International Journal of Surgery, Vol. 36, No. 12, Dec. 2009
Application of acellular dermal stromal mesh in the field of hernia surgery
Liu Chang Ji Yanchao
The application of artificial materials for hernia repair surgery has become the mainstream of the development of contemporary hernia surgery and has been accepted by the majority of surgeons [1], which basically meets the requirements of modern hernia surgery with "light postoperative pain, short recovery time, few complications and low recurrence rate", but complications such as postoperative infection, adhesions, and invasive intestinal fistula have become another prominent problem plaguing clinical practice. With the development of histology, materials science, bioengineering and other disciplines, acellular dermis matrices (ADM) has begun to be used as a biological mesh in hernia repair and has shown certain advantages.
1 Mechanism of ADM repair of soft tissues
The classification of ADM is divided into xenodermal matrix (xenoDen) and allogeneic dermal matrix (AlloDerm) according to the source of the prepared material. ADM is the application of tissue engineering technology, the dermal tissue is decellularized, the cellular components that cause rejection between allogeneic tissues are removed, and the extracellular matrix components such as collagen and elastic fibers are retained as soft tissue repair materials, and transplanted to the recipient site in the form of a "cell scaffold" to provide cells with a place and space for growth, induce and regulate cell growth, differentiation, and metabolism [2]. The soft tissue repair and healing process of ADM for defects and injuries is mainly completed through endogenous tissue regeneration.
The first is the rapid revascularization of ADM and the entry of host stem cells: because ADM does not have living cells and blood vessels, it is revascularized after transplantation on the wound because of its special composition and biological characteristics to induce rapid growth of recipient blood vessels, and circulating mesenchymal cell-like stem cells move into the transplanted tissue through the complete canal after vascularization, and begin the transformation of fibroblasts and re-enter the stroma. Takami et al. [3] transplanted ADM into the wound of full-thickness skin defect on the back of SD rats, and the formation of new vascularization in the matrix was seen after 2 weeks, and at the same time, the autologous fibroblasts were guided to grow in and begin to proliferate, and the inflammatory mediator response was mild and there was no obvious rejection. This revascularization and growth of autologous cells allows the acellular dermal matrix to become part of the autologous tissue, and allogeneic ADM can act as a scaffold for epidermal cell implantation and fibroblast and vascular endothelial cell growth during autologous skin grafting.
The second is collagen regeneration and dermal replacement: the physiological conversion rate of collagen is much lower than that of other proteins, and the implanted ADM participates in the metabolic process of collagen in the body. At this time, the cells are rapidly displaced to the entire transplant matrix, fibroblasts appear, and the transplant matrix is filled by the host cells, showing normal cell concentration, at this time, the autologous fibroblasts of the long human have enough time to secrete various autologous collagen and rebuild the dermis, and the proteins of the host cells filling the human matrix undergo a normal decomposition and regeneration process, carefully make a new matrix to become the regenerated host tissue, and restore to its origin structure, and finally form a new autologous dermis to replace the allogeneic dermis. In 1971, Gabbiani et al. [4] first reported the presence of a unique contractile cell derived from fibroblasts in rat wounds, which is myofibroblasts, which are associated with the contraction and scarring of granulation tissue. Experiments have shown that myofibroblasts appear in the first week of the larger wounds in pigs, peak at the end of the second week, and persist into the 12th week. Hickerson et al. [5] also showed that ADM increased energy and improved the survival rate of autologous epidermal grafts, while accelerating the regeneration of anchor fibers at the dermis-epidermal junction. Therefore, ADM may change the local environmental factors of the wound and improve the signal transduction of wound repair, and regulate the expression of cytokines and the growth and differentiation of cells.
