THE VALUE OF COMPUTED-TOMOGRAPHY FOR THE DIAGNOSIS OF RECURRENT PATELLAR SUBLUXATION IN ADOLESCENTS

Objective: To determine if computed tomography of the patellofemoral j oint has any advantage over standard radiologic techniques in the eval uation of recurrent patellar subluxation. Design: A case series. Setti ng: A tertiary children's hospital out-patient clinic. Participants: F orty consecutive adolescents with a clinical diagnosis of recurrent pa tellar subluxation (study group) and 14 volunteers with normal knees ( control group). Interventions: A standardized radiologic protocol, inc luding axial views of the patella at 30-degrees of knee flexion, with and without external torsion of the tibia, and computed tomography (CT ) of the patella at 15-degrees of knee flexion. Main Outcome Measures: The lateral patellofemoral angle on the axial views and on the CT sca n and patellar centralization on the CT scan. Results: In the control group, no radiologic evidence of recurrent patellar subluxation was fo und. In the study group, an abnormal lateral patellofemoral angle was found in 25% of axial views; this rate increased to 42% with external rotation and 86% on the CT scan. Patellar centralization was abnormal in 79% of cases. Conclusions: CT of the patellofemoral joint is more s ensitive than standard radiographs for the diagnosis of recurrent pate llar subluxation. The use of CT is recommended when standard radiograp hs appear normal.