Effect of Patellofemoral Arthroplasty on Patellar Height in Patients with Patellofemoral Osteoarthritis

Abstract

Osteoarthritis (OA) in the knee is common, painful, and may be uni- or multicompartmental. The compartment affected by arthritis may be due to trauma, malalignment (varus or valgus), or in the case of patellofemoral OA, patella alta. Patellofemoral arthroplasty (PFA) is an effective partial knee replacement surgery for patellofemoral OA. We hypothesized that PFA can decrease patellar height. In addition, we predicted better outcomes for patients with patella alta before PFA and those whose patellar heights decreased after PFA. This is a retrospective cohort study of PFA patients from 2012 to 2020. Before and after PFA, we measured patellar heights on X-ray images and collected patient-reported outcome measures (PROMs) (International Knee Documentation Committee score, Kujala Anterior Knee Pain Score, and Veterans RAND 12-Item Health Survey for mental and physical health). Statistical analyses assessed PROMs and compared outcomes based on pre- and postoperative patella height. Of 133 knees, 73% presented with patella alta and 61% had patellar heights that decreased after PFA. Compared with patients who did not present with patella alta, patients with patella alta reported similar outcomes with respect to knee function, pain, and general physical and mental health. Compared with patients whose patellar heights decreased after PFA, patients whose knees did not decrease in height reported greater improvements in pain and function. Our findings suggest that patella alta is commonly found in patients with patellofemoral OA and that PFA can decrease patellar height. Future studies are needed to assess whether patellofemoral OA patients with greater degrees of patella alta would benefit from staged or concurrent tibial tubercle distalization.

Modern Patellofemoral Arthroplasty

“…As a result, this must be looked for preoperatively and accounted for with a surgical technique to improve patellofemoral tracking and the subsequent outcome. Similarly, patella alta and trochlear dysplasia are significantly more frequent in PFOA with an increase in both trochlear angle and Dejour score noted by Mofidi et al 47,48 . PFA can reduce patella height; however, this has not been quantified and the effect of patella height on the overall outcome of PFA is uncertain with the literature showing mixed results 44,48-50 .…”

“…Similarly, patella alta and trochlear dysplasia are significantly more frequent in PFOA with an increase in both trochlear angle and Dejour score noted by Mofidi et al 47,48 . PFA can reduce patella height; however, this has not been quantified and the effect of patella height on the overall outcome of PFA is uncertain with the literature showing mixed results 44,48-50 . Beckmann et al concluded that patients with patella alta are contraindicated for an inlay design based on their 2019 study showing a high rate of revision for patella clunk after PFA with the inlay HemiCAP Wave implant 51 .…”