Anatomical risks of using supra-acetabular screws in percutaneous internal fixation of the acetabulum and pelvis

We conducted a study to determine whether a lag screw placed percutaneously at the level of the pelvic brim for treatment of iliac fracture risks injury to the lateral femoral cutaneous nerve (LFCN). A 4-mm Kirschner wire (K-wire) was placed percutaneously into each of 8 human cadaveric hemipelvises (4 pelvises) at the level of the pelvic brim to represent the path of screw placement. Under fluoroscopic guidance, each K-wire was advanced from the anteroinferior iliac spine toward the posterior iliac crest. Cadavers were dissected at study end. Proximity of the LFCN to the percutaneously inserted K-wire was the main outcome measured. In 4 of the 8 hemipelvises, the LFCN was disrupted; in 3 hemipelvises, it was within 4 mm of the K-wire; in the last hemipelvis, it was 23 mm away. LFCNs varied anatomically from 1 to 5 branches; disruptions occurred more in LFCNs with multiple branches than in those with 1 branch. The results suggest considerable risk for injury to the LFCN during percutaneous fixation of iliac and acetabular fractures using a percutaneous screw at the level of the pelvic brim.