CHAPTER 36
OPEN FRACTURES AND GUNSHOT INJURIES


 

  • SECTION ONE: MANAGEMENT OF THE OPEN FRACTURE
  • SECTION TWO: WOUND BALLISTICS



    SECTION ONE
    MANAGEMENT OF THE OPEN FRACTURE


    DAVID M. NUNAMAKER

  • Physical Examination
  • Radiographic Examination
  • Surgical Debridement
  • Fixation
  • Postsurgical Management
    An open fracture can be defined as a broken bone that is in communication through the skin with the environment. The amount of communication can vary from a small puncture wound in the skin to a large avulsion of soft tissue that leaves bone exposed. In contrast, a closed fracture is one that is contained within the extremity without a break in the integument. The old nomenclature of simple for closed fracture and compound for open fracture has largely been discontinued. Open fractures are much like pregnancy: they either are or they are not. Closed fractures, on the other hand, can contain devitalized skin that can be easily penetrated by bacteria resulting in the same problems that occur with open fractures. Closed fractures should, therefore, be evaluated very carefully in regard to the intactness of the integument and its viability. Closed fractures can usually be considered clean if the skin is not devitalized. All open fractures, on the contrary, are considered contaminated. Deceivingly small, seemingly insignificant puncture wounds associated with a fracture may, in fact, have severe consequences brought about by penetration of foreign matter into the extremity combined with neglect through nondiagnosis or improper treatment of the open fracture (Fig. 36-1).

    Open fractures are classified according to their severity.(33,42) In a first-degree open fracture, the bone fractures and then penetrates the skin from within. Firstdegree open fractures have very small wounds and following surgical debridement can be treated in the same manner as a closed fracture. Second-degree open fractures are more extensive than first-degree open fractures, and there is usually a larger wound that communicates with the fracture. Soft tissue may be injured to greater extent, and these fractures represent a middle ground between first-degree and third-degree fractures. Third-degree open fractures represent the most severe form of open fracture with comminution of the fracture and massive soft tissue damage. Soft tissue and bony avulsion may be part of the fracture, and often these injuries are caused by forces from without. Most commonly third-degree open fractures in the dog are the result of high-velocity bullet wounds. Some open fractures caused by vehicular trauma can also fall into this category. With the loss of soft tissue, these fractures represent the most demanding type of problem seen by the veterinarian.

    Any open fracture represents a contaminated wound. Contamination can occur at the time of the injury and anytime thereafter while the wound is exposed to the environment. Therefore, it is important to provide first aid measures whenever dealing with open fractures. The two major problems that must be overcome with open fractures are hemorrhage and protection of the wound. Many times, application of a pressure bandage with a clean dressing can solve both problems simultaneously. If hemorrhage is not a severe problem, the wound should still be covered and protected by a clean dressing. Most animals will be able to support themselves, but some animals following open fracture and severe bleeding may be in a state of shock and must be transported on a board or stretcher. The importance of covering the wound initially cannot be overemphasized.(42) Most of the organisms that are recovered from the wound following development of an infection can be traced to a hospital serotype and do not represent organisms that were present at the accident site.(33,42) Protection of the wound during transport and entrance into the hospital may significantly reduce this form of contamination.


    PHYSICAL EXAMINATION
    When an animal presents with an open fracture, diagnosis of the fracture has already been made and hopefully the wound covered with a dressing. The purpose of the physical examination is to determine the status of the patient, to stabilize the patient, and to assess all injuries. If external bleeding is a problem at the time of injury, usually a pressure dressing applied to the area can control hemorrhage while the physical examination is performed. Occasionally, spurting blood may require the use of a hemostat to directly control the source of bleeding. Rarely, if ever, should a tourniquet be applied to control bleeding in a hospital environment. Physical examination should include all of the body systems, usually leaving the fracture until last. If, in fact, the fracture is not covered on presentation, it should be covered immediately and bandaged with a sterile dressing. If a dressing has already been applied, it should not be disturbed at this time. If the dressing is inadequate, additional dressing can be applied over the existing dressing to completely cover and isolate the wound from the environment. Initial physical examination should try to assess neural and vascular supply to the limb below the area of the fracture. Blanching of the capillary bed or a pulse felt below the injury is indicative of adequate vascular flow. The warmth of the extremity is also a helpful sign, but the extremity may be cool if the animal is in shock, and the capillary bed may also be affected by this situation. Clipping a toenail short is another way to assess peripheral vascularity beyond the fracture site. If capillary bleeding exists, it is a positive sign for ah intact vascular supply for the foot. If the status of the limb's vascularity remains in doubt, arteriography should be performed.

