The effect of the type of intraperitoneally implanted prosthetic mesh on the systemic inflammatory response

Host inflammatory response to polypropylene implants: insights from a quantitative immunohistochemical and birefringence analysis in a rat subcutaneous model

Objectives

To describe acute and sub acute aspects of histological and immunohistochemical response to PP implant in a rat subcutaneous model based on objective methods.

Materials and Methods

Thirty rats had a PP mesh subcutaneously implanted and the same dissection on the other side of abdomen but without mesh (sham). The animals were euthanized after 4 and 30 days. Six slides were prepared using the tissue removed: one stained with hematoxylin-eosin (inflammation assessment); one unstained (birefringence evaluation) and four slides for immunohistochemical processing: IL-1 and TNF-α (pro-inflammatory cytokines), MMP-2 (collagen metabolism) and CD-31 (angiogenesis). The area of inflammation, the birefringence index, the area of immunoreactivity and the number of vessels were objectively measured.

Results

A larger area of inflammatory reaction was observed in PP compared to sham on the 4th and on the 30^th day (p=0.0002). After 4 days, PP presented higher TNF (p=0.0001) immunoreactivity than sham and no differences were observed in MMP-2 (p=0.06) and IL-1 (p=0.08). After 30 days, a reduction of IL-1 (p=0.010) and TNF (p=0.016) for PP and of IL-1 (p=0.010) for sham were observed. Moreover, area of MMP-2 immunoreactivity decreased over time for PP group (p=0.018). Birefringence index and vessel counting showed no differences between PP and sham (p=0.27 and p=0.58, respectively).

Conclusions

The implantation of monofilament and macroporous polypropylene in the subcutaneous of rats resulted in increased inflammatory activity and higher TNF production in the early post implant phase. After 30 days, PP has similar cytokines immunoreactivity, vessel density and extracellular matrix organization.

What do we know about titanized polypropylene meshes? An evidence-based review of the literature

PURPOSE

Despite the vast selection of brands available, nearly all synthetic meshes for hernia surgery continue to use one or other of three basic materials: polypropylene, polyester and ePTFE. These are used in combination with each other or with a range of additional materials such as titanium, omega 3, monocryl, PVDF and hyaluronate. This systematic review of all experimental and clinical studies is aimed at investigating whether titanized meshes confer advantages over other synthetic meshes in hernia surgery.

MATERIALS AND METHODS

A search of the medical literature from 2002 to 2012, as indexed by Medline, was performed, using the PubMed search engine (http://www.pubmed.gov). The search terms were: hernia mesh, titanium coating, lightweight mesh, TiMesh, mesh complications. All papers were graded according to the Oxford hierarchy of evidence.

RESULTS

Patients operated on with the Lichtenstein technique performed using the lightweight titanium-coated mesh have a shorter convalescence than those with the heavy-weight mesh Prolene. For inguinal hernias operated on with the TAPP technique and using a lightweight titanium-coated mesh in comparison to a heavy-weight Prolene mesh, the early postoperative convalescence seems to improve. Titanized meshes do exhibit a negative effect on sperm motility 1 year after a TEP operation, but not after 3 years. The laparoscopic IPOM technique with a titanium-coated polypropylene mesh was associated with less postoperative pain in the short term, lower analgesic consumption and a quicker return to everyday activities compared with the Parietex composite mesh.

CONCLUSION

In clinical studies, the titanium-coated polypropylene mesh shows in inguinal hernia repair certain benefits compared with the use of older heavy-weight meshes.

Nonwoven polypropylene prosthesis in large abdominal wall defects in rats

PURPOSE

To evaluate, in large abdominal wall defects surgically shaped in rats, if a synthetic polypropylene nonwoven prosthesis could be used as a therapeutic option to conventional polypropylene mesh.

METHODS

Twenty four (24) Wistar rats were enrolled into three groups. Group 1 (Simulation group) with an abdominal wall defect of 3 X 3 left untreated and Groups 2 and 3, respectively treated with a conventional polypropylene mesh and a polypropylene nonwoven (NWV) prosthesis to cover the breach. At the 45th postoperatively day, adhesion (area and strength) and vascularization of Groups 2 and 3 were evaluated. The histological preparations with Hematoxylin-Eosin, Tricromium of Masson, Pricrosirius red and polarization with birefringence, and also the structural analysis of the prostheses carried on by Thermogravimetry and Differential Scanning Calorimetry were also assessed.

RESULTS

There were no significant differences between the Groups 2 and 3.

CONCLUSION

In rats, the polypropylene nonwoven prosthesis showed to be safe and has to be considered as an alternative to conventional mesh manufactured by weaving in the treatment of great defects of the abdominal wall.

