DOES THE NUMBER OF PATELLOFEMORAL INSTABILITY EPISODES CORRELATE WITH THE PREVALENCE AND SEVERITY OF CHONDRAL AND OSTEOCHONDRAL LESIONS IN PEDIATRIC AND ADOLESCENT PATIENTS?

DISCLOSURES: None BACKGROUND: Current literature indicates that the risk of chondral and osteochondral injuries following patellofemoral instability events ranges from 40 to 96%. It is unclear based on current literature if there is an association between the number of instability events and the prevalence and severity of chondral and osteochondral injuries. HYPOTHESIS/PURPOSE: The purpose of this study was to investigate the prevalence and severity of chondral and osteochondral injury following patellar dislocations based on number of dislocations and accounting for other patellofemoral instability risk factors (patella alta, trochlear dysplasia, growth status). METHODS: Retrospective chart review was performed for patients under the age of 18 years with a prior history of traumatic patellar dislocation, documented number of instability events, and MRI available for review. Patients were grouped into those with 1 dislocation and >1 dislocation. A priori power analysis based on previous literature demonstrated a required minimum of 82 patients in each group (alpha=.05, power=90%, p1= 70%, p2=90%). Chart review was performed on all patients with diagnosis of patellofemoral instability for past 3 years to determine inclusion and record number of dislocations. MRI and radiographs were independently reviewed by a Musculoskeletal Radiologist and Orthopaedic Surgeon. Chondral injury severity (none, partial thickness, full thickness, osteochondral), location of injury, skeletal maturity, Caton-Deschamps index (CDI), and sulcus angle were recorded. Any discrepancies were settled by review by senior author. Poisson multivariate regression, chi-square, and descriptive statistics were used as appropriate. RESULTS: 99 patients were included in each group. There was no statistically significant difference in the prevalence of chondral injury between patients with one dislocation versus more than one dislocation (64.65% versus 55.56%, p=.19) (Table 1). Multivariate regression analysis determined that no factor (patella alta, trochlear dysplasia, skeletal maturity, number of dislocations) was associated with prevalence of chondral injury. Multivariate regression analysis determined patella alta (CDI >1.3) was a significant factor in severity of chondral injury (p=.016). CONCLUSION: A history of multiple patellar dislocations is not associated with a higher prevalence or increased severity of chondral injury compared to a single patellar dislocation event. In patients with patella alta, a lower threshold for surgical management may be warranted due to its association with more severe cartilage injury, if not already present.