Major acetabular prosthetic protrusion following total hip arthroplasty: a case report of a reconstruction challenge.

Background: Acetabular protrusion is an acetabular defect caused by the shift of the femoral head through the pelvic bone. Because of bone loss, usual anatomical landmarks may be confusing or absent, leading to a particularly high demanding surgical reconstruction in case of total hip arthroplasty (THA) implantation, without adequate support of the acetabulum due to major acetabular defect. To our knowledge, no article has dealt with acetabular defects to this extent and associated femoral osteolysis, which we will attempt to do in this case report. That's why we would like to share this case in order to propose an interesting alternative for the management of these challenging pathologies. Case Description: We hereby present the case of a rare pattern of severe acetabular prosthetic protrusion through the pelvic ring on a 77-year-old patient without any trauma. He was surgically treated with acetabular metal augment and a wide femoral modular reconstruction prosthesis. An instability was revealed after 6 weeks, so he underwent an early surgical revision with a constraint cup, overwhelming the absence of abductor apparatus. After this, his recovery was complete and uneventful, with effective function of the reconstructed hip joint and adequate stability of the prosthesis. Conclusions: Although acetabular protrusion is a rare complication in total hip replacement patients, we would like to draw attention to the challenging nature of this complication, both in terms of initial assessment and surgical management. The described strategy showed effective function of the reconstructed hip joint and final adequate stability of the prosthesis despite the absence of a competent abductor apparatus.