Clinical Orthopaedics and Related Research ®

A Publication of The Association of Bone and Joint Surgeons ®

Symposium: Papers Presented at the Annual Meetings of The Knee Society 149 articles


Does Patellectomy Jeopardize Function After TKA?

Reina Yao MD, Matthew C. Lyons MD, James L. Howard MD, MSc, FRCSC, James P. McAuley MD, FRCSC

The patella provides important mechanical leverage to the knee extensor mechanism. Patellectomy does not exclude the development of tibiofemoral arthrosis.

The 2012 Chitranjan Ranawat Award: Intraarticular Analgesia After TKA Reduces Pain: A Randomized, Double-blinded, Placebo-controlled, Prospective Study

Nitin Goyal MD, James McKenzie BS, Peter F. Sharkey MD, Javad Parvizi MD, William J. Hozack MD, Matthew S. Austin MD

Postoperative pain after total knee arthroplasty remains one of the most important challenges facing patients undergoing this surgery. Providing a balance of adequate analgesia while limiting the functional impact of regional anesthesia and minimizing opioid side effects is critical to minimize adverse events and improve patient satisfaction.

Predictors of Range of Motion in Patients Undergoing Manipulation After TKA

Harpreet S. Bawa MD, Glenn D. Wera MD, Matthew J. Kraay MS, MD, Randall E. Marcus MD, Victor M. Goldberg MD

Knee stiffness or limited range of motion (ROM) after total knee arthroplasty (TKA) may compromise patient function. Patients with stiffness are usually managed with manipulation under anesthesia (MUA) to improve ROM. However, the final ROM obtained is multifactorial and may depend on factors such as comorbidities, implant type, or the timing of MUA.

Patient-specific Total Knee Arthroplasty Required Frequent Surgeon-directed Changes

Benjamin M. Stronach MD, Christopher E. Pelt MD, Jill Erickson PA, Christopher L. Peters MD

Patient-specific instrumentation potentially improves surgical precision and decreases operative time in total knee arthroplasty (TKA) but there is little supporting data to confirm this presumption.

Do Fresh Osteochondral Allografts Successfully Treat Femoral Condyle Lesions?

Yadin D. Levy MD, Simon Görtz MD, Pamela A. Pulido BSN, Julie C. McCauley MPHc, William D. Bugbee MD

Fresh osteochondral allograft transplantation is an increasingly common treatment option for chondral and osteochondral lesions in the knee, but the long-term outcome is unknown.

Postoperative Alignment and ROM Affect Patient Satisfaction After TKA

Shuichi Matsuda MD, Shinya Kawahara MD, Ken Okazaki MD, Yasutaka Tashiro MD, Yukihide Iwamoto MD

Patient satisfaction has increasingly been recognized as an important measure after total knee arthroplasty (TKA). However, we do not know yet how and why the patients are satisfied or dissatisfied with TKA.

Surgical Technique: Vastus Medialis and Vastus Lateralis as Flap Transfer for Knee Extensor Mechanism Deficiency

Leo A. Whiteside MD

Loss of the quadriceps tendon, patella, and patellar tendon leaves a major anterior defect that is difficult to close and compromises knee extension strength. Gastrocnemius muscle transfer does not sufficiently cover such major defects. This paper describes a new surgical technique that addresses these defects and the results of eight cases of revision TKA managed with this new technique.

Rotating-platform Has No Surface Damage Advantage Over Fixed-bearing TKA

Kirsten Stoner MEng, Seth A. Jerabek MD, Stephanie Tow BA, Timothy M. Wright PhD, Douglas E. Padgett MD

Rotating-platform TKA, although purported to have superior kinematics, has shown no clinical advantages over those of fixed-bearing TKA. Our design-matched retrieval study aimed to investigate if differences in bearing wear damage exist between fixed- and mobile-bearing TKAs with similar condylar geometry.

Computer-assisted Total Knee Arthroplasty Is Currently of No Proven Clinical Benefit: A Systematic Review

R. Stephen J. Burnett MD, FRCSCC, Robert L. Barrack MD

Navigated total knee arthroplasty (TKA) may improve coronal alignment outliers; however, it is unclear whether navigated TKA improves the long-term clinical results of TKA.

Does Interlimb Knee Symmetry Exist After Unicompartmental Knee Arthroplasty?

Yang-Chieh Fu PhD, Kathy J. Simpson PhD, Tracy L. Kinsey MSPH, Ormonde M. Mahoney MD

Unicompartmental knee arthroplasty (UKA) has long been a treatment option for patients with disease limited primarily to one compartment with small, correctable deformities. However, some surgeons presume that normal kinematics of a lateral compartment UKA are difficult to achieve. Furthermore, it is unclear whether UKA restores normal knee kinematics and interlimb symmetry.

Total Knee Arthroplasty With a Computer-navigated Saw: A Pilot Study

Kevin L. Garvin MD, Andres Barrera MS, Craig R. Mahoney MD, Curtis W. Hartman MD, Hani Haider PhD

Computer-aided surgery aims to improve implant alignment in TKA but has only been adopted by a minority for routine use. A novel approach, navigated freehand bone cutting (NFC), is intended to achieve wider acceptance by eliminating the need for cumbersome, implant-specific mechanical jigs and avoiding the expense of navigation.

Which Factors Increase Risk of Malalignment of the Hip-Knee-Ankle Axis in TKA?

Arun B. Mullaji FRCS(Ed), MCh(Orth), MS(Orth), Gautam M. Shetty MS(Orth), A. P. Lingaraju MS(Orth), Sagar Bhayde MS(Orth)

Computer navigation has improved accuracy and reduced the percentage of alignment outliers in TKA. However, the characteristics of outliers and the risk factors for limb malalignment after TKA are still unclear.

Long-term Survivorship and Failure Modes of Unicompartmental Knee Arthroplasty

Jared R. H. Foran MD, Nicholas M. Brown MD, Craig J. Della Valle MD, Richard A. Berger MD, Jorge O. Galante MD

In a previously reported series of 51 patients with 62 cemented, fixed-bearing unicompartmental knee arthroplasties, we reported a 10-year, 98% survival rate with an average knee score of 92 points. The survivorship and modes of failure past 10 years are incompletely understood.

Can Microcomputed Tomography Measure Retrieved Polyethylene Wear? Comparing Fixed-bearing and Rotating-platform Knees

Charles A. Engh MD, Rebecca L. Zimmerman MS, Robert H. Hopper PhD, Gerard A. Engh MD

Wear of total knee polyethylene has been quantified gravimetrically with thickness measurements and evaluation of surface wear modes. However, these techniques do not localize volumetric wear.

Determinants of Direct Medical Costs in Primary and Revision Total Knee Arthroplasty

Hilal Maradit Kremers MD, MSc, Sue L. Visscher PhD, James P. Moriarty MSc, Megan S. Reinalda, Walter K. Kremers PhD, James M. Naessens ScD, David G. Lewallen MD

TKA procedures are increasing rapidly, with substantial cost implications. Determining cost drivers in TKA is essential for care improvement and informing future payment models.

The ACL in the Arthritic Knee: How Often Is It Present and Can Preoperative Tests Predict Its Presence?

Aaron J. Johnson MD, Stephen M. Howell MD, Christopher R. Costa MD, Michael A. Mont MD

TKA with retention of the anterior cruciate ligament (ACL) may improve kinematics and function. However, conflicting reports exist concerning the prevalence of intact ACLs at the time of TKA.

Arthroplasty Knee Surgery and Alcohol Use: Risk Factor or Benefit?

Carlos J. Lavernia MD, Jesus M. Villa MD, Juan S. Contreras MD

Excessive alcohol consumption has been associated with adverse measures of health after elective surgery. However, associations of low/moderate consumption remain uncertain.

Complications of Total Knee Arthroplasty: Standardized List and Definitions of The Knee Society

William L. Healy MD, Craig J. Della Valle MD, Richard Iorio MD, Keith R. Berend MD, Fred D. Cushner MD, David F. Dalury MD, Jess H. Lonner MD

Despite the importance of complications in evaluating patient outcomes after TKA, definitions of TKA complications are not standardized. Different investigators report different complications with different definitions when reporting outcomes of TKA.

Low Risk of Thromboembolic Complications With Tranexamic Acid After Primary Total Hip and Knee Arthroplasty

Blake P. Gillette MD, Lori J. DeSimone PA, Robert T. Trousdale MD, Mark W. Pagnano MD, Rafael J. Sierra MD

The use of antifibrinolytic medications in hip and knee arthroplasty reduces intraoperative blood loss and decreases transfusion rates postoperatively. Tranexamic acid (TXA) specifically has not been associated with increased thromboembolic (TE) complications, but concerns remain about the risk of symptomatic TE events, particularly when less aggressive chemical prophylaxis methods such as aspirin alone are chosen.

The John Insall Award: No Benefit of Minimally Invasive TKA on Gait and Strength Outcomes: A Randomized Controlled Trial

Julien Wegrzyn MD, PhD, Sebastien Parratte MD, PhD, Krista Coleman-Wood PhD, PT, Kenton R. Kaufman PhD, PE, Mark W. Pagnano MD

While some clinical reports suggest minimally invasive surgical (MIS) techniques improve recovery and reduce pain in the first months after TKA, it is unclear whether it improves gait and thigh muscle strength.

Discordance in TKA Expectations Between Patients and Surgeons

Hassan M. K. Ghomrawi PhD, MPH, Carol A. Mancuso MD, Geoffrey H. Westrich MD, Robert G. Marx MD, MSc, Alvin I. Mushlin MD, ScM

Aligning patient and surgeon expectations preoperatively may lead to better postoperative medical and rehabilitation compliance and therefore improve outcomes and increase satisfaction.

High Infection Control Rate and Function After Routine One-stage Exchange for Chronically Infected TKA

Jean-Yves Jenny MD, Bruno Barbe MD, Jeannot Gaudias MD, Cyril Boeri MD, Jean-Noël Argenson MD

Many surgeons consider two-stage exchange the gold standard for treating chronic infection after TKA. One-stage exchange is an alternative for infection control and might provide better knee function, but the rates of infection control and levels of function are unclear.

Higher Cefazolin Concentrations with Intraosseous Regional Prophylaxis in TKA

Simon W. Young FRACS, Mei Zhang PhD, Joshua T. Freeman FRCPA, Kelly G. Vince MD, Brendan Coleman FRACS

Prophylactic antibiotics reduce the risk of deep infection after primary TKA. However, conventional systemic dosing may not provide adequate tissue concentrations against more resistant organisms such as coagulase-negative staphylococci. Regional intravenous administration of antibiotics after tourniquet inflation achieves far higher tissue concentrations but requires foot vein cannulation. The intraosseous route may offer a rapid and reliable method of regional administration.

Aseptic Tibial Debonding as a Cause of Early Failure in a Modern Total Knee Arthroplasty Design

Diren Arsoy MD, Mark W. Pagnano MD, David G. Lewallen MD, Arlen D. Hanssen MD, Rafael J. Sierra MD

We observed isolated tibial component debonding from the cement in one modern primary TKA design (NexGen LPS 3° tibial tray; Zimmer, Warsaw, IN, USA). This failure mechanism is sparsely reported in the literature.

Is Pain and Dissatisfaction After TKA Related to Early-grade Preoperative Osteoarthritis?

Gregory G. Polkowski MD, Erin L. Ruh MS, Toby N. Barrack, Ryan M. Nunley MD, Robert L. Barrack MD

There is growing evidence to suggest many patients experience pain and dissatisfaction after TKA. The relationship between preoperative osteoarthritis (OA) severity and postoperative pain and dissatisfaction after TKA has not been established.

Voriconazole Is Delivered From Antifungal-Loaded Bone Cement

Ryan B. Miller MD, Alex C. McLaren MD, Christine Pauken PhD, Henry D. Clarke MD, Ryan McLemore PhD

Local delivery of antifungals is an important modality in managing orthopaedic fungal infection. Voriconazole is a powder antifungal suitable for addition to bone cement that is released from bone cement but the mechanical properties of antimicrobial-loaded bone cement (ALBC) made with voriconazole are unknown.

Robotic-assisted TKA Reduces Postoperative Alignment Outliers and Improves Gap Balance Compared to Conventional TKA

Eun-Kyoo Song MD, PhD, Jong-Keun Seon MD, PhD, Ji-Hyeon Yim MD, PhD, Nathan A. Netravali PhD, William L. Bargar MD

Several studies have shown mechanical alignment influences the outcome of TKA. Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment.

Durability of a Cruciate-retaining TKA With Modular Tibial Trays at 20 Years

John J. Callaghan MD, Mitchell W. Beckert BS, David W. Hennessy MD, Devon D. Goetz MD, Scott S. Kelley MD

Modular tibial trays have been utilized in TKA for more than 20 years. However, concerns have been raised about modular implants and it is unclear whether these devices are durable in the long term.

The 2012 Mark Coventry Award: A Retrieval Analysis of High Flexion versus Posterior-stabilized Tibial Inserts

Nicholas R. Paterson BScH, Matthew G. Teeter BScH, PhD, Steven J. MacDonald MD, FRCSC, Richard W. McCalden MD, MPhil(Edin), FRCSC, Douglas D. R. Naudie MD, FRCSC

High flexion (HF) implants were introduced to increase ROM and patient satisfaction, but design changes to the implant potentially have deleterious effects on polyethylene wear. It is unclear whether the HF implants affect wear.

