Outcomes of synthetic mesh in reconstruction of complex abdominal wall defects

Outcomes of synthetic mesh in reconstruction of complex abdominal  wall defects

Samir A.Ammar, MD

Department of General Surgery, Assiut University Hospital, Assiut, Egypt.

Introduction: The optimal management of complex abdominal wall defects (CAWD) is still undefined. The purpose ofthis study is to evaluate the use of synthetic mesh to treat CAWD.

Patients  and  methods:  Patients  with  CAWD  treated  by  polypropylene  mesh  (PP)  at  a university hospital between January 2005, and June 2012 were reviewed. The types of repair as well as clinical, operative, and follow-up data were analyzed. The primary outcome variables were surgical site occurrences (SSO) and hernia recurrence.

Results:  One hundred fifty-three patients were included in this study. The average age was

56 years, with an average body mass index (BMI) of 32 kglm?Forty-six percent were women. A staged approach was needed in 28 patients (18.3%) with wound dehiscence and defects that could not be closed. The overall complication  rate was 31.3% (481153). The rate of SSO was

20.2%. The hernia recurrence  or bulge  was observed  in 11% (171153).  Factors  associated with SSO included EMf, bacterial contamination, diabetes mellitus, and emergency procedures. Hernia recurrence was significantly associated with female gender, size of the defect, BMI, liver cirrhosis and surgical SSO. Different techniques of synthetic mesh placement were not found to have a statistically significant difference predicting SSO or hernia recurrence.

Conclusion: The reconstruction  of CAWD frequently requires composite and staged procedures. PP  mesh  can  be used  with  favorable  outcomes  even  in  contaminated  defects. Synthetic  meshes  that  become  infected  can  be  salvaged  with  local  wound  measures  and antibiotics. SSO is found to be significant predictors of hernia recurrence.

Key words: Mesh repair, abdominal wall reconstruction, hernia recurrence.

Introduction:

The aims of abdominal wall reconstruction are to  reestablish  the  integrity  of the myofascial  layer, provide durable cutaneous coverage, and to achieve acceptable surface contour.l Complex abdominal wall defects (CAWD) refer to situations where simple ventral  hernia repair is not feasible  because the defect is very large, there is a concomitant infection or failed previous repair attempt, or ifthere is not enough original skin to cover the repair.2,3 Often the  complexity  is identified before  operation,  but in some cases, events that are encountered (e.g., bowel gangrene) intra-operatively    may   promote    a   hernia from  one  that  was  regarded  preoperatively as simple to one being complex3. Numerous methods  are  available  for  abdominal  wall

reconstruction depending upon the clinical situation, which include presence or absence of contamination, location and size of defect, and soft tissue condition. The optimal management of CAWD is still undefined. The objective of this study is to evaluate the use of synthetic polypropylene (PP) mesh in the repair ofCAWD.

Patients and  methods:

This study included adult patients with CAWD undergoing operative reconstruction using  PP at Assiut University  Hospital between January 2005 and December 2012. Medical records were analyzed for patient demographics, including age, sex, body mass index (BMI), comorbidity, and outcome measures    such   as   wound   complications

and recurrence. The criteria used to define patients  with CAWD included  one or more of  the  following:  (1)  width  greater  than15 em; (2) recurrence with a previous mesh; (3) cutaneous infection or absence of stable skin coverage; and (4) emergency surgery with bowel resection. Hernia width was calculated based  on  the  intra-operative   measurement of the horizontal  distance in em between the lateral margins of the fascial defect. Patients were excluded from analysis if they had post­ traumatic defects, defects resulting from excision of abdominal wall tumors, or defects after gangrene of abdominal wall.

Surgical techniques:

All patients with ventral hernias underwent exposure   of   the   hernia   sac   and   fascial margins  of the  defect  through  an elliptical skin  incision   incorporating   any  redundant skin  and fat as well as the cutaneous  scars. The  musculo-fascial   margins  of  the  defect were  defined clearly. A low-tension  closure of the defect was performed with or without a relaxation incision or component separation. Mesh  placement  was  performed  according to the discretion of the surgeon. For cases in which the fascia could not be approximated without tension, the mesh was placed as a bridge with autologous tissue transposition; this host tissue barrier consisted of the greater omentum  and a peritoneal flap derived from the hernia sac. The mesh should lie flat, with neither folds  nor tension,  and be secured to the fascia with non-absorbable  sutures.

