Incisional Hernia

Definition

Incidence

• 10-50% after open laparotomy incisions
• 1-5% after laparoscopic port-site incisions
• Midline incisions carry the highest risk compared to off-midline incisions
• Rates can reach 50% in specific high-risk populations

Aetiology and Risk Factors

Patient Factors

• Obesity (increases intra-abdominal pressure AND wound infection risk)
• Diabetes (impairs wound healing)
• Malnutrition
• Immunosuppression / steroid therapy
• Smoking
• Chronic cough / COPD (elevated intra-abdominal pressure)
• Genetic collagen disorders
• Previous wound infection

Wound Factors

• Poor-quality tissue
• Wound tension
• Wound infection / surgical site infection (SSI) - an independent predictor of early (<6 months) incisional hernia formation

Surgical/Technical Factors

• Inappropriate suture material
• Poor closure technique
• Drains brought through the midline wound (prevents fascial apposition)
• Ostomies through the midline incision
• Incorporating fatty/muscular tissue in fascial bites (causes ischemia and necrosis)

Pathophysiology

• Progress rapidly to full-thickness wound dehiscence, heralded by serosanguineous discharge around the 6th postoperative day
• Pass unnoticed if overlying skin has healed, with a visible swelling appearing weeks, months, or years later

Clinical Features

• Localised swelling at the surgical scar, OR diffuse bulging along the whole incision length
• Multiple discrete defects within the same scar are very common (always check full incision length)
• Hernia tends to increase in size over time
• Overlying skin may become thin, atrophic, and prone to ulceration
• Obstruction is common (due to coexisting internal adhesions)
• Strangulation is less frequent - most incisional hernias are shallow and wide-necked; strangulation is most likely when the fibrous defect is small and the sac is large

Risk Stratification

Prevention

1. Preoperative optimisation - smoking cessation, weight loss, glycaemic control, nutritional support
2. Fascial closure technique:
   • Close the linea alba only - do not incorporate fat or muscle
   • Small-stitch, small-bite technique (STITCH trial): 5 mm fascial bites spaced 5 mm apart
   • Suture length:wound length ratio of ≥4:1 (European Hernia Society guideline)
   • Use slowly absorbable monofilament suture (e.g. 2-0 PDS with 30-40 mm needle)
   • Avoid closing under excessive tension
3. Drains must exit through separate stab incisions, never through the midline wound
4. Prophylactic mesh augmentation (PMA) in high-risk patients - reduces incisional hernia formation regardless of mesh plane (onlay, retrorectus, preperitoneal, or intraperitoneal)
5. Use laparoscopic approach when safe and feasible (lower hernia risk vs open)

Treatment

Conservative

• Asymptomatic hernias may not require immediate surgery
• Abdominal binder/belt provides symptomatic relief and may limit enlargement
• Patients with significant comorbidities: balance benefits vs operative risks carefully

Preoperative Optimisation ("Prehabilitation")

• Weight loss (loss of 7% bodyweight achieves significant metabolic improvement; 5 kg body weight ~1 extra litre of intra-abdominal space in adult males)
• Smoking cessation
• Fitness improvement and core-strengthening exercises
• Multidisciplinary team assessment is increasingly standard

Surgical Principles

1. Repair must cover the entire length of the previous incision
2. Musculofascial approximation with minimal tension
3. Prosthetic mesh should be used to reduce recurrence risk
   • Contraindicated in grossly contaminated field (e.g. perforated strangulated bowel)
   • May be used in clean-contaminated field (e.g. elective bowel resection) with strict hygiene and prophylactic antibiotics
4. Mesh should augment primary fascial closure - not "bridge" a gap (bridging repair leads to central mesh bulge)

Mesh Placement Planes (ICAP Classification, 2019)

Surgical Approaches

Open Repair

• Open previous incision along its full length to expose unsuspected defects
• Expose hernial sac, neck, and margins; reduce contents; divide adhesions; excise redundant sac
• Primary suture repair alone (Mayo/da Silva overlap) - NOT recommended due to unacceptable recurrence rates; only acceptable in gross contamination where mesh is contraindicated
• For small hernias (<2 cm): primary closure may be acceptable
• For larger defects: mesh-based repair is standard

