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Fractures, soft tissue injuries and degenerative diseases caused by various car accidents, falls from height and other causes are more common in orthopedics, and surgery is often a common treatment for these diseases.
Incision infection is a common complication after orthopedic surgery, and its influencing factors are complex, such as: poor nutritional status of patients, irregular sterile operation during doctors' surgery or wound replacement drugs and dressings, and failure of nurses and family members to do a good job in ward hygiene.
So far, there is still a lack of consensus on the definition of surgical incision infection, and most trauma literature usually cites the definition in the Centers for Disease Control (CDC) guidelines for surgical site infection (SSI), that is, infection that occurs at the surgical incision site, which is divided into superficial incision infection, incision deep infection, and organ/space infection.
According to the diagnostic criteria for surgical incision infection in the "Diagnostic Standards for Hospital Infection (Trial)" issued by the Ministry of Health of the mainland in 2001, at least one of the following conditions is required to diagnose postoperative incision infection: (1) redness, swelling, heat, pain and other manifestations or purulent discharge at the incision site;
(2) Purulent discharge or fever at the incision site and deep part≥ 38 °C, local pain or tenderness; (3) Redness, swelling, heat, pain and other manifestations appeared at the incision site, and the secretion culture results showed positive infection of pathogenic bacteria.
After the patient has postoperative incision infection, there will be redness, swelling, heat, pain and other typical symptoms of inflammatory reaction, and can not be relieved for a long time, because fracture surgery is mostly open injury, wound contamination is serious and soft tissue conditions are poor, resulting in a high postoperative infection rate, surgical treatment effect is not ideal.
After infection, it is often difficult to heal wounds, prolonged hospital stay, and increased economic burden, and if the patient's infected wounds cannot be controlled in a timely and effective manner, it may develop into osteomyelitis and even cause loss of limbs or life.
Therefore, for orthopedic surgical wounds with infection, timely and thorough debridement should be carried out, necrotic tissues and secretions should be removed outside the body, and at the same time ensure smooth drainage of the wound drainage tube, and then decide to suture the wound or free skin grafting and flap transfer to repair the wound when the patient's general condition is good, the infection at the wound can be effectively controlled, and the granulation tissue growth is fresh.
And change the dressing on time to avoid worsening the infection and affecting the patient's wound healing. The traditional treatment method is effective for patients with superficial wounds and good general condition, and the wound can achieve complete healing in a short time.
For those patients with long duration of infection, other diseases, and poor nutritional status, the requirements of complete debridement cannot be met, and the growth of granulation tissue is slow due to the presence of necrotic tissue and toxic decomposition products during treatment, which is not conducive to suture or skin grafting, and it takes a long time for the wound to heal.
In the process of disease development, it may also cause or aggravate soft tissue, bone, tendon necrosis, affecting the recovery of patients, and infected wounds need long-term, frequent dressing changes, the need for various dressings and systemic or local anti-infection treatment, not only increase the economic burden of patients, but also bring patients physical pain and the opportunity of nosocomial infection, so more efficient infection wound treatment measures should be found.
Research progress of negative pressure occlusion drainage in wound treatment
Overview and how it works
VSD is an evolution of Negative pressure wound therapy (NPWT), a systematic physical wound treatment method developed in the 90s of the 20th century, which consists of four main parts: (1) wound filling dressing; (2) semi-permeable film; (3) drainage tube; (4) Vacuum system.
VSD uses a dressing and a semi-permeable film as an intermediary to separate the outside from the wound, so that the necrotic tissue and secretions generated by the wound are discharged through the drainage tube into the negative pressure drainage bottle in the vacuum system. This can effectively reduce the invasion of toxic substances in the wound exudate, so as not to cause further damage to the body.
The following describes the mechanism of its healing effect on wounds:
(1) Increase wound blood supply and improve wound microcirculation VSD passively pulls capillaries through the mechanical traction force generated by negative pressure in the wound, so that the level of tissue cells is extended and deformed, and the resulting cell deformation leads to changes in cell proliferation, migration and differentiation functions.
Cell deformation and associated cell stretching induce cell proliferation, thereby promoting wound healing. For wounds with edema, traction can reduce vascular permeability, thereby alleviating edema around the wound, and have a beneficial effect on the formation of fresh granulation tissue and capillaries.
In addition, the wound edge is contracted by foam and the foam comes into contact with it, and at the wound interface, the foam produces micro-deformation, stretches the cells, and activates angiogenesis and cell division. It has been proposed that a temporary decrease in blood flow at the wound margin leads to transient hypoxia, which stimulates angiogenesis through the hypoxia-inducible factor-1α-VEGF (vascular endothelial growth factor) pathway.
