Diffusion-weighted MRI reveals epiphyseal and metaphyseal abnormalities in Legg-Calvé-Perthes disease: a pilot study

Abstract

Background: Legg-Calvé-Perthes disease (LCP) is thought to be associated with ischemic events in the femoral head. However, the types and patterns of reperfusion after these ischemic events are unclear.

Purposes: We therefore determined whether (1) there would be any age-related diffusion changes; (2) diffusion-weighted MR imaging would reveal ischemic damage; and (3) diffusion changes are correlated with prognostic MR findings in patients with LCP.

Methods: We prospectively performed conventional, perfusion, and diffusion-weighted MR imaging studies in 17 children with unilateral LCP. We then measured the apparent diffusion coefficient (ADC) values in the epiphysis and the metaphysis, and compared them with those of the contralateral normal side. Based on perfusion MR imaging, we assessed reperfusion to the epiphysis as either periphyseal or transphyseal. We studied T2-signal intensity changes in the metaphysis and the presence of focal physeal irregularity. We correlated diffusion changes with reperfusion to the epiphysis, T2-signal intensity change, and focal physeal irregularity.

Results: Normal diffusion decreased with age. In LCP hips, epiphyseal diffusion increased early and remained elevated through the healing stage. Six of the 17 patients who had a metaphyseal ADC greater than 50% over the normal side had 13 times greater odds of having an association with transphyseal reperfusion to the epiphysis. The increase of metaphyseal ADC also was associated with an increased T2-signal intensity in the metaphysis and presence of focal physeal irregularity.

Conclusions: Diffusion-weighted MR imaging can be used as a complimentary modality to evaluate ischemic tissue damage with a potential prognostic value in patients with LCP.

Fig. 1

Epiphyseal ADC values were obtained from a circular region of interest (ROI) with a diameter of 5 mm set in the center of the epiphyseal ossification center. Metaphyseal ADC values were obtained from another identical region in the subphyseal metaphysis, approximately 1 cm distal from the physis.

Fig. 2

The graph shows normal diffusion changes with age in the epiphysis and the metaphysis (ADC - apparent diffusion coefficient).

Fig. 3

The graph shows diffusion changes in the epiphysis with radiographic stages of LCP. The dot plot shows that epiphyseal ADC remains increased at least until the healing stage in all cases (ADC - apparent diffusion coefficient; 1 - initial stage; 2 - fragmentation stage; 3 - healing stage; 4 - residual stage).

Fig. 4

The graph shows diffusion changes in the metaphysis with radiographic stages of LCP (ADC - apparent diffusion coefficient; 1 - initial stage; 2 - fragmentation stage; 3 - healing stage; 4 - residual stage).

Fig. 5A–D

The MR images of a 2-year 11-month-old boy with LCP of the left hip are shown. The (A) ADC map and a (B) gadolinium enhanced fat-suppressed T1-weighted image of the right hip (control side) were compared with a (C) gadolinium enhanced fat-suppressed T1-weighted image of the left hip showing periphyseal reperfusion (arrows) in the epiphysis and the (D) ADC map of the left hip showing increased diffusion to the epiphysis.

Fig. 6A–D

The MR images of a 6-year-old boy with LCP of the left hip are shown. The (A) ADC map and a (B) gadolinium enhanced fat-suppressed T1-weighted image of the right hip (control side) were compared with a (C) gadolinium enhanced fat-suppressed T1-weighted image of the left hip showing transphyseal reperfusion (arrows) to the epiphysis and (D) the ADC map of the left hip showing increased diffusion to the epiphysis and the metaphysis.