CT-based three-dimensional planning and early postoperative posterior-facet displacement after percutaneous calcaneal fixation: a retrospective cohort study

Background Percutaneous calcaneal fixation does not permit direct visualization of the posterior facet. We examined whether computed tomography (CT)-based three-dimensional (3D) virtual planning was associated with less residual posterior-facet displacement than conventional multiplanar CT planning. Methods This retrospective single-center cohort included 85 patients (90 feet) with closed Sanders type II or III fractures treated from March 2020 to February 2025. CT-based 3D virtual planning was used for 42 feet, and conventional multiplanar CT planning was used for 48. Two observers measured posterior-facet step-off and gap on CT obtained 1–3 days after surgery. Patient-clustered generalized estimating equations adjusted for baseline displacement, fracture characteristics, demographic variables, surgical year, and surgeon. Holm correction was applied across the two main imaging outcomes. Results Mean step-off was 1.85 ± 0.32 mm after 3D planning and 2.24 ± 0.37 mm after conventional planning. The adjusted difference was − 0.40 mm (95% CI − 0.53 to − 0.28). Mean gap was 1.75 ± 0.33 mm and 2.37 ± 0.50 mm, respectively, with an adjusted difference of − 0.63 mm (95% CI − 0.78 to − 0.47). Both Holm-adjusted P values were < 0.001. Sensitivity analyses, including restriction to observed propensity-score common support, yielded estimates in the same direction. The intraclass correlation coefficient for a single rating, ICC(2,1), was 0.958 for step-off and 0.974 for gap. Conclusions Among selected complete cases who completed percutaneous fixation, CT-based 3D virtual planning was associated with 0.40-mm less step-off and 0.63-mm less gap than conventional planning. Nonrandom allocation, time-dependent adoption, and post-entry exclusions preclude causal interpretation. The clinical importance of these submillimetre early imaging differences and any long-term functional or safety benefit remain uncertain. Trial registration Not applicable. This was a retrospective observational study in which the investigators did not assign the planning strategy.