The "Discoid Epiphysis"-An Uncommon Presentation of Legg-Calvé-Perthes Disease

Among a cohort of 402 children with Legg-Calvé-Perthes disease (LCPD), 32 children presented with sclerosis and severe collapse of the entire femoral epiphysis that closely resembled a discus.This study was undertaken to identify the characteristics of children with this form of a "discoid epiphysis," compare them with typical LCPD and ascertain the radiologic outcome of their hips when the disease healed.

Sequential radiographs of the children were studied to monitor disease evolution. Femoral epiphyseal extrusion was measured on the initial anteroposterior radiograph. Thirty-one of the 32 children were treated with a proximal femoral varus osteotomy and weight-bearing was deferred till the disease reached stage IIIb. The pattern of fragmentation of the epiphysis was noted and the Sphericity Deviation Score (SDS) was computed once the disease healed.

The mean age of children with a discoid epiphysis was 6.81±1.57 years at onset of symptoms while that of children with the typical presentation was 7.54±1.64 years (P<0.017). Perfusion magnetic resonance imaging scans of three children with a discoid epiphysis done in stage Ib of the disease showed that over 95% of the epiphysis was avascular. Femoral head extrusion was frequently present on the initial radiographs (mean Reimer's migration index 27.08±8.7; range: 6.4 to 42.55).In operated children with a discoid epiphysis, the disease evolved typically with fragmentation of the epiphysis followed by reconstitution. The height of the epiphysis was never restored; when the disease healed the mean epiphyseal height was 51.31±10.44% of the normal contralateral epiphysis as compared with 82.46±11.24% in children with typical LCPD (P<0.001).The SDS at healing of operated children with a discoid epiphysis was 14.95±10.86 while the SDS for operated children without a discoid epiphysis was 9.77±11.7 (P<0.019). However, the SDS of children with typical onset LCPD who had Catterall IV involvement and Herring C collapse was 15.25±15.19 (P=0.49 NS).

The outcome of treatment of children with a discoid epiphysis is comparable to that of children with typical onset LCPD with Catterall IV (whole-head involvement) and Herring C collapse of the lateral pillar. About a third of these children who undergo early surgical containment may have spherical heads when the disease heals.