Characterization of poly-4-hydroxybutyrate mesh for hernia repair applications

Emerging materials and technologies for advancing bioresorbable surgical meshes

Surgical meshes play a significant role in the treatment of various medical conditions, such as hernias, pelvic floor issues, guided bone regeneration, and wound healing. To date, commercial surgical meshes are typically made of non-absorbable synthetic polymers, notably polypropylene and polytetrafluoroethylene, which are associated with postoperative complications, such as infections. Biological meshes, based on native tissues, have been employed to overcome such complications, though mechanical strength has been a main disadvantage. The right balance in mechanical and biological performances has been achieved by the advent of bioresorbable meshes. Despite improvements, recurrence of clinical complications associated with surgical meshes raises significant concerns regarding the technical adequacy of current materials and designs, pointing to a crucial need for further development. To this end, current research focuses on the design of meshes capable of biomimicking native tissue and facilitating the healing process without post-operative complications. Researchers are actively investigating advanced bioresorbable materials, both synthetic polymers and natural biopolymers, while also exploring the performance of therapeutic agents, surface modification methods and advanced manufacturing technologies such as 4D printing. This review seeks to evaluate emerging biomaterials and technologies for enhancing the performance and clinical applicability of the next-generation surgical meshes. STATEMENT OF SIGNIFICANCE: In the ever-transforming landscape of regenerative medicine, the embracing of engineered bioabsorbable surgical meshes stands as a key milestone in addressing persistent challenges and complications associated with existing treatments. The urgency to move beyond conventional non-absorbable meshes, fraught with post-surgery complications, emphasises the necessity of using advanced biomaterials for engineered tissue regeneration. This review critically examines the growing field of absorbable surgical meshes, considering their potential to transform clinical practice. By strategically combining mechanical strength with bioresorbable characteristics, these innovative meshes hold the promise of mitigating complications and improving patient outcomes across diverse medical applications. As we navigate the complexities of modern medicine, this exploration of engineered absorbable meshes emerges as a promising approach, offering an overall perspective on biomaterials, technologies, and strategies adopted to redefine the future of surgical meshes.

Long-term results with biosynthetic absorbable P4HB mesh in ventral abdominal wall repair: a multicentre analysis

BACKGROUND

The aim of this multicentre study was to analyse the outcomes of biosynthetic absorbable poly-4-hydroxybutyrate (P4HB) prosthesis implantation in patients undergoing ventral hernia repair (VHR) in the context of different degrees of contamination.

METHODS

From May 2016 to December 2021, a multicentre retrospective analysis of patients who underwent elective or urgent hernia repair with P4HB prosthesis was performed in seven hospitals in Spain and Portugal. Patients with a postoperative follow-up of less than 20 months and those within the theoretical period of prosthesis resorption were excluded from the study. Regarding the degree of contamination, patients were assessed according to the modified Ventral Hernia Working Group (VHWG) classification. Epidemiological data, hernia characteristics, surgical and postoperative variables (Clavien-Dindo classification) of these patients were analyzed. Risk factors related to long-term recurrence were studied by a multivariate analysis.

RESULTS

In 236 cases of P4HB prosthesis implantation, repair in cases of Grade 3 was the most frequent (49.1%), followed by Grade 2 in 42.3% of cases and Grade 1 in 8.4%. The most frequent complications were Grade 1, with the majority occurring during the first year. The overall rate of surgical site occurrences (SSO) was 30%. The hernia recurrence rate was 14.4% (n = 34), with a mean postoperative follow-up time of 41 months (22-61). The multivariate analysis showed that the onlay location of the mesh (OR 1.07; CI 1.42-2.70, p = 0.004) was a significant independent risk factor for recurrence.

CONCLUSIONS

The use of a P4HB bioresorbable mesh for the VHR with different degrees of contamination leads to favourable results overall, with an acceptable rate of hernia recurrence. The onlay location of the P4HB prosthesis is the main factor in recurrence in both elective and emergency settings.

Fabrication of Bioresorbable Barrier Membranes from Gelatin/Poly(4-Hydroxybutyrate) (P4HB)

Dental implant surgery is a procedure that replaces damaged or missing teeth with an artificial implant. During this procedure, guided bone regeneration (GBR) membranes are commonly used to inhibit the migration of epithelium and GBR at the surgical sites. Due to its biodegradability, good biocompatibility, and unique biological properties, gelatin (GT) is considered a suitable candidate for guiding periodontal tissue regeneration. However, GT-based membranes come with limitations, such as poor mechanical strength and mismatched degradation rates. To confront this challenge, a series of GT/poly(4-hydroxybutyrate) (P4HB) composite membranes are fabricated through electrospinning technology. The morphology, composition, wetting properties, mechanical properties, biocompatibility, and in vivo biodegradability of the as-prepared composite membranes are carefully characterized. The results demonstrate that all the membranes present excellent biocompatibility. Moreover, the in vivo degradation rate of the membranes can be manipulated by changing the ratio of GT and P4HB. The results indicate that the optimized GT/P4HB membranes with a high P4HB content (75%) may be suitable for periodontal tissue engineering because of their good mechanical properties and biodegradation rate compatible with tissue growth.

The use of poly-4-hydroxybutyrate (P4HB, Phasix™) mesh in ventral hernia repair: a systematic review and meta-analysis

PURPOSE/BACKGROUND

Despite the growing use of bioabsorbable mesh in ventral hernia repairs (VHR), the evidence of its impact on patient outcomes remains limited. This study aims to investigate the efficacy and safety profile of poly-4-hydroxybutyrate (P4HB) mesh for ventral hernia repair through a systematic review and meta-analysis.

METHODS

A literature search of five databases (PubMed, Embase, Ovid, Medline, and Google Scholar) produced a list of publications that analyzed the use of P4HB mesh in ventral hernia repair in both clean and contaminated cases. The primary postoperative outcomes of hernia recurrence, surgical site infections (SSI), and any complications were analyzed through a pooled meta-analysis.

RESULTS

In our systematic review, 21 studies met the inclusion criteria with a total of 1858 patients (933 males and 925 females) and an average age of 56.8 years. The median follow-up ranged from 1.6 to 62.3 months. In our meta-analysis, the use of P4HB mesh in VHR in proportion of events demonstrated a recurrence rate of 9% [6%; 15%], SSI of 10% [6%; 16%] and 35% [9%; 42%] for rate of any complications. Sub-meta-analysis restricted to studies with follow up > 18 months continues to show low rates of recurrence of 9% (95%CI, 4-17%), SSI of 9% (95%CI, 4-16%), and 31% (95%CI, 23-41%) for any complications.

CONCLUSION

Our study demonstrates that the use of P4HB mesh is both safe and effective in ventral hernia repairs. When further analyzed past 18 months, the time where P4HB mesh fully resorbs, the rates of hernia recurrence, SSI, and any complications remain low of upwards of 5 years and comparable to the rates seen in synthetic and biologics in similar patient populations.

Ventral Hernia Reconstruction with GORE ENFORM Biomaterial

Introduction: Ventral hernia repair (VHR) is one of the most common surgeries performed in the United States. Degradable mesh is the recommended choice for patients presenting with high-risk co-morbidities or increased risk for infection. GORE® ENFORM BiomaterialTM is a biosynthetic degradable mesh that has recently been approved for use in ventral hernia reconstruction with no reports of its clinical outcomes. Methods: This study was a single surgeon case series. Patients were included in the study if they underwent VHR with GORE® ENFORM BiomaterialTM. The decision to use GORE® ENFORM BiomaterialTM was the senior surgeon's decision based on the patient's center for disease control classification. Patient comorbidities, hernia characteristics, postoperative hernia recurrence, and surgical site occurrences (SSOs) were collected at in-patient follow-up appointments and chart review. Patients were asked to complete preoperative and postoperative patient-reported outcomes (PROs) using the Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Intensity short form 3a and the hernia-specific quality of life (HerQLes) survey. Results: A total of 15 patients were included in this study. The average length of follow-up was 315 days. Postoperatively, 26.7% of patients had an SSO with 4 surgical site infections. Two patients required an operative washout with mesh removal. One patient experienced hernia recurrence. Eight of the 15 patients completed preoperative and postoperative PROs. Conclusion: This is the first clinical study to report the outcomes of ventral hernia repair using ENFORM mesh. These results show that Enform mesh is an option to consider in complex ventral hernia reconstruction.

Ventral hernia repair using bioresorbable poly-4-hydroxybutyrate mesh in clean and contaminated surgical fields: a systematic review and meta-analysis

PURPOSE

Use of biologic or synthetic mesh in hernia repair shifts is based on evolving evidence. Poly-4-hydroxybutyrate (P4HB) biosynthetic mesh is a potential alternative to biologic and synthetic mesh in ventral hernia repair (VHR). This meta-analysis assesses the efficacy of P4HB mesh in clean and contaminated surgical settings.

METHODS

Two authors searched literature on PubMed, reviewing titles and abstracts of all articles to determine inclusion eligibility. Post-operative data were compared via transformation method to convert the proportion of patients with the outcome of interest into a suitable quantity for random-effects synthesis using STATA software.

