AVASCULAR NECROSIS AND THE PAVLIK HARNESS - THE INCIDENCE OF AVASCULAR NECROSIS IN 3 TYPES OF CONGENITAL DISLOCATION OF THE HIP AS CLASSIFIED BY ULTRASOUND

We analysed the incidence of avascular necrosis in 101 hips of 90 infa nts with congenital dislocation treated with the Pavlik harness and fo llowed up for more than one year. Using ultrasonography in the flexed- abducted position the hips were classified as type A when the femoral head was displaced posteriorly, but within the socket and making conta ct with the posterior inner wall of the acetabulum; type B when it was in contact with the posterior margin of the acetabulum, with its cent re at this level or anterior to it; and type C when it was displaced o ut of the socket,,vith its centre posterior to the posterior rim of th e acetabulum. Eighty-seven hips were reduced by the harness (86%), and seven of these developed avascular necrosis (8%). All 69 hips with ty pe-a dislocation were reduced, and only one (1.4%) showed slight avasc ular necrosis, Eighteen (78.3%) of 23 hips with type-B dislocation wer e reduced, and six developed avascular necrosis (33.3%), In one hip, t he femoral head was severely damaged, None of the nine hips with type- C dislocation was reduced in the harness, We conclude that the Pavlik harness is indicated for type-A, but not for type-B or type-C dislocat ions.