In     patients     with     skin     infection     or

necrosis  Figure(l), the lesion was managed with   antibiotic   treatment,   debridement   of necrotic tissue and local wound  care.  When the  inflammatory  signs  disappeared   and  a negative culture was obtained,  patients were considered for definitive surgery. Giant ventral hernias  cause  overabundance  or sagging  of the  overlying   skin.   Contouring   procedure was  performed  at  the  time  of  the  hernia repair; as the  goal is to restore an aesthetic shape  to  the  abdominal  wall  Figure(2,3). Staged repair or planned ventral  hernia was needed  in  critically  ill  patients  with  intra­ abdominal  sepsis  and contaminated  defects

that could not be closed. These defects can't be closed by tension sutures due to edema of the viscera or relative deficiency of tissue. Methods of staged repair included skin only closure Figure(4), split-thickness skin graft Figure(5), or spontaneous epithelization by secondary intention.

Postoperative management and follow-up: The          patients             were     closely observed

postoperatively   for  adequate  pain  control, urine output, and blood gases. As soon as practical,  the  patient  was  raised  to  about

45-degree  flexion  of  the  trunk  in  order  to allow  maximum  pulmonary  ventilation  and to decrease tension on repair. The intravenous infusion was continued until return of bowel sounds. Semisolid and solid diets were then gradually advanced. The patient remained catheterized until he/she were able to get out of bed. The drains were removed when the output was less than 50 cc within the 24-hours period. Patients were discharged when they recovered their autonomy, pain was well tolerated,  and the surgical team was satisfied that there were no immediate  complications. Outpatient follow-up  was at 1, 3, 6, and 12 months, and yearly thereafter. Follow-up assessment of hernia recurrence was based on physical examination± abdominal imaging.

Endpoints:

The  primary  outcome  variables  for  this study  were  surgical  site occurrences  (SSO) and  hernia  recurrence.   SSO  were  defined as development of an infection at 30 days; formations of a seroma, hematoma or fistula; or wound dehiscence.4,5 Seroma was defined as accumulation of noninfected fluid after removal  of  drains,  which  need  aspiration, while surgical site infection was reported if there is purulent drainage from the incision or local signs and symptoms of inflammation or infection. Abdominal bulge was defined as an abnormal protrusion ofthe abdominal contour, with no underlying defect, as observed in a postoperative physical examination with the patient in the standing  position. A recurrent hernia was defined as a fascial defect palpable on  physical  examination  and/or  visible  on

the CT scan. Wound dehiscence or wound disruption is separation of the edges  of the wound   with   protrusion  or  evisceration of abdominal contents.

Statistical analysis

Data were  analyzed  using a commercially available  software program  (SPSS  9 for Windows).  Differences between groups were compared using  chi-square test.  Continuous data  were   analyzed  using   Student's  t-test. P-values  of less than  0.05  were  regarded as significant.

Results:

One hundred fifty-three patients were included  in this  series.  The average  age was

56 years, with an average body mass index (BMI)  of 32 ± 6.6 kg!m2. Mean hospital  stay was   7.9  ± 6.5  days.   The  mean   follow-up was 28 months  (range,  6-72).  The operation was  performed   as  an  emergency procedure in  100  patients   (65%).   The  characteristics of patients, defects, and repair are shown in Table (1). Astaged approach was needed in 28 patients  (18.3%) with wound  dehiscence and defects that could not be closed. The overall complication rate was 31.3%  (48/153).

Analysis of surgical  site occurrences:

SSO    were    identified    in   31    of    153 (20.2%) patients. Twenty patients (13%) developed  surgical  site infection, and were managed with  antibiotics and  local  wound care.  Eight  patients   (5.1%)   had  seroma   in the   subcutaneous  tissue   and   were   treated with percutaneous aspiration and external garment  compression. Three  patients  had exposure  of  the  mesh.  After  a  brief  course of antibiotics, outpatient debridement and treatment   with    repeated     dressings,   the wound  healed  by secondary intention  within

4-6 weeks.  Excision  of exposed  part  of  the mesh  was  needed  in two  patients.  Complete removal   of  the   mesh   was   not  needed   in any  of  these  patients, and  none  developed chronic mesh infection.  Defect size and mesh placement technique were not found  to have a statistically significant  difference  predicting SSO   Table (2).   Factors   that   significantly

predict SSO included diabetes mellitus, liver cirrhosis,  BMI,  bacterial  contamination, and emergency operation.

Analysis of hernia recurrence and bulge: Eleven   patients   had   hernia   recurrence,

and six patients had abdominal wall bulge. Patient's age, mesh  placement technique, bacterial  contamination, and emergency operation  were  not  found   to  have   a statistically significant  difference predicting hernia recurrence or bulge Table (3). Patients with liver cirrhosis, high BMI, or with defect size greater  than  15 em  were  more  likely  to have  hernia  recurrence  and  bulge.   Women had a higher recurrence rate than men. Hernia recurrence was more common among patients who had SSO.