    FIG. 36-1 (A) An undiagnosed open fracture of the proximal femur was referred for internal fixation. Clipping of the leg prior to surgery showed a punched-out skin lesion on the lateral thigh. (B) Surgical exploration revealed the missing skin attached to the end of the distal fragment. Frank infection was present. Approximately 1 liter of purulent fluid was removed and the internal fixation applied using a suction drain. (c) A poor clinical result correlated well with this radiograph picture of a degenerative arthrosis of the hip at 3 months.

    The history surrounding the injury is of great importance when dealing with open fractures. It is important to know, for instance, whether the automobile struck the animal or ran over it. The soft tissue damage that is always a part of this injury can in great measure be a part of the prognosis regarding it. Very often, the amount of soft tissue injury can be assumed only by looking at the radiographs; a comminuted fracture would indicate a high-energy type injury and/or massive soft tissue swelling, which in turn would indicate a large amount of soft tissue damage and/or hemorrhage. Kinetic energy involved in the wounding of the animal (KE = 1/2 mv^2) is just as important in vehicular injury as it is in wounds created by missiles. Complications such as tetanus or clostridial myonecrosis (gas gangrene) are more likely in open fractures associated with high kinetic energies. The devitalization of muscle mass and loss of vascularity, hence oxygenation of the tissues, are all important for these obligate anaerobes. Since the incubation period of the clostridial organism is usually less than 24 hours, it is important to recognize quickly the conditions that may lead to its presence. During the physical examination it is important not to manipulate the injured extremity to any great extent. More severe soft tissue injuries may occur through manipulation, and any lacerated vessels that have been temporarily occluded may start to hemorrhage again. The dressing that was placed over the limb should not be removed until the animal is taken to the operating room for debridement. The unnecessary examination and probing of an open wound by one or several clinicians in a hospital environment is conducive to further contamination with pathogenic organisms of a hospital serotype.


    RADIOGRAPHIC EXAMINATION
    Following evaluation of the patient, including blood work and any stabilization necessary, radiographic examination of the injured extremity should be undertaken. It is necessary to examine the entire involved limb segment radiographically. This should include the joint above and below the actual fracture. Biplane radiographs are necessary to determine the extent of injury to the bone. Arteriography may be used if indicated. Radiographs will reveal the extent of the bony injury and suggest the soft tissue involvement. The radiographic picture will allow for a plan of action to be undertaken when the animal is taken to the operating room for complete wound debridement and definitive fracture treatment. This plan may be modified or changed as surgical debridement of the wound is undertaken and the extent of the soft tissue injury is realized; therefore, it is important to have all the necessary instruments prepared to undertake the definitive treatment of this fracture.


    SURGICAL DEBRIDEMENT
    Surgical debridement is accomplished in the operating room under aseptic conditions. Surgical preparation of the limb is carried out through clipping and scrubbing of the area around the wound before removal of the bandage. Following general preparation of the leg and donning of a cap, mask, and gloves by the surgeon, the rest of the wound may be clipped and surgically scrubbed. A sterile lubrication jelly can be placed in the wound to avoid contamination of the wound with the hair while clipping. This lubrication jelly is miscible with water and is rinsed away during surgical debridement. The wound itself is cleansed in the same manner as the leg. Copious amounts of fluid are used to rinse the wound clear of hair and debris. A complete surgical scrub is carried out and the wound is draped; the surgeon, who is regowned and regloved after inspection of the wound during surgical preparation, begins the surgical debridement. Since copious amounts of fluid will be used in washing the wound, it is important to provide a plastic sheet or other impenetrable barrier for fluids between the extremity and the rest of the body or table. In general, during debridement the wound should be flushed with liters of fluid. The literature shows a decreased infection rate when 10 liters or more of fluid are used for wound flushing during debridement.(23) This flushing can be accomplished with the use of a bulb syringe or, as has been more recently recommended, the use of a pulsetile water jet such as a Water Pik.(22) Just forceful cleansing of the surface of tissues will rid them of bacterial contamination as well as debris, which would have the potential for bacterial colonization. A significant difference seems to exist in bacterial infection in experiments associated with the use of a bulb syringe versus Water Pik-type cleansing.(22) These studies have shown the beneficial effect of the Water Pik-type device in contaminated crush wounds.

