Approach Considerations
The combination of mechanical compression of the spinal cord by pus or granulation tissue can result in ischemia with spinal cord infarction, which accounts for the rapid neurologic progression of this disease. Patients with a spinal epidural abscess may progress to complete paralysis within minutes to hours, even while receiving optimal antibiotic therapy. In addition, patients with vertebral osteomyelitis can develop pathologic fractures, caused by the softening of the bone, and present with acute spinal cord compression.
Most patients with pyogenic vertebral osteomyelitis respond to medical management. However, surgery may be required if medical management is unsuccessful. [74] Indications for surgery include the following:
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Significant osseous involvement
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Neurologic deficits - Neurologic deterioration can be caused by significant kyphosis, by infection behind the vertebral body under the posterior longitudinal ligament, or by infection in the epidural space
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Septic course with clinical toxicity from an abscess not responding to antibiotics
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Failure of needle biopsy to obtain necessary cultures
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Failure of intravenous (IV) antibiotics alone to eradicate the infection
The Infectious Diseases Society of America (IDSA) has published clinical practice guidelines for the treatment of native vertebral osteomyelitis (NVO) in adults (see Guidelines). [59]
Removal of hardware with irrigation and debridement in patients with surgical-site infections (SSIs) is performed commonly. However, the removal of hardware from patients with SSIs after spinal procedures is controversial. [75] Moreover, new spinal infections with spinal cord compression or biomechanical instability may require instrumentation [76, 77, 78] along with surgical debridement. In these patients, topical placement of antibiotic-impregnated beads, which allow slow release of antibiotics, may be beneficial.
There has been a growing emphasis on the use of newer minimally invasive surgical approaches to treat spinal infections. [79, 80]
Medical Therapy
The overall treatment plan for a patient with vertebral osteomyelitis must be individualized according to the patient's general medical condition, [54, 55, 81, 82] his or her neurologic status, the presence of large associated abscesses, and biomechanical factors. Underlying infections (eg, retropharyngeal, pelvic, decubital) must be treated simultaneously if the vertebral infection is to be cured. A multidisciplinary approach is very important. [41, 83, 84]
Antibiotic treatment must be tailored to the isolated organism and any other sites of infection. Broad-spectrum antibiotics covering both gram-positive and gram-negative organisms, aerobes and anaerobes (including methicillin-resistant S aureus [MRSA]), are administered initially until the organism is isolated. Most cases of vertebral osteomyelitis are caused by S aureus, which generally is sensitive to antibiotics. Although rare, spinal tuberculosis or fungal infection must be considered in the face of persistently negative culture findings and lack of response to antibiotics. [4, 85, 86]
Antibiotics are given for variable lengths of time. It appears that 6-8 weeks of parenteral antibiotic therapy is effective in most cases [85, 86] Before parenteral antibiotics are discontinued, the erythrocyte sedimentation rate (ESR) should have fallen to at least two thirds of the pretherapy level. In addition, the patient should be afebrile, without pain on mobilization, and without any disease-related complications such as neurologic deficits.
A persistently high ESR implies continuing infection, and additional IV antibiotics are indicated. In such an instance, an additional biopsy can be taken of the infected vertebra to see if organisms not susceptible to the chosen antibiotics are present. [60, 62]
Bracing is recommended to provide stability for the spine while the infection is healing. The goal of immobilization is to provide opportunity for the affected level to fuse in an anatomically aligned position. Bracing is usually continued for 6-12 weeks, until either bony fusion is seen on radiographs or the patient's pain subsides. A rigid brace works best and need be worn only when the patient is active.
After successful conservative treatment of pyogenic vertebral osteomyelitis and eventual union, some degree of vertebral body collapse may still occur. The greater the amount of bone destruction present before treatment, the greater the likelihood of eventual kyphosis. After antibiotic treatment, therefore, the spine must be monitored with sequential radiographs. Kyphosis formation may lead to eventual neural impingement, and the kyphosis itself may require late surgical correction.
Medications
Vancomycin is a potent antibiotic that is directed against gram-positive organisms and is active against Enterococcus species. It is useful in the treatment of bloodstream infection and skin-structure infection and is indicated in patients who cannot receive or have failed to respond to penicillins and cephalosporins or have infections with resistant staphylococci.
