Open fractures

Introduction:

The treatment of open fractures can be challenging. Open fractures are often the result of high energy mechanisms. Additionally, contamination of the fracture site as well as devitalization of the soft tissue envelope greatly increases the risk of infection, nonunion and wound complications when compared to closed fractures.

Treatment of these fractures begins with a thorough assessment of the patient and classification of the injury with the goals of wound coverage or closure, prevention of infection and restoration of length, alignment, rotation and stability. Advances in antibiotics, fracture stabilization, orthobiologics and particularly modern plastic surgery techniques have improved the prognosis for functional recovery and limb salvage for severe open fractures.

Classification:

Open fractures are classified according to the system of Gustilo and Anderson. This system was first proposed in 1976 and modified in 1984 into the system that is in use today. According to this classification, type I injuries have puncture wounds <1cm in length with minimal contamination or soft tissue injury. Type II injures have a wound >1cm in length, but without extensive soft-tissue damage, flaps or avulsions. Type III injuries are subclassified into categories a, b and c. Type IIIa injuries have extensive soft tissue damage secondary to high energy trauma, but have adequate soft tissue coverage. Type IIIb injures exhibit severe periosteal stripping and bone exposure usually associated with massive contamination. Type IIIc fractures are associated with arterial injury. As the full extent of soft tissue injury and viability is often difficult to assess at presentation and may not correlate with the size of the skin defect, the classification of an open fracture should be made in the operating room. This allows for full wound exploration and will provide a better understanding of the true extent of soft tissue damage.

Despite the widespread use of this classification system, the interobserver agreement has been questioned. However, this classification system has been shown to have prognostic significance with increasing infection rates and worse outcomes associated with Type III injuries.

Antibiotics and Infection

Infection Risk and Wound Culture

24-70% of open fractures are contaminated with bacteria, however, in the absence of antibiotic prophylaxis, infection occurs in approximately 14% of open fractures. In an effort to predict infection and ultimately, the causative organism, routine pre- and post-debridement wound cultures have been suggested. However, multiple studies have demonstrated that initial wound cultures in the early post-fracture setting are ineffective in predicting infection or the causative organism. Additionally, post-debridement wound cultures fail to isolate the infecting organism the majority of the time. Thus, early post-fracture wound cultures are not recommended.

Antibiotic Prophylaxis

As with many routine practices, the justification and evidence for the use of prophylactic antibiotics for open fractures has been obscured with time. Much of what is considered standard practice regarding this subject is based on a few important papers published before the era of modern open fracture management as well as the surge in nosocomial infections and bacterial resistance patterns. The effects of prophylactic antibiotics on antibiotic resistance, the increased nosocomial infection rate and mortality from nosocomial pneumonia must be weighed against the short term control of infection in open fractures with an understanding that today, most infections in open fractures are caused by nosocomial flora and not through initial wound contamination or the patient's native flora.

Antibiotics were long believed to prevent infections in open fractures, although until the prospective, randomized, placebo-controlled study by Patzakis et al in 1974, there was no evidence to support this assumption. This study and subsequent studies established strong evidence for the efficacy of first generation cephalosporins in the management of open fractures. However, it has also been suggested that antibiotic prophylaxis should include both gram-positive and gram-negative coverage. Currently, there are insufficient data to conclude that gram-negative prophylaxis is beneficial for open fractures. Additionally, it has been commonplace to recommend the use of penicillin G for prophylaxis against clostridial myonecrosis. There is insufficient data to support this recommendation as well. Moreover, it is rare for clostridium perfringens to be resistant to the anitbiotics typically used for open fracture prophylaxis and today penicillin G may be considered suboptimal treatment for C. perfringens. Adequate debridement and delayed closure for wounds thought to be at high risk for clostridial myonecrosis (farm injuries and ischemia) cannot be overemphasized.

