Clinical Orthopaedics and Related Research ®

A Publication of The Association of Bone and Joint Surgeons ®

Published in
Clinical Orthopaedics and Related Research®
Volume 468 | Issue 1 | Jan, 2010
Articles

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.

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 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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

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]

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]

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]

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]

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]

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]

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]

Fenestrated Cannulae with Outflow Reduces Fluid Gain in Shoulder Arthroscopy

Hasan M. Syed MD, Seth B. Gillham BA, Christopher M. Jobe MD, Wesley P. Phipatanakul MD, Montri D. Wongworawat MD Soft tissue fluid retention is a common problem after arthroscopy, with as much as 2% of patients having complications develop. A fenestrated outflow cannula has been introduced to reduce interstitial swelling. We tested the ability of this outflow cannula design to reduce fluid weight gain. We enrolled 28 patients undergoing shoulder arthroscopy and randomized them into two groups using fenestrated outflow versus conventional cannulae. The conventional group had greater weight gain as a function of the procedure duration than the fenestrated outflow group (slope = 0.542 ± 1.160 kg/hour versus 0.0144 ± 0.932 kg/hour). The conventional group also had greater weight gain as a function of fluid volume than the fenestrated outflow group (slope = 0.022 ± 0.038 kg/L versus 0.002 ± 0.341 kg/L). Compared with conventional nonoutflow cannulae, fenestrated outflow cannulae with negative pressure reduced weight gain associated with longer arthroscopic surgeries and increased arthroscopic fluid volume.,[object Object]

High Fusion Rates with Circular Plate Fixation for Four-corner Arthrodesis of the Wrist

Ben Bedford MD, S. Steven Yang MD, MPH

Scaphoid excision and four-corner fusion is commonly performed to reconstruct advanced scapholunate collapse and scaphoid nonunion with collapse. Metallic plates were introduced for achieving fixation of the four carpal bones. Although the developer reported high rates of fusion, several other early reports of circular plate fixation suggest higher complication rates and inferior outcomes compared with traditional fixation techniques.

Accuracy of Computer Navigation for Acetabular Component Placement in THA

James A. Ryan MD, Amir A. Jamali MD, William L. Bargar MD The accuracy and precision of any computer-aided surgical device is critical to its utility. We asked the following question: how accurate and precise are the values measured by an imageless computer navigation system as compared with those measured using postoperative CT scans? Twenty-five patients (26 hips) underwent primary THA using an imageless computer navigation system for placement of the acetabular component. Inclination and anteversion were measured in the operative coordinate system as defined by Murray. Accuracy, precision, and bias were computed, and Bland-Altman analysis was used to assess levels of agreement. The accuracy (mean ± standard deviation of the absolute difference between computer-assisted navigation and CT) was 1.8° ± 1.2° for inclination and 2.0° ± 2.0° for anteversion. Precision was 3.4° for inclination and 5.5° for anteversion. Bias was 0.52° for inclination and 0.35° for anteversion. Limits of agreement were 4.26° for inclination and 5.58° for anteversion. An imageless computer navigation system can precisely determine acetabular cup position.

Incidence of Postthrombotic Syndrome in Patients Undergoing Primary Total Knee Arthroplasty for Osteoarthritis

Christopher M. McAndrew MD, Steven J. Fitzgerald MD, Matthew J. Kraay MD, Victor M. Goldberg MD Postthrombotic syndrome (PTS) is characterized by edema, venous ectasia, hyperpigmentation, varicose veins, venous ulceration, and pain with calf compression after deep venous thrombosis (DVT). We determined the incidence of PTS after DVT diagnosed on screening ultrasound in patients undergoing primary total knee arthroplasty (TKA) for osteoarthritis (OA). We retrospectively reviewed the records of 1406 patients who underwent primary TKA for osteoarthritis and compared the incidence of PTS in patients without and with DVT. All patients had postoperative screening ultrasound. From these 1406 patients we identified 66 (4.7%) who had DVT, 50 of whom had a minimum of 1 year followup (mean, 4.97 years; range, 1.00–7.53 years). PTS was diagnosed if any two of six signs were documented in the medical record. Three of 50 patients with DVT (6%) had signs consistent with PTS; two of these three had a DVT proximal to the soleal arch. Seven (8%) of 88 patients randomly chosen for primary TKA because of OA with similar mean age and gender, but without DVT, had signs of PTS. PTS does not seem to be a major sequela of DVT in patients undergoing primary TKA for OA.,[object Object]

Arthroscopic Treatment of Femoroacetabular Impingement of the Hip: A New Technique to Access the Joint

