Underestimation of pelvic osteolysis: the value of the iliac oblique radiograph.

Periacetabular osteolysis is recognized as a complication of cementless total hip arthroplasty. Routine follow-up radiographs are recommended by most joint reconstructive surgeons to detect osteolytic lesions that may remain asymptomatic. These studies usually consist of an anteroposterior (AP) pelvic and lateral radiograph of the hip. Three male cadaver pelves were used to evaluate whether a routine AP pelvic radiograph was adequate to show certain osteolytic lesions. This study involved creation of progressively enlarging defects simulating an osteolytic lesion of the posterior wall. The extent of involvement of the lesion as shown by an AP pelvic radiograph and iliac oblique views was then compared. By the time the posterior column lesion could be estimated to the same extent on both the AP pelvic and iliac oblique radiographs, the lesion had become uncontained in the posterior medial direction. The evaluation of pelvic osteolysis with biplanar imaging provides a 3-dimensional understanding of the lesion. This study shows the inadequacy of a single AP pelvic radiograph in showing and localizing periprosthetic osteolytic lesions in the posterior column.