Critical view of robotic-assisted transverse abdominal release (r-TAR).

INTRODUCTION: Establishing straightforward and reproducible steps to describe the technique performed with the aid of the robotic system for complex hernia surgery is key for good outcomes. Even using the description of open surgery as a parameter for performing the robotic technique, it is important to stress the particularities of this access. To describe the steps to perform robotic-assisted TAR (r-TAR) in a standardized technique, with a critical and safe view of all the anatomical structures. DESCRIPTION OF THE TECHNIQUE: We defined 8 landmarks for the critical view of safety in r-TAR which include: (1) patient position, trocar and docking; (2) posterior rectus sheath mobilization; (3) transversus abdominis release (TAR)-Top-down technique; (4) transversus abdominis release (TAR)-bottom-up technique and mesh insertion; (5) contralateral trocar insertion and redocking, 6) posterior sheath closure; (7) final mesh positioning; and (8) anterior defect closure and drains. DISCUSSION: Complex hernia surgery using a robotic-assisted posterior component separation requires well-established steps so the procedure can be reproducible and achieve better results.

Assessment of myofascial medialization following posterior component separation via transversus abdominis muscle release in a cadaveric model.

PURPOSE: Posterior component separation (PCS) via the transversus abdominis release (TAR) procedure continues to gain popularity. However, neither the physiologic basis nor the extent of myofascial medialization after TAR is established. We aimed to assess both anterior and posterior rectus fascia (AF and PF) medialization following each step of the TAR procedure. METHODS: Ten fresh cadavers underwent PCS via TAR. Steps included midline laparotomy (MLL), retrorectus dissection (RRD), incision of the posterior rectus sheath (IPL), transversus abdominis muscle division (TAD), and retromuscular dissection (RMD). Medial advancement of AF and PF was measured following application of 2.5, 5.0 lb, and maximal tension to the fascial edge. Values are represented as mean advancement past midline in centimeters. RESULTS: MLL allowed advancement of 2.5, 3.7, and 4.9 cm. RRD provided advancement of 4.1, 5.9, and 7.6 cm for AF and 4.4, 6.2, and 7.5 cm for PF. IPL provided advancement of 4.2, 6.1, and 8.0 cm for AF and 4.6, 6.6, and 8.3 cm for PF. TAD provided advancement of 4.5, 6.6, and 8.6 cm for AF and 5.3, 7.5, and 9.5 cm for PF. RMD provided advancement of 5.5, 7.9, and 9.9 cm for AF and 6.9, 9.6, and 11.2 cm for PF. Overall, the complete TAR procedure provided AF advancement of 102% and PF advancement of 129%, over baseline. CONCLUSIONS: The TAR procedure provides for substantial medial advancement of both anterior and posterior myofascial components of the abdominal wall. Retromuscular dissection deep to the divided transversus abdominis muscle appears to be the key step of the procedure, allowing for effective reconstruction of very wide (≈ 20 cm) defects.

Outcomes of utilizing absorbable mesh as an adjunct to posterior sheath closure during complex posterior component separation.

BACKGROUND: A minority of patients undergoing posterior component separation (PCS) have abdominal wall defects that preclude complete reconstruction of the visceral sac with native tissue. The use of absorbable mesh bridges (AMB) to span such defects has not been established. We hypothesized that AMB use during posterior sheath closure of PCS is safe and provides favorable outcomes. METHODS: We performed a retrospective review of consecutive patients undergoing PCS with AMB at two hernia centers. Main outcome measures included demographics, comorbidities, and post-operative complications. RESULTS: 36 patients were identified. Post-operative wound complications included five surgical site infections. At a median of 27 months, there were five recurrent hernias (13.9%), 2 of which were parastomal, but no episodes of intestinal obstruction/fistula. CONCLUSIONS: Utilization of AMB for large posterior layer deficits results in acceptable rates of perioperative wound morbidity, effective PCS repairs, and does not increase intestinal morbidity or fistula formation.

Laparoscopic repair of traumatic flank hernias.

