False Femoral Neck Fracture Detected during Shaft Nailing: A Mach Band Effect
A 57-year-old man sustained a motor vehicle accident and was transferred to our ER for femoral shaft comminuted fractures on the left side. We planned closed reduction and internal fixation with intramedullary nails for the left femoral shaft fracture. In the operating room, the patient was placed on a fracture table under general anesthesia. A skin incision was made proximal to the tip of the greater trochanter about 5 centimeters. A 3.2-mm guide pin was inserted at the tip of the greater trochanter. After trochanteric reaming along the 3.2-mm guide pin, a ball-tip guide was introduced into the medullary cavity of the proximal and distal fragments after reduction. A femoral nail (greater trochanter starting nail, 12 mm in diameter, 40 cm in length) was introduced after reaming a hole to 13 mm. The nail was inserted uneventfully without excessive force. At that time, we identified a vertical radiolucent line at the femoral neck, which was thought to be further displacement of a hidden silent fracture or an iatrogenic fracture that developed during nail insertion (). Consequently, we decided to perform reconstructive femoral nailing. We inserted two 6.0-mm partially threaded cancellous screws into the femoral neck and head. Afterwards, we observed that the radiolucent line at the femoral neck had decreased in size. Three distal interlocking screws were then inserted, and a nail cap was applied.\nPostoperative hip imaging failed to show the femoral neck fracture that we saw in the operating room. Fourteen days after surgery, we took a CT scan of the proximal femur in order to analyze the radiolucent line observed during intraoperative fluoroscopy; the femoral neck was confirmed as intact. Reversal of the fluoroscopic image taken in the operating room showed a radiolucent line running from the femoral neck to the medial thigh ().