Monika Horisberger MD, Alexander Brunner MD, Richard F. Herzog MD Femoroacetabular impingement has been established as an important cause of groin pain and limitation of range of motion in young, active patients and a possible cause for early osteoarthritis of the hip. Open surgery is a well-recognized approach for treatment and probably the standard for most surgeons, but recent reports regarding arthroscopic treatment procedures suggest comparable results. We present a technique that provides a way to securely penetrate the joint capsule and evaluate the clinical results of this technique in patients with femoroacetabular impingement. Between 2004 and 2007, we prospectively followed a cohort of 105 hips (88 patients; 60 males, 28 females) who underwent surgery for symptomatic cam or mixed femoroacetabular impingement. All patients were evaluated for the Nonarthritic Hip Score, clinical parameters, visual analog scale pain score, initial radiographic degenerative changes, and alpha angle. At a minimum followup of 1.3 years (average, 2.3 years; range, 1.3–4.1 years), all clinical outcome measures improved. The Nonarthritic Hip Score improved from 56.7 points (range, 15–92.5 points) to 84.6 points (range, 47.5–100 points). Nine patients (8.6%) underwent THA during followup. The outcome measures after arthroscopic therapy for femoroacetabular impingement seem comparable to those reported after open procedures.,[object Object]

Asymmetry in Quadriceps Rate of Force Development as a Functional Outcome Measure in TKA

Nicola A. Maffiuletti PhD, Mario Bizzini MSc, PT, Katharina Widler MSc, Urs Munzinger MD Quadriceps muscle strength is an important predictor of functional abilities in patients having TKA. However, because several daily activities are characterized by a limited time to generate force, it has been suggested that rate of force development (RFD) could better predict functional difficulties than maximal strength. We therefore hypothesized the side-to-side asymmetry would be larger for RFD than for maximal strength, and RFD asymmetry relates to subjective symptoms and/or functional daily living activities. We studied 31 subjects (17 women, 14 men) 6 ± 1 months after undergoing TKA for unilateral osteoarthritis. Symptoms and limitations during activities of daily living were quantified using the knee outcome survey-activities of daily living scale (KOS-ADLS). Quadriceps maximal strength and RFD at different times (50 to 200 ms from contraction onset) were quantified during unilateral maximal voluntary isometric actions. Side-to-side asymmetries (involved versus uninvolved side) were larger for RFD (approximately 36%) than for maximal strength (approximately 24%). Subjective knee function related to all RFD asymmetry variables, but not to maximal strength asymmetry. In addition to maximal strength, quadriceps RFD in the first 100 to 200 ms from contraction onset provides an alternative functional outcome measure for individuals undergoing TKA.

How Successful are Current Ankle Replacements?: A Systematic Review of the Literature

Nikolaos Gougoulias MD, PhD, Anil Khanna MD, Nicola Maffulli MD, PhD [object Object],[object Object]

Can Porous Tantalum Be Used to Achieve Ankle and Subtalar Arthrodesis?: A Pilot Study

Arno Frigg MD, Hugh Dougall MD, Steve Boyd PhD, Benno Nigg PhD A structural graft often is needed to fill gaps during reconstructive procedures of the ankle and hindfoot. Autograft, the current gold standard, is limited in availability and configuration and is associated with donor-site morbidity in as much as 48%, whereas the alternative allograft carries risks of disease transmission and collapse. Trabecular metal (tantalum), with a healing rate similar to that of autograft, high stability, and no donor-site morbidity, has been used in surgery of the hip, knee, and spine. However, its use has not been documented in foot and ankle surgery. We retrospectively reviewed nine patients with complex foot and ankle arthrodeses using a tantalum spacer. Minimum followup was 1.9 years (average, 2 years; range, 1.9–2.4 years). Bone ingrowth into the tantalum was analyzed with micro-CT in three of the nine patients. All arthrodeses were fused clinically and radiographically at the 1- and 2 year followups and no complications occurred. The American Orthopaedic Foot and Ankle Society score increased from 32 to 74. The micro-CT showed bony trabeculae growing onto the tantalum. Our data suggest tantalum may be used as a structural graft option for ankle and subtalar arthrodesis. All nine of our patients achieved fusion and had no complications. Using tantalum obviated the need for harvesting of the iliac spine.,[object Object]

Growth Diagrams for Grip Strength in Children

H. M. (Ties) Molenaar MSc, Ruud W. Selles PhD, J. Michiel Zuidam MSc, Sten P. Willemsen MSc, Henk J. Stam, Steven E. R. Hovius