Laparoscopic Repair

• Laparoscopy and adhesiolysis performed first
• Hernia contents reduced
• Mesh placed intraperitoneally and fixed with tacks/sutures
• Advantages: less wound morbidity, shorter hospital stay
• Access ports at a distance from the hernia; may need robotic assistance for complex cases

Component Separation

Complications of Repair

• Wound seroma (very common, especially with large flap elevation)
• Wound infection / SSI
• Mesh infection (may require mesh removal)
• Recurrence (lower with mesh vs suture alone)
• Adhesive bowel obstruction (especially with intraperitoneal mesh)
• Visceral erosion/fistula

Key Points Summary

• Incidence: 10-50% after laparotomy; 1-5% after laparoscopic ports
• Most important modifiable prevention factor: fascial closure technique (small-bite, ≥4:1 suture:wound ratio)
• Obstruction is common; strangulation is rare (wide-necked)
• Multiple defects in same scar are very common - always explore full incision
• Mesh repair is standard - simple suture repair has unacceptable recurrence
• Retromuscular/sublay plane is preferred for mesh placement
• Prehabilitation (weight loss, smoking cessation) is important preoperatively

Surgical Steps for Incisional Hernia Repair

A. Open Primary Suture Repair

• General anaesthesia to achieve full relaxation of abdominal wall musculature
• Patient supine, arms out
• Foley catheter for bladder decompression
• Orogastric tube for gastric decompression

• Open through the previous scar along its full length (to expose any unsuspected additional defects)
• Dissect through subcutaneous tissues carefully - sac contents may lie just at the level of the anterior rectus sheath

• Identify the hernial sac and clear it of all attachments to the fascia using electrocautery
• Expose the full circumference of the fascial defect
• Clear fascia of soft tissue both anteriorly and posteriorly for a 3-4 cm margin of healthy fascia all around the defect

• Reduce hernia contents back into the abdominal cavity
• Take down any peritoneal attachments to the anterior abdominal wall
• Open the sac, divide any internal adhesions, and reduce contents
• Excise redundant sac if present

• Clear fascial edges of extraneous fat and muscle (to avoid incorporating ischemic tissue)
• Use a 2-0 slowly resorbable monofilament suture (e.g. PDS) with a 30-40 mm needle
• Running technique with 5 mm fascial bites spaced 5 mm apart
• Suture length:wound length ratio must be ≥ 4:1
• Alternative for wide defects: interrupted figure-of-eight sutures placed loosely along the wound first, then cinched together to distribute tension evenly

• Confirm no additional unsuspected defects
• Confirm sutures are not pulling through tissue (if so, tension is excessive - proceed to component separation)

• Closed suction drain in the subcutaneous space if a large dead-space pocket remains
• Skin closed with staples or running subcuticular suture

Note: If tension is excessive on attempted closure, component separation (Ramirez technique) is required - see below.

B. Open Mesh Repair

• General anaesthesia; supine position with arms out
• Foley catheter and orogastric tube placed

• Incision extends beyond the hernia defect in all directions
• Dissect down to anterior rectus sheath
• Identify the defect; clear fascia with a 3-4 cm margin of healthy fascia circumferentially

• Perform adhesiolysis to free the entire anterior abdominal wall (improves mobilisation and medialization for closure)
• Dissect in planes other than intraperitoneal where bowel is fused to peritoneum to minimise visceral entry
• If intraperitoneal entry is necessary, carefully take down adhesions
• Remove all prior intraperitoneal mesh (reduces infection/fistulisation risk)
• After adhesiolysis, inspect bowel for any inadvertent injury and repair

• If no preoperative bowel obstruction symptoms: anterior abdominal wall adhesiolysis alone suffices
• If signs of bowel obstruction preoperatively: full enterolysis required (with careful judgment to avoid unnecessary dissection of clinically insignificant fused bowel)

