Ideal screw positions for multiple screw fixation in femoral neck fractures - Study of proximal femur morphology in a Japanese population.

Background: Despite the fact that multiple screw fixation is a common option of surgical treatment for femoral neck fractures, there is a paucity of precise morphological study of the femoral neck. To identify appropriate positions and spacing of hip screws for multiple-screw femoral neck fracture fixation, proximal femur morphology in Japanese patients was studied.

Method: One hundred hips in fifty knee arthroplasty candidates were studied. Following full limb CT, defined slices were created and anatomical variables measured.

Result: The average neck-shaft angle was 126.5° and the distance from the subcapital line to the subchondral bone on a line parallel to the femoral neck axis (FNA) was approximately 25 mm at the superior and inferior; borders of the femoral neck. The FNA was shown to run anterior to the femoral axis (FA). The cross section of the femoral neck forms a reverse right triangle. The height and width of the neck medullary canal were equal (approximately 25 mm), with the posterior wall closer to the femoral axis than the anterior wall.

Conclusion: Based on these data, the anterior screw positioned just above the calcar femorale, 16 mm proximal and 27° anterior to the FA, and the posterior screw positioned 12 mm proximal and 5 mm posterior to the FA is recommended. For screws inserted with a fixed angle side-plate, ≤130° is recommended.