Despite advances in surgical techniques, antibiotic therapy, and diagnosis, infection remains a difficult problem that can compromise the results of foot and ankle surgery. Miller 31 reported infections in 2.2% of 1841 patients after inhospital foot and ankle surgery, and Stevens 41 reported a 5.3% infection rate. Hugar et al 21 reported infections in 1.35% of patients after outpatient foot surgery. The influence of managed care has increased the importance of the economic impact of infections after surgery. The emergence of multiple-drug resistant organisms additionally complicates the treatment of these infections. A high index of suspicion and early and aggressive treatment can help limit the severity of complications caused by infection after foot and ankle surgery but the cornerstones of treatment are prevention of iatrogenic and nosocomial infections.
Careful patient selection is critical in the prevention of infection after surgery. Patients with some systemic conditions, such as poorlycontrolled diabetes and peripheral vascular disease, and patients who are steroid-dependent are at higher risk for having infection develop after surgery. Medical evaluation and vascular screening with Doppler ultrasound before surgery may be indicated to help identify patients at risk. 4 Cessation of smoking and improvement of nutrition also can help decrease the risk of infection after surgery.
Proper surgical technique, including skin preparation, draping, and surgical scrub, is important in preventing infection. 40 The length of the surgical procedure also is a factor: the longer the procedure, the greater the risk of contamination.
Soft Tissue Infections
Cellulitis is common after foot and ankle surgery, and its clinical appearance varies according to the overall health of the patient, the causative factors, and the infecting organism. It is important to distinguish a superficial infection from one that involves the deeper soft tissue envelope and possibly the joint or bone. With a superficial infection, the skin is warm, tender, and erythematous, but joint motion is painless. Occasionally lymphangitis or lymphadenopathy is present. The area is tender to palpation, but is not fluctuant. Leukocyte count and temperature may be increased. The most common causative organisms in uncompromised hosts are Staphylococcus aureus and B-hemolytic Streptococci. Usually 5 to 7 days of oral antibiotic treatment with agents such as dicloxacillin, cephalexin, clindamycin, more broad-spectrum cephalosporins, and fluoroquinolones is sufficient treatment for cellulitis. If the cellulitis is resistant to broad-spectrum antibiotics, therapy should be based on culture results. Surgical drainage, soaks, and elevation also may be required. 10
Deep infections with abscess formation are a serious complication of foot and ankle surgery. Patients who are immunocompromised are at a higher risk for having deep infections develop after surgery. A high index of suspicion and aggressive treatment are necessary to salvage the lower extremity. In patients with deep infections, the skin is warm, tender, swollen, and possibly fluctuant. White blood cell count and temperature may be increased. Plain radiographs, magnetic resonance imaging (MRI), and needle aspiration are helpful in making the diagnosis. Surgical debridement and broad-spectrum antibiotic therapy are the initial treatment. Once the infecting microorganism is identified, the antibiotic should be changed accordingly.
The technique for surgical drainage is based on obtaining adequate decompression of the exudative compartments. Threeincision 26 and five-incision 24 techniques have been described for exposure of deep infections of the foot. Extensive irrigation and debridement often is required to remove infected tissue adequately, and multiple irrigation and debridement procedures may be necessary to eradicate the infectious material. Placing drains and packing in open wounds allows drainage of the abscess while the wound begins to heal.
