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Objective patellar instability: MR-based quantitative assessment of potentially associated anatomical features
Joan S Escala1, José M Mellado, Montserrat Olona
1Servei de Cirurgia Ortopèdica i Traumatologia, Hospital Universitari de Tarragona Joan XXIII, Carrer Doctor Mallafrè Guasch, Spain. jsescalaarnau@hotmail.com
Summary
Quantitative MRI parameters can diagnose objective patellar instability (OPI). Lateral patellar tilt, trochlear groove depth, and Insall-Salvati index show high sensitivity for OPI detection.
Area of Science:
- Radiology
- Orthopedics
- Medical Imaging
Background:
- Objective patellar instability (OPI) is a clinical condition requiring accurate diagnosis.
- Knee magnetic resonance (MR) imaging offers multiple quantitative parameters for assessment.
Purpose of the Study:
- To evaluate and compare the diagnostic utility of various quantitative MR parameters for OPI.
- To identify MR features most associated with objective patellar instability.
Main Methods:
- Retrospective analysis of knee MR examinations in 46 OPI patients and 69 controls.
- Statistical comparison of quantitative parameters including trochlear groove depth, Insall-Salvati index, patellar nose length, morphology ratio, and patellar tilt.
Main Results:
- OPI patients exhibited shallower trochlear grooves, larger Insall-Salvati indices, shorter patellar noses, smaller morphology ratios, and larger patellar tilts.
- Lateral patellar tilt (92.7% sensitivity) and trochlear groove depth (85.7% sensitivity) were highly sensitive.
- Morphology ratio (86.9% specificity) and patellar nose (84.5% specificity) demonstrated high specificity.
Conclusions:
- Shallow trochlear grooves and patella alta (detected by Insall-Salvati index) are key findings in OPI.
- Patellar nose and morphology ratio are specific indicators of OPI.
- Lateral patellar tilt is the most sensitive and specific MR parameter for diagnosing OPI.