RESULTS

Initial search yielded 287 citations. Six studies were included and categorized on whether hernia repairs were conducted in clean (CDC class I) or contaminated cases (CDC class II-IV). The pooled proportion of surgical site infection (SSI), surgical site occurrence (SSO), hernia recurrence, total surgical complications, and reoperation were calculated in 391 clean and 81 contaminated cases. For clean vs. contaminated cases, the following pooled proportions were noted: SSI (2% (CI 0-7%) vs 9% (CI 0-025) (p = 0.03), SSO: 14% (CI 5-25%) vs 35% (CI 22-50%) (p = 0.006), hernia recurrence (8% (CI 1-19%) vs 4% (CI 0-12%) (p = 0.769); surgical complications (17% (CI 6-32%) vs 50% (CI 27-72%) (p = 0.009). Reoperation data were available in 298 clean cases across four studies: 5% (CI 0-15%).

CONCLUSIONS

P4HB biosynthetic mesh may be more effective than previously thought, particularly in clean wounds. P4HB may also be superior to biologic mesh when compared to clinical trial data. Further research is necessary for more direct comparison.

The Regenerative Capacity of Tissue-Engineered Amniotic Membranes

Scaffolds can be introduced as a source of tissue in reconstructive surgery and can help to improve wound healing. Amniotic membranes (AMs) as scaffolds for tissue engineering have emerged as promising biomaterials for surgical reconstruction due to their regenerative capacity, biocompatibility, gradual degradability, and availability. They also promote fetal-like scarless healing and provide a bioactive matrix that stimulates cell adhesion, migration, and proliferation. The aim of this study was to create a tissue-engineered AM-based implant for the repair of vesicovaginal fistula (VVF), a defect between the bladder and vagina caused by prolonged obstructed labor. Layers of AMs (with or without cross-linking) and electrospun poly-4-hydroxybutyrate (P4HB) (a synthetic, degradable polymer) scaffold were joined together by fibrin glue to produce a multilayer scaffold. Human vaginal fibroblasts were seeded on the different constructs and cultured for 28 days. Cell proliferation, cell morphology, collagen deposition, and metabolism measured by matrix metalloproteinase (MMP) activity were evaluated. Vaginal fibroblasts proliferated and were metabolically active on the different constructs, producing a distributed layer of collagen and proMMP-2. Cell proliferation and the amount of produced collagen were similar across different groups, indicating that the different AM-based constructs support vaginal fibroblast function. Cell morphology and collagen images showed slightly better alignment and organization on the un-cross-linked constructs compared to the cross-linked constructs. It was concluded that the regenerative capacity of AM does not seem to be affected by mechanical reinforcement with cross-linking or the addition of P4HB and fibrin glue. An AM-based implant for surgical repair of internal organs requiring load-bearing functionality can be directly translated to other types of surgical reconstruction of internal organs.

Progress of biodegradable polymer application in cardiac occluders

Cardiac septal defect is the most prevalent congenital heart disease and is typically treated with open-heart surgery under cardiopulmonary bypass. Since the 1990s, with the advancement of interventional techniques and minimally invasive transthoracic closure techniques, cardiac occluder implantation represented by the Amplazter products has been the preferred treatment option. Currently, most occlusion devices used in clinical settings are primarily composed of Nitinol as the skeleton. Nevertheless, long-term follow-up studies have revealed various complications related to metal skeletons, including hemolysis, thrombus, metal allergy, cardiac erosion, and even severe atrioventricular block. Thus, occlusion devices made of biodegradable materials have become the focus of research. Over the past two decades, several bioabsorbable cardiac occluders for ventricular septal defect and atrial septal defect have been designed and trialed on animals or humans. This review summarizes the research progress of bioabsorbable cardiac occluders, the advantages and disadvantages of different biodegradable polymers used to fabricate occluders, and discusses future research directions concerning the structures and materials of bioabsorbable cardiac occluders.

A novel self-gripping long-term resorbable mesh providing temporary support for open primary ventral and incisional hernia

A novel synthetic fully long-term resorbable self-gripping mesh has been recently developed to reinforce soft tissue where weakness exists during ventral hernia repair open procedures. This resorbable mesh is a macroporous, knitted, poly-L-lactide, poly-trimethylene carbonate copolymer monofilament mesh with the ProGrip™ technology, providing grips on one side of the mesh. A new poly-L-lactide, poly-trimethylene copolymer was developed to provide the required features for mechanical support during at least 20 weeks covering the critical healing period, including resistance to fatigue under cyclic loading conditions, as it occurs in patients. The yarns and mesh initial physical and biomechanical properties were characterized. Then, the mesh mechanical strength was evaluated over time. The mechanical properties of the proposed mesh were found to be above the generally recognized threshold value to mechanically support the repair site of a hernia over a 20-week period during in-vitro cyclic loading test. The mesh performance was evaluated in vivo using a published preclinical porcine model of hernia repair at 4-, 12- and 20-weeks post implantation. The burst strength of the hernia repair sites reinforced with the new mesh were higher at 4 & 12 weeks and comparable at 20 weeks to the one of the native abdominal walls. At all time points, the mesh was well tolerated with moderate inflammation and was fast integrated in the abdominal wall at 4 weeks. Particularly, the grips were nicely engulfed in the newly formed connective tissue. They must facilitate the anchoring of the mesh by their extension from the mesh and their mushroom shape. The preclinical data of the self-gripping resorbable mesh suggests that it has all the favorable characteristics for future clinical use during ventral hernia repair open procedures.

Early wound morbidity and clinical outcomes associated with P4HB mesh compared to permanent synthetic mesh in umbilical and small to medium, routine ventral hernia repairs

Background

Permanent synthetic meshes such as polypropylene (PP) have been utilized for hernia repair for decades, but concerns remain regarding potential long-term, mesh-related complications. A resorbable polymer such as poly-4-hydroxybutyrate (P4HB) represents an alternative with high initial strength, that gradually resorbs, leaving an abdominal wall that is at least as strong as it would be in its native state. We aimed to compare early wound morbidity and clinical outcomes associated with P4HB to traditional, permanent PP in umbilical and small to medium, routine ventral hernias using data from the Abdominal Core Health Quality Collaborative (ACHQC).

Methods

Inclusion criteria for the umbilical cohort included: all Centers for Disease Control and Prevention (CDC) wound classes, all Ventral Hernia Working Group (VHWG) hernia grades, and hernia defects <3 cm. The small to medium, routine ventral hernia cohort was limited to CDC class I wounds, VHWG hernia grades I and II, and hernia defects <5 cm. The study group was comprised of P4HB meshes; the comparator group was an aggregate of PP meshes. Clinical outcomes were assessed at 30 days.

Results

There was no significant difference in early wound morbidity, readmission, or reoperation between the P4HB and PP cohorts. A small number of patients experienced SSO, with ≤4% requiring procedural intervention. None of the patients (0% in all cases) experienced skin/soft tissue necrosis, infected seroma, infected hematoma, exposed/contaminated/infected mesh, enterocutaneous fistula, graft failure, or pain requiring intervention at 30-days. However, P4HB was associated with significantly greater operative time, length of stay, and use of myofascial release compared to PP (p < 0.05 in all cases).

Conclusions

Short-term clinical outcomes associated with resorbable P4HB mesh are comparable to permanent synthetic PP mesh in umbilical and small to medium, routine ventral hernia repairs, despite significant differences in operative time and length of stay. Longer-term follow-up is needed to expand on the clinical relevance of these short-term findings.

Novel Material Optimization Strategies for Developing Upgraded Abdominal Meshes

Over 20 million hernias are operated on globally per year, with most interventions requiring mesh reinforcement. A wide range of such medical devices are currently available on the market, most fabricated from synthetic polymers. Yet, searching for an ideal mesh is an ongoing process, with continuous efforts directed toward developing upgraded implants by modifying existing products or creating innovative systems from scratch. In this regard, this review presents the most frequently employed polymers for mesh fabrication, outlining the market available products and their relevant characteristics, further focusing on the state-of-the-art mesh approaches. Specifically, we mainly discuss recent studies concerning coating application, nanomaterials addition, stem cell seeding, and 3D printing of custom mesh designs.

Biosynthetic meshes in contaminated fields: where are we now? A systematic review and meta-analysis in humans

PURPOSE

Selection of an appropriate mesh reinforcement for hernia repair in contaminated fields is a significant problem for surgeons. To date the proper mesh for contaminated fields has not been found. Biosynthetic meshes have emerged as new treatment option in contaminated fields. This study aims to evaluate the postoperative outcomes of biosynthetic meshes in contaminated fields.

METHODS

Systematic electronic search (PubMed, Medline, Embase, Scopus), according to PRISMA criteria, was performed. A literature search of scientific papers was performed by two reviewers until April 2021. Articles were chosen based on reference to biosynthetic meshes, their use in infected fields, and in human subjects. GRADE methodology and the modified Newcastle-Ottawa scale were used to assess the quality of studies. According to CDC-Centers for Disease Control classes patients were divided into two subgroups, group 1 (CDC class 2) and group 2 (CDC classes 3-4).

