The Journal of Bone and Joint Surgery, Vol 66, Issue 4 479-489, Copyright © 1984 by Journal of Bone and Joint Surgery, Inc
Legg-Calve-Perthes disease. The prognostic significance of the subchondral fracture and a two-group classification of the femoral head involvement
RB Salter and GH Thompson
From previous experimental investigations of a model of Legg-Calve-Perthes
disease in young pigs, it was speculated that the early radiographic
phenomenon of the subchondral crescentic-shaped radiolucent line is a
pathological fracture and, furthermore, that this fracture initiates the
stage of resorption. Being painful, the fracture also heralds the clinical
onset of the disease. From these laboratory investigations, plus a
preliminary radiographic investigation in children, it has been observed
that only that portion of the epiphysis underlying the subchondral fracture
is resorbed. The radiographic investigation of 1,057 children (1,264
involved hips) with Legg-Calve-Perthes disease from four institutions
included 376 hips in which the diagnosis had been made early and the
subchondral fracture was detectable. In all of these hips the extent of the
subchondral fracture correlated precisely with the subsequent extent of
maximum resorption. Consequently, in the early stage of Legg-Calve-Perthes
disease the extent of the subchondral fracture is of prognostic
significance in predicting the eventual extent of involvement of the
femoral head. We propose a simple and practical two-group classification of
the extent of involvement of the femoral head: Group A (less than half of
the head) and Group B (more than half of the head). The classification can
be applied in the early stage of the disease when the subchondral fracture
is detectable as well as throughout the ensuing resorptive stage.
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