Failure of Irrigation and Débridement for Early Postoperative Periprosthetic Infection

Thomas K. Fehring MD, Susan M. Odum MEd, Keith R. Berend MD, William A. Jiranek MD, Javad Parvizi MD, Kevin J. Bozic MD, Craig J. Della Valle MD, Terence J. Gioe MD

Irrigation and débridement (I&D) of periprosthetic infection (PPI) is associated with infection control ranging from 16% to 47%. Mitigating factors include organism type, host factors, and timing of intervention. While the influence of organism type and host factors has been clarified, the timing of intervention remains unclear.

Is Administratively Coded Comorbidity and Complication Data in Total Joint Arthroplasty Valid?

Kevin J. Bozic MD, MBA, Ravi K. Bashyal MD, Shawn G. Anthony MD, MBA, Vanessa Chiu MPH, Brandon Shulman BS, Harry E. Rubash MD

Administrative claims data are increasingly being used in public reporting of provider performance and health services research. However, the concordance between administrative claims data and the clinical record in lower extremity total joint arthroplasty (TJA) is unknown.

Development of a New Knee Society Scoring System

Philip C. Noble PhD, Giles R. Scuderi MD, Adam C. Brekke BA, Alla Sikorskii PhD, James B. Benjamin MD, Jess H. Lonner MD, Priya Chadha MD, Daniel A. Daylamani BS, W. Norman Scott MD, Robert B. Bourne MD, FRCSC

The Knee Society Clinical Rating System was developed in 1989 and has been widely adopted. However, with the increased demand for TKA, there is a need for a new, validated scoring system to better characterize the expectations, satisfaction, and physical activities of the younger, more diverse population of TKA patients.

How Does TKA Kinematics Vary With Transverse Plane Alignment Changes in a Contemporary Implant?

William M. Mihalko MD, PhD, Devin J. Conner BS, Rodney Benner MD, John L. Williams PhD

Assessment of patient function after TKA often focuses on implant alignment and daily activity capabilities, but the functional results and kinematics of the TKA are not easily predicted by some of these parameters during surgery.

Unicompartmental Versus Total Knee Arthroplasty Database Analysis: Is There a Winner?

Matthew C. Lyons MBBS, FRACS, Steven J. MacDonald MD, FRCSC, Lyndsay E. Somerville MSc, Douglas D. Naudie MD, FRCSC, Richard W. McCalden MD, FRCSC

TKA and unicompartmental knee arthroplasty (UKA) are both utilized to treat unicompartmental knee arthrosis. While some surgeons assume UKA provides better function than TKA, this assumption is based on greater final outcome scores rather than on change in scores and many patients with UKA have higher preoperative scores.

The New Knee Society Knee Scoring System

Giles R. Scuderi MD, Robert B. Bourne MD, FRCSC, Philip C. Noble MD, James B. Benjamin MD, Jess H. Lonner MD, W. N. Scott MD

All-polyethylene and Metal-backed Tibial Components Are Equivalent With BMI of Less Than 37.5

Jared Toman MD, Richard Iorio MD, William L. Healy MD

Modular, metal-backed tibial (MBT) components are associated with locking mechanism dysfunction, breakage, backside wear, and osteolysis, which compromise survivorship. All-polyethylene tibial (APT) components eliminate problems associated with MBTs, but, historically, APT utilization has generally been limited to older, less active patients. However, it is unclear whether APT utilization can be expanded to a nonselected patient population.

Pain Relief and Functional Improvement Remain 20 Years After Knee Arthroplasty

John B. Meding MD, Lindsey K. Meding, Merrill A. Ritter MD, E. Michael Keating MD

TKA provides demonstrable pain relief and improved health-related quality of life. Yet, a decline in physical function may occur over the long term despite the absence of implant-related problems.

Does a Modified Gap-balancing Technique Result in Medial-pivot Knee Kinematics in Cruciate-retaining Total Knee Arthroplasty?: A Pilot Study

Wolfgang Fitz MD, Sonal Sodha, William Reichmann, Tom Minas MD, MS

Normal knee kinematics is characterized by posterior femorotibial rollback with tibial internal rotation and medial-pivot rotation in flexion. Cruciate-retaining TKAs (CR-TKAs) do not reproduce normal knee kinematics.

The John Insall Award: No Functional Advantage of a Mobile Bearing Posterior Stabilized TKA

Ormonde M. Mahoney MD, Tracy L. Kinsey MSPH, Theresa J. D’Errico MSHS, Jianhua Shen MS

Mobile bearing (MB) total knee design has been advocated as a means to enhance the functional characteristics and decrease the wear rates of condylar total knee arthroplasty (TKA). However, it is unclear if these designs achieve these goals.

Perioperative Closure-related Complication Rates and Cost Analysis of Barbed Suture for Closure in TKA

Jeremy M. Gililland MD, Lucas A. Anderson MD, Grant Sun BS, Jill A. Erickson PA-C, Christopher L. Peters MD

The use of barbed suture for surgical closure has been associated with lower operative times, equivalent wound complication rate, and comparable cosmesis scores in the plastic surgery literature. Similar studies would help determine whether this technology is associated with low complication rates and reduced operating times for orthopaedic closures.

Can a High-flexion Total Knee Arthroplasty Relieve Pain and Restore Function Without Premature Failure?

Ryan D. Bauman MD, Derek R. Johnson MD, Travis J. Menge MD, Raymond H. Kim MD, Douglas A. Dennis MD

High-flexion TKA prostheses are designed to improve flexion and clinical outcomes. Increased knee flexion can increase implant loads and fixation stresses, creating concerns of premature failure. Whether these goals can be achieved without premature failures is unclear.

Minimizing Dynamic Knee Spacer Complications in Infected Revision Arthroplasty

Aaron J. Johnson MD, Siraj A. Sayeed MD, Qais Naziri MD, Harpal S. Khanuja MD, Michael A. Mont MD

Deep infections are devastating complications of TKA often treated with component explantation, intravenous antibiotics, and antibiotic-impregnated cement spacers. Historically, the spacers have been static, which may limit patients’ ROM and ability to walk. Several recent reports describe dynamic spacers, which may allow for improved ROM and make later reimplantation easier. However, because of several dynamic spacer problems noted at our institution, we wanted to assess their associated failures, reinfection rates, and functionality.

Three-dimensional Morphology of the Knee Reveals Ethnic Differences

Mohamed Mahfouz PhD, Emam ElHak Abdel Fatah Bsc, Lyndsay Smith Bowers MSc, Giles Scuderi MD

Studies have demonstrated sex differences in femoral shape and quadriceps angle raising a question of whether implant design should be sex-specific. Much of this research has addressed shape differences within the Caucasian population and little is known about differences among ethnic groups.

Reinfected Revised TKA Resolves With an Aggressive Protocol and Antibiotic Infusion

Leo A. Whiteside MD, Tariq A. Nayfeh MD, PhD, Renee LaZear RN, Marcel E. Roy PhD

Revision of failed two-stage revision TKA for infection is challenging, and amputation often is the only alternative.

Patient-related Risk Factors for Postoperative Mortality and Periprosthetic Joint Infection in Medicare Patients Undergoing TKA

Kevin J. Bozic MD, MBA, Edmund Lau MS, Steven Kurtz PhD, Kevin Ong PhD, Daniel J. Berry MD

The impact of specific baseline comorbid conditions on the relative risk of postoperative mortality and periprosthetic joint infection (PJI) in elderly patients undergoing TKA has not been well defined.

Is There a Preferred Articulating Spacer Technique for Infected Knee Arthroplasty?: A Preliminary Study

Niraj V. Kalore MD, Aditya Maheshwari MD, Amit Sharma MD, Edward Cheng MD, Terence J. Gioe MD

Periprosthetic infection in TKA is a devastating and challenging problem for both patients and surgeons. Two-stage exchange arthroplasty with an interval antibiotic spacer reportedly has the highest infection control rate. Studies comparing static spacers with articulating spacers have reported varying ROM after reimplant, which could be due to differences in articulating spacer technique.

Revision Surgery for Patellofemoral Problems: Should We Always Resurface?

Todd C. Johnson MD, Penny J. Tatman MPH, Susan Mehle BS, Terence J. Gioe MD

Routine patellar resurfacing performed at the time of knee arthroplasty is controversial, with some evidence of utility in both TKA (tricompartmental) and bicompartmental knee arthroplasty. However, whether one approach results in better implant survival remains unclear.

Can Surgeons Predict What Makes a Good TKA?: Intraoperative Surgeon Impression of TKA Quality Does Not Correlate With Knee Society Scores

Gwo-Chin Lee MD, Paul A. Lotke MD

Surgeons generally agree on what they want to achieve when performing TKA. However, we do not know which technical quality goals are correct, important, or irrelevant to achieve adequate function or durability.

Lateral Unicompartmental Knee Arthroplasty Through a Lateral Parapatellar Approach Has High Early Survivorship

Keith R. Berend MD, Michael C. Kolczun MD, Joseph W. George MD, Adolph V. Lombardi MD

The literature suggests lateral unicompartmental knee arthroplasties are associated with low revision rates. However, there are fewer reports describing techniques for lateral unicompartmental arthroplasty and whether technique influences ROM and function compared to reports for medial unicompartmental arthroplasty.

Polyethylene Quality Affects Revision Knee Liner Exchange Survivorship

C. Anderson Engh MD, Nancy L. Parks MS, Gerard A. Engh MD

Options to treat patients with wear or osteolysis include full revision, partial (tibial or femoral) revision, and isolated polyethylene exchange. It is unclear whether one choice is superior to the other. Polyethylene quality reportedly influences the survivorship of primary TKA, but similar reports are not described for revision TKA.

Improved Accuracy of Alignment With Patient-specific Positioning Guides Compared With Manual Instrumentation in TKA

Vincent Y. Ng MD, Jeffrey H. DeClaire MD, Keith R. Berend MD, Bethany C. Gulick RT (R), Adolph V. Lombardi MD

Coronal malalignment occurs frequently in TKA and may affect implant durability and knee function. Designed to improve alignment accuracy and precision, the patient-specific positioning guide is predicated on restoration of the overall mechanical axis and is a multifaceted new tool in achieving traditional goals of TKA.

Restoration of the Distal Femur Impacts Patellar Height in Revision TKA

Saurabh Khakharia MD, Giles R. Scuderi MD

Restoring patellar height is important in revision TKA for normal knee function and kinematics. Alteration in patellar height after revision TKA is associated with inferior extensor mechanism function.

Mark B. Coventry Award: Synovial C-reactive Protein: A Prospective Evaluation of a Molecular Marker for Periprosthetic Knee Joint Infection

Javad Parvizi MD, FRCS, Christina Jacovides BS, Bahar Adeli BA, Kwang Am Jung MD, William J. Hozack MD

C-reactive protein (CRP) serum assays are a standard element of the diagnostic workup for periprosthetic joint infection (PJI). However, because CRP is a marker for systemic inflammation, this test is not specific to PJI.

Platelet-rich Plasma Does Not Reduce Blood Loss or Pain or Improve Range of Motion After TKA

Timothy M. DiIorio MD, Justin D. Burkholder BS, Robert P. Good MD, Javad Parvizi MD, Peter F. Sharkey MD

Numerous reports suggest the application of platelet-rich plasma (PRP) during TKA may decrease postoperative bleeding. Because excessive bleeding can increase postoperative pain and inflammation, use of PRP also reportedly decreases the need for narcotics and increases speed of recovery after TKA. Because previous investigations of PRP and TKA reflect a weak level of medical evidence, we sought to confirm these findings.

All-Polyethylene Tibial Components in Obese Patients Are Associated With Low Failure at Midterm Followup

David F. Dalury MD, Kimberly K. Tucker MD, Todd C. Kelley MD

In the United States, the obese population has increased markedly over the last four decades, and this trend continues. High patient weight places additional stress on TKA components, which may lead to increased polyethylene wear, osteolysis, radiolucencies, and clinical failure. Metal-backed tibial components and all-polyethylene tibial components in the general population have comparable osteolysis and failure, but it is unclear whether these components yield similar osteolysis and failure in obese patients.

Lateral Unicompartmental Knee Arthroplasty Relieves Pain and Improves Function in Posttraumatic Osteoarthritis

Sebastien Lustig MD, PhD, Sebastien Parratte MD, PhD, Robert A. Magnussen MD, Jean-Noel Argenson MD, Philippe Neyret MD

Posttraumatic arthritis secondary to lateral tibial plateau fracture malunion causes pain and limited function for patients. It is sometimes technically challenging to correct malalignment in these patients with advanced arthritis using osteotomies. Lateral unicompartmental knee arthroplasty (UKA) may be an option to treat such patients.

No Long-term Difference Between Fixed and Mobile Medial Unicompartmental Arthroplasty

Sebastien Parratte MD, Vanessa Pauly MS, Jean-Manuel Aubaniac MD, Jean-Noel A. Argenson MD

Early studies in the literature reported relatively high early minor reintervention rate for the mobile-bearing unilateral knee arthroplasty (UKA) compared with short- and midterm survivorship after fixed- or mobile-bearing UKA. However, whether the long-term function and survivorship are similar is unclear.

