Thoracolumbar Spine Infections

Overview

Infections of the spine, although uncommon, are extremely destructive and can lead to spinal instability, neurologic damage including paraplegia, and death if not properly treated. Spine infections that involve the vertebrae are called vertebral osteomyelitis. An infection of the disc is called discitis; an infection with pus within the spinal canal is called an epidural abscess. Most often, patients will present with only one or two of these clinical entities, yet some patients present with all three of these entities and are usually extremely ill. Infections of the spine can be caused by bacterial infection, fungus, or tuberculosis. The incidence of pyogenic (bacterial) vertebral osteomyelitis, which is the most common form, is reported to be 1 in 250,000, and occurs most commonly in the region of the thoracolumbar spine.

Causes

The most common cause of spinal infections is the spread of another infection, through the bloodstream, from another part of the body. Urinary tract infections or wound infections are the most frequent originating source of a spinal infection. Spinal infections are much more common in elderly patients, patients with significant medical problems (diabetes, etc), and immunocompromised patients (transplant patients). Initially, the infection begins near the vertebral endplate, where the vascular flow is diminished. Once seeded, the entire endplate becomes infected; the infection then spreads into the disc and to the endplate of the adjacent vertebrae. If the infection goes untreated, it will gradually erode a large portion of the bone away, which may destabilize the spine and compromise the neurologic structures.

Symptoms

Back pain is the most common presenting symptom of patients with a thoracolumbar spine infection. Patients often have unrelenting pain, as well as night pain, that is not relieved by rest or traditional measures. Patients will often have back stiffness and decreased range-of-motion. Patients may have weakness or numbness if the infection is advanced and causing neurologic compression or irritation. In addition, patients may have constitutional symptoms such as low-grade fever, chills, night sweats, fatigue, malaise, and/or loss of appetite, among others.

Physical Findings

The physical findings for patients with a spine infection are limited. Patients may or may not have a fever (Temperature > 101 degrees). Patients may demonstrate tenderness and spasm with decreased lumbar range-of motion. The neurologic examination will generally be normal unless the spinal infection is advanced and causing neurologic compression or irritation.

Imaging Studies

Plain x-rays of the spine will show subtle signs of endplate erosion and destruction, but usually this is not evident in the first 1-3 weeks of a pyogenic infection. The most sensitive imaging test for a spine infection is a magnetic resonance imaging test (MRI) with gadolinium. An MRI test can also define the severity and extent of the infection, and whether it involves the spinal canal (epidural abscess). Spinal infections caused by tuberculosis demonstrate a different radiographic appearance than bacterial infections; tuberculous infections affect the vertebral body primarily and usually do not affect the disc whereas pyogenic vertebral osteomyelitis preferentially destroys the endplate and intervertebral disc. Because tuberculosis of the spine is much less common, especially in the United States, and the radiographic pattern of destruction is often similar to that of a spine tumor or cancer, a thorough work-up to rule out cancer should always be undertaken if this radiographic pattern is encountered.

Laboratory Tests

Laboratory tests are frequently used to diagnose spine infections. A complete blood count (CBC) with differential, a C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are routinely ordered when evaluating for an infection. In many cases, patients will demonstrate an elevated white blood cell (WBC) count. Patients with spine infections who do not have an elevated WBC will almost always have abnormally elevated CRP and ESR tests. Serial laboratory tests can also be used to track whether the infection is being effectively treated with antibiotics. A PPD skin test should also be placed to test for tuberculosis.

Diagnosis

The diagnosis of a spine infection is often delayed, primarily because the early signs and symptoms are subtle and clinicians do not initially suspect it. Patients with "red flags" (symptoms suggesting infection or tumor, such as unrelenting pain, night pain, fevers, chills, night sweats, weight loss, etc) must be appropriately evaluated with imaging and laboratory tests to confirm the diagnosis.

Treatment Options

The treatment of an infection of the thoracolumbar spine depends on the severity of a patient's symptoms and severity of neurologic compression and bony destruction. Patients are initially referred for a fine needle aspiration (FNA) or closed bone biopsy and culture to ascertain the specific type of bacteria that is causing the infection. Patients in whom the biopsy or aspiration fails and the results are indeterminate may be considered for open biopsy. Patients are generally treated with strong antibiotics for 4-8 weeks until the infection is eradicated. Patients are usually indicated for surgical debridement if there is spinal instability, significant deformity, and/or neurologic deficit. A paravertebral abscess causing sepsis, or any sized epidural abscess, is often an indication for emergent surgical intervention. An anterior or posterior decompression and fusion, or combined anterior/posterior surgery, may be utilized depending on where the infection and neurologic compression is most prominent.

Selected Bibliography

Arnold PM, Baek PN, Bernardi RJ, et al. Surgical management of nontuberculous thoracic and lumbar vertebral osteomyelitis: report of 33 cases. Surg Neurol. 1997;47:551.

Buchelt M, Lack W, Kutschera HP, et al. Comparison of tuberculous and pyogenic spondylitis: An analysis of 122 cases. Clin Orthop 1993;296:192.

Caragee EJ. Pyogenic vertebral osteomyelitis. J Bone Joint Surg Am. 1997;79:874.

Emery SE, Chan DK, Woodward HR. Treatment of hematogenous pyogenic vertebral osteomyelitis with anterior debridement and primary bone grafting. Spine. 1989;14:284.

Fang D, Cheung KMC, Dos Remedios IDM, et al. Pyogenic vertebral osteomyelitis: treatment by anterior spinal debridement and fusion. J Spinal Disord. 1994;7:173.

Liebergall M, Chaimsky G, Lowe J, et al. Pyogenic vertebral osteomyelitis with paralysis: prognosis and treatment. Clin Orthop. 1991;269:142.

McGuire RA, Eismont FJ. The fate of autogenous bone graft in surgically treated pyogenic vertebral osteomyelitis. J Spinal Disord. 1994;7:206.

Nussbaum ES, Rockswold GL, Bergman TA, et al. Spinal tuberculosis: A diagnostic and management challenge. J Neurosurg 1995;83:243.

Patzakis MJ, Rao S, Wilkins J Moore TM, Harvey PJ. Analysis of 61 cases of vertebral osteomyelitis. Clin Orthop 1991; 264:178.

Przybylski GJ, Sharan AD. Single-stage autogenous bone grafting and internal fixation in the surgical management of pyogenic discitis and vertebral osteomyelitis. J Neurosurg. 2001;94:1.

Rezai AR, Lee M, Cooper PR, et al. Modern management of spinal tuberculosis. Neurosurgery 1995;36:87.

Rezai AR, Woo HH, Errico TJ, et al. Contemporary management of spinal osteomyelitis. Neurosurgery. 1999;44:1018.

Safran O, Rand N, Kaplan L, et al. Sequential or simultaneous, same-day anterior decompression and posterior stabilization in the management of vertebral osteomyelitis of the lumbar spine. Spine. 1998;23:1885.