Giant Ventral Incisional Hernia: Abdominal Wall Function, Respiratory Performance and Quality of Life

Overall project aim

The present study examines the abdominal skeletal muscle and connective tissue of patients with giant ventral incisional hernia (VIH), and to evaluate the effect of a new endoscopic components separation technique (CST) with abdominal muscle replacement upon the muscular function of the abdominal wall and quality of life in patients. The study relies on the following hypotheses:

1. Collagen characteristics and organization are altered in patients with incisional hernia as compared with patients who do not develop incisional hernia.
2. Reconstruction of the linea alba by endoscopic CST and medialization of the abdominal rectus muscles in patients with giant VIH leads to improvement of daily function, respiratory performance and quality of life.
3. Abdominal wall reconstruction including CST with re-positioning of the rectus abdominis musculature increases the abdominal muscle mass and strength along with higher protein synthesis of the rectus muscles and a reduction of fibrotic skeletal muscle phenotype.

A total of 20 patients electively admitted for repair of a giant midline VIH, and 20 patients without hernias electively operated on for other indications are included. Exclusion criteria are pregnancy, severe heart- or lung disease, significant musculoskeletal disease, chemo- or radiotherapy within three months prior to the examination, and systemic corticosteroid medication. Oral and written informed consents are obtained from each participating patient.

Strength measurements of the m. rectus abdominis and the vastus lateralis of the quadriceps femoris muscle are done using a Good Strength muscle test system, both static and dynamic. The measurements are undertaken preoperatively and 1 year after surgery. A CT scan of the abdomen and thigh is done both 1 month before and 1 year after surgery to provide a detailed description of the hernia dimensions, the distance between the abdominal rectus muscles, and to determine the cross sectional area of the rectus abdominis and the vastus lateralis muscle. Lung function is determined by arterial blood gas, venous oxygen saturation, forced expiratory volume (FEV1), forced- and vital capacity (FVC, VC) including B2-receptor agonist reversal test, and maximum inspiratory- and expiratory pressure (MIP/MEP) preoperatively and 1 year postoperatively. Daily arterial blood gas is measured during postoperative admission. Lung function is determined at 1-month follow-up.

Quality of Life is assessed by the use of questionnaires. SF 36 is used for obtaining both mental and physical health scores. The St. George respiratory questionnaire and MRC are used to determine the level of daily lung impairment. Further, Carolina Comfort Scale assesses level of pain, movement limitation, and mesh sensation.

Protein turnover in both abdominal and thigh skeletal muscle is assessed by the use of a flood-primed continuous infusion of ring-13C6- phenylalanine. This will be infused four hours before surgery, and during this period 2-3 blood samples are drawn to verify stabilization of the isotope enrichment level prior to biopsy sampling. Muscle biopsy material is divided into fractions covering myofibrillar, sarcoplasmic and connective tissue proteins and analyzed using mass spectrometry to allow for calculation of protein synthesis of both contractile muscle protein and for muscle collagen. These procedures are repeated one year post surgery.

During surgery, biopsies of the linea alba, abdominal rectus muscle and the vastus lateralis muscle are taken using needle-biopsy equipment (Bergstrøm needle). One year after surgery the abdominal rectus muscle and vastus lateralis muscle again undergo the same biopsy procedure using a similar technique, but this time performed per-cutaneously under ultrasonographic guidance.

The biopsies are examined histologically for individual muscle fiber size and type (ATPase staining) as well as connective tissue and muscle structure (immunohistological examination collagen I, III and IV, laminin, desmin, tenascin-C). A section of the biopsy is used for mRNA expression by RT-PCR of COL1, COL3 and Tenascin-C. The content of collagen and both enzymatic and non-enzymatic cross-links (HP, LP and pentosidine) are determined by HPLC.

The linea alba connective tissue biopsy taken perioperative is investigated by electron microscopy for quantification of collagen fibril diameter, and atomic force microscopy to investigate fibril mechanics and 3-D structure of the connective tissue.

The change in abdominal flexor function and respiratory performance secondary to surgery is described in a paired design for both groups of patients. Quality of Life SF 36 and Carolina Comfort Scale are compared between the two groups of patients in an unpaired design and within patient groups in a paired design to assess any change induced by surgery. Differences between patient groups and change induced by surgery are assessed from the analyses on the harvested biopsy materials.