Objective:

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.

Approach:

• Study Design: Retrospective analysis of CT data from 71 patients with closed Sanders type II/III IACFs.
• Data Analysis: Utilized Mimics and 3-matic software for 3D reconstruction and simulated reduction, measuring translational and rotational changes of the fragment's geometric center.

Key Findings:

• 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).
• 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.

Interpretation:

Rotational malalignment, particularly axial-plane internal rotation and sagittal-plane anterior tilt, may be an important but easily overlooked component of posterior facet displacement.

Limitations:

• Further biomechanical and clinical validation is required.

Conclusion:

The findings provide a quantitative anatomical reference for preoperative planning and intraoperative assessment of reduction.