Spontaneous dissociation of bipolar hip hemiarthroplasty in a patient with nerve palsy: A case report and review of the literature

INTRODUCTION: Dislocation after bipolar hemiarthroplasty is a common complication but dissociation of the prosthesis is rare. There are some reports of bipolar hemiarthroplasty dissociation at the inner head and outer shell. However, there are limited reports on acute spontaneous dissociation of the head and neck at the taper interface in bipolar hemiarthroplasty. PRESENTATION OF CASE: A 65-year-old female had cemented bipolar hemi hip replacement after fixation failure of a dynamic hip screw. She had left lower limb weakness for ten years after previous spinal surgery. At the sixth week of postoperation, the patient had dissociation of the components of the bipolar hemiarthroplasty at the femoral head and neck junction. The patient had open reduction and femoral head revision. There was no re-dislocation at one-year follow-up. DISCUSSION: Dissociation of bipolar hemiarthroplasty is a complex complication that can happen from the modularity of the implant. This condition requires operative treatment. The mechanism and cause of failure should be identified before the operation. CONCLUSION: To prevent this condition, preoperative planning and proper techniques should be done as an index procedure. In the case of marked shortening of the limb after an operation in patients with lower limb muscle weakness, we hypothesize that early full weight bearing with immediate use of a shoe lift might help prevent this condition.