Background: This cadaveric study evaluated the risk of injury to the superior gluteal nerve when a proximal incision site is used for insertion of an antegrade, reamed femoral intramedullary nail into the piriformis fossa. Based on prior anatomical studies, our hypothesis is that the use of a proximal incision site for intramedullary nail insertion will consistently injure the superior gluteal nerve.
Methods: A reamed femoral intramedullary nail was inserted through a piriformis fossa entry site in six pairs of fresh-frozen cadaver femora. The specimens were randomized to two groups: reaming of the femoral canal with or without a protective sleeve. Damage to the superior gluteal nerve was evaluated by means of layered dissection of specimens. Damage to any part(s) of the superior gluteal nerve was recorded, and the distances between the path of the instrumentation and nail and the branches of the superior gluteal nerve were measured.
Results: A "spray" nerve pattern of the superior gluteal nerve was present in all twelve specimens. The average distance and standard deviation between the most superior branch of the superior gluteal nerve and the instrumentation and nail path was 17.75 ± 8.58 mm. The average distance between the most inferior branch of the superior gluteal nerve and the instrumentation and nail path was 22.39 ± 10.52 mm. There were no significant differences between the two groups. There were no injuries to any part of the superior gluteal nerve regardless of whether or not a protective sleeve was used.
Conclusions: This anatomic study demonstrated that the superior gluteal nerve is not at risk for injury when a proximal incision site is used to place a reamed intramedullary nail into the piriformis fossa.