Grip strength dynamometers often are used to assess hand function in children. The use of normative grip strength data at followup is difficult because of the influence of growth and neuromuscular maturation. As an alternative, infant welfare centers throughout the world use growth diagrams to observe normative growth. The aim of this study was to develop similar growth diagrams for grip strength in children. We measured the grip strength, hand dominance, gender, height, and weight of 225 children, 4 to 12 years old. We developed separate statistical models for both hands of boys and girls for drawing growth curves. Grip strength increased with age for both hands. For the whole group, the dominant hand produced higher grip strength than the nondominant hand and boys were stronger than girls. The grip strength of boys and girls differed between 2 and 19 N for the different age groups. Because grip strength measurements are accompanied by a rather large variance, the growth diagrams (presenting a continuum in grip strength) make it possible to better observe grip strength development with time corresponding to a more exact age. Depending on the accuracy needed, the use of one combined diagram could be considered.,[object Object]

Proximal Femur Allograft-prosthesis with Compression Plates and a Short Stem

D. Luis Muscolo MD, German L. Farfalli MD, Luis A. Aponte-Tinao MD, Miguel A. Ayerza MD Proximal femur allograft-prosthesis composites (APCs) performed with compression plates and a short stem theoretically could minimize the resorption or nonunion that reportedly occurs with long stems bypassing the diaphyseal osteotomy. To confirm this theoretical consideration, we retrospectively reviewed 34 patients with 38 proximal femoral APCs using a short-cemented femoral stem and compression plates for diaphyseal osteotomy fixation. In 26 patients, the plate fixation extended over at least half the femoral stem and in 12, it did not. We reinserted the abductor mechanism with two techniques: in 10 cases the host trochanter was reattached to the APC, and in 28 the host tendons were sutured to the tendinous insertion of the allograft. The overall survival of the entire series was 72% at 5 years and 69% at 10 years. Eleven of the 38 (29%) APCs were removed: three for infection, one for local recurrence of tumor, and seven for fractures. Trendelenburg gait occurred in four of 21 patients with direct tendon-to-tendon suture of the abductor mechanism and in three of six patients with trochanteric osteotomy. The overall APC survival rate was greater in patients in whom the allograft was adequately protected with internal fixation than in patients in whom it was not.,[object Object]

Argon Beam Coagulation as Adjuvant Treatment after Curettage of Aneurysmal Bone Cysts: A Preliminary Study

Judd E. Cummings MD, Richard A. Smith PhD, Robert K. Heck MD The optimal treatment of aneurysmal bone cysts remains an area of debate. Curettage, with or without adjuvant therapy, has been advocated for tumors in most locations. To evaluate argon beam coagulation as adjuvant therapy to curettage, we retrospectively analyzed the complication and recurrence rates in 40 consecutive patients with a diagnosis of aneurysmal bone cyst. For our analysis of recurrence, we excluded six of the 40 patients who were lost to followup or had less than 18 months followup; five patients treated with resection also were excluded. Of the remaining 29 patients, 17 were treated with curettage and argon beam coagulation and 12 were treated with curettage with or without phenol. None of the 17 patients treated with curettage and argon beam coagulation had a recurrence, whereas four patients treated without argon beam coagulation had recurrences. There were no differences between patients treated with or without argon beam coagulation regarding frequencies of intraoperative complications, neurovascular injury, or bone graft incorporation. Argon beam coagulation seems to offer favorable control rates when compared with curettage with or without phenol. No complications have been experienced thus far with its use.,[object Object]

Skeletally Mature Patients with Bilateral Distal Radius Fractures Have More Associated Injuries

Amirhesam Ehsan MD, Milan Stevanovic MD, PhD Bilateral distal radius fractures are rare injuries and only a handful of case reports exist. Understanding the demographic variables and associated injuries in patients with these fractures may improve awareness and treatment of concomitant injuries. We determined the differences in mode of trauma and associated injuries between skeletally mature and skeletally immature patients with bilateral distal radius fractures. We retrospectively reviewed the records of 93 patients with bilateral distal radius fractures. We compared demographic data, fracture patterns, mode of injury, treatment modality, and associated injuries for skeletally mature and immature patients. The mean age of all patients sustaining a bilateral injury was 22.5 years and 61 (71%) were male. Of the 51 (55%) skeletally immature patients, 37 (73%) were male, and 44 (86%) sustained a low-energy mechanism of injury. Of the 42 (45%) skeletally mature patients, 29 (69%) were male, and 37 (88%) sustained a high-energy mechanism of injury. Skeletally mature patients had a 38% rate of associated injuries versus 4% found in skeletally immature patients. Skeletally mature patients sustained bilateral distal radius fractures through higher-energy mechanisms and presented with more frequent associated injuries compared with the skeletally immature patients.