There is evidence that short (6 h) intermittent application of VSD in mouse models of diabetes resulted in prolonged proliferating cell response and increased expression of Ki-67 (a cell proliferation marker).
(2) Inhibit bacterial growth and control infection In the VSD system, semi-permeable membrane is very effective in preventing the wound from being invaded by bacteria in the external environment and preventing cross-infection, which isolates the wound from the external environment, making the open wound become a relatively closed wound;
The formation of bacterial culture medium is reduced by timely drainage of necrotic tissue and secretions of the wound by negative pressure. Some studies have shown that one study observed that the number of bacteria in the wound decreased from an initial 1.00×10 8/g to 1.00×10 4/g by day 5 when no antibiotics were used when wounds were treated without antibiotics and only with negative pressure.
(3) Promote the growth of cells and granulation tissues, and the growth of granulation tissue in wounds mainly relies on the proliferation of new capillaries, fibroblasts and their synthesis of secreted collagen. Macrophages promote endothelial cell proliferation by secreting VEGF.
The VSD system drains out toxic substances from the wound through negative pressure, promotes blood flow, reduces the diffusion distance of oxygen and nutrients, and promotes the smooth healing process of the wound. The mechanical traction produced by negative pressure therapy can promote the multiplication of fibroblasts, which in turn promotes the synthesis of collagen by cells, thereby accelerating the healing of chronic wounds.
Through the role of VSD, granulation and vascularization of wound local tissues can improve the healing environment, specifically VSD can reduce tissue edema, reduce inflammation, and clear wound exudate, so as to exchange beneficial substances into local wound tissues and perfuse tissues.
Progress in clinical application
In 1993, Wim Fleischmann first introduced traditional negative pressure drainage combined with modern wound dressings to treat wounds, a treatment modality that came to be known as VSD. First of all, it was applied to draining limb wounds, and the clinical effect was remarkable. Professor Qiu Huade first introduced NPWT technology to China in 1994 and explored it clinically.
In recent years, NPWT has been widely used in the treatment of acute and chronic wounds in different departments, such as general surgery, orthopedics and burns. Studies have shown that NPWT can effectively promote wound healing by controlling wound infection and inflammation, removing wound exudate, reducing tissue edema, promoting granulation tissue formation, angiogenesis and blood perfusion.
In 1995, the technology was approved for use by the Food and Drug Administration (FDA). The most widely used variant of NPWT is the vacuum-assisted closure (VAC) technique, introduced in North America in 1997 by American surgeons Argenta and Morykwas.
Using porous polyurethane foam as a wound dressing, a pressure below atmospheric pressure is applied to the wound surface, which is sealed by a film dressing and connected to a negative pressure pump and drainage collection system through a drainage tube. NPWT is gaining popularity as a way to reduce the number of dressing changes and is convenient for bedside applications, and has been widely recognized to shorten wound duration.
Although NPWT is widely used in clinical practice, there are some problems that hinder its further development: (1) drainage tube blockage: For wounds with excessive viscous secretions similar to wound infection, wound exudate, bleeding and necrotic tissue are easily deposited in the tube, resulting in tube obstruction and negative pressure failure;
(2) Topical medication restriction: the wound is closed by a semi-permeable film during the healing process, which hinders the application of topical drugs, such as anti-infective drugs or growth factor solutions, which may affect wound healing; (3) Infection: Although NPWT has oxygen-suppressing functions by creating hypoxic and acidic conditions, its antibacterial ability is weak and easy to lead to anaerobic infection.
VSD technology has been widely used in the process of repairing wounds, and its adverse reactions have been reduced with the continuous transformation and upgrading of scientific and technological workers. In 1998, Fleischmann first proposed Negative pressure wound therapy with instillation (NPWTI).
Correct use of solution perfusion in the NPWTI process can effectively improve the wound microenvironment, inhibit bacterial growth, control inflammatory response, have the dual effects of negative pressure drainage and wound flushing, and the treatment effect is better than NPWT. Open fractures, soft tissue injuries, and necrotizing fasciitis are common acute wounds in orthopedics.
Preventing and controlling wound infection and covering wounds as soon as possible are key to treating open fractures. NPWTI provides positive drainage to the wound, and continuous wound irrigation ensures continuous wound cleaning, thus avoiding secondary contamination and shortening treatment time.
