Novel method for diagnosing lateral patellar compression syndrome using X-ray: a retrospective case-control study

Area of Science:

• Orthopedics
• Radiology
• Sports Medicine

Background:

• Diagnosing lateral patellar compression syndrome (LPCS) lacks a standardized reference, relying on subjective clinical judgment and examination findings.
• Conventional X-rays show limited accuracy in detecting patellar tilt using the congruence angle (CA) and patellar tilting angle (PTA).
• Objective diagnostic criteria are needed to improve the accuracy of LPCS diagnosis.

Purpose of the Study:

• To evaluate the diagnostic value of the lateral patellar compression angle (LPCA) in lateral patellar compression syndrome (LPCS).
• To compare LPCA measurements in patients with LPCS, patellar dislocation (PD), and meniscus tears (MT).
• To determine the sensitivity and specificity of LPCA for diagnosing LPCS.

Main Methods:

• Eighty-seven patients were categorized into LPCS, PD (control), and MT (negative control) groups (29 each).
• Patellar axial radiographs in 30° knee flexion were analyzed by a senior radiologist and sports medicine physician.
• Measurements included LPCA, CA, and PTA; statistical analyses (ANOVA, Kruskal-Wallis H test, Bonferroni correction) were performed.

Main Results:

• LPCA was significantly higher in the LPCS group compared to MT and PD groups (P<0.01).
• LPCA was also significantly higher on the affected side in LPCS patients (P=0.04).
• An LPCA threshold of >13.9° demonstrated 89.66% sensitivity and 68.97% specificity for LPCS diagnosis (AUC: 0.82).

Conclusions:

• The lateral patellar compression angle (LPCA), measured on axial knee radiographs at 30° flexion, is elevated in patients with LPCS.
• LPCA shows potential as a valuable tool for the objective diagnosis of lateral patellar compression syndrome.
• This radiographic measurement may aid clinicians in improving the diagnostic accuracy for LPCS.