A Risk Prediction Model for Synthetic Mesh Remodeling and Collagen Distribution After Abdominal Wall Reconstruction: An Analysis of Explants By Host Characteristics and Surgical Site Classifications

Jaime A Cavallo, MD, MPHS, Andres A Roma, MD, Jingxia Liu, PhD, Jenny Ousley, BS, Jennifer Creamer, MD, Sara Baalman, MA, Margaret M Frisella, RN, Brent D Matthews, MD, Corey R Deeken, PhD

Section of Minimally Invasive Surgery, Department of Surgery, Washington University School of Medicine; Division of Biostatistics, Washington University School of Medicine; Department of Anatomic Pathology, Cleveland Clinic

INTRODUCTION: The ability to predict from preoperative patient characteristics and surgical site classifications the patients for whom synthetic meshes are most likely to successfully remodel and develop favorable collagen type ratios would be of great clinical value. We hypothesized that higher collagen type I:III ratios and more favorable histologic remodeling scores of explanted scaffolds would directly correlate with duration of scaffold indwelling, and inversely correlate with hernia diameter; history of diabetes, alcohol abuse (ETOH), radiation to the abdomen or pelvis (RAD), chemotherapy, and corticosteroid use; as well as the age, body mass index (BMI), obesity class, American College of Surgeons wound class, and Ventral Hernia Working Group (VHWG) hernia grade of the subject assessed at the time of both scaffold implantation (T1) and explantation (T2).

METHODS: Biopsies of synthetic meshes were obtained from abdominal wall repair sites of n=24 patients during subsequent abdominal re-explorations. Biopsies were H&E stained, and evaluated according to a semi-quantitative scoring system for characteristics of remodeling [cell infiltration (CI), cell types (CT), host extracellular matrix deposition (ECM), inflammation (IF), fibrous encapsulation (FE), and neovascularization (NEO)], and mean composite remodeling score (CR). Mesh biopsies were also stained with sirius red (SR) for collagen I and fast green (FG) for collagen III, photographed under polarized light, and analyzed for SR:FG ratio. Univariate analyses were performed with two-tailed Kruskal-Wallis tests at a significance level of α=0.05. Significant variables from the univariate analyses were used in multivariate linear regression models.

RESULTS: Mean subject age at T1 and T2, M:F ratio, ratio of onlay:inlay:sublay location, and mean duration of scaffold indwelling were 55.01 ± 12.95 years, 57.07 ± 12.40 years, 6:18, 2:3:15, and 1195.35 ± 1331.59 days, respectively. IF and mean CR significantly correlated with, and CT trended toward significance with subject race (p=0.0272, 0.0205, and p=0.0521, respectively). Mean CR trended toward significance with BMI at T1 (p=0.0541). CT significantly correlated with VHWG hernia grade at T2 (p=0.0034). IF significantly correlated with subject history of tobacco use (p=0.0365), and FE, mean SR, and mean SR/FG ratio significantly correlated with cigarette packs per day (p=0.0483, 0.0149, 0.0485, respectively). ECM, FE, and NEO significantly correlated with duration of mesh indwelling in days (p=0.0328, 0.0285, 0.0325, respectively). Following multivariate linear regression, only cigarette packs per day and subject BMI at T1 were significantly correlated with mean FG (p=0.0157, 0.0014, respectively).

CONCLUSION: Host characteristics and surgical site assessments may predict degree of remodeling following abdominal wall repair for synthetic meshes. Patient factors significantly correlated with synthetic mesh remodeling include race, history and quantity of tobacco use, BMI at time of mesh implantation, duration of mesh indwelling, and VHWG hernia grade at time of mesh explantation. Quantity of collagen III, which confers less mechanical strength to tissue than collagen I, significantly correlated in multivariate analysis with cigarette packs per day and host BMI at the time of the mesh implantation for abdominal wall reinforcement.

Session: Poster Presentation

Program Number: P020

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