A Current Review of Biologic Meshes in Abdominal Wall Reconstruction:

A multicenter randomized controlled trial comparing short- and medium-term outcomes of novel biologics and lightweight synthetic mesh for laparoscopic inguinal hernia repair

INTRODUCTION

The use of biological graft in laparoscopic inguinal hernia repair (LIHR) has been controversial, and there is a lack of high-level evidence to confirm the value of biological graft in LIHR. The purpose of this study is to evaluate the effectiveness of a novel composite biologics in LIHR.

METHODS

A multicenter, single-blinded, randomized controlled clinical trial was designed. Fifty patients with unilateral primary inguinal hernia were randomly assigned to the experimental and control group (1:1). The experimental group was repaired with a non-crosslinked composite extracellular matrix from porcine urinary bladder matrix and small intestinal submucosa (UBM/SIS). The control group was repaired with a lightweight, large-pore, synthetic mesh. The primary endpoint was the effectiveness rate of hernia repair.

RESULTS

The patients were followed up for four years. No significant difference was found between the experimental group and the control group in the effective rate of hernia repair (24/24[100%] vs 21/22[95.45%], RR, 0.4667; 95%CI, 0.3294-2.304; P = 0.4783). There was no fever, seroma, infection, groin pain, foreign body discomfort or recurrence in the experimental group during the follow-up. In the control group, there were 2 cases of seroma 14 days after operation, 1 case of groin discomfort 60 days after operation and one case of recurrence 410 days after surgery.

CONCLUSION

Compared with the lightweight synthetic mesh, the novel UBM/SIS graft has comparable short-term and medium-term effectiveness in LIHR, and the incidence of postoperative complications such as seroma groin discomfort is lower. Trial registration Clinical Trials Registry: ChiCTR1800020173.

A Review of Advanced Abdominal Wall Hernia Patch Materials

Tension-free abdominal wall hernia patch materials (AWHPMs) play an important role in the repair of abdominal wall defects (AWDs), which have a recurrence rate of <1%. Nevertheless, there are still significant challenges in the development of tailored, biomimetic, and extracellular matrix (ECM)-like AWHPMs that satisfy the clinical demands of abdominal wall repair (AWR) while effectively handling post-operative complications associated with abdominal hernias, such as intra-abdominal visceral adhesion and abnormal healing. This extensive review presents a comprehensive guide to the high-end fabrication and the precise selection of these advanced AWHPMs. The review begins by briefly introducing the structures, sources, and properties of AWHPMs, and critically evaluates the advantages and disadvantages of different types of AWHPMs for AWR applications. The review subsequently summarizes and elaborates upon state-of-the-art AWHPM fabrication methods and their key characteristics (e.g., mechanical, physicochemical, and biological properties in vitro/vivo). This review uses compelling examples to demonstrate that advanced AWHPMs with multiple functionalities (e.g., anti-deformation, anti-inflammation, anti-adhesion, pro-healing properties, etc.) can meet the fundamental clinical demands required to successfully repair AWDs. In particular, there have been several developments in the enhancement of biomimetic AWHPMs with multiple properties, and additional breakthroughs are expected in the near future.

What Mesh Should be Used in Hernia Repair?

Ventral hernia repair is one of the most frequently performed general surgery operations in the world, yet the treatment of clean-contaminated and contaminated cases remains controversial. Biologic mesh has been thought to resist infection, decrease chronic wound complications, and reduce the need for reoperation. Their use continues to be predominant in contaminated and dirty cases. This article is a comprehensive review of what mesh to choose in both clean and contaminated single-staged, open ventral hernia repair with further considerations of tissue incorporation characteristics, cost, safety profiles, complications, recurrence, and long-term outcomes.

Comparison of mechanical properties and host tissue response to OviTex™ and Strattice™ surgical meshes

PURPOSE

This study compared the in vitro/benchtop and in vivo mechanical properties and host biologic response to ovine rumen-derived/polymer mesh hybrid OviTex™ with porcine-derived acellular dermal matrix Strattice™ Firm.

METHODS

OviTex 2S Resorbable (OviTex 2S-R) and Strattice morphology were examined in vitro using histology and scanning electron microscopy; mechanical properties were assessed via tensile test; in vivo host biologic response and explant mechanics were evaluated in a rodent subcutaneous model. Separately, OviTex 1S Permanent (OviTex 1S-P) and Strattice were evaluated in a primate abdominal wall repair model.

