To investigate the effect of different degrees of patellofemoral joint cartilage degeneration on short-term outcome of medial mobile-bearing unicondyle knee arthroplasty.

The data of 75 patients who underwent medial mobile-bearing unicondyle knee arthroplasty (UKA) or total knee arthroplasty (TKA) for anteriormedial osteoarthritis in Shenzhen People’s Hospital from January 2017 to December 2018 were retrospectively analyzed. According to the intraoperative exploration of patellofemoral joint cartilage degeneration, the patients were divided into four groups: no patellofemoral joint degeneration+ UKA group (the non-degeneration group), the medial patellofemoral joint degeneration+ UKA group (the medial degeneration group); the medial and lateral patellofemoral joint degeneration+ UAK group (the medial-lateral degeneration group); the medial and lateral patellofemoral joint degeneration+ TKA group (the TKA group). The preoperative and postoperative Oxford knee assessment scores (OKS), Hospital for Special Surgery(HSS)knee scores, and the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index scores of the four groups were compared and analyzed by one way ANOVA. The prosthesis loosening, dislocation, and force line changes were recorded during the final follow-up.

All the patients were followed up for (36±10) months on average. The postoperative OKS, HSS, and WOMAC scores of the four groups were improved compared with those before operation (F=18.555, P<0.001; F=5.867, P=0.001; F=22.671, P<0.001). Comparing the differences of OKS, HSS and WOMAC scores before and after the surgery, there was no statistically significant difference between the non-degeneration group and the medial degeneration group (all P>0.05). Compared with the non-degeneration group and the medial degeneration group, the function improvement of the medial-lateral degeneration group was slightly worse, and the difference was statistically significant (all P<0.05). The difference in OKS, HSS, and WOMAC scores between the medial-lateral degeneration group and the TKA group was not statistically significant (all P >0.05). No prosthesis loosening, dislocation, or force line change was found at the final follow-up.

Medial patellofemoral joint degeneration has little effect on the outcome after medial mobile-bearing UKA. Cautions should be taken with the lateral patellofemoral joint cartilage degeneration, choosing UKA or TKA should be individually considered.