# Abdominal Wall Reconstruction

## Introduction
Abdominal wall defects result from oncologic resection, hernia, trauma, infection, fascial dehiscence, and open abdomen management. Complex abdominal wall reconstruction addresses defects where primary fascial closure is not possible. Goals: restore abdominal wall continuity and dynamic function, prevent visceral eventration, provide durable soft tissue coverage. The plastic surgeon plays an essential role in collaboration with general and surgical oncology teams.

## Functional Anatomy of the Abdominal Wall
**Musculofascial layers** (lateral to medial): **External oblique**: fibers run superomedially to inferomedially ("hands in pockets" direction); aponeurosis forms anterior rectus sheath. **Internal oblique**: fibers run inferomedially to superomedially (perpendicular to external oblique); splits to contribute to both anterior and posterior rectus sheath above the arcuate line. **Transversus abdominis**: fibers run transversely; deepest lateral muscle; aponeurosis contributes to posterior rectus sheath above the arcuate line.

**Rectus abdominis**: paired vertical muscles from pubic symphysis to costal margin; enclosed in the rectus sheath. **Arcuate line (semicircular line of Douglas)**: located midway between the umbilicus and pubic symphysis; below this line, all aponeurotic layers pass anterior to the rectus, leaving only transversalis fascia posteriorly. **Linea alba**: midline fusion of bilateral rectus sheaths; site of midline (ventral) hernias. **Blood supply**: superior epigastric artery (from IMA), inferior epigastric artery (from external iliac), intercostal and lumbar perforators.

**Innervation**: intercostal nerves T7-T12 and L1; run between the internal oblique and transversus abdominis; must be preserved during component separation to maintain dynamic muscle function.

## Classification of Abdominal Wall Defects
**Location**: midline, lateral, supraumbilical, infraumbilical. **Size**: small (<5 cm), medium (5-10 cm), large (10-20 cm), massive (>20 cm). **Tissue quality**: clean vs. contaminated vs. infected; prior radiation; presence of mesh, stomas, or fistulae. **Loss of domain**: chronic hernia where abdominal contents reside outside the peritoneal cavity; reduction causes respiratory compromise and abdominal compartment syndrome.

## Preoperative Planning
**CT abdomen and pelvis**: defines hernia/defect size, mesh position, muscular anatomy, and loss of domain. Nutritional optimization (albumin >3.0 g/dL, prealbumin >15 mg/dL). Smoking cessation minimum 4 weeks preoperatively. Infection control: clear any active wound infection; staged approach if contaminated.

**Preoperative progressive pneumoperitoneum (PPP)**: Goni Moreno technique; serial insufflation of air into the peritoneal cavity over weeks to expand the abdominal cavity and accommodate reduced viscera; used for large loss-of-domain hernias. Botulinum toxin A injection into lateral abdominal wall musculature (200 units total): paralyzes muscles and allows medial advancement of the lateral abdominal wall; performed 4-6 weeks preoperatively.

## Surgical Techniques

### Primary Fascial Closure
Goal of all reconstructions when achievable. Direct suture repair appropriate for small, clean defects with healthy tissue. Mesh reinforcement recommended even with primary closure for defects >2 cm (reduces recurrence).

### Component Separation Technique (CST)

#### Anterior Component Separation (Ramirez Technique)
**Principle**: release the external oblique aponeurosis from the rectus sheath to allow bilateral medial advancement. Incision along the external oblique aponeurosis, 1-2 cm lateral to the lateral border of the rectus sheath. Release extends from the costal margin to the inguinal ligament. **Advancement achieved**: 3-5 cm at the epigastrium, 7-10 cm at the umbilicus, 1-3 cm at the suprapubic region (per side).

**Bilateral release** can achieve 10-20 cm of midline advancement. **Preserve perforating vessels**: lateral row of periumbilical perforators must not be divided. **Disadvantage of open technique**: requires large skin flaps with risk of wound complications (seroma, skin necrosis).

#### Endoscopic/Minimally Invasive Component Separation
External oblique released through small incisions using endoscopic visualization. Reduces wound complications by preserving skin perforators and avoiding large flaps. Same fascial advancement as open technique.

#### Posterior Component Separation (Transversus Abdominis Release — TAR)
**Novitsky technique**: incision through the posterior rectus sheath medially, then division of the transversus abdominis muscle. Enters the preperitoneal (retromuscular) space; allows wide retromuscular mesh placement. **Advantages**: preserves anterior abdominal wall blood supply and innervation, allows large mesh overlap in the retromuscular plane, lower wound complication rate than open anterior CST. **Advancement**: 8-12 cm per side at the umbilical level. Increasingly preferred over anterior CST for complex midline defects.

