Subtalar Fusion Preparation: What Are We Really Doing? A Cadaver Study

Introduction. The open, lateral sinus tarsi approach is the most commonly used technique for subtalar arthrodesis. In this cadaver study, we measured the maximum joint surface area that could be denuded of cartilage and subchondral bone through this approach. Methods. Nine fresh frozen above-knee specimens were used. The subtalar joint was accessed through a lateral incision from the fibular malleolus distally over the sinus tarsi area to the level of the calcaneocuboid joint. Cartilage was removed from the anterior, middle, and posterior facets of the calcaneus and talus using an osteotome and/or curette. ImageJ was used to calculate the surface areas of undenuded cartilage. Results. No specimens were 100% denuded of cartilage on all 6 measured surfaces. The greatest percentages of unprepared surface area remained on the middle facet of the talus (18.66%) and the middle facet of the calcaneus (14.51%). The anterior facet of the talus was 100% denuded in 6 specimens, while the middle and posterior facets were 100% denuded in 3 specimens. The anterior facet of the calcaneus was also 100% denuded in 6 specimens, while the middle and posterior facets were 100% denuded in 3 and 4 specimens, respectively. The average total unprepared surface area per specimen was 8.67%. Conclusion. The lateral sinus tarsi approach provides adequate denudation of cartilage of the subtalar joint in most cases. Total percentage of unprepared joint surface may range from approximately 2% to 18%. Future clinical studies are warranted to assess whether this technique results in optimal union rates. Levels of Evidence:V, Cadaveric Study.