RESULTS

OviTex 2S-R demonstrated layer separation, whereas Strattice retained its structural integrity and demonstrated higher maximum load than OviTex 2S-R out-of-package (124.8 ± 11.1 N/cm vs 37.9 ± 5.5 N/cm, p < 0.001), 24 h (55.7 ± 7.4 N/cm vs 5.6 ± 3.8 N/cm, p < 0.001), 48 h (45.3 ± 14.8 N/cm vs 2.8 ± 2.6 N/cm, p = 0.003), and 72 h (29.2 ± 10.5 N/cm vs 3.2 ± 3.1 N/cm, p = 0.006) following collagenase digestion. In rodents, inflammatory cell infiltration was observed between OviTex 2S-R layers, while Strattice induced a minimal inflammatory response. Strattice retained higher maximum load at 3 (46.3 ± 27.4 N/cm vs 9.5 ± 3.2 N/cm, p = 0.041) and 6 weeks (28.6 ± 14.1 N/cm vs 7.0 ± 3.0 N/cm, p = 0.029). In primates, OviTex 1S-P exhibited loss of composite mesh integrity whereas Strattice integrated into host tissue with minimal inflammation and retained higher maximum load at 1 month than OviTex 1S-P (66.8 ± 43.4 N/cm vs 9.6 ± 4.4 N/cm; p = 0.151).

CONCLUSIONS

Strattice retained greater mechanical strength as shown by lower susceptibility to collagenase degradation than OviTex 2S-R in vitro, as well as higher maximum load and improved host biologic response than OviTex 2S-R in rodents and OviTex 1S-P in primates.

Acellular Dermal Matrix Susceptibility to Collagen Digestion: Effect on Mechanics and Host Response

Various tissue origins and manufacturing processes can differentially affect the retention of native properties of acellular dermal matrices (ADMs); however, comparative studies are limited. Head-to-head comparisons between different configurations of porcine-derived Strattice (Allergan Aesthetics, an AbbVie Company, Irvine, CA) and bovine-derived SurgiMend (Integra LifeSciences, Billerica, MA) ADMs were performed to evaluate mechanical integrity and host tissue biologic response. Thermodynamic profile and morphology, which affect retention of mechanical strength, were evaluated through differential scanning calorimetry, scanning electron microscopy, and histology. Mechanical strength was assessed through tensile testing following collagenase exposure in vitro and following subcutaneous implantation in a rodent model. Host biologic response was evaluated through histopathology. Compared with respective native tissues, reductions in onset melting temperature following tissue processing were smaller for Strattice Firm versus SurgiMend 1.0 (Δ0.79°C vs. Δ5.77°C), Strattice Extra Thick versus SurgiMend 3.0 (Δ1.57°C vs. Δ4.79°C), and Strattice Perforated versus SurgiMend Microperforated (Δ1.18°C vs. Δ7.76°C), with similar trends for peak melting temperature. Strattice maintained native dermal architecture versus compacted collagen with process-induced interstices observed for SurgiMend. Strattice Firm, Extra Thick, and Perforated retained 33.44%, 65.65%, and 17.20% of initial strength after 48 h exposure to excess collagenase, while the SurgiMend ADMs were completely digested by 48 h. At 6 weeks postimplantation, both Strattice and SurgiMend showed minimal inflammatory response, but greater fibroblast repopulation was evident for Strattice. Strattice Firm had higher maximum load (145.85 ± 33.05 N/cm vs. 24.29 ± 12.35 N/cm, p ≤ 0.01), maximum stress (8.20 ± 1.91 MPa vs. 2.24 ± 1.27 Mpa, p ≤ 0.01), and stiffness (7491.00 ± 1981.32 N/cm vs. 737.56 ± 292.55 N/cm, p ≤ 0.01) than SurgiMend 1.0. Strattice Extra Thick had lower maximum load (198.54 ± 58.79 N/cm vs. 303.08 ± 76.76 N/cm, p < 0.05) than SurgiMend 3.0, but similar maximum stress (6.96 ± 1.78 Mpa vs. 8.73 ± 2.15 Mpa) and stiffness (13386.11 ± 3123.28 N/cm vs. 9389.02 ± 4860.67 N/cm). Strattice Perforated had higher maximum load (72.65 ± 41.44 N/cm vs. 10.23 ± 4.67 N/cm, p < 0.05) and maximum stress (4.08 ± 2.08 Mpa vs. 0.44 ± 0.19 p < 0.05) than SurgiMend Microperforated. Maximum load retention rates following implantation were higher for Strattice Firm versus SurgiMend 1.0 (37.85% vs. 8.03%), Strattice Extra Thick versus SurgiMend 3.0 (45.03% vs. 37.80%), and Strattice Perforated versus SurgiMend Microperforated (28.04% vs. 6.21%). Similar results were obtained for maximum stress and stiffness. In conclusion, Strattice retained greater mechanical strength in vitro and in vivo, while exhibiting greater fibroblast cell infiltration.