<image>Surgical illustration comparing anterior and posterior component separation techniques for abdominal wall reconstruction. The left panel shows an axial cross-section of the abdomen at the umbilical level demonstrating anterior component separation (Ramirez technique): the external oblique aponeurosis is released at a line 1-2 cm lateral to the rectus sheath, and arrows show the bilateral rectus-internal oblique complex advancing medially toward the midline. The skin and subcutaneous tissue are elevated off the external oblique as wide flaps. The right panel shows the same axial cross-section demonstrating posterior component separation (transversus abdominis release): the posterior rectus sheath is incised medially, and the transversus abdominis muscle is divided, opening into the preperitoneal space. Arrows show the rectus muscle complex advancing medially. A large piece of mesh is shown placed in the retromuscular-preperitoneal plane (behind the rectus muscles and in front of the peritoneum), extending laterally past the divided transversus abdominis into the preperitoneal space. Labels identify the rectus abdominis, external oblique, internal oblique, transversus abdominis, peritoneum, skin, subcutaneous fat, and mesh position in each technique.</image>

### Mesh Selection and Placement

#### Mesh Types

| Mesh Type | Examples | Best Use | Key Risk |
|-----------|---------|----------|----------|
| Synthetic permanent | Polypropylene (Prolene), Polyester (Parietex) | Clean fields; lowest recurrence | Infection, adhesions, fistula (if intraperitoneal without barrier) |
| Composite (barrier) | ePTFE-coated, absorbable-coated | Intraperitoneal placement | Cost; still carries infection risk |
| Biologic (ADM) | AlloDerm, Strattice, FlexHD | Contaminated/infected fields | Higher recurrence; stretch |
| Biosynthetic (absorbable) | Phasix, TIGR | Contaminated fields; bridge to healing | Complete resorption; recurrence |

**Synthetic permanent mesh**: polypropylene (Prolene), polyester (Parietex); strong, low recurrence; risk of infection, adhesions, fistula if placed intraperitoneally without barrier. **Composite mesh**: synthetic with antiadhesive barrier (ePTFE, absorbable coating) on visceral side; for intraperitoneal placement. **Biologic mesh**: acellular dermal matrix (AlloDerm, Strattice, FlexHD); used in contaminated or infected fields; may be cross-linked (more durable but less incorporated) or non-cross-linked (better incorporation but higher stretch/recurrence). **Biosynthetic mesh** (Phasix, TIGR): absorbable synthetic; provides temporary scaffold; useful in contaminated fields; eventual complete resorption.

#### Mesh Position

| Position | Location | Recurrence Rate | Key Consideration |
|----------|----------|----------------|-------------------|
| Onlay | Superficial to anterior rectus sheath | Highest | Easiest; highest wound complications |
| Inlay (bridging) | Spans fascial gap (no closure) | Highest | Avoid when possible |
| Sublay (retromuscular/Rives-Stoppa) | Between rectus muscle and posterior sheath | Lowest | Preferred position; protected from viscera |
| Underlay (preperitoneal/intraperitoneal) | Deep to musculature | Low | Requires barrier mesh if intraperitoneal |

**Onlay**: superficial to the anterior rectus sheath; easiest but highest recurrence rate; highest wound complication rate. **Inlay (bridging)**: mesh spans the fascial gap without fascial closure; highest recurrence; avoid when possible. **Sublay (retromuscular/Rives-Stoppa)**: between the rectus muscle and posterior rectus sheath; preferred position for most reconstructions; low recurrence, protected from viscera. **Underlay (preperitoneal/intraperitoneal)**: deep to the musculature; excellent overlap but risk of adhesions if intraperitoneal (requires barrier mesh).

### Tissue Flaps for Soft Tissue Coverage

#### Pedicled Flaps
**Bilateral advancement of abdominal wall components** (CST itself functions as a flap technique). **Rectus femoris flap**: pedicled superiorly on the lateral circumflex femoral artery; covers lower abdominal defects. **Tensor fasciae latae (TFL) flap**: pedicled on the ascending branch of the LCFA; reaches the lower abdomen and groin. **ALT flap (pedicled)**: if based on adequate pedicle length; covers lateral and lower abdominal defects.

#### Free Flaps
**ALT flap**: for large soft tissue deficits; recipient vessels are inferior epigastric or femoral vessels. **Tensor fasciae latae**: can provide fascial component for structural support. Indicated when local tissue is inadequate (radiation, multiple prior surgeries, massive tissue loss).