To avoid toxicity, it is recommended to assay vancomycin trough levels after the third dose is drawn one half hour before the next dose. Creatinine clearance (CrCl) should be used to adjust the dose in patients diagnosed with renal impairment. Vancomycin is used in conjunction with gentamicin for prophylaxis in patients who are allergic to penicillin and are undergoing gastrointestinal (GI) or genitourinary (GU) procedures. The adult dosage is 0.5-2 g/day IV; the pediatric dosage is 40 mg/kg/day IV. Vancomycin is a pregnancy category C drug.
Nafcillin is the initial therapy for suspected penicillin G–resistant streptococcal or staphylococcal infections. Parenteral therapy should be provided initially in severe infections, then switched to oral therapy as the patient’s condition warrants. Because of the risk of thrombophlebitis, particularly in elderly patients, parenteral administration should continue for only a short period (1-2 days) before being changed to the oral route as clinically indicated.
Adult dosing of nafcillin is 1 g IV or intramuscularly (IM) every 4-6 hours. Neonatal dosing (0-4 kg) is 10 mg/kg IM every 12 hours. Dosing in children who weigh 4-40 kg is 25 mg/kg IM every 12 hours or 50 mg/kd/day orally in four divided doses or, alternatively, 100-200 mg/kg/day IV/IM in four or six divided doses. Nafcillin is a pregnancy category B drug.
Gentamicin is an aminoglycoside antibiotic that has gram-negative coverage. It is used in combination with both an agent against gram-positive organisms and one that covers anaerobes. Gentamicin may be considered if penicillins or other less toxic drugs are contraindicated, when clinically indicated, and in mixed infections caused by susceptible staphylococci and gram-negative organisms. Dosing regimens are numerous; the dosage should be adjusted on the basis of CrCl and changes in volume of distribution. Gentamicin may be given IV or IM.
In adults, dosing of gentamicin for serious infections and normal renal function is 3 mg/kg IV every 8 hours. The loading dose and the maintenance dose are 1-2.5 mg/kg IV and 1-1.5 mg/kg IV, respectively, every 8 hours. The extended dosing regimen for life-threatening infections is 5 mg/kg/day IV/IM every 6 or 8 hours. Each regimen is followed by at least a trough level drawn on the third or fourth dose (30 minutes before dosing); a peak level may be drawn 30 minutes after a 30-minute infusion.
In children younger than 5 years, gentamicin dosing is 2.5 mg/kg IV/IM every 8 hours. In those older than 5 years, dosing is 1.5-2.5 mg/kg IV/IM every 8 hours or 6-7.5 mg/kg/day in three divided doses, not to exceed 300 mg/day, monitored as in adults.
Ceftazidime is a third-generation cephalosporin with broad-spectrum gram-negative activity. It has lower efficacy against gram-positive organisms and higher efficacy against resistant organisms. Ceftazidime arrests bacterial growth by binding penicillin-binding proteins. Adult dosing is 1-2 g IV/IM every 8 or 12 hours. Neonatal dosing is 30 mg/kg IV every 12 hours. In infants and children, dosing is 30-50 mg/kg IV every 8 hours, not to exceed 6 g/day. Ceftazidime is a pregnancy category B drug.
A multicenter retrospective cohort study by Watkins et al evaluated ceftaroline, an advanced cephalosporin with activity against MRSA, against a comparator antibiotic in the treatment of spinal infections. [81] There were no significant differences between the two groups in terms of clinical success, and side effects and toxicities were rare. The investigators concluded that ceftaroline appeared to be safe and effective for treating spinal infections, including those caused by MRSA.
Surgical Therapy
Although most patients with pyogenic vertebral osteomyelitis respond to medical management, surgery may be required (see Approach Considerations). [4, 87, 88, 49, 50, 51, 52, 53, 89, 90, 91] Predictors of the need for surgical invention at initial presentation of spinal infection include the presence of epidural abscess, involvement of the cervical or thoracic spine, and an increasing number of spinal levels involved. [92]
Goals of surgery include preservation of neural function and achievement of stable bony fusion without severe kyphosis, which itself could lead to neural compromise or disabling radicular pain.
Preparation for surgery
Most patients who need to undergo a surgical procedure for the treatment of a vertebral infection are chronically debilitated and require a careful preoperative evaluation, including a hematologic and coagulation profile, chest radiography, and electrocardiography (ECG). Blood is typically typed and cross-matched.
