DISCUSSION
Wound healing occurs through inflammation, proliferation, and maturation phases. The hemostasis phase occurs within about 10–15 minutes after the wound occurs and is often included in the inflammatory phase. Upon the initial tissue damage, the damaged blood vessels contract, causing the platelet aggregation and coagulation cascade activation to produce a platelet plug. The platelet plug is a physiological barrier that prevents bleeding, bacterial infection, and water loss that serves as a provisional matrix. The cells in the platelet plug contain a variety of growth factors that induce the influx of inflammatory cells into the wound site and activate fibroblasts, vascular endothelial cells, and macrophages to begin the inflammatory phase. Platelets increase vascular permeability through serotonin. Neutrophils are the first white blood cells to enter the wound, and their values peak within 24 hours. They cause acute inflammation and play an immunological role in preventing bacterial contamination and infection. They also secret protease to remove damaged ECM and tissue. Next, monocytes enter, are activated and converted to macrophages, and act as the major cells that destroy foreign bodies or bacteria within 48–72 hours. They secrete several growth factors and offer phagocytosis, which induces ECM formation and the proliferation of fibroblasts, vascular smooth muscle cells, and vascular endothelial cells. Finally, lymphocytes appear after 72 hours. When the wound exits the inflammatory phase, the next proliferation phase begins. As macrophage numbers decrease, fibroblasts, vascular endothelial cells, and keratinocytes are produced and secrete growth factors. These growth factors stimulate ECM production and neovascularization. The proliferative phase consists of epithelialization, ECM deposition, vascularization, and wound contraction. In the maturation phase, mature scars are formed by collagen reconstruction through structural modifications [
5-
7]. If the inflammatory phase persists without timely and orderly progression, wound healing may become delayed or severe scarring may occur, and the wound can become chronic, presenting clinical problems and frequently causing morbidity and mortality [
6,
8].
Wound healing is a dynamic process that is difficult to distinguish clearly and requires consistent measurements. Wound healing is usually assessed by clinical features and biochemical and histological parameters [
6]. Histological evaluations should include the basic components of the healing process, including angiogenesis (neovascularization), inflammation (inflammatory cell infiltration), fibroplasia and restoration of the connective tissue matrix (collagen deposition), wound contraction and remodeling, epithelialization, and differentiation [
5,
6,
8]. A quantitative scoring system is highly specific and standardized; however, in most cases, it is difficult to use because it is a difficult to objectify the exact interval between two values. Therefore, in biochemical research, semi-quantitative scoring systems are widely used to measure and express the degree of change between scales [
6]. In this study, a comparative study using semiquantitative scoring system was also conducted.
Methods of hemostasis include: mechanical techniques (compression, suture, ligation, etc.); thermal techniques (electrocautery, laser, etc.); and chemical techniques (pharmacotherapy–hypotensive anesthesia, epinephrine, vitamin K, desmopressin/topical hemostatic–collagen, cellulose, gelatin, thrombin, fibrin sealant, etc.) [
1]. Of these methods, topical hemostatic agents are used when other methods are impractical [
2]. Ideally, topical hemostatic agents should be easy to use; quickly and effectively achieve hemostasis; and be nonantigenic, fully absorbable, and inexpensive. However, such hemostatic agents do not exist. Therefore, surgeons must be aware of the mechanisms, advantages, and disadvantages of various topical hemostatic agents to ensure their appropriate use [
1,
9]. Samudrala [
1] classified topical hemostatic agents as follows according to their mechanism of action: active (collagen, cellulose, gelatin, etc.); passive (thrombin, etc.); or tissue sealant (fibrin sealant, polyethylene glycol, albumin/glue, etc.). Achneck et al. [
9] classified topical hemostatic agents according to their components as: physical (bone wax, ostene, etc.); absorbable (gelatin, oxidized cellulose, microfibrillar collagen, etc.); biologic (thrombin, fibrin sealant, platelet sealant, etc.); and synthetic (polyethylene glycol hydrogels, cyanoacrylates, glutaraldehyde cross-linked albumin, etc.). The mechanism, advantages, and disadvantages of clinically frequently used hemostatic agents are summarized in
Table 4 [
1,
3,
9]. Topical hemostatic agents do not adhere strongly to wet tissues and have little effect on actively bleeding wounds. And, their dissolution does not indicate their disappearance from the site of application. Although hemostatic agents are dissolved in a short period of time, the absorption of their residue and wound healing involve another process. Surgeons believe that it will be absorbed immediately, but it may remain unabsorbed depending on environmental factors, so it is preferable to use the minimum amount needed. In addition, topical hemostatic agents may increase infection, so minimal amounts should be used in cases of a risk of contamination [
2]. Surgicel Fibrillar used in this experiment is very loose and relatively thicker (>5 mm) than the original. Surgicel Snow is thick, tightly woven, and denser than Surgicel Fibrillar [
10].
