Patellofemoral arthroplasty remains controversial, primarily due to high failure rates reported with early implants. Recent design changes may improve the reproducibility of surgical technique and consistency of outcomes. The purpose of this study is to evaluate the early results of one of the largest consecutive series to date of PFA with a milling system technique, and factors that may lead to early failure.
From 2011 to 2018, 250 patellofemoral arthroplasties were performed by a single surgeon for unicompartmental arthritis. Patients had an average age of 71 years, 66 inches in height, and 166 pounds weight. The majority of patients were female (182/250, 73%). Radiographic and clinical evaluations were performed. Followup was performed for minimum 2 years, with average 4.2 years followup.
With the milling technique, there were no technical complications, component placement or sizing deviations, or intraoperative abandonments to TKA. Patellar thickness averaged 20.3mm prior to resection, and 21.7mm after resurfacing. There were 4 lateral releases performed. Knee Society Scores increased from average 78 to 98 (p< 0.05). The impairments leading to low preoperative scores, and also serving as areas of most improvement, were stair climbing and anterior knee pain relief. One patient developed asymptomatic patellar avascular necrosis. Two patients have been converted to TKA. One clinical failure is due to confounding pain from an ipsilateral arthritic hip and lower spine.
With careful patient selection, patellofemoral arthroplasty can have excellent short-term results. However, risk for need for conversion to TKA exists regardless of strict inclusion criteria. A history of prior open knee surgery or confounding pain sources can negatively impact outcomes, regardless of a technically successful PFA procedure. Nonetheless, in most patients, with careful attention to 2 particularly important surgical steps, patellofemoral arthroplasty reliably improves stair function and anterior knee pain.