Reconstitution of the anterior abdominal wall RECONSTRUCTIVE

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1 RECONSTRUCTIVE Acellular Dermal Matrices in Abdominal Wall Reconstruction: A Systematic Review of the Current Evidence Jeffrey E. Janis, M.D. Anne C. O Neill, M.B.B.Ch., Ph.D. Jamil Ahmad, M.D. Toni Zhong, M.D. Stefan O. P. Hofer, M.D., Ph.D. Dallas, Texas; and Toronto, Ontario, Canada Background: Reconstruction of the anterior abdominal wall is a complex procedure that can be complicated by contamination, loss of domain, previous scarring or radiotherapy, and reduced availability of local tissues. With the introduction of acellular dermal matrices to clinical use, it was hoped that many of the problems associated with previous synthetic materials could be overcome. With their enhanced biocompatibility, acellular dermal matrices are believed to integrate with surrounding tissues while demonstrating resistance to infection, extrusion, erosion, and adhesion formation. Methods: The MEDLINE database was reviewed, including all publications as of December 31, 2011, using the search terms dermal matrix or human dermis or porcine dermis or bovine dermis, applying the limits human and English language. Prospective and retrospective clinical articles were identified. Results: A total of 40 eligible articles were identified and included in this review. Thirty-five of the studies were level IV; the remaining studies were level III. Acellular dermal matrix was used to reconstruct the abdominal wall in a wide range of clinical settings, including trauma, tumor resection, sepsis, and hernia repairs. The operative methods varied widely among clinical studies. While the heterogeneity of the patient populations and techniques limited interpretation of the data, concerns were identified regarding high rates of hernia recurrence with acellular dermal matrix use. Conclusion: High-quality data derived from level I, II, and III studies are necessary to determine the indications for acellular dermal matrix use and the optimal surgical techniques to maximize outcomes in abdominal wall reconstruction. (Plast. Reconstr. Surg. 130 (Suppl. 2): 183S, 2012.) CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV. From the Department of Plastic Surgery, University of Texas Southwestern Medical Center at Dallas; the Division of Plastic and Reconstructive Surgery, Department of Surgery, University of Toronto; and the Division of Plastic Surgery, Department of Surgery and Surgical Oncology, University Health Network. Received for publication February 28, 2012; accepted March 7, Copyright 2012 by the American Society of Plastic Surgeons DOI: /PRS.0b013e cfc Reconstitution of the anterior abdominal wall is a challenging reconstructive procedure that aims to provide protection for the abdominal contents and restore functional support and integrity. 1 Acquired defects of the abdominal wall may result from previous surgery, resection of tumors, trauma, or severe infections. Such cases may be complicated by contamination, loss of domain, scarring from previous procedures or radiotherapy, and the absence of local tissues for reconstruction. Many strategies have been employed in an effort to provide effective restoration of integrity that can withstand the dynamic stresses placed on the anterior abdominal wall. Autologous tissue techniques, including components separation, local flap, and free tissue transfer, have Disclosure: Dr. Janis serves as a consultant for LifeCell Corporation. Dr. Zhong has received funding from the Plastic Surgery Foundation for onestage breast reconstruction using dermal matrix/ implant versus two-stage expander/implant procedure (AlloDerm randomized clinical trials). Drs. O Neill, Ahmad, and Hofer do not have any financial interest with any of the products or devices mentioned in this article S

