To explore the clinical efficacy and long-term prosthesis survival rate of mobile bearing unicompartmental knee arthroplasty in the treatment of knee osteoarthritis.

A retrospective analysis was performed in 1084 patients with primary medial compartment osteoarthritis of the knee who were treated by mobile bearing unicompartmental knee arthroplasty between April 2007 and June 2022. The patients with other knee diseases, severe knee deformity, history of knee osteotomy or arthroplasty, intolerance for surgery, and invalid follow-up information were excluded. All the patients were treated in orthopetic department of the 960th Hospital. The clinical treatment was evaluated by Western Ontario and Mcmaster University osteoarthritis index (WOMAC),Oxford University knee score (OKS) and knee range of motion (ROM). The changes between old and new instruments, and between different ages on the clinical efficacy and survival rate were compared. The long-term survival rate of prosthesis was evaluated by life-table survival analysis. Paired sample t test was used to compare the efficacy between preoperative and final follow-up, two independent sample t test was used for postoperative comparison between new and old device groups, and univariate analysis of variance was used for comparison between different age groups.

The last follow-up time point was December 2022. The follow-up time were (62±40) months on average, 114 patients were followed up for more than 10 years, 435 for five to 10 years, and 535 for less than five years. The average age were (62±8) years. WOMAC score improved from (58.9±5.0) before operation to (26.7±7.2) after operation (t=121.570, P<0.05); OKS score increased from (36.7±4.3) before operation to (55.4±2.7) after operation (t =-121.317, P<0.05); ROM of knee joint was (102.7±6.1) before operation and (116.7±5.1) after operation (t=-58.904, P<0.05). A total of 41 postoperative complications occurred, among which the dislocation of bearing was the highest . The over-all survival rate of prosthesis was 95.9%, and the long-term prosthesis survival rate was 93.9% in patients followed for more than 10 years. The survival rate was 96.1% in both traditional and new instrument groups, there was no statistically significant difference (P>0.05). The survival rate in different age groups was 91.8% in group of age ≤55 years, 97.3% in group of 55 to 75 years old, 96.8% in group of age >75 years. The difference between groups was statistically significant (P=0.02).

OUKA has a reliable clinical effect in the treatment of medial knee osteoarthritis, and has a high long-term prosthesis survival rate. With the progress of surgical techniques and the improvement of prosthesis design, this surgical method can be applied more and more widely in clinic. Accurate indication selection and accurate operation are essential to obtain good clinical efficacy and avoid complications.