Evaluation of hip containment in legg-calvé-perthes disease: a comparison of ultrasound and magnetic resonance imaging.

BACKGROUND

To compare the performance of magnetic resonance imaging (MRI) and ultrasound (US) in the determination of head containment in hips with Legg-Calvé-Perthes disease (LCPD).

METHODS

In 26 children (22males, 4 females; age range 2.75 - 11.5 years; median 5.7 years) with LCPD classified as Catterall group III/IV, MRI and US were compared to assess the containment of the femoral head. A total of 63 individual examinations of LCPD and the healthy contralateral hip were evaluated and analyzed objectively by two independent observers. The containment was quantified by MRI with the "cartilage acetabulum-head-index" (CAHI) and by sonography with the "lateral cartilage distance" (LCD). For analyzing MRI and US data, the Pearson correlation coefficient was used and a probability value of less than 0.05 was assigned to indicate statistical significance.

RESULTS

US correlated well with MRI in the objective evaluation of the lateralization of the femoral head (CAHI: p = 0.01; LCD: p = 0.01). All hips showed a high agreement between the observers for the width of the femoral head/roof (Pearson: > 0.70) and for the LCD (Pearson: > 0.70). In comparison with the unaffected side, the loss of containment should be considered if CAHI is less than 73 % and LCD higher than 6.5 mm.

CONCLUSION

Hip sonography seems to be a reliable method for monitoring the containment of the femoral head in LCPD.