Posttraumatic Reconstruction of the Foot and Ankle in the Face of Active Infection




Posttraumatic infection of the foot and ankle is a challenging issue for orthopedic surgeons. Making the diagnosis often requires combining laboratory and radiologic testing, patient examination, and history. Patient comorbidities should be identified and optimized whenever possible. Treatment must combine effective antibiotic therapy with thorough debridement of the infected zone. Reconstruction often requires a 2-staged approach using antibiotic spacers and temporary external fixation, with the goal of obtaining a functional, pain-free limb that is free of infection.


Key points








  • Many options exist in the treatment of posttraumatic infection in the foot and ankle.



  • Making the diagnosis often requires combining laboratory and radiologic testing, patient examination, and history.



  • Antibiotic and surgical treatments should be tailored to individual patients based on the nature of their injury, extent of infection, comorbidities, and overall functional expectations.






Introduction


Posttraumatic infection of the foot and ankle is a challenging issue for orthopedic surgeons. Whether infection sets in as a result of the initial severe soft tissue injury or as a postoperative complication, clearing infection to allow successful reconstruction can be frustrating. Patient factors must be taken into account to determine the best approach for treatment. Thorough debridement is paramount followed by appropriate antibiotic treatment to clear the infection. Reconstruction can then be individualized based on host factors, type of injury, extent of bone or soft tissue loss, and patient expectations. Despite appropriate surgical and antibiotic treatment, the long-term recurrence rate for chronic osteomyelitis is about 20%.




Introduction


Posttraumatic infection of the foot and ankle is a challenging issue for orthopedic surgeons. Whether infection sets in as a result of the initial severe soft tissue injury or as a postoperative complication, clearing infection to allow successful reconstruction can be frustrating. Patient factors must be taken into account to determine the best approach for treatment. Thorough debridement is paramount followed by appropriate antibiotic treatment to clear the infection. Reconstruction can then be individualized based on host factors, type of injury, extent of bone or soft tissue loss, and patient expectations. Despite appropriate surgical and antibiotic treatment, the long-term recurrence rate for chronic osteomyelitis is about 20%.




Patient evaluation: making the diagnosis


Often the presence of infection is clear with draining sinuses or wounds, erythema, or radiographic evidence of osteomyelitis. Other times the diagnosis may be more elusive. Imaging and laboratory studies as well as tissue cultures are included in the standard workup for infection.


Laboratory Testing


Laboratory values can be helpful but are nonspecific. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and white blood cell (WBC) levels should be obtained first. These tests are nonspecific but have been reported to have a sensitivity and specificity greater than 90% for the diagnosis of osteomyelitis, especially when used in combination. Serum procalcintonin is a newer additional test with a high specificity for bacterial infection, which can be helpful for both diagnosing infection and monitoring treatment. Procalcitonin has been studied in acute osteomyelitis and septic arthritis in all age ranges and has been found to be a sensitive and specific marker at a cutoff of greater than 0.4 mg/mL.


Imaging Studies


Radiographs


Plain radiographs are generally obtained first. In the presence of acute osteomyelitis, radiographs may be negative because radiographic signs of infection are not visible for about 2 weeks after the onset of infection. With more chronic infection, sclerotic bone may be present surrounding an infectious sequestrum. Cortical destruction may also be present. In the setting of posttraumatic infection, radiographs can be helpful to evaluate the traumatic bone injury, presence of nonunion, and extent of bone resorption to plan for surgical debridement and reconstruction. Comparing current radiographs to past and future radiographs can help to follow the progression of treatment as well.


Computed tomography


Computed tomography (CT) scans best demonstrate cortical destruction, periosteal reactions, and sequestrum. Limitations include image degradation by streak artifact when metallic hardware is present and poor soft tissue and bone marrow resolution. CT scans can be helpful when planning reconstruction, however, due to their 2- and 3-dimensional imaging capabilities that allow for better defining bone injury, presence of nonunion, and spatial relationships.


MRI


MRI is often the imaging option of choice for diagnosing osteomyelitis due to its early diagnostic capability. MRI can show bone marrow edema after only 1 to 2 days of onset of bone infection. MRI has a sensitivity in diagnosing osteomyelitis of 82% to 100% and a specificity of 75% to 96%. MRI can be helpful in showing abscess formation, sinus tracts, and soft tissue inflammation as well. MRI, however, is less helpful in the posttraumatic patient due to signal changes from the injury itself and susceptibility artifact from hardware.


Nuclear imaging


Nuclear imaging can provide a more specific evaluation for osteomyelitis without being compromised by the presence of hardware. The standard triple phase bone scan has a high sensitivity for identifying osteomyelitis in nonviolated bone. However, increased osseous tracer uptake is noted in trauma or previous surgery, which decreases the usefulness of this test in the posttraumatic setting. The nuclear medicine test of choice for these patients is a white cell scan in which the patient’s WBCs are labeled with either Indium-111 or Tc 99m -HMPAO, before being intravenously returned to the patient. These labeled white cells have increased uptake in infected bone. The WBC scan is combined with a standard bone marrow scan to differentiate from normal physiologic marrow uptake. When a WBC tagged scan is combined with a bone scan, the specificity is 80% to 90%. Chronic or partially treated osteomyelitis can have false negative results.


Deep Tissue or Bone Culture


The best way to diagnose osteomyelitis remains a deep bone biopsy. A positive culture provides a high level of specificity in the diagnosis of osteomyelitis. However, cultures have a low sensitivity with only 40% to 60% of patients with infection showing positive culture results. Multiple intraoperative tissue samples encompassing the entire zone of infection should be obtained at debridement.