## Special Considerations

### Contaminated and Infected Fields
Avoid permanent synthetic mesh in contaminated (CDC wound class III-IV) settings. Use biologic mesh (AlloDerm, Strattice) or biosynthetic mesh (Phasix) as a bridge. Staged approach: initial debridement with wound VAC, followed by definitive reconstruction when wound is clean. Component separation without mesh in contaminated fields is acceptable if fascial closure is tension-free.

### Open Abdomen and Planned Ventral Hernia
Patients who cannot be closed after damage control laparotomy develop loss of domain. Sequential wound VAC changes (ABThera system) with progressive fascial reapproximation. If primary fascial closure cannot be achieved: skin-only closure or biologic mesh bridge → planned ventral hernia repair in 6-12 months. Definitive reconstruction with CST and mesh after recovery and nutritional optimization.

<image>Diagram showing mesh placement positions in abdominal wall reconstruction in a sagittal cross-section through the anterior abdominal wall. Four panels each show a different mesh position. Panel A shows onlay position with mesh placed superficial to the anterior rectus sheath and deep to the subcutaneous fat. Panel B shows sublay or retromuscular position with mesh placed between the rectus abdominis muscle anteriorly and the posterior rectus sheath posteriorly in the Rives-Stoppa space. Panel C shows preperitoneal or underlay position with mesh placed between the posterior rectus sheath and the peritoneum. Panel D shows intraperitoneal position with a composite mesh placed directly against the peritoneal surface with the barrier coating facing the viscera. Each panel labels the skin, subcutaneous fat, anterior rectus sheath, rectus abdominis muscle, posterior rectus sheath, peritoneum, and bowel. Arrows indicate the mesh position in each configuration.</image>

## Complications
**Recurrence**: 10-20% for CST with mesh; higher for bridging repairs; biologic mesh has higher recurrence than synthetic. **Wound complications**: seroma (30-40% for open anterior CST), surgical site infection (10-20%), skin flap necrosis. **Mesh infection**: may require partial or complete mesh removal; chronic mesh infection presents as draining sinus. **Enterocutaneous fistula**: from mesh erosion into bowel (especially intraperitoneal polypropylene without barrier).

**Abdominal compartment syndrome**: after reduction of large loss-of-domain hernias; monitor bladder pressures. **Chronic pain**: mesh-related or nerve entrapment; intercostal nerve preservation critical during CST. **Bulge without true hernia**: denervation of lateral abdominal muscles; common after open anterior CST.

## Key Clinical Pearls
Posterior component separation (TAR) has become the preferred technique for complex midline hernias because it preserves anterior abdominal wall blood supply, avoids large skin flaps, and provides an ideal retromuscular space for mesh placement with wide overlap. Preoperative botulinum toxin injection into the lateral abdominal wall muscles 4-6 weeks before surgery is a valuable adjunct for large defects; it allows 2-4 cm of additional medial advancement per side. Synthetic mesh should be avoided in contaminated or infected fields; biologic mesh or biosynthetic mesh is preferred, with the understanding that recurrence rates are higher and staged repair may be necessary. The retromuscular (sublay) position is the optimal mesh placement for most ventral hernia repairs; it provides excellent coverage, is protected from the viscera by the posterior sheath, and has the lowest recurrence rate. Always assess for loss of domain preoperatively with CT imaging; patients with significant loss of domain may benefit from preoperative progressive pneumoperitoneum to expand the abdominal cavity and prevent compartment syndrome after reduction.

## References
- Ramirez OM, Ruas E, Dellon AL. "Components separation" method for closure of abdominal-wall defects: an anatomic and clinical study. Plast Reconstr Surg. 1990;86(3):519-526.
- Novitsky YW, Elliott HL, Orenstein SB, Rosen MJ. Transversus abdominis muscle release: a novel approach to posterior component separation during complex abdominal wall reconstruction. Am J Surg. 2012;204(5):709-716.
- Rosen MJ, Bauer JJ, Harmaty M, et al. Multicenter, prospective, longitudinal study of the recurrence, surgical site infection, and quality of life after contaminated ventral hernia repair using biosynthetic absorbable mesh. Ann Surg. 2017;265(1):205-211.
- Ibarra-Hurtado TR, Nuno-Guzman CM, Echeagaray-Herrera JE, et al. Use of botulinum toxin type A before abdominal wall hernia repair. World J Surg. 2009;33(12):2553-2556.