The Use of Synthetic Mesh in Contaminated and Infected Abdominal Wall Repairs. A Long-term Prospective Clinical Trial
Condition: Abdominal Wall Defect; Abdominal Wall Infection; Abdominal Wall Fistula; Infection
MeSH terms: Infections; Communicable Diseases; Fistula
Study type: Interventional

Summary: 
      Background: Abdominal wall reconstruction in patients presenting with enteric fistulas and
      mesh infection is challenging. There is a consensus that synthetic mesh must be avoided in
      infected operations. The alternatives to using synthetic mesh, such as component separation
      techniques and biologic mesh, present disappointing results with expressive wound infection
      and hernia recurrence rates.

      Methods: A prospective clinical trial designed to evaluate the short and the long-term
      outcomes of patients submitted to elective abdominal wall repair with synthetic mesh in the
      dirty-infected setting, and compared to a cohort of patients submitted to clean ventral
      hernia repairs.
    

Detailed description: 
      We designed a prospective study, evaluating the short and the long-term outcomes of the
      surgical treatment of 40 consecutive patients presenting with an infected abdominal wall,
      compared to a cohort of 40 patients submitted to clean ventral hernia repairs. Patients were
      admitted between January 2012 and February 2015, and operated at the Hospital das Clinicas of
      the University of São Paulo School of Medicine, in Brazil. All patients included in the study
      group carried an active chronic mesh infection (mesh sinus, exposed mesh or mesh related
      enteric fistulas) resulting from a previous hernia repair, with or without an associated
      recurrent ventral hernia. All the operations required in this group were classified as Class
      IV (dirty-infected), accordingly to the CDC Wound Classifications, as adopted by the European
      registry for abdominal wall hernias. The only inclusion criterion was the presence of an
      active chronic mesh infection. The infected abdominal wall (IM) group and the outcomes of the
      treatment were compared to a clean-control (CC) group of patients who underwent clean
      abdominal wall reconstructions, originally belonging to a prospective study of the
      tensiometry of the abdominal wall, and operated during the same period and in the same
      conditions. The exclusion criteria were: giant ventral hernias with a volume ratio higher
      than 25%, patients on immunosuppressive therapy or using corticosteroids, patients with
      hepatic cirrhosis and portal hypertension, Chron´s disease, acute postoperative mesh
      infection, chronic mesh infections following inguinal hernia repair and emergency
      operations.The data assessed included gender, age, body mass index (BMI), American Society of
      Anesthesiologists (ASA) score, comorbidities, smoking status, cancer history, the number of
      previous abdominal operations, the number of prior hernia operations, the presence of a
      recurrent incisional hernia and/or enteric fistula and the presentation of the mesh
      infection. Perioperative data included operative time, anesthesia time, associated
      procedures, the defect characteristics and the extension of the pre-aponeurotic dissection.
      Further analysis in the infected mesh (IM) group included the type and position of the
      infected mesh, the causes for the mesh infection and the microbiology of mesh explants.
      Patients were followed and operated at the Abdominal Wall and Hernia Repair Unit of the
      General Surgery and Trauma Discipline, and five surgeons of the team conducted the operations
      in both groups. Informed consents were presented to the patients in the IM group upon
      admission. Patients in the CC group signed informed consents to participate the study, during
      their post-operative follow-up visits.

      Surgical procedure The operations were performed through the previous surgical incision.
      Patients in the IM group had the infected mesh removed completely together with all the
      sutures, tacks or other foreign material. The surrounding fibrotic tissue and the existing
      sinus tracts were resected to perform a complete toilet of the abdominal wall. The abdominal
      cavity was entered in most of the patients, and associated or incidental procedures were made
      as required. After the removal of the infected mesh, or at the end of the abdominal cavity
      workup, all the surgical drapes, instruments and gloves were replaced. The size of the defect
      and the extension of the anterior abdominal wall dissection were estimated. The
      reconstruction of the midline was done as anatomically as possible, by repositioning of the
      muscles and primary closure of the aponeurosis. We did not use component separation
      techniques or transverse abdominal releases in any case. In some patients, a bilateral
      relaxing incision along the anterior rectus sheath was required to allow the re-approximation
      of the muscles in the midline. In all patients, a heavyweight macroporous (pore size > 75µm)
      monofilament polypropylene mesh (Intracorp®, Venkuri, www.venkuri.com.br) was used in the
      onlay position, to reinforce the repair. The mesh was fixed with multiple absorbable Vicryl®
      sutures, placed over the borders of the mesh, in the midline and along the relaxing
      incisions. The remaining dead space between the mesh and the underlying tissue was cleared
      entirely with interrupted sutures. The operative field was irrigated with 0,9% saline, and
      the subcutaneous was drained with suction drains. The scars and the exceeding skin flaps were
      resected. We did not use irrigation with antibiotics solution. The subcutaneous tissue and
      the skin were closed with interrupted sutures. Fluids and samples of the explanted mesh were
      sent to cultures and microbiological analysis. The same technique of repair was used in the
      CC group. The size of the defect was measured, and the extension of the anterior abdominal
      wall dissection was estimated. A bilateral relaxing incision along the anterior rectus sheath
      was used routinely in this group, to allow a tensionless closure of the midline.

      Outcomes parameters The primary outcomes variables were the presence of any surgical site
      occurrences (SSO) or surgical site infection (SSI) during the first 30 days after the
      operation, and the development of hernia recurrence or the recurrence of mesh infection
      during a 36-month follow-up period. Suspected recurrences of a hernia or infection were
      determined by physical examination and CT scan imaging. Non-surgical complications, other
      operations, and deaths were registered during the follow-up period.

      Statistical Analysis The chi-square test was conducted to verify the association between
      categorical variables in contingency tables and the Fisher exact test was adopted in 2x2
      tables whenever at least one expected frequency was less than 5. The U-test was used for
      verifying the association between continuous data and group with two categories, and when
      normal distribution was observed the Student t-test was performed. The 5% level of
      significance was considered for all statistical tests. Statistical computer Stata software
      version 10.0 (StataCorp, College Station, TX) was used for conducting all statistical
      analysis.
    

Intervention name(s): Abdominal wall reconstruction
Intervention type(s): Procedure
Intervention description(s): The repair of abdominal wall defects with polypropylene mesh
Other intervention name(s): Ventral hernia repair
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Intervention model description: A study group submitted to abdominal wall repair with synthetic mesh in the contaminated/infected setting compared to a control group submitted to abdominal wall repair with synthetic mesh in the clean setting.
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: ventral hernia; mesh infection; enteric fistula; polypropylene mesh; synthetic mesh; abdominal wall reconstruction; complex hernia