Minimum 10-year follow-up of mobile bearing medial unicompartmental arthroplasty: Does the presence of preoperative radiographic patellofemoral arthritis influence patient outcomes?

BACKGROUND

Medial unicompartmental knee arthroplasty (UKA) has become an accepted means of treating end stage anteromedial osteoarthritis of the knee. However, the presence of patellofemoral osteoarthritis on preoperative radiographs has proven to be confusing for orthopaedic surgeons in terms of candidacy for unicompartmental arthroplasty. The purpose of this study is to assess whether the presence of preoperative radiographic patellofemoral joint (PFJ) arthritis influences implant survivability or clinical outcomes at minimum 10-year follow-up.

METHODS

Preoperative radiographs of 502 knees treated between 2004 and 2010 with medial mobile-bearing UKA and minimum 10-year follow-up (mean 13.3 years ± 2.0) were assessed by an observer blinded to the clinical outcome, and the patellofemoral joint (PFJ) was graded using the modified Altman classification. In the analyzed cohort there were 310 (61.8 %) grade 0, 135 (26.9 %) grade 1, 51 (10.2 %) grade 2, and 6 (1.2 %) grade 3 knees. Clinical outcomes were assessed using Knee Society pain, clinical and functional scores, and the University of California Los Angeles (UCLA) activity rating.

RESULTS

There were 66 (12.7 %) knees revised for overall survival of 86.9 %. The most common reason for revision was arthritic progression, in 27 (40.9 %) knees. There was no difference in Kaplan-Meier survival based on preoperative patellofemoral grade (p = 0.8047) and mean time to revision was similar between groups (p = 0.6330). When analyzing outcomes for the entire cohort there was significant improvement from preoperative to postoperative range of motion (ROM) (p = 0.0002) and Knee Society pain, clinical, and functional scores (all p < 0.0001).

CONCLUSIONS

This study demonstrates that at long term follow-up there is not a significant difference in overall implant survival or patient reported outcome scores based upon preoperative radiographic PFJ arthritic state. Thus, the radiographic appearance of the patellofemoral joint alone should not be a deciding factor when considering patients as candidates for medial UKA.