2 ADM and abdominal hernia repair
ADM was first used as a skin substitute in patients with severe burns in 1992 and has since been widely used in burns, plastic surgery, oral surgery, neurosurgery, ophthalmology, otolaryngology and other disciplines. In recent years, a series of studies and clinical applications of ADM as a repair material for abdominal hernia repair have achieved good results. Harper[6] used ADM to repair abdominal wall defects, and showed that the density of cells and blood vessels in the ADM area was equivalent to that of the abdominal wall fascia at 8 months after surgery, and the boundary between the ADM and the surrounding fascia was no longer clear, and the collagen in the tissue was still tight and strong. l2 months after surgery, ADM has a thick collagen matrix, neatly arranged, and the distribution of cells and blood vessels is equivalent to that of normal fascia and different from scarring. Twenty-four months after surgery, ADM was completely fused with the surrounding tissues, and the collagen fibers naturally extended to the fibrous network of the surrounding fascia, and the elastin was no longer observable. In 8 patients with different types of abdominal hernia, acellular dermal stromal mesh was used for tension-free hernia repair, and after 3-6 months of follow-up, the patients felt natural, the incorporation was not tightened, and there was no local traction pain. During the follow-up period, the abdominal color ultrasound was rechecked, and the growth of the mesh was stable, and the surrounding normal tissues had healed each other, and the strength of the abdominal wall was significantly strengthened. While tension-free hernia repair with artificial mesh is widely used, complications such as foreign body sensation, local hard lump, and even infection, adhesion, and aggressive intestinal fistula after mesh treatment have not been well solved, and complex abdominal wall defects that are infected, contaminated or may be contaminated (including intestinal fistula with hernia, parastoma hernia, incarcerated hernia without intestinal necrosis or perforation, intestinal resection and recurrent incisional hernia during hernia repair, etc.) have also been difficult to treat hernia and abdominal wall surgery. Due to the rapid revascularization after implantation, phagocytic cells can quickly enter local tissues to increase the ability to resist infection, and form a layer of physical barrier locally to prevent tissue adhesion and pathological hyperplasia in the trauma area, so that different tissues can independently complete their healing process, reconstruct the normal anatomical relationship of local tissues, and complete defect repair through endogenous tissue regeneration, so that they can survive on the contaminated and infected wound without losing strength. It has certain advantages and is increasingly used in the repair of infected wounds or high-risk wounds [8-9]. Diaz et al. [10] conducted a multicenter retrospective study of 240 cases of complex abdominal wall hernias with different degrees of contamination of the gastrointestinal tract and bile ducts, and applied acellular dermal stromal mesh for one-stage repair, with an average repair defect area of 201 cm2 and an average postoperative follow-up of 317 days, and the repair effect was satisfactory, and the recurrence rate of hernia was 17.1%, which was significantly better than that of first-stage fascial closure repair. They concluded that acellular dermal stromal mesh provides a better option for primary repair of complex abdominal wall hernias. Patton et al. [11] retrospectively studied the use of acellular dermal matrix mesh to repair 67 patients with contaminated complex abdominal wall defects (incarcerated hernia, incisional hernia, abdominal wall injury, intestinal exposure, etc.), and the results were satisfactory. At an average follow-up of 10.6 months after surgery, the acellular dermal matrix mesh played a good anti-infection role in the contaminated area, and only 2 cases had the mesh removed due to severe early infection. Diaz et al. [12] used acellular dermal stromal mesh to repair 75 patients with abdominal wall defects with varying degrees of contamination, and the overall infection rate was 33.3% after postoperative follow-up (275±209) days, of which only 5 cases eventually needed to be removed from the mesh, and Ma et al. [13] used acellular dermal stromal mesh to repair the abdominal wall defect caused by actinomycosis in 1 case, and there was no incision infection or recurrence after 7 months of follow-up. These studies have shown that ADM has a strong anti-infective effect and is safe and effective even for the repair of complex and contaminated abdominal wall defects.