Decreased Length of Stay After TKA Is Not Associated With Increased Readmission Rates in a National Medicare Sample

John S. Vorhies BA, Yun Wang PhD, James H. Herndon MD, MBA, William J. Maloney MD, James I. Huddleston MD

There is a trend toward decreasing length of hospital stay (LOS) after TKA although it is unclear whether this trend is detrimental to the overall postoperative course. Such information is important for future decisions related to cost containment.

Preoperative Patient Education Reduces In-hospital Falls After Total Knee Arthroplasty

Henry D. Clarke MD, Vickie L. Timm BSN, Brynn R. Goldberg MSN, Steven J. Hattrup MD

Inpatient hospital falls after orthopaedic surgery represent a major problem, with rates of about one to three falls per 1000 patient days. These falls result in substantial morbidity for the patient and liability for the institution.

The Chitranjan Ranawat Award: Is Neutral Mechanical Alignment Normal for All Patients?: The Concept of Constitutional Varus

Johan Bellemans MD, PhD, William Colyn MD, Hilde Vandenneucker MD, Jan Victor MD, PhD

Most knee surgeons have believed during TKA neutral mechanical alignment should be restored. A number of patients may exist, however, for whom neutral mechanical alignment is abnormal. Patients with so-called “constitutional varus” knees have had varus alignment since they reached skeletal maturity. Restoring neutral alignment in these cases may in fact be abnormal and undesirable and would likely require some degree of medial soft tissue release to achieve neutral alignment.

Can Tantalum Cones Provide Fixation in Complex Revision Knee Arthroplasty?

Paul F. Lachiewicz MD, Michael P. Bolognesi MD, Robert A. Henderson MSc, Elizabeth S. Soileau BSN, Thomas Parker Vail MD

The best method for managing large bone defects during revision knee arthroplasty is unknown. Metaphyseal fixation using porous tantalum cones has been proposed for severe bone loss. Whether this approach achieves osseointegration with low complication rates is unclear.

Continuous Infusion of UHMWPE Particles Induces Increased Bone Macrophages and Osteolysis

Pei-Gen Ren DVM, PhD, Afraaz Irani BS, Zhinong Huang MD, PhD, Ting Ma MD, MSc, Sandip Biswal MD, Stuart B. Goodman MD, PhD

Aseptic loosening and periprosthetic osteolysis resulting from wear debris are major complications of total joint arthroplasty. Monocyte/macrophages are the key cells related to osteolysis at the bone-implant interface of joint arthroplasties. Whether the monocyte/macrophages found at the implant interface in the presence of polyethylene particles are locally or systemically derived is unknown.

Incidence and Reasons for Nonrevision Reoperation After Total Knee Arthroplasty

Benjamin Zmistowski BS, Camilo Restrepo MD, Lauren K. Kahl BS, Javad Parvizi MD, FRCS, Peter F. Sharkey MD

A dramatic increase in the demand for TKA is expected. The current burden of revision TKA is well known but the incidence and etiology of nonrevision reoperations after primary TKA is not.

Wear Damage in Mobile-bearing TKA is as Severe as That in Fixed-bearing TKA

Natalie H. Kelly BS, Rose H. Fu BS, Timothy M. Wright PhD, Douglas E. Padgett MD

Mobile-bearing TKAs reportedly have no clinical superiority over fixed-bearing TKAs, but a potential benefit is improved polyethylene wear behavior.

Popliteus Tendon Resection During Total Knee Arthroplasty: An Observational Report

Thomas J. Kesman MD, MBA, Kenton R. Kaufman PhD, Robert T. Trousdale MD

The contribution provided by the popliteus tendon in patients undergoing TKA is poorly defined. Some authors believe the popliteus tendon is essential to a well-functioning arthroplasty, while others do not believe it provides a critical function.

Liner Exchange and Bone Grafting: Rare Option to Treat Wear & Lysis of Stable TKAs

John J. Callaghan MD, Eric R. Reynolds, Nicholas T. Ting BA, Devon D. Goetz MD, John C. Clohisy MD, William J. Maloney MD

Liner exchange and bone grafting are commonly performed for wear and osteolysis around well-fixed modular acetabular components that otherwise would require structural allografting and revision THA. However, liner exchange in the face of substantial lysis around TKA has been performed rarely with reports of failure rates of up to 25% at 3 year followup.

In Vivo Normal Knee Kinematics: Is Ethnicity or Gender an Influencing Factor?

Filip Leszko MSc, Kristen R. Hovinga MS, Amy L. Lerner PhD, Richard D. Komistek PhD, Mohamed R. Mahfouz PhD

In vivo studies have suggested Caucasians achieve lower average knee flexion than non-Western populations. Some previous studies have also suggested gender may influence condylar AP translation and axial rotation, while others report an absence of such an influence.

Technical Challenges of Total Knee Arthroplasty in Skeletal Dysplasia

Raymond H. Kim MD, Giles R. Scuderi MD, Douglas A. Dennis MD, Steven W. Nakano BA

Total knee arthroplasty (TKA) in patients with skeletal dysplasias is particularly challenging as a result of the anatomic variances and substantial bony deformities. Little has been written regarding technical considerations that should be made when performing TKA in skeletal dysplasia.

Implant Design Influences Tibial Post Wear Damage in Posterior-stabilized Knees

Mark M. Dolan MD, Natalie H. Kelly BS, Joseph T. Nguyen MPH, Timothy M. Wright PhD, Steven B. Haas MD

The tibial post in posterior-stabilized total knees is a potential source of polyethylene wear debris, but the relationship between the shape and location of the tibial post in relation to the tibiofemoral bearing surfaces and the subsequent wear damage patterns remains unknown.

Hematologic Genetic Testing in High-risk Patients Before Knee Arthroplasty: A Pilot Study

Hany Bedair MD, Martin Berli MD, Sefer Gezer MD, Joshua J. Jacobs MD, Craig J. Della Valle MD

Patients with a personal or familial history of thromboembolism are considered at higher risk for thromboembolic disease after knee arthroplasty. While it remains unclear why some patients develop deep vein thrombosis (DVT) or pulmonary embolism (PE) despite similar operative procedures and the same prophylactic regimen, we presume one explanation would be genetic predisposition.

When Can I Drive?: Brake Response Times After Contemporary Total Knee Arthroplasty

David F. Dalury MD, Kimberly K. Tucker MD, Todd C. Kelley MD

After right total knee arthroplasty (TKA), patients are usually eager to return to driving. Previous studies suggest 6 weeks postsurgery is a safe time. However, recent advances in surgical technique, pain management, and rehabilitation have theoretically improved recovery after TKA.

A Second Decade Lifetable Survival Analysis of the Oxford Unicompartmental Knee Arthroplasty

Andrew J. Price DPhil FRCS(Orth), Ulf Svard MD

The role of unicompartmental arthroplasty in managing osteoarthritis of the knee remains controversial. The Oxford medial unicompartmental arthroplasty employs a fully congruent mobile bearing intended to reduce wear and increase the lifespan of the implant. Long-term second decade results are required to establish if the design aim can be met.

Management of Intraoperative Medial Collateral Ligament Injury During TKA

Gwo-Chin Lee MD, Paul A. Lotke MD

Intraoperative injuries to the medial collateral ligament are often unrecognized and failure to appropriately manage ligament loss may result in knee instability and loosening.

Knee Arthroplasty With a Medially Conforming Ball-and-Socket Tibiofemoral Articulation Provides Better Function

Fahad Hossain MRCS, Shelain Patel MRCS, Shin-Jae Rhee MRCS, Fares Sami Haddad FRCS (Tr & Orth)

A knee design with a ball-and-socket articulation of the medial compartment has a femoral rollback profile similar to the native knee. Compared to a conventional, posterior-stabilized knee design, it provides AP stability throughout the entire ROM. However, it is unclear whether this design difference translates to clinical and functional improvement.

Perioperative Complications of Simultaneous versus Staged Unicompartmental Knee Arthroplasty

Keith R. Berend MD, Michael J. Morris MD, Michael D. Skeels DO, Adolph V. Lombardi MD, FACS, Joanne B. Adams BFA

The complication risk of staged versus simultaneous total knee arthroplasty continues to be debated in the literature. Previous reports suggest unicompartmental knee arthroplasty provides a more rapid functional recovery than total knee arthroplasty. However, little data exist on whether simultaneous unicompartmental knee arthroplasty can be performed without increasing the perioperative risk compared with staged unicompartmental knee arthroplasty.

In Vitro Quantification of Wear in Tibial Inserts Using Microcomputed Tomography

Matthew G. Teeter BSc, Douglas D. R. Naudie MD, FRCSC, David D. McErlain MSc, Jan-M. Brandt Dipl-Ing, PhD, Xunhua Yuan PhD, Steven J. MacDonald MD, FRCSC, David W. Holdsworth PhD

Wear of polyethylene tibial inserts can decrease the longevity of total knee arthroplasty. Wear is currently assessed using laboratory methods that may not permit backside wear measurements or do not quantify surface deviation.

Hospital Economics of Primary Total Knee Arthroplasty at a Teaching Hospital

William L. Healy MD, Adam J. Rana MD, Richard Iorio MD

The hospital cost of total knee arthroplasty (TKA) in the United States is a major growing expense for the Centers for Medicare & Medicaid Services (CMS). Many hospitals are unable to deliver TKA with profitable or breakeven economics under the current Diagnosis-Related Group (DRG) hospital reimbursement system.

The John Insall Award: Control-matched Evaluation of Painful Patellar Crepitus After Total Knee Arthroplasty

Douglas A. Dennis MD, Raymond H. Kim MD, Derek R. Johnson MD, Bryan D. Springer MD, Thomas K. Fehring MD, Adrija Sharma PhD

Patellar crepitus (PC) is reported in up to 14% of subjects implanted with cruciate-substituting total knee arthroplasty (TKA). Numerous etiologies of PC have been proposed.

Do “Premium” Joint Implants Add Value?: Analysis of High Cost Joint Implants in a Community Registry

Terence J. Gioe MD, Amit Sharma MD, Penny Tatman MPH, Susan Mehle BS

Numerous joint implant options of varying cost are available to the surgeon, but it is unclear whether more costly implants add value in terms of function or longevity.

The Chitranjan Ranawat Award: Fate of Two-stage Reimplantation After Failed Irrigation and Débridement for Periprosthetic Knee Infection

J. Christopher Sherrell MD, Thomas K. Fehring MD, Susan Odum MEd, Erik Hansen MD, Benjamin Zmistowski BS, Anne Dennos BS, Niraj Kalore MD

Irrigation and débridement is an attractive low morbidity solution for acute periprosthetic knee infection. However, the failure rate in the literature is high, averaging 68% (range, 61%–82%). Patients who fail subsequently undergo two-stage reimplantation after a prolonged period of illness. This leads to higher surgical risk and further delays in rehabilitation and may contribute to failure of subsequent revision surgery.

The Mark Coventry Award: Diagnosis of Early Postoperative TKA Infection Using Synovial Fluid Analysis

Hany Bedair MD, Nicholas Ting BA, Christina Jacovides BA, Arjun Saxena MD, Mario Moric MS, Javad Parvizi MD, Craig J. Della Valle MD

Synovial fluid white blood cell count is useful for diagnosing periprosthetic infections but the utility of this test in the early postoperative period remains unknown as hemarthrosis and postoperative inflammation may render standard cutoff values inaccurate.

The Peel in Total Knee Revision: Exposure in the Difficult Knee

Carlos Lavernia MD, Juan Salvador Contreras MD, Jose Carlos Alcerro MD

The femoral peel to expose a difficult knee was first described by Windsor and Insall in the mid-1980s. This surgical exposure consists of a complete soft tissue subperiosteal peel of the femur. It includes the detachment of the origin of the medial and lateral collateral ligaments.

Wear and Lysis is the Problem in Modular TKA in the Young OA Patient at 10 Years

Andrew N. Odland BS, John J. Callaghan MD, Steve S. Liu MD, Christopher W. Wells BA

Most long-term followup studies of younger patients who underwent TKA include a relatively high percentage of rheumatoid patients, whose function and implant durability may differ from those with osteoarthritis (OA).

Methicillin-resistant Staphylococcus aureus in TKA Treated With Revision and Direct Intraarticular Antibiotic Infusion

Leo A. Whiteside MD, Michael Peppers PharmD, Tariq A. Nayfeh MD, PhD, Marcel E. Roy PhD

Resistant organisms are difficult to eradicate in infected total knee arthroplasty. While most surgeons use antibiotic-impregnated cement in these revisions, the delivery of the drug in adequate doses is limited in penetration and duration. Direct infusion is an alternate technique.