Initial treatment




  • 1.

    Thorough debridement(s) to remove all nonviable tissue


  • 2.

    Effective antibiotic treatment


  • 3.

    Address patient-specific factors that may impede healing



Debridement


Upon diagnosis of infection, the patient should undergo thorough debridement to remove all evidence of necrotic tissue. Bone should be debrided until healthy-appearing bleeding bone remains and all sequestrum is removed. Multiple debridements may be required until no macroscopic sign of infection is present. If hardware is present in the infected area, it should be removed if loose or unstable or if the bone is well healed. If the hardware is stable and the bone is nonunited, then the hardware may be left in place until the bone is healed. Retaining hardware can reduce cure rates, however, due to biofilm formation. In the presence of retained hardware, greater treatment success can be expected for patients infected with a single, less virulent organism compared with a more aggressive or multiple organisms ( Fig. 1 ).




Fig. 1


Treatment of the infected posttraumatic foot or ankle. Patients with active infection require serial debridements and appropriate antibiotic therapy. Hardware that may be present from previous surgeries may be removed. External fixators as well as antibiotic spacers may be used on a case-by-case basis.


Antibiotic Treatment


With extensive deep infection or osteomyelitis, obtaining the assistance of an infectious disease specialist can be very helpful for optimizing antibiotic treatment. Antibiotic treatment options and duration should be patient specific and culture directed. Polymicrobial infections are common in the foot and ankle, especially in those with diabetes, vascular disease, or immunocompromised patients. Staphylococcus aureus is a very common pathogen in the foot and ankle, occurring in around 80% of infected patients in one study. In this same study, Pseudomonas aeruginosa was a common primary or second infectious agent in 75% of patients, most commonly affecting diabetics. This information should be taken into account when initial empiric antibiotics are chosen. ESR levels can be used to guide the duration of antibiotic treatment. Once normalized, consideration is turned to definitive operative treatment.


Patient-Specific Factors Affecting Healing/Treatment


Often, patient factors are out of the control of the treating orthopedic surgeon but can have a profound effect on treatment outcome. These factors should be part of the decision-making algorithm and should be optimized at the onset of treatment when possible ( Box 1 , Fig. 2 ).



Box 1





  • Diabetes



  • Peripheral vascular disease



  • Tobacco use



  • Obesity



  • Malnutrition



  • Vitamin D deficiency



  • Wounds/soft tissue loss



  • Immunosuppression



Comorbidities affecting healing



Fig. 2


Comorbidity algorithm. Many patients may have more than one comorbidity, which should each be addressed individually to better account for all patient risk factors.


Diabetes


Diabetic patients have a known higher risk of postoperative complications, including infection and impaired wound healing. Patients with poor glycemic control should be counseled regarding their risk. Foot and ankle patients with a glycosylated hemoglobin (HgbA1c) level greater than 8% have a 2.5 times increased risk of developing infection. Tight glucose control is imperative in improving outcomes in these patients. Patients with a fasting glucose level of greater than 140 mg/dL on the morning of surgery are 3 times more likely to develop infection than those with glucose levels less than 140 mg/dL.


The presence of neuropathy also complicates the postoperative period by increasing the rate of infection and prolonging healing times. Postoperative infection is greater than 5 times more likely in patients with neuropathy.


Peripheral Vascular Disease


When peripheral pulses are diminished, blood flow may not be adequate to allow for healing of the tissues or clearance of the infection. Patients with peripheral arterial disease are 3 times more likely to develop postoperative infections after foot or ankle surgery than those without vascular disease. Box 2 lists vascular factors that indicate higher potential for wound healing in patients with vascular disease. In patients who do not meet these criteria, vascular surgery consultation is recommended. If the patient is a candidate, revascularization can aid in healing the reconstruction or offering a more distal amputation level if this route is chosen.



Box 2





  • Ischemic index greater than 0.5



  • Transcutaneous oxygen tension greater than 30 mm Hg



  • Toe pressure greater than 40 mm Hg



  • Ankle-brachial index greater than 0.45



Factors favoring wound healing


Tobacco use


Active tobacco users are twice as likely to develop postoperative infections after foot or ankle surgery when compared with non-tobacco users. Tobacco use can impede skin healing and bone union. Counseling on smoking cessation should be done early in the treatment process to improve healing capability. Smoking cessation options include oral medications or nicotine replacement products, referral to smoking cessation support networks such as 1-800-quit-now, or referral to a primary care provider.


Malnutrition


Malnutrition poses a serious risk to primary wound healing as well as any potential flap procedure that may be required for soft tissue or bone coverage. An albumin level less than 3.0 g/dL is a poor prognostic indicator for potential wound healing. Consider checking protein, albumin, and prealbumin levels in patients with evidence of poor healing or suspected malnutrition. Improving protein levels can aid in soft tissue and bone healing. Vitamin C (500 mg daily) and a multivitamin are helpful as well.


Soft tissue loss/wounds


Wound management is essential in any traumatic situation, but becomes ever more important in the face of concomitant infection. The soft tissue envelop must provide adequate coverage over bone and hardware with potential to heal. Ultimately, the size and depth of the defect, type and volume of deficient tissue, availability of anastomosing vessels, and donor site condition determine options available for soft tissue reconstruction ( Fig. 3 ).


Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Posttraumatic Reconstruction of the Foot and Ankle in the Face of Active Infection
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