Results of geometric arthroplasty for rheumatoid and osteoarthritis of the knee.

The Geometric Total Knee Arthroplasty was one of the earliest unconstrained knee arthroplasties available for the replacement of knees severely affected by destructive arthritis. This paper presents the results of Geometric knee arthroplasty performed by surgeons of the Alfred Hospital, Melbourne, during the years 1973 to 1977, this being the initial five years experience with this procedure. One hundred and fifty arthroplasty operations were performed in 106 patients, 78 for osteoarthritis and 72 for rheumatoid arthritis, with the average time from operation to review being four years. The Geometric arthroplasty was used in 147 of these operations. Assessment was based on a modification of the British Orthopaedic Association Knee Function Assessment Chart (1978) and 137 knees were available for review. Eighty nine percent of patients suffering osteoarthritis, and 79% of patients with rheumatoid arthritis were satisfied or enthusiastic with their prosthesis. Nineteen percent of rheumatoid patients and 4% of osteoarthritic patients considered the result of their operation disappointing. In both groups, the operated knee constituted minimal persisting disability to the patient when reviewed. Seventeen knees (11.3%) were assessed as unsatisfactory, of which 7 (4.6%) were due to infection, and 5 (3.3%) were due to loosening. Revision procedures were performed in 7 knees (5%), for instability or loosening. Improvements in arthroplasty design have resulted in alternative prostheses now being chosen by most surgeons for knee replacement, and the long term results of these newer prostheses must be evaluated with those results obtained using the original geometric prosthesis.