Discussion:

In  reconstruction  of  abdominal  wall defects, the  surgeon  must take  into consideration  local   wound   condition, optimize  the  utility  of  remaining tissues, reinforce   the   abdominal  wall   with   mesh, and provide  healthy  skin  coverage. Tension­ free repair technique has gained wide acceptance, and surgeons  have developed various  techniques to  achieve  this  purpose; such  as  prosthetic  mesh  repair,  autologous tissue  grafts  repair,  acellular dermal  matrix patch  repair,  and components separation technique.  Mesh   augments the  strength   of the  weakened abdominal wall  and  achieves a  tension-free  repair.   To  decrease   tension and to  reduce  the  size  of  the  mesh  needed, it is sometimes combined with  a component separation. Components separation technique allows  enlargement of the abdominal wall surface  by separating muscle  layers  without damaging the  innervation or blood  supply to the muscles.6

The principles  of ventral  hernia repair  are optimization ofthe patient,  preparation ofthe wound, reapproximation of the rectus muscles alongthemidlinetothe extent possible, and the use  of appropriate prosthetic repair  material to  reinforce   the   closure.7  Optimization  of the patient is done by weight reduction, improvement of nutritional status, adjustment

of  any  comorbidity, and  smoking cessation. There are two stages of preparation of wounds that  may  complicate cutaneous  coverage  of abdominal hernia.  The  first  occurs  prior  to surgery; this stage may include  percutaneous drainage   of  any  abscesses, management of the lesion  with antibiotic and debridement of necrotic tissue.  When the inflammatory signs disappear and  a negative  culture  is obtained, definitive surgery  is considered. The  second stage   occurs   in  the  operating  room;  sharp debridement  of  all  devitalized  or  infected tissue  to reduce  the  bioburden  of the wound is critical,  and  contaminated wounds  should be cleaned  by lavage.8  If the  bioburden  can be  successfully  managed,  then   immediate

reconstruction can be performed.7 Otherwise,

definitive repair  is postponed.

In  the  era  of  "damage  control" surgery following severe  abdominal  trauma or sepsis, an  increasing number  of  patients   is treated with an open abdomen technique. Planned ventral hernia refers to a management strategy where  the  abdominal  fascial  layer  has  been left  unclosed  and  the  viscera   are  covered with original  or grafted skin.9 The short-term aims oftemporary abdominal closure include protection ofthe viscera and preventing fistula formation, and  enabling safer  future  fascial and   skin   closure.lO  In  this  study,   planned ventral   hernia   was  needed   in  28  patients (18.3%) with  abdominal  wound  dehiscence. Patients  with  abdominal wound   dehiscence in the  immediate post-operative period  have wound infection, visceral  edema  and poor general  condition. Sometimes, these  defects cannot  be  closed  by tension sutures   due  to edema  of the viscera  or relative  deficiency  of tissue. Leaving the fascia open (laparostomy) may be the optimal  approach in treating such patients to avoid abdominal compartment syndrome and  to  improve  survival. In these situations, the hernia  is a favorable outcome with the aim of repairing the hernia  at a later stage  when  it is safe,  possible  and  tolerated by the patient.

When a synthetic  mesh is used for repair of

CAWD,  the following conditions need  to be met: availability of normal  skin to cover the mesh, separation of the underside of the mesh

from viscera by the greater  omentum and a peritoneal flap derived  from the hernia  sac to avoid   bowel  erosion  with  fistula  formation or   excessive  adhesions.  The   ideal   mesh should be non-absorbable, biocompatible, preserve  the physiological elasticity of the abdominal wall  and allow proper  integration with the surrounding tissue.ll Monofilament PP meshes can resist infection with higher bacterial clearance compared to multifilament meshes  and  composite meshes  with  an anti­ adhesive barrier.l2 Unique properties of synthetic PP material should  be considered when  evaluating a prosthetic mesh  for  high­ risk hernia repair.

