A mechanical model for the failure of reconstructive breast implant surgery due to capsular contracture

Capsular contracture is a pathological response to implant-based reconstructive breast surgery, where the ``capsule'' (tissue surrounding an implant) painfully thickens, contracts and deforms. It is known to affect breast-cancer survivors at higher rates than healthy women opting for cosmetic breast augmentation with implants. I model the early stages of capsular contracture based on stress-dependent recruitment of contractile and mechanosensitive cells to the implant site. I derive a continuum partial differential equations (PDE) model for the spatio-temporal evolution of cells and collagen densities away from the implant surface. Mechanical properties of the tissue are modelled with a linear viscoelastic stress-strain constitutive equation. A force balance equation relates stress at the tissue level and at a cell level. Various assumptions are investigated for linear versus saturating cell responses to stress and cell traction forces. The model is numerically simulated with the method of lines, coupled with finite differencing. My results point to specific risk factors for capsular contracture, and indicate how physiological parameters, as well as initial states (such as inflammation after surgery) contribute to patient susceptibility.