BACKGROUND: The indication of total hip arthroplasty (THA) has been increasing among older and more frail patients who possibly have suboptimal bone quality. Pelvic insufficiency fractures (PIF) are rarely observed after THA. The appropriate diagnosis of fracture location is crucial, but its symptoms are non-specific and radiographic abnormality is often subtle; thus, diagnosis can be challenging, particularly in case of concomitant fractures at multiple locations.

CASE REPORT: A 47-year-old woman with rheumatoid arthritis and ongoing long-term oral corticosteroid therapy had groin pain in her left hip, which gradually developed without traumatic events 2.5 years after THA. Follow-up radiographs revealed an ipsilateral inferior pubic ramus fracture and a contralateral ischium fracture. The acetabular component of THA was slightly shifted upward, but further diagnostic examination was not conducted at that time. The pain was improved temporarily, but subsequently worsened and made her return to the clinic 6 months later, and radiographs revealed a medial wall fracture and superomedial migration of the acetabular component. She required a 2-stage revision procedure with massive allograft. At 1 year after these procedures, the patient is able to walk without a walking aid and does not report groin pain or present signs of dislocation, and radiographs show no loosening of the implant.

CONCLUSIONS: This case highlights that medial wall post-THA PIF can occur along with pubic/ischial fractures, which mask the symptoms of the medial wall fracture. We also reviewed the current literature and discussed the diagnostic strategy to be applied when suspecting this rare injury.

Keywords: Arthritis, Rheumatoid, Arthroplasty, Replacement, Hip, Fractures, Stress, Osteoporosis, Acetabulum, Pelvis, Radiography