Comparison of results of different types of knee arthroplasties

We summarise our experience gained with knee arthroplasties over 18 years. Between 1976 and 1994 1103 knee arthroplasties (1044 primary cases, 59 revisions) were performed at the Orthopaedic Department of the National Institute of Rheumatology and Physiotherapy in Budapest, Hungary. The diagnoses were osteoarthritis (OA) in 50.9%, rheumatoid arthritis (RA) in 40.7% and other causes in 8.4%. The average age of the patients at the time of the operation was 57.6 years (range 14-81 years). The types of primary implant were as follows: 60 constrained (hinge) prostheses, 876 unconstrained (sledge) prostheses, 108 semiconstrained (total condylar) prostheses. The mean follow-up period was 11.4 years for the hinge-type prostheses, 10.3 years for the unconstrained prostheses and 1.6 years for the semiconstrained prostheses. Reviewing the 59 revision cases, we conclude that complications with the constrained prostheses reached 17.8% and, most presented within the 1st year. Because of this high complication rate, the use of hinge prostheses has been reduced in this department to only selected cases. After sledge prosthesis implantation most of the complications (overall 5.3%) appeared after 1 year in aseptic circumstances. Given the short follow-up period of the semi-constrained total condylar knee replacement, apart from one infection in a patient with rheumatoid arthritis no other complication has been recorded. Summarising these data, it can be concluded that on average the knee function, using a standardised scoring system, improved from 38% to over 80% by introducing the semiconstrained total condylar knee prosthesis.