RESULTS

The research included 21 articles and 1619 patients were analyzed. Long-term follow-up showed a significant higher recurrence rate than short-term follow-up. P < 0.001. Meta-analysis of these studies showed that the SSI were significantly higher in CDC classes 3-4 than CDC class 2 (P < 0.01). No differences were found in SSO (P = 0.06) and recurrence (P = 0.37) rate among the two groups. Phasix™ was the most common mesh in 15 studies. The mean follow-up was 23.0 months. The surgical site infection (SSI) rate was 17.3%. The surgical site occurrence (SSO) rate was 32.4%. Recurrence rate was 11.5%.

CONCLUSION

This is the first systematic review and meta-analysis on the clinical outcomes of abdominal wall repair using biosynthetic mesh in contaminated-infected settings. The results show good results in patients at high risk of postoperative wound complications. The aim of this study is to add to the growing literature on biosynthetic mesh a picture of current literature evidence to help future researchers performing further studies on this topic.

A reliable and replicable test protocol for the mechanical evaluation of synthetic meshes

Despite the worldwide spread of surgical meshes in abdominal and inguinal surgery repair, the lack of specific standards for mechanical characterization of synthetic meshes, used in hernia repair and urogynecologic surgery, makes performance comparison between prostheses undoubtedly difficult. This consequently leads to the absence of acknowledged specifications about the mechanical requirements that synthetic meshes should achieve in order to avoid patient discomfort or hernia recurrences. The aim of this study is to provide a rigorous test protocol for the mechanical comparison between surgical meshes having the same intended use. The test protocol is composed of three quasi-static test methods: (1) ball burst test, (2) uniaxial tensile test, and (3) suture retention test. For each test, post-processing procedures are proposed to compute relevant mechanical parameters from the raw data. Some of the computed parameters, indeed, could be more suitable for comparison with physiological conditions (e.g., membrane strain and anisotropy), while others (e.g., uniaxial tension at rupture and suture retention strength) are reported as they provide useful mechanical information and could be convenient for comparisons between devices. The proposed test protocol was applied on 14 polypropylene meshes, 3 composite meshes, and 6 urogynecologic devices to verify its universal applicability towards meshes of different types and produced by various manufacturers, and its repeatability in terms of coefficient of variation. The test protocol resulted easily applicable to all the tested surgical meshes with intra-subject variability characterized by coefficient of variations settled around 0.05. Its use within other laboratories could allow the determination of the inter-subject variability assessing its repeatability among users of alternative universal testing machines.

Abdominal wall hernia repair: from prosthetic meshes to smart materials

Hernia reconstruction is one of the most frequently practiced surgical procedures worldwide. Plastic surgery plays a pivotal role in reestablishing desired abdominal wall structure and function without the drawbacks traditionally associated with general surgery as excessive tension, postoperative pain, poor repair outcomes, and frequent recurrence. Surgical meshes have been the preferential choice for abdominal wall hernia repair to achieve the physical integrity and equivalent components of musculofascial layers. Despite the relevant progress in recent years, there are still unsolved challenges in surgical mesh design and complication settlement. This review provides a systemic summary of the hernia surgical mesh development deeply related to abdominal wall hernia pathology and classification. Commercial meshes, the first-generation prosthetic materials, and the most commonly used repair materials in the clinic are described in detail, addressing constrain side effects and rational strategies to establish characteristics of ideal hernia repair meshes. The engineered prosthetics are defined as a transit to the biomimetic smart hernia repair scaffolds with specific advantages and disadvantages, including hydrogel scaffolds, electrospinning membranes, and three-dimensional patches. Lastly, this review critically outlines the future research direction for successful hernia repair solutions by combing state-of-the-art techniques and materials.

Comparative long-term effectiveness between ventral hernia repairs with biosynthetic and synthetic mesh

BACKGROUND

Debate exists regarding the most appropriate type of mesh to use in ventral hernia repair (VHR). Meshes are broadly categorized as synthetic or biologic, each mesh with individual advantages and disadvantages. More recently developed biosynthetic mesh has characteristics of both mesh types. The current study aims to examine long-term follow-up data and directly compare outcomes-specifically hernia recurrence-of VHR with biosynthetic versus synthetic mesh.

METHODS

With IRB approval, consecutive cases of VHR (CPT codes 49,560, 49,561, 49,565, and 49,566 with 49,568) performed between 2013 and 2018 at a single institution were reviewed. Local NSQIP data was utilized for patient demographics, perioperative characteristics, CDC Wound Class, comorbidities, and mesh type. A review of electronic medical records provided additional variables including hernia defect size, postoperative wound events to six months, duration of follow-up, and incidence of hernia recurrence. Longevity of repair was measured using Kaplan-Meier method and adjusted Cox proportional hazards regression.

RESULTS

Biosynthetic mesh was used in 101 patients (23%) and synthetic mesh in 338 (77%). On average, patients repaired using biosynthetic mesh were older than those with synthetic mesh (57 vs. 52 years; p = .008). Also, ASA Class ≥ III was more common in biosynthetic mesh cases (70.3% vs. 55.1%; p = .016). Patients repaired with biosynthetic mesh were more likely than patients with synthetic mesh to have had a prior abdominal infection (30.7% vs. 19.8%; p = .029). Using a Kaplan-Meier analysis, there was not a significant difference in hernia recurrence between the two mesh types, with both types having Kaplan Meir 5-year recurrence-free survival rates of about 72%.

CONCLUSION

Using Kaplan-Meier analysis, synthetic mesh and biosynthetic mesh result in comparable hernia recurrence rates and surgical site infection rates in abdominal wall reconstruction patients with follow-up to as long as five years.

Fully resorbable poly-4-hydroxybutyrate (P4HB) mesh for soft tissue repair and reconstruction: A scoping review

Background

Poly-4-hydroxybutyrate (P4HB) is a fully resorbable, biologically-produced polymer with a strength and flexibility comparable to permanent synthetic polymers. The objective was to identify/summarize all peer-reviewed publications involving P4HB mesh.

Methods

A scoping review was conducted within PubMed and included articles published through October 2022.

Results

A total of n = 79 studies were identified (n = 12 in vitro/bench; n = 14 preclinical; n = 6 commentaries; n = 50 clinical). Of the clinical studies, n = 40 reported results applicable to hernia and n = 10 to plastic/reconstructive surgery and involved patients of all Centers for Disease Control (CDC) wound classes and Ventral Hernia Working Group (VHWG) grades.

Conclusion

P4HB mesh provides long-term hernia repair strength and exhibits promising clinical outcomes beyond its resorption period. Future studies should include randomized controlled trials comparing P4HB to other biomaterials, as well as optimal patient selection, operative technique, long-term outcomes, minimization of potential mesh-related complications, and potential contraindications/complications for P4HB in hernia/abdominal wall reconstruction.

Mechanical reinforcement of amniotic membranes for vesicovaginal fistula repair

INTRODUCTION

Amniotic membranes (AM) have shown its great potential in reconstructive surgery due to their regenerative capacity. However, AM is regarded to be relatively weak when applied for load-bearing purposes. This study aims to produce an AM-based scaffold that can withstand the mechanical loads applied in vesicovaginal fistula repair. Different strategies are investigated to improve the mechanical characteristics of AM.

METHODS

Single and multilayered AM, and composite constructs of AM with electrospun poly-4-hydroxybutyrate (P4HB) or bovine pericardial tissue combined with the use of fibrin glue, were mechanically tested in this study. Suture retention strength and mechanical characteristics (tensile stress, elongation, tangent modulus and maximum load) were assessed by uniaxial testing. The effect of degradation of the composite constructs on the mechanical characteristics was determined by uniaxial testing after 4 and 8 weeks.

RESULTS

Single and multilayered AM could not provide the mechanical requirements needed for surgical implantation (>2N load). AM was combined successfully with electrospun P4HB and bovine pericardium with the use of fibrin glue and were able to exceed the 2N load.

CONCLUSION

The composite constructs with AM showed sufficient mechanical characteristics for surgical implantation. Electrospun P4HB combined with AM seemed the most promising candidate since the mechanical characteristics of P4HB can be further modified to meet the requirements of the application site and the degradation of the P4HB allows a gradual transfer of load. Eventhough the scaffold is intended for fistula repair, it can potentially be applied in surgical reconstruction of other hollow organs by modifying the mechanical characteristics.

Long-Term, Prospective, Multicenter Study of Poly-4-Hydroxybutyrate Mesh (Phasix Mesh) for Hernia Repair in Cohort at Risk for Complication: 60-Month Follow-Up

BACKGROUND

Long-term resorbable mesh represents a promising technology for ventral and incisional hernia repair (VIHR). This study evaluates poly-4-hydroxybutyrate mesh (P4HB; Phasix Mesh) among comorbid patients with CDC class I wounds.

