Rhomboid Flap Simulations under Anisotropic Skin Tension Conditions: A Shape-based Validation Study through Porcine Experiments and Patient Photograph Analysis.

Abstract

Objective: Finite element simulation has the potential to assist facial reconstructive surgery planning by providing biomechanical insight into post-operative tissue behaviour. However, relatively few studies quantitatively evaluate the agreement between simulated and observed surgical outcomes. In this paper, we propose a pipeline for validating simulated suture lines using registered patient photograph pairs and porcine samples.

Methods: To analyze patient photographs collected from the literature, facial landmarks are extracted from pre- and post-operative images. For images containing missing or occluded facial regions, Stable Diffusion inpainting is used to improve landmark detection accuracy. Additionally, 12 skin flaps are performed on two pigs and reconstructed as coloured 3D point clouds obtained using a stereo camera. The reconstructed point clouds are projected into 2D images. For both datasets, pre- and post-operative images are registered and compared with the corresponding simulation results, enabling quantitative evaluation of the simulated suture lines.

Results: Overall, 18 of 20 analyzed patient photographs and 11 of 12 porcine samples exhibited a normalized Hausdorff distance at or below 8%, indicating close geometric agreement between the observed and simulated suture lines.

Conclusion: Quantitative comparison with clinical and experimental data demonstrates the feasibility of assessing agreement between simulated and observed reconstructive surgery outcomes.

Significance: These results demonstrate that finite element simulations can reproduce observed suture line patterns and suggest that relaxed skin tension lines (RSTLs) play an important role in accurately simulating reconstructive surgery procedures.