Does Patellofemoral Disease Affect Outcomes in Contemporary Medial Fixed-Bearing Unicompartmental Knee Arthroplasty?

Pre-existing patellofemoral disease has traditionally been a contraindication to unicompartmental knee arthroplasty (UKA), as proposed by Kozinn and Scott. More recently, some propose that patellofemoral disease can be ignored in UKA; however, the supporting research is predominantly in mobile-bearing designs. The study purpose was to evaluate the effect of patellofemoral disease osteoarthritis severity on latest outcomes after fixed-bearing medial UKA.

A retrospective review of 147 consecutive medial fixed-bearing UKAs with minimum 1-year follow-up was performed. The medial and lateral patellofemoral compartments were graded according to the Kellgren & Lawrence grading system, Osteoarthritis Research Society International atlas, and intraoperative assessment performed using the Outerbridge classification. Prospectively collected University of California Los Angeles Activity Level, modern Knee Society pain and function scores, and Likert scale satisfaction were correlated with presence and severity of pre-existing patellofemoral disease.

One hundred forty-three medial UKAs were analyzed with mean age, body mass index, and follow-up of 64.1 years, 30.7 kg/m², and 24.0 months, respectively. No correlations were observed between patellofemoral disease severity and patient-reported outcome measures at latest follow-up or improvement scores for Kellgren & Lawrence grading system or Osteoarthritis Research Society International atlas (P ≥ .058). Improvement in activity level scores was significantly higher for patients with less patellar and trochlear chondral damage despite not reaching minimal clinically important difference of 2.0 (P ≤ .028). Regardless of patellofemoral disease severity, 93% of UKAs were satisfied or very satisfied.

Clinical outcomes of fixed-bearing medial UKA were not adversely impacted by intraoperatively visualized or radiographically evaluated patellofemoral disease. Furthermore, long-term follow-up is warranted and caution should be used before considering patellofemoral disease as a contraindication for UKA.