Treatment of massive acetabular bone loss and pelvic discontinuity with a custom triflange component and ilio-sacral fixation based on preoperative CT templating. A report of 2 cases.

Revision rates for total hip arthroplasty are increasing and pelvic discontinuity is estimated to be present in 1% to 5% (Berry). Discontinuity is defined as a separation of the cephalad portion of the pelvis from the caudad portion (AAOS Type IV defects). This results from bone loss secondary to osteolysis, infection, fracture, or mechanical loosening. The goals of revision surgery in this setting are to obtain secure fixation of the acetabular component with or without union of the discontinuity. Many methods exist for treating this problem. Results with allograft and cage fixation have generally been poor (Berry, Hansen). More favourable outcomes have been reported using either a cup cage technique or custom triflange (Gross, Christie). The custom Triflange component is designed based on preoperative imaging with CT scan to manufacture a custom titanium implant to address the patient's specific bone loss pattern and obtain secure fixation in the ilium, pubis, and ischium. However, we have encountered cases of acetabular discontinuity with massive pelvic bone loss in which bone stock in the ilium was insufficient to provide support for proximal fixation of a conventional custom triflange component. Currently in the trauma patient population posterior pelvic ring disruptions are being treated with ilio-sacral screw fixation. The sacrum provides a source of secure bony fixation for these injuries. We report on 2 patients with pelvic discontinuity and massive bone loss using a technique to obtain proximal fixation of a custom triflange component into the sacrum.