Subcapital Fracture with Avascular Necrosis of the Whole Femoral Head After Fixation of an Intertrochanteric Fracture: A Case Report.

INTRODUCTION: Subcapital fractures following internal fixation of an intertrochanteric fracture are relatively rare. It has been reported that these fractures are caused by improper placement of implants, osteoporosis, and any trauma episode. We report a rare case of subcapsular fracture possibly caused by whole femoral head necrosis following intertrochanteric fracture treatment. CASE REPORT: An 88-year-old woman fell and sustained an intertrochanteric fracture of the left femur. She was treated with a short femoral nail (SFN) and 3 months after the surgery, bone union was observed. One year after the internal fixation of the intertrochanteric fracture, she complained of the left hip joint pain without any trauma, and the X-ray showed a subcapital fracture of the femur. She underwent nail removal and was treated with a bipolar hemiarthroplasty. Magnetic resonance imaging showed a change in the signal intensity of the entire head, and pathological findings revealed osteonecrosis. Normally, the reaction of bone resorption occurs below the necrosis area. We believe that the avascular necrosis (AVN) of the whole femoral head made the subcapital area fragile, resulting in a subcapital fracture. CONCLUSIONS: We should consider AVN of the whole femoral head as a potential cause of subcapital fracture after SFN fixation of intertrochanteric fractures.