Hr. Song et al., Relationship between lateral subluxation and widening of medial joint space in Legg-Calve-Perthes disease, J PED ORTH, 18(5), 1998, pp. 637-642
Fifty-five patients (61 affected hips and 49 unaffected hips) with Perthes
disease were reviewed to evaluate the relationship between widening of medi
al joint space and lateral subluxation of the femoral head in radiographs.
The components of the medial joint space were evaluated by using T-1, T-2,
proton, and Gd-enhanced T1WI magnetic resonance images (MRI). The widened m
edial joint space in radiographs was filled with overgrown cartilage at the
initial stage (27 hips) in MRI, with both overgrown cartilage and widened
true medial joint space at the fragmentation stage (23 hips) and widened tr
ue medial joint space at the healing stage (11 hips). Between affected hips
and unaffected hips, the mean difference of medial joint space in radiogra
phs between hips at the initial stage and at the fragmentation stage was 2
and 4.5 mm, respectively; the mean difference in percentage of lack of cove
rage of the femoral head between hips at the initial stage and at the fragm
entation stage was 3 and 15%, respectively. During the healing stage, widen
ing of the medial joint space decreased or normalized because of ossificati
on of overgrown cartilage despite the existence of lateral subluxation beca
use of coxa magna. We concluded that widening of the medial joint space may
be used as an index of lateral subluxation at only the fragmentation stage
in Perthes disease.