20. A Comparative Analysis on the Gravitational Effect on Silicone and Saline Breast Implants

OBJECTIVE: Bottoming out is a well described phenomenon in both reconstructed and augmented breasts using implants. Over time, the soft tissue of the breast loses its structural integrity under the weight of a breast implant, which causes preferential expansion of the breasts. This can lead to implant malposition, nipple malposition, patient discomfort, and need for revision. This phenomenon happens with both saline and silicone breast implants, but many plastic surgeons anecdotally believe the frequency of bottoming out is greater with the use of saline implants. No comparative mechanical studies have been done to investigate this experience, however. Our hypothesis is that saline implants have a higher rate of bottoming out, as they impart more force on their surroundings compared to silicone implants. This study aims to develop a model of bottoming out, by examining the vertical force of breast implants dropped on to a force plate at varying heights. METHODS: Three silicone implants (Mentor MemoryGel Smooth Round High Profile Memory Gel: 250cc, 450cc, 650cc) and three saline implants (Mentor Smooth Round High Profile Slaine: 250cc-300cc, 420cc – 500c, 630cc-750cc) were chosen to act as matched comparisons. Silicone implants were weighed, and each corresponding saline implant was filled with saline solution to match the weight of the silicone implant. Implants were dropped from varying heights onto a force plate, and the vertical force of impact (Fz) in Newtons was recorded. Each implant was dropped five times from the varying heights and the force averaged. Implants were dropped from 5cm, 10cm, 15cm, 20cm, 25cm, and 30cm to simulate the spectrum vertical variation that a breast implants feels with day to day activities (i.e, walking, running, jumping). Repeated measure ANOVA was utilized to analyze the 3 main factors (material, implant weight, and drop height) and their interactions. RESULTS: Saline implants at all three weights, and from all five drops heights, imparted more vertical force on the force plate when compared to their matched silicone implants. All main factors, and their interactions, were found to significantly affect the vertical impact force. CONCLUSION: Saline implants, when dropped from varying heights impart more vertical force compared to weight matched silicone implants. The inherent properties of silicone in a breast implant act as a shock absorber and translate less force on its surroundings, particularly in the vertical dimension. This serves as an explanation for why bottoming out is anecdotally reported more with saline implants compared to silicone implants. These findings have significant implications when selecting the appropriate breast implant for a patient. Further studies are needed for clinical correlation. CORRESPONDING AUTHOR: Mitchell Gauger, [email protected], 5742533321, 255 Bradford St. NE, Grand Rapids, MI 49503