Sustentaculum Tali Screw Fixation Mode and Postoperative Foot-Ankle Function in Calcaneal Fractures

Background: Calcaneal fractures account for approximately 1% to 2% of all fractures and are the most common tarsal bone fractures, usually caused by high-energy injuries such as falls from height and motor vehicle accidents. Most are intra-articular fractures involving the subtalar joint. Open reduction and internal fixation is the mainstay of treatment for displaced intra-articular calcaneal fractures, aiming to restore the congruity of the subtalar articular surface and the normal morphology of the calcaneus.

The sustentaculum tali is a bony prominence on the medial side of the calcaneus that forms the middle facet of the subtalar joint. Because of its dense bone and strong ligamentous attachments, it is a key anchor point for fracture reduction and internal fixation. During surgery via a lateral approach, a sustentaculum tali screw is inserted from the lateral wall toward the medial side to provide stable support for the reduced posterior articular surface.

Depending on the screw tip position on postoperative imaging, fixation is classified as sustentaculum tali fixation (ST; screw penetrates within the range of the sustentaculum tali) or sustentaculum tali fragment fixation (STF; screw is fixed into the larger medial fragment containing the sustentaculum tali, with the penetration point outside the sustentaculum tali range). Because the sustentaculum tali is small and irregularly shaped, accurate screw placement is technically demanding, with reported accuracy of only 60% to 80% even among experienced surgeons. Recent studies suggest that fixation into the sustentaculum fragment may achieve clinical outcomes similar to precise sustentaculum tali fixation; however, the effect of the different fixation modes on postoperative foot and ankle function remains insufficiently investigated.

Design and methods: This is an ambidirectional cohort study. Approximately 92 participants with intra-articular calcaneal fractures treated by open reduction and internal fixation will be enrolled, including retrospective cases from January 2015 to August 2026 and prospective cases from September 2026. Participants will be naturally allocated to the ST or STF group according to the fixation mode determined on postoperative lateral and axial X-rays; no randomization is performed and no treatment plan is altered by the study.

Data are collected during routine clinical follow-up at 1 week, 6 weeks, 12 weeks, 24 weeks, and 1 year after surgery; no additional examinations or interventions are required. Radiographic parameters (Böhler's angle, Gissane's angle, calcaneal height and width) are measured on pre- and postoperative X-rays, and functional outcomes are assessed with the AOFAS ankle-hindfoot score and the Maryland Foot Score at least 12 months postoperatively.

Statistical analysis: Continuous variables will be compared using the t-test or the Wilcoxon rank-sum test according to their distribution, and categorical variables will be compared using the chi-square test. Two-sided P < 0.05 will be considered statistically significant. Multivariable regression may be used to adjust for potential confounders where appropriate. Analyses will be performed with SPSS 26.0 (IBM, Armonk, NY, USA).