Physical Properties of Silicone Gel Breast Implants.

BACKGROUND: Surgical applications using breast implants are individualized operations to fill and shape the breast. Physical properties beyond shape, size, and surface texture are important considerations during implant selection. OBJECTIVES: Compare form stability, gel material properties, and shell thickness of textured shaped, textured round, and smooth round breast implants from 4 manufacturers: Allergan, Mentor, Sientra, and Establishment Labs, through bench testing. METHODS: Using a mandrel height gauge, form stability was measured by retention of dimensions on device movement from a horizontal to vertical supported orientation. Dynamic response of the gel material (gel cohesivity, resistance to gel deformation, energy absorption) was measured using a synchronized target laser following application of graded negative pressure. Shell thickness was measured using digital thickness gauge calipers. RESULTS: Form stability, gel material properties, and shell thickness differed across breast implants. Of textured shaped devices, Allergan Natrelle 410 exhibited greater form stability than Mentor MemoryShape and Sientra Shaped implants. Allergan Inspira round implants containing TruForm 3 gel had greater form stability, higher gel cohesivity, greater resistance to gel deformation, and lower energy absorption than those containing TruForm 2 gel and in turn, implants containing TruForm 1 gel. Shell thickness was greater for textured vs smooth devices, and differed across styles. CONCLUSIONS: Gel cohesivity, resistance to gel deformation, and energy absorption are directly related to form stability, which in turn determines shape retention. These characteristics provide information to aid surgeons choosing an implant based on surgical application, patient tissue characteristics, and desired outcome.

Breast implant surface texture impacts host tissue response.

BACKGROUND: Surface texture of a breast implant influences tissue response and ultimately device performance. Characterizing differences among available surface textures is important for predicting and optimizing performance. METHODS: Scanning electron microscopy (SEM) and X-ray computed tomography (CT)-imaging were used to characterize the topography and surface area of 12 unique breast implant surface textures from seven different manufacturers. Samples of these surface textures were implanted in rats, and tissue response was analyzed histologically. In separate experiments, the force required to separate host tissue from the implant surface texture was used as a measure of tissue adherence. RESULTS: SEM imaging of the top and cross section of the implant shells showed that the textures differed qualitatively in evenness of the surface, presence of pores, size and openness of the pores, and the depth of texturing. X-ray CT imaging reflected these differences, with the texture surface area of the anterior of the shells ranging from 85 to 551 mm2, which was 8-602% greater than that of a flat surface. General similarities based on the physical structure of the surfaces were noted among groups of textures. In the rat models, with increasing surface texture complexity, there was increased capsule disorganization, tissue ingrowth, and tissue adherence. CONCLUSIONS: Surface area and topography of breast implant textures are important factors contributing to tissue ingrowth and adherence. Based on surface area characteristics and measurements, it is possible to group the textures into four classifications: smooth/nanotexture (80-100 mm2), microtexture (100-200 mm2), macrotexture (200-300 mm2), and macrotexture-plus (> 300 mm2).