Role of positioning of femoral component in the anterior-posterior direction on postoperative anterior pain in TKA.

Introduction and Purpose: The patellofemoral joint has proved to be the most problematic element of modern TKA for postoperative anterior knee pain; the positioning of the femoral component constitutes a critical phase in this issue. The objective of our study was to evaluate the possible role of either anterior positioning or posterior positioning of the femoral shield compared to the reference plane represented by the anterior cortex, on the anterior knee pain after knee arthroplasty.
Methods: Forty-eight patients treated with TKA were followed up approximately 12 months. None of them have been submitted to any patellar treatment. We observed the position of femoral shield with respect to the anterior cortical line of femur dividing patients into three groups: patients with significant notching, patients with no notching (shield corresponding to anterior cortical line) and patients with anterior positioning of shield. We evaluated clinical and functional outcomes with KSS, anterior knee pain with Kujala's score and adverse events such as periprosthetic fractures.
Results: We found a better clinical and functional result for patients with femoral shield positioned in line with anterior cortical cortex with respect to both TKAs with femoral notching and to protruding anterior femoral components; there were no main differences in anterior postoperative score by Kujala's system. We observed a periprosthetic fracture in a patient with an important femoral notching.
Conclusions: We cannot consider our study as an objective conclusion to the argument. We need more RCTs in order to study the proper influence of either notching or protrusion of femoral shield component onto anterior postoperative pain. Anyway positioning of femoral shield in anterior-posterior direction could be an interesting new critical object of study about anterior knee pain after TKA.