Infections after surgery are more common after traumatic injuries than after elective surgical procedures, because traumatic injuries are contaminated with microorganisms that are on the skin or are introduced at the time of injury. Seventy percent of open fractures are contaminated at the time of injury, 2 most commonly by Staphylococcus aureus. Tissue destruction and devascularization associated with the traumatic injury may hinder the body’s infection-fighting mechanism. Infection is the most important factor in the development of nonunion, loss of function, and other complications after foot and ankle trauma, and prevention of infection is essential to obtaining bony union and soft tissue coverage that result in a functional plantigrade foot. 6 The standard principles of wound irrigation and debridement are the basics of preventing infection after trauma. Antibiotic coverage is based on the severity of the soft tissue injury and the grade of open fracture. 8,19 Preventing infection can be difficult in patients with multiple injuries. Prophylactic measures include determining nutritional needs and appropriate antibiotic coverage and prevention of stress bleeding, venous thrombosis, and pressure sores. 42
In addition to the microorganisms introduced at the time of trauma, internal fixation of a fracture in the foot and ankle allows for possible bacterial invasion and causes changes in the surrounding cells. 34 Many types of bacteria, including Staphylococcus, can adhere to the implant, forming a glycocalyx that makes them resistant to the normal immune response and to antibiotics. 5,16–18 Internal fixation, however, is critical to provide fracture stability for union and can help prevent infection. 27,45 Animal models have shown that contaminated fractures treated without internal fixation had a higher rate of clinical infection than similar fractures treated with internal fixation. 30,45
The risk of infection after internal fixation of open or closed fractures can be decreased by the use of antimicrobial prophylaxis and proper surgical technique that includes minimal soft tissue stripping during placement of the implant. 45 Irrigation and debridement, stable fracture fixation, and early soft tissue reconstruction are keys to preventing infection after open fractures.
According to McNeur, 29 “There is one thing worse than a stable infected fracture and that is an unstable infected fracture.” If the infection is acute and the soft tissues are viable, the implant can be retained as long as fracture healing is progressing. Patients with chronic infections after internal fixation may require implant exchange or removal. 36
Necrotizing fasciitis is characterized by rapidly progressive necrosis and edema of the subcutaneous fat and fascia that can result in toxemia and death. Affected patients may have septic shock, end organ failure, and loss of limb or life. Patients who are immunocompromised, such as those with human immunodeficiency virus infections, diabetes mellitus, and alcoholism, are at increased risk for necrotizing fasciitis. 10 Group A-beta hemolytic Streptococcus pyogenes is the most common causative organism 28 but the infection may be caused by multiple organisms. Vibrio vulnificus is a rare cause of necrotizing fasciitis found in coastal sea water. 47
Clinical signs of necrotizing fasciitis include tense edema and erythema that do not respond to antibiotics or elevation. Patients appear toxic and usually febrile. 20 Crepitus of the skin may be palpable because of the subcutaneous emphysema caused by gas gangrene. The wound often appears benign even though the deep infection is extensive. The incubation period can range from a few hours to a few days and has been reported to be as long as 2 weeks after surgery. 32 Several types of toxins have been identified in necrotizing fasciitis.
These toxins function by enzymatic breakdown of membranes or by increasing the permeability of the vascular endothelium. 39 The most important risk factor in mortality from necrotizing fasciitis is a delay in diagnosis and treatment. Mortality rates have been reported to decrease significantly when surgery is done within 24 hours of recognition of the condition. 10
Wide surgical debridement and irrigation with the application of appropriate antibiotics are the mainstays of treatment. 10 Any sutured wounds should be opened widely and debrided, and antibiotic therapy should be administered immediately. 32 Occasionally, amputation is necessary to rid the area of infection and prolong the patient’s life. A guillotine amputation may be required to aid in drainage and multiple debridements.
Joint infections are uncommon after foot and ankle surgery. Ferkel et al 7 reported only six superficial infections and two deep infections after 612 arthroscopic ankle procedures. Antibiotics, good surgical technique with careful handling of the soft tissues, removal of devitalized tissue (when fusion is done), and prevention of hematoma formation can help decrease the risk of joint infection after surgery.