2 Plastic and Reconstructive Surgery November Supplement 2012 been widely described. 2 Despite the obvious advantages, there are often inadequate local tissues to provide complete restoration of the abdominal wall, and many patients in this population would be unsuitable candidates for free tissue transfer. These problems have led to the development of synthetic materials that can be used alone or in combination with autologous tissues. 3 Although beneficial in many cases, these materials can be associated with high rates of infection, delayed wound healing, fistula formation, and seroma. 4 Acellular dermal matrices were introduced in 2003, and they have many theoretical advantages over synthetic materials, largely resulting from their enhanced biocompatibility. Advocates claim that this material has an increased capacity for integration with surrounding tissues while demonstrating resistance to infection, extrusion, erosion, and adhesion formation. 5 These properties make acellular dermal matrix an attractive option for abdominal reconstruction, as it can be placed directly on exposed viscera and used in contaminated fields. In 2010, we reviewed the existing literature describing outcomes after abdominal wall reconstruction with acellular dermal matrix. 6 This review failed to provide conclusive evidence on the advantages of matrix use over options for abdominal wall reconstruction. In addition, the reviewed studies did not provide any definitive information on what, if any, technical aspects affect outcomes. Since 2010, several additional studies have been published. 7 9 This updated systematic review of the current literature provides an overview of the current evidence supporting the use of matrix in abdominal wall reconstruction. PATIENTS AND METHODS The MEDLINE database was reviewed, including all publications as of December 31, 2011, using the search terms dermal matrix or human dermis or porcine dermis or bovine dermis, applying the limits human and English language. Prospective and retrospective clinical articles were identified. Exclusion criteria included animal studies, case reports, reviews, and clinical series of congenital abdominal wall defects, inguinal, parastomal, or hiatal hernias, or enterocutaneous fistulas. All articles eligible for inclusion were manually cross-referenced to identify additional studies not captured by the MEDLINE search. Validation of the search results was conducted by two independent reviewers (A. O. N. and J. A.). RESULTS As of December 31, 2011, 12,807 articles of potential interest were identified using the broad search terms dermal matrix or human dermis or porcine dermis or bovine dermis (Fig. 1). Filtering this group with the search terms abdomen or hernia reduced the articles of interest to 343. A review of the titles in this subset found that 302 articles failed to meet the a priori criteria. The remaining 41 abstracts were reviewed, and 35 were found to meet the a priori criteria. These articles were examined in detail, and one further study was excluded based on the a priori exclusion criteria. The 34 eligible articles were manually cross-referenced, identifying an additional 12 articles, six of which met the inclusion criteria. A total of 40 articles were identified and included in this review (Table 1). The inclusion of expanded search terms and the extended time period revealed 10 additional articles that had not been identified in our earlier systematic review. No level I or level II studies were identified. Studies included seven level III studies, 7,10 15 and 33 level IV studies 3,8,9,16 46 (Table 2). Data were collected retrospectively in the majority of studies (n 37) 7 46 and prospectively in the remainder (n 3). 10,40,45 Human acellular dermal matrix was used in the majority of studies (n 34), 7,8,11 28,30 37,39,41 45 porcine acellular dermal matrix was used in five studies, 9,10,29,38,42 and bovine acellular dermal matrix was used in one study 46 (Table 3). The average number of patients included in the studies was 36 (range, two to 240 patients). Indications and Surgical Technique The indications for abdominal wall reconstruction varied widely and included tumor resection, ventral and incisional hernias, acute trauma, intra-abdominal sepsis, and necrotizing fasciitis. Acellular dermal matrix was used for primary reconstitution of the anterior abdominal wall defects and repair of primary and recurrent hernias. The surgical technique varied widely among studies (Table 4). For cases in which primary fascial closure could be achieved, the acellular dermal matrix was usually either placed beneath the fascia as an underlay or above the fascia as an overlay. In some cases, the matrix was placed above and below the fascia using a sandwich technique. When primary fascial closure was not possible, the acellular dermal matrix was used as an interpositional graft to bridge the defect. The matrix was used in single and multiple layers. The technique for inset of the matrix also varied 184S

