Abdominal wall reinforcement: biologic vs. degradable synthetic devices

Remodeling and Regenerative Properties of Fully Absorbable Meshes for Abdominal Wall Defect Repair: A Systematic Review and Meta-Analysis of Animal Studies

Fully absorbable meshes can repair abdominal wall defects and effectively reduce the incidence of complications, but different types of fully absorbable meshes have different remodeling and regeneration effects. In order to investigate and compare the effects of different fully absorbable meshes on remodeling and regeneration in animals and reduce the biological risk of clinical translation, SYRCLE was adopted to evaluate the methodological quality of the included studies, and GRADE and ConQual were used to evaluate the quality of evidence. According to the inclusion and exclusion criteria, a total of 22 studies related to fully absorbable meshes were included in this systematic review. These results showed that fiber-based synthetic materials and fiber-based natural materials exhibited better restorative and regenerative effects indicated by infiltration and neovascularization, when compared with a porcine acellular dermal matrix. In addition, the human acellular dermal matrix was found to have a similar regenerative effect on the host extracellular matrix and scaffold degradation compared to the porcine acellular dermal matrix, porcine intestinal submucosa, and fiber-based natural materials, but it offered higher tensile strength than the other three. The quality of the evidence in this field was found to be poor. The reasons for downgrading were analyzed, and recommendations for future research included more rigor in study design, more transparency in result reporting, more standardization of animal models and follow-up time for better evaluation of the remodeling and regenerative performance of abdominal wall hernia repair meshes, and less biological risk in clinical translation.

Long-Term Outcomes in Complex Abdominal Wall Reconstruction Repaired With Absorbable Biologic Polymer Scaffold (Poly-4-Hydroxybutyrate)

Introduction

After promising early outcomes in the use of absorbable biologic mesh for complex abdominal wall reconstruction, significant criticism has been raised over the longevity of these repairs after its 2-year resorption profile.

Methods

This is the long-term (5-year) follow-up analysis of our initial experience with the absorbable polymer scaffold poly-4-hydroxybutyrate (P4HB) mesh compared with a consecutive contiguous group treated with porcine cadaveric mesh for complex abdominal wall reconstructions. Our clinical analysis was performed using Stata 14.2 and Excel 16.16.23.

Results

After a 5-year follow-up period, the P4HB group (n = 31) experienced lower rates of reherniation (12.9% vs 38.1%; P = 0.017) compared with the porcine cadaveric mesh group (n = 42). The median interval in months to recurrent herniation was similar between groups (24.3 vs 20.8; P = 0.700). Multivariate logistic regression analysis on long-term outcomes identified smoking (P = 0.004), African American race (P = 0.004), and the use of cadaveric grafts (P = 0.003) as risks for complication while smoking (P = 0.034) and the use of cadaveric grafts (P = 0.014) were identified as risks for recurrence. The long-term cost analysis showed that P4HB had a $10,595 per case costs savings over porcine cadaveric mesh.

Conclusions

Our study identified the superior outcomes in clinical performance and a value-based benefit of absorbable biologic P4HB scaffold persisted after the 2-year resorption timeframe. Data analysis also confirmed the use of porcine cadaveric grafts independently contributed to the incidence of complications and recurrences.

Fundamentals of Extracellular Matrix Biomaterial Assimilation: Effect of Suture Type on Attachment Strength and Cell Repopulation

The clinical results with extracellular matrix biomaterials are confounded by expectations of material response based on years of experience with permanent or degradable synthetic polymers. However, the remodeling or assimilation of extracellular matrix biomaterials is dictated by cell-mediated processes rather than fibrous encapsulation or hydrolytic degradation. Previously, we found that tissue adherence and revascularization were dictated by proximity with de-epithelialized host tissue. We now investigate the effects of polymer and fixation type on attachment strength and rate of cell repopulation in an intra-abdominal implant model.

Absorbable Polyglactin vs. Non-Cross-linked Porcine Biological Mesh for the Surgical Treatment of Infected Incisional Hernia

BACKGROUND

The use of absorbable meshes during contaminated or infected incisional hernia (IH) repair is associated with high morbidity and recurrence rates. Biological meshes might be more appropriate but have been described in highly heterogeneous series. This study aimed at comparing the efficacy of absorbable vs. biological meshes for the treatment of contaminated or infected IH in a homogeneous series with a standardized technique.

METHODS

Data of all patients operated on between 2008 and 2015 for contaminated or infected IH, using an absorbable (A) Vicryl® or a biological (B) Strattice® mesh, were reviewed. Patient characteristics, infectious complication rates, and recurrence-free outcome (RFO) were compared between the two groups. A propensity score methodology was applied to a Cox regression model to deal with unbalanced characteristics between groups.

RESULTS

Patient demographics in A (n = 57) and in B (n = 24) were similar except that B patients had larger parietal defects (p < 0.001) and higher Center for Disease Control (CDC) wound class (p = 0.034). Patients in A had statistically significantly more postoperative early (61.4% vs. 33.3%, p = 0.03) and late (31.2% vs. 8.3%, p = 0.046) infectious complications. Six-, 12-, and 36-month RFO rates were 77%, 47%, and 24%, and 96%, 87%, and 82% in A and B, respectively, p < 0.001. Raw multivariable Cox regression analysis found that B (HR = 0.1, 95% CI [0.03-0.34], p < 0.001) was independently associated with prolonged RFO (HR = 0.091, 95% CI [0.045-0.180], p < 0.001).