STUDY DESIGN

This prospective, multi-institutional study evaluated P4HB VIHR in comorbid patients with CDC class I wounds. Primary outcomes included hernia recurrence and surgical site infection. Secondary outcomes included pain, device-related adverse events, quality of life, reoperation, procedure time, and length of stay. Evaluations were scheduled at 1, 3, 6, 12, 18, 24, 30, 36, and 60 months. A time-to-event analysis (Kaplan-Meier) was performed for primary outcomes; secondary outcomes were reported as descriptive statistics.

RESULTS

A total of 121 patients (46 male, 75 female) 54.7 ± 12.0 years old with a BMI of 32.2 ± 4.5 kg/m 2 underwent VIHR with P4HB Mesh (mean ± SD). Fifty-four patients (44.6%) completed the 60-month follow-up. Primary outcomes (Kaplan-Meier estimates at 60 months) included recurrence (22.0 ± 4.5%; 95% CI 11.7% to 29.4%) and surgical site infection (10.1 ± 2.8%; 95% CI 3.3 to 14.0). Secondary outcomes included seroma requiring intervention (n = 9), procedure time (167.9 ± 82.5 minutes), length of stay (5.3 ± 5.3 days), reoperation (18 of 121, 14.9%), visual analogue scale-pain (change from baseline -3.16 ± 3.35 cm at 60 months; n = 52), and Carolinas Comfort Total Score (change from baseline -24.3 ± 21.4 at 60 months; n = 52).

CONCLUSIONS

Five-year outcomes after VIHR with P4HB mesh were associated with infrequent complications and durable hernia repair outcomes. This study provides a framework for anticipated long-term hernia repair outcomes when using P4HB mesh.

Establishing Peer Consensus About the Use of Long-Term Biosynthetic Absorbable Mesh for Hernia (Grades 2-3) as the Standard of Care

BACKGROUND

Standard synthetic and biologic meshes, often used in hernia repair, have commonly been used and each have their strengths but associated drawbacks. Long-term biosynthetic absorbable (LTBA) mesh has been developed to combine the strengths of synthetic and biologic meshes without the associated weaknesses. As a newer type of mesh, the supporting evidence base is still growing, and their optimum use has yet to be defined. This consensus was initiated to provide insight into those situations where a LTBA might be considered the Standard of Care in ventral hernia repair grades 2-3 (original classification, 2010) of the Ventral Hernia Working Group.

METHODS

A steering group of expert surgeons identified 35 statements, based around the evidence supporting LTBA, surgical technique, patients type most suitable for LTBA, risk-benefit of LTBA, patient and surgeon considerations, LTBA value. Surgeons involved in hernia repair received an online survey to assess consensus with these statements. Consensus was defined as high if ≥ 70% and very high if ≥ 90% of respondents agreed. Statements that had not achieved consensus agreement were revised and these were then issued for a subsequent round. Finally, 34 statements were included.

RESULTS

Two hundred fifty-five surgeons were involved. Fourteen statements (41%) achieved very high consensus, 24 achieved consensuses (≥ 70-< 90%), whilst one (3%) just failed to achieve consensus with an agreement score of 69%.

CONCLUSIONS

Expert consensus opinion about the use of LTBA for hernia (Grades 2-3) as the Standard of Care was achieved. Based on the consensus scores, the steering group derived eleven keys.

Manufacturing, characterization, and degradation of a poly(lactic acid) warp-knitted spacer fabric scaffold as a candidate for tissue engineering applications

Three-dimensional bioabsorbable textiles represent a novel technology for the manufacturing of tissue engineering scaffolds. In the present study, 3D bioabsorbable poly(lactic acid) (PLA) spacer fabric scaffolds are fabricated by warp-knitting and their potential for tissue engineering is explored in vitro. Changes in physical properties and mechanical performance with different heat setting treatments are assessed. To characterize the microenvironment experienced by cells in the scaffolds, yarn properties are investigated prior to, and during, hydrolytic degradation. The differences in yarn morphology, thermal properties, infrared spectra, and mechanical properties are investigated and monitored during temperature accelerated in vitro degradation tests in phosphate buffered saline (PBS) solution at 58 °C and pH 7.4 for 55 days. Yarn and textile cytocompatibility are tested to assess the effect of materials employed, manufacturing conditions, post processing and sterilization on cell viability, together with the cytocompatibility of the textile degradation products. Results show that the heat setting process can be used to modify scaffold properties, such as thickness, porosity, pore size and stiffness within the range useful for tissue regeneration. Scaffold degradation rate in physiological conditions is estimated by comparing yarn degradation data with PLA degradation data from literature. This will potentially allow the prediction of scaffold mechanical stability in the long term and thus its suitability for the remodelling of different tissues. Mouse calvaria preosteoblast MC3T3-E1 cells attachment and proliferation are observed on the scaffold over 12 days of in vitro culture by 4',6-diamidino-2-phenylindole (DAPI) fluorescent staining and DNA quantification. The present work shows the potential of spacer fabric scaffolds as a versatile and scalable scaffold fabrication technique, having the ability to create a microenvironment with appropriate physical, mechanical, and degradation properties for 3D tissue engineering. The high control and tunability of spacer fabric properties makes it a promising candidate for the regeneration of different tissues in patient-specific applications.

Incisional hernia repair with a slowly absorbable P4HB mesh: what happens after the mesh disappears? A retrospective longitudinal clinical study

PURPOSE

To analyze the incisional hernia recurrence rate at a long-term follow-up using a biosynthetic long-term absorbable mesh in patients with a higher risk of surgical infection in a contaminated surgical field.

METHODS

This was a retrospective multicentric study. All patients undergoing incisional hernia repair between 2016 and 2018 at 6 participating university centers were included. Patients were classified according to the Ventral Hernia Working Group (VHWG). All consecutive patients who underwent abdominal wall repair using biosynthetic long-term absorbable mesh (Phasix^®) in contaminated fields (grade 3 and 4 of the VHWG classification) were included. Patients were followed-up until September 2021. Preoperative, operative, and postoperative data were collected. All patients' surgical site infections (SSIs) and surgical site occurrences (SSOs) were recorded. The primary outcome of interest was the clinical incisional hernia recurrence rate.

RESULTS

One hundred and eight patients were included: 77 with VHWG grade 3 (71.3%) and 31 with VHWG grade 4 (28.7%). Median time follow-up was 41 months [24; 63]. Twenty-four patients had clinical recurrence during the follow-up (22.2%). The SSI and SSO rates were 24.1% and 36.1%, respectively. On multivariate analysis, risk factors for incisional hernia recurrence were previous recurrence, mesh location, and postoperative enterocutaneous fistula.

CONCLUSIONS

At the 3 year follow-up, the recurrence rate with a biosynthetic absorbable mesh (Phasix^®) for incisional hernia repair in high-risk patients (VHWG grade 3 and 4) seemed to be suitable (22.2%). Most complications occurred in the first year, and SSI and SSO rates were low despite high-risk VHWG grading.

3D-printed poly-4-hydroxybutyrate bioabsorbable scaffolds for nipple reconstruction

Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and loss of projection of the reconstructed nipple. The use of unprocessed costal cartilage (CC) as an internal support for the reconstructed nipple has not been widely adopted because of the excessively firm resultant construct. Herein we use a 3D-printed Poly-4-Hydroxybutyrate (P4HB) bioabsorbable scaffold filled with mechanically processed patient-derived CC to foster ingrowth of tissue in vivo to protect the regenerated tissue from contractile forces as it matures. After 6 months in vivo, newly formed spongy fibrovascular cartilaginous tissue was noted in processed CC filled 3D-printed scaffolds, which maintained significantly greater projection than reconstructions without scaffolds. Interestingly, 3D-printed P4HB scaffolds designed with an internal 3D lattice of P4HB filaments (without CC) displayed the fastest material absorption and vascularized adipose-fibrous tissue as demonstrated by SEM and histological analysis, respectively. Using 3D-printed P4HB scaffolds filled with either processed CC, a 3D P4HB lattice or no fills, we have engineered neo-nipples that maintain projection over time, while approximating the biomechanical properties of the native human nipple. We believe that this innovative 3D-printed P4HB nipple reconstruction scaffold will be readily translatable to the clinic. STATEMENT OF SIGNIFICANCE: Nearly all autologous tissue techniques and engineered tissue substitutes utilized for nipple reconstruction are hindered by scar contracture and substantial loss of projection of the reconstructed nipple, leading to significant patient dissatisfaction. Using 3D-printed P4HB scaffolds filled with either processed costal cartilage or 3D P4HB lattices, we have engineered neo-nipples that resist the forces induced by scar contracture, resulting in maintenance of neo-nipple projection over time and biomechanically approximating human nipples after 6 months in vivo implantation. This novel 3D-printed bioabsorbable P4HB scaffold will be readily translatable to the clinic to reconstruct nipples with patient-specific dimensions and long-lasting projection.

