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Research Article: A quantitative three-dimensional analysis of posterior facet displacement in Sanders Type II and III intra-articular calcaneal fractures

Date Published: 2026-07-21

Abstract:
To quantify the three-dimensional (3D) displacement characteristics of the posterior facet fragment in Sanders type II and III intra-articular calcaneal fractures (IACFs) caused by falls from height, thereby providing a quantitative anatomical reference for reduction planning. We retrospectively analyzed CT data from 71 patients with closed Sanders type II/III IACFs. Mimics and 3-matic software were utilized for 3D reconstruction and simulated reduction. The translational and rotational changes of the fragment's geometric center were measured before and after reduction. Significant displacement occurred in all directions ( P <?0.05). Predominant translations were lateral (4.55?±?3.16?mm) and inferior (3.81?±?3.13?mm), while posterior translation was minor. Primary rotational deformities included axial plane internal rotation (17.62?±?14.57°) and sagittal plane anterior tilt (12.29?±?13.42°). Coronal plane varus (4.61?±?13.97°) was minimal but exhibited high variability, indicating significant instability. Posterior facet fragments primarily displace inferolaterally with significant internal rotation (?17.62°) and anterior tilt. These findings suggest that rotational malalignment, particularly axial-plane internal rotation and sagittal-plane anterior tilt, may be an important but easily overlooked component of posterior facet displacement. The results may provide a quantitative anatomical reference for preoperative planning and intraoperative assessment of reduction, although further biomechanical and clinical validation is required.

Introduction:
The calcaneus, the largest tarsal bone, bears approximately 60% of the body's weight. Calcaneal fractures account for 1%–2% of all fractures, with intra-articular fractures (IACFs) comprising about 75% ( 1 – 4 ). Displaced IACFs are typically high-energy injuries, resulting from forces such as compression, shear, traction, and direct impact ( 5 – 9 ). These forces concentrate on the posterior facet, leading to multi-directional displacement ( 7 ). The complex anatomy of the calcaneus, particularly the…

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