Accurate preoperative documentation of the patient's neurologic condition is essential. In patients with spinal instability or spinal cord compression, particular care should be taken to avoid unnecessary movement of the spine during transport, induction of anesthesia, endotracheal intubation, and positioning. Patients with a full stomach undergoing emergency surgery should have gastric decompression via a nasogastric tube and suction. Patients with cervical spinal instability or cervical spinal cord compression may benefit from fiberoptic endotracheal intubation while awake.
If antibiotic therapy has not been initiated preoperatively, prophylactic antibiotics are generally administrated after the cultures have been obtained. However, when the need for spinal instrumentation is anticipated, it is the author's preference to start IV antibiotics preoperatively so as to minimize bacteremia and reduce the chances of chronic persistent infection at the instrumentation.
Operative details
Infections located in the vertebral body or spinal cord compression produced by collapse of the vertebral body are best corrected by an anterior or anterolateral surgical approach (see the image below), which allows one to decompress the neural elements and to remove the infected disk and involved vertebral bodies. Patients with extensive vertebral destruction usually require instrumentation and fusion.
Spinal infections. Patient B developed lower-extremity weakness, and follow-up studies reveal further compression of L4 and compromise of canal. Anterolateral approach was performed with corpectomy, decompression of spinal canal, restoration of anterior column support, and arthrodesis with titanium cage and autologous iliac crest bone graft. Pathology and Gram stain revealed some hyphae. Culture findings were positive for Aspergillus species. Patient underwent full course of amphotericin B and completely recovered.
In cases of posterior osteomyelitis, especially if a posteriorly placed epidural abscess is present, laminectomy may be indicated. Whether subsequent fusion should be performed depends on the extent of bone removal, the condition of the anterior spinal column, and the likelihood of postoperative spinal instability or deformity.
After the patient is under general anesthesia and the endotracheal tube is secured, the patient's eyes should be well lubricated and taped shut. A Foley catheter is placed, and bilateral thromboembolism-deterrent (TED) hose and sequential compression boots are used. The extremities should be padded carefully to prevent compression-related neural injury.
Patient positioning depends on the particular surgical approach; the preferred position is usually prone for a posterior approach, supine for an anterior approach, and oblique for an anterolateral approach. It is important to avoid applying pressure to the thorax and abdomen so that epidural bleeding can be minimized. [92]
Decompression of the spinal cord and nerve roots with drainage of purulent material and debridement of compressive granulation tissue is central to this procedure. A full set of aerobic, anaerobic, fungal, and acid-fast bacteria cultures should be obtained early in the procedure. Appropriate antibiotics should be administrated at this time. Debridement and drainage should be followed by extensive irrigation with antibiotic solution. In most cases, closure can be done primarily, with a surgical drain left in place.
In some patients, arthrodesis with internal instrumental fixation may be necessary at the time of decompression. [87, 88, 89] Some patients may benefit from the use of vacuum-assisted wound closure. [90] There is strong support in the literature for a staged anterior decompression and strut fusion followed by a second-stage posterior spinal fixation. However, there is also growing support in the literature for the view that in selected patients, anterior fixation can be combined with a strut fusion or a cage filled with autologous bone. [87, 88, 93, 94] The authors prefer the use of a titanium implant filled with autologous iliac crest bone graft.
Zausinger et al suggested possible benefit from combining a surgical approach with stereotactic radiosurgery [91] ; however, the value of this approach remains to be determined.
A posterior approach with no formal debridement has been described as a potential alternative to an anterior approach with aggressive debridement for the treatment of nontuberculous pyogenic spinal infection. A systematic review and meta-analysis by Elmajee et al found the posterior approach to be capable of yielding successful infection resolution, improved pain scores, and better neurologic outcomes but noted the need for larger series with longer follow-up periods. [94]
Postoperative Care
Significant postoperative discomfort limits activity for several days in most patients. A morphine patient-controlled analgesia (PCA) pump usually is employed during the first 36-48 hours.
To allow early patient mobilization postoperatively, patients are braced with an appropriate molded orthosis for a variable period, and a physical therapist is consulted.
The antibiotics should be adjusted according to the culture results.
Nursing care should include frequent repositioning, vigorous pulmonary toilet, and deep venous thrombosis (DVT) prophylaxis.
Complications
Long-term antibiotic treatment may, in itself, lead to complications such as cranial nerve (CN) VIII and renal toxicity, skin rashes, and other sequelae associated with specific antimicrobials.
During the postoperative period, patients with neurologic deficits are prone to multiple complications, including pressure injuries, pulmonary problems, DVT, and urinary sepsis.