3 Volume 130, Number 5S-2 Abdominal Wall Reconstruction Fig. 1. Process of study selection. Reprinted from Zhong T, Janis JE, Ahmad J, Hofer SO. Outcomes after abdominal wall reconstruction using acellular dermal matrix: A systematic review. J Plast Reconstr Aesthet Surg. 2011;64: , with permission from Elsevier. among studies and was not always described in detail. The sheets were most commonly secured using nonabsorbable monofilament sutures (e.g., polypropylene) in an interrupted or continuous fashion. The matrix was sutured either directly to the fascial edge or, more commonly, with a fascial underlap/overlap, although the degree of underlap/overlap varied widely or was not completely described. Acellular dermal matrix was also commonly combined with other established techniques for abdominal wall repair. Components separation was often performed to achieve fascial closure or to decrease the width of the fascial defect, which was then bridged or reinforced with acellular dermal matrix. Other studies combined matrix with synthetic meshes, most commonly exploiting the tensile strength of the mesh while ensuring that only the matrix was in contact with the underlying viscera. 7 9 As there is no commonly accepted surgical protocol, the indications for the various methods of use were based largely on the personal 185S

4 Plastic and Reconstructive Surgery November Supplement 2012 Table 1. Summary of Studies Included in This Systematic Review ADM Type No. of Patients Indication Technique Follow-Up (mo) Study 6 1 LOE Cobb and Shaffer, III Porcine ADM: 55 Ventral/incisional/recurrent Laparoscopic ventral Composite mesh: 84 hernia hernia repair 31 Gupta et al., III Human ADM: 33 Ventral hernia Interposition Espinosa-de-los- Monteros et al., III Human ADM: 37 Porcine SIS: 11 Overlay 29 0 Underlay PP mesh: 39 Abdominal wall reconstruction CS overlay Overlay PP mesh Primary/ Recurrent Hernia (%) 5 20 Jin et al., III Human ADM bridged: 11 Abdominal wall reconstruction Bridged (interposition/ underlay) ADM/CS reinforce: 26 Reinforced CS (onlay/ underlay/sandwich) 24 (18 37) (6 31) 20 Ko et al., III Human ADM CS: 18 Ventral hernia repair Reinforced CS underlay 10 (3 d 74 m) 33.3 Soft PP mesh CS: 18 0 CS: Ko et al., III Human ADM CS: 26 Ventral hernia repair Reinforced CS underlay 17 (3 36) 46 Soft PP mesh CS: (4 26) 11 Brewer et al., III Human ADM: 34 Ventral/incisional hernia Interposition/underlay/ 26 (no range) 23.5 Mesh: 26 (transplant patients) overlay 76.9 Primary repair: TFL: 9 CS: 5 HADM mesh: 4 HADM TFL: 1 Guy et al., IV Human 9 Abdominal compartment syndrome Buinewicz and Rosen, IV Human 44 Incisional hernia/tram flap donor site Interposition 20 (11 30) 11 Overlay multilayer interposition 20 (8 32) 5 Butler et al., IV Human 12 Tumor resection Inlay 6 (2 13) 0 Nemeth and Butler, IV Human 12 Tumor resection Inlay 43 (41 53) 8 Kolker et al., IV Human 16 Incisional/recurrent hernia Multilayer with underlay/overlay/cs 16 (9 23) 0 Diaz et al., IV Human 75 Ventral hernia repair Inlay/interposition/ 9 (no range) 16 onlay/cs Underlay CS 6 (0 16) 10 Kim et al., IV Human 29 High-risk/recurrent hernia repair Parker et al., IV Porcine 9 Complicated fascial defects Underlay 18 (no range) 11 Interposition 9 (5 27) 50 Schuster et al., IV Human 18 Contaminated abdominal wall fascial defects Scott et al., IV Human 27 Open abdomen Underlay Unreported 0 Bellows et al., IV Human 20 Abdominal wall reconstruction Underlay 9 (2 16) 30 Patton et al., IV Human 67 Contaminated abdominal wall reconstruction Inlay/interposition/ onlay 10 (0 38) 17 (Continued) 186S

5 Volume 130, Number 5S-2 Abdominal Wall Reconstruction Table 1. (Continued) Study LOE ADM Type No. of Patients Indication Technique Lipman et al., IV Human 8 Massive incisional hernia with loss of domain Underlay CS reinforcement (following serial Gore- Tex excision) Follow-Up (mo) Primary/ Recurrent Hernia (%) 10 (2 29) 12.5 Shaikh et al., IV Porcine 20 Incisional hernia/tumor/ trauma Interposition 18 (6 36) 15 Alaedeen et al., ADM reinforcement: 8 IV Human ADM bridging: 2 Ventral hernia repair (contaminated field) Interposition reinforcement (underlay/onlay/ sandwich) 7 (5 8) (2 68) 0 Blatnik et al., IV Human 11 Abdominal wall reconstruction Interposition 24 (18 37) 80 Bluebond-Langner et al., of domain IV Human 27 Large ventral hernia with loss Interposition/onlay/ interposition PP mesh