Mazen reported an open tibial fracture treated with NPWTI and skin grafting, with the main objectives of preserving leg structure, achieving bone healing, and avoiding infection. The technology product was continuously upgraded, from the initial design of only the drainage tube A type to the B type.
A small tube flush tube is placed inside the drain tube, which is eventually upgraded to a Type D that can be placed alone in medical foam and the flush tube is immediately adjacent to the drain. Zhang Yuehong et al. selected 89 patients with soft tissue defects and infections as research subjects, first underwent debridement, then used VSD material to cover the wound, and performed skin grafting + VSD negative pressure aspiration after the granulation tissue of the wound was fresh.
The results showed that after the first stage of debridement + VSD negative pressure aspiration and the second stage of skin grafting + VSD negative pressure aspiration surgery, all 86 patients survived skin grafting and cured the wounds, and 3 patients with large wounds and severe infections were also survived after debridement + VSD negative pressure aspiration surgery.
In addition, VSD combined with irrigation therapy also effectively solves the problem of frequent blockage of drainage tubes and shriveling of bubbles. Yuan Yijia et al. retrospectively analyzed the clinical treatment of chronic refractory wounds, including 100 cases of diabetic foot, 19 cases of venous ulcers of lower extremities, and 50 cases of deep II° burns of lower limbs in the elderly.
A modified adjustable vacuum suction technique was applied, i.e. drainage therapy was performed by circulating intermittent low negative pressure blocking. The survey found that the observation group was better than the control group in terms of total cure time, postoperative skin graft survival and later recurrence.
This shows that intermittent circulating low negative pressure aspiration can play a certain role in enriching wound blood supply, and provide a good repair environment for secondary skin grafting or flap transplantation by improving the environment of oxygen deficiency and nutritional disorders in diabetic foot and venous leg ulcers.
Wound local oxygen delivery is carried out by normal pressure or pressurized equipment/dressing, and the increase of oxygen partial pressure in wound tissue only needs to produce high oxygen concentration and/or high pressure locally in the wound bed, which has the advantage that the delivery of oxygen does not depend on the vascular system, the partial pressure of oxygen in the cells in the wound center area can be corrected, the risk of systemic oxygen poisoning is reduced, and treatment is more convenient.
It has been shown to be a safe and effective treatment option for many patients with chronic wounds, and it has attracted much attention as an adjuvant wound treatment. The supply of oxygen is necessary to maintain the activity of human cells, and the energy on which oxygen supply depends is necessary for anti-infection, cell division, angiogenesis and collagen-producing cellular processes, all of which are indispensable for wound healing.
As inflammatory substances ooze from the damaged tissue, microcirculation and blood oxygen supply disorders occur after wound formation, resulting in insufficient oxygen supply and low oxygen levels around the tissues. When oxygen levels in the wound are low, one glucose molecule produces only 2 adenosine triphosphate (ATP) molecules.
Hypoxia (hypoxia) inhibits key cellular mechanisms that promote tissue healing, such as collagen synthesis and cross-linking, sustained angiogenesis, bacterial targeted cells releasing reactive oxygen species (phagocytosis) and epithelialization, so if local tissues are chronically deprived of oxygen, the tissue healing process is prolonged, making wounds difficult to heal.
If the wound site is rich in local oxygen, the process is 18 times more efficient, i.e. 36 ATP molecules are produced per glucose molecule. The wound healing process includes four stages: hemostasis, inflammation, proliferation/repair, and maturation/remodeling.
Oxygen plays an important role in the normal wound healing process, and oxygen and its derivatives reactive oxygen species (ROS) run through and participate in these stages of wound healing, including regulating cell migration, adhesion, proliferation, neovascularization, remodeling and apoptosis, and also play a key role in energy metabolism and inhibition of microbial growth.
Oxygen plays a vital role in wound healing during these stages by synthesizing collagen, enhancing fibroblasts, angiogenesis, and leukocyte function.
Promotes collagen synthesis and deposition During wound healing, repair processes such as cell proliferation, bacterial defense, and collagen synthesis require 5 times more energy, and adequate oxygenation of tissues is a prerequisite for adequate energy levels, which are essential for maintaining normal cell function.
Too low oxygen levels in cells can cause the survival mode of cells to switch to anaerobic metabolism, hindering cell division and collagen production.
In addition, negative pressure occlusion drainage is easier to immobilize the skin graft after surgery, making the procedure more effective. VSD has a promoting effect on the proliferation of wound cells and collagen deposition in foot ulcers in diabetes, which accelerates the growth of granulation tissue of the wound and is conducive to wound healing.