Patellar Height Measurements on Radiograph and Magnetic Resonance Imaging in Patellar Instability and Control Patients

J Knee Surg DOI: 10.1055/s-0037-1599249Insall–Salvati (IS) ratio, modified IS ratio (mIS), Caton–Deschamps (CD) index, and Blackburne–Peel (BP) index are patellar height measurements commonly made on lateral radiographs (XRs) in patients with patellofemoral instability. More recently, magnetic resonance imaging (MRI) has been used as an additional imaging modality to measure patellar height. However, different imaging modalities have not been previously compared for all of these measurements. First, to compare the patellar height measurements of IS, mIS, CD, and BP on XR and MRI in first-time lateral patellar dislocation (LPD) patients and a control population and, second, to evaluate for the effect of sex and skeletal maturity. All first-time LPD patients with both MRI and XR of the knee within 6 weeks of injury from 2008 to 2012 were included in the LPD group (n = 112). Patients without patellofemoral instability who underwent both MRI and XR of the knee served as controls (n = 129). Two independent observers measured patellar height. Mean values were compared among the radiographic modalities, sex, and skeletal maturity status. Interobserver reliability was assessed using intraclass correlation coefficients (ICCs). Patellar height in the LPD group measured greater on MRI than on XR for all four patellar height ratios (IS: 0.11; mIS: 0.07; CD: 0.18; BP: 0.08). In controls, MRI also demonstrated higher readings than XR on two indices (CD: 0.17; BP: 0.16). Skele...

Source: Journal of Knee Surgery - March 9, 2017 Category: Orthopaedics Authors: Yue, R. Alexander Arendt, Elizabeth A. Tompkins, Marc A. Tags: Original Article Source Type: research