Supination-External Rotation Ankle Fractures: Stability a Key Issue

Nikolaos Gougoulias MD, PhD, Anil Khanna MRCS, MS(Ortho), Anthony Sakellariou FRCS(Orth), Nicola Maffulli MD, MS, PhD, FRCS(Orth) Stability is a key issue in treating supination-external rotation ankle fractures, but we do not know how it affects functional outcome and subsequent development of radiographic osteoarthritis. With a systematic literature review, we identified 11 clinical studies (Level IV evidence) published in peer-reviewed journals reporting on at least 10 ankles. Followup was at least 1 year. Two authors independently scored the quality of the studies using the modified Coleman Methodology Score; the mean score was 58 of 100, with substantial agreement between the two examiners. Four studies used a general health assessment questionnaire. Several literature limitations (debatable fracture stability criteria, few cohort studies with heterogeneous methodology, small patient numbers and limited followup in some studies) do not allow definitive conclusions. Of 213 stable fractures treated nonoperatively, 2.8% of ankles had radiographic osteoarthritis develop (18 years’ mean followup) and 84% were free of symptoms. The incidence of radiographic osteoarthritis in 420 unstable fractures treated operatively was 20.9% at 5.5 years versus 65.5% at 6.8 years in 137 ankles treated nonoperatively. The complication rate in 355 operatively treated fractures was 10.4%. A medial malleolus fracture, female gender, older age, higher American Society of Anesthesiologists grade, smoking, and lower educational level negatively influenced general health outcome, physical function, and pain.,[object Object]

Is Humeral Segmental Defect Replacement Device A Stronger Construct than Locked IM Nailing?

Robert Heck MD, Ruxandra Marinescu PhD, Haden Janda BS, Seth Cooper BS, Jason Schroeder PhD Intramedullary (IM) nailing is currently the most common method for treating patients with impending pathologic humeral fractures; however, this treatment is associated with known complications primarily owing to violation of the rotator cuff during insertion. A better option is needed. To determine if a humeral segmental replacement prosthesis would provide a stronger construct compared with an IM nail in this setting, we compared the mechanical properties of these two devices in a cadaver model simulating an impending pathologic fracture. In each of nine matched pairs of fresh human humeri one was randomly selected to undergo a 50% lateral middiaphyseal defect simulating an impending pathologic fracture and subsequent fixation with an IM nail and bone cement. The contralateral humerus underwent fixation using a humeral segmental defect prosthesis. We determined T-scores using DEXA. Each specimen subsequently was tested in torsion to failure. Peak torque and peak rotation at failure were greater for the prosthesis specimens whereas torsional stiffness was greater for the IM nail specimens. We found a linear relationship between peak torque and T-score for each device with the slopes of the lines suggesting the construct with the prosthesis can withstand greater forces than the IM nail and the differences between devices were greater in weaker bones.

Luggage Tag Technique of Anatomic Fixation of Displaced Acromioclavicular Joint Separations

Keith Baldwin MD, MPH, MSPT, Surena Namdari MD, MSc, Jaron R. Andersen MD, Brian Lee BS, John M. Itamura MD, G. Russell Huffman MD, MPH Acromioclavicular joint dislocations are common injuries in active individuals. Most of these injuries may be treated nonoperatively. However, many techniques have been described when surgical management is warranted. A recent biomechanical study favors anatomic reconstruction of the conoid and trapezoid ligaments and the acromioclavicular joint capsule, as opposed to the traditional technique of excision of the lateral end of clavicle and transfer of the coracoacromial ligament to the intramedullary canal of the distal clavicle. We present a modification of the anatomic fixation technique using a luggage tag method, which places a graft under the base of the coracoid. This procedure has been associated with few redisplacements of the distal clavicle, reliable pain relief, and minimal postoperative morbidity. We found the luggage tag technique provides anatomic fixation of the distal clavicle and restoration of coronal and sagittal plane stability to the injured acromioclavicular joint. This procedure should reduce the possibility of coracoid fracture and decreases the risk of hardware complications associated with reconstruction techniques that violate the base of the coracoid process.,[object Object]

