summary Adult pyogenic vertebral osteomyelitis, also known as spondylodiscitis, represents a spectrum of spinal infections, including discitis, vertebral osteomyelitis, and epidural abscess Diagnosis is made with MRI with contrast Treatment may consist of long-term targeted antibiotics alone or surgical decompression and stabilization depending on the extent and chronicity of infection, location, and pathogen identification and susceptibility to antimicrobials Epidemiology Demographics usually seen in adults (median age for pyogenic osteomyelitis is 50-60 y/o) Anatomic location 50-60% of cases occur in the lumbar spine 30-40% of cases occur in the thoracic spine ~10% of cases occur in the cervical spine Risk factors include IV drug abuse diabetes recent systemic infection (UTI, pneumonia) malignancy immunodeficiency or immunosuppressive medications obesity malnutrition (serum albumin <3 g/dL is indicative of malnutrition) trauma smoking Etiology Pathophysiology pathogens bacterial Staph aureus most common (50-65%) Staph epidermidis second most common Gram-negative infections increasing over the last decade and often associated with Gram-negative infections of the genitourinary and respiratory tracts pseudomonas seen in patients with IV drug use salmonella seen in patients with sickle cell disease fungal tuberculosis inoculation hematogenous seeding inoculation likely occurs through hematogenous seeding (arterial or venous) of the endplates and intervertebral discs endplates contain an area of low-flow vascular anastomosis that may provide an environment suited for inoculation involvement of one endplate leads to direct extension into intervertebral discs, followed by direct extension into the second endplate direct inoculation can occur after penetrating trauma, open fractures, and surgical procedures contiguous spread from local infection most commonly associated with retropharyngeal and retroperitoneal abscesses neurologic involvement neurologic deficits present in 10-20% results from direct infectious involvement of neural elements compression from an epidural abscess compression from instability of the spine Associated conditions epidural abscess defined as a collection of pus or inflammatory granulation tissue between the dura mater and surrounding adipose tissue epidemiology usually associated with vertebral osteomyelitis present in ~18% of patients with spondylodiscitis 50% of patients with an epidural abscess will have neurologic symptoms psoas abscess Presentation History history of UTI, pneumonia, skin infection, or organ transplant is common Symptoms fever is present in only 33% of patients pain pain is often severe and insidious in onset pain is usually worse with activity and unrelenting in nature pain that awakens patients at night should raise concern for malignancy and infection neurologic symptoms are present in 10-20% radiculopathy myelopathy Physical exam perform a careful neurological exam Imaging Radiographs findings are usually delayed by weeks findings include paraspinous soft tissue swelling (loss of psoas shadow) seen within the first few days disc space narrowing and destruction seen at 7-10 days disc destruction is atypical of neoplasm endplate erosion or sclerosis is seen at 10-21 days local osteopenia CT useful to show bony abnormalities, abscess formation, and extent of bony involvement MRI MRI with gadolinium contrast indications gold standard for diagnosis and treatment determination sensitivity and specificity most sensitive (96%) and specific (93%) imaging modality for diagnosis of spinal osteomyelitis most specific imaging modality for differentiating infection from tumor timing if performed early, findings may be interpreted as degenerative changes repeat MRI may be required to see progression findings include paraspinal and epidural inflammation disc and endplate enhancement with gadolinium T2-weighted hyperintensity of the disc and endplate rim-enhancing lesion Bone scan technetium Tc99m bone scans indications patients who cannot undergo MRI sensitivity and specificity 90% sensitive, but lacks specificity combined technetium Tc99m and gallium 67 scan is both more specific and more sensitive than technetium Tc99m alone indium 111-labeled scan not recommended due to poor sensitivity (17%) Studies Laboratory WBC elevated only in ~50% not a sensitive indicator for early infection ESR elevated in 90% of cases can be monitored serially to track success of treatment; however, is considered less reliable than CRP CRP elevated in 90% of cases can be monitored serially to track success of treatment and is considered more reliable than ESR blood cultures indications all patients prior to antibiotic administration if the organism is unknown identification of the organism is mandatory for treatment sensitivity & specificity least invasive method to determine a diagnosis ~33% (reports show 25-66%) of patients with spondylodiscitis have positive blood cultures when positive, 85% accurate in isolating the correct organism blood culture yield is improved by withholding antibiotics and obtaining cultures when the patient is febrile CT-guided biopsy indications in patients who do not require immediate open surgery and whose blood cultures are negative sensitivity & specificity can provide diagnosis in 68-86% of patients technique can be guided by fluoroscopy or by CT scan cultures should be sent for: aerobic anaerobic fungal acid-fast cultures Open biopsy indications when tissue/organism diagnosis cannot be made with noninvasive techniques technique anterior, costotransversectomy, or transpedicular approaches are used Differential Spinal tumors MRI is the most specific imaging modality for differentiating infection from tumor features that favor infection include: disc space involvement endplate erosion significant inflammation Treatment Nonoperative immediate broad-spectrum antibiotics indications critically ill patients who are septic obtain Gram stains and cultures first, then start antibiotics consider immediate CT-guided aspiration prior to administration of IV antibiotics unable to wait for culture results before starting broad-spectrum antibiotics technique vancomycin for penicillin-resistant and Gram-positive bacteria third-generation cephalosporin for Gram-negative coverage organism-specific antibiotics for 6-12 weeks +/- bracing indications lumbar vertebral osteomyelitis organism must be identified and shown to be sensitive to antibiotics controversial, as some argue that surgical debridement is needed bracing helps improve pain and prevent deformity rigid cervicothoracic orthosis or halo is required for cervical osteomyelitis antibiotics indications once the organism has been identified via blood culture or biopsy technique usually treated with IV culture-directed antibiotics until signs of improvement (~4-6 weeks), then converted to oral antibiotics resistant strains new antibiotic-resistant strains of microorganisms are becoming more common; failure to diagnose can have negative consequences organisms include MRSA (methicillin-resistant Staph aureus) VRSA (vancomycin-resistant Staph aureus) VRE (vancomycin-resistant Enterococcus) treatment newer-generation antibiotics for antibiotic-resistant organisms include linezolid and daptomycin outcomes 80% successful Operative open biopsy alone indications cultures and CT-guided biopsy fail to identify a pathogen lumbar disease without abscess formation in the canal technique can use transpedicular (kyphoplasty-like) approach neurologic decompression, surgical debridement, and spinal stabilization indications cervical vertebral osteomyelitis progressive neurologic deficits progressive deformity & gross spinal instability refractory cases large abscess formation technique dictated by pathologic characteristics anterior debridement and strut grafting +/- posterior instrumentation gold standard posterior debridement and decompression alone usually ineffective for adequate debridement may be indicated in some cases Techniques Anterior debridement and strut grafting +/- posterior instrumentation goals identify the organism eliminate infection prevent or improve neurologic deficits maintain spinal stability techniques strut graft selection autogenous tricortical iliac crest, rib, or fibula strut grafts have proven safe and effective in the presence of acute infection allografts are being used with good results, but autogenous sources theoretically have better incorporation a recent study showed improved deformity correction with titanium mesh cages filled with autograft, followed by posterior instrumentation instrumentation spinal instrumentation in the presence of active infection is controversial some advocate irrigation and debridement followed by staged instrumentation some advocate a single procedure with bone graft and instrumentation in the presence of an active infection titanium is preferred over stainless steel posterior instrumentation posterior instrumentation is indicated in cases of severe kyphotic deformity or when a multilevel anterior construct is required posterior instrumentation can be performed at the same time or as a staged procedure