Treatment of Hip Osteoarthritis with Severe Acetabular Bone Defects by Total Hip Arthroplasty Using the Restoration GAP II Reinforcement Ring: A Case Report.

Introduction: Total hip arthroplasty (THA) in patients with severe acetabular bone defects remains technically demanding. Although favorable outcomes have been reported with Kerboull-type acetabular plates, the clinical results of the Restoration GAP II reinforcement ring (GAP II ring) have been inconsistent. We report a case of hip osteoarthritis with severe acetabular bone defects following rotational acetabular osteotomy, successfully treated with THA using the GAP II ring. Case Report: We report a case of an 80-year-old woman who underwent rotational acetabular osteotomy 20 years ago and subsequently developed hip osteoarthritis with severe acetabular bone defects that required acetabular reconstruction. Anatomical placement of the acetabular component and fixation with a cementless cup were deemed inapplicable due to the extent of the bone defects. Conclusion: Therefore, the Restoration GAP II reinforcement ring, which has multiple screw insertion points and customizable hook bending, was selected for reinforcement. Given the poor bone quality, autologous bone grafting was considered unsuitable, and bone cement was used to fill the defects. Total hip arthroplasty was successfully performed using the reinforcement ring, and the patient was allowed full weight-bearing ambulation from post-operative day 1.At 18 months after surgery, she reported no recurrence of pain or difficulties in walking. This case suggests that satisfactory outcomes can be achieved in cases with severe acetabular bone defects through the appropriate application of a reinforcement ring.