Overview
The management of spinal infections involves several general considerations. The ultimate goals in management are eradication of the infection, preservation of neurologic function, and prevention of sequelae such as progressive deformity and chronic pain. A systematic approach is used in the diagnosis and treatment of spinal infections; early diagnosis is of the utmost importance, before the onset of neurologic sequelae or spinal instability. These infections are evaluated according to the location, pathogen (bacterial vs. fungal), route of infection (direct inoculation, contiguous spread from an adjacent infection, or hematogenous seeding), age of the patient, and immune status of the host. In the setting of diskitis or spinal osteomyelitis ( Fig. 69-1 ), these goals can often be achieved without operative intervention. A presumptive diagnosis is established by the combination of suggestive laboratory findings, which include elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), along with plain radiographs and advanced imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI). A definitive tissue diagnosis of the offending pathogen can often be made using percutaneous CT-guided biopsy.
After determination of the organism’s sensitivity profile, a 6-week course of the appropriate intravenous (IV) antibiotics is usually sufficient. Bracing is often prescribed as adjuvant treatment to optimize the environment for eradication of the infection as well as for structural stability. Often patients are immunocompromised and/or malnourished; thus a multidisciplinary approach toward treatment with infectious disease and nutritional services is important.
Indications and Contraindications for Surgical Management of Spinal Infection
Indications
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Neurologic deficit from spinal cord injury or progressive root-level deficit
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Significant deformity, instability, or bone destruction/pathologic fracture
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Persistent sepsis or abscess formation
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Inability to identify the offending pathogen by closed methods
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Inability to eradicate the infection by medical management alone
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Intractable pain localized to the involved area of the spine
Contraindications
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Medical comorbidities that make operative intervention prohibitive
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Uncorrected coagulopathies
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Medically stable, immunocompetent patients with early involvement, none of the above indications, and diagnosis made by biopsy
Operative Technique
General Considerations
When surgical treatment is deemed necessary, several concepts appear to be generally accepted:
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Thorough débridement, decompression (if necessary), and establishment or maintenance of spinal stability are critical steps in treatment.
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In most cases, if the microbiologic diagnosis has not been established, preoperative antibiotics should be held until adequate tissue is obtained.
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The location of the lesion is usually anterior; therefore anterior procedures are usually preferred with the exception of selective lower lumbar lesions, in which the neural elements can be safely manipulated to permit anterior débridement and reconstruction.
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Systemic illness and malnutrition are often present and must be addressed concurrently.
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Choice of structural graft. Owing to the attendant morbidity of harvesting large structural autografts (tricortical iliac crest, fibula, and vascularized rib), alternative methods of reconstructing the weight-bearing anterior column are increasingly used. Despite concerns about the risk of sequestration and delayed healing, recent studies have demonstrated good outcomes, and without the aforementioned complications, using both allograft and titanium cages for spinal reconstruction after débridement of active infection.
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Use of recombinant human bone morphogenetic protein (rhBMP). Over the past several years, use of rhBMP has increased in a variety of orthopedic procedures to enhance bone formation. Specifically, it is being used with increased frequency for spinal fusion procedures given its potent osteoinductive properties. Studies thus far have not demonstrated an increase in morbidity or mortality associated with the use of rhBMP in the setting of local infection ; however, such application is off label.
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The use of instrumentation in the infected spine. Concerns have led to the common and effective practice of performing the anterior reconstruction with a strut graft and instrumenting the spine through a separate, posterior approach. Recent studies, however, have demonstrated successful management of pyogenic and granulomatous infections using anterior instrumentation.
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Same-day anterior–posterior versus staged procedures. Some have advocated staging the posterior placement of hardware to prevent “seeding” of the hardware by bacteremia produced by the anterior débridement. Although this advice is well reasoned, it is unclear whether it is necessary. The authors feel that the decision should be made on a case-by-case basis, predicated primarily on the patient’s overall physiologic condition on completion of the anterior procedure.
The techniques for treatment of diskitis and osteomyelitis of the cervical, thoracic, and lumbar spine are generally similar to those used for the anterior treatment of degenerative and traumatic conditions. Because these methods have been described in separate, detailed sections, this chapter will review each technique more generally, and it will highlight important considerations for applying these methods to the management of spinal infections.
Cervical Diskitis and Osteomyelitis
Positioning
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The patient is positioned supine with a bump under the buttocks if autograft harvesting is planned.
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A roll placed between the shoulder blades may facilitate visualization of the lower cervical spine.
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Gardner-Wells tongs may be applied for distraction once the patient has been appropriately positioned. Taping the shoulders with judicious caudal distraction may improve radiographic visualization and increase working space.
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Somatosensory-evoked and transcranial motor-evoked potentials are used when patients’ neurologic function is preserved.
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If the offending organism has not been previously identified, clear instructions to hold preoperative antibiotics are given to the anesthesia team.
Approach
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A left-sided approach is favored by many, although studies have failed to firmly establish an association between the side of approach and the incidence of recurrent laryngeal nerve symptoms.
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Transverse skin incisions are preferred if three or fewer vertebral bodies must be visualized. For more extensive procedures, an oblique incision just anterior to the anterior border of the sternocleidomastoid muscle is used.
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A standard anterolateral approach to the subaxial cervical spine is performed ( Fig. 69-2 ).
Figure 69-2
A standard anterolateral approach to the subaxial cervical spine.
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Location with fluoroscopy should be performed to clearly identify the levels of interest.
