Are results of total knee arthroplasty for isolated patellofemoral OA as good as for medial compartment OA? A medium-term retrospective comparative study.

Abstract

The aim of this study was to compare the results of isolated patellofemoral arthritis (IPFA) treated using a total knee arthroplasty (TKA) compared to the results of medial tibiofemoral arthritis treated with a TKA. We hypothesised that there would be no difference between functional outcomes for the two groups. Between 2003 and 2009, 32 TKAs were performed for IPFA (group I). Over this time period, a total of 813 primary TKAs were performed from which we identified a second group of patients who had undergone TKA for isolated medial tibiofemoral arthritis (group II: n = 32). These patients were matched based on age, sex, body mass index and average follow-up. The average age of patients in group I was 72.81 ± 6.6 years (59-83) and 71.97 ± 6.8 years in group II. The global International Knee Society (IKS) score was statistically significantly better in group I (114.72 ± 22 points) than in group II (84.9 ± 23.8). This difference was accounted for by better passive flexion, better walking distance and the absence of any coronal plane deformity. A total of 29 patients from group I were reviewed at an average follow-up of 64.58 ± 23.4 months, and 30 patients in group II were reviewed at an average follow-up of 66.13 ± 23.9 months (three were lost to follow-up in group I and two in group II). At final follow-up, there was statistically no difference between the two groups IKS score (175.34 ± 19.26 in group I vs. 170.13 ± 24.14 for group II) or Hospital for Special Surgery patella score (89.31 ± 9.98 points for group I vs. 89.16 ± 11.45 points for group II). We found no significant radiological difference between the two groups including patella height and orientation on axial views. The results of TKA for IPFA are as good as the results of TKA for isolated medial tibiofemoral arthritis with well-functioning prosthetic patellofemoral articulations. These results support our institutional preference for using TKA as treatment for IPFA in patients over 65-70 years old.