Effect of Polyethylene Crosslinking and Bearing Design on Wear of Unicompartmental Arthroplasty.

Wear and polyethylene damage continue to be important factors affecting outcomes of unicompartmental knee arthroplasty. We compared two design rationales for unicompartmental arthroplasty: fully congruent mobile bearings; or moderately conforming fixed bearings using experimental and computational wear simulation. Experimental wear rates were 3.89 (±0.12) mg/million cycles for the highly crosslinked Triathlon PKR fixed bearing compared to 18.35 (±0.19) mg/million cycles for the low crosslinked Oxford mobile bearing. Finite element analysis was used to calculate the effect of crosslinking and backside wear. Increase in polyethylene crosslinking reduced wear by 68% while backside wear comprised 46% of the total wear in the mobile bearing. Increasing conformity may not be the sole predictor of wear performance and highly crosslinked fixed-bearing polyethylene insert can also provide high wear performance.

Innovations in knee arthroplasty: three-dimensional modeling and analytical technology (SOMA).

The development of three-dimensional (3D) knee models and analytical tools from large databases of computerized tomographic data linked to patient demographics has led to the development of a fuller understanding of the amount of variation in the anatomy and morphology of the human knee and how this relates to clinical applications. In this study, we have aimed to review the spectrum of clinical applications of three-dimensional modeling, which includes osteotomies and knee arthroplasties. More specifically, three-dimensional modeling has been used for: the assessment of tibial and femoral morphometry, the potential development of novel instrumentation for femoral resection, the evaluation of femoral condylar anthropometry, correlating mechanical and anatomical alignment, the assessment of the relationship of joint line and flexion, the extension and mechanical axis of the knee, and the evaluation of the relationship between medial tibial tubercle to the posterior aspect of the tibia. Three-dimensional modeling and analytical technology may provide insights into anthropometric variations in the knee and may assist in the future development of more patient specific instrumentation, implant positioning, and implant designs. It is hoped that such advances could improve patient satisfaction and long-term implant survivorship.

Two- to 12-year evaluation of cementless Buechel-Pappas total hip arthroplasty.

A unique, straight-stemmed, proximally porous-coated, modular hip arthroplasty system, coated with thin-film (5- to 9-microm), titanium-nitride ceramic, was used clinically in 130 hip arthroplasties in 117 patients who were followed over a 2- to 12-year interval (mean, 6.45 years). Harris Hip Scores demonstrated 82.3% excellent, 15.4% good, 2.3% fair, and 0% poor results. Thigh pain that limited activities of daily living was seen in 0.8% (1 of 130) hips. Kaplan-Meier survival estimates using an endpoint of revision of any component for any reason demonstrated an overall survival of 95.5% during the 12-year interval. Cementless fixation survivorship of the acetabular and femoral components was 98.5% during the 12-year interval.

Primary exchange revision arthroplasty for infected total knee replacement: a long-term study.

Infected knee replacement is a serious complication that requires significant hospital-based resources for successful management. A successful primary exchange revision technique offers decreased morbidity for the patient by eliminating a second major operation and associated hospitalization, which in turn substantially reduces the cost associated with this dreaded condition. Twenty-two consecutive infected primary total knee arthroplasties in 22 patients were treated with primary exchange revision arthroplasties using antibiotic-impregnated cement. The surgical technique consisted of excision of draining sinuses, complete synovectomy, removal of granulation tissue, and debulking of the extensor mechanism. Postoperative treatment consisted of 4 to 6 weeks of parenterally administered antibiotics and 6 to 12 months of orally administered antibiotics. Both gram-positive and gram-negative organisms were treated. At an average follow-up of 10.2 years (range, 1.4 to 19.6 years), 90.9% were free of recurrent infection. Knee scores averaged 79.5, with 85.7% good or excellent results. The physiological classification of the host appeared to influence the outcome of revision. All patients in class A or B (20 knees) had successful eradication of their primary infection after 1-stage revision, whereas the only failure in the group was a physiological class C patient, who eventually expired from ongoing end-organ liver failure. These results compare most favorably with those of delayed-exchange revision arthroplasty while providing a more cost-effective management program.