Comparison of Two Intramedullary Nails for Tibiotalocalcaneal Fusion: Anatomic and Radiographic Considerations

Abstract

Background: Retrograde intramedullary nailing is an established procedure for tibiotalocalcaneal arthrodesis. This study was conducted to see whether, and if so to what extent, nail design modifications would influence the risk to anatomic structures and the bony coverage of the nail base. Methods: Six pairs of thawed fresh-frozen cadaver legs received two different intramedullary nails (N1: straight nail, lateral-medial tip locking; N2: valgus-curved nail, medial-lateral tip locking) under simulated operative conditions. The specimens were dissected; distances between the at-risk structures and the hardware were measured. The hindfoot axis and the volume of the intracalcaneal nail portion were determined with CT. Results: At the plantar entry site, N2 was significantly farther from the flexor hallucis longus tendon ( p = 0.047), the medial plantar artery ( p = 0.026), and the lateral plantar nerve ( p = 0.026) than N1. The lateral-medial calcaneal locking screw of N1 damaged significantly more often the peroneus brevis tendon ( p = 0.03) than N2. The proximal tip-locking screw, N2, was significantly farther from the anterior tibial artery ( p = 0.075) and the deep ( p = 0.047) and superficial peroneal nerves ( p = 0.009) than N1; N1 was significantly farther from the great saphenous vein ( p = 0.075) than N2. The distal tip-locking screw, N1. damaged significantly more often the extensor digitorum longus ( p = 0.007), the anterior tibial artery( p = 0.04), and the deep and superficial peroneal nerves ( p = 0.03) than N2. CT did not show any significant changes in the hindfoot axis with either device; intracalcaneal nail volumes were similar. Conclusions: A curved nail can increase the distance to at-risk plantar structures. Medial-lateral nail-tip locking appears to have less risk to neurovascular structures. Clinical Relevance: Safer retrograde intramedullary nailing for tibiotalocalcaneal fusion requires knowledge of the structures at risk and appropriate operative technique.