Medial Structures at Risk During Sinus Tarsi Approach for Fixation of Sustentaculum Tali Fractures: A Cadaveric Study

Abstract

Category: Hindfoot; Trauma; Other Introduction/Purpose: Calcaneal fractures are a common injury with potential for concomitant involvement of the sustentaculum tali. Common surgical repair involves a sinus tarsi approach with placement of a lag screw from lateral to medial. There is no current study that focuses on the potential damage to the medial structures after screw placement. The goal of this paper was to describe the incidence in which medial structures were damaged using a sinus tarsi approach for lateral to medial screw fixation of the sustentaculum tali. Methods: Seven fresh-frozen below-the-knee cadaver specimens were used for the present anatomic dissection study. Prior to investigations, specimens were inspected with fluoroscopic radiographs for any pathology or prior operational intervention Each specimen underwent screw placement using the sinus tarsi approach. Medial dissection of the calcaneus was performed after screw placement to determine the proximity of the anatomical structures of interest to the inserted hardware. The four anatomical structures of interest were the tibialis posterior tendon, flexor hallucis longus, flexor digitorum longus, and posterior neurovascular bundle. Distance from the 4.0 mm screw to the previously mentioned anatomic structures was measured with a scientific ruler and recorded to the nearest millimeter. The mean, standard deviation, and range for distances were calculated for all structures. Analysis of variance (ANOVA) was used to determine statistical significance. Results: The average patient age, height, and weight were 79.3 years, 5 feet 4 inches, and 127 lbs respectively. The primary outcome of interest was the longitudinal distance between the medial aspect of the screw to the anatomical structures of interest. On average, the posterior neurovascular bundle had the closest proximity to the medial aspect of the screw for all seven specimens with a mean distance of 6.4 mm. The second closest structure was the FHL with a mean distance of 7 mm, followed by the FDL and tibialis posterior tendon, with mean distances of 9.9 mm and 13.9 mm respectively. The posterior neurovascular bundle was hit by the screw on one occasion, whereas the hardware contacted the FDL on two separate occasions. The screw was placed through the FDL in one of the two occasions; however, the FDL was not transected or ruptured. Conclusion: This study sheds more light on the potential risks to medial structures when placing the sustentacular screw during open reduction and internal fixation of displaced intraarticular calcaneal fractures. We urge the orthopedic surgeon to exercise extreme caution when performing this critical step of the procedure to minimize avoidable injury to structures of importance that may increase the morbidity of the patient.