Computational Modelling of Platysma Muscle Mechanics: Challenging the Isometric Contraction Paradigm and Implications for the Treatment of Neck Bands.

backgroundPlatysmal bands are among the most visible signs of cervical ageing, commonly attributed to focal isometric contraction zones requiring targeted chemodenervation. However, this paradigm is based primarily on indirect imaging and clinical observation, with limited biomechanical validation.

objectivesTo develop a finite element model of platysma contraction incorporating realistic tissue mechanics and to test whether uniform shortening with fascial tethering alone can reproduce contour deformations classically ascribed to isometric contraction.

methodsA high-resolution finite element framework was created using Abaqus/CAE to simulate a layered cervical composite comprising platysma, superficial fascia, and dermis. Geometries were parametrically defined and varied across a synthetic cohort of 1000 virtual anatomies using Latin hypercube sampling. Constitutive formulations included transversely isotropic hyperelastic muscle, viscoelastic fascia with Prony series relaxation, and nonlinear dermis. Simulations varied contraction amplitude (5-15%) and tether density (0-50%). Outputs included cranio-caudal displacement, regional thickness deformation, strain energy, and divergence. Supplementary sustained contraction simulations assessed viscoelastic creep over 300 s.

resultsUniform contraction combined with variable fascial tethering reproduced localized thickening and restricted gliding without requiring isometric contraction zones. Maximal midline thickness increased proportionally with tether density (0.17 mm at 0% tethering to 0.65 mm at 50%), and displacement divergence amplified radial contour deformation. Sensitivity analysis confirmed robustness to ±20% variations in tissue stiffness. Viscoelastic creep simulations suggested progressive strain accumulation (+7% midline thickness over 5 minutes).

conclusionsThese findings suggest that platysmal bands can emerge from predictable passive deformation driven by uniform shortening over heterogeneous anchoring, challenging conventional models of focal hyperactivity. This framework supports the hypothesis that distributed injection protocols targeting tension gradients rather than only visually prominent bands may warrant investigation and highlights the need for further clinical validation of simulation-informed strategies. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .