OTA 1997 Posters - Femur Fractures

Risks of AP Locking Screws in the Proximal Femur

Paul Tornetta, III, MD, Joseph Riina, MD, Christopher Ritter

University Hospital, Brooklyn, New York, USA

Introduction: Retrograde nailing has become a more popular technique in the treatment of femoral shaft fractures. Many of these devices are designed with AP locking holes in the hip region. The risks of placing screws in this region has not, however, been examined.

Purpose: To evaluate the anatomic structures at risk from the placement of anterior to posterior locking screws in the proximal femur.

Materials and Methods: Sixty cadaveric thighs were used for the study. Dissections were performed about the anterior aspect of the femur from above the greater trochanter to the mid-thigh. After the skin was removed, the femoral triangle was identified. The location of the femoral artery and its branches and the femoral nerve and its branches were recorded. For structures never lying over the femur the closest distance to the femur was noted. For structures crossing the femur, the distance from the piriformis fossa to the structure in the center of the femur was recorded.

Results: The femoral nerve was always greater than 1 cm medial to the most medial aspect of the femur. The branches of the femoral artery were located greater than 10 cm distal to the fossa. Multiple branches of the femoral nerve crossed the femur in the proximal half of the bone. The average number of branches was 6.6 ± 2. The first branch crossed the femur 3.8 ± 1.4 mm distal to the fossa. The position of the lesser trochanter was difficult to precisely measure, but averaged 6 cm from the fossa. The number of nerve branches crossing the femur proximal to the lesser trochanter was one in 3, two in 29, three in 8, and four in 2 specimens. These branches may all be at risk from an anteroposterior screw. The number and frequency of nerve branches and arterial branches distal to the lesser trochanter was much greater than those proximal to the trochanter.

Discussion: This study identifies the anatomic risks of anterior to posterior locking screws in the proximal femur. The femoral artery is safe as it lies medial to the femur, branches of the femoral artery are rare within 10 cm of the piriformis fossa and are safe. Branches of the femoral nerve were most at risk as they cross the femur in the proximal half of the bone.

Conclusions: Anterior to posterior locking screws are safest if the screw is placed at or above the level of the lesser trochanter. A blunt dissection, cannulated system, or oscillating drill may decrease the risk to the branches of the femoral nerve.