Unreported Not reported (report laxity) De Moya et al., IV Human 10 Open abdomen Underlay 12 (1 12) 17 Candage et al., IV Human 46 Abdominal wall hernia Bridged (underlay), reinforced (onlay/ underlay/sandwich) 12 (1 39) 13 Gu et al., IV Human 3 Abdominal wall reconstruction Underlay omental flap 3 (1 11) 0 Singh et al., IV Human 10 Abdominal wall reconstruction Interposition 10 (0 24) 0 after liver transplant Misra et al., IV Human 70 Ventral/incisional hernia Onlay/underlay/ 12 (no range) 20 interpositional Diaz et al., IV Human 240 Complex ventral hernia repair Inlay/onlay/CS/ interposition 9 (0 38) 17 Hsu et al., IV Porcine 28 Abdominal wall reconstruction Underlay 16 (10 23) 10 Lee et al., IV Human 68 Abdominal wall reconstruction Underlay 15 (no range) 2 Lin et al., IV Human 144 Abdominal wall reconstruction Underlay/interposition/ overlay Maurice and Skeete, IV Human 63 Abdominal wall reconstruction Underlay/interposition/ overlay Tang et al., IV Human ADM: 6; other technique: 21 Abdominal wall reconstruction after tumor resection Interposition/ interposition TFL/ interposition omental flap 5 (0 23) 27 7 (0 24) 41 4 (3 21) 0 Wietfeldt et al., IV Bovine 5 Abdominal wall reconstruction Interposition 10 (9 17) 20 Awad et al., IV Human 17 Abdominal closure after intraabdominal Underlay Not reported Not reported sepsis or necrotizing fasciitis Shinall et al., IV Human 5 Open abdomen (pediatric) Interposition 13 (3 21) 0 Nasajpour et al., 14 (4 24) prosthetic mesh overlay IV Porcine 18 Recurrent ventral hernia Underlay CS Hadeed et al., IV Human Total: 133 (does not report how many received ADM) (outcome measure was infection) Complex ventral hernia Underlay/sandwich CS 6 (0 16) 100 with ADM alone LOE, level of evidence; ADM, acellular dermal matrix; CS, components separation; HADM, human acellular dermal matrix; PP, polypropylene; TFL, tensor fasciae latae; TRAM, transverse rectus abdominis muscle. 187S

6 Plastic and Reconstructive Surgery November Supplement 2012 Table 2. Evidence Rating Scale for Therapeutic Studies* I II III IV V High-quality, multicenter or single-center, randomized controlled trial with adequate power; or systematic review of these studies Lesser-quality, randomized controlled trial; prospective cohort study; or systematic review of these studies Retrospective comparative study; case-control study; or systematic review of these studies Case series Expert opinion; case report or clinical example; or evidence based on physiology, bench research, or first principles *From the American Society of Plastic Surgeons. Evidence-based clinicalpracticeguidelines.availableat: org/documents/medical-professionals/health-policy/evidencepractice/asps-rating-scale-march-2011.pdf. Accessed February 1, Table 3. Types of Acellular Dermal Matrix Products Used in the Included Studies Acellular Dermal Matrix Product Manufacturer Human 1-8,11-28,30-37,39-41,43-45 AlloDerm LifeCell Corp., Branchburg, N.J. Porcine 9,10,29,38,42 Permacol Covidien, Mansfield, Mass. Bovine 46 SurgiMend TEI Biosciences, Boston, Mass. Table 4. Technical Aspects of Acellular Dermal Matrix for Abdominal Wall Reconstruction* Location of acellular dermal matrix Underlay/inlay Interposition Overlay/onlay Sandwiched (underlay and overlay) Type of fascial repair Bridged (no reapproximation of fascia) Reinforced (reapproximation of fascia) Type of suture used Absorbable Permanent *Reprinted with permission from Zhong T, Janis JE, Ahmad J, Hofer SO. Outcomes after abdominal wall reconstruction using acellular dermal matrix: A systematic review. J Plast Reconstr Aesthet Surg. 2011;64: preference of the surgeon. Many studies used a variety of techniques, often changing the operative strategy as their clinical experience with matrix use increased. 16,23,39 Outcome Measures Hernia Recurrence As the primary objective of abdominal wall reconstruction is the reestablishment of longterm integrity and strength, it is not surprising that hernia recurrence is among the most commonly reported outcome measures. The incidence varied widely among studies, from 0 percent to 80 percent. Brewer et al. reported on their experience with human acellular dermal matrix in the repair of ventral hernias in transplant patients. 