• Place a large, counted laparotomy towel over the entire viscera to prevent injury during subsequent dissection and mesh placement

• Mesh is cut to the shape of the defect with a generous circumferential margin added (at least 3-5 cm overlap all around)
• Mesh types:
  • Polypropylene (macroporous, promotes tissue ingrowth/incorporation) - most common
  • ePTFE (microporous, less adhesion but requires secure fixation)
  • Biologic mesh (acellular dermal matrix - for contaminated/infected fields)

• Suture mesh to fascia with large, nonabsorbable interrupted sutures at multiple sites throughout the entire circumference
• Distributes tension evenly across the entire patch
• Ensure ≥3-5 cm overlap of healthy fascia around the defect
• For intraperitoneal mesh: also use tacking staples (laparoscopic tacks)
• Omentum can be interposed between bowel and mesh where possible

• Bring fascial edges together over the mesh (augmented/reinforced closure, not bridging)
• Small-bite technique as described above

• Closed suction drain placed away from the mesh to minimise infection risk
• Layered subcutaneous closure; skin staples or subcuticular suture

C. Laparoscopic Repair

• General anaesthesia; supine with arms tucked
• Foley catheter and orogastric tube
• Ensure port placement sites are distant from the hernia defect

• Initial access away from the scar (open Hasson technique preferred to avoid inadvertent bowel entry)
• Additional working ports placed laterally, well away from the defect

• Divide all adhesions between bowel/omentum and the anterior abdominal wall
• Use sharp dissection (scissors preferred over energy devices to avoid thermal bowel injury)
• Inspect bowel for injury at completion

• Identify all fascial defects from the inside
• Measure the defect accurately using intraperitoneal measurement (usually with a spinal needle and ruler or marking pen on skin)

• Use a barrier-coated mesh (e.g. composite dual-layer mesh) to prevent visceral adhesions
• Mesh sized to overlap defect by 3-5 cm in all directions

• Mark mesh orientation before introduction (to ensure correct positioning once inside)
• Roll/fold mesh and introduce through a port
• Unfurl and position under laparoscopic vision

• Transfascial (full-thickness) sutures placed at cardinal points first (usually 4 sutures: superior, inferior, left, right)
• Circumferential tacking with laparoscopic tackers (~1 cm apart) around the entire mesh perimeter
• Some surgeons use suture fixation alone (avoids chronic tack pain)

• Inspect mesh position, ensure no herniation of bowel or omentum beside the mesh
• Inspect for bowel injury throughout
• Deflate pneumoperitoneum
• Port sites >5 mm closed at fascial level to prevent port-site herniation

D. Component Separation (Ramirez Technique)

Postoperative Care

• Early ambulation
• Abdominal binder for support (reduces seroma, supports repair)
• Avoid heavy lifting for 6-8 weeks
• Monitor drain output (remove when <30 mL/day)
• Wound inspection for seroma, infection
• Address modifiable risk factors (weight loss, smoking cessation, glycaemic control) to reduce recurrence

Recurrence Rates by Technique

Steps of Incisional Hernia Repair

STEP 1 - Preoperative Preparation

• Anaesthesia: General anaesthesia (ensures full abdominal wall relaxation)
• Position: Supine, arms out
• Catheter: Foley catheter (bladder decompression)
• Gastric tube: Orogastric tube (gastric decompression)
• Prophylactic antibiotics: Given before incision
• Optimisation (elective cases): Weight loss, smoking cessation, glycaemic control done beforehand

STEP 2 - Incision

• Reopen through the previous surgical scar along its entire length (not just over the visible bulge)
• Full-length opening is mandatory - clinically unsuspected additional defects are very common along the same scar
• Dissect through subcutaneous tissues carefully - the sac or its contents may lie just beneath the skin at the level of the anterior rectus sheath

STEP 3 - Exposure of the Defect

• Identify the hernial sac, its neck, and the margins of the fascial defect
• Using electrocautery, clear the sac of all attachments to the fascia
• Clear the fascia of soft tissue both anteriorly and posteriorly for a 3-4 cm healthy margin circumferentially around the entire defect
• Inspect the entire length of the incision for any additional (Swiss cheese) defects

