Clinical outcomes of biologic mesh: where do we stand?

Modular Bioreactor Design for Directed Tendon/Ligament Tissue Engineering

Functional tissue-engineered tendons and ligaments remain to be prepared in a reproducible and scalable manner. This study evaluates an acellular 3D extracellular matrix (ECM) scaffold for tendon/ligament tissue engineering and their ability to support strain-induced gene regulation associated with the tenogenesis of cultured mesenchymal stromal cells. Preliminary data demonstrate unique gene regulation patterns compared to other scaffold forms, in particular in Wnt signaling. However, the need for a robust bioreactor system that minimizes process variation was also evident. A design control process was used to design and verify the functionality of a novel bioreactor. The system accommodates 3D scaffolds with clinically-relevant sizes, is capable of long-term culture with customizable mechanical strain regimens, incorporates in-line load measurement for continuous monitoring and feedback control, and allows a variety of scaffold configurations through a unique modular grip system. All critical functional specifications were met, including verification of physiological strain levels from 1–10%, frequency levels from 0.2–0.5 Hz, and accurate load measurement up to 50 N, which can be expanded on the basis of load cell capability. The design process serves as a model for establishing statistical functionality and reliability of investigative systems. This work sets the stage for detailed analyses of ECM scaffolds to identify critical differentiation signaling responses and essential matrix composition and cell–matrix interactions.

Onlay Poly-4-Hydroxybutyrate (P4HB) Mesh for Complex Hernia: Early Clinical and Patient Reported Outcomes

BACKGROUND

While mesh re-enforcement and advanced surgical techniques are cornerstones of complex ventral hernia repair (CVHR), the risk of complications and recurrence is common. We aim to evaluate the efficacy, safety, and patient reported outcomes (PROs) of patients undergoing CVHR with onlay Poly-4-hydroxybutyrate (P4HB).

METHODS

Adult (>18 y old) patients undergoing VHR with P4HB (Phasix) in the onlay plane by a single surgeon from 01/2015 to 05/2020 were reviewed. VHR was considered complex if patients had significant co-morbidities, large abdominal wall defects, a history of extensive abdominal surgery, and/or concurrent intra-abdominal pathology. A composite of postoperative outcomes including surgical site occurrences (SSO), surgical site infection (SSI), and surgical site occurrences requiring procedural intervention (SSOpi), as well as PROs as defined by the Abdominal Hernia-Q (AHQ), were analyzed.

RESULTS

A total of 51 patients were included with average age and body mass index of 56.4 and 29.9 kg/m². Median follow up was 20 mo with a hernia recurrence rate of 5.9% (n = 3). 21 patients had an SSO (41.2%), 8 had an SSI (15.7%), and 6 had an SSOpi (11.8%). There was an association with Ventral Hernia Working Group ≥ 2 and development of SSO. There was a significant improvement in overall PROs (P < 0.0001) with no difference in those patients with and without complications (P > 0.05).

CONCLUSION

For hernia patients with large defects and complex intra-abdominal pathology, a safe and effective repair is difficult. The use of onlay P4HB was associated with acceptable postoperative outcomes and recurrence rate.

Poly-4-hydroxybutyrate (Phasix™) mesh onlay in complex abdominal wall repair

BACKGROUND

Poly-4-hydroxybutyric acid (P4HB, Phasix™) is a biosynthetic polymer that degrades by hydrolysis that can be woven into a mesh for use in soft tissue reinforcement. Herein, we describe our initial experience performing complex abdominal wall repair (CAWR) utilizing component separation and P4HB mesh as onlay reinforcement.

METHODS

All patients undergoing CAWR between June 2014 and May 2017 were followed prospectively for postoperative outcomes. Only those patients who underwent components separation with primary repair of the fascial edges followed by onlay of P4HB mesh were included in this study.

RESULTS

105 patients (52 male, 53 female; mean age 59.2 years, range 22-84) met inclusion criteria. Mean BMI was 29.1 (range 16-48); 52% patients had prior attempted hernia repair, most with multiple medical comorbidities (71% of patients with ASA 3 or greater). 30% of cases were not clean at the time of repair (CDC class 2 or greater). Median follow-up was 36 months (range 9-63). Eighteen patients (17%) developed a hernia recurrence ranging from 2 to 36 months postoperatively. Five (5%) patients developed a localized superficial infection treated with antibiotics, three (2.8%) required re-operation for non-healing wounds, and six (6%) patients developed seroma.

