Iatrogenic superior gluteal nerve stretch in surgical fixation of acetabular fractures through a Kocher-Langenbeck approach: a cadaveric study

OBJECTIVES: Fixation of posterior column fractures through a Kocher‒Langenbeck approach requires retraction of the gluteus medius and minimus and, therefore, the superior gluteal nerve (SGN). Iatrogenic nerve injury is a concern that may result in hip abductor weakness and altered gait patterns. The purpose of this study was to measure the amount of stretch to the SGN relative to common placement of a retractor during a posterior approach to the acetabulum for fracture fixation. METHODS: An IRB-approved cadaveric study was performed. The Kocher-Langenbeck approach was performed on ten hips from five cadaveric donors. The superior gluteal nerve was reproducibly identified and isolated, exiting the greater sciatic notch (GSN) and traversing between the gluteus minimus and medius. The length of the nerve was measured with a caliper between the GSN and its insertion into the gluteus medius, along its longest segment. An acetabular retractor was placed anterior to the gluteal pillar, and the length of the SGN was measured with the retractor positioned 30 and 60 degrees relative to the horizontal. The measurements were completed both with the leg in the neutral position and with the leg in 15 degrees of abduction. Interobserver reliability was measured. The percent change in the length of the SGN relative to retractor position was calculated. RESULTS: The SGN was consistently found exiting the most proximal aspect of the GSN. The length of the SGN from the GSN to the muscular insertion was 29.3 mm (+/- 7.4 mm). The nerve stretched 28% of its length at 30 degrees of retraction and 56.9% at 60 degrees of retraction. The nerve was stretched over a short segment and tethered at the level of the GSN. The intraclass correlation coefficient (ICC) was excellent between the two observers (0.92 [0.87-0.95]). Significant changes in the length of the nerve were found in four hips with the retractor at 30 degrees and all ten hips at 60 degrees. CONCLUSIONS: The superior gluteal nerve is subjected to significant stretching during anterior retraction of the gluteal muscles during acetabular fracture fixation through a Kocher-Langenbeck approach. A clinical study with electrodiagnostic studies and gait analysis is needed to determine whether iatrogenic nerve stretch is consequential.