Introduction:
Cannulated screw fixation is a common technique employed for the closed reduction and fixation of minimally or non-displaced neck of femur (NOF) fractures. A rare but potentially devastating complication is a peri-implant subtrochanteric fracture. Given the possibility of dealing with two potentially unstable fractures in close proximity from an incomplete union of the femoral neck, surgical fixation must be carefully planned with the option of retaining the existing cancellous screws to maintain femoral neck stability. The authors describe a case of subtrochanteric fracture in a patient with an existing NOF fracture which was previously fixed with cancellous screw fixation and have provided our approach to such patients.
Case report:
The patient is a 73-year-old Chinese male with a previous cancellous screw fixation for an undisplaced NOF fracture 10 months before sustaining another fall resulting in a subtrochanteric fracture. Radiographs and computed tomography imaging revealed a peri-implant subtrochanteric fracture with fracture line originating distal to the inferior screw at the level of the lesser trochanter.The patient subsequently underwent a Trochanteric Fixation Nail-Advanced Proximal Femoral Nailing System (TFNA, Depuy Synthes) fixation of peri-implant subtrochanteric fracture. Two previous cancellous screws (superior-posterior and inferior-central) were first removed to allow the passage of the TFNA nail which just skirted the remaining superior-anterior screw.Postoperatively, the patient was allowed full weight-bearing with the patient managing to ambulate with a roller frame support on the immediate 1stpost-operative day. The subsequent progress was uneventful and at the final follow-up 6-month postoperatively, X-ray showed complete bony union and the patient is pain free and walking independently.
Conclusion:
Peri-implant subtrochanteric fractures following NOF fractures treated with cancellous screws are surgically challenging. A robust system of evaluating such fractures and decision-making aids perioperative planning. An intimate understanding of implant geometries and basic science principles can significantly help in difficult cases and may reduce the likelihood of intraoperative difficulties and complications. Further large-scale studies are required to evaluate the validity of the approach we have proposed.