CLINICAL OUTCOME AFTER REVISION OF UNICONDYLAR PROSTHESIS TO TOTAL KNEE PROSTHESIS

Abstract

One of the advantage in using unicondylar prosthesis seems to be the preservation of the bone stock, which allows most often easily revision to a total knee replacement if required. The purpose of the study was to compare the patients outcome after revision of unicondylar prosthesis with a group of patients who have received total knee replacement primarily.

Material and Method: 28 patients after revision unicondylar prosthesis (group A) and 28 patients after primary total knee replacement (group B) were included in the study. The two groups were matched according to age, sex, weight, height, type of prosthesis and follow-up time. The patients’ evaluation was based on the Knee-Society-Score and the WOMAC-score. X-rays of the knee were taken in the AP weight bearing and lateral view.

Results: In group A the average follow-up time was 55±15 months and in group B 56±13 months. The knee-score showed 71.8±18 and 80.4±10.4 points and the function-score 56.1±15 and 62±19 points for group A and group B respectively without any statistical difference. The subjective assessment according to the WOMAC score showed difference in the functional outcome. A better range of motion of 110±11° was noticed for group B in comparison with group A 102±8° (p=0.004). The revised patients required a significantly higher poly-ethylene-inlay (12.9±3mm) compared to the primarily implanted ones (10.3±3mm) (p=0.004).

Discussion: Based on our findings revision of unicondylar to total knee replacement provides comparable results to primarily implanted total knee arthroplasty and should be considered for the treatment of unicompartmetal osteoarthritis even in younger patients, where a revision operation during lifetime is more likely. Despite the difference regarding the height of the inlay of 3mm, adequate bone stock was still found in order to implant an unconstraint type of knee prosthesis. The impaired functional outcome seems to be related to the fact of the reoperation and a significant longer history of osteoarthritis for group A in comparison with group B.