PATIENT-REPORTED OUTCOMES OF UNICOMPARTMENTAL KNEE ARTHROPLASTY FOR END-STAGE OA : A COMPARATIVE STUDY WITH TOTAL KNEE ARTHROPLASTY

Background The indication of unicompartmental knee arthroplasty (UKA) for end-stage osteoarthritis (OA) remains controversial. This study aimed to investigate patient reported outcomes (PROs) of UKA in patients with severe varus deformity of the knee and compare the results with those of total knee arthroplasty (TKA) at mid-term follow up. Methods A total of 96 TKAs of 69 patients and 61 UKAs of 50 patients were included. All patients presented with severe knee OA with hip-knee-ankle angle (HKA) ranged from −25 degree to −10 degree, preoperatively. Mean HKAs in TKA group and UKA group were −14.95o and −13.38o, respectively. PROs were assessed using Knee Society Score (KSS 2011), PainDETECT score (PD), and Pain Catastrophizing Scale (PCS) at a mean follow up of 58.65 months for TKA and 58.05 months for UKA. Kaplan-Meier survival analysis was performed to assess implant survival. Complication rate was also assessed. All data were compared between TKA group and UKA group. Results Mean postoperative knee flexion angle was 124.38 o for TKA group and 133.69 o for UKA group, indicating that knee flexion angle of UKA was significantly greater than that of TKA (p=0.000). There were no statistically differences in KSS and their items, PD, and PCS. Regarding mid-term survivorship, TKA (96.0%) was less than UKA (96.8%), but there was no statistically significance. Major complications of the knee occurred in 4cases (4.0%) for TKA and 7 cases (11.1%) for UKA but there was also no statistically significance. Complications of UKA included 3 cases of OA progression in the lateral compartment. Discussion Although greater flexion angle was observed in UKA group, there was no significant differences in PROs between the two groups. The survival rate are practically considered worse in TKA and the complication rate are practically considered worse in UKA, but there are no statistically significance. Further assessment should be needed after increasing the number of subjects and follow-up period.