Infections involving the foot and ankle are manifested by increased pain with joint motion, severe swelling, and sometimes drainage. 10 Patients usually have an increased leukocyte count, sedimentation rate, and fever. Plain radiographs, MRI, and aspiration can be helpful in making the diagnosis. Prompt treatment with irrigation, debridement, and antibiotics is required. Severe joint space infections cause marked fibrosis and destructive arthritis. The prognosis of patients with joint infections after surgery is based on the duration of the infection before treatment, the organism involved (patients with gram negative infections have a worse prognosis than those with gram positive infections), preexisting joint disease, host competence, and the joint involved. 13
Infection involving joint implants in the foot ankle remains a complication of their use. Aseptic technique, delicate soft tissue handling, and perioperative antibiotics are important in prevention of this complication. Coagulase-positive Staphylococcus is the most common organism isolated from infected implants. The diagnosis is similar to other joints with infection involving implants. Once the diagnosis is made, removal of the implant, 6 weeks of antibiotic therapy, and arthrodesis after eradication of the infection offer the best chance for a successful result. 37
Bone infections after foot and ankle surgery can be difficult to diagnose and treat. Fever, local pain, edema, exudative drainage, and elevated leukocyte count and sedimentation rate are typical findings. Radiographic changes may include a rounded lucent area surrounded by sclerotic bone, with nearby cortical and periosteal thickening. 9 Magnetic resonance imaging and indium-labeled leukocyte scintigraphy are helpful to define the extent of the infection. 33 Definitive diagnosis is made by direct observation or biopsy. 10
Surgical treatment of patients with osteomyelitis consists of debridement of all necrotic and infected tissue and appropriate antibiotic therapy. Treatment also may include the use of antibiotic-impregnated methylmethacrylate beads, local or vascularized soft tissue flaps, autogenous bone grafts, or vascularized bone grafts once the infection is eradicated. 1
Thordarson et al 43 described successful treatment of five patients with septic ankles and tibial osteomyelitis. Their protocol included radical soft tissue and bone debridement, soft tissue transfer, intravenous antibiotics, and delayed ankle fusion. Fusion was complete at an average of 3.5 months and at an average followup of 27 months, all five patients were free of infection. Thordarson et al 43 suggested that the vascularized muscle transfer increased the host defenses and decreased the dead space.
Bishop et al 3 reported successful fusion in four of six patients treated with free vascularized bone grafts and ankle fusion for reconstruction of segmental bone loss caused by osteomyelitis. Two below-knee amputations were required for recurrent infection in one patient and nonunion in the other patient. Isenberg et al 22 reported good results after subtotal calcanectomy for osteomyelitis of the calcaneus.
Myobacterial and Fungal Infections
Mycobacterium tuberculosis infection is rare after foot and ankle surgery. Radiographs may show subchondral osteoporosis, areas of bone destruction, thickening of periosteum, and cartilage destruction. 13 A biopsy of the synovium or bone usually is necessary to make the diagnosis. 44 A positive skin test and manifestations of tuberculosis somewhere in the body are helpful indications of the diagnosis. Culture and sensitivity testing is important in patients with drug-resistant tuberculosis. Therapy with two or more antitubercular drugs for at least 9 months usually is curative. Surgery is reserved for patients with joint instability after chemotherapy is completed. 10
Atypical myobacterial postoperative infections also are rare. Patients with acquired immunodeficiency syndrome are at increased risk for Myobacterium avium-intracellulare infections, and patients who work with marine life may be infected with Mycobacterium marinum. The diagnosis and treatment are similar to those for typical mycobacterial infections. 46
Fungal infections rarely occur after surgery, but can be present at the time of surgery. Skin lesions can be treated with standard antifungal medications. Coccidioides immitis and Cryptococcus neoformans can involve deeper tissues, including bones and joints. The diagnosis usually is made by bone biopsy. Treatment includes surgical debridement and administration of amphotericin. 14
Infections in Patients With Diabetes
Infections after foot and ankle surgery in patients with diabetes mellitus are frequent and can be disastrous. Any surgical procedure planned for a patient with diabetes should consider the risk-to-benefit ratio. An infected foot is one of the most common reasons patients with diabetes are admitted to a hospital. Flynn et al 8 reported that the infection rate in patients with diabetes who are treated for ankle fractures was twice that of patients without diabetes. The incidence of amputation in patients with diabetes is 40 times that in patients without diabetes. 15 The pathophysiology of infection in patients with diabetes is well-documented. 10,11,35
The most common gram positive organisms in foot infections in patients with diabetes are Staphylococcus aureus, Staphylococcus epidermidis, group-B Streptococcus and Enterococci. Gram negative organisms may include Proteus, Escherichia coli, and Pseudomonas. Bacteroides is the most common anaerobic organism. 11
The clinical presentation of infection in patients with diabetes is unlike that of other infections. Two thirds of patients do not have a fever of more than 38° C (100° F), and ½ do not have leukocytosis. Diabetic immunosuppression often obscures the severity of the underlying infection. 35 Superficial cultures usually are not necessary and often overrepresent the pathogens. Empiric therapy with broadspectrum antibiotics has been shown to be as effective as culture-specific treatment. 10,11,35 Bone biopsy or deep cultures should be reserved for surgical treatment or when empiric therapy is unsuccessful. 35
Imaging is helpful for the diagnosis of osteomyelitis and deep abscess formation. Magnetic resonance imaging and technetiumlabeled bone scanning combined with 111-leukocyte scanning are the best modalities. Magnetic resonance imaging can better define the abscess cavity and bone marrow involvement than the combined nuclear medicine scans, but MR imaging often indicates a falsely large area of bone involved in osteomyelitis. Johnson et al 23 concluded that if radiographs are negative in a patient with diabetes who is suspected of having osteomyelitis, a negative indium-111 scan alone rules out infection. If the indium-111 scan is positive, a technetium-99m scan differentiates osteomyelitis from soft tissue infection.