CONCLUSIONS

These data demonstrate a relatively low rate of hernia recurrence, seroma, and other common complications of CAWR in a highly morbid patient population. Importantly, the rate of mesh infection was low and no patients required complete mesh removal, even when placed into a contaminated or infected surgical field.

Integration of Biomechanical and Biological Characterization in the Development of Porous Poly(caprolactone)-Based Membranes for Abdominal Wall Hernia Treatment

Aims. Synthetic meshes are the long-standing choice for the clinical treatment of abdominal wall hernias: the associated long-term complications have stimulated the development of a new generation of bioresorbable prostheses. In this work, polycaprolactone (PCL) porous membranes prepared by solvent casting/porogen leaching of PCL/poly(ethylene glycol) (PEG) blends with different compositions (different PCL/PEG weight ratios and PEG molecular weights) were investigated to be applied in the field. An optimal porous membrane structure was selected based on the evaluation of physicochemical, biomechanical, and in vitro biological properties, compared to a reference commercially available hernia mesh (CMC). Findings. Selected PCL7-2i membranes, derived from PCL/PEG 70/30 (PCL: Mw 70,000-90,000 Da; PEG: 35,000 Da), showed suitable pore size for the application, intermediate surface hydrophilicity, and biomimetic mechanical properties. In vitro cell tests performed on PCL7-2i membranes showed their cytocompatibility, high cell growth during 21 days, a reduced production of proinflammatory IL-6 with respect to CMC, and a significant secretion of collagen type I. Conclusions. PCL7-2i membranes showed biomimetic biomechanical properties and in vitro biological properties similar to or even better than - in the case of anti-inflammatory behavior and collagen production - CMC, a commercially available product, suggesting potentially improved integration in the host tissue.

"Complex abdominal wall" management: evidence-based guidelines of the Italian Consensus Conference

To date, there is no shared consensus on a definition of a complex abdominal wall in elective surgery and in the emergency, on indications, technical details, complications, and follow-up. The purpose of the conference was to lay the foundations for a homogeneous approach to the complex abdominal wall with the primary intent being to attain the following objectives: (1) to develop evidence-based recommendations to define “complex abdominal wall”; (2) indications in emergency and in elective cases; (3) management of “complex abdominal wall”; (4) techniques for temporary abdominal closure. The decompressive laparostomy should be considered in a case of abdominal compartment syndrome in patients with critical conditions or after the failure of a medical treatment or less invasive methods. In the second one, beyond different mechanism, patients with surgical emergency diseases might reach the same pathophysiological end point of trauma patients where a preventive “open abdomen” might be indicated (a temporary abdominal closure: in the case of a non-infected field, the Wittmann patch and the NPWT had the best outcome followed by meshes; in the case of an infected field, NPWT techniques seem to be the preferred). The second priority is to create optimal both general as local conditions for healing: the right antimicrobial management, feeding—preferably by the enteral route—and managing correctly the open abdomen wall. The use of a mesh appears to be—if and when possible—the gold standard. There is a lot of enthusiasm about biological meshes. But the actual evidence supports their use only in contaminated or potentially contaminated fields but above all, to reduce the higher rate of recurrences, the wall anatomy and function should be restored in the midline, with or without component separation technique. On the other site has not to be neglected that the use of monofilament and macroporous non-absorbable meshes, in extraperitoneal position, in the setting of the complex abdomen with contamination, seems to have a cost effective role too. The idea of this consensus conference was mainly to try to bring order in the so copious, but not always so “evident” literature utilizing and exchanging the expertise of different specialists.