Discontinuation of Warfarin Is Unnecessary in Total Knee Arthroplasty

David A. Rhodes MD, Erik P. Severson MD, Jeffrey T. Hodrick MD, Harold K. Dunn MD, Aaron A. Hofmann MD Patients with medical comorbidities that necessitate chronic anticoagulation therapy frequently present as candidates for total knee arthroplasty (TKA). We asked whether it was necessary to stop warfarin preoperatively to avoid postoperative bleeding complications. We retrospectively reviewed 77 preoperatively anticoagulated patients undergoing TKA. Thirty-eight of these 77 patients were maintained on their routine therapeutic warfarin regimen throughout the perioperative period. The remaining 39 patients had their routine preoperative warfarin regimen discontinued preoperatively and then restarted after surgery. We compared rates of comorbid illness, blood transfusions, wound complications, and reoperations. The demographic data and the ratio of primary to revision arthroplasties were similar in the two groups. The age-adjusted risk ratios for blood transfusions, wound complications, and reoperations were 0.61, 0.29, and 0.43, respectively. The data presented suggest maintaining a therapeutic warfarin regimen throughout the perioperative period for high-risk patients is not associated with an increase risk of complications after TKA.,[object Object]

The Role of Polyethylene Design on Postoperative TKA Flexion: An Analysis of 1534 Cases

Richard W. McCalden MD, MPhil (Edin), FRCSC, Steven J. MacDonald MD, FRCSC, Kory D. J. Charron MET, Robert B. Bourne MD, FRCSC, Douglas D. Naudie MD, FRCSC The range of motion after TKA depends on many patient, surgical technique, and implant factors. Recently, high-flexion designs have been introduced as a means of ensuring or gaining flexion after TKA. We therefore evaluated factors affecting postoperative flexion to determine whether implant design influences longterm flexion. We prospectively collected data on patients receiving a primary Genesis II™ total knee replacement with a minimum of 1-year followup (mean, 5.4 years; range, 1–13 years). We recorded pre- and postoperative outcome measures, patient demographics, and implant design (cruciate retaining [CR, n = 160], posterior stabilized [PS, n = 1177], high-flex posterior stabilized [HF-PS, n = 197]). Backward stepwise linear regression modeling identified the following factors affecting postoperative flexion: preoperative flexion, gender, body mass index, and implant design. Independent of gender, body mass index, and preoperative flexion, patients who received a HF-PS and PS design implant had a mean of 8° and 5° more flexion, respectively, than those who received a CR implant. Patients with low flexion preoperatively (< 100°) were more likely to gain flexion, whereas those with high flexion preoperatively (> 120°) were most likely to maintain or lose flexion postoperatively. Controlling for implant design, patients with high flexion preoperatively (> 120°) were more likely to gain flexion with the HF-PS design implant (HF-PS = 32.0%; PS = 15.1%; CR = 4.5%).,[object Object]

Patient Satisfaction after Total Knee Arthroplasty: Who is Satisfied and Who is Not?

Robert B. Bourne MD, FRCSC, Bert M. Chesworth PhD, Aileen M. Davis PhD, Nizar N. Mahomed MD, MPH, FRCSC, Kory D. J. Charron Dipl. MET Despite substantial advances in primary TKA, numerous studies using historic TKA implants suggest only 82% to 89% of primary TKA patients are satisfied. We reexamined this issue to determine if contemporary TKA implants might be associated with improved patient satisfaction. We performed a cross-sectional study of patient satisfaction after 1703 primary TKAs performed in the province of Ontario. Our data confirmed that approximately one in five (19%) primary TKA patients were not satisfied with the outcome. Satisfaction with pain relief varied from 72–86% and with function from 70–84% for specific activities of daily living. The strongest predictors of patient dissatisfaction after primary TKA were expectations not met (10.7× greater risk), a low 1-year WOMAC (2.5× greater risk), preoperative pain at rest (2.4× greater risk) and a postoperative complication requiring hospital readmission (1.9× greater risk).,[object Object]

Gap Balancing versus Measured Resection Technique for Total Knee Arthroplasty

Douglas A. Dennis MD, Richard D. Komistek PhD, Raymond H. Kim MD, Adrija Sharma PhD Multiple differing surgical techniques are currently utilized to perform total knee arthroplasty (TKA). We compared knee arthroplasties performed using either a measured resection or gap balancing technique to determine if either operative technique provides superior coronal plane stability as measured by assessment of the incidence and magnitude of femoral condylar lift-off. We performed 40 TKA using a measured resection technique (20 PCL-retaining and 20 PCL-substituting) and 20 PCL-substituting TKA were implanted using gap balancing. All subjects were analyzed fluoroscopically while performing a deep knee bend. The incidence of coronal instability (femoral condylar lift-off) was then determined using a 3-D model fitting technique. The incidence of lift-off greater than 0.75 mm was 80% (maximum, 2.9 mm) and 70% (maximum, 2.5 mm) for the PCL-retaining and substituting TKA groups performed using measured resection versus 35% (maximum, 0.88 mm) for the gap-balanced group. Lift-off greater than 1 mm occurred in 60% and 45% of the PCL-retaining and -substituting TKA using measured resection versus none in the gap-balanced group. Rotation of the femoral component using a gap balancing technique resulted in better coronal stability which we suggest will improve functional performance and reduce polyethylene wear.

Revision Total Knee Arthroplasty for Aseptic and Septic Causes in Patients with Rheumatoid Arthritis

Ryan M. Garcia MD, Brian T. Hardy MD, MBA, Matthew J. Kraay MS, MD, Victor M. Goldberg MD Revision total knee arthroplasty in patients with rheumatoid arthritis can be challenging. We asked whether we could confirm previously reported high failure rates following revision total knee arthroplasty in patients with rheumatoid arthritis. We therefore determined the Knee Society knee score and function scores, radiographic evidence of failure, and overall survival of the revision procedure in these patients. We retrospectively reviewed 39 patients with rheumatoid arthritis who underwent 45 TKA revisions from 1994 to 2006. Twenty-seven of the 45 TKA revisions were for mechanical failure of the prosthetic components and 18 for infection. Five of the 27 knees (19%) revised for mechanical failure subsequently failed a second time. Five of the 18 patients who underwent revision for infection died within 6 months and three of the remaining knees failed secondary to reinfection. Excluding the knees that failed, the average Knee Society knee score and function score improved in both subgroups. Two knees had radiographic evidence of nonprogressive tibial radiolucencies. The probability of survival for all knees (revision as the end point) was 76% ± 9% at 5 years. We confirmed the previously reported high mortality and subsequent failure rates following revision total knee arthroplasty for both mechanical issues and infection in patients with rheumatoid arthritis and emphasize the potential difficulties in treating these patients.,[object Object]

2009 Knee Society Presidential Guest Lecture: Polyethylene Wear in Total Knees

John Fisher DEng, Louise M. Jennings PhD, Alison L. Galvin PhD, Zhongmin M. Jin PhD, Martin H. Stone FRCS, Eileen Ingham PhD Knee arthroplasties in young and active patients place a substantial increase in the lifetime tribological demand and potential for wear-induced osteolysis. Polyethylene materials have advanced in recent years, reducing the potential for oxidative degradation and delamination failure. It is timely to consider tribological design variables and their potential to reduce surface wear and the long-term risk of osteolysis. The influence of reduced cross shear in rotating platform mobile-bearing knee designs and reduced surface wear area in low conforming fixed-bearing knees has been investigated. A reduction in cross shear substantially reduced wear in both multidirectional pin-on-plate studies and in rotating platform mobile-bearing designs in knee simulator studies. A reduction in bearing surface contact area substantially reduced surface wear in multidirectional pin-on-plate simulations and in low conforming fixed-bearing knee designs in knee simulator studies. This offers potential for a paradigm shift in knee design predicated by enhanced mechanical properties of new polymer materials. We describe two distinct low-wearing tribological design solutions: (1) a rotating platform design solution with reduced cross shear provides reduced wear with conformity and intrinsic stability; and (2) a low conformity fixed bearing with reduced surface area, provides reduced wear, but has less intrinsic stability and requires good soft tissue function.

Complications of Femoral Nerve Block for Total Knee Arthroplasty

Sanjeev Sharma MD, FRCSC, Richard Iorio MD, Lawrence M. Specht MD, Sara Davies-Lepie MD, William L. Healy MD Preemptive and multimodal pain control protocols have been introduced to enhance rehabilitation after total knee arthroplasty (TKA). We determined the complication rate associated with preoperative femoral nerve block (FNB) for TKA. Among 1018 TKA operations, we performed 709 FNBs using a single-injection technique into the femoral nerve sheath and confirming position with nerve stimulation before induction. After TKA, weightbearing as tolerated was initiated using a walker or crutches on postoperative Day 1. Twelve patients (1.6%) treated with FNB sustained falls, three (0.4%) of whom underwent reoperations. Five patients had postoperative femoral neuritis, which may have been secondary to the block. One patient had new onset of atrial fibrillation after FNB, and the TKA was postponed. Femoral nerve block before TKA is not a harmless intervention. We recommend postoperative protocols be modified for patients who have FNB to account for decreased quadriceps function in the early postoperative period, which can lead to falls.,[object Object]

Isolated Tibial Polyethylene Insert Exchange Outcomes After Total Knee Arthroplasty

Seann E. Willson MD, Michelle L. Munro BS, Julie C. Sandwell MPHc, Kace A. Ezzet MD, Clifford W. Colwell MD Total knee arthroplasty (TKA) using a modular design allows isolated tibial polyethylene insert exchange (ITPIE) as a treatment option for isolated polyethylene failure. We asked whether ITPIE in selected patients would provide high survivorship and identified factors predicting success or failure. We retrospectively reviewed 42 patients (42 knees) who underwent ITPIE for instability, stiffness, or aseptic effusions after TKA. All patients had well-aligned and well-fixed components documented by radiographs and intraoperative evaluation. We determined whether patients had been revised and evaluated unrevised patients using the Knee Society rating system. The minimum followup was 2 years (average, 5.6 years; range, 2–11 years). Twelve patients (29%) underwent subsequent revision of their ITPIE (58% survivorship at 11 years). Average time to revision was 3 years. Although mean Knee Society scores improved, nine of the 30 unrevised patients (30%) had persistent pain at followup. Time from index TKA to ITPIE was associated with outcome; ITPIE less than 3 years from index TKA was 3.8 times more likely to undergo rerevision than ITPIE more than 3 years from index TKA. ITPIE for failed TKA is associated with unpredictable outcomes. ITPIE, even with well-defined and narrow indications, should be undertaken with caution. The longer the initial components performed successfully before ITPIE, the greater the likelihood of success after ITPIE.,[object Object]

High Incidence of Complications From Enoxaparin Treatment After Arthroplasty

Andrew S. Neviaser MD, Charles Chang MD, Stephen Lyman PhD, Alejandro Gonzales Della Valle MD, Steven B. Haas MD Pulmonary embolism (PE) complicates 1% to 10% of total joint arthroplasties and generally requires immediate anticoagulation. Low-molecular-weight heparins have supplanted unfractionated heparin as the treatment of choice for PE and hold a 1A recommendation from the American College of Chest Physicians for this indication. However, the complications of enoxaparin treatment begun in close proximity to arthroplasty surgery are not well described. We examined the records of 135 patients who underwent total joint arthroplasty, experienced an in-hospital PE, and received treatment with enoxaparin at therapeutic doses (1 mg/kg body weight). The type and frequency of complications were determined and classified as major or minor. Twenty-seven percent of patients experienced minor complications and 10% experienced major complications. The incidence of major bleeding was substantially higher than rates reported for nonsurgical patients. The overall complication rate of enoxaparin treatment is similar to the rate of complications reported for unfractionated heparin treatment in this setting, but the complications are less severe.,[object Object]

Survival of Bicompartmental Knee Arthroplasty at 5 to 23 Years

Sebastien Parratte MD, Vanessa Pauly MS, Jean-Manuel Aubaniac MD, Jean-Noel A. Argenson MD Recent literature suggests patients achieve substantial short-term functional improvement after combined bicompartmental implants but longer-term durability has not been documented. We therefore asked whether (1) bicompartmental arthroplasty (either combined medial unicompartmental knee arthroplasty (UKA) and femoropatellar arthroplasty (PFA) or medial UKA/PFA, or combined medial and lateral UKA or bicompartmental UKA) reliably improved Knee Society pain and function scores; (2) bicompartmental arthroplasty was durable (survivorship, radiographic loosening, or symptomatic disease progression); (3) we could achieve durable alignment; and (4) the arthritis would progress in the unresurfaced compartment. We retrospectively reviewed 84 patients (100 knees) with bicompartmental UKA and 71 patients (77 knees) with medial UKA/PFA. Clinical and radiographic evaluations were performed at a minimum followup of 5 years (mean, 12 years; range, 5–23 years). Bicompartmental arthroplasty reliably alleviated pain and improved function. Prosthesis survivorship at 17 years was 78% in the bicompartmental UKA group and 54% in the medial UKA/PFA group. The high revision rate, compared with total knee arthroplasty, may be related to several factors such as implant design, patient selection, crude or absent instrumentation, or component malalignment, which can all contribute to the relatively high failure rate in this series.,[object Object]

The John Insall Award: Both Morphotype and Gender Influence the Shape of the Knee in Patients Undergoing TKA

