The early stage of lower limb trauma is mostly treated by orthopaedics or emergency surgery-.Some patients have primary injuries such as such as electric burn, severe rolling of skin and soft tissue, vascular injury, or local hematoma , fat liquefaction and hematoma infection，which eventually develop into skin necrosis- ; For patients with fracture, plate internal fixation is a more common method. However, a lot of inflammatory exudate accumulate in the wound in some patients because of postoperative skin tissue swelling, excessive shear tension, skin necrosis or incision dehiscence or secondary wound infection, osteomyelitis.
In addition, due to the retention of foreign bodies such as dead bone, necrotic and degenerative tendon tissue and steel plate, the ejection reaction of the body also produces inflammatory exudation, which contains the colloidal substances such as proteins in the exudate precipitate and solidify in the foreign body surface and the surrounding spaces to form peptone which becomes a good culture medium for bacteria.Bacteria multiply in large numbers in the above-mentioned areas(Figure 2), release toxins, and further aggravate the inflammatory reaction of the tissue around the wound, so that the wound continues to produce exudate and pus, forming a vicious circle, and the wound can not heal-.After timely wound dressing change and anti-infective treatment, the acute inflammation of the wound was controlled and turned to chronic wound, the bone plate was exposed or formed one or more sinuses. After several months or even longer treatment, there was no obviously tending to heal.
For this kind of wounds, the traditional method is to use various flaps to repair them, but some patients split again across the position of the steel plate at the suture of the flap edge and the recipient area, and the steel plate is exposed again, certainly some flaps heal well in early time, however,1 or 2 months after operation, the sinus tract on the suture line between the flap and the recipient area appeared again, with intermittent discharge of secretions, and the sinus orifice showed typical chronic inflammation.The early swelling of the transplanted flap is an important reason for the re split of the flap and the exposure of bone steel nails,In the later stage, due to the contracture of the flap tissue and the tissue around the wound, the tension between the flap and the wound suture was too large,Because the suture between the flap and the recipient tissue is a single end-to-end contact, under the action of tension, the tissue at the suture becomes thinner and finally splits,In particular, if the suture crosses the bone or steel plate, there is no active tissue in the deep layer to provide healing and implantation, and it is only a matter of time before the wound splits again.
Some scholars reported that if the wound fails to heal in 4 weeks, it will become a chronic wound. The important characteristic of chronic wound is the stagnation of wound healing process.Once a chronic wound is formed, the tissue repair process stops, the tissue around the wound becomes fibrotic, scarred, and stops growing,The exposed bone, tendon or steel plate can not be effectively covered by tissue, resulting in lasting exposure.
Another important reason for healing failure is the residual foreign bodies in the wound and the formation of dead cavity, especially infectious foreign bodies. Necrotic bone and tendon, the steel plate as a foreign body in the wound can neither be completely removed nor effectively covered.Tissue rejection and bacterial colonization make the wound inflammatory reaction continue, and the dead cavity at the bone plate or broken end of the fracture becomes the best place for the accumulation of inflammatory exudate and pus. The protein components in the exudate solidify into a good bacterial culture medium, and the bacteria multiply to produce pus, which further stimulates the surrounding tissues to produce inflammatory reaction and form a vicious circle.A large amount of pus accumulates and disperses to the deep along the steel plate or bone to form a pus cavity. The external tissues become brittle and thin due to inflammatory reaction, and finally the skin breaks and the pus is discharged to form cracks or sinuses (Fig. 8: A, B, c).
Due to the stimulation of chronic inflammation, the tissue around the wound gradually fibrosis, scarring, congestion and blood stasis, thickening, dark purple color, lack of elasticity, poor circulation, which is not conducive to wound repair-.