Delayed sequential abdominal wall closure in pediatric liver transplantation to overcome "large for size" scenarios

BACKGROUND

Primary abdominal wall closure after pediatric liver transplantation (PLT) is neither always possible nor advisable, given the graft-recipient size discrepancy and its potential large-for-size scenario. Our objective was to report the experience accumulated with delayed sequential closure (DSC) guided by Doppler ultrasound control.

METHODS

Retrospective analysis of DSC performed from 2013 to March 2020.

RESULTS

Twenty-seven DSC (26.5%) were identified out of 102 PLT. Transplant indications and type of grafts were similar among both groups. In patients with DSC, mean weight and GRWR were 9.4 ± 5.5 kg (3.1-26 kg) and 4.7 ± 2.4 (1.9-9.7), significantly lower and higher than the primary closure cohort, respectively. The median time to achieve definitive closure was 6 days (range 3-23 days), and the median number of procedures was 4 (range 2-9). Patients with DSC had longer overall PICU (22.5 ± 16.9 vs. 9.1 ± 9.7 days, p < .05) and hospital stay (33.4 ± 19.1 vs 23, 9 ± 19.8 days (p < .05). These differences are less remarkable if the analysis is performed in a subgroup of patients weighing less than 10 kg. Two patients presented vascular complications (7.4%) within DSC group. No differences were seen when comparing overall, 3-year graft and patient survival (96% and 96% in the DSC group).

CONCLUSIONS

DSC is a simple and safe technique to ensure satisfactory clinical outcomes to overcome "large for size" scenarios in PLT. In addition, we were able to avoid using a permanent biological material for closing the abdomen.

Latest Trends on the Attenuation of Systemic Foreign Body Response and Infectious Complications of Synthetic Hernia Meshes

Throughout the past few years, hernia incidence has remained at a high level worldwide, with more than 20 million people requiring hernia surgery each year. Synthetic hernia meshes play an important role, providing a microenvironment that attracts and harbors host cells and acting as a permanent roadmap for intact abdominal wall reconstruction. Nevertheless, it is still inevitable to cause not-so-trivial complications, especially chronic pain and adhesion. In long-term studies, it was found that the complications are mainly caused by excessive fibrosis from the foreign body reaction (FBR) and infection resulting from bacterial colonization. For a thorough understanding of their complex mechanism and providing a richer background for mesh development, herein, we discuss different clinical mesh products and explore the interactions between their structure and complications. We further explored progress in reducing mesh complications to provide varied strategies that are informative and instructive for mesh modification in different research directions. We hope that this work will spur hernia mesh designers to step up their efforts to develop more practical and accessible meshes by improving the physical structure and chemical properties of meshes to combat the increasing risk of adhesions, infections, and inflammatory reactions. We conclude that further work is needed to solve this pressing problem, especially in the analysis and functionalization of mesh materials, provided of course that the initial performance of the mesh is guaranteed.

