Infection after fracture surgery is a challenging entity. Prompt diagnosis and treatment is of paramount importance. Successful treatment includes culture-specific antibiotic therapy in collaboration with the infectious disease team.
8 Infection after Fracture Fixation and Infected Nonunions
Prompt identification of early deep infection is of paramount importance to avoid the sequalae of chronic osteomyelitis.
Accurate microbiology diagnosis using multiple and adequate samples is crucial for targeted antibiotic therapy.
In the case of Grade 3B open fractures, adequate debridement in conjunction with a plastic surgeon to enable expeditious closure has been shown to reduce infection.
8.1 Antibiotic Prophylaxis for Open Fractures
Open fractures represent a marker of high-energy trauma and significant soft-tissue injury. They are associated with an increased risk of infection, as bacteria on the skin or in the environment are given access to the deep soft tissues and fracture site. 1 Often, there is macroscopic contamination of the bone ends themselves. Further, areas of muscle or bone necrosis resulting from the trauma can make infections more difficult to control once established.
The prophylactic use of antibiotics in the setting of open fractures has been common-place for over half a century. Open fractures are typically classified according to the system of Gustilo-Anderson (▶ Table 8.1). 2 When classifying open fractures, the injury is assigned a type based on its worst feature. For example, an injury with a 2 cm wound, extensive fracture comminution, and periosteal stripping would be assigned type IIIa. The risk of infection in open fractures is directly related to Gustilo-Anderson type. While type I injuries have an infection risk similar to closed injuries when treated with prophylactic antibiotics and timely surgery, the risk of infection in type IIIb and IIIc fracture approaches 30 to 50% in some series. 3 The risk of infection in types II and IIIa fractures falls between these extremes.
Early administration of antibiotics has been shown to reduce the risk of infection in open fractures. 4 The American College of Surgeons (ACS) recommends that antibiotics be given within 1 hour of presentation to the hospital. Many systems now try to administer antibiotics on the scene or during transport by Emergency Medical Service (EMS) personnel.
Other factors that are associated with reduced risk of infection include a timely and thorough soft-tissue debridement and early soft-tissue coverage when a flap is required. 5 , 6 , 7 The exact timing of debridement remains controversial. Historically, open fractures were treated as an emergency and every attempt was made to take the patient to the operating room within 6 hours of the injury. The ACS now recommends that all open fractures be treated in the operating room within 24 hours, if possible. There are some injuries, particularly ones with extensive soft-tissue injury and/or contamination that may benefit from a more urgent debridement.
There is little agreement on the optimal choice of antibiotic for prophylaxis for open fractures. Many surgeons advocate for a first-generation cephalosporin for prophylaxis against low-grade open fractures (type I or II). High-grade open fractures (type IIIa/b/c) likely benefit from expanded coverage with either an aminoglycoside, fluoroquinolone, monobactam, or glycopeptide. 1 For injuries with soil contamination, the addition of penicillin or metronidazole can cover clostridial infections. An example of a reasonable prophylaxis protocol is presented in ▶ Table 8.2.
Antibiotic prophylaxis should be initiated as soon as feasible. Once started, it should be continued for 24 hours for low-grade injuries and up to 72 hours for high-grade injuries. Predebridement wound cultures have not been helpful in predicting infection or the organism of an eventual infection. 8 Postdebridement cultures may have some value in targeting any remaining bacteria before an infection becomes entrenched. 9
8.2.1 Clinical Diagnosis
Infection after fracture surgery remains difficult to diagnose and historically has not been standardized. More recently, a consensus statement related to the definition has been proposed (▶ Fig. 8.1). Fracture-related infection (FRI) has been categorized into confirmatory criteria, such as fistula, sinus, wound breakdown, or purulent drainage from the wound, and suggestive criteria such as clinical or radiological signs indicating infection, joint effusion, elevated inflammatory markers, or wound drainage. This new definition may allow for better diagnostic accuracy and communication among surgeons. However, FRI does not attempt to classify infection, help with guiding treatment, or consider anatomical variations. 10
FRI can occur at any point after fracture surgery. Diagnosis of early infection within the first 2 weeks is difficult. Trauma to the soft tissue may confound the clinical picture, and the classic clinical signs and symptoms of wound infection (i.e., pain, warmth, erythema, swelling, and fever) may be attributed to trauma or the operation. In general, a wound, with continuous drainage, that fails to epithelize within 7 to 10 days should raise the suspicion of a deep infection and should be treated surgically without delay (▶ Fig. 8.2).
The clinical signs of infection are generally more obvious 2 weeks after the fracture surgery. Early loosening of the hardware, pain, fever, and erythema around the incision site are common signs.
Late infection (>10 weeks) can be difficult to treat due to the likely development of biofilm, dead tissue, and fracture instability. Therefore, early diagnosis of deep infection is warranted to prevent major complications and prolonged treatment, which are associated with the development of chronic infection. Clinical signs, such as a sinus tract, are pathognomonic of a deep space infection after fracture surgery (▶ Fig. 8.3). 11
8.2.2 Laboratory Tests
Laboratory studies looking for elevated serum inflammatory markers, such as white blood cell count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), should be obtained. It is important to understand that these studies may not provide sufficient specificity but may be used as screening tools. WBC may be elevated in early infection but is often normal in chronic infections. 12 ESR is often elevated for the first 6 months after fracture surgery and therefore has a limited role in the early diagnostic workup. However, due to the high sensitivity of ESR, it may be used as a screening tool. Multiple variables such as poor nutrition, illicit drug use, age, fluid status, smoking, or infection elsewhere may influence the level of ESR. 13
In contrast, CRP is an acute phase reactant with a half-life of 24 to 28 hours and usually normalizes within 2 to 3 weeks after the initial fracture surgery. An elevation after 2 weeks should raise the suspicion for deep infection and is generally more sensitive than ESR. 14
Regular X-rays can be helpful in the later stages for diagnosing chronic infections but is not as useful for diagnosing acute infections. Similar to ESR, conventional radiography is not very specific for diagnosing FRI, but can rule out other causes of pain after surgery. Chronic infections can have multiple radiographic findings, such as hardware failure or loosening, osteolysis, periosteal elevation, or endosteal scalloping (▶ Fig. 8.4). Sequestrum, which is dead sclerotic bone, can often be visualized in the subacute or chronic stages of osteomyelitis. It is defined as an area of calcification within a lucent lesion, completely separated from the surrounding bone. In contrast, an involucrum is periosteal new bone formation around a sequestrum. An intraosseous abscess or Brodie’s abscess can be present in chronic osteomyelitis and radiographically identified as an intramedullary cystic cavity. 15