Aiming for anatomical femoral axis on the coronal plane leads to good-to-excellent short-term outcomes in isolated patellofemoral arthroplasty.

Background: In patellofemoral replacement (PFR) coronal alignment is mostly influenced by local condylar anatomy. However, there is still a lack of consensus regarding references to follow intraoperatively for the optimal positioning of the trochlear component. The aim of this study was to assess whether aiming for the anatomical femoral axis on the coronal plane leads to improved clinical outcomes and whether coronal alignment correlates with clinical outcomes. Methods: Forty-two patients who underwent PFR were retrospectively evaluated at a minimum one-year follow-up using Kujala and Knee Society Score (KSS). Moreover, patients underwent an anteroposterior hip-to-knee X-ray to evaluate the coronal alignment of the trochlear component with respect to the femoral anatomic and mechanical axis. Prosthesis coronal alignment, Kujala, and KSS were assessed for possible correlation. Results: Mean follow-up time: 29.1 months. Mean KSS for pain: 90 (±8.9), for function: 93.7 (±15.9); mean Kujala: 89.2 (±13.6). Mean prosthesis coronal alignment was 3.3 ± 2.3° in valgus with respect to the femoral anatomic axis and 7.4 ± 2.6° in valgus with respect to the femoral mechanical axis. No correlations were found between coronal alignment and KSS or Kujala scores. Conclusions: Results from the current study showed that PF replacement with a third-generation implant led to good-to-excellent outcomes. In addition, the surgical technique used for aligning femoral component in this study resulted in reduced coronal alignment variability and achieved good short-term clinical outcomes. Keywords: Osteoarthritis; Patellofemoral; Patellofemoral arthroplasty; Unicompartimental replacement.