Unicondylar knee arthroplasty does not lead to better WOMAC function or range of motion when compared to total knee arthroplasty
Due to a lack of consensus in the literature it was the aim of our study to compare the functional outcome (knee score, Range of motion (ROM)) between unicondylar knee arthroplasty (UKA) and total knee arthroplasty (TKA). Consequently, it was hypothesized that UKA and TKA would differ with regard to the WOMAC function scale (hypothesis1) and the WOMAC total scale (hypothesis2). In addition, it was assumed that the groups would differ with respect to changes in ROM over time (hypothesis3).
The study design was retrospective comparative. Patients who previously underwent primary knee arthroplasty, either unicondylar or total - were considered. For patient-reported functional outcome the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) was applied (WOMAC function and total scales). The WOMAC data was available from the federal state's arthroplasty registry (preoperative, one year postoperative). ROM data collected with goniometers were available from clinical routine / medical records (preoperative, postoperative days 4, 7 and 10 and one year postoperative). ANOVAs for repeated measurements were applied, adjusted for age, to test the hypotheses 1 – 3.
The UKA group had 112 patients (41 male, 71 female, age 65, BMI 29) and the TKA group 330 patients (125 male, 205 female, age 69, BMI 29).
Preoperatively, the WOMAC function score was 48 ±22 (mean ±standard deviation) in the UKA group and 53 ±21 in the TKA group. One year postoperative the WOMAC function improved to 22 ±22 in the UKA group and 25 ±23 in the TKA group. There was no significant group*time interaction (p=0.608, hypothesis 1). This means that the amount of improvement in WOMAC function was not influenced by the surgical group.
Preoperatively, the WOMAC total was 48 ±20 and 53 ±20 in UKA and TKA patients, respectively. One year after the procedure, the values improved to 21 ±21 in UKA patients and 23 ±22 in TKA patients. No significant group*time interaction was found (p=0.392, hypothesis 2). This means that the amount of improvement in the WOMAC total score was not influenced by the surgical group.
Regarding hypothesis 3 we found no significant group*time interaction for the ROM data (p=0.731, Fig. 3).
On the basis of our findings it is concluded that UKA and TKA do not differ in WOMAC function, WOMAC total (both one year postoperatively). Similarly there are no differences in early or late postoperative gain in ROM.