Antimicrobial Meshes for Hernia Repair: Current Progress and Perspectives

Recent advances in the development of biomaterials have given rise to new options for surgery. New-generation medical devices can control chemical breakdown and resorption, prevent post-operative adhesion, and stimulate tissue regeneration. For the fabrication of medical devices, numerous biomaterials can be employed, including non-degradable biomaterials (silicone, polypropylene, expanded polytetrafluoroethylene) or biodegradable polymers, including implants and three-dimensional scaffolds for tissue engineering, which require particular physicochemical and biological properties. Based on the combination of new generation technologies and cell-based therapies, the biocompatible and bioactive properties of some of these medical products can lead to progress in the repair of injured or harmed tissue and in tissue regeneration. An important aspect in the use of these prosthetic devices is the associated infection risk, due to the medical complications and socio-economic impact. This paper provides the latest achievements in the field of antimicrobial surgical meshes for hernia repair and discusses the perspectives in the development of these innovative biomaterials.

Self-adhesive hydrogel meshes reduce tissue incorporation and mechanical behavior versus microgrips self-fixation: a preclinical study

Purpose

Atraumatic mesh fixation for abdominal hernia repair has been developed to avoid the disadvantages of classical fixation with sutures, which is considered a cause of chronic pain and discomfort. This study was designed to analyze, in the short and medium term, the biological and mechanical behavior of two self-fixing meshes compared to that of a polypropylene (PP) mesh fixed with a cyanoacrylate (CA) tissue adhesive.

Methods

Partial abdominal wall defects (6 × 4 cm) were created in New Zealand rabbits (n = 36) and repaired using a self-adhesive hydrogel mesh (Adhesix™), a self-gripping mesh (ProGrip™) or a PP mesh fixed with CA (Surgipro™ CA). After 14 and 90 days, the host tissue incorporation, macrophage response and biomechanical strength were examined.

Results

At 14 and 90 days, the ProGrip and Surgipro CA meshes showed good host tissue incorporation; however, the Adhesix implants presented poor integration, seroma formation and a higher degree of shrinkage. The Adhesix hydrogel was completely reabsorbed at 14 days, whereas ProGrip microhooks were observed at all study times. The macrophage response was higher in the ProGrip and Surgipro CA groups at 14 and 90 days, respectively, and decreased over time. At 90 days, the ProGrip implants showed the highest tensile strength values and the Adhesix implants showed the highest failure stretch.

Conclusion

Meshes with mechanical microgrip self-fixation (ProGrip) show better biological and mechanical behavior than those with adhesive hydrogel (Adhesix) in a preclinical model of abdominal hernia repair in rabbits.

The Synthetic Scaffolds for Ventral Hernia Repair: Perspectives for Regenerative Surgery—Systematic Review

Ventral hernia (VH) frequently affects patients after abdominal surgery. The use of a mesh is often recommended. Different materials are described, from synthetic non-resorbable meshes to biological meshes. New generation meshes, also named scaffolds, aim to combine the advantages of both materials. The aim of this review is to provide an overview of the cytological, histological, biomechanical, and clinical outcomes of the use of the newest resorbable synthetic scaffolds in VH repair, based on experimental studies in a pre-clinical setting. A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and to the Assessing the Methodological Quality of Systematic Reviews (AMSTAR) guidelines. Only experimental studies were included. Outcome parameters were building technique, in vitro cytocompatibility, in vivo histocompatibility, biomechanical analysis, and clinical outcomes. The articles included were nine. The total number of cases treated was 257. Materials analyzed included electrospun silk fibroin (SF)/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) hybrid scaffolds, biodegradable polyester poly-ε-caprolactone (PCL) in the form of nanofibers, biodegradable mesh in poly-4-hydroxybutyrate (P4HB), nanofibrous polylactic acid (PLA) scaffold with a polypropylene (PP) material to generate a sandwich-like mesh, the collagen sponge (CS) group, the hybrid scaffold (HS) containing CS and poly-L-lactide (PLLA), and the hybrid scaffold (HS) + bone marrow (HSBM). Resorbable synthetic scaffolds are new, safe, surgical materials for the treatment or prevention of ventral hernia in animal models. Scaffolds should be tested in a contaminated surgical field for emergency use. Rigorous schematic indications for data collection are needed to improve the quality of the data in order to definitively clarify the pathway involved in inflammatory induced response.

Evaluation of the short-term host response and biomechanics of an absorbable poly-4-hydroxybutyrate scaffold in a sheep model following vaginal implantation

Objective

To evaluate the host‐ and biomechanical response to a fully absorbable poly‐4‐hydroxybutyrate (P4HB) scaffold in comparison with the response to polypropylene (PP) mesh.

Design

In vivo animal experiment.

Setting

KU Leuven Center for Surgical Technologies.

Population

Fourteen parous female Mule sheep.

Methods

P4HB scaffolds were surgically implanted in the posterior vaginal wall of sheep. The comparative PP mesh data were obtained from an identical study protocol performed previously.

Main outcome measures

Gross necropsy, host response and biomechanical evaluation of explants, and the in vivo P4HB scaffold degradation were evaluated at 60‐ and 180‐days post‐implantation. Data are reported as mean ± standard deviation (SD) or standard error of the mean (SEM).

Results

Gross necropsy revealed no implant‐related adverse events using P4HB scaffolds. The tensile stiffness of the P4HB explants increased at 180‐days (12.498 ± 2.66 N/mm SEM [p =0.019]) as compared to 60‐days (4.585 ± 1.57 N/mm) post‐implantation, while P4HB degraded gradually. P4HB scaffolds exhibited excellent tissue integration with dense connective tissue and a moderate initial host response. P4HB scaffolds induced a significantly higher M2/M1 ratio (1.70 ± 0.67 SD, score 0–4), as compared to PP mesh(0.99 ± 0.78 SD, score 0–4) at 180‐days.

Conclusions

P4HB scaffold facilitated a gradual load transfer to vaginal tissue over time. The fully absorbable P4HB scaffold, in comparison to PP mesh, has a favorable host response with comparable load‐bearing capacity. If these results are also observed at longer follow‐up in‐vivo, a clinical study using P4HB for vaginal POP surgery may be warranted to demonstrate efficacy.

Tweetable Abstract

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Degradable vaginal P4HB implant might be a solution for treatment of POP.

Botox, Abdominal Wall Transection, and Body Positioning: A Case of Complex Abdominal Wall Reconstruction With Seat Belt Syndrome

Seat belt syndrome (SBS) represents all injury profiles associated with seat belt injuries and motor vehicle crashes (MVCs). Seat belt syndrome classically presents with a superficial seat belt sign that may signify deeper intra-abdominal and/or spinal involvement. The amount of force transmitted from the restraint to the passenger ultimately dictates the amount and severity of the injury. We present a unique case of a 59-year-old female involved in a motor vehicle crash with multiple traumatic injuries, including seat belt syndrome, abdominal wall transection, and bowel injuries. She later had reconstruction of her traumatic abdominal wall hernias (TAWHs). Three unique approaches were used in the management of her traumatic abdominal wall hernias: (1) preoperative Botulinum toxin (Botox) injections, (2) operative use of biologic and bioabsorbable meshes in contaminated fields, and (3) postoperative physical therapy and body positioning. The patient did not experience any recurrence of these hernias after her abdominal wall reconstruction and remains alive at the time this case was written. The diagnostic criteria and surgical management of traumatic abdominal wall hernias have yet to be established, and the case presented here provides approaches that should serve as future areas for study.

Current Advances towards 4-Hydroxybutyrate Containing Polyhydroxyalkanoates Production for Biomedical Applications

Polyhydroxyalkanoates (PHA) are polyesters having high promise in biomedical applications. Among different types of PHA, poly-4-hydroxybutyrate (P4HB) is the only polymer that has received FDA approval for medical applications. However, most PHA producing microorganisms lack the ability to synthesize P4HB or PHA comprising 4-hydroxybutyrate (4HB) monomer due to their absence of a 4HB monomer supplying pathway. Thus, most microorganisms require supplementation of 4HB precursors to synthesize 4HB polymers. However, usage of 4HB precursors incurs additional production cost. Therefore, researchers have adopted strategies to reduce the cost, such as utilizing low-cost substrate as well as constructing 4HB monomer supplying pathways in microorganisms. We herein summarize the biomedical applications of P4HB, the natural producers of 4HB polymer, and the various strategies that have been applied in producing 4HB polymers in non-4HB producing microorganisms. It is expected that the readers would gain a vivid idea on the different strategic developments in the field of 4HB polymer production.

Slowly resorbable biosynthetic mesh: 2-year results in VHWG grade 3 hernia repair

Introduction

Information on the long-term performance of biosynthetic meshes is scarce. This study analyses the performance of biosynthetic mesh (Phasix™) over 24 months.

Methods

A prospective, international European multi-center trial is described. Adult patients with a Ventral Hernia Working Group (VHWG) grade 3 incisional hernia larger than 10 cm², scheduled for elective repair, were included. Biosynthetic mesh was placed in sublay position. Short-term outcomes included 3-month surgical site occurrences (SSO), and long-term outcomes comprised hernia recurrence, reoperation, and quality of life assessments until 24 months.