Quinolones have been shown to be an effective alternative to cephalosporins for prophylaxis for Type I and Type II open fractures. However, they have not been shown to be effective for Type III fractures. This class of drugs is attractive since it offers broad-spectrum bacteriocidal coverage, oral administration, less frequent administration and the ability to provide prophylaxis for penicillin allergic patients, however these benefits must be weighed against experimental evidence suggesting that fluoroquinolones adversely affect the early phases of bone healing.

Timing and Duration of Prophylaxis

Antibiotic prophylaxis should be initiated as soon after the injury as possible as the timing of the antibiotic prophylaxis has been shown to be important for prevention of infection. However, the appropriate duration of antibiotic prophylaxis is less clear. There is evidence that shorter courses of antibiotics are just as effective as longer courses, but the most appropriate duration has not been determined.

In conclusion, there is evidence to support a short course of first-generation cephalosporin administration or similar agent active against gram-positive bacteria as prophylaxis for most types of open fractures. Duration of prophylaxis should be limited to a 24 hour course with repeated 24 hour courses likely indicated for subsequent debridements, wound closures, bone grafting or other major surgical procedures.

Wound Management

Debridement and Irrigation

Debridement and irrigation are vitally important to the successful management of open fractures. While the details and methods of irrigation are still debated, the role of a careful and complete debridement is clear. Gustilo emphasized this point by stating that an adequate debridement is the single most important factor in the attainment of a good result in the treatment of an open fracture.

A systematic debridement should begin with removal of gross contamination and debris. Use of a tourniquet should be minimized. It is important to understand that the injury shock wave can devitalize tissues beyond the extent of the skin defect and often, it necessary to extend the injury wound to adequately evaluate the nature of soft tissue injury. All necrotic tissue should be excised. Muscle viability is determined by the four C's: contractility, color, consistency and capacity to bleed. Evaluation of the bone should ensue with removal of completely free cortical fragments. When it is difficult to fully determine the viability of all tissues at the time of initial debridement, repeated debridements at 24-48 hour intervals can be employed to eliminate devitalized tissue that may declare itself.

Irrigation is employed to supplement a systematic debridement in removing foreign material and decreasing bacterial load. Despite its importance and the frequency with which irrigation is employed, there is a relative paucity of high-quality literature pertaining to the optimal solution, volume, additive and method of irrigation for open fractures.

There is scant animal data suggesting that increasing the volume of irrigation improves the removal of bacteria and debris, however the optimal volume has not been determined. Based on the wide availability of 3L bags of normal saline, a review by Anglen arbitrarily recommended 3L of irrigation for Type 1 fractures, 6L for Type 2 fractures and 9L for Type 3 fractures.

While most surgeons use sterile saline alone for irrigation, the addition of antiseptics, antibiotics and surfactants have each been studied for their efficacy in reducing bacterial load and subsequent infections as well as their effects on local tissue viability and healing. Antiseptic solutions such as povidone-iodine, Dakin's solution and chlorhexidine have not been shown to decrease infection rates. They have been linked to tissue damage and thus should be avoided. Antibiotic irrigation has been shown to decrease infection rates in animal studies. However, recently surfactant (nonsterile soap) solutions have been shown to be more effective, cause less tissue damage and be more economical than antibiotic solutions.

In addition to the volume of irrigation and additives, the effect of irrigation pressure has also been evaluated. Pressures greater than 50psi have been shown to be detrimental to bone and soft tissue, slow bone healing and potentially drive bacteria further into the wound.

Timing of Debridement and Irrigation

The timing of effective initial surgical debridement of open tibia fractures remains controversial. Most current guidelines pertaining to the timing of initial surgical debridement of open fractures recommend that debridement occur within 6 hours of injury. However, little recent data exists to support this recommendation, which is believed to stem from Freidrich's 1898 study of guinea pigs. The majority of current literature is unable to demonstrate an improved infection rate for open fractures initially debrided within 6 hours of injury

Immediate Primary Wound Closure

Immediate primary wound closure is possible when there is adequate viable soft tissue to close an open wound without tension. Historically, immediate primary wound closure was associated with clostridial myonecrosis. However, with modern antibiotic prophylaxis and adequate debridement and irrigation, it has been shown that immediate primary wound closure is not associated with in increase infection or nonunion rates. Immediate primary wound closure also may decrease nosocomial infection rates by sealing open wounds and minimizing the number of subsequent debridements. In wounds in which tissue of questionable viability is retained or severe contamination is present, other methods of wound management should be considered.