    The use of antibiotics in the irrigation solution has been shown experimentally to reduce the incidence of infection in contaminated wounds. However, the use of antibiotics is no substitute for good surgical debridement. The rapid penetration of the wound by pathogenic organisms was demonstrated by Petty to prevent complete sterilization by antibacterial solutions.(44) However, antibiotics are useful in decreasing the bacterial population and may reduce the surface contamination to zero. Commonly, the agents used are those that are not used systemically because of toxicity. In the past the most common combination was a neomycin-polymyxin-bacitracin solution containing 1 g neomycin, 500,000 units polymyxin, and 50,000 units of bacitracin per liter of saline or Ringer's solution. Kanamycin at a concentration of 2 g/liter solution is also a popular choice. All combinations of the above drugs have been used as well as many others. The kanamycin solution seems to work well if Pseudomonas is not a problem. Polymyxin added to this will control the Pseudomonas. When using any local antibiotic, systemic absorption may represent a problem; therefore, it is very important not to overdose the patient by this route. The effects of local antibacterial agents are local not systemic, but the ototoxic, neurotoxic, and nephrotoxic effects can be achieved through local lavage. Recently, we have gone to flushing the wound during operative procedures using the antibiotic solution in a spray bottle, to allow a gentle mist to be sprayed over the entire wound once every 5 minutes. The spray bottle limits the amount of solution used, so that adequate concentrations are achieved with minimal volumes. The antibiotic solution is not used during initial debridement and irrigation, since the fluid volumes required at this stage are so large (> 10 liters). Surgical exposure should be adequate for debridement but should not devitalize more tissue. The skin incision should be through a skin surface that does not appear to have vascular compromise. Sometimes the incision can be an extension of the wound, whereas a separate incision away from the wound may be necessary in other cases. The use of a surgical implant may also modify the approach that is taken. It is important to remember that wound healing can take place only where the skin has adequate vascularity. The surgical debridement should be thorough, with removal of all devitalized tissue. Sometimes it is difficult to determine if some tissues may be viable. The dependable features for predicting viability of muscle are listed in order of decreasing significance: ability to bleed, consistency, contractility, color. Color, an often used criterion, is really one of least reliable and depends on the light source being used to examine it or tissue perfusion. If adequate tissue perfusion is present, active bleeding will be present during resection. All nonviable tissue is excised. There must be no exceptions if wound healing is to proceed. Once the wound is clean, the fracture is reduced and stabilized. The techniques used to stabilize open fractures are those that can be used in the open treatment of closed fractures as well as in the closed treatment of closed fractures.


    FIXATION
    The use of a cast or splint in the treatment of an open fracture depends on the stability of the fracture after reduction (it must be inherently stable) and on the amount of soft tissue damage. Casts and splints make wound care difficult and usually allow excessive movement of the fracture during the frequent cast changes that are necessary to deal with open wounds. The compromised skin vascularity may also prohibit the use of a cast or splint.

    Intramedullary devices can be used with first- and second-degree open fractures, but the introduction of an intramedullary device in a contaminated or infected fracture may spread the contamination to the entire medullary cavity, where it is difficult to treat. Therefore, intramedullary rods are used in first-degree open fractures in the dog with results similar to those that would be expected with open treatment of closed fractures by the same methods. Intramedullary devices are not used in third-degree open fractures. Their effective use in seconddegree open fractures is related to the stability they confer to the fracture and to the severity of the soft tissue injury.