Johan Bellemans MD, PhD, Karel Carpentier MD, Hilde Vandenneucker MD, Johan Vanlauwe MD, Jan Victor MD There is an ongoing debate whether gender differences in the dimensions of the knee should influence the design of TKA components. We hypothesized that not only gender but also the patient’s morphotype determined the shape of the distal femur and proximal tibia and that this factor should be taken into account when designing gender-specific TKA implants. We reviewed all 1000 European white patients undergoing TKA between April 2003 and June 2007 and stratified each into one of three groups based on their anatomic constitution: endomorph, ectomorph, or mesomorph. Of the 250 smallest knees, 98% were female, whereas 81% of the 250 largest knees were male. In the group with intermediate-sized knees, female knees were narrower than male knees. Patients with smaller knees (predominantly female) demonstrated large variability between narrow and wide mediolateral dimensions irrespective of gender. The same was true for larger knees (predominantly male). This variability within gender could partially be explained by morphotypic variation. Patients with short and wide morphotype (endomorph) had, irrespective of gender, wider knees, whereas patients with long and narrow morphotype (ectomorph) had narrower knees. The shape of the knee is therefore not only dependent on gender, but also on the morphotype of the patient.,[object Object]

Prophylactic Antibiotics Do Not Affect Cultures in the Treatment of an Infected TKA: A Prospective Trial

R. Stephen J. Burnett MD, FRCS(C), Ajay Aggarwal MD, Stephanie A. Givens RN, J. Thomas McClure MD, Patrick M. Morgan MD, Robert L. Barrack MD Prophylactic antibiotics are frequently withheld until cultures are obtained in revision total knee arthroplasty (TKA). We undertook a prospective study to determine whether prophylactic preoperative intravenous antibiotics would affect the results of cultures obtained intraoperatively. We enrolled 25 patients with 26 infected TKAs, a known preoperative infecting organism, and no recent antibiotic therapy. Reaspiration of the infected TKA was performed after anesthesia and sterile preparation. Intravenous antibiotic prophylaxis was then administered and the tourniquet inflated. Intraoperative culture swabs and tissue were obtained at arthrotomy. The timing of events was recorded. Pre- and postantibiotic culture data were analyzed to determine the effect of intravenous preoperative prophylactic antibiotics on cultures obtained intraoperatively. Infections were acute postoperative (four), chronic (19), and acute hematogenous (three). The most common infecting organism was cloxacillin-sensitive Staphylococcus aureus (nine knees [35%]). Preoperative prophylactic antibiotics did not affect the results of intraoperative cultures and we therefore believe should not be withheld before surgery for an infected TKA when an organism has been identified on aspiration preoperatively, and there has been no recent (4 weeks) antimicrobial therapy.,[object Object]

Prosthetic Joint Infection Risk after TKA in the Medicare Population

Steven M. Kurtz PhD, Kevin L. Ong PhD, Edward Lau MS, Kevin J. Bozic MD, MBA, Daniel Berry MD, Javad Parvizi MD The current risk of infection in contemporary total knee arthroplasty (TKA) as well as the relative importance of risk factors remains under debate as a result of the rarity of the complication and temporal changes in the treatment and prevention of infection. We therefore determined infection incidence and risk factors after TKA in the Medicare population. The Medicare 5% national sample administrative data set was used to identify and longitudinally follow patients undergoing TKA for deep infections and revision surgery between 1997 and 2006. Cox regression was used to evaluate patient and hospital characteristics. In 69,663 patients undergoing elective TKA, 1400 TKA infections were identified. Infection incidence within 2 years was 1.55%. The incidence between 2 and up to 10 years was 0.46%. Women had a lower risk of infection than men. Comorbidities also increased TKA infection risk. Patients receiving public assistance for Medicare premiums were at increased risk for periprosthetic joint infection (PJI). Hospital factors did not predict an increased risk of infection. PJI occurs at a relatively high rate in Medicare patients with the greatest risk of PJI within the first 2 years after surgery; however, approximately one-fourth of all PJIs occur after 2 years.,[object Object]

Autologous Chondrocyte Implantation for Joint Preservation in Patients with Early Osteoarthritis

Tom Minas MD, MS, Andreas H. Gomoll MD, Shahram Solhpour MD, Ralf Rosenberger MD, Christian Probst BS, Tim Bryant RN [object Object],[object Object]

Robotic Arm-assisted UKA Improves Tibial Component Alignment: A Pilot Study

Jess H. Lonner MD, Thomas K. John MD, Michael A. Conditt PhD The alignment of the components of unicompartmental knee arthroplasty (UKA) reportedly influences outcomes and durability. A novel robotic arm technology has been developed with the expectation that it could improve the accuracy of bone preparation in UKA. During the study period, we compared the postoperative radiographic alignment of the tibial component with the preoperatively planned position in 31 knees in 31 consecutive patients undergoing UKA using robotic arm-assisted bone preparation and in 27 consecutive patients who underwent unilateral UKA using conventional manual instrumentation to determine the error of bone preparation and variance with each technique. Radiographically, the root mean square error of the posterior tibial slope was 3.1° when using manual techniques compared with 1.9° when using robotic arm assistance for bone preparation. In addition, the variance using manual instruments was 2.6 times greater than the robotically guided procedures. In the coronal plane, the average error was 2.7° ± 2.1° more varus of the tibial component relative to the mechanical axis of the tibia using manual instruments compared with 0.2° ± 1.8° with robotic technology, and the varus/valgus root mean square error was 3.4° manually compared with 1.8° robotically. Further study will be necessary to determine whether a reduction in alignment errors of these magnitudes will ultimately influence implant function or survival.,[object Object]

Does Bearing Design Influence Midterm Survivorship of Unicompartmental Arthroplasty?

John-Paul Whittaker MB ChB, FRCS (T&O), Douglas D. R. Naudie MD, FRCS (C), James P. McAuley MD, FRCS (C), Richard W. McCalden MD, MPhil, FRCS (C), Steven J. MacDonald MD, FRCS (C), Robert B. Bourne MD, FRCS (C) Medial unicompartmental arthroplasties (UKA) are available with mobile- and fixed-bearing designs, with the advantages of one bearing over another unproven. We questioned whether the bearing design influenced clinical outcome, survivorship, the reason for revision, or the timing of failures. We retrospectively reviewed 179 patients (229 knees) who had medial unicompartmental knee arthroplasties between 1990 and 2007; of these 79 knees had a mobile-bearing design and 150 knees a fixed-bearing design. Patients with mobile-bearing UKA had a minimum followup of 1 year (mean, 3.6 years; range, 1–11.3 years); those with fixed-bearing UKA a minimum followup of 1 year (mean, 8.1 years; range, 1–17.8 years). Patients were evaluated with clinical outcome scores and radiographically using the Knee Society rating system. Seven of 79 (9%) mobile-bearing knees underwent revision at a mean of 2.6 years, and 22 of 150 (15%) fixed-bearing knees underwent revision at a mean of 6.9 years. The 5-year cumulative survival rates were 88% (SE ± 0.47, 95% CI 0.7229–1) and 96% (SE ± 0.16, 95% CI 0.93–0.9979) for the mobile- and fixed-bearing designs respectively using the endpoint of revision surgery. We observed no differences in the indications or complexity of revision surgery between the groups and none in midterm survivorship.,[object Object]

The Epidemiology of Revision Total Knee Arthroplasty in the United States

Kevin J. Bozic MD, MBA, Steven M. Kurtz PhD, Edmund Lau MS, Kevin Ong PhD, Vanessa Chiu MPH, Thomas P. Vail MD, Harry E. Rubash MD, Daniel J. Berry MD Understanding the cause of failure and type of revision total knee arthroplasty (TKA) procedures performed in the United States is essential in guiding research, implant design, and clinical decision making in TKA. We assessed the causes of failure and specific types of revision TKA procedures performed in the United States using newly implemented ICD-9-CM diagnosis and procedure codes related to revision TKA data from the Nationwide Inpatient Sample (NIS) database. Clinical, demographic, and economic data were reviewed and analyzed from 60,355 revision TKA procedures performed in the United States between October 1, 2005 and December 31, 2006. The most common causes of revision TKA were infection (25.2%) and implant loosening (16.1%), and the most common type of revision TKA procedure reported was all component revision (35.2%). Revision TKA procedures were most commonly performed in large, urban, nonteaching hospitals in Medicare patients ages 65 to 74. The average length of hospital stay (LOS) for all revision TKA procedures was 5.1 days, and the average total charges were $49,360. However, average LOS, average charges, and procedure frequencies varied considerably by census region, hospital type, and procedure performed.,[object Object]

The Mark Coventry Award Articular: Contact Estimation in TKA Using In Vivo Kinematics and Finite Element Analysis

Fabio Catani MD, Bernardo Innocenti PhD, Claudio Belvedere PhD, Luc Labey PhD, Andrea Ensini MD, Alberto Leardini PhD In vivo fluoroscopy is a well-known technique to analyze joint kinematics of the replaced knee. With this method, however, the contact areas between femoral and tibial components, fundamental for monitoring wear and validating design concepts, are hard to identify. We developed and tested a novel technique to assess condylar and post-cam contacts in TKA. The technique uses in vivo motion data of the replaced knee from standard fluoroscopy as input for finite element models of the prosthesis components. In these models, tibiofemoral contact patterns at the condyles and post-cam articulations were calculated during various activities. To test for feasibility, the technique was applied to a bicruciate posterior-stabilized prosthesis. Sensitivity of the finite element analysis, validation of the technique, and in vivo tests were performed. To test for potential in the clinical setting, five patients were preliminarily analyzed during chair rising-sitting, stair climbing, and step up-down. For each task and patient, the condylar contact points and contact line rotation were calculated. The results were repeatable and consistent with corresponding calculations from traditional fluoroscopic analysis. Specifically, natural knee kinematics, which shows rolling back and screw home, seemed replicated in all motor tasks. Post-cam contact was observed on both the anterior and posterior faces. Anterior contact is limited to flexion angle close to extension; posterior contact occurs in deeper flexion but is dependent on the motor task. The data suggest the proposed technique provides reliable information to analyze post-cam contacts.

The Chitranjan Ranawat Award: The Nonoperated Knee Predicts Function 3 Years after Unilateral Total Knee Arthroplasty

Sara Farquhar PhD, PT, Lynn Snyder-Mackler PT, ScD, FAPTA The long-term functional abilities of patients after a unilateral total knee arthroplasty (TKA) are influenced by the status of the nonoperated knee at the time of the TKA. We hypothesized that in the 3 years after TKA, the nonoperated limb would become more painful, and the quadriceps muscles would weaken; pain and strength would influence performance on functional testing by 3 years after TKA. Healthy control subjects were tested over the same time interval; we hypothesized the controls would also decline in strength and function over time. Individuals with unilateral knee pain (less than 4/10 on a verbal analog scale) were recruited preoperatively. We tested patients 1, 2, and 3 years after TKA to determine changes in strength, self-report outcome measures, and performance on a stair climbing test and the 6-minute walk test. Control subjects without osteoarthritis were tested twice, 2 years apart. The nonoperated limb of patients with TKA weakened from 1 to 2 years, and further weakened from 2 to 3 years after TKA; by 3 years after TKA, the nonoperated limb was more painful compared to the operated limb. Three years after TKA, nonoperated knee pain contributed 44% of the variability in the 6-minute walk and 33% of the variability in the stair climbing test. Patients with TKA were weaker, slower, and had lower self-report outcome measures compared with control subjects at both time intervals. Control subjects also weakened over time, yet were stable on self-report outcome measures and the 6 minute walk test. Weakening of the quadriceps muscles in all participants represents changes due to ageing; however on average the nonoperated limb weakened over time, possibly representing not only changes resulting from aging, but progression of osteoarthrosis in some patients with unilateral TKA.,[object Object]

Intraoperative Fracture During Primary Total Knee Arthroplasty

Kris J. Alden MD, PhD, William H. Duncan MD, Robert T. Trousdale MD, Mark W. Pagnano MD, George J. Haidukewych MD While the occurrence of periprosthetic fractures around total knee arthroplasties (TKAs) is well know, little is known about intraoperative fractures that occur during TKA. We describe the incidence, location, and outcomes of iatrogenic intraoperative fracture during primary TKA. We reviewed 17,389 primary TKAs performed between 1985 and 2005 and identified 66 patients with 67 intraoperative fractures including 49 femur fractures, 18 tibia fractures, and no patella fractures. There were 12 men and 54 women with a mean age of 65.2 ± 16 years. Of the 49 femur fractures, locations included medial condyle (20), lateral condyle (11), supracondylar femur (eight), medial epicondyle (seven), lateral epicondyle (two), and posterior cortex (one). Tibia fractures (18) included lateral plateau (six), anterior cortex (four), medial plateau (three), lateral cortex (three), medial cortex (one), and posterior cortex (one). Twenty-six fractures occurred during exposure and preparation, 22 while trialing, 13 during cementation, and three while inserting the polyethylene spacer. The minimum followup was 0.15 years (mean, 5.1 years; range, 0.15–15.4 years). All fractures healed clinically and radiographically. Knee Society scores and function scores improved from 46.4 and 34.6 to 79.5 and 61, respectively. Fourteen of the 66 (21%) patients were revised at an average of 2.8 years. Intraoperative fracture is an uncommon complication of primary TKA with a prevalence of 0.39%. Intraoperative fracture occurred more commonly in women (80.6%) and in the femur (73.1%). The majority of fractures occurred during exposure and bone preparation and trialing of the components.,[object Object]

