Spinal Infections Treatment & Management

The overall treatment plan for a patient with vertebral osteomyelitis must be individualized according to the patient's general medical condition, neurologic status, presence of large associated abscesses, and biomechanical factors. Underlying infections (eg, retropharyngeal, pelvic, decubital) require simultaneous treatment if the vertebral infection is to be cured. 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, are instituted 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.^{[2, 27]}

Antibiotics are given for variable lengths of time. It would appear that 6-8 weeks of parenteral antibiotic therapy is effective in most cases. Before parenteral antibiotics are discontinued, the 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 intravenous 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.^{[28, 29]}

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 needs to 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 using 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 directed against gram-positive organisms and that is active against Enterococcus species. It is useful in the treatment of septicemia and skin structure infections 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, the current recommendation is to assay vancomycin trough levels after the third dose is drawn one half hour prior to the next dosing. Use creatinine clearance (CrCl) 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 GI or GU procedures. Adult dosing is 500 mg/d to 2 g/d IV. Pediatric dosing is 40 mg/kg/d IV. Vancomycin is a pregnancy category C drug.

Nafcillin (Unipen, Nallpen, Nafcil) is the unitial therapy for suspected penicillin G–resistant streptococcal or staphylococcal infections. Use parenteral therapy initially in severe infections. Change to oral therapy as the patient’s condition warrants. Because of the risk of thrombophlebitis, particularly in elderly patients, administer parenterally only for short term (1-2 d); change to oral route as clinically indicated. Adult dosing is 1 g IV/IM q4-6h. Neonatal dosing (0-4 kg) is 10 mg/kg IM bid. Dosing in children who weigh 4-40 kg is 25 mg/kg IM bid or 50 mg/kd/d PO divided qid or, alternatively, 100-200 mg/kg/d IV/IM in 4-6 divided doses. Nafcillin is a pregnancy category B drug.

Gentamicin (Garamycin, Gentacidin) 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. Consider gentamicin 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; adjust dose based on CrCl and changes in volume of distribution. It may be given IV/IM. In adults, dosing for serious infections and normal renal function is 3 mg/kg/dose IV q8h. The loading dose and maintenance dose is 1-2.5 mg/kg IV and 1-1.5 mg/kg IV, respectively, q8h. The extended dosing regimen for life-threatening infections is 5 mg/kg/d IV/IM q6-8h. Follow each regimen by at least a trough level drawn on the third or fourth dose (0.5 h before dosing); a peak level may be drawn 0.5 h after 30-min infusion. In children < 5 years, dosing is 2.5 mg/kg/dose IV/IM q8h. Inthose >5 years, dosing is 1.5-2.5 mg/kg/dose IV/IM q8h or 6-7.5 mg/kg/d divided q8h, not to exceed 300 mg/d; monitor as in adults.

Ceftazidime (Tazidime, Tazicef, Ceptaz, Fortaz) 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 q8-12h. Neonatal dosing is 30 mg/kg IV q12h. In infants and children, dosing is 30-50 mg/kg/dose IV q8h, not to exceed 6 g/d. Ceftazidime is a pregnancy category B drug.

Although most patients with pyogenic vertebral osteomyelitis respond to medical management, surgery may be required. Indications for surgery include significant osseous involvement, neurologic deficits, septic course with clinical toxicity from an abscess not responding to antibiotics, failure of needle biopsy to obtain necessary cultures, and failure of intravenous antibiotics alone to eradicate the infection. 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.^{[2, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39]}

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.

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 radiograph, and ECG. Blood is typically typed and cross-matched.

An accurate preoperative documentation of the patient's neurologic condition is of primary importance. 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.

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, 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.

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, 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 TED hose and sequential compression boots are used. The extremities should be padded carefully to avoid compression-related neural injury.

Patient positioning depends on the particular surgical approach, usually prone for a posterior approach, supine for anterior approaches, 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.

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, leaving a surgical drain in place.

In some patients, an arthrodesis with internal instrumental fixation may be necessary at the time of decompression. 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 an evolving literature that in selected patients anterior fixation can be combined with a strut fusion.^{[30, 31, 40]}

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.

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 CRP have been shown to be more sensitive than ESR. Serial radiographic studies are needed to detect bony collapse or deformity.

Patients dying from vertebral osteomyelitis typically succumb to the spinal-neural infection or to other attendant problems, such as secondary sepsis, inanition, or the original infection. The mortality rate for osteomyelitis ranges from 2-12%. Neurologic deficits develop in 13-40% of patients, especially those with diabetes or other systemic illnesses. Long-term antibiotic treatment may, in itself, lead to complications such as 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 skin decubitus, pulmonary problems, deep venous thrombosis, and urinary sepsis.

Both bony and neural status must be considered in the evaluation of treatment outcome.^[41] Most patients can be cured by a treatment protocol that includes antibiotics alone or in combination with surgery.^{[32, 33]} For patients with an incomplete neurologic compromise, several studies indicate that with aggressive antibiotic and surgical therapy, paresis may improve or resolve.^{[34, 35, 36]} Only 15% of patients experience permanent neurologic deficits. Recrudescence of infection occurs in 2-8% of patients.

In the future, the introduction of newer, more effective antibiotics may contribute to the treatment of these infections. For patients requiring a fusion, the use of growth factors for the induction of spinal fusions is a theoretically attractive approach. Numerous studies have shown that viral vectors can be used to implant osteoinductive growth factor genes directly into the paraspinal muscles or into cells that can subsequently be implanted next to the spine. These osteoinductive factors enhance the activation and differentiation of pluripotent stem cells to develop into mature bone.