7 In their series of 104 patients, 34 had repairs using human matrix, while the remaining cases were performed using primary repair, synthetic mesh, or tensor fasciae latae grafts. The lowest recurrent hernia rate was observed in the human matrix group. Of note, this was significantly lower than in the synthetic mesh group (24 percent versus 77 percent). The rates of removal and wound infection were also significantly lower with human matrix compared with synthetic mesh (12 percent versus 69 percent, and 24 percent versus 77 percent, respectively). The authors conclude that human acellular dermal matrix can significantly reduce morbidity in this specific immunosuppressed group. Espinosa-de-los-Monteros et al. compared overlay of human acellular dermal matrix (n 39) with randomly selected cases in which human matrix was not used. 11 In medium-sized hernias, components separation was performed to facilitate direct fascial closure. Human acellular dermal matrix was then used as an overlay to reinforce the repair (82 percent of cases). In the remaining larger hernias, where fascial approximation could not be achieved, polypropylene mesh was used as an underlay followed by a human matrix overlay. The overall hernia recurrence rate was significantly lower in the human matrix group compared with the controls (5 percent versus 20 percent). When human matrix was used in combination with polypropylene mesh in larger hernias, the benefit was not sustained (29 percent versus 30 percent). Not all studies reported positive outcomes however. Ko et al. combined components separation with human acellular dermal matrix or polypropylene or soft polypropylene. The incidence of hernia recurrence was found to be highest in the human matrix group (33 percent), and the authors do not recommend its use except in contaminated cases. 15 In a second study with an extended follow-up period (mean, 17.3 months), the same authors found human matrix to be associated with a recurrent hernia rate of 46 percent. 14 Blatnik et al. reported on a hernia recurrence rate of 80 percent associated with the use of human acellular dermal matrix as an interpositional bridge at a mean follow up period of 24 months. 19 The authors indicated that at 9 months postoperatively, their recurrence rate would only have been 20 percent, calling into question the findings 188S

7 Volume 130, Number 5S-2 Abdominal Wall Reconstruction of series with short follow-up periods. They acknowledged that their recurrence rate is among the highest reported and proposed that this is a true reflection of human matrix, as they have not used it in combination with other synthetic meshes or fascial closure techniques. The authors argue that human matrix in isolation merely constitutes an expensive hernia sac, as the mean cost was $5100 per patient experiencing recurrence, and they suggest that absorbable synthetic meshes could provide similar recurrence rates at one twentieth of the cost. Jin et al. also reported high recurrence rates of 80 percent associated with the use of human acellular dermal matrix as an interpositional bridging graft. 13 This was significantly higher than cases in which human matrix was used to reinforce primary fascial closure (20 percent recurrence), usually combined with components separation. They also emphasized the importance of prolonged follow-up, as recurrences were seen up to 31 months postoperatively. Many of the studies with larger patient numbers had short follow-up periods. 25,33 Abdominal Wall Laxity The incidence of abdominal wall laxity is not as widely documented as hernia recurrence. Difficulties in defining what constitutes laxity may result in variability of reporting. Studies that do not report laxity separately may be including the figures in overall recurrence rates, while others may consider postoperative bulging as a benign phenomenon of little functional consequence. Bluebond-Langner et al. define laxity as clinical evidence of a bulge, which requires secondary reconstruction. 20 In their series of 27 patients, they reported that clinical laxity was observed in 7 of 9 patients who had components separation in combination with interpositional placement of human acellular dermal matrix. Laxity was more common in patients who had surgical site infections and in larger abdominal defects, although this was not an independent risk factor. At reoperation, they noted severe attenuation of the central portion of the human matrix sheet. Secondary repair was performed with polypropylene mesh without recurrence. De Moya et al. reported on their use of human acellular dermal matrix in reconstruction of trauma-related abdominal defects in a small series of patients. 