Incisions in Hepatobiliopancreatic Surgery: Surgical Anatomy and its Influence to Open and Close the Abdomen
Executive Summary
Hepatobiliopancreatic (HPB) surgery requires complex abdominal incisions that often compromise the muscular, vascular, and nervous integrity of the abdominal wall. The incidence of incisional hernia (IH) following these procedures remains high, with reported rates ranging from 7.7% to 38.8%. While midline incisions are common in general surgery, HPB procedures frequently utilize subcostal, transverse, or hybrid (e.g., J-shaped or Mercedes-Benz) incisions to gain adequate exposure to the upper abdomen.
Critical findings from current clinical literature indicate that IH formation and muscle bulging—resulting from denervation and subsequent atrophy—are significant long-term complications. Prevention is paramount, as these defects are complex to repair and substantially impair patient quality of life. Key preventative strategies include:
Anatomical Fidelity: Minimizing lateral extensions to preserve intercostal nerves and maintaining a distance of at least 2–3 cm from the costal margin.
Closure Technique: Utilizing multilayered suturing and the "small bites" technique (5–9 mm bites, 5 mm apart) to achieve a suture-to-wound length ratio of 4:1.
Prophylactic Intervention: Implementing prophylactic mesh in high-risk patients, which has demonstrated a reduction in IH incidence from approximately 17–19% to under 4% in comparative cohorts.
Surgical Anatomy of the Abdominal Wall
The functionality of the abdominal wall depends on the coordination of several overlapping muscular layers and a rich neurovascular supply.
Muscular Composition
The anterior abdominal wall is categorized into two primary groups:
Midline Group: Comprising the rectus abdominis (RM) and the pyramidalis muscle. The RM inserts into the xiphoid process and the 5th–7th costal cartilages.
Anterolateral Group: Comprising the external oblique muscle (EOM), internal oblique muscle (IOM), and transversus abdominis (TA).
The EOM aponeurosis forms the main component of the anterior rectus sheath.
The IOM divides into anterior and posterior lamellas; the posterior lamella contributes to the posterior rectus sheath.
The TA fibers run horizontally, and its myoaponeurotic limit is the linea semilunaris.
Neurovascular Supply
The space between the TA and IOM contains the branches of the intercostal nerves. Subcostal incisions systematically sever branches of the 7th, 8th, and 9th (and occasionally 10th) intercostal nerves. Lateral extensions may further injure the 11th and 12th nerves, which are critical contributors to the innervation of the anterior abdominal wall. Damage to these nerves results in motor impairment, leading to ipsilateral rectus muscle and TA atrophy.
Classification and Impact of HPB Incisions
Long-Term Consequences
Incisional Hernia (IH): A defect in the musculoaponeurotic layers caused by factors such as obesity, infection, or inadequate closure.
Bulging: A protrusion in the surgical scar without a fascial defect, occurring specifically due to nerve injury leading to muscle denervation and atrophy.
Incidence and Risk Factors for Incisional Hernia
The incidence of IH varies significantly by incision type and patient profile. Retrospective reviews suggest that the midline component of hybrid incisions carries the highest risk of failure, accounting for roughly 40.3% of IH cases in some cohorts.
Documented Risk Factors
Patient Metrics: BMI > 26.0 kg/m², height > 167.5 cm, and age ≥ 65 years.
Comorbidities: Diabetes mellitus, malnutrition (albumin < 3.5 g/dL), anemia, smoking, and the presence of ascites or cirrhosis.
Anatomical Markers: Subcutaneous fat thickness > 23.3 mm, perirenal fat pad > 14.7 mm, and high levels of intramuscular adipose tissue.
Surgical Factors: Surgical site infection (SSI), previous IH, and the use of specific hybrid incisions (Mercedes-Benz and Reverse-T).
Optimal Closure Techniques
Effective closure is essential for wound healing and IH prevention. Current literature suggests several technical recommendations:
Multilayered Closure: The document recommends a multilayered approach. For lateral incisions, this may involve a two-layer protocol:
Layer 1: Internal oblique muscle, transversus abdominis, and the posterior rectus sheath.
Layer 2: External oblique muscle, its fascia, and the anterior rectus sheath.
Small Bites Technique: In accordance with European Hernia Society guidelines, closure should utilize a continuous small-bites technique with slowly absorbable 2-0 suture. Bites should be 5–9 mm from the edge and 5 mm apart to achieve a 4:1 suture-to-wound ratio.
Hemostasis: Careful control of the superior epigastric artery and its branches is required during the division of the rectus muscle to prevent hematoma formation.
Prophylactic Mesh Implementation
Evidence supports the safety and efficacy of prophylactic mesh in high-risk HPB surgery patients. Comparative studies have shown:
Subcostal Laparotomies: IH incidence was reduced to 1.72% in mesh groups compared to 17.54% in primary suture groups.
Emergency Subcostal Incisions: Onlay mesh reinforcement reduced IH rates to 3.8%, compared to 19.1% with suture only.
Safety Profile: These studies reported no significant increase in surgical site infections, morbidity, or mortality associated with mesh placement.
Common placement strategies involve positioning the mesh in the space between the internal and external oblique muscles, extending retromuscularly over the posterior rectus sheath when moving medially.