INTRODUCTION: Traumatic flank hernias (TFH) are caused by a blunt abdominal trauma with resultant detachment of the oblique musculofascial complex at the iliac crest and/or costal margin. Given such proximity to the bony structures and essential absence of healthy fascia to anchor the mesh, TFH represent a challenging surgical problem. Although laparoscopic repair of ventral hernias has become very common, no series of laparoscopic repairs of TFH has been reported to date. We present a series of patients undergoing laparoscopic repair of TFH. METHODS: After retrospective review of prospective hernia database at two Hernia centers, patients undergoing laparoscopic TFH repair were identified and analyzed. Main outcome measures included patient demographics, surgical technique, intraoperative data, and post-operative outcomes. RESULTS: From December 2007 to December 2013, 14 patients underwent laparoscopic repair of a TFH. Eleven patients had chronically incarcerated viscera within the defect. Operative steps included complete reduction of the hernia sac, pre/retroperitoneal dissection to expose the entire lateral edge of a psoas muscle, defect closure with transabdominal sutures, wide mesh overlap, and transabdominal suture fixation with selective use of bone anchors. The mean operative time was 174 min (range 125-230). Mean estimated blood loss was 65 cc. Mean mesh size was 295 cm2. There were no peri-operative complications. Mean hospital stay was 3.1 days and all patients returned to full activities by 6 weeks. At a mean follow-up of 35 months, there have been no recurrences. CONCLUSION: Laparoscopic approach to TFH is feasible and safe. It is associated with minimal hospital stay and fast functional recovery. The key components of our approach include wide pre/retroperitoneal with defect closure and subsequent wide mesh underlay coverage with fixation to bony structures using anchors/screws. We believe that the laparoscopic approach should safely considered for the majority of patients with TFH.

The use of Vicryl mesh in a porcine model to assess its safety as an adjunct to posterior fascial closure during retromuscular mesh placement.

BACKGROUND: Posterior component separation has become a common approach to complex abdominal wall reconstructions. This technique includes creation of an extraperitoneal retromuscular space for subsequent large synthetic mesh reinforcement. In certain cases, when complete restoration of "posterior" layer is precluded by significant tissue loss/damage, one proposed strategy is to replace the posterior fascia with an absorbable synthetic polyglactin (Vicryl) mesh. However, the safety of this strategy to prevent mesh-related visceral complication is unknown. Herein, we aimed to characterize mesh-viscera adhesion profiles and host tissue response of synthetic mesh either exposed directly to the viscera, or protected with Vicryl mesh. METHODS: Using adult Yorkshire pigs, 5 × 5 cm pieces of mesh were secured to the intact peritoneum in each of the four quadrants (n = 6 pigs, 24 mesh samples). The study groups were Vicryl (V), Marlex (M), Softmesh (S), Marlex + Vicryl construct (MV), Softmesh + Vicryl construct (SV). The self-made composite meshes were then implanted with the Vicryl side facing the exposed viscera. The pigs were survived for 60 days. At necropsy, grossly, the extent and tenacity of visceral adhesions were evaluated using established scales. Histologically, all specimens for fibrous encapsulation on the visceral surface of the mesh were reviewed by an experienced pathologist blind to meshes used. RESULTS: At necropsy, all Vicryl meshes were completely resorbed. The mean adhesion and tenacity scores for M and MV were 1.8 and 1.1 (P > 0.05), 2.0 and 1.5 (P > 0.05), respectively; while the mean adhesion extent scores and tenacity scores for S and SV were 2.0 and 1.2 (P > 0.05), 2.0 and 1.7 (P > 0.05). No significant difference in adhesion extent and tenacity was observed between Synthetic and Vicryl composite mesh groups. Histologically, Marlex + Vicryl mesh and Softmesh + Vicryl mesh constructs had thicker fibrous capsules than the corresponding unprotected Marlex and Soft mesh implants. Furthermore, visceral adhesions in the composite groups were noted to be to the fibrous capsule and not synthetic mesh itself. CONCLUSION: Utilization of the absorbable polyglactin (Vicryl) mesh as a separating layer between a synthetic mesh and intestines, did not reduce adhesions across various mesh types and composites. Histologically, however, a thick fibrous capsule replaced the Vicryl mesh and may be an important layer to prevent intestinal erosion into retromuscular synthetic meshes.