CONCLUSION

Biological meshes seem to be superior to absorbable meshes in patients with contaminated or infected incisional hernia. These results need to be confirmed by prospective randomized trials.

Squid Ring Teeth-coated Mesh Improves Abdominal Wall Repair

Background

Hernia repair is a common surgical procedure with polypropylene (PP) mesh being the standard material for correction because of its durability. However, complications such as seroma and pain are common, and repair failures still approach 15% secondary to poor tissue integration. In an effort to enhance mesh integration, we evaluated the applicability of a squid ring teeth (SRT) protein coating for soft-tissue repair in an abdominal wall defect model. SRT is a biologically derived high-strength protein with strong mechanical properties. We assessed tissue integration, strength, and biocompatibility of a SRT-coated PP mesh in a first-time pilot animal study.

Methods

PP mesh was coated with SRT (SRT-PP) and tested for mechanical strength against uncoated PP mesh. Cell proliferation and adhesion studies were performed in vitro using a 3T3 cell line. Rats underwent either PP (n = 3) or SRT-PP (n = 6) bridge mesh implantation in an anterior abdominal wall defect model. Repair was assessed clinically and radiographically, with integration evaluated by histology and mechanical testing at 60 days.

Results

Cell proliferation was enhanced on SRT-PP mesh. This was corroborated in vivo by abdominal wall histology, dramatically diminished craniocaudal mesh contraction, improved strength testing, and higher tissue failure strain. There was no increase in seroma or visceral adhesion formation. No foreign body reactions were noted on liver histology.

Conclusions

SRT applied as a coating appears to augment mesh-tissue integration and improve abdominal wall stability following bridged repair. Further studies in larger animals will determine its applicability for hernia repair in patients.

Comparison of biological and alloplastic meshes in ventral incisional hernia repair

PURPOSE

The aim of our retrospective analysis was to compare the results of incisional hernia repair by porcine small intestinal submucosa-derived (SIS) meshes with those obtained by alloplastic polypropylene-based (PP) meshes in comparable surgical indications by matched-pair design. We hypothesized that in incisional hernia, SIS mesh repair is associated with fewer recurrences and SSO than PP mesh repair in incisional hernias.

METHODS

Twenty-four matched pairs (SIS vs. PP mesh repair between 1 January 2005 and 31 December 2013) were identified by matching criteria: gender, age, comorbidities, body mass index, EHS hernia classification, mesh implantation technique, CDC wound classification, and source of contamination/primary surgery leading to incisional hernia. Minimal follow-up time was 24 months. Means and standard deviations were compared by paired t test; categorial data were compared by McNemar's test. Poisson's distribution and negative binominal distribution were employed to detect significant correlation.

RESULTS

There were no statistically significant differences between both groups in the pre- and perioperative factors and the follow-up times. There were significantly more wound complications (19 vs. 12, p = 0.041), longer hospital stay (22.0 ± 6.3 vs. 12.0 ± 3.1 days, p = 0.010), and significantly more recurrent hernias (25 vs. 12.5%, p = 0.004) after SIS mesh repair. Both the Poisson's distribution and the negative binominal distribution unveiled significantly more complication points (3-6 vs. 1-2) per month after SIS mesh repair.

CONCLUSION

There is no advantage of SIS meshes compared to PP meshes in incisional hernia repair with different degrees of wound contamination in this matched-pair analysis. Further prospective and randomized trials or at least registry studies such as the EHS register with standardized and defined conditions are warranted.

Characterization of host response, resorption, and strength properties, and performance in the presence of bacteria for fully absorbable biomaterials for soft tissue repair

PURPOSE

The objective was to evaluate the host response, resorption, and strength properties, and to assess the performance in the presence of bacteria for Phasix™ Mesh (Phasix™) and Gore® Bio-A® Tissue Reinforcement (Bio-A®) in preclinical models.

METHODS

In a rat model, one mesh (2 × 2 cm) was implanted subcutaneously in n = 60 rats. Animals were euthanized after 2, 4, 8, 12, 16, or 24 weeks (n = 5/mesh/time point), and implant sites were assessed for host inflammatory response and overall fibrotic repair thickness. In a rabbit model, meshes (3.8 cm diameter) were bilaterally implanted in subcutaneous pockets in n = 20 rabbits (n = 10 rabbits/mesh) and inoculated with 108 CFU clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). One mesh type was implanted per animal. Animals were euthanized after 7 days, and implants were assessed for abscess formation, bacterial colonization, and mechanical strength.

RESULTS

In the rat study, Phasix™ and Bio-A® exhibited similar biocompatibility, although Bio-A® demonstrated a significantly greater inflammatory response at 4 weeks compared to Phasix™ (p < 0.01). Morphometric analysis demonstrated rapid resorption of Bio-A® implants with initially thicker repair sites at 2, 4, 8, and 12 weeks (p < 0.0001), which transitioned to significantly thinner sites compared to Phasix™ at 16 and 24 weeks (p < 0.0001). In the rabbit bacterial inoculation study, Phasix™ exhibited significantly lower abscess score (p < 0.001) and bacterial colonization (p < 0.01), with significantly greater mechanical strength than Bio-A® (p < 0.001).

CONCLUSIONS

Host response, resorption, repair thickness, strength, and bacterial colonization suggest a more stable and favorable outcome for monofilament, macroporous devices such as Phasix™ relative to multifilament, microporous devices such as Bio-A® over time.