AXIAL RADIOGRAPHY OR CT IN THE MEASUREMENT OF PATELLOFEMORAL MALALIGNMENT INDEXES IN CHILDREN AND ADOLESCENTS

The present study compares the repeatability of patellofemoral malalig nment (PFM) indices obtained by 20 degrees flexion axial radiography ( AR) and computerized tomography (CT) with 0 degrees and 20 degrees fle xion of the knees in children and adolescents. Thirty-one patients wit h a mean age of 14.2 years (range 8 to 19.2 years) suffering from PFM were examined using these two radiographic techniques. The lateral pat ellofemoral angle (LPA), the lateral patellar tilt (LPT), and the late ral patellar displacement (LPD) were measured by two different investi gators on different occasions, and the agreement of these indices betw een CT and AR was evaluated according to Bland and Altman's statistica l method. LPT and LPD obtained by AR were more reliable and repeatable than those obtained by CT. The quadriceps muscle contraction exacerba tes PFM indices significantly with the knees in full extension (P=0.00 01). LPT and LPD measured at 20 degrees AR show reliably the two patho logical components (the patellar tilt and the lateral patellar displac ement) of PFM which are necessary for diagnosis and treatment planning . CT with quadriceps contraction is better in qualitative screening of more subtle cases of PFM.