Prevalence of Trochlear Dysplasia and Associations with Patellofemoral Pathology (166)

OBJECTIVES: Patellar instability is a common condition of adolescents with an incidence of 29 to 43 per 100,000. Trochlear dysplasia has been found in up to 85% of those with recurrent patellar instability and has been found in association with ACL rupture. However, the prevalence of trochlear dysplasia in the general population has not yet been defined. The purpose was to define the prevalence of trochlear dysplasia as defined by ultrasound in a skeletally mature population and characterize associations of trochlear dysplasia with patellofemoral pathology. METHODS: Skeletally mature adolescents and parents aged 50 and under presenting to orthopedics clinics were recruited from 2019 to 2020. Those with a history of intra-articular fracture, total knee arthroplasty, and syndromic ligamentous laxity or neuromuscular disease were excluded. Surveys were collected detailing any history of knee symptoms and surgery as well as an abbreviated Anterior Knee Pain Score (AKPS) with a score of 4 or greater being considered positive. Ultrasounds were obtained of bilateral knees and the osseous sulcus angle of the trochlea as well as the trochlear depth were measured (Figure 1). Basic descriptive statistics are reported. RESULTS: One hundred and two patients (203 knees) were studied. The mean osseous sulcus angle was 144.1±6.8° and the mean trochlear depth was 5.5±1.4mm. The distribution of outcomes of interest can be found in Table 1. High grade trochlear dysplasia was defined as two standard deviations from the mean which was shown to be a sulcus angle ≥158˚ or a trochlear depth of ≤3mm. Prevalence of high grade trochlear dysplasia based on sulcus angle was 3.0% and 5.9% based on trochlear depth. In the presence of high grade trochlear dysplasia as defined by osseous sulcus angle, there was a 32 times increased risk of previous patellar instability (p=0.007) and 10 times increased risk of a positive AKPS (p=0.016). All those with high grade trochlear dysplasia as defined by osseous sulcus angle had a history of, or current, patellofemoral pain. CONCLUSIONS: The prevalence of trochlear dysplasia in the general population is approximately 6%. There are significant associations of trochlear dysplasia not only with patellar instability but also with patellofemoral pain. Use of ultrasound to diagnose trochlear dysplasia may prove to be a rapid and useful tool in guiding patient education and treatment decisions.