Stiffness, Compliance, Resilience, and Creep Deformation: Understanding Implant-Soft Tissue Dynamics in the Augmented Breast: Fundamentals Based on Materials Science

Postoperative tissue stretch deformities are among the possible complications in breast augmentation. These deformities are responsible for many potential risks such as bottoming-out deformity, breakdown of the inframammary fold, permanent tissue atrophy, sensory loss, and breast distortion (visible implant edges and traction rippling), among others. Although the elastic properties of the breast are a major concern for plastic surgeons, concepts such as stiffness, compliance, elasticity, and resilience have not been sufficiently defined or explored in the plastic surgery literature. Similar to any other material, living tissues are subject to the fundamentals of the mechanics of materials. Based on their experience with more than 5,000 breast augmentations, the authors explored the basic fundamentals of the mechanics of materials in search of a rational explanation for long-term results in breast augmentation and augmentation-mastopexy. A basic law of the mechanics of materials determines that when a material (e.g., breast) is loaded with a force (e.g., implant), it produces a stress that causes the material to deform (e.g., breast augmentation), and this behavior might be graphed in a theoretical material's stress-stress curve. This deformation will increase with time although the load (implant) remains constant, a concept termed creep deformation. Because the breast, like all human tissues, is a viscoelastic material, the application of concepts such as elastic and plastic deformation, stiffness, compliance, resilience, and creep deformation can and should be applied to breast augmentation surgery. The authors have found that the principles of the mechanics of materials can provide plastic surgeons with some clues for a predictable, long-lasting good result in breast augmentation and augmentation-mastopexy. Future studies are needed to develop these concepts and evaluate how they might individually determine the mid- and long-term outcomes of augmented breasts. 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.