What factors affect the repair of a hernia in patients with varying demographics and medical histories, including body mass index (BMI), smoking status, and comorbidities such as diabetes and cardiovascular disease?

Factors Affecting Hernia Repair Outcomes

Multiple patient-specific, surgical, and mesh-related factors significantly impact hernia repair success, with smoking, diabetes, obesity, ASA score ≥3, emergency operations, and mesh infection being the most critical modifiable and non-modifiable risk factors that surgeons must address to optimize outcomes.

Patient-Related Risk Factors

Demographic Factors

• Age: Older patients have significantly higher mesh infection rates (weighted mean difference = 2.63 years between infected and non-infected groups) 1
• Male sex: Associated with 28% increased risk of postoperative delirium (OR = 1.28), which can complicate recovery 1
• BMI: Higher BMI increases recurrence risk after umbilical hernia repair (P = 0.007) and shows a trend toward higher mesh infection rates (RR = 1.41 for obese patients, though not statistically significant) 1, 2
• Underweight patients (BMI <18.5): Face dramatically increased delirium risk (OR = 2.25) which can impact surgical recovery 1

Comorbidities

• Diabetes: Increases risk of postoperative complications within 30 days (OR = 1.35) and is associated with higher recurrence rates after umbilical hernia repair (P = 0.021) 2, 3, 4
• Complicated diabetes (with secondary manifestations): Particularly increases early postoperative complication risk 3
• ASA score ≥3: Significantly increases mesh infection risk (RR = 1.40) and wound complications 1
• Immunosuppression/steroid use: Predictive of mesh infection (OR = 2.22) and associated with higher recurrence rates 1, 5
• Chronic obstructive pulmonary disease: Increases complication rates in combined ventral hernia repair with panniculectomy 6

Lifestyle Factors

• Current smoking: Significantly increases mesh infection risk (RR = 1.36) and recurrence after umbilical hernia repair (P = 0.020) 1, 2, 4
• Smoking status: Active smokers have 37% increased delirium risk (OR = 1.37) compared to non-smokers 1

Cognitive and Social Factors

• Preoperative cognitive impairment: Dramatically increases postoperative delirium risk (OR = 3.99), which can complicate recovery 1
• Lower educational level: Associated with higher delirium rates; college degree or more reduces risk (OR = 0.45) 1
• Institutionalized patients: Face 54% increased delirium risk (OR = 1.54) 1
• History of previous delirium: Strongest predictor of postoperative delirium (OR = 3.9) 1

Surgical and Operative Factors

Urgency and Timing

• Emergency operations: Dramatically increase mesh infection risk (RR = 2.46) compared to elective procedures 1
• Urgent repair: Associated with increased postoperative complications 1
• Operative duration: Longer hernioplasty duration correlates with higher mesh infection rates (weighted mean difference = 44.92 minutes) and increases recurrence risk (OR = 1.11 per hour) 1

Hernia Characteristics

• Hernia type: Most important variable associated with recurrence; incisional and parastomal hernias have higher recurrence rates 5, 4
• Hernia size: Larger defects (≥1.5 cm for umbilical hernias) significantly increase recurrence risk when repaired primarily (P = 0.001) 1, 5, 2
• Previous hernia repair: Increases likelihood of recurrence (OR = 1.99) and wound complications 1, 7, 5
• Femoral hernias: Exceptionally high risk requiring bowel resection (OR = 8.31) 8, 9

Surgical Technique Factors

• Mesh type: Biologic or resorbable synthetic mesh associated with higher recurrence rates compared to permanent synthetic mesh 5, 6
• Mesh position: Onlay position increases risk of mesh explantation (OR = 3.51) 1
• Mesh size: Larger mesh width reduces recurrence risk; inadequate overlap (<1.5-2.5 cm) increases failure 1, 5
• Fascial closure: Reduces recurrence risk; absence increases wound complications (OR = 0.33) 1, 5
• Myofascial release: Associated with lower recurrence odds 5
• Component separation: Increases complication rates in combined procedures 6
• Surgeon experience: Trend toward higher mesh infection when operated by resident versus consultant (RR = 1.18) 1

Intraoperative Complications

• Intestinal violation/enterotomy: Strong predictor of mesh explantation (OR = 5.17) and increases complications 1, 6
• Bowel resection: Associated with contaminated field requiring different mesh selection 1

Postoperative Factors

Infectious Complications

• Postoperative surgical site infection: Predictive of mesh infection (OR = 2.9) and strongly associated with recurrence (P < 0.001) 1, 2, 6
• Mesh infection rate: Overall crude rate of 5%, with most requiring mesh removal 1
• Biofilm formation: Complex pathogenesis involving bacterial virulence and prosthetic material properties; early antibiotics and mechanical irrigation critical 1

Inflammatory Markers

• Preoperative CRP levels: Elevated levels (>10 mg/dL) dramatically increase delirium risk (OR = 3.56), which can complicate recovery 1
• Systemic inflammatory response: Indicates potential strangulation requiring immediate intervention 8

Wound Complications

• Skin dehiscence and necrosis: More common in combined procedures 6
• Seroma formation: Contributes to overall complication profile 6
• Reoperation: Significantly increases recurrence risk 5

Mesh-Related Factors

Mesh Material Properties

• Large pore synthetic meshes: More resistant to infection than small pore meshes 1
• Polypropylene: Most commonly used material for hernia repairs 1
• Biological meshes: Higher cost and potentially less favorable long-term durability, but offer infection resistance in contaminated fields 1

Mesh Fixation

• Improper fixation: Primary mechanism of recurrence through host-prosthesis interface failure 1, 7
• Minimal overlap: Increases separation risk and recurrence 1, 7
• Fixation technique: Transfascial sutures versus tackers affects outcomes; avoid tackers near pericardium 1

Common Pitfalls and Clinical Caveats

• Distinguishing mesh infection from superficial SSI: Mesh infections tend to be indolent with chronic signs, while superficial SSIs occur early postoperatively with typical inflammatory symptoms 1
• Underestimating deep mesh infections: May present with subtle signs rather than obvious local inflammation 1
• Primary closure of large defects: Hernias ≥1.5 cm should receive mesh repair to prevent recurrence 2
• Inadequate mesh overlap: Must extend 1.5-2.5 cm beyond defect edges 1
• Ignoring preoperative optimization: Smoking cessation, diabetes control, and weight management should be addressed when feasible 1, 2, 3
• Concurrent procedures: Laparoscopic inguinal hernia repair performed simultaneously increases recurrence risk (P = 0.044) 2
• Surgical field contamination: Requires different mesh selection strategy; synthetic mesh still recommended in clean-contaminated fields, but biologic/biosynthetic preferred in contaminated/dirty fields 1, 9