Results

Eighty-four patients were treated with biosynthetic mesh. Twenty-two patients (26.2%) developed 34 SSOs, of which 32 occurred within 3 months (primary endpoint). Eight patients (11.0%) developed a hernia recurrence. In 13 patients (15.5%), 14 reoperations took place, of which 6 were performed for hernia recurrence (42.9%), 3 for mesh infection (21.4%), and in 7 of which the mesh was explanted (50%). Compared to baseline, quality of life outcomes showed no significant difference after 24 months. Despite theoretical resorption, 10.7% of patients reported presence of mesh sensation in daily life 24 months after surgery.

Conclusion

After 2 years of follow-up, hernia repair with biosynthetic mesh shows manageable SSO rates and favorable recurrence rates in VHWG grade 3 patients. No statistically significant improvement in quality of life or reduction of pain was observed. Few patients report lasting presence of mesh sensation. Results of biosynthetic mesh after longer periods of follow-up on recurrences and remodeling will provide further valuable information to make clear recommendations.

Trial registration

Registered on clinicaltrials.gov (NCT02720042), March 25, 2016.

Laparoscopic Ventral Hernia Repair with Poly-4-Hydroxybutyrate Absorbable Barrier Composite Mesh

Background

Repair of ventral and incisional hernias (VIHR) is a common procedure, newly introduced resorbable mesh biomaterials provide an attractive option to reduce the use of permanent synthetic mesh in hernia surgery and reduce its complications. However, data on the use of slowly resorbable mesh materials remains scarce, this study aims to evaluate the use of poly-4-hydroxybutyrate/absorbable barrier composite mesh (P4HB/ABCM) in laparoscopic repair of VIHR.

Methods

This is a retrospective study of a sequential cohort of patients undergoing laparoscopic VIHR utilizing a P4HB/ABCM mesh. Perioperative characteristics and clinical outcomes were collected.

Results

In total, 26 patients including 10 females and 7 males underwent laparoscopic VIHR using P4HB/ABCM. All surgeries were performed in a single institution by the same surgeon. The average patient age was 52.6, and the mean BMI was 35.5. All patients had a clean wound classification. The average defect size was 136.4 cm². All patients were seen in clinic with a median follow-up of 28 months. We observed 4 wound seromas, and no wound infections or recurrences during the follow-up period.

Conclusion

Results of laparoscopic VIHR with P4HB/ABCM are favorable and encourages further studies on the role of absorbable biosynthetic mesh materials in hernia surgery.

Cost-effectiveness analysis of resorbable biosynthetic mesh in contaminated ventral hernia repair

BACKGROUND

The aim of this study was to compare, in terms of cost and serious complications, the use of biosynthetic resorbable parietal mesh with biologic mesh in patients undergoing contaminated ventral hernia repair (modified Ventral Hernia Working Group grade 3). Poly-4-hydroxy-butyrate (P4HB) biosynthetic mesh has rarely been the subject of comparative studies in the context of contamination. Data are required to confirm the effects of a transition from biological mesh to biosynthetic resorbable mesh.

PATIENTS AND METHODS

A cost-effectiveness analysis was conducted. It was based on a decision analysis model built with clinical and economic data issued from a before-after study that included 94 patients hospitalized for ventral hernia repair at the University Hospital of Strasbourg (France) from June 2011 to February 2018. The effectiveness endpoint was the number of patients presenting with a serious specific complication or a general complication at 6 months. Data for surgical hospitalization stays, home hospitalizations and ambulatory care costs were included.

RESULTS

We found fewer serious complications with biosynthetic mesh: 21% versus 33% with biologic mesh. A cost savings of US $5146 was determined. Deterministic sensitivity analyses and a probabilistic analysis confirmed our findings and the robustness of the model.

CONCLUSION

P4HB biosynthetic resorbable mesh appeared to be the most effective and the least costly option. Additional data will be needed to confirm the superiority of biosynthetic mesh in terms of the recurrence risk reduction over a longer period.

Polymer Hernia Repair Materials: Adapting to Patient Needs and Surgical Techniques

Biomaterials and their applications are perhaps among the most dynamic areas of research within the field of biomedicine. Any advance in this topic translates to an improved quality of life for recipient patients. One application of a biomaterial is the repair of an abdominal wall defect whether congenital or acquired. In the great majority of cases requiring surgery, the defect takes the form of a hernia. Over the past few years, biomaterials designed with this purpose in mind have been gradually evolving in parallel with new developments in the different surgical techniques. In consequence, the classic polymer prosthetic materials have been the starting point for structural modifications or new prototypes that have always strived to accommodate patients’ needs. This evolving process has pursued both improvements in the wound repair process depending on the implant interface in the host and in the material’s mechanical properties at the repair site. This last factor is important considering that this site—the abdominal wall—is a dynamic structure subjected to considerable mechanical demands. This review aims to provide a narrative overview of the different biomaterials that have been gradually introduced over the years, along with their modifications as new surgical techniques have unfolded.

Prosthetic meshes for hernia repair: State of art, classification, biomaterials, antimicrobial approaches, and fabrication methods

Worldwide, hernia repair represents one of the most frequent surgical procedures encompassing a global market valued at several billion dollars. This type of surgery usually requires the implantation of a mesh that needs the appropriate chemical, physical and biological properties for the type of repair. This review thus presents a description of the types of hernias, current hernia repair methods, and the state of the art of prosthetic meshes for hernia repair providing the most important meshes used in clinical practice by surgeons working in this area classified according to their biological or chemical nature, morphology and whether bioabsorbable or not. We emphasise the importance of surgical site infection in herniatology, how to deal with this microbial problem, and we go further into the future research lines on the production of advanced antimicrobial meshes to improve hernia repair and prevent microbial infections, including multidrug-resistant strains. A great deal of progress has been made in this biomedical field in the last decade. However, we are still far from an ideal antimicrobial mesh that can also provide excellent integration to the abdominal wall, mechanical performance, low visceral adhesion and minimal inflammatory or foreign body reactions, among many other problems.

Observational Cohort Study on the Use of a Slowly Fully Resorbable Synthetic Mesh (Phasix™) in the Treatment of Complex Abdominal Wall Pathology with Different Grades of Contamination

PURPOSE

Abdominal wall hernia repair in contaminated cases remains a therapeutic challenge due to the high risk of post-operative surgical site occurrences (SSO). Slowly resorbable synthetic (biosynthetic) meshes have recently been introduced and may offer unique advantages when challenged with bacterial colonization during abdominal wall reconstruction.

METHODS

A multicenter single-arm retrospective observational cohort study examined all consecutive patients in whom a poly-4-hydroxybutyrate mesh (Phasix™ or Phasix™ ST; Becton Dickinson, Franklin Lakes, NJ, USA) was used for the repair of an inguinal or ventral/incisional hernia, or to replace an infected synthetic mesh. Patient records were analyzed according to the level of contamination, using the classification score of the Centers for Disease Control and Prevention (CDC). The primary objective was to evaluate short-term postoperative morbidity by assessing SSOs and the need for reoperation or even mesh excision.

RESULTS

A total of 47 patients were included. The median age was 68 years (30-87), the male/female ratio was 26/21, and the median BMI was 26.5 kg/m2 (16.4-46.8). There were 17 clean cases, 17 clean-contaminated, 6 contaminated and 7 dirty. Median follow-up time was 48 days. An SSO was seen in 4 clean (23.5%), 7 clean-contaminated (41.2%), 2 contaminated (33.3%) and 5 dirty cases (71.4%). A surgical site occurrence requiring procedural intervention (SSOPI) was seen in 2 clean (11.8%), 3 clean-contaminated (17.6%), 1 contaminated (16.7%) and 2 dirty cases (28.6%). Hernia recurrence was seen in 1 clean (5.9%), 2 clean-contaminated (11.8%) and 3 dirty cases (42.9%). Mesh excision had to be performed in only one case in the contaminated group.

CONCLUSION

The Phasix™ mesh shows promising short-term results when used in contaminated hernia-related surgery. Even in contaminated or dirty conditions, with or without infection of the mesh, resection of the mesh only had to be performed once and patients could be managed either conservatively or by relatively minor reoperations. However, further research is needed to fully evaluate the safety and efficacy of these meshes.

Poly-4-Hydroxybutyric Acid Mesh Compares Favorably With Acellular Dermal Matrix in Tissue Expander-Based Breast Reconstruction

BACKGROUND

Acellular dermal matrix (ADM) is commonly used during immediate expander-based breast reconstruction, with potential advantages of greater intraoperative expansion, decreased time to complete expansion, and decreased rates of capsular contracture. However, ADM is associated with increased infection rate, seroma, and subsequent reconstructive failure. Poly-4-hydroxybutyric acid (P4HB) mesh is a large pore, biosynthetic scaffold shown to fully resorb and incorporate host tissues within 18 months. We sought to compare outcomes between the use of P4HB and ADM in immediate retropectoral expander-based reconstruction.

