Radiologic classification of posterior dislocations of the hip: refinements and pitfalls.

Seventeen traumatic hip dislocations seen during a 15-month period were evaluated. In 10 of the 14 cases of posterior hip dislocation, the final Thompson-Epstein classification differed from the initial radiographic classification. Dislocations of the hip often result in radiographically obscure femoral head and acetabular damage. High quality radiographs with oblique and coned-down views are of substantial aid in evaluating the dislocated hip. After closed reduction of a dislocated hip, further views and tomography are helpful but diagnostic pitfalls exist. A persistently widened hip joint, even with negative plain films and tomography, indicates possible intra-osteochondral debris or incompletely reduced femoral head fragments.