Minimally Invasive Calcaneal Osteotomy: Does the Shannon Burr Endanger the Neurovascular Structures? A Cadaveric Study.

Calcaneal osteotomies are used to correct hindfoot alignment. Traditional open procedures have been plagued with complications. Various minimally invasive techniques have been described but are laborious and time-consuming. A percutaneous technique using a side cutting "Shannon" burr offers a simple and reliable alternative; however, little evidence is available to address the safety concerns. The aim of the present study was to quantify the risk posed to the medial and lateral neurovascular structures using this technique. The study was performed at the anatomy department, University of Sussex, using 13 fresh-frozen, below-the-knee cadaveric specimens during a training session held by WG Healthcare UK, Ltd. (Letchworth, Herts). The participants were 11 consultant orthopedic surgeons, who were inexperienced in minimally invasive surgery, and 2 demonstrators. Each performed a chevron calcaneal osteotomy using a Shannon burr by way of a lateral percutaneous approach under fluoroscopic guidance. The authors subsequently dissected the specimens to identify the neurovascular structures, describe their anatomic relations and proximity to the burr, and note any damage incurred. No evidence was found of significant neurovascular injury. Two very small proximal branches of the sural nerve were transected, the nerve itself passing safely 9 to 21 mm anterosuperior to the entry point. The medial neurovascular bundle crossed the path of the osteotomy in 4 specimens but was protected by the medial head of the quadratus plantae muscle. In conclusion, the Shannon burr for calcaneal osteotomy has the potential to minimize the surgical morbidity and maximize surgical efficiency without compromising safety in all patients with normal anatomy of the quadratus plantae muscle.