Due to its complexity and proximity to neurovascular structures the acetabulum is a very difficult skeletal area on which to operate7 This acetabular complexity makes the treatment for these lesions controversial.
Unlike the femur, a lesion involving the acetabulum can not be readily stabilized with an intramedullary fixation or replacement with a composite prosthesis. Because of this, and many other technical considerations, the external hemipelvectomy remained the standard of surgical therapy for large acetabular tumors until the 1970's.8
The external hemipelvectomy refers to amputation of the innominate bone (ilium, pubis, and ischium), including the ipsilateral extremity.
While this can provide cure of a primary neoplasm, the resection of the viable lower extremity is problematic. Not only is it disfiguring, but only younger, stronger patients are able to ambulate with a fitted prosthesis (see right). Older patients are often confined to a wheelchair or possibly bedridden. This procedure not only has functional problems, as it is also plagued with high infection rates.8,9
The shift towards limb-sparing procedures, including the internal hemipelvectomy, began in the 1970's. The internal hemipelvectomy entails complete or partial resection of the innominate bone with preservation of the limb. Although this maintains a viable limb, the patient is left with significant leg length discrepancy, 'flail hip' and instability. Rehabilitation times are prolonged and high rates of infection are seen.8,9
Lytic metastasis to left acetabulum.
Prosthesis after external hemipelvectomy (above and below).