Repair of massive ventral hernias with "quilted" mesh.

INTRODUCTION: Prosthetic reinforcement is a critical component of hernia repair. For massive defects, mesh overlap is often limited by the dimensions of commercially available implants. In scenarios where larger mesh prosthetics are required for adequate reinforcement, it may be necessary to join several pieces of mesh together using non-absorbable suture. Here, we report our outcomes for abdominal wall reconstructions in which "quilted" mesh was utilized for fascial reinforcement. METHODS: Patients undergoing open incisional hernia repair utilizing posterior component separation and transversus abdominis muscle release, with use of quilted synthetic mesh placed in the retromuscular position, were reviewed. Main outcome measures included patient, hernia, and operative characteristics and post-operative outcomes, including surgical site occurrence (SSO), surgical site infection (SSI), and recurrence. RESULTS: Thirty-two patients (mean age 55.7 ± 9.3, BMI 38.3 ± 5.8 kg/m(2)) underwent open ventral hernia repair with "quilted" mesh placed in the retromuscular position. The mean defect area was 760.1 ± 311.0 cm(2) with a mean width of 24.7 ± 6.4 cm. Quilted meshes consisted of two-piece (69 %), three-piece (19 %) and four-piece (12 %) configurations. Wound morbidity consisted of eight (25 %) SSOs, including four (13 %) SSIs, all of which resolved without mesh excision. With mean follow-up of 9.0 ± 13.6 months, there were two (6.3 %) lateral recurrences, both unassociated with mesh-to-mesh suture line failure. CONCLUSIONS: Massive ventral hernias that require giant mesh prosthetics, currently not commercially available, may be successfully repaired using multiple mesh pieces sewn together in a quilt-like fashion. Such retromuscular repairs are durable, without added morbidity due to the mesh-to-mesh suture line. However, additional operative time is required for quilting the mesh together, prompting strong calls for manufacturing of larger mesh prosthetics.

Posterior component separation with transversus abdominis release successfully addresses recurrent ventral hernias following anterior component separation.

PURPOSE: Anterior component separation (ACS) with external oblique release for ventral hernia repair has a recurrence rate up to 32%. Hernia recurrence after prior ACS represents a complex surgical challenge. In this context, we report our experience utilizing posterior component separation with transversus abdominis muscle release (PCS/TAR) and retromuscular mesh reinforcement. METHODS: Patients with a history of recurrent hernia following ACS repaired with PCS/TAR were retrospectively identified from prospective databases collected at two large academic institutions. Patient demographics, hernia characteristics (using CT scan) and outcomes were evaluated. RESULTS: Twenty-nine patients with a history of ACS developed 22 (76%) midline, 3 (10%) lateral and 4 (14%) concomitant recurrences. Contamination was present in 11 (38%) of cases. All were repaired utilizing a PCS/TAR with retromuscular mesh placement (83% synthetic, 17% biologic) and fascial closure. Wound morbidity consisted of 13 (45%) surgical site occurrences including 8 (28%) surgical site infections. Five (17%) patients required 90-day readmission, and two (7%) were related to wound morbidity. One organ space infection with frank spillage of stool resulted in the only instance of mesh excision. This case also represents the only instance of recurrence (3%) with a mean follow-up of 11 (range 3-36) months. CONCLUSION: Patients with a history of an ACS who develop a recurrence represent a challenging clinical scenario with limited options for surgical repair. A PCS/TAR hernia repair achieves acceptable outcomes and may in fact be the best approach available.

Central failures of lightweight monofilament polyester mesh causing hernia recurrence: a cautionary note.