Experimental study comparing meshes made of polypropylene, polypropylene + polyglactin and polypropylene + titanium: inflammatory cytokines, histological changes and morphometric analysis of collagen

PURPOSE

Incisional hernia occurs in approximately 11% of all laparotomies. Changes in collagen have been closely implicated in its pathogenesis. The high recurrence rate (45-54%) after primary suture has stimulated the development of meshes. Currently, meshes are the biomaterials implant group most used in medicine. This study aims to compare the serum and tissue inflammatory responses and collagen deposition caused by meshes made of polypropylene, polypropylene + polyglactin and polypropylene + titanium.

METHODS

Thirty Wistar rats were divided into three groups. In group I, a high-density polypropylene mesh was positioned on the abdominal wall. In groups II and III, low-density meshes were used in associations with polyglactin and titanium, respectively. Immediately before the operation and on the first, third and fortieth postoperative days, pro-inflammatory cytokines were assayed. On the 40th postoperative day, the region of the inserted prosthesis was biopsied. The tissue inflammatory reaction was evaluated using a scale for objective scoring. For collagen, picrosirius was used with data reading using the Image Tool computer software.

RESULTS

Cytokines: there were no statistically significant differences between the groups.

HISTOLOGY

on the 40th postoperative day in group I, there were fewer inflammatory tissue response and greater collagen deposition (P < 0.01). In group II, there were greater inflammatory tissue response and less collagen deposition (P < 0.01). Group III presented intermediate values between groups I and II.

CONCLUSIONS

There were no significant differences in cytokine levels between the groups in the present study. In the animals with the polypropylene + polyglactin mesh implant there was the most intense inflammatory process with lower tissue maturation and collagen deposition on the 40th postoperative day. The polypropylene mesh presented a less severe late inflammatory process, with greater tissue maturation and collagen deposition. The polypropylene + titanium mesh presented intermediate values between the others.

Does type of mesh used have an impact on outcomes in laparoscopic inguinal hernia?

BACKGROUND

Theoretically, a lighter and softer mesh may decrease nerve entrapment and chronic pain by creating less fibrosis and mesh contracture in laparoscopic inguinal hernia repair.

METHODS

We performed a telephone survey of patients who underwent laparoscopic inguinal hernia surgery between 2001 and 2007. We recorded patient responses for chronic pain, foreign body sensation, recurrence, satisfaction, and return to work, and then studied the effect of type of mesh (polypropylene vs polyester) on these factors.

RESULTS

Of 109 consecutive patients surveyed (mean age, 54.5 y), 67 eligible patients underwent 84 transabdominal extraperitoneal procedures and 2 transabdominal preperitoneal procedures. Patients with polypropylene mesh had a 3 times higher rate of chronic pain (P = .05), feeling of lump (P = .02), and foreign body perception (P = .05) than the polyester mesh group. Our overall 1-year recurrence rate was 5.9%. The recurrence rate was 9.3% for the polypropylene group and 2.9% for the polyester group (P = .26).

CONCLUSIONS

A lightweight polyester mesh has better long-term outcomes for chronic pain and foreign body sensation compared with a heavy polypropylene mesh in laparoscopic inguinal hernia repair. We also saw a trend toward higher recurrence in the polypropylene group.

Prospective double-blind randomized controlled study comparing heavy- and lightweight polypropylene mesh in totally extraperitoneal repair of inguinal hernia: early results

BACKGROUND

Success of totally extraperitoneal (TEP) inguinal herniorrhaphy depends upon strengthening of the weakened native tissue by inflammation resulting in mesh-aponeurosis scar tissue (MAST) complex formation. The inflammatory response attributable to polypropylene (PP) content of the mesh is linked to weight of PP and pore size of the mesh. Continuation of the inflammatory process beyond MAST complex formation can entrap contiguous structures, leading to adverse outcome such as groin pain. Reduction of PP content has been shown to be beneficial in animal studies. Paucity of randomized controlled trials (RCTs) on human beings has left choice of mesh to surgeon preference or cost. We carried out a double-blind RCT comparing heavy- and lightweight PP-based meshes in TEP.

PATIENTS AND METHODS

Consecutive, married, sexually active male candidates for bilateral TEP herniorrhaphy were enrolled without any exclusion, with ethical and informed consent protocol. Standard TEP technique was followed for day-care surgery. Heavy- and lightweight meshes were implanted in each patient, one in either groin after randomization. Surgeon and patient were blinded to side of groin and type of mesh. An independent doctor (AID) evaluated the patients for groin pain, discomfort, sexual dysfunction, and clinical recurrence. A nonmedical secretary/AID transferred prospective data for both sides of groin collected by AID to Microsoft Excel.

RESULTS

Twenty-five bilateral TEPs implanting 25 heavy- and 25 lightweight PP meshes, one of each type in each patient, were performed from December 2005 to July 2007 without difficulty or complication. Lightweight PP mesh was associated with significantly better pain scores, patient comfort, and sexual function. There was no infection or recurrence with either type of mesh.

CONCLUSION

Lightweight PP mesh is associated with significantly better outcomes in TEP inguinal herniorrhaphy as compared with heavyweight PP mesh.