Plastic Surgery Research Council

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Superficial Fascial System Strength Can Be Quantified with Portable Ultrasound and Mean Gray Value Calculation
Michelle E. McCarthy, MS1, Richard Guidry, BS2, David Straughan, MD3, Jason Schuster, MSBME4, Michael Dancisak, PhD4, Abigail Chaffin, MD3, Hugo St-Hilaire, MD5, John Lindsey, MD3.
1Tulane University School of Medicine, New Orleans, LA, USA, 2Louisiana State University Health Sciences Center, New Orleans, LA, USA, 3Division of Plastic Surgery, Department of Surgery, Tulane University School of Medicine, New Orleans, LA, USA, 4Center for Anatomical and Movement Sciences, Tulane University, New Orleans, LA, USA, 5Division of Plastic and Reconstructive Surgery, LSU Health Sciences Center, New Orleans, LA, USA.

Wound dehiscence and extensive scarring continue to be the leading complications following body contouring procedures. Lack of structural support deep to the skin closure can result in hypertrophic scarring, recurrence of laxity, and wound dehiscence, thus decreasing patient satisfaction and increasing reoperation rates. The superficial fascial system (SFS) has long been implicated as the main source of mechanical strength in subcutaneous tissues. However, no studies to date have shown this mechanical relationship. Utilizing portable ultrasound technology, we have confirmed previous studies showing that the quantity of SFS is highly variable among different patients and within different areas of the same patient. In this study, we used ultrasound image analysis to quantify the amount of SFS in tissue specimens from the abdomen and investigated the relationship between SFS and tissue tensile strength.
Tissue specimens were collected from 5 patients undergoing abdominoplasty procedures. These specimens were then cut into 3x1x1 inch rectangles (59 total samples) using a 3D-printed template to ensure precise sizing. Ultrasound images of the SFS in each sample were taken with the Lumify portable ultrasound system. Number 1 Vicryl sutures were then placed into tissue sections utilizing a needle guide within the 3D-printed template, ensuring equal bites across all samples. Suture pull-out strength was measured using an ADMET axial testing system. To quantify SFS, the mean gray value (MGV) of each image was calculated. The MGV is given by the following equation below. As SFS is more echogenic than surrounding fat, images with more SFS will have a larger MGV. Polynomial least-squares regression analysis was performed in Microsoft Excel.

Using regression analysis, we found that ultrasound image MGV positively correlated with tissue tensile strength (Figure 1, P = 0.006). Additionally, when the MGV of all tissue samples from each patient were averaged together to make a whole-patient MGV, we found that the whole-patient MGV correlated positively with whole-patient tissue tensile strength (Figure 2, P=0.036). Notably, whole-patient MGV accounted for 98.5% of the variance seen in patient-average tensile strength, making whole-patient MGV a very strong predictor for tensile strength in our study.
Using readily-available portable ultrasound and image-processing technology, patient and area-specific SFS can be visualized and quantified, thus allowing prediction of subcutaneous tissue strength. The amount of SFS in a specimen correlates with the suture pull-out/tensile strength of that specimen. Clinically, the quantification of a patient's SFS pre-operatively may aid in outcome predictions, managing patient expectations, as well as potentially lowering procedure complication rates.

Acknowledgements: We would like to acknowledge Theresa Weeks for invaluable assistance with image collection and management.

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