Highly Crosslinked Polyethylene is Safe for Use in Total Knee Arthroplasty

Jeffrey T. Hodrick MD, Erik P. Severson MD, Deborah S. McAlister MD, Brian Dahl BS, Aaron A. Hofmann MD Highly cross-linked polyethylene (XLPE) has been used with good initial success in hip arthroplasty to reduce wear. However, the process of crosslinking reduces fracture toughness, raising concerns as to whether it can be safely used in total knee arthroplasty (TKA). We therefore asked whether XLPE can be used safely in TKA. We performed a retrospective review of 100 subjects receiving XLPE and compared them to 100 subjects who received standard polyethylene in the setting of TKA. The standard polyethylene group had a mean age of 70 with a minimum follow up of 82 months. The highly cross-linked polyethylene group had a mean age of 67 and a minimum follow up of 69 months (mean, 75 months; range, 69–82 months). On radiographic review, the standard group demonstrated 20 TKAs with radiolucencies; 4 of these had evidence of a loose tibial component. The standard group required three revisions related to loose tibial components. The XLPE group had 2 subjects that demonstrated radiolucencies on radiograph and no subjects with evidence of tibial loosening. There were no reoperations related to osteolysis. The data suggest XLPE in TKA can be used safely at least short- to midterm. Our study provides an impetus for further long-term investigation.,[object Object]

Diagnosis of Infected Total Knee: Findings of a Multicenter Database

Javad Parvizi MD, FRCS, Elie Ghanem MD, Peter Sharkey MD, Ajay Aggarwal MD, R. Stephen J. Burnett MD, FRCS(C), Robert L. Barrack MD Although total knee arthroplasty (TKA) is an effective and successful procedure, the outcome is occasionally compromised by complications including periprosthetic joint infection (PJI). Accurate and early diagnosis is the first step in effectively managing patients with PJI. At the present time, diagnosis remains dependent on clinical judgment and reliance on standard clinical tests including serologic tests, analysis of aspirated joint fluid, and interpretation of intraoperative tissue and fluid test results. Although reports regarding sensitivity and specificity of all diagnostic tests in the literature are abundant, the interpretation of the available data has been hampered by the low sample size of these studies. In view of the scope of this important problem and the limitations of previous reports, a large database was assembled of all revision TKA performed at three academic referral centers in order to determine the current status of diagnosis of the infected TKA utilizing commonly available tests. Intraoperative cultures should not be used as a gold standard for PJI owing to high percentages of false-negative and false-positive cases. When combined with clinical judgment, total white cell count and percentage of neutrophils in the synovial fluid more accurately reflects PJI and when combined with hematologic exams safely excludes or confirms infection.,[object Object]

Polyethylene Wear Is Influenced by Manufacturing Technique in Modular TKA

Adolph V. Lombardi MD, FACS, Bradley S. Ellison MD, Keith R. Berend MD Polyethylene insert backside surface wear is implicated in osteolysis and failure of total knee arthroplasty. Manufacturing and sterilization methods reduce articular-sided wear. We questioned whether manufacturing technique influences the severity of backside wear. We examined 39 explanted tibial bearings in a blinded fashion using visual, stereomicroscopic, and scanning electron microscopic techniques. We examined 26 direct compression molded components and 13 nondirect compression molded components and applied a new backside wear severity score. The score characterized the magnitude of the various modes of wear with severity ranging from 0 (no wear) to 27 (severe wear). Time in vivo, tibial baseplate material, and manufacturing technique were used as variables for comparison. Backside wear was related to polyethylene manufacturing process with direct compression molded implants having a wear score of 2.3 and nondirect compression molded a score of 5.7. Time in vivo influenced backside wear, although direct compression molded predicted decreased backside wear independent of time in vivo. The data suggest manufacturing technique influences backside wear in total knee arthroplasty polyethylene inserts.

Measuring Tools for Functional Outcomes in Total Knee Arthroplasty

Robert B. Bourne MD, FRCSC Total knee arthroplasty has come under increasing scrutiny attributable to the fact that it is a high-volume, high-cost medical intervention in an era of increasingly scarce medical resources. Health-related quality-of-life outcomes have been developed such that healthcare providers might determine how good an intervention is and whether it is cost-effective. Total knee arthroplasty has been subjected to disease-specific, patient-specific, global health, functional capacity, and cost-to-utility outcome measures. Patient satisfaction is high (90%) after total knee arthroplasty and 93% of patients would have this operative procedure again. Large improvements in preoperative to postoperative WOMAC scores occurred (over 39 of 100 points in 82% of patients). Cost-to-quality outcomes demonstrated total knee arthroplasties are extremely cost-effective. This analysis documents total knee arthroplasty is a highly efficacious procedure that competes favorably with all medical and surgical interventions.

Rotating Platform versus Fixed-bearing Total Knees: An In Vitro Study of Wear

Hani Haider PhD, Kevin Garvin MD One of the assumed benefits of mobile bearings is the reduction of UHMWPE wear. However, to date, such benefit has not been categorically proven. To test the hypothesis that rotating platform total knee arthroplasty would have less wear than a fixed-bearing of the same design, this in vitro study compared the wear and kinematics (which influence wear) of one type of mobile with fixed-bearing tibial components of otherwise identical design. We tested four fixed bearing (FB) and four rotating platforms (RP) on force control knee simulators using identical ISO standard force inputs and simulated soft tissue restraint for 6 million walking cycles. The internal/external rotations peaked just before toe off, reaching an average maximum of 7° internal (tibial rotation) in the RP, 1.5 times that of the FB, which peaked at approximately 4.5° internally. Two of the RP specimens showed infrequent and mostly temporary dislocations of the UHMWPE insert. The wear rate for the FB averaged 8.14 ± 2.63 mg/million cycles and the RP averaged 6.78 ± 1.74 mg/million cycles. Both were very low wear rates compared with most other implants tested similarly in the same laboratory. We concluded polyethylene wear was similar for both designs.

The Classic: Total Condylar Knee Replacement in Patients Who Have Rheumatoid Arthritis. A Ten-Year Follow-Up Study

Richard S. Laskin MD Eighty knee replacements with a total condylar prosthesis in patients who had rheumatoid arthritis were followed for ten years. At ten years, nineteen knees needed revision and sixty-one prostheses were still functioning. The major reasons for revision were loosening of the tibial component or late bacteremic seeding from another site. Radiolucency at the bone-cement interface adjacent to the tibial component was statistically related to malposition of the tibial component. According to the system of The Hospital for Special Surgery, the mean scores were 64 points preoperatively and 85 points postoperatively. Synovitis recurred in only 3 per cent of the knees. When revision, pain, or radiographic evidence of loosening were considered an indication of failure, the ten-year cumulative survival was 75 per cent.

The Classic: Modular Total Knee-Replacement Arthroplasty. A Review of Eighty-nine Patients

Richard S. Laskin MD Fifty-eight osteoarthritic and thirty-one rheumatoid patients underwent modular total knee-replacement arthroplasty. The major indication for the operation was relief of pain. Contraindications to this resurfacing arthroplasty included varus-valgus instability of over 20 degrees, combined varus-valgus instability with flexion contracture of over 40 degrees, marked recurvatum, and predominant patellofemoral symptoms. In 59 per cent of the osteoarthritic and 58 per cent of the rheumatoid patients, complete relief of pain was evident when they were evaluated twenty-four months after surgery, while another 35 per cent of each group had only mild pain related to inclement weather. Their ability to walk long distances without support or limp was increased. Range of motion and ability to climb stairs were not significantly improved.

Restoration of Femoral Anatomy in TKA With Unisex and Gender-specific Components

Henry D. Clarke MD, Joseph G. Hentz MS Recent modifications in total knee prosthesis design theoretically better accommodate the anatomy of the female femur and thereby have the theoretical potential to improve clinical results in TKA by more accurately restoring femoral posterior condylar offset, reducing femoral notching, reducing femoral component flexion, and reducing component overhang. First, we radiographically evaluated whether a contemporary unisex prosthesis would accommodate female anatomy equally as well as male anatomy. Next, we radiographically evaluated female knees in which a gender-specific prosthesis was used. Pre- and postoperative radiographs of 122 knees (42 female unisex, 41 male unisex, 39 female gender-specific) were reviewed. In the unisex groups, there were no differences in femoral notching or femoral component flexion. Posterior femoral offset increased in both groups. However, femoral component overhang was worse in female knees (17%) than in male knees (0%). In the gender-specific female group, the incidence of component overhang was similar to that in the unisex female group. Unisex femoral components of this specific design do not equally match the native anatomy male and female knees. In some women, a compromise was required in sizing.

Rotational Position of Femoral and Tibial Components in TKA Using the Femoral Transepicondylar Axis

Paolo Aglietti MD, Lorenzo Sensi MD, Pierluigi Cuomo MD, Antonio Ciardullo MD, PhD Proper femoral and tibial component rotational positioning in TKA is critical for outcomes. Several rotational landmarks are frequently used with different advantages and limitations. We wondered whether coronal axes in the tibia and femur based on the transepicondylar axis in the femur would correlate with anteroposterior deformity. We obtained computed tomography scans of 100 patients with arthritis before they underwent TKA. We measured the posterior condylar angle on the femoral side and the angle between Akagi’s line and perpendicular to the projection of the femoral transepicondylar axis on the tibial side. On the femoral side, we found a linear relationship between the posterior condylar angle and coronal deformity with valgus knees having a larger angle than varus knees, ie, gradual external rotation increased with increased coronal deformity from varus to valgus. On the tibial side, the angle between Akagi’s line and the perpendicular line to the femoral transepicondylar axis was on average approximately 0°, but we observed substantial interindividual variability without any relationship to gender or deformity. A preoperative computed tomography scan was a useful, simple, and relatively inexpensive tool to identify relevant anatomy and to adjust rotational positioning. We do not, however, recommend routine use because on the femoral side, we found a relationship between rotational landmarks and coronal deformity.

Effect of Gender and Preoperative Diagnosis on Results of Revision Total Knee Arthroplasty

Stephanie Y. Pun MD, Michael D. Ries MD Recent studies question an effect of gender on outcome of primary TKA. We questioned whether the results of revision TKA were affected by gender. We separated 67 revision TKAs by gender and preoperative diagnosis into four groups (arthrofibrosis, infection, instability, and wear and loosening). Each revision TKA was individually matched by age and gender to two primary TKAs. Postoperative Knee Society pain and function scores after revision TKA were lower than for primary TKA for both females and males. However, postoperative Knee Society pain and function scores were similar in males and females. Postoperative pain and function scores were lower for all revision groups compared with primary TKA, except for pain and function scores after revision for instability. Postoperative pain and function scores were higher for instability and wear or loosening than for arthrofibrosis. Our data suggest the results of revision TKA are affected by preoperative diagnosis but not gender.,[object Object]

Posterior Cruciate-retaining Total Knee Arthroplasty for Valgus Osteoarthritis

James P. McAuley MD, Matthew B. Collier MS, W. G. Hamilton MD, Ehsan Tabaraee MS, G. A. Engh MD The valgus, osteoarthritic knee is challenging technically and it is unknown whether and how technical and implant variables influence outcomes. We therefore determined the influence of surgical technique of soft tissue balancing and patient and implant factors from 100 unselected cruciate-retaining TKAs for valgus osteoarthritis in patients younger than 75 years of age. From 1987 to 1990, lateral soft tissue balancing was done with an outside-in progression in which the lateral collateral ligament and popliteus were typically released from the femur. From 1991 to 1994, an inside-out technique was use in which the lateral collateral ligament and/or popliteus were typically preserved. The minimum followup was 0.1 year (mean, 8.2 years; range, 0.1–18.2 years). Fourteen of 16 revisions were for wear and/or instability. Popliteus release, lateral collateral ligament release, or greater polyethylene shelf age increased the risk of revision. At 10 postoperative years, survival (end point, revision) was 89% (100 knees), 94% when the shelf age was less than 1 year (n = 73 knees), 97% when the popliteus or lateral collateral ligament was not released (n = 57 knees), and 100% when both conditions were met (n = 39 knees). Cruciate-retaining implants can be successfully used in knees with any degree of valgus osteoarthritis and survival is improved when the surgeon preserves at least one of the structures providing lateral stability in flexion and uses polyethylene with a short shelf life.,[object Object]

Less Invasive TKA

Andrea Baldini MD, Paolo Adravanti MD Femoral intramedullary canal referencing is used by most knee arthroplasty systems. Fat embolism, activation of coagulation, and bleeding may occur from the reamed canal. The purpose of our study was to evaluate a new extramedullary device that relies on templated data. We randomized 100 consecutive patients undergoing primary total knee arthroplasty through a limited parapatellar approach to use of either standard intramedullary femoral instruments (IM group) or a new extramedullary device (EM group). The extramedullary instrument was calibrated using templated data obtained from a preoperative full-limb weightbearing anteroposterior view of the knee. In both groups, an intraoperative double check was performed using an extramedullary rod referring to the anterosuperior iliac spine. Femoral component coronal alignment was within 0° ± 2° of the mechanical axis in 84% of the IM group and 86% of the EM group. Sagittal alignment of the femoral component was 0° ± 2° in 78% of the IM group and 90% of the EM group. We observed no difference in the average operative time between the two groups. The two groups showed similar postoperative blood loss. Extramedullary reference with careful preoperative templating can be safely used during TKA.,[object Object]