INTRODUCTION: Uncoated, lightweight, macroporous,monofilament mesh has been shown to demonstrate improved bacterial clearance, better tissue integration,reduced foreign body response, and less chronic pain with equivalent durability for hernia repair. These findings led us to use a new lightweight monofilament polyester mesh (Parietex TCM, Covidien). Here, we report our experience with this mesh in open incisional hernia repair. METHODS: Patients undergoing incisional hernia repair with Parietex TCM were retrospectively identified within our prospectively maintained database. Patient demographics,operative characteristics, and follow-up were reviewed. Outcome parameters included 90-day wound morbidity and hernia recurrence. RESULTS: In 2011, 36 patients (mean age 56.8; mean BMI32.4 kg/m2) underwent open incisional hernia repair with retrorectus mesh placement by two surgeons (MJR, YWN) at Case Medical Center. Anterior and posterior fascial closure was achieved in all cases. Wound morbidity included seven surgical site occurrences: four superficial infections that resolved with antibiotics, one wound dehiscence requiring wet-to-dry packing, and two seromas that resolved without intervention. With a mean follow-up of 13 months, 8 (22%) recurrences have occurred. On reoperation, 7 (19%) of these patients had mechanical failure or fracturing of the mesh. No confounding variables were identified by univariate analysis of patient demographics,operative characteristics, or wound morbidity. CONCLUSION: Lightweight monofilament polyester mesh (Parietex TCM) appears to have a high incidence of mechanical failure in the context of open incisional hernia repair. While this limitation may ultimately be revealed asa weakness of all lightweight mesh, surgeons should be aware that these failures have already been documented.

The effects of Losartan on abdominal wall fascial healing.

PURPOSE: Losartan, a commonly used angiotensin II receptor blocker (ARB) for blood pressure control, also impairs cutaneous wound healing. Our current study will analyze how Losartan affects wound healing in the muscle and fascia from both biomechanical and histological aspects. METHODS: A total of 26 Sprague-Dawley rats were separated into one control group (NS, N = 13) and one experimental group (LG, N = 13) to receive normal saline and 40 mg/kg of Losartan by way of gastric lavage, respectively. 7 days later, all animals were subjected to a 5 cm midline laparotomy. The fascia and skin were then closed with 4-0 prolene and 5-0 vicryl. 15 days postoperatively, the animals were sacrificed and the abdominal wall harvested for wound tensiometric test and histological analysis. RESULTS: All 26 rats survived to the time of necropsy. Tensiometry detected significantly higher wound tensile strength in the NS group (1.6 ± 0.31 N/mm) than in the LG (1.3 ± 0.28 N/mm) group (p = 0.016). Transection histology with trichrome staining demonstrated higher degree of immature fibroplasia inside the wound in the LG group than in the NS group (p = <0.0001). The LG group also had larger incisional gaps than the NG group. CONCLUSION: The antihypertensive drug, Losartan, retards wound healing in the abdominal fascia and reduces wound tensile strength in our rat model. Attention should be paid to the potential effects of various medications on fascial wound healing to guarantee optimal surgical outcomes.

The impact of developing a comprehensive hernia center on the referral patterns and complexity of hernia care.

BACKGROUND: Complex hernia repairs represent a formidable surgical challenge. Several comprehensive hernia centers, including ours, with advanced expertise have recently emerged across the country. However, the effects of tertiary specialization remain largely unclear. We aimed to evaluate the impact of developing a comprehensive hernia center on the referral patterns and costs of patients with complex hernias. METHODS: A prospectively maintained database was used to identify all patients undergoing open ventral hernia repair (VHR) between 2006 and 2013 at the Case Comprehensive Hernia Center. Patients were separated into two groups by zip code: those traveling either <25 or >100 miles. Demographics, operative characteristics, length of stay and costs data were analyzed. RESULTS: Of all patients who underwent open VHR during the study period, 287 met the inclusion criteria. Hernia length, width and area were all significantly larger for patients traveling >100 miles (P < 0.01 for all). These patients were also more likely to have active mesh infections (OR 3.57) and non-healing wounds (OR 5.00) when compared with local patients. Length of hospital stay was significantly longer for patients traveling >100 miles compared to those traveling <25 miles (9.7 vs. 6.8; P < 0.0001). Surgical site occurrence, infection and hernia recurrence rates were similar between the two groups during the follow-up period. Patients who traveled >100 miles incurred significantly higher fixed direct and variable direct costs compared to those who traveled <25 miles (P < 0.05 for both). CONCLUSION: The development of a comprehensive hernia center results in centralization of complex hernia care. Patients traveling >100 miles for ventral hernia repair have significantly larger and more complex hernias. The implications for improved patient outcomes and potential reimbursement issues for providing this care should be carefully evaluated.

