To evaluate diffusion MR imaging of the neck of the femur in Legg-Calve-Perthes disease (LCPD).

This is a prospective study in 27 children followed for unilateral LCPD. Forty-six MRIs were carried out with bilateral quantification of the apparent diffusion coefficient (ADC) of the neck of the femur. The intra- and inter-observer variability of the ADC measurements was evaluated. The association between the ADC and age as well as the healthy or pathological status of the neck of the femur and the Catterall classification were looked for.

Intra- and inter-observer reproducibility of the ADC measurements was excellent. A statistically significant negative correlation between the ADC of the healthy neck of the femur and age was found. There was a significant increase in the ADC of the pathological neck of the femur compared to the healthy neck. The ratio of the pathological neck ADC and the healthy neck ADC was significantly associated with the Catterall classification.

The quantification of the ADC of the neck of the femur is reproducible. This could be useful in the treatment of LCPD, where there is an early and significant increase in the ADC on the pathological side. This increase could have a prognostic value, as it is correlated with the Catterall classification.