Lightweight, Highly Permeable, Biocompatible, and Antiadhesive Composite Meshes for Intraperitoneal Repairs

Ventral hernia is a public health issue and millions of meshes are used to repair abdominal wall defects every year. Polypropylene-based composite meshes represent an important class of materials for intraperitoneal repair, but the meshes generally give rise to infection, seroma, migration, and adhesion, leading to severe consequence or even reoperation. Here, a facile and versatile one-way fabrication of lightweight, highly permeable, and biocompatible composite meshes with superior antiadhesion properties is proposed by modifying polypropylene meshes with well-defined polydopamine nanocoating. The resulting composite meshes are found to significantly enhance the biocompatibility and antiadhesion effect in rat model. The scalable production and excellent biomedical properties of composite meshes make them a promising candidate for future-generation ventral hernia repair materials.

Treatment of abdominal wall hernia with suture, or polypropylene, or collagen prosthesis

PURPOSE

To develop an experimental model for incisional hernias and to compare morphological and functional aspects of hernia repairs by suture, polypropylene mesh and collagen mesh.

METHODS

A defect measuring 7cm x 2cm was created in the anterior abdominal of 28 New Zealand male rabbits, divided into four groups (n = 7): (1) control, (2) suture of the anterior sheath of the rectus abdominal muscle, (3) setting of polypropylene mesh, and (4) setting of collagen mesh. On the 90th postoperative day, the animals were examined to verify the presence of incisional hernia. Samples of abdominal wall and scar were collected for histological study.

RESULTS

Incisional hernia was identified in 85.7% of the control group, 57.1% of the suture group, 42.9% of the collagen mesh group, and none in the polypropylene mesh group (p = 0.015). Mesh exposure could be identified in 71.4% of the animals in group 3 and in no animal in group 4 (p = 0.021). The polypropylene mesh is effective in the treatment of abdominal wall defects, causing an intense inflammatory reaction.

CONCLUSION

The collagen mesh is biocompatible, producing a minimal inflammatory reaction, but fails in the treatment of abdominal wall defects.

Strain gradient development in 3-dimensional extracellular matrix scaffolds during in vitro mechanical stimulation

This study analyzed strain variations in 3D ECM scaffolds using a membrane-adherent model (MM) and a direct elongation model (DM). Computational models were solved for target strains from 1 to 10% at varied scaffold thicknesses and intra-scaffold slices. DM strain profiles were uniform within the scaffold and independent of thickness. However, a wide range of strains developed with substantial volume experiencing significantly off-target strain. MM strain profiles varied throughout the scaffold, exhibiting significantly reduced average strain with increasing thickness. These findings are important for tissue engineering studies since biological responses are commonly attributed to a single strain level that only partially describes the mechanical condition, making it difficult to develop precise causal relationships. Spatial strain variations and reduced average strain may warrant targeted sampling for cell response and should be taken into consideration by investigators using large-volume 3D scaffolds when engineering mechanically sensitive tissues.

Outcomes of Retromuscular Porcine Biologic Mesh Repairs Using Transversus Abdominis Release Reconstruction

BACKGROUND

Optimal mesh reinforcement and operative technique for major abdominal wall reconstructions (AWR) remain debatable. Posterior component separation via transversus abdominis release (TAR) allows for wide sublay mesh reinforcement with durable reconstruction, and has been gaining popularity in recent years. Although biologic mesh has been associated with mixed results, outcomes of AWR with bioprosthetics have not been well elucidated to date. We evaluated our outcomes of TAR reconstructions with retromuscular porcine biologic mesh reinforcement.

STUDY DESIGN

Consecutive patients undergoing AWR using TAR with biologic mesh sublay reinforcement were identified in our prospective databases and analyzed. We characterized patient demographics and perioperative details. Main outcomes measures included wound complications and hernia recurrence.

RESULTS

Between 2007 and 2014, seventy-seven patients (mean age 56 years, mean BMI 35 kg/m(2)) underwent AWR using TAR with biologic mesh. Mean hernia size was 306 ± 128 cm(2) with mean width of 14.3 ± 3.3 cm. The vast majority of patients had grade 3 hernias (92%) and more than half had a history of wound infection (55%). There were 22 (28.6%) surgical site infections consisting of 14 deep, 7 superficial, and 1 organ-space surgical site infections. There were no incidences of chronic mesh infection or explantation. In patients with at least 12 months follow-up (mean duration 28.2 months), there were 8 (12.5%) recurrences.