History of methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection may not be a contraindication to ventral hernia repair with synthetic mesh: a preliminary report.

PURPOSE: A history of methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection presents a significant surgical dilemma as to the risk of subsequent mesh infection, even if no active infection is present. We investigated the outcomes of ventral hernia repair with synthetic mesh in patients with prior MRSA surgical site infections (SSIs). METHODS: All patients with a clean wound but prior MRSA SSI undergoing open ventral hernia repair with mesh by a single surgeon over a 3-year period were reviewed for the development of any major (need for readmission, operative debridement, or mesh removal) or minor SSI. All patients received peri-operative intravenous vancomycin and prolonged suppressive oral trimethoprim/sulfamethoxazole or doxycycline. RESULTS: Ten patients (male = 7, female = 3) with clean wounds and a history of MRSA SSI underwent open ventral hernia repair with retrorectus synthetic mesh placement. Mean follow-up was 13.5 ± 3.3 months. Overall, two patients (20 %) developed SSIs (minor = 2, major = 0). Both SSIs were successfully managed with therapeutic oral antibiotics and local wound care without need for surgical debridement or mesh removal. There have been no hernia recurrences in any of the patients. CONCLUSIONS: Preliminary results suggest that history of MRSA infection may not be a contraindication to the use of synthetic mesh for ventral hernia repair. Macroporous lightweight meshes, combined with use of prolonged suppressive antibiotics and sublay retromuscular mesh placement that provides complete tissue coverage, should be further investigated as an acceptable prosthetic choice when planning a complex ventral hernia repair in the setting of prior MRSA SSI.

Comparative analysis of histopathologic responses to implanted porcine biologic meshes.

OBJECTIVES: Biologic mesh (BM) prostheses are increasingly utilized for hernia repairs. Modern BMs are not only derived from different tissue sources, but also undergo various proprietary processing steps-factors that likely impact host tissue responses and mesh performance. We aimed to compare histopathologic responses to various BMs after implantation in a mouse model. MATERIALS AND METHODS: Five-mm samples of non-crosslinked [Strattice (ST)], and intentionally crosslinked [CollaMend (CM), Permacol (PC)] porcine-derived biologic meshes were implanted subcutaneously in C57BL/6 mice. 1, 4, 8, and 12 weeks post-implantation, meshes were assessed for inflammation, foreign body reaction (FBR), neocellularization, and collagen deposition using H&E and trichrome stains. RESULTS: All meshes induced early polymorphonuclear cell infiltration (highest in CM; lowest in ST) that resolved by 4 weeks. ST was associated with extensive macrophage presence at 12 weeks. Foreign body response was not seen in the ST group, but was present abundantly in the CM and PC groups, highest at 8 weeks. New peripheral collagen deposition was seen only in the ST group at 12 weeks. Collagen organization was highest in the ST group as well. Both CM and PC groups were associated with fibrous encapsulation and no evidence of integration or remodeling. CONCLUSIONS: Inflammation appears to be a common component of integration of all biologic meshes studied. Pronounced inflammatory responses as well as profound FBR likely lead to observed encapsulation and poor host integration of the crosslinked BMs. Overall, ST was associated with the lowest foreign body response and the highest degree of new collagen deposition and organization. These features may be key predictors for improved mesh performance during hernia repair.

