Relationship Between Patellar Morphology and Known Anatomic Risk Factors for Patellofemoral Instability

Background: Patellar instability (PI) is a common problem among pediatric, adolescent, and young adult patients. Recent literature has shown a correlation between pathoanatomy and PI. Purpose/Hypothesis: The purpose of this study was to determine if there is any difference in patellar shape in patients with and without PI and if there is any association between the shape of the patella and the shape of the trochlea. Our hypothesis was that there would be no association between the shape of the patella and the likelinhood of having PI and that the shape of the trochlea would not be associated with patellar morphology. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance imaging (MRI) scans were analyzed for 97 study patients with PI and 100 control patients with anterior cruciate ligament tears. Radiologic measurements of trochlear morphology were collected via MRI; 15 measurements of patellar morphology were then measured using axial MRI scans. Comparisons between the control and PI groups were performed using a 2-tailed t test. Regression analysis was performed to determine if associations existed between the 15 patellar morphology measurements and the trochlear dysplasia measurements. Results: There were no statistically significant differences between the PI and control groups for the majority of patellar morphology measurements. With regression analysis, there were no statistically significant associations between the majority of patellar morphology measurements and the trochlear dysplasia measurements. Conclusion: Patellar morphology is highly variable in knees with and without PI. There was a minimal association between measurements of patellar morphology and trochlear dysplasia.