3 Advantages of ADM in hernia repair
It has the following advantages: (1) low cytotoxicity and low antigenicity: ADM has only mild cytotoxicity, no rejection and scarring, easy to crawl around the epithelium and fuse with the surrounding tissues, will not be rejected after transplantation, and can exist permanently in the host; (2) Cosmetic: ADM is well integrated with the surrounding tissues, without obvious difference, eliminating the "patch" phenomenon of the mesh; (3) Good tissue barrier effect and anti-infection ability: after ADM is implanted in the body, it can quickly vascularize and form a layer of physical barrier locally, prevent tissue adhesion and pathological hyperplasia in the trauma area, enable different tissues to complete their healing process independently, and reconstruct the normal anatomical relationship of local tissues; (4) Giving tissues sufficient strength and flexibility: It has been reported in the literature [14] that the maximum load of ADM can reach 144 N. The tensile strength after 9 months at the junction between ADM and fascia was 106.5 N; At the junction of the two ADMs, the tensile strength after 9 months was 149.1 N. Comparative studies showed that the tensile strength of ADM at the interface with fascia was significantly stronger than that of synthetic patches. (5) ADM has good flexibility, appropriate thickness, easy to trim, cut, overlap, roll into rolls, and can also choose products of different specifications according to the size of the wound, which is easy to operate and time-saving; (6) It has good histocompatibility and tissue-induced regeneration function, mild trauma, no chronic pain, local induration or discomfort, and has a good application prospect [15].
However, there are still many issues worthy of further research on acellular matrix patches, such as how to retain as many extracellular matrix components as possible while retaining as many extracellular matrix components as possible to maintain the structural integrity of the acellular matrix while removing the immune antigenicity that can cause rejection; How to control the porosity and degradation rate of decellularized matrix during the preparation of its decellularization matrix will be further studied in the future.
4 Key points of operation of acellular dermal matrix in hernia repair
Preoperative preparation: improve the general condition of the patient, control the factors of intra-abdominal hypertension before surgery, perform abdominal expansion and abdominal wall compliance exercises for patients with incisional hernia, and apply intravenous antibiotics prophylactically 1 hour before surgery. Key points of operation of inguinal oblique hernia: cut the aponeurosis of the external oblique muscle, free the spermatic cord, and protect the nerve from damage. The hernia sac was released to the neck of the hernia sac, the hernia sac was returned to the abdominal cavity, and the 5.5 cm × 10 cm acellular dermal matrix mesh patch was placed flat on the posterior wall of the inguinal canal, and the pores through which the spermatic cord passed were trimmed in the upper part of the mesh. The upper and lower ends of the mesh exceeded the medial annular orifice and pubic tuberosity by 3 cm, respectively, and the medial and lateral sides were fixed with the symphysis tendon and inguinal ligament, respectively. Ensure that the mesh coverage extends beyond the defect area and maintain slight tension so that the mesh fits tightly with the posterior wall tissue. Key points of operation of incisional hernia: enter the abdomen through the original incision, explore the retreat position of the hernia sac neck and the base of the abdominal wall in the abdominal cavity, and the size of the peritoneal built-in acellular dermal matrix mesh is 8 cm X 10 cm, so that the mesh is fully flattened, maintain moderate tension, and should exceed the actual defect edge by more than 5 cm, and fix it on the peritoneum and posterior fascia of the corresponding part with non-absorbable 2-0 polypropylene suture (polypropylene), indwelling negative pressure drainage in the front and lower part of the mesh, and poke the incision at the lowest position of the incursion. Compression bandaging of the abdominal bandage. Postoperative intravenous spot broad-spectrum antibiotics, pay attention to trauma, and routine abdominal ultrasound examination 3 days after surgery. For incisional hernias, abdominal tension is controlled with an abdominal band, and indwelling negative pressure drainage is used to prevent subcutaneous effusion.
Application precautions for acellular dermal matrix mesh: (1) Before use, the mesh should be soaked in sterile 0.9% sodium chloride solution for 2 times for 5 min each time; (2) When using, the mesh should be fully flattened and the appropriate tension should be maintained, and the mesh should be more than 5 cm beyond the actual defect edge; (3) When the edge is sutured, a non-absorbable 2-0 polypropylene suture (polypropylene) should be used for suture fixation; (4) At the same time, reasonable drainage should be carried out according to the size of the sac and the exudation of the wound.
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(Received:2009-08-19)