Effect of patient and hospital characteristics on outcomes of elective ventral hernia repair in the United States.

PURPOSES: Our ability to predict complications of ventral hernia repairs (VHR) are inadequate. Although impact of patient comorbidities and hospital characteristics on outcomes of several surgical procedures has been reported, such analysis on elective herniorrhaphy has not been performed to date. We hypothesized that obesity and diabetes as well as socioeconomic factors would have deleterious outcomes on elective VHR. METHODS: Analysis of 2004-2008 Nationwide Inpatient Sample database. Main outcome measures included wound/systemic morbidity, length of stay, discharge status, and in-hospital mortality. Bivariate and multivariate analyses were performed to assess influence of diabetes, obesity, patient socioeconomic factors, and hospital characteristics on the outcomes of VHR. RESULTS: A total of 78,348 adults undergoing elective VHR were analyzed. Obesity had significant risks for cardiopulmonary complications and prolonged hospitalization. Diabetics were more likely to have delayed wound healing. Hispanic patients had significantly higher rates of pulmonary complications and mortality. As compared to private insurance patients, Medicaid and Medicare patients had significantly higher odds of complications, prolonged hospitalization, non-routine discharge, and mortality. CONCLUSION: Obesity and diabetes appear to be significant predictors of morbidity in patients undergoing elective VHR. Alarmingly, Medicare/Medicaid patients not only had the highest rates of wound/systemic complications but also the highest post-operative mortality. For the first time, we demonstrated that in addition to comorbidities, both patient socioeconomic factors and hospital characteristics appear to be major determinants of post-herniorrhaphy complications and mortalities. Improved health maintenance and reduction in income-related disparities in health care delivery may be paramount in improving outcomes of VHR in the United States.

Laparoscopic diagnosis and management of a novel inguino-pelvic hernia.

Inguinal hernias can typically be diagnosed with a proper history and thorough physical exam. However, patients with chronic groin pain, normal physical exam and no radiologic findings present a diagnostic/therapeutic dilemma [1]. We present a case of a female patient with obscure chronic groin pain. Upon laparoscopic exploration, she was found to have a hernia in a previously non-described location. Reduction of a chronically incarcerated preperitoneal fat and subsequent repair using traditional transabdominal preperitoneal repair resulted in a complete resolution of her pain.

Anisotropic evaluation of synthetic surgical meshes.

INTRODUCTION: The material properties of meshes used in hernia repair contribute to the overall mechanical behavior of the repair. The anisotropic potential of synthetic meshes, representing a difference in material properties (e.g., elasticity) in different material axes, is not well defined to date. Haphazard orientation of anisotropic mesh material can contribute to inconsistent surgical outcomes. We aimed to characterize and compare anisotropic properties of commonly used synthetic meshes. METHODS: Six different polypropylene (Trelex(®), ProLite™, Ultrapro™), polyester (Parietex™), and PTFE-based (Dualmesh(®), Infinit) synthetic meshes were selected. Longitudinal and transverse axes were defined for each mesh, and samples were cut in each axis orientation. Samples underwent uniaxial tensile testing, from which the elastic modulus (E) in each axis was determined. The degree of anisotropy (λ) was calculated as a logarithmic expression of the ratio between the elastic modulus in each axis. RESULTS: Five of six meshes displayed significant anisotropic behavior. Ultrapro™ and Infinit exhibited approximately 12- and 20-fold differences between perpendicular axes, respectively. Trelex(®), ProLite™, and Parietex™ were 2.3-2.4 times. Dualmesh(®) was the least anisotropic mesh, without marked difference between the axes. CONCLUSION: Anisotropy of synthetic meshes has been underappreciated. In this study, we found striking differences between elastic properties of perpendicular axes for most commonly used synthetic meshes. Indiscriminate orientation of anisotropic mesh may adversely affect hernia repairs. Proper labeling of all implants by manufacturers should be mandatory. Understanding the specific anisotropic behavior of synthetic meshes should allow surgeons to employ rational implant orientation to maximize outcomes of hernia repair.

