Primary Abdominal Wall Reinforcement With Synthetic Mesh Following Harvesting of Vertical Rectus Abdominis Myocutaneous Flaps in Multivisceral Pelvic Resections

Following multivisceral pelvic resections, the pelvis and perineum are often reconstructed using myocutaneous flaps. Abdominal wall defects after harvesting rectus abdominis flaps can be reinforced with mesh. Primary reconstruction using synthetic mesh was presently evaluated. Fifty-eight patients who underwent multivisceral pelvic resection and perineal reconstruction with a vertical rectus abdominis myocutaneous (VRAM) flap, January 2004 to February 2014, were retrospectively reviewed. The abdominal wall was reinforced in 26. Demographics, treatment procedures, surgical procedures, length of hospital and ICU stay, early and late morbidity at the recipient and donor sites were recorded. Patients with mesh reinforcement were significantly younger than those without. There were no further significant differences in patient demographics or treatment procedures between the two groups. In 31% of the patients with mesh, surgery was performed on two consecutive days, although total operating time did not differ significantly. Patients without mesh bled more. Surgery was associated with considerable morbidity, without significant differences in overall complication rate between the two groups. At the recipient site, wound infection/ dehiscence was the most common early complication. The group with mesh had higher rate of total flap necrosis necessitating re-operation. At the donor site, wound infection /dehiscence, hernia, or bulge were recorded. Patients with mesh had lower rates of donor site morbidity. Perineal reconstruction with VRAM flap and primary abdominal wall reinforcement with mesh is feasible after multivisceral resection. Our study indicates that primary use of mesh can be applied in potentially contaminated surgical fields in oncologic patients without increasing morbidity and with improved long-term cosmetic results. DOI : 10.14302/issn.2471-7061.jcrc-15-661 Running title: Primary abdominal wall reinforcement in multivisceral resections. Corresponding author: Evita Zoucas MD, PhD, Associate Professor, University of Lund, Department of Surgery, SE-205 02 Malmö, Sweden. email: Evita.Zoucas@med.lu.se


Introduction
Multivisceral pelvic exenteration often represents the only option for sustainable treatment of patients with primary or recurrent advanced pelvic malignancy (1,2).
Musculocutaneous flaps are commonly used to fill the resulting intra-abdominal void created by the exenteration and to reconstruct the pelvic floor and perineum. VRAM flaps weaken the abdominal wall, which can be reinforced using mesh (3,4). Due to potential contamination of the surgical field, there has been considerable controversy regarding implantation of foreign material, primarily, in the abdominal wall (5).
The aim of the present study was to ascertain whether primary reconstruction of the abdominal wall with mesh after pelvic exenteration and harvesting of VRAM flaps is associated with increased risk of complications. An additional objective was to determine whether patient demographics or treatment procedures could identify specific indications for use of abdominal wall reinforcement in this setting.

Patients and Methods
We conducted an observational retrospective cohort study of all patients at our hospital who underwent extended perineal resection for pelvic malignancy and All in-and out-patient medical records were systematically reviewed, and data on the two groups (i.e., those with and those without mesh reinforcement) were analyzed. Clinical data on patient demographic characteristics, comorbidity status, and tumor histology are shown in Table 1. There were fewer female patients in the group without mesh reinforcement. The patients with mesh were significantly younger, and one fourth of them were receiving immunosuppressive therapy other than the oncological chemotherapy. There were no differences in BMI or comorbidity between the two groups. Tumors were either adenocarcinomas of the rectum or anal squamous cell carcinomas.

Surgical Techniques
Operations were conducted as one-or two-session procedures depending on the duration of the oncological part of the surgery and the expected duration of the reconstruction. In two-session procedures, the first stage (day 1) included removal of the tumor, and the second stage (day 2) comprised reconstruction of the perineum and reinforcement of the abdominal wall as appropriate. Perineal resection was performed with the patient in prone jackknife position. Patients were kept on a ventilator in the intensive care unit (ICU) during the non-procedural overnight interval.
In all procedures, general anesthesia was combined with epidural analgesia. When possible, VRAM flaps were rised from the contralateral to the stoma site as described by Tei et al. (6). The flaps consisted of muscle and the overlying adipose tissue and skin, and were raised based on the inferior epigastric artery, including the medial but sparing the lateral perforating vessels.
The flap was rotated intra-abdominally to fill the pelvic defect, with the skin paddle oriented vertically, to  follow-up, respectively), and were identified by physical examination and CT scans.

Post-Operative Regimen
After surgery, the patients were instructed to lie in supine or lateral position on an air-fluidized therapy mattress. Torso elevation of maximum 45 degrees was accepted the first 15 days, and standing and walking, but not sitting, were permitted during the same period.
Thereafter, sitting was allowed for gradually increasing

Statistical Analyses
Continuous data are presented as median (range).
Intergroup comparison was carried out using Fisher's exact probability test and Levene's test for equality of variances. Statistical significance was set at a level of 5%. Statistical analyses were conducted using SPSS software (SPSS Inc., Chicago, IL, USA). procedures between the two groups, but significantly more patients underwent a two-session procedure in the mesh group (31 versus 6%). Differences between the groups with regard to the number of days of hospital stay were not statistically significant (Table 3). Morbidity at the recipient site is outlined in Table 5. Donor-site complications were wound infection with or without dehiscence (early), and hernia or bulge (late), as shown in Table 6. One patient without mesh reinforcement was returned to the operating room due to wound infection, and another was re-operated for an incarcerated hernia at the stoma. One patient with mesh required secondary suture of the abdominal incision. The bulge rate was significantly higher in patients without mesh. No mesh had to be removed due to any complication. Fisher's exact probability test

Discussion
We studied patients with tumors of the rectum and anus VRAM flaps have been used in association with removal of advanced pelvic tumors involving wide perineal resection (8,9). The resulting large pelvic and perineal defects create wounds in irradiated, poorly vascularized tissue that are prone to infection and  (3,10,11,12). As shown in earlier investigations (9,13,14), higher than the level reported by other investigators (10,17). No late morbidity due to incarceration was observed, and the abdominal brace that was provided was not used continuously by many of the patients. In a recent review of materials used for abdominal wall reinforcement, Lee et al. (20) noted that a wound infection rate of 6.4% and a hernia rate of 3.2% were associated with synthetic non-absorbable prosthetics in clean-contaminated cases, which confirms the present results.
We did not find any correlation between the rate of complications and comorbid conditions in our patients.
The present study had several limitations, one of which was the retrospective design with a relatively small number of patients. Also, there is an inherent bias in the outcomes, because the two groups of patients underwent surgery at different times with variable oncological procedures. Furthermore, the patients were not randomly assigned to receiving a VRAM flap or having abdominal wall reinforcement, and we did not evaluate outcomes with regard to restriction of abdominal wall strength.

Conclusion
In conclusion, primary implantation of synthetic mesh appeared to be safe even in the current potentially contaminated field. Nevertheless, it should be noted that implantation of mesh led to operative procedures extending over two days for one third of the current patients, and the patients without abdominal wall reinforcement did not use an abdominal brace.
Accordingly, further studies should be performed that include evaluation of abdominal wall functionality and measurement of quality of life in order to identify patients that can clearly benefit from abdominal wall reinforcement after harvesting of VRAM flaps.