Session X - Pelvis
Risks to the Superior Gluteal Neurovascular Bundle during Percutaneous Iliosacral Screw Insertion: An Anatomical Cadaver Study
David A. Coons, DO1; Cory A. Collinge, MD2;
Introduction: Iliosacral screws are an increasingly popular method for treating complicated injuries of the pelvis. It is well-recognized that this technique entails some potentially disabling complications, including damage to vessels and sacral nerves. The recommended insertion site for iliosacral screws lies along the posterior ilium between the greater sciatic notch and the iliac crest. The anatomy of the superior gluteal nerve and vessels (SGNAV) has been well described along the outer aspect of the posterior ilium. Although injury to the SGNAV has been reported during pelvic surgery, including the insertion of iliosacral screws, little or no information is available as to the risks to the SGNAV. The purpose of this study was to assess the risks of injury and proximity of percutaneously inserted iliosacral screws to the SGNAV by using a cadaver model.
Methods: Percutaneous iliosacral screws were placed on the right and left sides into the first sacral body of 29 supine cadavers (for a total of 58 sides) with use of fluoroscopic guidance. The superior gluteal neurovascular anatomy was then studied via a posterior dissection. Injury to the neurovascular bundle was noted if it occurred, and the distance between the screw head and the neurovascular bundle was measured with fine calipers. Distances from the screw head to the crista glutea, greater sciatic notch, and iliac crest were also measured.
Results: The anatomy of the SGNAV after they exit the greater sciatic notch was mostly consistent with prior descriptions. The superficial branch is the first major branch and diverges in a superior and superficial direction into the gluteus maximus. The main bundle continues briefly and then bifurcates to form deep superior and deep inferior branches of the SGNAV. The superior branch of the SGNAV then follows a path along the lateral ilium to supply much of the gluteus medius and the gluteus minimus. Ten of 58 (18%) iliosacral screws caused injury to the superior branch of the SGNAV; eight bundles were impaled and two others were partly entrapped between the screw head and the ilium. The mean distance from the head of the iliosacral screws to the deep superior branches of the SGNAV was 9.1 mm (±6.8 mm). The mean distances from the screw head to the crista glutea, sciatic notch, and iliac crest were 19.5 mm (±4.9 mm), 33.0 mm (±6.4 mm) and 50.3 mm (±4.6 mm). All of the 10 screws that caused SGNAV injury were well-placed and within the "desired" area of insertion.
Conclusions: The deep superior branch of the SGNAV, which provides major blood and nerve supply to the gluteus medius and gluteus minimus, is at risk during the percutaneous placement of iliosacral screws, even when "well placed." The clinical effects of these injuries remain poorly defined.