Low grade of radiographic osteoarthritis predicts unsatisfactory response of the contralateral knee replacement in two-stage bilateral total knee arthroplasty.

purposeIt is difficult to counsel patients with bilateral osteoarthritis who are unsatisfied with their first knee replacement as to whether they are likely to have a better outcome after the contralateral knee is replaced. The purpose of this study was to determine whether predictive factors can be found to prognosticate outcome of the second-side knee replacement when a patient has an unsatisfactory response to the first, with the hypothesis that predictors, such as prosthetic factors and radiographic level of osteoarthritis, may be able to predict a satisfactory response to the contralateral knee replacement. MATERIALS AND

methodsAn analysis of staged bilateral knee replacements performed at a tertiary arthroplasty centre from 2012 to 2018 was undertaken. A total of 550 knee replacements in 275 patients were included in this study. The primary variable measured was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Satisfactory response to surgery was defined as a WOMAC score improved by 17 points or more, and 56 or greater. Patients who did not achieve a satisfactory response with their first knee replacement were further analysed for predictive factors (age, sex, pre-operative score, mental score, socioeconomic status, type of prosthesis, use of navigation, patella resurfacing and radiographic osteoarthritis) of an unsatisfactory response for their contralateral knee replacement.

resultsOverall, 44 (16%) patients failed to achieve a satisfactory response from both their first and contralateral knee replacements. The factor most predictive of an unsatisfactory response to their first knee replacement was pre-operative mental health score. However, in patients who did not achieve a satisfactory response with their first knee replacement, radiographic osteoarthritis, as measured by the Kellgren-Lawrence (KL) score was the main predictor of satisfactory response for their contralateral knee replacement. Only patients with KL grade 4 osteoarthritis were likely to have a satisfactory response with their contralateral knee replacements (KL4 versus KL3, Odds ratio 3.57 (CI 1.26-10.03) p = 0.016*). Patients with KL grade 3 osteoarthritis were unlikely to have a satisfactory response, and in this series, no patient with KL grade 2 osteoarthritis had a satisfactory response.

conclusionIn a patient who has an unsatisfactory response to their first knee replacement, the best predictor of achieving a satisfactory response to his/her contralateral knee replacement is the level of radiographic osteoarthritis in that knee. LEVEL OF EVIDENCE: IV: Retrospective Cohort study.