Efficacy and safety of minimally invasive intramedullary calcaneal nail “nail-in-nail” technique versus extensile lateral approach plate internal fixation for Sanders type II-III calcaneal fractures: a multicenter, prospective, single-blind randomize

OBJECTIVE: To compare the short- and long-term clinical efficacy, radiological outcomes, and complication rates of the minimally invasive intramedullary "nail-in-nail" technique versus extensile lateral approach (ELA) plate internal fixation in the treatment of Sanders Type II-III calcaneal fractures via a multicenter prospective randomized controlled trial (RCT), to provide high-level evidence for clinical decision-making. METHODS: This multicenter, prospective, single-blind, 1:1 randomized controlled trial was conducted in Hubei Province from January 2021 to June 2025. A total of 240 patients with Sanders Type II-III calcaneal fractures were enrolled and randomly assigned to the nail group (n = 120, treated with "nail-in-nail" technique) and the plate group (n = 120, treated with ELA plate fixation). All patients were followed up for 24 months. The primary outcome was the excellent-to-good rate of AOFAS ankle-hindfoot score at 24 months postoperatively. Secondary outcomes included perioperative indicators, radiological parameters, Visual Analogue Scale (VAS) pain score, complication rates (stratified by approach-related and implant-related), and secondary surgery rate during follow-up. Propensity score matching (PSM) was performed for sensitivity analysis to verify the robustness of the results. RESULTS: All baseline characteristics were balanced between the two groups (all P>0.05). A total of 230 patients completed the 24-month follow-up, with an overall loss to follow-up rate of 4.17%. Compared with the plate group, the nail group had significantly shorter operation time, less intraoperative blood loss, fewer fluoroscopy times, shorter hospital stay, and earlier time to full weight-bearing (all P <0.001). Postoperatively, both groups achieved significant restoration of Böhler angle, Gissane angle, and calcaneal morphology (intra-group P<0.001), while the nail group had significantly smaller discrepancies from the healthy side in all radiological parameters (all P<0.05), lower reduction loss rate and lower incidence of post-traumatic arthritis (Kellgren-Lawrence grade ≥ II) at 24 months (all P <0.05). The nail group had significantly lower VAS scores at all postoperative time points (all P <0.001), higher AOFAS scores at 12 and 24 months postoperatively, and a higher excellent-to-good rate at 24 months (92.24% vs. 71.93%, P <0.001). The total complication rate (6.03% vs. 16.67%, P =0.009) and 24-month secondary surgery rate (1.72% vs. 7.89%, P = 0.032) in the nail group were significantly lower than those in the plate group, especially the approach-related complication rate (2.59% vs. 11.40%, P ༝0.008). Sensitivity analysis after PSM confirmed the robustness of all the above results. CONCLUSION: The minimally invasive intramedullary "nail-in-nail" technique has significant advantages in the treatment of Sanders Type II-III calcaneal fractures, with reliable fixation, less surgical trauma, faster postoperative recovery, better long-term functional prognosis, and lower incidence of soft tissue complications and secondary surgery. It is a safe and effective minimally invasive surgical option for eligible patients. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2100043215. Registered on 5 February 2021.