Q-angle and J-sign: Indicative of Maltracking Subgroups in Patellofemoral Pain

Frances T. Sheehan PhD, Aditya Derasari MD, Kenneth M. Fine MD, Timothy J. Brindle PhD, Katharine E. Alter MD Mechanical factors related to patellofemoral pain syndrome and maltracking are poorly understood. Clinically, the Q-angle, J-sign, and lateral hypermobility commonly are used to evaluate patellar maltracking. However, these measures have yet to be correlated to specific three-dimensional patellofemoral displacements and rotations. Thus, we tested the hypotheses that increased Q-angle, lateral hypermobility, and J-sign correlate with three-dimensional patellofemoral displacements and rotations. We also determined whether multiple maltracking patterns can be discriminated, based on patellofemoral displacements and rotations. Three-dimensional patellofemoral motion data were acquired during active extension-flexion using dynamic MRI in 30 knees diagnosed with patellofemoral pain and at least one clinical sign of patellar maltracking (Q-angle, lateral hypermobility, or J-sign) and in 37 asymptomatic knees. Although the Q-angle is assumed to indicate lateral patellar subluxation, our data supported a correlation between the Q-angle and medial, not lateral, patellar displacement. We identified two distinct maltracking groups based on patellofemoral lateral-medial displacement, but the same groups could not be discriminated based on standard clinical measures (eg, Q-angle, lateral hypermobility, and J-sign). A more precise definition of abnormal three-dimensional patellofemoral motion, including identifying subgroups in the patellofemoral pain population, may allow more targeted and effective treatments.

Regional Variations of Bone Quantity and Quality Impact Femoral Head Collapse

Christian J. Zaino BA, Alex Leali MD, Joseph F. Fetto MD Osteonecrosis (ON) of the femoral head causes the bone to deteriorate, buckle, and collapse. As the vasculature is reportedly uniform in the femoral head, one would expect uniform susceptibility to ON; however, collapse typically occurs in the anterior region. We asked whether regional variations in bone quantity and/or quality could explain the bone’s anterior susceptibility despite uniform vascularity. We examined seven femoral heads resected for primary osteoarthritis and three removed after femoral neck fracture. Each was cut into 4-mm-thick, 1.5 cm × 1.5-cm bone squares, processed for light microscopy, and sectioned twice. One section was stained with Gomori’s trichrome and assessed by a computer-assisted microscope, which calculated trabecular area, a measure of bone quantity. The other was stained with hematoxylin and eosin and assessed by light microscopy to identify trabecular microfractures, a measure of bone quality. Bone quantity and quality were reduced in the fracture group as a whole; bone quantity was uniform in each femoral head, but the quality was reduced in the anterior portion. The quality was further reduced in the superior region of arthritic bone and in the lateral-inferior regions of the fractured bones. Our findings suggest the anterior susceptibility is the result of bone loading and, as such, reinforcement of the femoral head in ON should focus on the anterior hemisphere.

Case Report: Osteoid Osteoma of the C2 Pedicle: Surgical Technique Using a Navigation System

Hideki Nagashima MD, Takako Nishi MD, Koji Yamane MD, Atsushi Tanida MD An osteoid osteoma of the cervical spinal pedicle is rare and carries a high surgical risk because of the close anatomic relationship to the spinal cord, nerve root, and vertebral artery. We report the case of a 12-year-old girl with an osteoid osteoma of the C2 pedicle. Computed tomograms showed an oval nidus and marked sclerosis around this lesion at the right C2 pedicle. There also was expansion of the medial and inferior cortical bone of the C2 pedicle. After failure of nonoperative treatment, we planned surgery. Owing to concerns regarding thermal damage to the spinal cord, nerve root, and/or vertebral artery using computed tomography (CT)-guided radiofrequency ablation, we curetted the nidus using a navigation system. Twenty-eight months after surgery, her pain was relieved with no limitation of cervical movement and there has been no evidence of recurrence. Navigation allowed safe curettage of the nidus through a small hole while maintaining spinal stability.

Case Reports: A Stener-like Lesion of the Medial Collateral Ligament of the Knee

Kristoff Corten MD, Christian Hoser MD, Christian Fink, Johan Bellemans MD, PhD When the superficial fibers of the medial collateral ligament of the knee are torn without tearing of the deep fibers, the anterior superficial fibers may displace over the pes anserinus tendons, so that healing back to the tibial insertion site may be jeopardized. As only the anterior superficial and not the posterior superficial or deep fibers are disrupted, the knee will not have increased valgus laxity in extension whereas there is not a firm end point in 30° flexion. The clinical findings could be confused with those of a Grade 2 medial collateral ligament sprain that generally is not associated with displacement of the anterior fibers over the pes anserinus tendons. We describe the diagnostic findings confirmed with surgical exploration of two Stener-like disruptions of the medial collateral ligament of the knee.
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