Introduction: Metal-on-metal hip resurfacing arthroplasty is one option for young and active patients with advanced hip disease. Intraoperative or immediate postoperative femoral neck fractures complicating a metal-on-metal hip resurfacing is a well described complication as a result of neck notching and stress shielding of the femoral head. The literature contains very little evidences on the conservative mode of treatment for peri-prosthetic fractures following the index operation with a favourable and an unfavourable outcome. We report a case of femoral neck fracture incurred three months after metal-on-metal hip resurfacing resulting in a varus malunion.

Case report: A 55 year old lady underwent metal-on-metal surface hip replacement for advanced osteoarthritis of the left hip. The implants used were Cormet 2000 uncemented 50mm dual coated cup and cemented 44mm femoral head. Intraoperative bone quality was good and no technical difficulties were encountered. She was admitted three months later with a painful left hip after sustaining a fall. The radiograph confirmed left periprosthetic femoral neck fracture with resurfacing prosthesis in situ. She was scheduled for elective revision surgery of the femoral component. The patient elected to go home with the intention of getting readmitted. Initially lost to follow-up, she self referred after 30 months of her fracture with shortening and persistent painful limp. The clinical examination revealed 1.5 cm of true limb shortening with restricted terminal range of abduction and rotational movements. The radiographs revealed a varus malunited fracture with proximal migration of greater trochanter. The acetabular component was well fixed in situ. She is awaiting revision surgery by conversion to conventional total hip arthroplasty.

Conclusion: We report the first case of a malunited femoral neck fracture following metal-on-metal hip resurfacing operation. Femoral neck fractures can heal in these cases but poor compliance and resultant failure to closely observe the patient may have contributed to such an unfavourable outcome. These complications may be prevented by increased compliance and communication with the patients. At the same time, the hospital management and professional staff should be aware of such potential problems to prevent their recurrence.