Management of the Deficient Patella in Revision Total Knee Arthroplasty

Ryan M. Garcia MD, Matthew J. Kraay MS, MD, Patricia A. Conroy-Smith RN, Victor M. Goldberg MD There are a number of options available to manage the patella when revising a failed total knee arthroplasty. If the previous patellar component is well-fixed, undamaged, not worn, and compatible with the femoral revision component, then it can be retained. When a patellar component necessitates revision and is removed with adequate remaining patellar bone stock, an onlay-type all-polyethylene cemented implant can be used. Management of the patella with severe bony deficiency remains controversial. Treatment options for the severely deficient patella include the use of a cemented all-polyethylene biconvex patellar prosthesis, patellar bone grafting and augmentation, patellar resection arthroplasty (patelloplasty), performing a gull-wing osteotomy, patellectomy, or the use of newer technology such as a tantalum (trabecular metal) patellar prosthesis. Severe patellar bone deficiency is a challenging situation because restoration of the extensor mechanism, proper patellar tracking, and satisfactory anatomic relationships with the femoral and tibial components are critical for an optimal clinical outcome.,[object Object]

Men versus Women

Roger H. Emerson MD, Jessica Martinez MD The role played by femoral component sizing in the clinical outcome of primary TKA is currently debated. Oversizing the femur in patients with smaller knees could lead to overstuffing the knee capsule with resulting pain and reduced range of motion. We asked whether the distribution of femoral component sizes differed between genders and whether the availability of additional sizes benefited genders differently and led to a measurable improvement in knee flexion and Knee Society scores or pain. We retrospectively examined two groups of consecutive knees of patients who underwent primary TKA using similar techniques and constraint: Group 1 (93 men and 90 women) who had available four original sizes and Group 2 (106 men and 106 women) after the introduction of three new smaller sizes. More than twice as many new smaller sizes were used in women (52.3%, 56 of 106) compared to men (17.9%, 19 of 106). At the scheduled 6-month followup visit (average, 6 months; range, 5–7 months), we found no differences in the knee score, pain score, and knee flexion in men and women before the additional sizes (Group 1) and after the new sizes (Group 2). Additional sizes therefore did not appear to influence short-term outcomes.,[object Object]

The John Insall Award: Gender-specific Total Knee Replacement: Prospectively Collected Clinical Outcomes

Steven J. MacDonald MD, FRCSC, Kory D. Charron MET, Robert B. Bourne MD, FRCSC, Douglas D. Naudie MD, FRCSC, Richard W. McCalden MD, FRCSC, Cecil H. Rorabeck MD, FRCSC Gender-specific total knee replacement design is a recent and debated topic. We determined the survivorship and clinical outcomes of a large primary total knee arthroplasty cohort, specifically assessing any differences between gender groups. A consecutive cohort of 3817 patients with 5279 primary total knee replacements (3100 female, 2179 male) with a minimum of 2 years followup were evaluated. Preoperative, latest, and change in clinical outcome scores (WOMAC, SF-12, KSCRS) were compared. While men had higher raw scores preoperatively, women had greater improvement in all WOMAC domains including pain (29.87 versus 27.3), joint stiffness (26.78 versus 24.26), function (27.21 versus 23.09), and total scores (28.35 versus 25.09). There were no gender differences in improvements of the SF-12 physical scores. Men had greater improvement in Knee Society function (22.1 versus 18.63) and total scores (70.01 versus 65.42), but not the Knee Society knee score (47.83 versus 46.64). Revision rates were 10.2% for men and 8% for women. Women demonstrated greater implant survivorship, greater improvement in WOMAC scores, equal improvements in SF-12 scores, and less improvement in only the Knee Society function and total scores. The data refute the hypothesis of inferior clinical outcome for women following total knee arthroplasty when using standard components.,[object Object]

Computer Navigation-assisted versus Minimally Invasive TKA

Peter M. Bonutti MD, Daniel Dethmers MD, Slif D. Ulrich MD, Thorsten M. Seyler MD, Michael A. Mont MD Computer-navigated and minimally invasive TKAs are emerging technologies that have distinct strengths and weaknesses. We compared duration of surgery, length of hospitalization, Knee Society scores, radiographic alignments, and complications in two unselected groups of 81 consecutive knees that underwent TKA using either a minimally invasive approach or computer navigation. The two groups were operated on by two different surgeons over differing timeframes. The mean surgical time was longer in the navigated group by 63 minutes. The Knee Society scores and lengths of hospitalization of the two groups were similar. The postoperative component alignments of the two groups were similar; the mean femoral valgus and tibial varus angles of the navigation group changed from 96° and 88° preoperatively to 95° and 89° postoperatively, respectively, and in the minimally invasive group, the mean femoral valgus angles and tibial varus angles changed from 97° and 88° preoperatively to 95° and 89° postoperatively, respectively. There were 11 major and three minor complications in the navigation group, including one revision, two femoral shaft fractures, four reoperations for knee stiffness, and four instances of bleeding from tracker sites. We believe the higher incidence of complications in addition to the longer operative time in the navigated group may outweigh any potential radiographic benefits.,[object Object]

The Chitranjan Ranawat Award

Patricia D. Franklin MD, Wenjun Li PhD, David C. Ayers MD Total knee replacement effectively relieves arthritis pain but improvement in physical function varies. A clearer understanding of the patient attributes associated with differing levels of functional gain after TKR is critical to surgical decision making. We reviewed 8050 primary, unilateral TKR patients enrolled in a prospective registry between 2000 and 2005 who had complete data. We evaluated associations between 12-month function (SF12/PCS) and preoperative gender, age, BMI, emotional health (MCS), knee diagnosis, quadriceps strength, and physical function (PCS). More than 98% of patients reported pain relief (KS pain score). At 12 months, mean PCS gain was 13.6 points, but the distribution was bimodal. The mean gain in PCS in the 63% of patients with greater improvement was 21 (SD = 7), and 4.1 (SD = 7) in the remaining 37%. Increased likelihood of poor functional gain was associated with older age, body mass index (BMI) over 40, lower MCS, and poor quadriceps strength. While two-thirds of patients reported functional gain well above national average at 12 months post-TKR, 37% reported limited functional improvement. Further understanding of the patient attributes associated with limited improvement will guide the design of innovative strategies to improve functional outcomes.,[object Object]

Radiographic and Navigation Measurements of TKA Limb Alignment Do Not Correlate

Mark A. Yaffe MD, Samuel S. Koo MD, S. David Stulberg MD Precise pre- and postoperative anatomic measurements are necessary to plan, perform, and evaluate total knee arthroplasty (TKA). We evaluated the relationship between radiographic and navigation alignment measurements, identified sources of error in radiographic and navigated alignment assessment, and determined the differences between desired and clinically accepted alignment. Fifty-eight computer-assisted TKAs were performed and limb alignment measurements were recorded both pre- and postoperatively with standard radiographs and with an intraoperative navigation system. Intraoperative navigation produced consistent navigation-generated alignment results that were within 1° of the desired alignment. The difference between preoperative radiographic and navigation measurements varied by as much as 12° and the difference between postoperative radiographic and navigation measurements varied by as much as 8°. This discrepancy depended on the degree of limb deformity. Postoperative radiographic measurements have inherent limitations. Navigation can generate precise, accurate, and reproducible alignment measurements. This technology can function as an effective tool for assessing pre- and postoperative limb alignment and relating intraoperative alignment measurements to clinical and functional outcomes.,[object Object]

Determining Femoral Component Position Using CAS and Measured Resection

James Benjamin MD To evaluate the ability of computer-assisted surgery (CAS) to accurately size and determine rotational alignment of the femoral component in TKA, the author reviewed femoral component position after 50 consecutive primary TKAs using a femur-first, measured resection workflow. The computer software used allowed femoral rotation to be selected based on epicondylar axis, posterior condylar axis, or anteroposterior axis. The final femoral component size and position was determined by the surgeon to avoid anterior notching, match the posterior-medial condyle resection, and flexed to match the plane of the anterior femoral cortex. Femoral sizing was confirmed intraoperatively with a standard sizing guide. The femoral component was downsized in 52% of patients from the size recommended by the computer software. The posterior condylar axis matched the implanted rotational position of the femoral component to within 1° in 64% of patients in contrast to the epicondylar axis (32%) and anteroposterior axis (26%). CAS provides information to make surgical decisions but does not replace clinical judgment. Landmark referencing may be compromised by limited surgical exposures leading to variation in implant positioning by computer software. A clear understanding of the principles of TKA is critical when using CAS to optimize implant sizing and position.

Lateral Retinacular Release Rates in Mobile- versus Fixed-bearing TKA

Charles C. Yang MD, Lee A. McFadden LTC, MD, Douglas A. Dennis MD, Raymond H. Kim MD, Adrija Sharma MS Controversy exists as to whether bearing mobility facilitates centralization of the extensor mechanism after TKA. To assess the incidence of lateral retinacular release, we retrospectively reviewed 1318 consecutive primary TKAs (1032 patients) performed by one surgeon using either a rotating-platform bearing (940) or a fixed bearing (378) from the same implant system. The selection of a fixed- versus mobile-bearing TKA was primarily based on age with patients younger than 70 years receiving a mobile-bearing TKA. We performed a lateral release whenever continuous symmetric patellar facet contact with the trochlear groove from 0° to 90° of flexion was not obtained using the rule of no thumb after tourniquet release. One hundred four of 1318 knees (7.9%) had a lateral release. We performed more lateral releases in the fixed-bearing group (14.3% [54 of 378]) than in the mobile-bearing group (5.3% [50 of 940]). Patellar tilt occurred more often in the mobile-bearing group (10% [94 of 940]) than in the fixed-bearing group (6.9% [26 of 378]), although the magnitude of mean patellar tilt was small in both groups (mobile-bearing 3.0°; fixed bearing 2.55°). No patient had patellar subluxation greater than 5 mm. We suspect the fewer lateral releases in the mobile-bearing group is the result of better extensor mechanism centralization provided by bearing rotation.,[object Object]

Stemmed Implants Improve Stability in Augmented Constrained Condylar Knees

Jeremy J. Rawlinson PhD, Robert F. Closkey MD, Nicole Davis, Timothy M. Wright PhD, Russell Windsor MD We previously combined experimental and computational measures to ascertain whether tibial stem augmentation reduces bone strains beneath constrained condylar implants. Using these same integrated approaches, we examined the benefit of a stem when a wedge is used. Implants were removed from the eight paired cadaver specimens from our previous experiment, and oblique defects created that were restored with 15° metallic wedges cemented in place. We applied a varus moment and an axial load and monitored relative motion between implant and bone. Specimen-specific 3-D finite element models were constructed from CT scans and radiographs to examine bone stress in the proximal tibia. Implants with a wedge but no stem had greater motion than the previous control with no stem or wedge. Use of a modular stem with a wedge maintained the same level of motion as the primary case, suggesting that a stem is preferable when a wedge is utilized. The computational models confirmed this conclusion with a 30% reduction in bone stress compared to 17% in the primary case without a wedge. The wedge carried more axial load compared to the primary implant due to its support on stiff metaphyseal bone.

Tibial Post Wear in Posterior-stabilized Knee Replacements is Design-dependent

Bridgette D. Furman BS, Joseph Lipman MS, Mordechai Kligman MD, Timothy M. Wright PhD, Steven B. Haas MD Polyethylene tibial post wear in posterior-stabilized knee designs is a major problem. The Insall-Burstein II (IB PS II) reportedly has severe anterior wear of the post in retrieved implants. We hypothesized the more anterior placement in the IB PS II would be reflected in greater wear at the anterior face than the IB PS I. We examined 234 retrieved inserts using subjective scales to grade post damage and wear. Of the IB PS II inserts, 38% demonstrated severe wear compared with only 25% of IB PS I inserts. The most prevalent damage location for the IB PS II was the anterior face, whereas the IB PS I sustained wear mainly on the medial face. While the IB PS post was not designed to constrain posterior femoral displacement, our observations confirm contact in hyperextension or other paradoxic anterior tibial translation is common and design-dependent. Minimizing wear and damage through proper post placement and changes in implant design to anticipate contact on the anterior post should be considered for future posterior stabilized knee replacements. These changes cannot occur in isolation, however, because changes in post placement and design also depend on their relation to the shape and location of the tibial bearing surfaces.

