The reversed dynamic patellar apprehension test mimics anatomical complexity in lateral patellar instability

Area of Science:

• Orthopedic Surgery
• Sports Medicine
• Biomechanics

Background:

• Recurrent lateral patellar instability presents a significant clinical challenge.
• Accurate assessment of patellar stabilizer insufficiency is crucial for effective treatment planning.

Purpose of the Study:

• To develop and validate a dynamic physical examination test, the reversed dynamic patellar apprehension test (ReDPAT).
• To functionally simulate patellar instability events and quantify patellar stabilizer insufficiency.
• To correlate test results with anatomical predispositions for lateral patellar instability.

Main Methods:

• Prospective evaluation of 78 patients with recurrent lateral patellar instability and 35 controls using the ReDPAT.
• Assessment of anatomical risk factors including trochlear dysplasia, tibial tuberosity-trochlear groove distance, patellar height, and malalignment.
• Statistical analysis of test sensitivity, specificity, and correlation with anatomical factors.

Main Results:

• The ReDPAT demonstrated high sensitivity (93.7%) and specificity (88.2%) for detecting lateral patellar instability.
• A significant correlation was found between the positive ReDPAT knee flexion angle and the severity of trochlear dysplasia, valgus deformity, and the number of anatomical risk factors.
• Patients with instability had an average of 3.4 anatomical risk factors, with severe trochlear dysplasia and patella alta being most common.

Conclusions:

• The ReDPAT is a reliable clinical tool for assessing lateral patellar instability.
• The test provides patient-specific information on the limits of stable patellar tracking.
• ReDPAT findings can assist in surgical decision-making, particularly for bony procedures in patellar dislocation treatment.