Local Antibiotics

Management of large open fracture wounds with antibiotic-impregnated delivery vehicles can be a useful adjunct to systemic antibiotic prophylaxis. The most common delivery vehicle is polymethylmethacrylate (PMMA) cement which is impregnated with antibiotics. Commercially-available PMMA beads are not available in the US, so they must be made by the surgeon. Typically, forty grams of PMMA are mixed with 3.6 grams of tobramycin, molded into 5-10mm spheres and strung on suture or wire. Most often, aminoglycosides are utilized due to their broad spectrum of activity and heat stability, although vancomycin and cephalosporins have also been employed. Local antibiotics are most often utilized in the bead pouch technique. After appropriate debridement and irrigation, this technique places aminoglycoside-impregnated PMMA beads into an open fracture defect and seals the defect with a semi-permeable sterile covering. This technique allows for very high local concentrations of antibiotic (10-20 times higher than systemic administration) without elevated systemic concentrations. It also decreases potential nosocomial contamination by providing a sealed aerobic environment. In a series of 1085 open fracures, Ostermann found an infection rate of 3.7% for those treated with the bead pouch technique and systemic antibiotics compared a 12% infection rate for systemic antibiotics alone.

More recently, bioabsorbable delivery vehicles such as calcium sulfate, demineralized bone matrix and fibrin clots have shown promise in preventing infection in animal models. These delivery vehicles would eliminate the need for removal of PMMA cement and may decrease the number or volume of autografts, while providing osteoconductive and osteoinductive material to aid fracture healing.

Negative Pressure Wound Therapy

With the introduction of the Vacuum Assisted Closure device (VAC;KCI, San Antonio TX), negative pressure wound therapy has risen in popularity. The VAC device has been shown to decrease edema, rapidly increase granulation tissue and reduce wound size. Recently, the VAC has been credited with decreasing the need for free tissue transfer for open fracture wound coverage. However, it does not appear that VAC decreases the rate of open fracture wound infection when wounds are not definitively closed in a timely fashion.

Soft Tissue Reconstruction

Type III open fractures, due to their extensive soft tissue damage, often require soft tissue reconstruction for wound coverage. Reconstructing the soft tissue envelope is vitally important for fracture recovery by providing durable vascularized coverage. The improved vascularity to the wound bed afforded by reconstruction decreases infection rates by improving delivery of antibiotics, promoting native immune responses and covering the wound from the environment, thus reducing the risk of nosocomial infection. Additionally, soft tissue reconstruction promotes fracture and soft tissue healing and prevents wound dessication.

Soft tissue coverage can be achieved through the use of local rotational flaps, free flaps, fasciocutaneus flaps and skin grafts. The location, size and volume of the defect as well as the extent of local soft tissue damage often determine the reconstruction method to be utilized. Local rotational flaps are technically easier, but are limited by their rotation radius and the potential of transferring tissue that was damaged in the same trauma as produced the open fracture. Fasciocutaneous (FC) flaps are tissue flaps that include skin, subcutaneous tissue and fascia and obtain their blood supply from single or multiple fasciocutaneous perforators. These flaps are less bulky, may be raised locally or free and are useful when dead space is minimal. Free flaps usually involve transfer of skin, subcutaneous tissue, fascia and muscle and can provide large volumes of undamaged, well-vascularized tissue to cover large defects or three-dimensional wounds with dead-space.

Timing of Coverage

Soft tissue reconstruction should be performed within 7-10 days. The literature is inconsistent in regards to the optimal timing of reconstruction, but studies have consistently shown that delays in reconstructive wound coverage are associated with increased infection and flap failure rates.