The Hindfoot Nail Entry Point

Background: Tibiotalocalcaneal arthrodesis is a procedure for pain relief and deformity correction by creating a rigid fusion of tibiotalar and subtalar joints. Hindfoot nails have been identified as one of the most common current methods used in the procedure. Establishing the correct entry point for a hindfoot nail is critical to ensure acceptable hindfoot alignment which is physiologically known to be associated with valgus. Our research aims to use a cadaveric model to assess the anatomic angle to be considered in potential hindfoot nails.

Materials and methods: 6 fresh-frozen transtibial amputated cadaveric specimens, with no known prior deformity, surgical intervention, or trauma, were evaluated. Two 6.5-mm guide pins were advanced in antegrade and retrograde directions till a point of intersection was detected by fluoroscopy. The hindfoot angle was measured in every specimen.

Results: The hindfoot angle, in degrees, for each of the six cadaveric specimens was as follows: 7.1, 6.8, 5.3, 10.1, 6.3, and 8.1. The mean hindfoot angle for the six specimens was 7.3 +/- 1.6 degrees.

Conclusion: Our analysis shows that a hindfoot nail with approximately 7.3 degrees of valgus will enhance positioning of the nail inside calcaneus, talus, and distal tibia. This angle permits axial loading through the nail which is the most biomechanically stable structure.