Correlation between trochlear dysplasia and the notch index.

purpose. To evaluate the correlation between trochlear dysplasia and the notch index. Methods. Magnetic resonance images (MRI) of 95 knees in 54 male and 36 female patients aged 4 to 74 (mean, 28) years were reviewed by 2 musculoskeletal radiologists. Standard MRI sequences were used. Based on the Dejour classification of trochlear dysplasia, the knees were classified into normal or types A, B, C, and D. A notch index of <0.2 was considered narrow. Normal knees and knees with trochlear dysplasia were compared. results. 60 of the 95 knees had trochlear dysplasia, of which 39 were Dejour type A, 13 were type B, 7 were type C, and one was type D. Dejour types B, C, and D were combined as non-type A. Inter-observer agreement in assessing the notch index was good (Kappa=0.6). The mean notch indices in normal knees and knees with trochlear dysplasia were comparable (0.161 vs. 0.157, p=0.18), as were in Dejour type A and non-type A knees (0.154 vs. 0.160, p=0.54) and