Dual Mobility Total Hip Arthroplasty for Recurrent Dislocation After Femoral Neck Fracture in an Elderly Patient: A Case Report.

INTRODUCTION: Recurrent dislocation after bipolar hemiarthroplasty for femoral neck fracture is a challenging complication, particularly in elderly patients with risk factors for instability such as cognitive impairment, soft-tissue insufficiency, and muscle weakness. Dual mobility total hip arthroplasty has been increasingly used to improve hip stability in patients at high risk of dislocation.

CASE REPORT: An 83-year-old woman with dementia sustained a Garden type III femoral neck fracture and underwent bipolar hemiarthroplasty through a posterior approach. Three months after the initial surgery, she developed posterior dislocation of the hip. Thereafter, posterior dislocation occurred almost daily despite repeated closed reductions. She had no Parkinson's disease or paralysis. Due to severe recurrent instability, conversion total hip arthroplasty was performed through a posterior approach using a dual mobility acetabular component. The femoral stem was well fixed and was retained. A Zimmer Biomet G7 dual mobility cup was implanted with an inclination angle of 49° and an anteversion angle of 19°. At the 2-year follow-up, no redislocation had occurred. The patient was able to walk with a cane, and the Harris Hip Score was 80 points. Written informed consent for publication was obtained from the patient and her family.

CONCLUSION: Dual mobility total hip arthroplasty may be an effective stem-retaining salvage option for severe recurrent posterior dislocation after bipolar hemiarthroplasty for femoral neck fracture in elderly patients with cognitive impairment. The clinical significance of this case is that durable stability was achieved without femoral stem revision in a patient with almost daily posterior dislocation, supporting dual mobility acetabular reconstruction as a practical option when the femoral component is well fixed and instability is multifactorial.