METHODS

One hundred ninety-two consecutive cases (107 patients) of breast reconstruction using ADM were compared with a subsequent cohort of 112 cases (62 patients) using P4HB mesh. In all patients, reconstruction was performed immediately after mastectomy by a single surgeon, and outcomes were compared between groups.

RESULTS

Baseline characteristics were similar between the P4HB and ADM groups. Overall infection rates were lower, but not significantly with P4HB (11% vs 17%, P = 0.18). Time to drain removal was significantly lower with P4HB (15 vs 18 days, P = 0.008), although there was no difference in rates of seroma (0.9% vs 3%, P = 0.43). Similar numbers of patients underwent external beam radiation (22% vs 24%) and received chemotherapy in each group (48% vs 45%). By univariate analysis, all odds ratios were decreased with use of P4HB, including risk of major complications (0.55), seroma (0.17), infection (0.59), need for reoperation (0.78), and skin necrosis (0.77).

CONCLUSIONS

Initial findings suggest P4HB mesh to be a safe alternative to ADM in expander-based breast reconstruction, with trends toward decreased rates of infection, seroma, and need for device removal using P4HB mesh. Although our results are limited to a small series of initial patients, P4HB mesh may be a promising novel technique to decrease complications inherent to use of ADM at a reduced material cost.

Robust Electrospun Nanofibers from Chemosynthetic Poly(4-hydroxybutyrate) as Artificial Dural Substitute

Bioresorbable poly(4-hydroxybutyrate) (P4HB) may fulfill the specific requirements that are necessary for a dural substitute, including its high elasticity, long-term strength retention properties, and the biocompatibility without significant accumulation of acidic degradation products. However, commercial P4HB can only be produced by the bacterial fermentation, which limits its applications in the cerebrospinal system due to higher endotoxin restriction. Meanwhile, P4HB can be prepared via the ring-opening polymerization of γ-butyrolactone. In this contribution, high molecular weight P4HB from chemosynthesis is electrospun into fibrous membrane, showing good mechanical properties that match the natural dura mater. Such P4HB membrane induces fast cellular migration, adhesion, and proliferation of fibroblasts in vitro. Subcutaneous implantation in rats demonstrates excellent biocompatibility of the P4HB membrane with proper biodegradation behaviors. After implantation in the rabbit dural defect model as an onlay graft, the P4HB membranes prevent cerebrospinal fluid leakage and regenerate dura tissue without detecting any local or systematic infections or foreign body responses. Thus, the electrospun P4HB membranes may be particularly useful as artificial dural substitutes to induce wound closure and tissue regeneration, which will be of great benefit to neurosurgery in the future.

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.

Bilateral transversus abdominis release: Complex hernia repair without sacrificing quality of life

BACKGROUND

Transversus Abdominis Release (TAR) during ventral hernia repair (VHR) allows for further lateral dissection by dividing the transversus abdominis muscles (TAM). The implications of division of the TAM on clinical and patient-reported outcomes has not be extensively studied.

METHODS

Adult patients undergoing retrorectus (RR) VHR with biosynthetic mesh with or without bilateral TAR were retrospectively identified. Post-operative and patient-reported outcomes (PROs) were collected.

RESULTS

Of 50 patients, 24 underwent TAR and 26 had RR repair alone. Median defect sizes were 449 cm² and 208 cm², respectively (p < 0.001). Rates of SSO and SSI were similar (p > 0.05). One TAR patient (4.2%) and four RR patients (15.4%) recurred (p = 0.26), with median follow up of 24 and 38 months. PROs improved significantly in both groups (p < 0.05).

CONCLUSION

Despite more complex abdominal wall reconstruction on larger defects, TAR has minimal major adverse events, low recurrence rates, and does not negatively affect PROs.

Successful conservative treatment of a poly-4-hydroxybutyrate mesh infection: A case report

Introduction and importance

An infection of an abdominal wall prosthesis can be a real disaster for the patient. A conservative treatment might be an option if biological or slowly resorbable synthetic meshes were used. However, adequate research of their use in contaminated and dirty wounds lacks.

Case presentation

Herein we report the case of a 69-year-old patient with a heavily infected poly-4-hydroxybutyrate mesh that was successfully treated conservatively.

Clinical discussion

Despite promising results of poly-4-hydroxybutyrate meshes, their use remains controversial and studies in contaminated wounds are scarce.

Conclusion

Our case report shows the potential benefits of a poly-4-hydroxybutyrate mesh in a very high-risk patient with active infection.

Behaviour at the peritoneal interface of next-generation prosthetic materials for hernia repair

BACKGROUND

When using a prosthetic material in hernia repair, the behaviour of the mesh at the peritoneal interface is especially important for implant success. Biomaterials developed for their intraperitoneal placement are known as composites and are made up of two different-structure materials, one is responsible for good integration within host tissue and the other is responsible to make contact with the viscera. This study examines the behaviour at the peritoneal level of two composites, the fully degradable Phasix-ST® and the partially degradable Symbotex®. A polypropylene mesh (Optilene®) served as control.

METHODS

Sequential laparoscopy from 3 to 90 days, in a preclinical model in the New Zealand white rabbit, allowed monitoring adhesion formation. Morphological studies were performed to analyse the neoperitoneum formed in the repair process. Total macrophages were identified by immunohistochemical labelling. To identify the different macrophage phenotypes, complementary DNAs were amplified by qRT-PCR using specific primers for M1 (TNF-α/CXCL9) and M2 (MRC1/IL-10) macrophages.

RESULTS

The percentage of firm and integrated adhesions remained very high in the control group over time. Both composites showed a significant decrease in adhesions at all study times and in qualitative terms were mainly loose. Significant differences were also observed from 7 days onwards between the two composites, increasing the values in Phasix over time. Neoperitoneum thickness for Phasix was significantly greater than those of the other meshes, showing mature and organized neoformed connective tissue. Immunohistochemically, a significantly higher percentage of macrophages was observed in Symbotex. mRNA expression levels for the M2 repair-type macrophages were highest for Phasix but significant differences only emerged for IL-10.

CONCLUSIONS

Fewer adhesions formed to the Symbotex than Phasix implants. Ninety days after implant, total macrophage counts were significantly higher for Symbotex, yet Phasix showed the greater expression of M2 markers related to the tissue repair process.

Slowly absorbable mesh in contaminated incisional hernia repair: results of a French multicenter study

PURPOSE

To analyze the postoperative morbidity and 1-year recurrence rate of incisional hernia repair using a biosynthetic long-term absorbable mesh in patients at higher risk of surgical infection in a contaminated surgical field.

METHODS

All patients undergoing incisional hernia repair in a contaminated surgical field with the use of a biosynthetic long-term absorbable mesh (Phasix®) between May 2016 and September 2018 at six participating university centers were included in this retrospective cohort and were followed-up until September 2019. Regarding the risk of surgical infection, patients were classified according to the modified Ventral Hernia Working Group classification. Preoperative, operative and postoperative data were collected. All patients' surgical site infections (SSIs) and occurrences (SSOs) and recurrence rates were the endpoints of the study.

RESULTS

Two hundred and fifteen patients were included: 170 with mVHWG grade 3 (79%) and 45 with mVHWG grade 2 (21%). The SSI and SSO rates at 12 months were 22.3% and 39.5%, respectively. According to the Dindo-Clavien classification, 43 patients (20.0%) had at least one minor complication, and 57 patients (26.5%) had at least one major complication. Among the 121 patients (56.3%) having at least 1 year of follow-up, the clinical recurrence rate was 12.4%. Multivariate analysis showed that a concomitant gastrointestinal procedure was an independent risk factor for surgical infection (OR = 2.61), and an emergency setting was an independent risk factor for major complications (OR = 11.9).

CONCLUSION

The use of a biosynthetic absorbable mesh (Phasix®) is safe in a contaminated surgical field, with satisfying immediate postoperative and 1-year results.

TRIAL REGISTRATION

The study is registered on Clinical Trial ID: NCT04132986.

What results can be expected one year after complex incisional hernia repair with biosynthetic mesh?

BACKGROUND

Incisional hernia is a frequent complication after midline laparotomy. The current standard repair includes the use of a synthetic mesh to prevent recurrence. However, the use of a synthetic mesh in a contaminated field carries a higher risk of mesh infection. In this setting biologic and biosynthetic meshes can be used as they resist to infection, but these are absorbable meshes. This raises the question of the risk of recurrence as the mesh disappears. Phasix® is a biosynthetic mesh getting absorbed in 12-18 months. The aim of this study was to assess the 1-year recurrence rate after abdominal-wall repair with a Phasix® mesh.

METHODS

All patients undergoing ventral hernia repair between 2016 and 2018 at the University Hospital of Dijon using a Phasix® mesh were prospectively included in a database. They were all followed-up with a physical exam and a routine CT scan at one year. All postoperative complications were recorded.

RESULTS

Twenty-nine patients were included in the study (55.2% women), with a mean BMI of 30,25 kg/m². Nineteen meshes were sublay and 10 intraperitoneal. Complications at 1 month were mainly mild: Clavien-Dindo I and II (61.1%). No mesh was explanted. There was no chronic infection. The mean length of stay was 11.5 days. The 1-year recurrence rate was 10.3%.

