Percutaneous retrograde posterior column acetabular fixation: is the sciatic nerve safe? A cadaveric study.

OBJECTIVES: The purpose of this cadaveric study was to determine the proximity of the neurologic structures to the path of the screw inserted percutaneously into the ischial tuberosity.

DESIGN: Cadaver study.

INTERVENTION: Ten screws were inserted in 10 limbs (5 cadavers) under fluoroscopic guidance. Dissection was then performed to expose the head of the screw and was extended laterally to expose the sciatic nerve, the posterior cutaneous nerve of the thigh, and its inferior cluneal branches.

MAIN OUTCOME MEASURE: The distance from the screw head to the sciatic nerve, posterior cutaneous nerve of the thigh, and the inferior cluneal nerves.

RESULTS: The distance from the center of the screw head to the sciatic nerve averaged 58 mm (range, 40-70 mm). The average distance between the screw head and the posterior cutaneous nerve of the thigh was 42 mm (range, 30-60 mm). The inferior cluneal branches were the closest to the path of the screw with an average distance of 3.5 mm in 6 specimens (range, 1-6 mm) and were injured by the screw in 3 and could not be located in another specimen.

CONCLUSIONS: The sciatic nerve and the posterior cutaneous nerve of the thigh appear to be safe during retrograde percutaneous screw fixation of a posterior column acetabular fracture through a central entry point in the ischial tuberosity. However, the inferior cluneal nerves that are responsible for the cutaneous sensitivity of the lower half of the gluteal region are at risk of injury.