Trochlear Dysplasia As Shown By Increased Sulcus Angle is Associated with Osteochondral Damage in Patients with Patellar Instability.

Abstract Purpose The primary objective was to describe the incidence of osteochondral damage in our cohort of patients with patellar instability. The second was to assesss for associations between patient demographics, duration of patellar instability, and quantitative radiographic measurements of anatomic risk factors for patellar instability and osteochondral damage. Methods A retrospective chart review identified patients treated for patellar instability at a tertiary referral center between 2013 and 2018. Patients were evaluated for osteochondral injury with either Magnetic Resonance Imaging (MRI) if treated non-operatively or operative reports if treated surgically. Caton-Deschamps (CD) ratio, proximal tibial tubercle to trochlear groove (pTT-TG) distance, distal tibial tubercle to trochlear groove (dTT-TG) distance, lateral trochlear inclination (LTI) angle, lateral patellar inclination (LPI) angle, and sulcus angle were calculated from MRI scans. Trochlear dysplasia is an important risk factor for patellar instability which can be reliability quantified by pTT-TG, dTT-TG, LTI, sulcus angle, and LTI. Demographic data including age at first instability event, gender, BMI, symptom duration, and number of dislocations were documented. Results A total of 125 knees in 118 patients (average age: 13.9±3.4, 48% female) were identified with patellar instability. Within this cohort, 67% were treated surgically and 53% had osteochondral damage. There was no association identified between osteochondral injury and age, gender, BMI, symptom duration, LTI, LPI, dTT-TG, pTT-TG, or number of dislocations. Increased sulcus angle (more dysplasia) had a statistically significant association with osteochondral pathology (P=0.021), and higher sulcus angles were statistically significantly associated with acute osteochondral fracture compared to chondral injury (P=0.001). Conclusions Using quantitative analysis of trochlear dysplasia, this study identified a significant association between trochlear dysplasia (sulcus angle) and the incidence of osteochondral damage in our cohort of patients with patellar instability. The frequency of dislocation or subluxation and patient demographics were not significantly associated with osteochondral damage. Level of Evidence III, Retrospective prognostic study