STEP 4 - Adhesiolysis

• Free the anterior abdominal wall from all adhesions (bowel, omentum)
• Improves mobilisation and medialization of the abdominal wall muscles
• Dissect in planes other than intraperitoneal wherever possible to avoid visceral injury
• Remove any previously placed intraperitoneal mesh (reduces infection/fistulisation risk)
• After adhesiolysis, inspect the bowel for inadvertent injury and repair immediately if found
• Full enterolysis only if patient had preoperative bowel obstruction symptoms; otherwise anterior wall adhesiolysis alone suffices

STEP 5 - Sac Management

• Open the hernial sac
• Reduce all hernia contents back into the abdominal cavity
• Divide any internal adhesions
• Excise redundant sac as needed
• Place a large counted towel over viscera to protect them during subsequent repair steps

STEP 6 - Decision: Primary Closure vs Mesh vs Component Separation

STEP 7A - Primary Suture Repair (small defects only)

• Use 2-0 slowly resorbable monofilament suture (e.g. PDS) with 30-40 mm needle
• Small-bite technique (STITCH trial): 5 mm bites of fascia, 5 mm apart, running suture
• Suture length : wound length ratio ≥ 4:1
• For wide defects: interrupted figure-of-eight sutures - place loosely along entire wound first, then cinch together (distributes tension evenly)
• Incorporate fascia (linea alba) only - never include fat, muscle, or peritoneum in bites (causes ischaemia and breakdown)

STEP 7B - Mesh Repair (standard for most incisional hernias)

Choose Mesh Plane:

Mesh Technique:

1. Cut mesh to cover defect + ≥3-5 cm overlap of healthy fascia in all directions
2. Position mesh in chosen plane
3. Protect bowel from direct mesh contact (interpose omentum where possible)
4. Fix mesh with large nonabsorbable interrupted sutures distributed around the entire circumference
5. Close the fascia over the mesh (augment, do not bridge)

STEP 7C - Component Separation (if fascial closure under excessive tension)

Anterior Component Separation (Ramirez, 1990):

1. Raise skin/subcutaneous flaps off anterior rectus sheath to the linea semilunaris
2. Incise posterior rectus sheath just lateral to linea alba; separate rectus from posterior sheath
3. Incise external oblique aponeurosis just lateral to linea semilunaris from costal margin to iliac crest
4. Separate external oblique from internal oblique in the avascular intermuscular plane
5. Achieves 5-10 cm medialization per side

Transversus Abdominis Release (TAR - for larger defects):

• Additionally divide the posterior lamella of internal oblique and transversus abdominis muscle lateral to linea semilunaris
• Carry lateral dissection to retroperitoneum (border of psoas)
• Creates a large retromuscular space for wide mesh placement
• Achieves even greater medialization

STEP 8 - Drain Placement

• Closed suction drain placed in the subcutaneous space if large dead space remains
• Keep drain away from the mesh (proximity to mesh increases infection risk)
• Remove when output <30 mL/day

STEP 9 - Wound Closure

• Layered subcutaneous closure
• Skin closed with staples or running subcuticular suture

STEP 10 - Postoperative Care

• Abdominal binder - worn postoperatively to reduce seroma and support the repair
• Early ambulation
• No heavy lifting for 6-8 weeks
• Monitor for seroma (most common complication - usually self-resolves), wound infection, mesh infection
• Address modifiable risk factors for recurrence: weight loss, smoking cessation, glycaemic optimisation

Key Rules to Remember

1. Always open the full length of the scar - never assume a single defect
2. Mesh is the standard - suture-only repair has 30-50% recurrence; mesh reduces it to 10-24%
3. Mesh must augment, not bridge (bridging = mesh bulge = apparent recurrence)
4. Never incorporate fat or muscle in fascial bites - only the linea alba/fascia
5. Suture length : wound length ratio must always be ≥ 4:1
6. Drains always exit through separate stab incisions, never through the repair