In this study, according to the causes of the formation of secondary chronic bone exposure wound, through one-stage expansion, remove the scar skin within a certain range around the wound, cut or remove the sinus wall, scrape out the basal granulation tissue, and cultivate a fresh wound bed in combination with VSD,turn the chronic wound into an acute wound,reactivate the wound healing process,and provides a good basis for flap healing and wound final healing.After the preparation of the wound bed, the second stage debridement.The necrotic bone, periosteum, tendon tissue and peptone on the surface of the plate and bone were removed, the space around the bone of the plate was filled with artificial dermis, and the exposed bone and plate were completely covered.Then the wound was closed with flap transfer.Artificial dermis isolated the contact between body tissue and foreign body in the early stage and blocked the rejection . After operation, the flap was wrapped with appropriate pressure to effectively prevent the possibility of dead cavity residue and blood accumulation under the flap to form pus cavity.Using fascial cuff flap transplantation, the suture between the flap edge and the wound edge tissue was changed from end-to-end plane contact to three-dimensional mortise and tenon contact,This three-dimensional contact and wound bed with rich basal blood supply greatly increases the contact area between the flap and the tissue around the wound, so that the flap and the wound can establish blood supply in an earlier and wider range, form a complete fibrous capsule earlier, and completely embed the dead bone and steel plate.At the same time, the three-dimensional mortise and tenon contact can effectively prevent the risk of skin thinning and cracking at the suture due to the excessive tension caused by the retraction of the flap.Since the bacteria in chronic wounds are mainly low toxic strains , after twice debridement and cleaning with VSD and alcohol, the bacterial content is greatly reduced. Fresh wound granulation tissue and flap tissue with reliable blood supply can completely remove the residual bacteria, and the possibility of infection and sinus formation has been significantly reduced.
In recent years, our unit has treated many patients with the above condition. On admission, most of the wounds were partial steel plate exposure with sinus formation, a few was all steel plate exposure, local bone exposure, bone cortex was gray yellow or gray black, with necrotic tendinous tissue exposure. In all cases, the skin around the wound was dark purple, hard and inactive. The growth of wound epidermis was reversed, and there was a small amount of purulent secretion in the wound.
When expanding the wound, the scar skin and fibrotic tissue of the outer wall of the steel plate should be excised. If there is a sinus, the outer wall of the sinus should be incision, and the fibrous capsule inside the outer wall and the sinus cavity should be removed. If necessary, make a transverse incision at the bottom of the sinus wall, so that the sinus wall can be loosely attached to the base after the fibrous capsule is removed. If the fibrotic scar of the outer wall of the sinus is so severe that it can not be well attached to the base, it can be removed as appropriate. Free bone fragments should be removed. The necrotic periosteum and tendinous tissue at the base of the wound were also removed as clean as possible. Scratching the aged granulation at the bottom can cause bleeding in the wound, which can lead to fresh wounds, thus activating the wound healing process. The protein-like tissue attached and precipitated in the holes of the steel plate, in the steps formed between the edge of the steel plate and the bone surface, in the gap formed by the incompact adhesion between the steel plate and the bone, and in the gap at the broken end of the bone should be carefully cleaned to remove. During the skin flap transplantation, the denatured and necrotic bone cortex should be chiseled off 1-2mm, the peptone in the steel plate steps and spaces should be removed, and the exposed bone or steel plate should be covered with artificial dermis. The gap between the steps formed at the edge of the steel plate and the bones under the plate should be closely filled, so that the dead space will not remain after the flap transplantation and avoid infection and necrosis caused by effusion under the flap after operation.
Artificial dermis was developed by yannas and Burke in 1980. It is a membrane artificial skin and a synthetic tissue used to repair skin tissue [25,26].S. Suzuki researched and improved the product and developed a new artificial dermis (PELNAC), which is widely used in scar shrinkage repair, excision of wounds caused by tumors, traumatic skin defects, peeling of skin flaps and other reasons,the effect evaluation shows that the good rate is 86%.In recent years,PELNAC has been widely used in some wounds with bone exposure after trauma. When the artificial dermis was transplanted to the wound with poor basal blood supply, the time of local vascularization was delayed than that of the wound with good basal blood supply.In this study, two debridement and VSD were performed to complete the wound bed preparation, so as to form a wide base with good blood supply around the wound, so as to ensure the vascularization of artificial dermis and the healing of flap. The blood supply of the flap is reliable. When the flap covers the artificial dermis, in a short time, the deep layer of the artificial dermis is filled with new collagen, and the sponge structure is replaced by true skin like tissue, so as to quickly complete the embedding process of steel plate or exposed bone.