Necrotizing Soft-Tissue Infections: An Orthopaedic Emergency

Adam Lee, MD; Addison May, MD, FACS, FCCM; William T. Obremskey, MD, MPH

Disclosures

J Am Acad Orthop Surg. 2019;27(5):e199-e206. 

In This Article

Diagnosis

Early diagnosis confirmation is often delayed because of the underestimation or confusion with cellulitis. As mentioned previously, hard signs of NSTI are present in a minority of patients, and thus a high index of suspicion and ongoing vigilance are needed to prevent potentially fatal progression.[3] No one finding or a group of findings has been prospectively validated as a highly sensitive and specific means of confirming the presence or lack of NSTI, and therefore, all objective findings must be considered in the context of the patient's clinical course.[25]

Laboratory Evaluation

Additional laboratory evaluation is useful to stratify presenting findings. Initial workup of a suspected necrotizing infection should include a measure of white blood cell count with differential, platelet count and hemoglobin, sodium, creatinine, blood glucose, albumin, and C-reactive protein (CRP) levels. Blood cultures should be obtained when concern for systemic involvement is raised because this can direct early antibiotic therapy and confirm presence of virulent pathogens. Studies have shown low sodium level, elevated creatinine level, and high white blood cell count were sensitive at predicting NSTI.[24,26] These findings were used along with laboratory values found to be predictive of NTSI in a multivariate regression to develop a scoring system for prediction of necrotizing infections[27] (Table 2). Although this Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score has not been validated in a prospective trial, the components of the score are still useful in addition to the overall assessment and as a prognostic tool.[9,19,28] A study retrospectively comparing a cohort of patients with severe erysipelas subsequently diagnosed with either cellulitis or NSTI found that the overall clinical presentation for each was similar; however, NSTI patients were more likely to have higher pain scores, a higher CRP level, and a higher LRINEC score[29] (Table 2). Another series analyzing vibrio NSTI found severe hypoalbuminemia, thrombocytopenia, and bandemia as a predictor of mortality and suggested that these values be used to direct early surgical intervention.[19] Because of the variability of laboratory data indicative of NSTIs, the use of the LRINEC is surgeon dependent and has never been prospectively validated.

Imaging

Radiographic evaluation may or may not assist in diagnosis of NSTI. Imaging findings are often nonspecific and may not manifest until substantial disease progression has occurred. Further, advanced imaging may delay time to surgical débridement and it should be used judicially in evaluation of equivocal cases. Gas dissecting in facial planes on plain radiograph (in the absence of an open wound) is a hard sign indicative of NSTI although this finding is present in a minority of cases. CT and MRI are advanced imaging techniques that may be considered in the stable patient with nonfocal disease to assess for signs of necrotizing fasciitis (thickening of deep fascia) or deep abscess or necrotic area.[30] MRI is more sensitive at detecting subtle changes in the fascia and deep edema, but acquisition time in most hospitals is longer than that of a CT scan; so again, a thoughtful approach is needed to optimize data gathering while preventing lengthy delay in definitive management. Advanced imaging can be useful to direct surgical approach if no superficial manifestations are present.

Presence of hard signs of NSTI makes diagnosis more certain. Clinical decompensation or progression of infection despite broad antibiotic management with increasing serum lactate, CRP >150 mg/L, or leukocytosis >25,000/mm3are indications for urgent surgical intervention. Diagnosis is formally confirmed with growth of microorganism from cultures taken from deep tissue intraoperatively as discussed later. Diagnosis is confirmed on intraoperative inspection of deep structures. These findings include necrotic tissue and dusky gray appearance of fascia. Microbiologic diagnosis is confirmed with deep tissue cultures with deep tissue samples being submitted to histopathology to aid in confirmation of diagnosis and focused antibiotic management.

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