THE ABDOMINAL WALL: STRUCTURE & FUNCTION OF WOUND HEALING
Incision and closure of the abdominal wall is one of the most frequently performed; yet least discussed, of surgical procedures. Another often over looked topic is; understanding the rehabilitation process and post surgical care. Placing the power in the clients hands and arming them with the knowledge to self manage the healing process can significantly reduce movement dysfunction caused by scar tissue or change in posture habits and inactivity; as well as, a basic understanding of the timeline for wound healing and wound health.
The structural integrity of the anterior abdominal wall depends upon the rectus abdominis muscles, the muscles of the flank, and the conjoined tendons of the flank muscles that combine to form the rectus sheath. These terms, the anatomy and function were introduced in length in my last article. The rectus abdominis muscle is found on either side of the midline with the pyramidalis muscle lying superficial to the rectus muscle just above the pubis.
Factoring in connective tissue; we mentioned the rectus sheath also forms and intertwines with the superfiscial front line and the deep front lines of the fascia matrix. However, two notable structures are often overlooked when discussing abdominal wall surgery and post surgical care. They are the pyramidalis and the transversalis fasica.
One important muscular structure that is often not discussed in re training/ re patterning post-surgical rehabilitation is the pyramidalis.
The pyramidalis muscles arise from the pubic bones and insert into the linea alba in an area several centimeters above the symphysis pubis. Normally, the precise function of the pyramidalis muscle is unclear and considered to be of no value in the human structure. That is until abdominal incisions are made along the linea alba and near the umbilicus. The function this muscle acts to contact the linea alba, as well as stabilize the pelvis.
Therefore, if scar tissue or adhesion builds up, as it naturally will due to cutting through the abdominal wall and connective tissue, the innervation and nerve response could be diminished. In many patients, I have worked with I have seen Si joint dysfunction and low back pain that was not present prior to surgery. Something to consider in rehabilitation.
Deep to the muscular layers, and superficial to the peritoneum, lies a layer of fibrous tissue called the transversalis fascia, which lines the abdominal cavity. It is visible during abdominal incisions as the layer just underneath the rectus abdominis muscles.
It’s importance lies in the nature of it’s structure. The transversalis fascia in its entirety is second in importance perhaps only to the peritoneum as an encasing membrane of the abdominal contents. It acts to reinforce and stabilize the spine, as well as regulate intra abdominal pressure. Where function demands, it thickens and develops its strong elastic fibers to a protective perfection. When there are multiple incisions necessary for surgery, like a laparoscopic appendectomy this wall is perforated and comprised for several weeks to months. Tissue strength is a integral concern and factor in corrective rehabilitation; as well as wound healing.
Understanding the fundamental processes that are responsible for these functions is necessary to best create and close an abdominal incision and limit the risk of inflection, as well as to understand the complex process of healing post surgery.
Inflection is the first major risk; or failure of the healing process to synthesize adequate quantities of collagen to restore abdominal wall strength.
Psychoneuroimmunology (PNI): (Pyschological + Neurological + Immunology)
The wound-healing process is a balance between the amount of damage done to the tissue during an operation, and the ability of the body to decontaminate and repair its function.
With any incision, there is exposure of blood and platelets to connective tissue; which ultimately begins the inflammatory response that will sterilize and heal the wound. Psychoneuroimmunology (PNI) plays a critical role in both healing and immune function at the biological and biochemical levels. PNI is the study of the interaction between psychological processes, the nervous and immune systems of the human body. Recent work in psychoneuroimmunology (PNI) has demonstrated that stress delays wound healing; which is directly related to the pre and post surgical anxiety and nervousness a patient will ultimately feel.
Greater fear or distress prior to surgery is associated with a slower and more complicated postoperative recovery because anxiety presumably interferes with recuperation through both behavioral and physiological mechanisms. Seems logical enough.
Listening to mindful music for an hour every day can reduce chronic pain by up to 21% and depression by up to 25%, but I will leave that stat for another article.
Our body’s nature inflammatory response
During the initial phases of this process, the small vessels in the region of the injury become permeable to both molecular and cellular mediators of the inflammatory response. First, healing is under the direction of the inflammatory response, as this is essential to eliminating bacteria; as well as immunology. Every person has a unique biological and biochemical healing process; which should be taken into account.
After this initial phase, the polymorphonuclear neutrophils (PMNNs) and wandering tissue macrophages begin their work of digesting damaged tissue, killing bacteria, and synthesizing the chemotactic factors that direct wound repair. These cells lay the groundwork for the later appearance of the fibroblast that will reestablish wound strength.
The next critical factor in proper healing is the amount of necrotic tissue created. Actual repair must begin from healthy tissue. Healing must then begin from the uninjured tissue behind the area of damage.
Collagen & Tissue Strength
The re-establishment of abdominal wall strength depends upon the synthesis of new connective tissue. This is accomplished by fibroblasts and requires, not only the protein precursors for collagen synthesis, but also occurs most rapidly in a normally oxygenated environment where the enzymes and cofactors needed for collagen synthesis are present.
Collagen, the primary structural protein of the body, is synthesized by the fibroblast. It begins to appear in the wound on the second day, as an amorphous gel devoid of strength. Maximum collagen synthesis occurs around the fifth day. It depends especially upon the presence of oxygen, vitamin C, and amino acid precursors.
Maximum strength development does not occur for several months and depends upon the interconnection of the collagen subunits. Approximately 80% of original strength is reached in about 6 weeks; therefore it is recommended that light activity building up to moderate activity are only encouraged after 6 weeks and as long as there is no pain or discomfort.
It is important to recognize that perfusion of the wound is the most important factor in wound healing. Integrity of the microvasculature and flow is responsible for the oxygenation needed for cellular metabolism. Damage to tissue that impairs the delivery of oxygen to the wound increases the number of wound infections and the likelihood of herniation or infection. Which could complicate and impair movement quality in the future.
Empower the patient is first and foremost. Education each client on the complex healing process and concerns moving forward with post surgical care is crucial to not only the healing process but self management on behalf of the client. Understanding tissue strength and the body’s healing process from the inside out is of equal importance when re entering sport, play and or professionals that require manual labor.
- Milloy FJ, Anson BJ, McAfee DK: The rectus abdominus muscle and the epigastric arteries. Surg Gynecol Obstet 110: 293, 1960
- Cruse PJE, Ford R: The epidemiology of wound infection: A 10-year prospective study of 62,939 wounds. Surg Clin North Am 60: 27, 1980
- Cherney LS: A modified transverse incision for low abdominal operations. Surg Gynecol Obstet 72: 92, 1941
- Surgical anatomy of the transversus abdominis and transversalis fascia. Ann Surg. Jan 1971; 173(1): 1–5.