24 They observed a 50 percent laxity rate at 6-month follow-up, which had increased to 100 percent (including one patient with hernia following removal of infected human acellular dermal matrix) at 1 year. Candage et al. reported an eventration rate of 17 percent in their series of 53 patients with predominantly ventral hernia repairs. 23 The incidence of eventration was increased when human acellular dermal matrix was used as a bridging repair compared with reinforced primary fascial closure repairs. The incidence of hernia recurrence was also increased in this group. The authors indicated that acellular dermal matrix can only be used as an interpositional graft if it is accepted that it provides only temporary support without long-term durability, and secondary definitive procedures may be necessary. Factors That May Influence Recurrence Rates The wide variety of clinical indications, patient variables, and surgical techniques make it difficult to definitively identify independent factors that compromise the outcome of abdominal reconstruction with acellular dermal matrix. Type of Acellular Dermal Matrix The most commonly used acellular dermal matrix was human, and there were no studies that compared human matrix with porcine or bovine forms. Shaikh et al. shared their experience with porcine matrix in a series of 20 reconstructions for both acute and chronic abdominal wall defects. 42 They reported an overall complication rate of 35 percent and a recurrence rate of 15 percent. Nasajpour et al. reported no recurrences in 18 patients who underwent ventral hernia repair using porcine matrix underlay following components separation. 9 In addition, a synthetic mesh overlay was used in all cases, making the true contribution of the acellular dermal matrix difficult to evaluate. Hsu et al. and Parker et al. reported recurrence rates of 10 percent and 11 percent, respectively, using porcine matrix as an underlay. 29,38 Wietfeldt et al. reported on the use of bovine matrix as an interpositional graft in a small series, with a 20 percent recurrence rate and a 60 percent incidence of wound healing complications. 46 Position of Acellular Dermal Matrix The position of the acellular dermal matrix appears to have an important influence on recurrence rates. The highest recurrence rates appear to be associated with use of matrix as an interpositional graft (up to 80 percent). 13,16,19 Maurice and Skeete reported a significantly higher incidence of hernia recurrence when matrix was sutured to the fascial edges. 35 Diaz et al. reported lower incidences of recurrence when matrix was used as an underlay, a finding echoed by Lin and coworkers, although these findings 189S

8 Plastic and Reconstructive Surgery November Supplement 2012 did not reach significance. 26,33 Conversely, Gupta and colleagues found the overlay technique to have a lower recurrence rate. 12 Method of Inset of Acellular Dermal Matrix The method of inset of the acellular dermal matrix may also influence the outcome. In studies that specifically reported the suture material used, monofilament nonabsorbable suture such as polypropylene was most common. Diaz et al. reported a reduction in recurrent hernia formation when permanent sutures were used compared with absorbable sutures (10 percent versus 25 percent), although this was not statistically significant. 26 The suture techniques reported included interrupted, mattress, continuous, and a combination of all three. The exact method of inset was also poorly reported, although it is likely to exert an important influence on recurrence rates. In particular, the degree of fascial overlap was rarely specified. The degree of tension placed on the acellular dermal matrix at the time of inset is also believed to be influential. Bluebond-Langner et al. proposed that matrix sheets stretch by up to 50 percent due to their inherent elastic properties and recommend that they be placed under tension. 20 Candage proposed that increasing intra-abdominal pressure and increased collagenase activity in contaminated wounds can cause attenuation of the acellular dermal matrix. 