What is the role of MESH (Mesh implant) in hernia repair?

Role of Mesh in Hernia Repair

Mesh provides structural reinforcement to the abdominal wall during hernia repair, significantly reducing recurrence rates by approximately 54% compared to non-mesh repairs, while serving as a scaffold for tissue ingrowth and permanent support of the defect. 1

Primary Functions of Mesh

Mechanical Support and Recurrence Prevention

• Mesh reduces hernia recurrence risk by more than half (RR 0.46,95% CI 0.26 to 0.80), preventing one recurrence for every 46 mesh repairs performed compared to suture-only repairs. 1
• The textile implant provides immediate tensile strength to the repair site, decreasing mechanical failure rates that occur with tissue-only repairs. 2
• Mesh extends beyond the hernia defect boundaries by at least 2-3 cm to distribute tension across a broader area and prevent edge failure. 3

Biological Integration

• Mesh serves as a scaffold for host tissue ingrowth, with fibroblasts depositing new collagen and inducing angiogenesis around the implant material. 4
• Biological meshes become vascularized and remodeled into autologous tissue after implantation, though this process varies based on whether the mesh is cross-linked or non-cross-linked. 4
• Synthetic meshes remain as permanent implants while allowing tissue incorporation through their pore structure. 5

Mesh Selection Based on Surgical Field Contamination

Clean Fields (CDC Class I)

• Synthetic mesh is the standard choice for clean surgical fields, providing optimal recurrence prevention without increasing infection rates. 3, 1
• Polypropylene mesh remains the most commonly used material due to its durability and tissue compatibility. 4
• Large-pore synthetic meshes demonstrate superior resistance to infection compared to small-pore designs. 4

Clean-Contaminated Fields (CDC Class II)

• Synthetic mesh can be safely used even with intestinal strangulation and/or bowel resection without gross enteric spillage, showing no significant increase in 30-day wound-related morbidity. 4, 3
• Surgical site infection rates remain acceptable at 7.1% in clean-contaminated fields when using polypropylene mesh. 4

Contaminated/Dirty Fields (CDC Class III-IV)

• Biological mesh is recommended for contaminated or dirty fields when the defect is >3 cm, as it offers lower susceptibility to infection due to its non-synthetic composition. 4
• Cross-linked biological meshes resist mechanical stress better and demonstrate lower failure rates in contaminated fields compared to non-cross-linked variants. 4
• However, biological mesh carries substantially higher recurrence rates (27.2%, 95% CI 9.5-44.9%) compared to synthetic mesh (3.2%, 95% CI 0.0-11.0%) in contaminated fields, representing a critical trade-off between infection risk and durability. 4
• For small defects (<3 cm) in dirty fields, primary suture repair without mesh is recommended to avoid mesh-related complications. 3

Critical caveat: Absorbable prosthetic materials should be avoided entirely as they inevitably lead to hernia recurrence due to complete dissolution of the prosthetic support through hydrolytic degradation. 4

Mesh-Related Complications

Infection Risk

• Mesh infection occurs in 1.9-5% of cases but represents a catastrophic complication, with 72.7% requiring complete mesh explantation to eradicate infection. 4
• The foreign material creates a decreased threshold for bacterial infection by providing a surface for bacterial adherence and biofilm formation. 6
• Staphylococcus species (particularly S. aureus), Enterococcus species, and Gram-negative bacteria are the most commonly isolated organisms in mesh infections. 4, 6
• Risk factors significantly associated with mesh infection include: emergency operations (RR 2.46), smoking (RR 1.36), ASA score ≥3 (RR 1.40), and longer operative duration. 4, 6

Other Complications

• Mesh repair reduces neurovascular and visceral injuries compared to non-mesh repair (RR 0.61,95% CI 0.49 to 0.76, NNTB = 22). 1
• Seromas occur more frequently with mesh repair (RR 1.63,95% CI 1.03 to 2.59, NNTB = 72), as does wound swelling (RR 4.56,95% CI 1.02 to 20.48). 1
• Mesh repair reduces postoperative urinary retention compared to non-mesh repair (RR 0.53,95% CI 0.38 to 0.73, NNTB = 16). 1
• Specific mesh materials correlate with specific complications: PTFE/polypropylene mesh shows more intestinal complications (14% vs 7%), while biomaterial mesh demonstrates more tissue reactions (57% vs 7%). 7

Infection Prevention Strategies

Intraoperative Techniques

• Change gloves immediately before handling and placing mesh, even if current gloves appear intact, as bacterial contamination increases dramatically over time. 6
• Surgical glove microperforation rates increase from 15.4% at ≤90 minutes to 23.7% when worn longer than 150 minutes. 6
• If surgery duration exceeds 90 minutes before mesh placement, mandatory glove change is recommended for all team members directly handling the mesh. 6
• During hernia repair with bowel manipulation or resection, gloves become contaminated with enteric flora, creating polymicrobial bacterial load that increases mesh infection risk. 6

Antimicrobial Prophylaxis

• Short-term antimicrobial prophylaxis is recommended for incarcerated hernias without ischemia (CDC Class I). 3
• 48-hour prophylaxis is recommended for strangulation and/or bowel resection (CDC Classes II-III). 3
• Full antimicrobial therapy is indicated for peritonitis (CDC Class IV). 3

Clinical Outcomes and Recovery

Hospital Stay and Return to Function

• Mesh repair may reduce hospital stay by 0.6 days compared to non-mesh repair, though results vary widely across studies. 1
• Participants undergoing mesh repairs may return to normal activities of daily living a mean of 2.87 days sooner than those with non-mesh repair, though this finding has substantial heterogeneity. 1
• Operating time averages 4 minutes 22 seconds longer for non-mesh repairs, though this result is uncertain due to wide variation across studies. 1

Mortality

• No deaths occurred during follow-up periods in studies reporting this outcome (7 studies, 2546 participants). 1

Special Populations

Immunocompromised Patients

• Biological mesh demonstrates good results in immune-compromised patients, with a complication rate of 9.4% in transplanted patients undergoing abdominal reconstruction. 4

Emergency Settings

• Emergency ventral hernia repair with mesh can be safely performed without increase in early wound-related or additional 30-day patient morbidity or mortality in CDC wound classes III and IV. 4
• For unstable patients experiencing severe sepsis or septic shock, open management without immediate mesh placement is recommended to prevent abdominal compartment syndrome. 4