The treatment of a posterior fracture-dislocation of the hip is strongly
influenced by the surgeon's assessment of stability of the hip after the
dislocation has been reduced. Stability is inversely related to the size of
the posterior acetabular fragment. Computed tomography was used to measure
the size of the fracture fragment in nine cadavera of adults. Progressive
increments of bone were removed from the posterior part of the acetabular
wall in sixteen hips. After each osteotomy, the hip was tested for
stability and was measured by computed tomography until it became unstable.
All hips from which less than 20 per cent of the posterior part of the
acetabular wall was removed were stable, while those from which more than
40 per cent was removed were unstable.