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A self-retaining retractor is used with blades placed beneath the elevated medial borders of the longus colli muscle.
Débridement and Decompression
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Great care should be taken to maintain orientation with respect to the midline, because the anatomy in the region of the active infection may be distorted. Exposure of an uninvolved level above and below may be helpful.
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Much of the initial débridement can be performed piecemeal using pituitary rongeurs and curettes. Generous sampling of pathologic material should be sent for Gram stain; culture for aerobic, anaerobic, acid-fast, and fungal organisms; and histologic evaluation.
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The remainder of the decompression is accomplished in standard fashion, with a high-speed burr used to sequentially thin the bone from anterior to posterior. The thin remaining shell of bone is then removed with microcurettes ( Fig. 69-3 ).
Figure 69-3
The thin remaining shell of bone is removed with microcurettes.
Reconstruction
Strut Graft Without Anterior Instrumentation
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To prevent dislodgment, the graft is countersunk into the vertebral bodies above and below.
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A high-speed burr is used to create slots in the bone above and below. The graft is placed in the slot in the superior vertebra first.
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Distraction across the defect using the Caspar distractor alone or in addition to Gardner-Wells tongs is helpful for seating the graft.
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With distraction applied, the graft is rotated and tamped into the slot in the inferior vertebra ( Fig. 69-4 ).
Figure 69-4
With distraction applied, the graft is rotated and tamped into the slot in the inferior vertebra.
Strut Graft with Anterior Instrumentation.
If this technique is selected, grafting is done in the manner previously described for cervical corpectomy. Specifics for applying this technique in the infected spine include the following:
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Preservation of end plate integrity is achieved by gentle preparation with a high-speed burr or rasps and curettes.
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Screws are inserted into uninvolved bone by correlating preoperative imaging with intraoperative findings. Reliance of screw purchase in pathologic bone is not recommended. A preoperative CT scan may be helpful to evaluate bone quality at the levels considered for screw fixation.
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The anterior vertebral body surfaces often undulate with convexities in the peridisk areas. Flattening any anterior prominences with a high-speed burr will allow the plate to sit flush against the bone and decrease the overall profile.
Posterior Instrumentation
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If noninstrumented strut grafting was performed anteriorly, we favor the addition of posterior instrumentation to increase stability of the construct and decrease postoperative immobilization requirements. Posterior instrumentation is also used in most cases of three-level corpectomy owing to concerns of inadequate stability with anterior plating.
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Posterior instrumentation is done using standard techniques described elsewhere in this book. Lateral mass screws are generally used from C3 to C6, and pedicle screws are used caudally at C7 at the end of long constructs, as anatomy permits. Some favor extension of long posterior constructs to the upper thoracic spine.
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If the posterior procedure is performed under the same anesthesia, a separate set-up table of instruments to be used for the posterior procedure is requested in advance and kept separate from instruments used during the anterior stage.
Illustrative Case
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Lateral cervical radiograph of cervical diskitis/osteomyelitis in a middle-aged man with insulin-dependent diabetes ( Fig. 69-5 )
Figure 69-5
Lateral cervical radiograph of a middle-aged man with insulin-dependent diabetes and cervical diskitis/osteomyelitis.
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T2-weighted sagittal MRI ( Fig. 69-6 )
Figure 69-6
T2-weighted sagittal magnetic resonance imaging.
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Postoperative lateral radiograph after anterior débridement and decompression, allograft fibula strut grafting with anterior plating, and posterior lateral mass fixation ( Fig. 69-7 )
Figure 69-7
Postoperative lateral radiograph after anterior debridement and decompression, allograft fibula strut grafting with anterior plating, and posterior lateral mass fixation.
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Postoperative anterior–posterior (AP) radiograph of the same patient ( Fig. 69-8 )
Figure 69-8
Postoperative anteroposterior radiograph.
Thoracic Diskitis and Osteomyelitis
Anesthesia
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The thoracolumbar junction can be approached using standard, two-lung ventilation; higher transthoracic approaches may be facilitated by selected intubation and one-lung ventilation with a double-lumen endotracheal tube.
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An arterial line, central venous line, and Foley catheter are typically placed for continuous blood pressure and fluid status monitoring.
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Somatosensory and transcranial motor-evoked potentials are used when patients have preservation of neurologic function.
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Antibiotics are withheld until specimens are obtained to establish the microbiologic diagnosis.
Patient Positioning
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For anatomic reasons, a left-sided approach is favored by many. The thick-walled aorta can be manipulated with less risk than the thin-walled vena cava. In addition, because of the right-sided location of the liver, less caudal access is available to the thoracolumbar junction without a transdiaphragmatic approach. Midthoracic levels can be adequately approached from either side.
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For anterior approaches to the upper thoracic spine, the patient is positioned supine as described earlier.
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For access to the middle and lower thoracic spine, the patient is positioned in a true lateral decubitus position. Care is taken to stabilize the patient at an angle perpendicular to the floor, using padded attachments to the table or a beanbag and tape ( Fig. 69-9 ).
Related posts:
Craniovertebral Junction Instabilities and Surgical Fixation Techniques
Surgical Approaches to the Craniovertebral Junction in Rheumatoid Arthritis
Anterior and Posterior Cervicothoracic Junction Stabilization Techniques
Percutaneous and Endoscopic Diskectomy
Sacral Screw Fixation and Plating Techniques
Surgical Management of Gunshot Wounds to the Spine
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