Pathological changes in a case of Perthes' disease.

Although the number of affected femoral heads from human cases of coxa plana that have become available for direct study has been surprisingly small, the findings have been generally consistent with the view that the fundamental pathological process is one of infarction, necrosis and subsequent revascularisation of the epiphysis (Zemansky 1928 ; Gall and Bennett 1942; Mizuno, Hirayama, Kotani and Simazu 1966; Mattner 1968). Nevertheless, it is still not possible fully to account for the clinical features of coxa plana on the basis of a single vascular catastrophe. The outstanding difficulty is that of accounting for the slowness of the repair process, which may last for several years. In cases of known infarction of the capital epiphysis after trauma, recovery is often complete within a few months (Haliburton, Brockenshire and Barber 1961), and this is also the case after experimental infarction of the femoral head in animals (Kemp 1965, Salter 1966, Freeman and England 1969). The fact that there exists a form of coxa plana in dogs in which recovery is also slow (Lee and Fry 1969, Lee 1970) suggests that this cannot be accounted for simply by the small size of the femoral head. Because of this tardiness it seems likely that there is some factor which interferes secondarily with the repair process. Trueta (1968) suggested that mechanical collapse of the head might interfere with revascularisation and so retard recovery, but an alternative suggestion put forward more recently by Sanchis, Zahir and Freeman (1973), based on experimental evidence, is that the disease may represent the end-result of more than one episode of major infarction. The relevance of such observations to human coxa plana can be determined only by a study of material from the disease itself. There follows therefore a description of the findings in the femoral head of a boy aged nine years who had been treated for Perthes’ disease for two years before his accidental death from drowning. Special attention was paid to any evidence which might suggest that there had been interference with the process of revascularisation.