Component Separation Technique

Mark W. Clemens

Charles E. Butler

INTRODUCTION

Ventral hernias may follow laparotomy closures, tumor ablation, congenital anomalies, or trauma to the abdominal wall. Direct suture repair alone of ventral hernia defects results in an extremely high rate of recurrence. Primary fascial coaptation and mesh reinforcement of hernia defects are paramount tenets of abdominal wall reconstruction. No single advancement in surgical technique has made a greater impact on abdominal wall reconstruction outcomes than the development of component separation (CS) described by Ramirez and colleagues in 1990. In wide abdominal defects where fascial approximation is not possible under physiologic tension, CS with musculofascial advancement flaps is critically important to assist in fascial closure. CS maintains the strength and integrity of the abdominal wall while preserving innervated muscle function without tension. This chapter focuses on reliable and effective techniques of CS with an emphasis on patient diagnosis, planning, surgical technique, and complications.

INDICATIONS/CONTRAINDICATIONS

Indications for abdominal wall reconstruction are multifactorial and include tumor ablation, congenital anomalies, and trauma. Proposed risk factors for the development of hernias include tobacco use and a strong family history of hernia, which suggests a genetic predisposition. Studies have suggested that mechanical strain on load-bearing tissues can induce secondary changes in tissue fibroblast function that in turn can result in failure of abdominal wall repairs. The general indications for performing a CS of the abdominal wall include a deficiency of the abdominal wall fascia, which would require a bridged repair without fascial release. Clinical examples include large midline hernias, infected wounds with or without exposed mesh, and patients who have failed previous herniorrhaphy. CS is a fascial release of the external oblique fascia with creation of musculofascial advancement flaps. This procedure creates an autologous flap option for fascia coaptation, which is beneficial particularly in the presence of mesh reinforcement. Relative contraindications include lateral abdominal wall hernias in patients with ostomies directly in line with a planned CS. In these situations, a unilateral CS performed on the contralateral hemi-abdomen may be sufficient to achieve fascial coaptation. It is not possible to perform CS in patients who have lost the anatomy required for such a fascial release, such as complete loss of abdominal domain that can be seen in pancreatic fistulas or necrotizing soft-tissue infections of the anterior abdominal fascia. Radiated tissue is not an absolute contraindication but does have higher rates of wound dehiscence, infection, necrosis, and delayed wound healing. Patients with multiple previous abdominal wall surgeries or unclear reconstructive surgical history and anatomy should be approached cautiously. Violation of the rectus complex such as with elevation of a transverse rectus abdominis muscle flap or vertical rectus abdominis muscle flap does not preclude the use of CS.

PREOPERATIVE PLANNING

Physical examination should be performed to assess the patient’s general condition, the abdominal wall integrity, the extent and location of any abdominal wall abnormalities, and the presence of scars that could become an obstacle to raising reliable tissue flaps. Routine laboratory tests and
a nutritional assessment are advised. Correct diagnosis of abdominal wall defects is critical to proper management. Preoperative computed tomography (CT) to examine the defect characteristics, abdominal wall anatomy, and vascularity is helpful for surgical planning. CT scans allow for visualization of intra-abdominal organs, and the abdominal wall, three-dimensional data sets, and multiplanar reformation capabilities. CT scans may assist in detecting fluid collections, bowel obstruction, incarceration, strangulation, and traumatic wall hernias. Magnetic resonance imaging also permits the detection of soft tissue defects and abdominal wall hernias, although this modality does not usually offer further sensitivity and therefore may be cost prohibitive. Thromboprophylaxis should be administered on the basis of a patient’s particular risk for a thrombosis as evaluated by the Caprini risk assessment tool. Prospective randomized controlled data is unavailable regarding routine antibiotic prophylaxis. Most centers including ours regularly prescribe prophylactic antibiotics intraoperatively for all patients. Bowel preps may be beneficial in patients with anticipated violation of the gastrointestinal tract.

SURGERY

Preoperative/Markings

Patients should be marked in the preoperative holding area, ideally in both recombinant and supine positions for complete evaluation of abdominal wall defects. The pertinent landmarks of the abdominal wall and are recounted. Markings may delineate anatomic boundaries such as the pelvis, midline, and costal margin as well as the fascial extent of any intra-abdominal defects. Once the patient is transported to the operating room, he or she is placed supine on the operating table, sedated, and intubated. Intraoperative intravenous antibiotic component prophylaxis is initiated. The abdomen is widely draped and prepped to expose the patient’s flanks and from the pelvis to the mid-sternal area. Patients should receive sequential compression devices for deep vein thrombosis prophylaxis. Patients requiring greater exposure should have room temperatures maintained above 75°F to minimize postoperative infections.

