Effect of surgical insertion on the local shell properties of SILASTIC II silicone gel breast implants.

The reasons for the failure of silicone gel breast implants are unclear. One potential failure mechanism is the weakening of the implant shell during its insertion into the breast. Such local weakening could eventually lead to implant failure. We recently reported on the effect of implant surgery on the overall mechanical properties of SILASTIC II gel-filled implants. In the earlier study, the mechanical properties of 34 Dow Corning SILASTIC II gel-filled breast implants from the same manufacturing lot were measured. Twenty of the thirty four implants were not implanted but were evaluated to establish a baseline of control data. The other fourteen lot-matched implants were inserted into a subglandular pocket through an inframammary incision in a cadaver breast and then removed. The experimental augmentation scenario was designed to represent actual breast implantation as closely as possible. The mechanical properties of the anterior and posterior sides of the control implants (not implanted) and explants (implanted in a cadaver) were measured and compared to determine whether differences existed between the explant and control groups. We found that the implantation surgery process did slightly reduce the average tensile strength. Although not as statistically significant, other mechanical properties such as breaking energy and moduli were less for the explants than the controls. The reduction was a relatively small percentage in the context of overall shell properties. Elongation and tear resistance were unaffected. Our findings suggested that the surgical act of implanting a breast implant has a small but detectable weakening effect on the average tensile strength, breaking energy and moduli of the elastomeric shell of the device. The present study is an extension of the previous investigation. Here we have analyzed the explant shell region where the surgeon's fingers forced the implant through the incision. Our results indicate that the implant shell can be locally damaged due to the implantation process.