The clinical outcome of revision knee replacement after unicompartmental knee arthroplasty versus primary total knee arthroplasty: 8–17 years follow-up study of 49 patients

When unicompartmental knee arthroplasty (UKA) failure occurs, a revision procedure to total knee arthroplasty (TKA) is often necessary. We compared the long-term results of this procedure to primary TKA and evaluated whether they are clinically comparable. Twenty-one patients underwent UKA conversion to TKA between 1991 and 2000. The results of these patients were compared to the group of 28 primary TKA patients with the same age, sex and operation time point. The long-term outcomes were evaluated using clinical and radiological analysis. The mean follow-up period of the patients was 10.5 years. The UKA revision patients were more dissatisfied, as measured by the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) scale (0–100 mm) compared to the primary TKA patients (pain 18.1/7.8; p = 0.014; stiffness 25.7/14.4, p = 0.024; physical function 19.0/14.8, p = 0.62). Two patients were revised twice in the UKA revision group. There was one revision in the primary TKA group (p = 0.39). Improvement in range of motion (ROM) was better in the TKA patients compared to the UKA revision patients (8.2°/–2.6°, p = 0.0001). We suggest that UKA conversion to TKA is associated with poorer clinical outcome as compared to primary TKA.