The genesis of Perthesʼ disease: does it lie in hips with reduced ranges of movement?

: Noting that Perthes' disease is relatively common in Caucasian British children compared with black African children, this study was carried out to compare the range of hip movements in a series of 100 normal Ghanaian children and 182 normal British children, between 5 and 6 years of age. A significantly increased range of movement was found in the African group in all parameters, (P<0.001). The changes were even more marked when sex was taken into consideration, female children having a much bigger range of movement than the males in both racial groups. The unaffected hips in a series of 51 Caucasian children presenting with unilateral Perthes' disease were then analysed and were found to have a reduced range of movement compared with normal, in flexion, abduction, internal rotation in flexion and external rotation in extension (P<0.001). It is suggested that one of the reasons why some hips are vulnerable to Perthes' disease could be a preexisting restricted range of movement, which renders them more susceptible to strain injuries.