Purpose: 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.
Methods: 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.
Results: 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.
Conclusions: 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.