A RAT MODEL FOR CAPSULAR CONTRACTURE - THE EFFECTS OF SURFACE TEXTURING

There has been ongoing clinical and laboratory research to determine the role of surface morphology on capsular contracture. The purpose of this study was to develop a rat model in which capsular contracture occurred frequently and to determine whether surface texturing had any effect on the incidence or degree of capsular contracture as determined by in vivo biomechanical analysis of tissue modulus and histological examination of the tissue at the capsule-implant interface. A new sublatissimus implantation site in the rat was developed in an attempt to avoid subpannicular placement, which has been associated with inconsistent results because of contracture despite texturing, and a high rate of implant exposure secondary to trauma. Each rat (N = 43) was implanted with two devices-one smooth-surface 6-ml implant and one textured Biocell 6-ml implant-both with remote ports to allow for biomechanical analysis. Evaluation was carried out at 1, 2, and 3 months (n = 10) and 6 months (n = 5). Biomechanical evaluation of the implants was carried out in vivo and anonymously. The animals were then killed, and sectioning of the overlying capsule-implant interface from the dome of the implant was performed. Histological evaluation was carried out anonymously with regards to the implant type. Capsular contracture developed in smooth-surface devices in 95% of sites; this became evident on biomechanical analysis at 2 months and progressed to 3 months, after which it remained relatively stable. Capsular contracture did not develop in textured devices, but in all cases there was tissue adherence of the capsule to the implant at the interface. Histology confirmed disruption of collagen fiber alignment, increased cellularity and vascularity, and overall thinner capsules around the textured Biocell implants. This rat model provides an inexpensive animal model for further investigation of a difficult clinical problem. In vivo biomechanical analysis to determine tissue modulus has again been shown to be a sensitive method of defining overall soft-tissue contracture around implanted biomaterials.