Atypical insufficiency fracture of the femur following prolonged bisphosphonate use is well described. Regardless of the cause, insufficiency fracture of the acetabulum is extremely rare, and no reports have described insufficiency fractures of the acetabulum that are associated with prolonged bisphosphonate use. This report demonstrates the possibility of insufficiency fracture at the acetabulum following long-term alendronate use and the necessity of particular care in managing insufficiency fractures in "frozen" bone. We describe two cases of insufficiency fracture of the acetabulum following 6 years of alendronate use. Given the patients' medical histories and bone biopsy findings, these insufficiency fractures were thought to be attributable to alendronate use. One case involved the left hip and the presence of pelvic fractures on the opposite side. The patient was treated using cementless total hip arthroplasty (THA), which failed 1 year after surgery. The hip was revised with a massive bone graft and a supportive wire mesh. The other case was managed via THA with a Ganz reinforcement ring due to concerns regarding the use of a cementless implant.
Keywords: Acetabulum; Alendronate; Insufficiency fracture; Total hip replacement.