CONCLUSION

Patients having undergone complex ventral hernia repair with a Phasix® mesh have a 1-year recurrence rate of 10.3%. No severe surgical site occurrence was detected. A longer follow-up in a larger number of patients could confirm the place of this mesh in abdominal-wall repair.

A Novel Use of Fully Absorbable PhasixTM Mesh for Laparoscopic Inguinal Hernia Repair

Background and Objectives

An inguinal hernia is usually repaired with synthetic nonabsorbable mesh, resulting in collagen formation, chronic inflammation, and fibrosis, with significantly reduced hernia recurrence. However, chronic pain may affect the quality of life. Poly-4-hydroxybutyrate (P4HB) mesh was introduced to minimize complications, and starts to degrade in 12-18 months. This study assesses the consequences and results of patients undergoing transabdominal preperitoneal (TAPP) inguinal hernia repair using P4HB mesh (Phasix^TM, C.R. Bard Inc., Murray Hill, NJ, USA).

Methods

We performed a pilot study of laparoscopic TAPP repair for inguinal hernias using P4HB mesh in 15 patients (14 male and one female) with an average age of 55.8 y, and an average body mass index of 27.4 kg/m². We assessed the recurrence rate and patients' chronic pain for 30 months, with institutional review board approval (E-19-3735). The study was conducted from January 2016 to July 2017 in Medical City, King Saud University. We measured postoperative pain, reactions, mesh sensation, discomfort, and recurrence.

Results

In 15 patients, we encountered no recurrence or mesh sensation, except in one patient, who experienced mild chronic inguinal pain for one year, without activity restrictions.

Conclusion

Laparoscopic TAPP inguinal hernia repair using P4HB mesh is safe for combined, direct (medial), and indirect (lateral) inguinal hernia, with no recurrence. P4HB absorbable mesh caused less chronic pain and discomfort. Longer follow-up, more patients and 15 patients repaired using synthetic mesh are necessary to assess the utility of P4HB for inguinal hernia repair globally.

Prospective, multicenter study of P4HB (Phasix™) mesh for hernia repair in cohort at risk for complications: 3-Year follow-up

BACKGROUND

This study represents a prospective, multicenter, open-label study to assess the safety, performance, and outcomes of poly-4-hydroxybutyrate (P4HB, Phasix™) mesh for primary ventral, primary incisional, or multiply-recurrent hernia in subjects at risk for complications. This study reports 3-year clinical outcomes.

MATERIALS AND METHODS

P4HB mesh was implanted in 121 patients via retrorectus or onlay technique. Physical exam and/or quality of life surveys were completed at 1, 3, 6,12, 18, 24, and 36 months, with 5-year (60-month) follow-up ongoing.

RESULTS

A total of n = 121 patients were implanted with P4HB mesh (n = 75 (62%) female) with a mean age of 54.7 ± 12.0 years and mean BMI of 32.2 ± 4.5 kg/m2 (±standard deviation). Comorbidities included: obesity (78.5%), active smokers (23.1%), COPD (28.1%), diabetes mellitus (33.1%), immunosuppression (8.3%), coronary artery disease (21.5%), chronic corticosteroid use (5.0%), hypo-albuminemia (2.5%), advanced age (5.0%), and renal insufficiency (0.8%). Hernias were repaired via retrorectus (n = 45, 37.2% with myofascial release (MR) or n = 43, 35.5% without MR), onlay (n = 8, 6.6% with MR or n = 24, 19.8% without MR), or not reported (n = 1, 0.8%). 82 patients (67.8%) completed 36-month follow-up. 17 patients (17.9% ± 0.4%) experienced hernia recurrence at 3 years, with n = 9 in the retrorectus group and n = 8 in the onlay group. SSI (n = 11) occurred in 9.3% ± 0.03% of patients.

CONCLUSIONS

Long-term outcomes following ventral hernia repair with P4HB mesh demonstrate low recurrence rates at 3-year (36-month) postoperative time frame with no patients developing late mesh complications or requiring mesh removal. 5-year (60-month) follow-up is ongoing.

Outcomes of Poly-4-hydroxybutyrate Mesh in Ventral Hernia Repair: A Systematic Review and Pooled Analysis

Within the past decade, poly-4-hydroxybutyrate (P4HB) biosynthetic mesh has been introduced as a potential alternative to traditional biologic and synthetic mesh in ventral hernia repair (VHR). The aim of this study was to systematically assess clinical outcomes with the P4HB in VHR.

Methods

A literature search identified all articles published in 2000 involving the use of P4HB in VHR. Descriptive statistics were used to synthesize collective data points, including postoperative outcomes. A pooled analysis of postoperative outcomes was performed using chi-square test and Fisher exact test.

Results

Across 7 studies, the P4HB was used in 453 patients. The mean rate of surgical site infection (SSI) was 6.8% (31/453), reoperation 10.7% (30/281), and recurrence 9.1% (41/453). At an average follow-up of 26.8 months, the incidence of recurrence was 10.4% (28/270). Onlay was significantly associated with increased recurrence (14.2% versus 4.4%, P = 0.001). Among sublay placements, there was no difference in recurrence in clean (Center for Disease Control [CDC] 1) or contaminated (CDC >1) wounds (2.7% versus 6.1%, P = 0.585), but contaminated wounds were associated with increased SSI (2.7% versus 15.2%, P = 0.028). Ventral Hernia Working Group grade 2 and 3 did not have different incidences of recurrence (8.0% versus 5.1%, P = 0.526) nor SSI (5.1% versus 14.6%, P = 0.265).

Conclusions

Overall, clinical outcomes of the P4HB mesh in VHR are acceptable. The P4HB mesh serves as a reliable alternative to traditional synthetic and biologic mesh across a range of defect characteristics and patient health conditions. Further research is needed to better understand the conditions in which it may provide a clinical benefit over traditional mesh types.

In Vitro Bacterial Adhesion and Biofilm Formation on Fully Absorbable Poly-4-hydroxybutyrate and Nonabsorbable Polypropylene Pelvic Floor Implants

Knitted polypropylene (PP) implants for the correction of pelvic organ prolapse have been associated with complications such as vaginal exposure, infection, and pain. Since certain complications may be linked to bacterial contamination and persistent inflammation, there is a rationale to develop a biocompatible implant that is less prone to bacterial adhesion and biofilm formation. Delayed absorbable materials could meet these requirements and poly-4-hydroxybutyrate (P4HB) might be such a new material for future pelvic floor implants. We studied in vitro bacterial adhesion and biofilm formation on P4HB in comparison to PP. We investigated the influence of both polymers using flat films and compared P4HB and PP implants with different knitting designs. P4HB flat films were demonstrated to be hydrophilic with significantly less Staphylococcus aureus and Escherichia coli cultured from P4HB films than from hydrophobic PP films after 24 h of incubation. On the implants, a higher number of E. coli were cultured after 1 h of incubation from the knitted P4HB implant with the highest density and smallest pore size, compared to other P4HB and PP implants. No differences were observed between the implants for E. coli at later time points or for S. aureus incubation. These results show that in flat films, the polymer influences biofilm formation, demonstrated by a reduced biofilm formation on P4HB compared with PP flat films. In addition, the knitting design may affect bacterial adhesion. Despite certain design and material characteristics that give the knitted P4HB implants a higher surface area, this did not result in more bacterial adhesion and biofilm formation overall. Collectively, these results warrant further (pre)clinical investigations of P4HB pelvic floor implants.

In-vivo evaluation of a reinforced ovine biologic: a comparative study to available hernia mesh repair materials

PURPOSE

Two innovative reinforced biologic materials were studied in a non-human primate hernia repair model. The test articles, which combine layers of ovine decellularized extracellular matrix with minimal amounts of synthetic polymer, were evaluated for their biologic performance as measured by inflammatory response, healing kinetics, integration, and remodeling into functional host tissue. For comparison, seven clinically used biologic and synthetic meshes were also studied.

METHODS

Animals were implanted with test articles in surgically created full-thickness midline abdominal wall defects, and evaluated macroscopically and histologically at 4, 12, and 24 weeks.

RESULTS

Macroscopically, biologics resorbed and remodeled into naturally appearing tissue; the reinforced biologics appeared similar, but remodeled earlier and were less prone to stretch. Synthetics developed a layer of reactive tissue above and separate from the contracted mesh structure. At early time points, the collagen networks of biologics and reinforced biologics were infiltrated by host cells primarily as a peripheral layer on the biologics. As early as 12 weeks, the collagen networks associated with the reinforced biologics remodeled into organized host collagen. By 24 weeks, both reinforced biologics and biologics had low levels of inflammation. In contrast, a foreign body response persisted at 24 weeks with the synthetics, which had developed less organized collagen, separate in space from the actual mesh.

CONCLUSIONS

The current study shows a favorable response to reinforced biologics, which were associated with an initial inflammatory response, resolving by later time points, followed by active remodeling, and the formation of new morphologically functional collagen.