Unicondylar vs. total knee arthroplasty in medial osteoarthritis: a retrospective analysis of registry data and functional outcome

It was the aim of our study to compare the functional outcome (WOMAC score, range of motion) achieved with unicondylar knee arthroplasty (UKA) and total knee arthroplasty (TKA). It was hypothesized that UKA and TKA would differ with regard to the WOMAC function scale (hypothesis 1) and the WOMAC total scale (hypothesis 2). It was assumed that the groups would differ with respect to changes in range of motion (ROM) over time (hypothesis 3). A retrospective comparative study was conducted to analyze data available from the federal state's Arthroplasty Registry (WOMAC score) and from clinical routine (ROM). Patients who underwent UKA or TKA between 2008 and 2015 were considered. ANOVAs for repeated measurements were applied, adjusted for age, to test hypotheses 1–3. The UKA group was comprised of 112 patients (age 65, BMI 29). The TKA group included 330 cases (age 69, BMI 29). Regarding hypothesis 1, the amount of improvement in WOMAC function was not influenced by the surgical group (no significant group*time interactions, p = 0.608). Similarly, for hypothesis 2, the amount of improvement in the WOMAC total score was not influenced by the surgical group (no significant group*time interactions, p = 0.392). Regarding hypothesis 3, we found no significant group*time interaction for the ROM data (p = 0.731). On the basis of our findings, it is concluded that whether knee osteoarthritis is treated with either medial UKA or TKA has no influence on the WOMAC total score or any of the WOMAC subscales. It has no effect on early or late ROM gain