Total knee replacement in juvenile chronic arthritis.
Twelve patients with juvenile chronic arthritis (JCA) underwent 18 primary knee replacements during 1975-81. Eleven patients were followed for an average of six (3-9) years. Mean age at operation was 25 (18-32) years. Indications for surgery were pain and limitation of motion. Four knee joints were revised, one of them three times, due to malposition and/or mechanical loosening of the prosthetic components. At follow-up, all patients except one were satisfied with the knee replacement. All patients except one were ambulatory. Functional capacity was improved in 8 patients. The arc of motion was increased by a mean of 17 degrees. The radiographs at follow-up showed an average hip-knee-ankle (HKA) angle of 182 (173-193) degrees. In eight knee joints the tibial and/or femoral component showed a radiolucent zone at the bone-cement interface exceeding 2 mm and in four of these joints there were signs of prosthetic migration. To aid in the choice of an appropriate prosthesis for the juvenile arthritic joint, standardized measurements of the radiographic dimensions of the knee joint were made. Because of the high rate of revisions during the short observation period and the potential failure rate indicated by the radiographs at follow-up, we maintain a cautious attitude towards knee replacement in patients with JCA.