Patients with diabetes who have mild infections after surgery can be treated with oral antibiotics, local wound care with dressing changes, and pressure relief. Frequent followup visits are necessary to monitor the response of the infection to antibiotics. If there is no response, another oral antibiotic or intravenous antibiotic administration should be considered. More severe infections usually are caused by a combination of gram positive and gram negative aerobes and anaerobes, and intravenous antibiotics are essential. Consultation with an infectious disease specialist is helpful in determining the type and duration of antibiotic. Antibiotic therapy generally includes ampicillin, sulbactam, ticarcillin-clavulanate, piperacillin-tazobactam, or fluocinolone with clindamycin (for patients who are allergic to penicillin). Patients with abscesses and necrotic bone should be treated surgically. Occasionally, amputation is necessary to eradicate infection, preserve function, and prolong the patient’s life. 10,35 Education is an important part of the treatment of infections in patients with diabetes, and a team approach, including the orthopaedist, vascular surgeon, internist, orthotist, and wound care specialist, often is helpful.
A wide variety of antibiotics can be effective in the treatment of patients with foot and ankle infections (Tables 1, 2). Given the complexity of microbial resistance patterns, cost considerations, adverse drug reactions, and drug interactions, consultation with an infectious disease specialist is advisable.
A few general guidelines can be helpful in choosing the appropriate antibiotic: (1) First and second generation oral cephalosporins have suboptimal effectiveness in the treatment of patients with serious gram positive infections; (2) Older quinolones, such as ciprofloxacin, do not have a role in the treatment of patients with gram positive or anaerobic infections, and the role of newer quinolones such as levofloxacin in the treatment of patients with Staphylococcal infections is unclear; (3) Vancomycin is not an especially potent antistaphylococcal antibiotic, but it is the gold standard of treatment of patients with methicillin-resistant Staphylococcus aureus infections; its nephrotoxicity has been overemphasized. Vancomycin, however, should be used only in specific situations (Table 3). Vancomycin overuse has been shown to be a risk factor for infection and colonization with vancomycin-resistant Enterococcus and may increase the possibility of the emergence of vancomycin-resistant Staphylococcus aureus 12; and (4) The role of coagulase-negative Staphyloccocal infection in the foot and ankle is minimal in the absence of a foreign body. Even with a foreign body, a culture positive for this species of microbe may not represent true infection but may be attributable to contamination.
The emergence of multidrug resistant organisms, such as methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, and vancomycin-resistant Enterococcus have necessitated the development of new antimicrobials. 12 Streptogramins are a new class of antibiotics that have two chemical compounds that act to inhibit bacterial protein synthesis. The synergistic combination of these compounds allows the streptogramins to be less susceptible to organism resistance. Clinically, these antibiotics have been shown to be effective against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. 25 Teicoplanin is a new semisynthetic antibiotic reported to be as successful as, or more so, than vancomycin with less toxicity. It is a glycopeptide antibiotic that binds the epetidoglycan precursor terminus. 38
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Osaretin B. Idusuyi, MD; and G. James Sammarco, MD, Guest Editors© 2001 Lippincott Williams & Wilkins, Inc.