Mechanical properties of breast periprosthetic capsules and the correlation to capsule contracture

Contracture of the fibrous connective capsules that form around breast implants is the most frequent complication for silicone mammary prostheses. Capsule contraction is thought to be associated with the alteration in the mechanical properties of the tissue, but to date such a correlation has not been quantified. This study aimed to develop an experimental protocol to investigate the mechanical properties of the periprosthetic tissue and their dependence on the severity of capsular contracture. Capsule samples were harvested from donors undergoing surgical correction or re-implantation of breast prostheses; strip specimens were cut along both the meridian and circumferential directions of the capsular dome. The experimental protocol consisted of mechanical preconditioning, stress relaxation tests and tensile tests to rupture. The capsular tissue exhibited non-linear stress-strain relationships and stress relaxation behavior; nevertheless, both the elastic and the relaxation properties did not depend on the loading direction. In spite of the small number of samples included, to date, in the experimentation, some preliminary conclusions can be drawn: the stiffness and the strength of the tissue increases with the contracture severity; the relaxation seems unaffected by the contracture degree. Some assumptions concerning the modifications in periprosthetic tissue composition following contracture are also drawn.