The relationship between crosslinking structure and silk fibroin scaffold performance for soft tissue engineering

Biologically active scaffolds with tunable mechano- and bio-performance remain desirable for soft tissue engineering. Previously, highly elastic and robust silk fibroin (SF) scaffolds were prepared via cryogelation. In order to get more insight into the role of ethylene glycol diglycidyl ether (EGDE) on the structure and properties of SF scaffolds, we investigated the fate of SF scaffolds with different usages of the crosslinking agent in vitro and in vivo. Although SF scaffolds with varied EGDE contents showed similar micro-morphology, increasing EGDE from 1 mmol/g to 5 mmol/g resulted in firstly increased and later decreased content of β-sheet conformation, and linearly increased tensile modulus and decreased elasticity. The dual-crosslinked SF scaffolds with EGDE up to 5 mmol/g did not show in vitro cytotoxicity for NIH3T3 fibroblasts. In vivo subcutaneous implantation of SF scaffolds with <3 mmol/g EGDE displayed excellent degradation behavior and tissue ingrowth after 28 days of implantation. However, with ≥3 mmol/g EGDE, SF scaffolds exhibited obvious post-implantation foreign body reactions, probably associated with slow degradation due to excess chemical crosslinks and less mechanical compatibility. These results suggest that an appropriate dosage of crosslinking agent was critical to achieve balanced mechanical properties, degradability in vivo and immuno-properties of the SF scaffold platform for soft tissue engineering.

Outcomes of mid-term and long-term degradable biosynthetic meshes in single-stage open complex abdominal wall reconstruction

OBJECTIVE

To assess clinical outcomes in patients that underwent open single-stage complex abdominal wall reconstruction (CAWR) with biosynthetic mesh.

METHODS

Retrospective observational study of two prospectively registered series of consecutive patients undergoing CAWR with either long-term degradable (LTD) Phasix^™ or mid-term degradable (MTD) BIO-A^® biosynthetic mesh in a single institution between June 2016 and December 2019.

RESULTS

From 169 patients with CAWR, 70 consecutive patients were identified who underwent CAWR with either LTD or MTD biosynthetic mesh. More than 85% of patients had an incisional hernia that could be classified as moderately complex to major complex due to a previous wound infection (67%), one or more complicating comorbidities (87.1%), one or more complicating hernia characteristics (75.7%) or contaminated or dirty defects (37.1%). Concomitant component separation was performed in 43 of 70 patients (61.4%). Overall surgical site infection (SSI) rate in these CAWR patients was 45.7%. Seventeen of 70 patients (24.3%) had computed tomography (CT) - and culture-confirmed SSI in direct contact of mesh, suspicious of mesh infection. Mesh removal for persistent local infection occurred in 10% (7 of 70) after a median of 229 days since surgery. Salvage rate of mesh after direct contact with infection was 58.8%. All removed meshes were in the LTD group. Seven patients (10%) had a recurrence; four patients in the LTD group (10%) had a recurrence at a median follow-up of 35 months and three patients in the MTD group (10%) at a median follow-up of 11 months. Three of the seven recurrences occurred in patients with SSI in persistent and direct contact with mesh.

CONCLUSIONS

Comorbid patients undergoing open complex abdominal wall reconstruction are at high risk of postoperative wound complications regardless of which type of biosynthetic mesh is used. When in persistent and direct contact with infection, long-term biodegradable biosynthetic meshes may need to be removed, whereas mid-term biodegradable biosynthetic meshes can be salvaged.

Biologic Mesh in Surgery: A Comprehensive Review and Meta-Analysis of Selected Outcomes in 51 Studies and 6079 Patients

BACKGROUND

In recent decades, biologic mesh (BM) has become an important adjunct to surgical practice. Recent evidence-based clinical applications of BM include but are not limited to: reconstruction of abdominal wall defects; breast reconstruction; face, head and neck surgery; periodontal surgery; other hernia repairs (diaphragmatic, hiatal/paraesophageal, inguinal and perineal); hand surgery; and shoulder arthroplasty. Prior systematic reviews of BM in complex abdominal wall hernia repair had several shortcomings that our comprehensive review seeks to address, including exclusion of laparoscopic repair, assessment of risk of bias, use of an acceptable meta-analytic method and review of risk factors identified in multivariable regression analyses.

MATERIALS AND METHODS

We sought articles of BM for open ventral hernia repair reporting on early complications, late complications or recurrences and included minimum of 50. We used the quality in prognostic studies risk of bias assessment tool. Random effects meta-analysis was applied.