    Plates and screws for fixation in open fractures of the first-and second-degree type have found widespread use in veterinary orthopaedics (Fig. 36-2). This stable internal fixation has allowed the surgeon to reduce and stabilize the fracture, permitting the soft tissues to heal without motion at the fracture site. When dealing with severe, third-degree open fractures in the dog, the acceptance of internal fixation with plates and screws is not universal. It has been shown that certain severe fractures can be stabilized and heal with the use of plates and screws, but severe unrelenting infection can also be a possibility. My choice for severe, third-degree open fractures depends on the type fracture, vascularity of the skin, and the nature of the incision that would be necessary to place the plate.

    The implant should be placed away from the open wound, although sometimes it must encompass it. External skeletal fixation is my first choice for treating severe third-degree open fractures (Fig. 36-3). The placement of the pins away from the fracture site and soft tissue injury preserves tenuous vascularity and allows for adequate wound care. The combination of interfragmentary screw fixation with a full-frame external skeletal fixation often represents the optimal method of stabilizing the fracture without stripping away vascularity that plating may demand. Simple interfragmentary lag screws can be inserted without increased wound exposure following good surgical debridement.

    FIG. 36-2 (A) This comminuted second-degree open fracture of the femur occurred in a Great Dane that was hit by a garbage truck. (a) Two plates and a massive bone graft were used to stabilize the fracture. The animal returned to the show ring in six months, although complete healing was delayed. (C) A radiograph at 10month follow-up shows complete healing.

    FIG. 36-3 A third-degree open fracture of the tibia is stabilized with minimal internal fixation (three screws [A] and an external skeletal transfixation [B]).


    POSTSURGICAL MANAGEMENT
    The management of the wound following definitive fracture treatment is most important. The decision to close a wound or leave it open often will determine success or failure of the fracture repair. Although each case will present slightly different problems, some basic rules should be followed and remembered. All open fractures present with contaminated wounds. Wounds presented or dealt with after the 6 hour "golden period" can be considered to be infected. In my opinion, closure of a wound should be considered only with a well-debrided, clean first-or second-degree open fracture. These wounds must have good vascularity, no tension or dead space when closing, and no devitalized tissue within their boundaries. Primary closure is also performed when closed suction drains can be used to control dead space. All other wounds are best left open. Following surgical debridement, the wound is lightly packed with sterile Vaseline gauze sponges. The wound is bandaged with sterile cotton roll and the animal is recovered. The dressing is changed in 2 to 4 days in an aseptic manner. If further debridement is needed, the patient is returned to the operating room and another surgical debridement is carried out. Additional loose packing of the wound is performed and bandage changes repeated as needed. When the bed of the wound is covered with granulation tissue, the immediate threat of infection is gone. At this time, the wound can be left to granulate closed (skin transplants are rarely used in the dog) or a delayed primary closure is carried out by returning the patient to the operating room and closing the wound after careful inspection and freeing of the skin edges to prevent tension in the suture line.

    Occasionally, large bone and soft tissue defects are present. These wounds can be managed with a massive cancerous bone graft after the wound bed is covered with granulation tissue, usually within 10 to 14 days. In this instance the graft (see Chapter 39) is used to fill the entire wound with cancerous bone right up to the skin edges. The wound is covered with Vaseline gauze and kept under a sterile bandage, which is checked by changing as needed (every 2 to 4 days). When gaps exist in the fracture fragments, cancerous bone grafts should be used either immediately with good vascularity or after a 10 to 14-day delay when dealing with impaired circulation. Bone grafts tend to help speed union in all fractures, but especially in open fractures. If the graft does not take because of poor vascularity, it undergoes coagulation necrosis and is exuded from the wounds. Open fractures respond well to good surgical debridement and wound care. Stabilization of the fracture allows more rapid healing of the soft tissues and seems to control infection. Implants can and should be used for correct indications in open fractures, along with cancellous bone grafts.



    SECTION TWO
    WOUND BALLISTICS

    PAUL BERG