Surgicel consists of uronic acid components and fibrous residue. This fibrous residue is processed by macrophages and is not associated with foreign body giant cell, so it has low antigenicity. In addition, it has fibrin affinity with hemostatic potential and acts as a scaffold for fibrin deposition and clot formation [
11]. Above all, it is widely used because of its low cost and easy application, and it is known to take 2–6 weeks to be absorbed [
2,
12]. Surgicel inhibits bacterial growth by preventing the influx of sodium hydroxide and lowering the pH to about 2.5 [
13]. Surgicel is effective against a broad spectrum of bacteria and antibiotic-resistant bacteria, and since bacteria have a growth limit at pH 4.4–4.9, it does not act on the mechanism itself like antibiotics do [
10]. However, lowering the pH reportedly causes strong inflammatory reactions and delays wound healing [
2,
12,
14].
The Tachosil used in this experiment is an absorbable fibrin sealant patch that consists of a combination of fibrin sealant (tissue sealant) and collagen (passive hemostatic agent) [
1,
3]. Tachosil is absorbed within about 12 weeks and reportedly reduces scar formation and adhesions [
3]. The fibrin sealant is composed of human fibrinogen, human thrombin, Ca
2+, and factor XIII; dissolved fibrinogen and thrombin contact the fluid and act at the end of the coagulation cascade. Thrombin cleaves fibrinogen into fibrin monomers and activates factor XIII to factor XIIIa together with Ca
2+. Fibrin monomers form unstable and soluble fibrin polymers, which are then cross-linked by factor XIIIa to become stable and insoluble fibrin polymers, resulting in fibrin clots [
3,
9,
15]. Fibrin regulates the inflammatory phase by regulating monocyte and macrophage activity as well as hemostasis in the wound healing process. It also acts as a growth factor, directly affecting angiogenesis and promoting fibroblast formation. Through this action, it has a good effect on wound healing [
7]. Tachosil has the advantages of hemostasis, providing tissue sealing, supporting sutures, preventing adhesions, protecting nerves, slowly releasing medications, and promoting wound healing, and is clinically used for hemostasis, adherence purposes during skin grafting, nerve anastomosis, bone sealing, dura sealing, and mastectomy to reduce seroma formation, slowly releasing medications, including antibiotics, growth factors, and chemotherapeutic agents [
3,
15-
17]. However, if a contaminated or infected area or active infections are present, its use should be avoided. There are also problems with immunologic reactions and the transmission of infectious disease (human immunodeficiency virus, hepatitis, parvovirus B19, and Creutzfeldt-Jakob disease) [
3,
15,
17]. As a solution, viral inactivation using nanofiltration, heat treatment, solvent detergent cleansing, autologous donation techniques, and recombination production methods are used [
17].
In this study, although the data values were not statistically significant, differences in each group were observed on histological evaluation. The Surgicel and Tachosil groups showed an increase in all parameters compared to the control group. Each increased inflammation as a foreign body but did not significantly interfere with the wound healing process. The increase in foreign body giant cell and inflammatory cell infiltration in the Surgicel group is thought to be due to low pH; in contrast, Tachosil induces a less serious foreign body reaction. In the Tachosil group, the initial ECM formation amount was higher than that of other groups, but it is difficult to distinguish the newly generated amount accurately because it is mixed with collagen in the product components. As the product components were absorbed later, the amount of ECM formation was similar in all groups. However, due to the fibrin action seen in the Tachosil group, the wound healing proceeded faster than in the other groups. The authors believe that this study was not statistically significant at below 5%. But, considering that it is a significant value below 10%, it is expected that statistically significant results will be obtained if the number of samples increases.
In conclusion, we recommend the use of Tachosil because it features a less severe foreign body reaction than Surgicel and facilitates faster wound healing due to the fibrin action.