To Resurface or Not to Resurface the Patella in Total Knee Arthroplasty

Naeder Helmy MD, Carolyn Anglin PhD, Nelson V. Greidanus MD, FRCS (C), Bassam A. Masri MD, FRCS (C) The management of the patellar articular surface at the time of primary total knee arthroplasty (TKA) is controversial. We used expected-value decision analysis to determine whether the patella should be resurfaced in TKA, and also whether secondary resurfacing on an unresurfaced patella is worthwhile. Outcome probabilities and utility values were derived from randomized controlled trials only. A decision tree was constructed and fold-back analysis was performed to ascertain the best treatment path. Sensitivity analyses were performed to determine the effect on decision-making of varying outcome probabilities and utilities. Our model showed patellar resurfacing is the best management strategy for the patella at the time of primary TKA. This decision is robust to changes in the specific data: the best path would remain the same as long as the incidence of persistent anterior knee pain (AKP) with resurfacing remains less than 29% (current mean, 12%) or the incidence of AKP after nonresurfacing falls below 12% (current mean, 26%). Delayed (ie, secondary) patellar resurfacing for ongoing patellar pain provides inferior results for the majority of patients.,[object Object]

Patient-reported Outcome Correlates With Knee Function After a Single-design Mobile-bearing TKA

Jean-Noel Argenson MD, Sebastien Parratte MD, Abdullah Ashour MD, Richard D. Komistek PhD, Giles R. Scuderi MD [object Object],[object Object]

Predicting Patellar Failure After Total Knee Arthroplasty

John B. Meding MD, Mark D. Fish DO, Michael E. Berend MD, Merrill A. Ritter MD, E. Michael Keating MD [object Object],[object Object]

Anthropomorphic Differences Between the Distal Femora of Men and Women

Jess H. Lonner MD, Jeff G. Jasko MS, Beverly S. Thomas RN There is debate about whether distinct designs of femoral components for men and women are needed based on morphologic and size differences between genders. We asked whether anthropomorphic differences exist between the distal femoral dimensions in women and men. We measured the distal femora of 100 women and 100 men intraoperatively after preparation for prosthetic implantation. The measured dimensions included the anteroposterior height from the posterior edge of the medial femoral condyle to the flush anterior cut, the mediolateral width at the transepicondylar axis, the anterior and posterior edges of the anterior chamfer, and the medial and lateral trochlear flanges. These measurements were compared between genders using independent-samples t test. The aspect ratio (a measure of the shape of the distal femur), the ratio between the anteroposterior and mediolateral dimensions, was calculated for men and women to determine whether there is a shape difference between genders. The mean aspect ratio was larger for women than for men (0.84 [range, 0.57–1.03] versus 0.81 [range, 0.066–1.34], respectively). The standard deviation and range of each measurement of size and morphology suggest variability not only between genders but also within genders. Whether the aspect ratios and variations will reflect clinically important differences in outcomes after TKA with available prostheses will require additional study.

Isolated All-polyethylene Patellar Revisions for Metal-backed Patellar Failure

Ryan M. Garcia MD, Matthew J. Kraay MS, MD, Victor M. Goldberg MD The outcome of isolated patellar component revisions after metal-backed patellar failure is variable with satisfactory results reported from 78% to 100%. To supplement information in the literature we determined the failure rate and the functional outcome based on the Knee Society clinical and roentgenographic evaluation systems of isolated patellar component revisions after metal-backed patellar component failure. We retrospectively reviewed 27 patients with 28 isolated patellar component revisions for metal-backed patellar component failure performed between 1988 and 2005. Twenty-five knees in 24 patients were available for review with a minimum followup of 24 months (mean, 90 months; range, 24–210 months). All knees were revised with a cemented all-polyethylene patellar component and all tibial polyethylene components were routinely exchanged. One failure (4%) occurred 122.6 months after the isolated patellar component revision secondary to femoral and tibial component loosening. The average Knee Society knee score improved from 73 to 89 points, whereas the average Knee Society function score improved from 56 to 65. Our data confirm those in the literature suggesting a successful outcome can be achieved with an isolated patellar component revision for metal-backed patellar component failure.,[object Object]

In-hospital Complications and Mortality of Unilateral, Bilateral, and Revision TKA: Based on an estimate of 4,159,661 Discharges

Stavros G. Memtsoudis MD, PhD, Alejandro González Della Valle MD, Melanie C. Besculides DrPH, MPH, Licia Gaber BA, Thomas P. Sculco MD Patients undergoing bilateral total knee arthroplasty (BTKA) may have higher complication rates and mortality than those undergoing a unilateral procedure (UTKA). To evaluate this hypothesis, we analyzed nationally representative data collected for the National Hospital Discharge Survey on discharges after BTKA, UTKA, and revision TKA (RTKA) between 1990 and 2004. The demographics, comorbidities, in-hospital stay, complications, and mortality of each procedure were compared. An estimate of 4,159,661 discharges (153,259 BTKAs; 3,672,247 UTKAs; 334,155 RTKAs) were included. Patients undergoing BTKA were younger (1.5 years) and had a lower prevalence of comorbidities for hypertension (versus UTKA), diabetes, pulmonary disease, and coronary artery disease (versus UTKA and RTKA). The length of hospitalization was 5.8 days for BTKA, 5.3 for UTKA, and 5.4 for RTKA. Despite similar length of hospitalization, the prevalence of procedure-related complications was higher for BTKA (12.2%) compared with UTKA (8.2%) and RTKA (8.7%). In-hospital mortality was highest for patients undergoing BTKA (BTKA, 0.5%; UTKA, 0.3%; RTKA, 0.3%). Patients undergoing BTKA had a 1.6 times higher rate of procedure-related complications and mortality compared with those undergoing UTKA. Outcomes for patients undergoing RTKA for most variables were similar to those for UTKA. BTKA, advanced age, and male gender were independent risk factors for complications and mortality after TKA.,[object Object]

The Impact of Gender, Age, and Preoperative Pain Severity on Pain After TKA

Jasvinder A. Singh MBBS, MPH, Sherine Gabriel MD, MSc, David Lewallen MD Do gender and age affect knee arthroplasty outcomes? In a cohort of patients who underwent primary or revision TKA between 1996 and 2004 and responded to a followup questionnaire 2 and 5 years after arthroplasty, we investigated the impact of gender and age on the prevalence of moderate or severe post-TKA knee pain (primary TKA: 2 years, 5290; 5 years, 2602; revision TKA: 2 years, 1109; 5 years, 505). Moderate-severe pain was higher in women than men after primary TKA at 2 and 5 years (9% versus 6.6% and 7.9% versus 6.5%) and post-revision TKA at 2 and 5 years (28.6% versus 22% and 28.9% versus 18.3%). More women compared to men and fewer patients between 61 and 70 years (versus patients ≤ 60) had moderate-severe pain 2 years after primary TKA adjusting for gender, age, and preoperative pain severity. In the post-revision TKA group, the odds of moderate-severe pain were lower in patients older than 80 years (versus those ≤ 60) at 2 years and higher in patients with moderate-severe preoperative pain at 2 and 5 years postoperatively, after adjustment for gender, age, and preoperative pain severity. We conclude female gender, younger age, and worse preoperative pain predict greater risk of moderate-severe pain postoperatively in patients with primary and revision TKA.,[object Object]

Navigation Did Not Improve the Precision of Minimally Invasive Knee Arthroplasty

Peter M. Bonutti MD, Daniel A. Dethmers MD, Mike S. McGrath MD, Slif D. Ulrich MD, Michael A. Mont MD Potential advantages of minimally invasive total knee arthroplasty (TKA) include decreased pain, faster recovery, and increased quadriceps muscle strength. Computer-assisted navigation has been associated with more accurate component alignment. We evaluated two groups of 50 patients who had minimally invasive TKAs performed with and without navigation by two surgeons. A comparison of 50 previous TKAs by each of the two surgeons showed similar results. The mean operative times for the navigation and nonnavigation groups were 112 minutes (range, 63–297 minutes) and 54 minutes (range, 35–86 minutes), respectively. The mean estimated blood losses, mean Knee Society pain as well as functional scores and mean component alignments were similar. The number of knees that deviated by more than 3° from the normal anatomic axis was three and one in the navigated and nonnavigated groups, respectively. Complication rates were 6% and 4% in the navigated and nonnavigated groups, respectively. Our data demonstrate no distinct advantage of navigation when combined with a minimally invasive approach.,[object Object]

Lack of Axial Rotation in Mobile-bearing Knee Designs

Ray C. Wasielewski MD, MS, Richard D. Komistek PhD, Sumesh M. Zingde MS, Kate C. Sheridan BS, Mohamed R. Mahfouz PhD It has often been assumed rotational kinematics are improved with mobile-bearing TKA designs as the terms mobile-bearing and rotating platform imply. We tested this assumption by assessing the in vivo axial rotation magnitudes and patterns of 527 knees implanted with 12 different mobile-bearing TKA designs. Implants were grouped and compared by type—posterior stabilized (PS), posterior cruciate retaining (PCR), and posterior cruciate sacrificing (PCS)—and by specific design. We hypothesized all three mobile-bearing types (PS, PCR, and PCS) would achieve greater than 10° average axial rotation and we would find no differences in axial rotation between types. Only 14% of PS knees, 3% of PCS knees, and 17% of PCR knees attained greater than 10° axial rotation when measured from 0° to 90°. The percentage of PCS knees with greater than 10° axial rotation was less compared with the other two groups. Axial rotation averaged 4.3°, 2.5°, and 3.8° for the PS, PCS, and PCR knees, respectively. Incidences of reverse rotation were observed in 17% of PS knees, 32% of PCS knees, and 28% of PCR knees. Compared with the PCS group, the PS group achieved greater average axial rotation and had a lower percentage of knees displaying incidences of reverse rotation. The data refuted the hypotheses.

Long-term Results With a Lateral Unicondylar Replacement

Jean-Noël A. Argenson MD, Sebastien Parratte MD, Antoine Bertani MD, Xavier Flecher MD, Jean-Manuel Aubaniac MD While the literature suggests lateral unicondylar knee arthroplasty (UKA) improves function in the short- and medium-term, it is less clear on longer-term function. We asked (1) whether lateral UKA improved longer-term Knee Society scores and return to previous activity level); (2) whether there were any concerning longer-term radiographic findings (the Knee Society roentgenographic evaluation and scoring system); and (3) whether lateral UKA was durable as measured by survivorship to revision at 10 and 16 years. We retrospectively reviewed 39 patients with 40 lateral cemented metal-backed UKA. The patients had a mean age of 61 years at surgery. The etiologies were primary osteoarthritis in 24 knees, posttraumatic in 12 cases, and osteonecrosis in four cases. We performed clinical and radiographic evaluations at a minimum followup of 3 years (mean, 12.6 years; range, 3–23 years). Prostheses survivorship was 92% at 10 years and 84% at 16 years. Despite the limited number of indications and technical considerations, our data suggest lateral UKA is a reasonable alternative for isolated lateral femorotibial compartment disease.,[object Object]

Does Patellar Eversion in Total Knee Arthroplasty Cause Patella Baja?

Vineet Sharma MD, Panagiotis G. Tsailas MD, Aditya V. Maheshwari MD, Amar S. Ranawat MD, Chitranjan S. Ranawat MD Several proponents of minimally invasive surgery-total knee arthroplasty (MIS-TKA) have suggested patellar eversion during a standard exposure of the knee may cause shortening of the patellar tendon and poorer outcomes secondary to acquired patella baja. To explore this suggestion, we retrospectively reviewed 135 consecutive TKAs in 110 patients to ascertain the effect of TKA on the postoperative Insall-Salvati ratio. All surgeries were performed using standard TKA techniques with a midline incision, medial parapatellar arthrotomy, partial excision of the fat pad, and routine eversion of the patella. One patient developed a postoperative patella baja, defined as an Insall-Salvati ratio of less than 0.8. The Knee Society score for knee and function in this patient was 75 and 70, respectively. Five additional patients had a decrease in Insall-Salvati ratio by 10% or more but without patella baja. Mean Knee Society score for knee and function in these five patients was 94 (range, 73–99) and 96 (range, 90–100), respectively, as compared with 93 (range, 37–99) and 94 (range, 40–100) in the remaining 104 patients. Our data suggest the incidence of patella baja is low after TKA despite routine patellar eversion. Furthermore, a 10% or more decrease in the Insall-Salvati ratio without patella baja was not associated with a worse clinical outcome.,[object Object]

The Mark Coventry Award: In Vivo Knee Forces During Recreation and Exercise After Knee Arthroplasty

Darryl D. D’Lima MD, PhD, Nikolai Steklov BS, Shantanu Patil MD, Clifford W. Colwell MD Knee forces directly affect arthroplasty component survivorship, wear of articular bearing surfaces, and integrity of the bone-implant interface. It is not known which activities generate forces within a range that is physiologically desirable but not high enough to jeopardize the survivorship of the prosthetic components. We implanted three patients with an instrumented tibial prosthesis and measured knee forces and moments in vivo during exercise and recreational activities. As expected, stationary bicycling generated low tibial forces, whereas jogging and tennis generated high peak forces. On the other hand, the golf swing generated unexpectedly high forces, especially in the leading knee. Exercise on the elliptical trainer generated lower forces than jogging but not lower than treadmill walking. These novel data allow for a more scientific approach to recommending activities after TKA. In addition, these data can be used to develop clinically relevant structural and tribologic testing, which may result in activity-specific knee designs such as a knee design more tolerant of golfing by optimizing the conflicting needs of increased rotational laxity and conformity.