This is an observational, ambidirectional cohort study. Calcaneal fractures are the most common tarsal bone fractures, and most are intra-articular fractures involving the subtalar joint. Surgery with open reduction and internal fixation is the standard treatment for displaced intra-articular calcaneal fractures. During surgery, a sustentaculum tali screw is placed from the lateral wall of the calcaneus toward the medial side to support the reduced posterior articular surface. Depending on the screw tip position, fixation is classified as sustentaculum tali fixation (ST; screw fixed directly into the sustentaculum tali) or sustentaculum tali fragment fixation (STF; screw fixed into the larger medial fragment containing the sustentaculum tali). This study compares radiographic reduction quality, foot and ankle function, and complications between these two fixation groups. Approximately 92 participants with intra-articular calcaneal fractures will be enrolled, retrospectively from January 2015 to August 2026 and prospectively from September 2026. The fixation mode is determined on postoperative X-rays. Outcomes, including the Maryland Foot Score, the AOFAS ankle-hindfoot score, Böhler's angle, Gissane's angle, calcaneal height and width, and complications, will be compared between groups over at least 12 months of follow-up. No randomization is performed and no treatment is altered by this study.