In this retrospective registry-based PSM analysis, MWPP and HWPP were found to have similar short-term outcomes when used in contaminated open retromuscular ventral hernia repairs. These similarities were also found between single sheet and paneled sheets of HWPP mesh.

The successful use of polypropylene mesh in contaminated (CDC II/III) retromuscular hernia repairs has been consistently reported over the past decade, as the advent of a transversus abdominis release has allowed for wide adoption of retromuscular techniques for complex ventral hernias [10, 11]. The largest series of 402 patients by Warren et al. reported a 2.4% rate of mesh excision and 0 enterocutaneous fistula with 21 month median follow-up. Likewise, our recent randomized trial comparing MWPP to biologic mesh found that the synthetic mesh had similar rates of wound morbidity and was more durable at 2 years. However, reports of the effective use of polypropylene in this setting have exclusively focused on lightweight (density < 40 g/m2) and mediumweight (density 40–60 g/m2) polypropylene and its success has been attributed to its density and macroporosity. Theoretically, lighter weight/larger pored materials allow for increased flexibility, tissue ingrowth, and bacterial clearance [7, 12, 13]. However, we have considered the possibility that polypropylene mesh weight and porosity are not as critical to its resilience as is often regarded and that HWPP (density > 75 g/m2) may perform just as well in contaminated cases of elective open retromuscular hernia repair. Our data in the context of elective retromuscular repairs is consistent with the initial studies of HWPP almost 70 years ago that highlighted the material’s impressive resistance to microorganisms [14]. More contemporary studies support antimicrobial properties of polypropylene mesh with resistance to MRSA adherence [15, 16].

Apprehension to using synthetic mesh in contaminated settings pre-dated modern retromuscular techniques and ironically originated with the use of HWPP (Marlex®) mesh in complicated cases of intra-abdominal catastrophe. Marlex® 50 (Bard-Davol, Cranston, RI), a heavyweight mesh employed in the use of hernia repairs, eventually led to the adoption of Marlex® by the US military for use in closing contaminated abdomens with large defects and other highly contaminated scenarios [17,18,19]. Subsequently, Voyles et al. reported their 5 year experience using Marlex® intraperitoneally in 31 heavily contaminated ventral hernia repairs, 25 consisting of necrotizing soft-tissue infections (many with associated intra-abdominal sepsis) and found that early success was curtailed with late development of enterocutaneous fistula development and wound complications requiring mesh excision warranted second thought to the use of this permanent material [20]. Other studies performed in the 1980s made similar conclusions to Voyles et al. with significant wound morbidity issues at long-term follow-up time points [21]. When considering our contemporary use of HWPP in contaminated scenarios, the importance of distinguishing that these are elective cases with a prosthetic in a well-vascularized retromuscular plane cannot be underscored enough. The absence of mesh excisions or enterocutaneous fistulas in our HWPP cohort begin to validate that this context is separate and distinct from those remote cases but also emphasizes the importance of long-term follow-up.

The use of mediumweight monofilament polypropylene seems to be effective in the majority of context during the perioperative period; however, our group became concerned due to a recent analysis that demonstrated a 4.2% fracture rate of MWPP at 1 year following open retromuscular ventral hernia repair, a rate that increased to 30% in bridged scenarios [22]. In an era when retromuscular repairs are becoming ubiquitous, we are concerned that rates of mesh fracture may increase, particularly with longer follow-up and leave a large contingency of patients needing another repair after the retromuscular space has been utilized. Furthermore, for contaminated (CDC II/III) scenarios when concomitant abdominal wall reconstruction is being entertained, this rate of mesh fracture adds another layer of complexity when considering delaying definitive hernia repair and staging reconstruction. As such, an additional impetus for this analysis was to investigate whether HWPP could be utilized in these concomitant cases to allow for similar durability and the avoidance of another operation.

Today, we are less hesitant to utilize HWPP in CDC II/III fields. A residual limitation remains scenarios where wide mesh overlap is needed and anterior fascial coverage is not possible, leaving a bridged scenario. In this scenario, where MWPP is most vulnerable to mesh fracture, we either utilize a 50 × 50 cm MWPP or paneled HWPP. This drove a sub-analysis of the single sheet vs. paneled HWPP mesh, which did not show any differences in outcomes at 30 days. As mesh industry continues to advocate for absorbable meshes at astronomical cost, perhaps a simpler approach would be to create larger sheets of an already well-studied product. At the time of this article, Surgimesh® (BG Medical, Deer Park, IL), is made in larger HWPP sheets; however, the outcomes of this multifilament alternative are currently unknown.

This study has several limitations to address. The overall number of patients included in analysis is small and may not accurately reflect the true incidence of complications in this population. Many surgeons feel that 30 day outcomes are not long enough, even for short-term wound complications. Certainly, longer-term follow-up is needed to truly comment on the safe use of HWPP mesh in contaminated settings. While propensity score matching helps to equalize comparator groups, the retrospective nature of this data introduces the potential for selection bias. The ACHQC, while nationwide, may not represent common practice as many surgeons that participated in the ACHQC are hernia experts with high level of interest in hernia surgery, thus these results may not be generalizable.