23 Use of Adjunctive Techniques The use of other techniques in combination with acellular dermal matrix repairs is likely to strongly influence outcomes. When fascial approximation can be achieved, matrix is used to merely reinforce the repair strength and, as might be expected, this is associated with a lower incidence of recurrence. Kolker et al. reported no recurrent hernias in their series of 16 patients who underwent ventral hernia repairs using a sandwich technique of matrix underlay, fascial closure, and matrix overlay. 31 Tang et al. also reported low recurrence rates, but their series included a number of patients who had human acellular dermal matrix in combination with free or pedicled flaps for fascial reconstruction. 45 Similarly, studies have combined matrix with synthetic meshes, making it difficult to determine the true contribution of acellular dermal matrix to abdominal wall integrity. 7,9 Environmental Circumstances The influence of contamination on recurrence rates has also been investigated with conflicting results. Buinewicz and Rosen found that postoperative wound infection increased the hazard ratio for recurrence to Bluebond-Langner et al. also reported higher laxity rates in infected cases. 20 Conversely, Candage et al. concluded that hernia and eventration were not increased in infection, and Patton et al. found no association between recurrence and infection. 23,39 Increased body mass index has also been identified as an independent risk factor for hernia recurrence. 25 Complications The incidence of complications varied widely among studies. Delayed wound healing was common and occurred in up to 64 percent of patients. 23 As might be expected in this patient population, infections were frequently reported, varying from superficial wound infections to deep intra-abdominal abscesses. Misra et al. reported decreased infection rates with overlay techniques compared with inlay or interpositional techniques. 36 The infection rate was also increased in diabetic patients. Patton et al. reported a 16 percent infection rate in their series of patients with contaminated abdominal fields, but they failed to identify any association between position of the acellular dermal matrix and infection rates. 39 In many cases, infection did not require removal of the matrix. 30 Awad et al. found an infection rate of 24 percent when acellular dermal matrix was used in infected cases. 17 Culture showed contaminants to be similar to those responsible for the primary infection. All infections were successfully treated with antibiotics without removal of the mesh. Others reported occasional removal of acellular dermal matrix in cases of recalcitrant infection. 10,26,39 Seroma was also commonly reported following matrix use but did not generally affect overall outcome. 35 DISCUSSION This systematic review of the current literature revealed 40 articles reporting the use of acellular dermal matrices in abdominal wall reconstruction. There was a marked absence of high-quality evidence; no level I or II studies were identified. The majority of the studies included were level IV studies, often with small patient numbers and short follow-up periods. The primary outcome measure of these studies was the recurrence of abdominal wall herniation. Overall, the results would indicate that there are concerns regarding the high incidence of recurrent hernias following acellular dermal matrix repairs, but these findings must be interpreted with caution. The heterogeneity of the patient populations makes it difficult to compare among studies. The reported outcomes are likely to be heavily influ- 190S

9 Volume 130, Number 5S-2 Abdominal Wall Reconstruction enced by the variable starting points of the studies. A wide spectrum of cases varying from acute abdominal defects following trauma to recurrent hernias following multiple previous surgeries were included in these studies. Patients undergo abdominal wall reconstructions for a wide variety of clinical indications and often have a large number of significant comorbidities that may strongly influence outcomes. Acellular dermal matrix is a relatively new surgical tool, and indications for its use have yet to be definitively determined. Randomized controlled trials will be necessary to identify the specific patient populations most likely to benefit from its use. Perhaps the greatest problem in interpreting the selected studies lies in the wide variety of surgical techniques described. No clear guidelines exist for the use of acellular dermal matrices in a given clinical scenario. The position of the matrix is particularly contentious. There