Patellofemoral positioning CT protocol has diagnostic ability to differentiate patellar maltracking phenotype

Area of Science:

• Orthopedic imaging
• Biomechanical analysis of the knee

Background:

• Patellofemoral pain syndrome (PFPS) and instability often involve dynamic patellar maltracking.
• Traditional radiographs have limitations in capturing this dynamic nature, hindering accurate diagnosis.

Purpose of the Study:

• To introduce and evaluate a novel CT imaging protocol for patellofemoral maltracking.
• To assess the influence of knee positioning on patellofemoral indices.
• To determine the protocol's efficacy in classifying maltracking phenotypes.

Main Methods:

• Retrospective review of 65 patients undergoing PFPS surgery.
• Comparison of patellofemoral indices from standard radiographs and a three-position CT protocol (45° flexion, extension, extension with quadriceps contraction).
• Statistical analysis including logistic regression to differentiate maltracking phenotypes (Dislocator, Subluxator, Neither).

Main Results:

• Knee position significantly influences patellofemoral indices on CT scans.
• Quadriceps contraction during CT scanning exacerbates maltracking indices.
• CT scans in extension and with quadriceps contraction effectively differentiate maltracking phenotypes, unlike standard radiographs or CT at 45° flexion.
• Key predictors of maltracking severity include Lateral Offset and Insall-Salvati Ratio in extension, and changes in Lateral Offset and Lateral patellofemoral angle (LPFA) between extension and quadriceps contraction.

Conclusions:

• Standard radiographs are insufficient for reliably classifying patellar maltracking phenotypes in PFPS.
• A dedicated CT protocol with scans in extension and under quadriceps contraction enhances diagnostic accuracy for PFPS.
• This advanced imaging approach can guide personalized treatment strategies based on specific maltracking mechanics.