Factors affecting the incidence of hip dislocation in cerebral palsy.

We have studied the natural history of spontaneous dislocation of the hip in cerebral palsy, with particular reference to the pattern of neurological involvement. In patients with bilateral hemiplegia and severe involvement of the upper limbs the incidence of dislocation was very high (59%), while in those with diplegia and little involvement of the upper limbs, only 6.5% were affected. There was no evidence of dysplasia or instability of the hip in any of the patients with unilateral hemiplegia. A strong correlation was found between the stability of the hip and the patients' ability to walk. These findings have a bearing on clinical surveillance and also on the indications for prophylactic surgery.