Effects of mast cell modulation on early host response to implanted synthetic meshes.

INTRODUCTION: Mast cells (MCs) and their products (e.g., histamine, serotonin, heparin, prostaglandins, cytokines, etc.) play key roles in controlling local inflammation, wound healing, and foreign body reactions in vivo. Investigation of the role of MCs in mediating local tissue responses to synthetic hernia meshes has been very limited to date. We aimed to determine the effects of MCs/MC products in mice undergoing synthetic mesh implantation. MATERIALS AND METHODS: Circular samples (5 mm) of heavyweight microporous polypropylene (Trelex), midweight microporous polypropylene (ProLite), lightweight macroporous polypropylene with poliglecaprone (Ultrapro), and 3-dimensional macroporous polyester (Parietex) meshes were implanted subcutaneously in C57BL/6 J mice with and without cromolyn (MC stabilizer/suppressant) treatment (50 mg/kg, daily IP). Two weeks post-implantation, all meshes were explanted and evaluated histologically using H&E and trichrome stains. RESULTS: Chronic inflammation was focused around individual mesh fibers; inter-fiber inflammation and fibrosis diminished as mesh porosity increased. MC accumulation was seen at the periphery of inflammatory reactions, and in association with mesh-induced fibrosis and neovascularization. Cromolyn treatment resulted in significantly decreased fibrotic responses to all four meshes and reduced inflammation induced by Trelex, ProLite, and Parietex meshes but not Ultrapro. CONCLUSION: We demonstrated that MCs play important roles in mesh-induced host tissue reactions. Blocking MC degranulation decreased early inflammation and fibrosis induced by most synthetic meshes in this study. Further evaluation and understanding of the role of MCs in mesh-induced tissue reactions will provide new therapeutic approaches to enhance the biocompatibility of surgical meshes and ultimately improve clinical outcomes in patients undergoing hernia repair with synthetic biomaterials.

Activation of human mononuclear cells by porcine biologic meshes in vitro.

INTRODUCTION: While porcine-based biologic meshes are increasingly used for hernia repair, little data exist on tissue responses to such products. Host foreign body reaction, local inflammation, and wound healing are principally controlled by monocytes/macrophages (M/MØs). Exaggerated activation of M/MØs may deleteriously influence mesh integration and remodeling. We hypothesized that common porcine meshes induce the differential activation of M/MØs in vitro. MATERIALS AND METHODS: Samples of four acellular porcine-derived meshes, CollaMend (CM; C.R. Bard/Davol), Permacol (PC; TSL/Covidien), Strattice (ST; LifeCell), and Surgisis (SS; Cook Biotech), were exposed to mononuclear cells derived from the peripheral blood of six healthy subjects. Following a 7-day incubation period, supernatants were assayed for interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8), and vascular endothelial growth factor (VEGF) using a multiplex bead-based immunoassay system. The four groups were compared using analysis of variance (ANOVA) and Student's t-test. RESULTS: Each mesh type induced differential mononuclear cell activation in vitro. The mean IL-1beta expressions for CM (7,195 pg/ml) and PC (4,215 pg/ml) were significantly higher compared to ST and SS (123 and 998 pg/ml, respectively; P < 0.05). Similar trends were also seen for IL-6 (range 445-70,729 pg/ml), IL-8 (range 11,640-1,045,938 pg/ml), and VEGF (range 686-7,133 pg/ml). CONCLUSION: For the first time, we demonstrated that porcine meshes induce M/MØ activation in vitro. CM and PC (chemically crosslinked dermis) induced significantly higher cytokine expression compared to ST (non-crosslinked dermis) and SS (small intestine submucosa). These differences are likely related to proprietary processing methods and/or the extent of collagen crosslinking. Further understanding of immunologic effects of porcine-derived biologic meshes will not only allow for a comparison between existing products, but it may also lead to mesh modifications and improvement of their clinical performance.