TOTAL KNEE ARTHROPLASTY IN PATELLECTOMIZED PATIENTS

Thirty-two total knee arthroplasties (TKAs) in patellectomized patient s were evaluated with recent clinical and radiographic examinations. E ighteen patients had a primary TKA with a mean follow-up period of 49 months, and 14 patients had a revision TKA with a mean follow-up perio d of 36 months. A control group of 13 TKA patients with intact patella e were randomly generated but matched for age, sex, follow-up data, di agnosis, and prosthesis. Posterior cruciate ligament-retaining types o f prostheses were used in the primary knees, while the revision knees underwent arthroplasties with the more constrained, posterior cruciate ligament-substituting prostheses. All knees were evaluated based on t he Knee Society's clinical and radiographic scoring system. In additio n, 18 patients (9 primary, 9 revision) underwent isokinetic dynamomete r testing for quantitation of peak quadriceps and hamstring torque. Th e knee score, indicative of pain relief, averaged 82.5 in the primary group (16 good/excellent, 1 fair, 1 poor), 86.5 in the revision group (12 good/excellent, 1 fair, 1 poor), and 93.9 in the control group (13 /13 excellent). The function-score averaged -59.7 in the primary group (6 good/excellent, 6 fair, 6 poor), 60.0 in the revision group (5 goo d/excellent, 2 fair, 7 poor), and 80.9 iii the control group (12 good/ excellent, 1 fair). The lower function scores predominantly reflected the patients' difficulty in independently climbing or descending stair s. This was also reflected in their higher flexion to extension peak t orque ratios. There was one failure in the primary group requiring a r evision and one failure in the revision group requiring a knee fusion. There was no radiographic evidence of impending failure in any of the remaining knees. No clinical or radiographic differences were found b etween the patients with osteoarthritis or rheumatoid arthritis. Altho ugh the knee and function scores were lower in the patellectomized pat ients, the overall results were generally satisfactory without a high incidence of failures. Satisfactory results were obtained in the prima ry TKAs using the minimally constrained prostheses when the posterior cruciate ligament Was intact. Revision TKAs, in which the posterior cr uciate ligament was absent, also demonstrated satisfactory results wit h the more constrained, posterior cruciate ligament-substituting prost heses.