appears to be some consensus that placement of matrix as an interpositional graft increases recurrence, but there are conflicting reports regarding the superiority of underlay techniques over overlay techniques. The number of matrix layers also varied widely among, and even within studies. The relationship of the matrix to the native abdominal fascia is likely to play a critical role in the success of the repair. Achieving primary approximation of the abdominal fascia is likely to be very important in the restoration of abdominal wall strength but was not always clarified in the reports. Similarly, when the fascia could not be approximated, there was a wide variation in the amount of fascial overlap of acellular dermal matrix underlay, and in many cases this was not specified, although it is liable to influence recurrence rates. The use of acellular dermal matrices in combination with other techniques was also common, making it difficult to identify the independent benefits of the matrix. The optimal method of fixation is also unclear, as an ideal suture type or technique has not been identified. In many cases, the exact surgical technique was poorly described and the methods often changed within studies, resulting in numerous subgroups consisting of small patient numbers. This reflects the general lack of experience with acellular dermal matrix with techniques evolving throughout study periods. Variations in nomenclature pertaining to matrix positioning (inlay versus underlay, onlay versus overlay, bridging versus reinforcement) and outcomes (hernia versus eventration versus bulge) further confound interpretation of the available data. While the current literature offers valuable insights into personal experience with acellular dermal matrix, it fails to provide high-level data that could lead to definitive guidelines for use. Matrices may have a role in the reconstruction of abdominal defects in infected fields where synthetic materials are contraindicated. Prospective level I, II, and III studies and comparative effectiveness study designs are necessary to clearly establish the advantages of matrices over existing techniques, including components separation, prosthetic meshes, local flaps, and free tissue transfers. Current studies using these techniques in combination with acellular dermal matrices have failed to clearly demonstrate what advantages are contributed by the addition of an matrix. CONCLUSIONS Acellular dermal matrices offer many advantages over previous techniques, but their precise role in complex abdominal wall reconstruction has yet to be determined. It is an expensive adjunctive treatment that appears to be associated with high hernia recurrence rates. High-quality studies are needed to identify the patient populations and clinical scenarios in which they may be most beneficial. In addition, clear recommendations regarding ideal surgical techniques with particular emphasis on positioning, tensioning, and insetting of the acellular dermal matrix will be necessary if optimal long-term results are to be achieved. Jeffrey E. Janis, M.D. Department of Plastic Surgery University of Texas Southwestern Medical Center 1801 Inwood Road Dallas, Texas jeffrey.janis@utsouthwestern.edu REFERENCES 1. Rohrich RJ, Lowe JB, Hackney FL, Bowman JL, Hobar PC. An algorithm for abdominal wall reconstruction. Plast Reconstr Surg. 2000;105: ; quiz Ramirez OM, Ruas E, Dellon AL. Components separation method for closure of abdominal-wall defects: An anatomic and clinical study. 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11 Volume 130, Number 5S-2 Abdominal Wall Reconstruction abdominal wall defects. World J Surg. 2007;31: ; discussion Shinall MC Jr, Mukherjee K, Lovvorn HN 3rd. Early fascial closure of the damage control abdomen in children. Am Surg. 2010;76: Singh MK, Rocca JP, Rochon C, Facciuto ME, Sheiner PA, Rodriguez-Davalos MI. Open abdomen management with human acellular dermal matrix in liver transplant recipients. Transplant Proc. 2008;40: Tang R, Gu Y, Gong DQ, Qian YL. Immediate repair of major abdominal wall defect after extensive tumor excision in patients with abdominal wall neoplasm: A retrospective review of 27 cases [corrected]. Ann Surg Oncol. 2009;16: Wietfeldt ED, Hassan I, Rakinic J. Utilization of bovine acellular dermal matrix for abdominal wall reconstruction: A retrospective case series. Ostomy Wound Manage. 2009;55: S