Morphological analysis (Form Stability Testing)
For morphological analysis, a test bench based on Jewell et al. 2018 was built. The test bench consists of a sliding stage which will carry the breast implant specimen. The sliding stage will be moved until the test specimen touches the stationary plate stop. The moving plate stop is attached to a horizontal caliper in order to measure the width of the implant. A digital height indicator is placed next to the setup in order to measure the projection and pole depth. The setup also allows for supported vertical orientation of the test specimen.
Parameters measured include the width, height, lower pole depth, and upper pole depth for shaped implants, and height, projection, and upper pole depth for round implants. Each parameter is measured 3 times for each device, with the device removed from the testing instrument and repositioned between measurements. Maximum projection of shaped implants is defined as the lower pole depth when in a horizontal position and maximum projection for round implants is defined as the apex at the center of the device. Upper pole depth is the thickness of the upper pole, which is defined as 17% of the mean horizontal height as measured from the top of a shaped implant, or 25% of the mean horizontal height as measured from the top of a round implant.
Less change in implant dimensions when moved from the horizontal to vertical orientation is indicative of better form stability (shape retention). The mean values determined from the 3 measurements of each parameter (width, height, lower pole depth, and upper pole depth) are used to calculate retention and net per cent change in dimension. Retention is an index of the amount of change in dimension, with 100% indicating no change. Mean per cent retention of dimensions is calculated for each
parameter as (vertical value/horizontal value) × 100. Net per cent change in dimension is a measure of the change in retention, where 0% represents no change in dimension and the farther away from 0%, the greater the change (ie, higher percentages represent greater changes). Net per cent change in dimension was calculated as ([vertical value – horizontal value]/[horizontal value]) × 100.
Reference:
Jewell ML, Bengtson BP, Smither K, Nuti G, Perry T. Physical Properties of Silicone Gel Breast Implants. Aesthet Surg J. 2019 Feb 15;39(3):264-275