SSO  are  difficult  to  completely avoid  in

patients with CAWD. In this study, many patients   had  risk  factors   for  SSO  such  as high    BMI,    multiple     comorbidities,   and bowel  resection.  The reported rate of SSO is

20.2%.   Patients  with  surgical  site  infection are   successfully  treated   by   antibiotics   in combination   with    repeated    dressing.    PP mesh was salvaged  in all patients  with  SSO; only   two   patients    required    partial    mesh excision.  The  decision  for  mesh  removal  is determined clinically.  Grossly  infected  mesh that is unincorporated into surrounding tissue

should  be removed when  found. 13 A number

of  studies,   including  this  study,  challenge the   surgical   dictum   that   a  synthetic  mesh is contraindicated in a contaminated field during  open  abdominal wall  reconstruction. Several  series  have  reported  favorable outcomes of synthetic  mesh used m contaminated fields.l4,15 Two prospective randomized trials  of lightweight PP mesh placed  prophylactically at the time  of stoma creation  in the retro-rectus position  have reported     excellent    long-term   resultsl6,17_ Other investigators continued to share their successful experience with synthetic mesh in contaminated fields.l5,18-19

In   acutely    strangulated   hernia,    Zafar and colleagues20 noted a 38% wound complication  rate  when  a  bowel   resection was performed versus 28% without  bowel resection. Despite  slightly  higher  infections with  bowel  resection, no  mesh  required removal, even in five patients  who developed

Figure (1): Incisional hernia with necrosis of skin coverage (a). The same patient after debridement of necrotic tissue and local wound care for 3 weeks.

Figure (2): Reoperativefront and lateral views (a,b) of a giant complicated umbilical hernia in patient with liver cirrhosis. Postoperative view of the same abdominal wall after reconstruction using synthetic polypropylene mesh (c).

Figure (3): Preoperative front and lateral views (a,b) of incisional hernia with ulceration of skin coverage. Postoperative view of the same patient (c).

Figure (4): Patient with liver cirrhosis and mesenteric vascular occlusion developed burst abdomen on the 9th postoperative day (a). The same patient after 3 weeks of local wound care (b). The same patient after skin only closure (c).

Figure (4): A case of planned ventral hernia with split-thickness skin graft.

Table 1. Patient, defect, and repair characteristics.

a With defects that could not be closed

b COPD: Clu·onic obstructive pulmomuy disease

deep  infections.  On  the  other  hand,  Abd­ Ellatif and colleagues21 used PP mesh repair for  strangulated   hernia.  They  expetienced a low rate of wound infections between the patients with and without bowel resection. Although  the wound  complication  rate may be increased with bowel resection, the mesh never required removal.22,23 Bessa andAbdel­ Razek24 analyzed  the combined  results of prosthetic mesh repair in cases of strangulated hennas available in the literature. Combined analysis  of  572  patients  support  the safety of prosthetic mesh  for the repair of hennas

that present strangulated, requmng bowel resection.

Two factors are common between the 1isk

factors for SSO and henna  recunence; high BMI and  liver cinhosis. Another  important finding of this study is the role of SSO on predicting henna  recunence  and bulge. This finding is sinrilar to that repmted by other studies.5,25 Mesh  placement  techniques  are not found to have a statistically significant difference   in   SSO   or   henna   recunence. In Coclu·ane Systematic  Review, trials companng onlay  and  sublay  positions  for

Table 2. Factors affecting  surgical site occurrences.

* Stattsttcally  stgnificant

incisional hernias showed no difference in recurrences.26   Recurrence  after   abdominal wall hernia  repair has been shown to be correlated with factors that cause poor wound healing,   such  as  obesity,27  diabetes,28  and liver cirrhosis.  In the present study, smoking is not found  to be a significant predictor  ofSSO or hernia  recurrence. In a study  by Rosen  et al,29 there  was no significant  difference  with respect to recurrence or wound  morbidity between   smokers   and  nonsmokers.  Women had a higher recurrence rate than men in this study. In consistent with this result, Lin et al30 reported  significantly higher  recurrence rate in female  gender.

Although   retrospective     study    is   good for   analyzing  multiple    outcomes,  and   it can  accumulate data  for  a  large  number  of patients, an inherent  weakness of  the  study is  the  potential for  selection  bias  and  the

liability  for  great  deal  of  missed  data.  The

accuracy  of the  data  collected   is dependent on the  quality  of information in the  medical record.  In this study, cases with synthetic PP mesh in CAWD repairs are selected. The type of PP mesh,  light weight  or heavy  weight,  is not known in most cases and consequently, excluded  from  analysis. There  are other patients with CAWD who had repair either without  mesh  or with  other  types  of meshes and were excluded from this study.

Conclusion

The management of CAWD is challenging and frequently requires  composite  and staged procedures. Each repair should  be tailored to both the characteristics of the defect  and the patient. PP mesh can be used with favorable outcomes   even   in   contaminated   defects. Mesh that becomes infected  can be salvaged with  local  wound  measures and  antibiotics.

SSO  is found  to  be significant  predictors of

Am-ShamsJSurg2014;7(2):303-312

Table 3. Factors affecting recurrence or bulge after repair.

*Statistically significant

hernia recurrence.

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