Total knee arthroplasty in patellectomized patients

Thirty-two total knee arthroplasties (TKAs) in patellectomized patients were evaluated with recent clinical and radiographic examinations. Eighteen 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 period of 36 months. A control group of 13 TKA patients with intact patellae were randomly generated but matched for age, sex, follow-up data, diagnosis, and prosthesis. Posterior cruciate ligament-retaining types of 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 the Knee Society's clinical and radiographic scoring system. In addition, 18 patients (9 primary, 9 revision) underwent isokinetic dynamometer testing for quantitation of peak quadriceps and hamstring torque. The 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 good/excellent, 2 fair, 7 poor), and 80.9 in the control group (12 good/excellent, 1 fair). The lower function scores predominantly reflected the patients' difficulty in independently climbing or descending stairs. This was also reflected in their higher flexion to extension peak torque ratios. There was one failure in the primary group requiring a revision 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 between the patients with osteoarthritis or rheumatoid arthritis. Although the knee and function scores were lower in the patellectomized patients, the overall results were generally satisfactory without a high incidence of failures. Satisfactory results were obtained in the primary TKAs using the minimally constrained prostheses when the posterior cruciate ligament was intact. Revision TKAs, in which the posterior cruciate ligament was absent, also demonstrated satisfactory results with the more constrained, posterior cruciate ligament-substituting prostheses.