CONCLUSIONS

Complex hernias repaired with TAR and retromuscular porcine biologic mesh reinforcement are associated with a low rate of serious perioperative wound/mesh complications. Additionally, our approach resulted in a fairly low rate of hernia recurrences in this complex cohort of patients. We believe that the TAR approach and retromuscular mesh placement can be beneficial when biologic mesh reinforcement is chosen during complex and/or contaminated abdominal wall reconstructions.

Inhibition of COX1/2 alters the host response and reduces ECM scaffold mediated constructive tissue remodeling in a rodent model of skeletal muscle injury

Extracellular matrix (ECM) has been used as a biologic scaffold material to both reinforce the surgical repair of soft tissue and serve as an inductive template to promote a constructive tissue remodeling response. Success of such an approach is dependent on macrophage-mediated degradation and remodeling of the biologic scaffold. Macrophage phenotype during these processes is a predictive factor of the eventual remodeling outcome. ECM scaffolds have been shown to promote an anti-inflammatory or M2-like macrophage phenotype in vitro that includes secretion of downstream products of cycolooxygenases 1 and 2 (COX1/2). The present study investigated the effect of a common COX1/2 inhibitor (Aspirin) on macrophage phenotype and tissue remodeling in a rodent model of ECM scaffold treated skeletal muscle injury. Inhibition of COX1/2 reduced the constructive remodeling response by hindering myogenesis and collagen deposition in the defect area. The inhibited response was correlated with a reduction in M2-like macrophages in the defect area. The effects of Aspirin on macrophage phenotype were corroborated using an established in vitro macrophage model which showed a reduction in both ECM induced prostaglandin secretion and expression of a marker of M2-like macrophages (CD206). These results raise questions regarding the common peri-surgical administration of COX1/2 inhibitors when biologic scaffold materials are used to facilitate muscle repair/regeneration.

STATEMENT OF SIGNIFICANCE

COX1/2 inhibitors such as nonsteroidal anti-inflammatory drugs (NSAIDs) are routinely administered post-surgically for analgesic purposes. While COX1/2 inhibitors are important in pain management, they have also been shown to delay or diminish the healing process, which calls to question their clinical use for treating musculotendinous injuries. The present study aimed to investigate the influence of a common NSAID, Aspirin, on the constructive remodeling response mediated by an ECM scaffold (UBM) in a rat skeletal muscle injury model. The COX1/2 inhibitor, Aspirin, was found to mitigate the ECM scaffold-mediated constructive remodeling response both in an in vitro co-culture system and an in vivo rat model of skeletal muscle injury. The results presented herein provide data showing that NSAIDs may significantly alter tissue remodeling outcomes when a biomaterial is used in a regenerative medicine/tissue engineering application. Thus, the decision to prescribe NSAIDs to manage the symptoms of inflammation post-ECM scaffold implantation should be carefully considered.

Mesh herniorrhaphy with simultaneous colorectal surgery: a case-matched study from the American College of Surgeons National Surgical Quality Improvement Program

BACKGROUND

The aim of this study is to evaluate the impact of concurrent mesh herniorrhaphy on short-term outcomes of colorectal surgery by using a large, nationwide database.

METHODS

Patients who underwent simultaneous ventral hernia repair (VHR) and colorectal surgery between 2005 and 2010 were identified from the American College of Surgeons National Surgical Quality Improvement Program. Patients who underwent VHR with mesh repair were case matched with patients who underwent VHR without mesh based on the type of colorectal procedure, diagnosis, and American Society of Anesthesiologists score.

RESULTS

Two hundred sixty-two patients who underwent VHR with mesh were case matched with 524 patients who underwent VHR without mesh. Mean operating time was significantly longer in patients who underwent VHR with mesh (195.8 ± 98.7 vs 164.3 ± 84.4 minutes, P < .001). Postoperative morbidity (P = .58), mortality (P = .27), superficial surgical site infection (SSI) (P = .14), deep SSI (P = .38), organ space SSI (P = .17), wound disruption (P > .99), reoperation (P = .48), and length of hospital stay (P = .71) were comparable between the groups.

CONCLUSION

The American College of Surgeons National Surgical Quality Improvement Program data suggest that VHR with mesh does not increase 30-day mortality, medical or surgical morbidity in colorectal surgery setting.