RESULTS

This comprehensive review selected 62 articles from 51 studies that included 6,079 patients. Meta-analytic pooling found that early complications are present in about 50%, surgical site occurrences (SSOs) in 37%, surgical site infections (SSIs) in 18%, reoperation in 7%, readmission in 20% and mortality in 3%. Meta-analytic estimates of late outcomes included overall complications (42%), SSOs (40%) and SSIs (22%). Specific SSOs included seroma (14%), hematoma (4%), abscess (10%), necrosis (5%), dehiscence (8%) and fistula formation (5%). Reoperation occurred in about 17%, mesh explantation in 9% and recurrence in 36%.

CONCLUSION

Estimates of nearly all outcomes from individual studies were highly heterogeneous and sensitivity analyses and meta-regressions generally failed to explain this heterogeneity. Recurrence is the only outcome for which there are consistent findings for risk factors. Bridge placement of BM is associated with higher risk of recurrence. Prior hernia repair, history of reintervention and history of mesh removal were also risk factors for increased recurrence.

Functional requirements for polymeric implant materials in head and neck surgery

BACKGROUND

The pharyngeal reconstruction is a challenging aspect after pharyngeal tumor resection. The pharyngeal passage has to be restored to enable oral alimentation and speech rehabilitation. Several techniques like local transposition of skin, mucosa and/or muscle, regional flaps and free vascularized flaps have been developed to reconstruct pharyngeal defects following surgery, in order to restore function and aesthetics. The reconstruction of the pharynx by degradable, multifunctional polymeric materials would be a novel therapeutical option in head and neck surgery.

MATERIALS AND METHODS

Samples of an ethylene-oxide sterilized polymer (diameter 10 mm, 200μm thick) were implanted for the reconstruction of a standardized defect of the gastric wall in rats in a prospective study. The stomach is a model for a "worst case" application site to test the stability of the implant material under extreme chemical, enzymatical, bacterial, and mechanical load.

RESULTS

Fundamental parameters investigated in this animal model were a local tight closure between the polymer and surrounding tissues, histological findings of tissue regeneration and systemic responses to inflammation. A tight anastomosis between the polymer and the adjacent stomach wall was found in all animals after polymer implantation (n = 42). Histologically, a regeneration with glandular epithelium was found in the polymer group. No differences in the systemic responses to inflammation were found between the polymer group (n = 42) and the control group (n = 21) with primary wound closure of the defect of the gastric wall.

CONCLUSIONS

A sufficient stability of the polymeric material is a requirement for the pharyngeal reconstruction with implant materials.

Simultaneous Ventral Hernia Repair and Panniculectomy: A Systematic Review and Meta-Analysis of Outcomes

BACKGROUND

Simultaneous ventral hernia repair and panniculectomy (SVHRP) is a procedure that is more commonly being offered to patients with excess skin and subcutaneous tissue in need of a ventral hernia repair; however, there are concerns about surgical-site complications and uncertainty regarding the durability of repair. SVHRP outcomes vary within the literature. This study assessed the durability, complication profile, and safety of SVHRP through a large data-driven repository of SVHRP cases.360 METHODS:: The current SVHRP literature was queried using the MEDLINE, PubMed, and Cochrane databases. Predefined selection criteria resulted in 76 relevant titles yielding 16 articles for analysis. Meta-analysis was used to analyze primary outcomes, identified as surgical-site occurrence and hernia recurrence. Secondary outcomes included review of techniques used and systemic complications, which were analyzed with pooled weighted mean analysis from the collected data.

RESULTS

There were 917 patients who underwent an SVHRP (mean age, 52.2 ± 7.0 years; mean body mass index, 36.1 ± 5.8 kg/m; mean pannus weight, 3.2 kg). The mean surgical-site occurrence rate was 27.9 percent (95 percent CI, 15.6 to 40.2 percent; I = 70.9 percent) and the mean hernia recurrence rate was 4.9 percent (95 percent CI, 2.4 to 7.3 percent; I = 70.1 percent). Mean follow-up was 17.8 ± 7.7 months. The most common complications were superficial surgical-site infection (15.8 percent) and seroma formation (11.2 percent). Systemic complications were less common (7.8 percent), with a thromboembolic event rate of 1.2 percent. The overall mortality rate was 0.4 percent.

CONCLUSIONS

SVHRP is associated with a high rate of surgical-site occurrence, but surgical-site infection seems to be less prominent than previously anticipated. The low hernia recurrence rate and the safety of this procedure support its current implementation in abdominal wall reconstruction.