Several studies have demonstrated that patients who are immunocompromised (eg, because of diabetes, rheumatoid arthritis [RA], chemotherapy, long-term steroid or narcotic use, or chronic smoking) have an increased incidence of wound healing problems and other complications.
Severely impaired patients with limited mobility are at risk for developing skin decubitus injuries.
Activity
Ealy mobilization with a program of physical therapy is beneficial, reducing the risk of pulmonary and thromboembolic complications. To facilitate early patient mobilization, patients can be braced with an appropriate molded orthosis.
Prevention
Several studies have shown that preincisional antimicrobial prophylaxis administration and use of postoperative antibiotics for 24 hour reduce the rate of SSI after spinal surgery. [95, 38] Prolonged (>48 hr) administration of antimicrobial prophylaxis postoperatively does not seem to be beneficial.
Consultations
A multidisciplinary team approach, including participation of an internist, an infectious disease specialist, a neurosurgeon, and a physical therapist, is beneficial.
Long-Term Monitoring
Once correct treatment is implemented, patients require neurologic monitoring to exclude progressive neurologic deterioration. Home health care may help provide parenteral antibiotics, which typically are given until the infection resolves. Rehabilitation for any residual neurologic deficit may be necessary. This would include restrengthening programs and ambulation retraining.
In addition, follow-up laboratory and radiologic studies are necessary. A falling ESR is consistent with successful treatment. Decreases in serum C-reactive protein (CRP) have been shown to be more sensitive than the ESR. Serial radiographic studies are needed to detect bony collapse or deformity.
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Spinal infections. Lateral plain radiographs of Patient A with diskitis at C4-5. Note severe disk space narrowing and subluxation seen at C4-5.
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Spinal infections. T2-weighted MRI of Patient A. Evidence of osteomyelitis and diskitis, as well as small epidural abscess, is present. The patient underwent C4-5 anterior cervical diskectomy and arthrodesis using autologous iliac crest bone graft and instrumental fixation with titanium plate and screws.
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Spinal infections. Patient B (47-year-old woman) presented with intractable back pain. Radiographs reveal significant collapse and destruction of the L4 vertebral body. MRI of lumbar spine was ordered.
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MRI of Patient B reveals enhancing mass affecting L4 vertebral body with compromise of spinal canal. Patient underwent several blood cultures and CT-guided trocar biopsy; culture results were negative. Surgical procedure was necessary.
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Spinal infections. Patient B developed lower-extremity weakness, and follow-up studies reveal further compression of L4 and compromise of canal. Anterolateral approach was performed with corpectomy, decompression of spinal canal, restoration of anterior column support, and arthrodesis with titanium cage and autologous iliac crest bone graft. Pathology and Gram stain revealed some hyphae. Culture findings were positive for Aspergillus species. Patient underwent full course of amphotericin B and completely recovered.
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MRI with gadolinium contrast in 41-year-old patient with history of IV drug use and extensive osteomyelitis, diskitis, and anterior spinal epidural abscess causing compression of spinal cord.
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Intraoperative fluoroscopy in 41-year-old patient with history of IV drug use and extensive osteomyelitis, diskitis, and anterior spinal epidural abscess treated with corpectomy and anterior stabilization.
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AP intraoperative fluoroscopy. Given abnormal softening of bones by osteomyelitis, same patient underwent posterior stabilization of spine with lateral mass and pedicle screws.
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3D CT of 41-year-old man with severe osteomyelitis and diskitis at L3 and L4. Note bony destruction. This was later demonstrated with gadolinium-enhanced MRI.
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Gadolinium-enhanced MRI in 37-year-old male with history of IV methamphetamine use who developed severe diskitis at L3-4. Epidural abscess is also present. Treatment of his condition required extensive surgical decompression and stabilization. Cultures showed polymicrobial infection, including gram-positive and gram-negative bacteria. Antibiotic beads soaked in vancomycin and tobramycin were applied to surgical site.
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Gadolinium-enhanced MRI in 67-year-old male with L3-4 and L4-5 diskitis. Initial cultures were negative. He was treated medically with 8 weeks of IV antibiotics and clinical follow-up with ESR and CRP.
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Same patient presented several months later with intractable pain. His CT and MRI showed extensive destruction of disks and vertebral bodies. His condition required extensive debridement with stabilization of spine using transpedicular screws and rods. Antibiotic beads were placed at surgical site.