Surgical Technique

Critically important to a hernia repair is the reestablishment of the abdominal domain integrity with complete spacial coaptation. All attempts should be made to avoid a bridged mesh repair because there is a clear trend toward higher recurrence rates compared with when the fascia can be reapproximated over a mesh repair. Understanding all of the approaches for abdominal wall reconstruction and particularly myofascial advancement flaps is critically important to determine the least invasive procedure to provide a long-lasting repair with an excellent functional outcome for the patient. Ramirez and colleagues’ description of the surgical technique of CS facilitates medialization of the rectus musculofascia and midline abdominal closure, by releasing the external oblique aponeurosis and posterior rectus sheath bilaterally (Fig. 68-1). Although CS will often allow for midline fascial reapproximation, which is the optimal situation, occasionally this will not be possible for larger hernias. As a result, the myofascial edges will need to be bridged with mesh. Defect size reduction, especially if less than 150 cm², will lead to the lowest recurrence rates. There are several other theoretical advantages to reapproximating the linea alba. If one considers the linea alba as the tendinous insertion of the rectus and oblique muscles and borrows from the concepts of tendon repair, then it seems logical that the physiologic tension of the abdominal wall should be restored during ventral incisional hernia repair. Although every attempt to reestablish the midline is advisable, accomplishing that goal is not always feasible, and not all patients can tolerate the intraperitoneal compression required. This can result in intraperitoneal hypertension, pulmonary compromise, or abdominal compartment syndrome. Once the mesh is inserted peripherally the midline fascia will be reapproximated, and the mesh and its inset will bear the majority of the tension.

Open Component Separation

Myofascial advancement techniques, or CS, take advantage of the laminar nature of the abdominal wall and the ability to release one muscular or fascial layer to enable medial advancement of another. The lateral abdominal compartment can be released by open or minimally invasive CS. A minimally invasive CS can be performed in various ways, but all of the techniques (to a certain degree) maintain the blood supply to the skin from the underlying rectus abdominis muscles. In contrast, an open CS is
performed by raising large subcutaneous flaps to expose the external oblique fascia (Fig. 68-1). The cutaneous perforators emerging from the anterior rectus sheath are ligated and divided to facilitate exposure of the linea semilunaris in its entirety. These flaps are carried laterally past the linea semilunaris. This subcutaneous dissection itself can provide some medial advancement of the abdominal wall skin. An anatomically precise external oblique aponeurotomy is made 1-2 cm lateral to the linea semilunaris on the lateral aspect of the external oblique aponeurosis from several centimeters above the costal margin to the pubis. It is important to confirm that the incision is not carried through the linea semilunaris because this would result in a full-thickness defect of the lateral abdominal wall, which is very challenging to repair. The external oblique aponeurosis is then bluntly separated in the avascular plane away from the internal oblique aponeurosis to the midaxillary line, allowing the internal oblique and transversus abdominis muscles with the rectus abdominis muscle or fascia to advance medially as a unit. These techniques, when bilaterally performed, can yield up to 20 cm of mobilization in the mid-abdomen.

FIGURE 68-1 Open component separation. Subcutaneous flaps are elevated off the anterior rectus sheath to expose the external oblique aponeurosis. The external oblique aponeurosis is released from the inguinal ligament inferiorly to above the costal margin superiorly. This allows exposure of the internal oblique muscle fibers once the external aponeurosis is incised. (Adapted with permission from, Rosen MJ. Atlas of Abdominal Wall Reconstruction. Elsevier, 2011.)

Once the mesh insertion and fascial closure are performed, the subcutaneous skin flaps are advanced and closed at the midline. To reduce subcutaneous dead space, interrupted quilting sutures should be placed between the Scarpa fascia and musculofascial repair. This technique also decreases shear stress, which is thought to contribute to postoperative seroma formation, and decrease the total drain output, allowing the surgeon to place fewer drains and leave them in for a shorter period. After paramedian skin perfusion is critically assessed, a vertical panniculectomy may be performed so that the skin is reapproximated in the midline without redundancy.

A major limitation of open CS is the wound morbidity associated with the large skin flaps necessary to access the lateral abdominal wall. To avoid this morbidity, several manuscripts have described innovative minimally invasive approaches to CS. These approaches are designed to gain direct access to the lateral abdominal wall without creating large skin flaps, creating dead space, or interrupting
the primary blood supply to the central abdominal skin by ligation of the rectus abdominis perforator vessels.

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