A Prospective Randomized Trial Comparing Headless Full-Threaded and Partial-Threaded Screws for Subtalar Fusion

Research Type: Level 1 - Randomized controlled trial (RCT), Meta-analysis of randomized trials with homogeneous results Introduction/Purpose: Subtalar fusion is a common surgical procedure aimed at alleviating pain in patients with subtalar joint pathology. Successful bone healing is crucial for optimal outcomes. This study compared the efficacy of full-threaded and partial-threaded headed screws to create bone bridging in subtalar fusion. Methods: We conducted a prospective randomized control trial in patients who underwent subtalar fusion between June 2017 and December 2023. They either received full-threaded variable pitch headless or partial-threaded headed screws. We assessed subtalar bone healing by blinded computed tomography analysis at 12 and 24 weeks postoperatively. Patient-related outcomes were collected at these periods and 52 weeks postoperative. Patients were followed for a year. The study was appropriately powered. Results: Our findings, in 79 patients (mean age 58 years (SD 12) who underwent a subtalar fusion, showed 69.0 % bone healing in full-threaded and 68.5% in partial-threaded screws at 12 weeks (p-value 0.97 between groups). Bone formation increased at 24 weeks to 76.8 % and 82.7 %, respectively (p-value 0.17 between groups). The AOS score improved in both groups over time from a mean of 59.2 (SD 17.2) at baseline to 26.3 (SD 17.2) at 52 weeks, with no significant difference between groups. The mental component of the SF-36 score did not change. There was only one revision, a hardware removal. There were no non-unions. There was no linear dependence between patient-reported outcomes and the percentage of bone bridging. Conclusion: This is the first level 1 study on the outcomes of subtalar fusions. It showed that both full-threaded as well as partial-threaded screws can be used for subtalar fusions, as they achieve a high percentage of bone healing and a significant improvement in patient related outcomes, without any major complications. No differences in bone healing or patient reported outcomes were found among fully or partially threaded screw types. Bone healing and AOS score after subtalar fusions On the left it shows percent bone bridging, analysed by CT scan, per screw type at 24 weeks after subtalar fusion. On the right, it depicts the AOS score over time.