Surgical closure and securement products range from simple suture products through to sophisticated biomaterial aids for hemostasis, sealant activity, and for adhesion prevention. Within the hemostasis field, products have the objective of rapidly achieving hemostasis and acting to seal in the presence of high pressure blood flow or air flow.
Natural hemostats such as gelatin, collagen and thrombin were first developed as hemostatic agents, followed by mixes and fibrin sealants. More recently, companies have introduced synthetic sealants and hemostats that accelerate the process of blood clotting and provide a stronger seal that will withstand stronger pressures. These products employ various synthetic polymer chemistry systems. Glues are required to secure tissue firmly under substantial forces. In extreme cases such as musculoskeletal repair, these glues need to withstand high tension and pressure forces. Fibrin and other sealants are not strong enough for these applications and have been used as adjunctive to sutures and staples. Cyanoacrylate glues have sufficient strength for most procedures but are not yet cleared for use in the majority of internal applications due to toxicity concerns. They also lack sufficient flexibility for use in many procedures.
Efforts are progressing to develop new biomaterials capable of gluing tissues with high strength, low toxicity, and sufficient flexibility to avoid breakage of the bond. In addition, cyanoacrylate manufacturers are examining the possibility of improving cyanoacrylate technology to overcome the existing challenges of toxicity and brittleness. Despite this huge challenge, one or both of these two approaches are likely to establish new products in the next decade. In addition, the evidence of research work suggests it should be possible to create a glue technology that incorporates hemostatic properties to enhance the role of this technology even further.
Apart from fibrin-based sealants and cyanoacrylate-based high-strength glues, there are three other main categories of closure/attachment products in use or in development at present.
(For more information, see “Worldwide Surgical Sealants, Glues, Wound Closure and Anti-adhesion Markets, 2008-2015.”)
Historically, wounds have been treated with absorbent coverings designed to absorb the high levels of exudates produced from surgical, traumatic, or chronic wounds. These dressings delivered the benefit that they aesthetically covered up the sight of the wound, offered some absorptive capacity, and protected the wounds from getting dirty, offering some protection from infectious agents.
These dressings were based on fabric technologies of weaving and businesses developed based in textile manufacturing areas at the turn of the 19th century. Later, innovations in traditional dressings largely been focused on sterilization and then cost reduction and manufacturing, with some specific developments such as addition of radio-opaque material for x-ray visibility after surgery, and development of fabric production technologies such as non-woven techniques. Gauze has been traditionally used for absorption, packing, covering, and mechanical debridement of nonviable tissue. It has many disadvantages; it is difficult to keep moist, susceptible to linting, subject to fluid strike-through and invading environmental bacteria, and able to damage fragile granulation tissue if removed dry. Impregnated gauze products incorporate oils or petrolatum to provide for reduced adherence and easier removal, or to deliver antimicrobial agents to the wound surface. Synthetic fibers have also been developed to enhance absorption and to reduce costs.
The ideal wound dressing achieves a number of goals. It should cover the wound and control odor; be conformable, mimicking the elasticity and stretch characteristics of skin, and yet easy to apply to the wound. It is now recognized that ideal wound dressings should control the fluid level at the wound surface in moist wound healing conditions, while absorbing excess liquid exudates. Wound dressings should also exclude infectious agents, and disinfect pathological levels of infectious agents. These dressings should require to be changed as infrequently as possible without detriment to the wound healing process, and acceleration of wound healing without scar formation is an elusive goal. Clearly a number of wound dressings with different attributes are required to address the wide variety of wound types, symptoms and the variability within any single wound.
Several classification schemes have been invented with varying degrees of success in an attempt to organize dressings into manageable categories. These classification systems have been based on composition, such as films, foams, and hydrogels or function, such as contact layers, fillers, and absorbers.
The moist wound healing concept gave rise to a differentiation between semi-occlusive (advanced) dressings, and non-occlusive (traditional) dressings. Non-occlusive dressings allow all the moisture to escape from the surface of the wound. This will lead eventually to drying of the wound which slows healing and leads to trauma due to adherence of the dressing to the recovering tissue. These dressings can lead to the accumulation of excess liquid (exudates) at the wound surface, causing maceration of injured and healthy skin.
Semi-occlusive dressings were developed to manage the moisture level at the wound surface. These dressings are designed to absorb excess exudates, and to allow evaporation of water vapor from the outside surface. They are therefore designed to handle a lot of fluid without feeling at all wet on their outside surface. The combined benefits of absorption and water vapor transmission allow large quantities of exudates to be â€œmanagedâ€ without maceration, while maintaining the moist wound healing environment that is conducive to repair.
Both occlusive and semi-occlusive dressings provide a barrier to microbes and fluids. Totally occlusive wound dressings, however, do not allow the passage of water vapor or other gases, whereas semi-occlusive dressings allow varying amounts of water vapor, oxygen, and carbon dioxide to pass to and from the surrounding environment. Semi-occlusive dressings are compared by measuring the amount of moisture vapor they transmit over a 24-hour period from one square meter of dressing surface. The moisture vapor transmission rate (MVTR) of transparent films, for example, may vary from 500 gr/24h/m2 to well over 10,000 gr/24h/m2. Films are often combined with hydrogel to increase moisture levels for debridement or epithelialization phases. Lower MVTRs are suitable for wound healing, whereas higher MVTR products are used over intravenous catheters where they function to keep the skin and insertion site clean, free from microbes and dry, while allowing free diffusion of gases to the underlying skin.
Individual national markets differ in the extent to which the principles of moist wound healing have been adopted. In the U.K., pressure ulcer treatments rely on modern protocols, such as occlusive and non-occlusive dressings, whereas the Netherlands and Italy place greater reliance on non-occlusive products, such as simple gauze. Germany utilizes a variety of treatment regimes, including the entire spectrum of dressing types, which include occlusive, semi-occlusive, and non-occlusive dressings. In general, as markets develop, they adopt more sophisticated advanced wound care dressing technologies including hydrocolloids, composite foam dressings, hydrogels and film dressings. Market forces work to reduce the prices of these products, but health service procurement authorities still tend to inhibit adoption of these better treatments by budget cost containment measures.
Occlusive and semi-occlusive dressings have made significant inroads into the market for chronic wounds and wounds healed by secondary intention; however, non-occlusive products are used predominantly in surgical procedures. Gauze products are sold as dry presentations or as gauze impregnated with non-adherent substances.
While some companies and/or researchers are developing innovative new technologies for treating wounds (such as Uluru Inc. and its Altrazealâ„¢ Transforming Powder Dressing with Nanoflexâ„¢ Technology), the majority of products available fit into the following categories: film dressings, hydrocolloids, foam dressings, alginate dressings, hydrogels, nonadherent dressings, antimicrobial dressings, tissue-engineered products, pharmacological products, and physical treatments (such as negative pressure, positive pressure, mechanically assisted and others).