You are in: eMedicine Specialties > Orthopedic Surgery > SPINE Spinal InfectionsArticle Last Updated: May 9, 2003AUTHOR AND EDITOR INFORMATIONAuthor: Federico C Vinas, MD, Consulting Neurosurgeon, Department of Neurological Surgery, Halifax Medical Center Federico C Vinas is a member of the following medical societies: American Association of Neurological Surgeons, American College of Surgeons, American Medical Association, Congress of Neurological Surgeons, Florida Medical Association, and North American Spine Society Coauthor(s): Richard Rhodes, MD, Consulting Surgeon, Department of Orthopedic Surgery, Halifax Medical Center; Amy Stumpf, BA, BS, MPH, PA-C, Department of Neurosurgery, Halifax Medical Center Editors: James F Kellam, MD, Vice-Chair, Department of Orthopedic Surgery, Director of Orthopedic Trauma and Education, Carolinas Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; William O Shaffer, BS, MD, Professor, Vice-Chairman and Residency Program Director, Department of Orthopedic Surgery, University of Kentucky at Lexington; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Mary Ann E Keenan, MD, Professor, Vice Chair for Graduate Medical Education, Department of Orthopedic Surgery, University of Pennsylvania School of Medicine; Chief of Neuro-Orthopedics Program, Department of Orthopedic Surgery, Hospital of the University of Pennsylvania Author and Editor Disclosure Synonyms and related keywords: pyogenic vertebral osteomyelitis, vertebral infection, bacterial osteomyelitis, infectious osteomyelitis, pyogenic vertebral infections, diskitis INTRODUCTIONPyogenic vertebral osteomyelitis is the most commonly encountered form of vertebral infection. It can develop from direct open spinal trauma, infections in adjacent structures, or from hematogenous spread of bacteria to a vertebra, or it can occur postoperatively. Left untreated, it can lead to permanent neurologic deficits, significant spinal deformity, or death. History of the ProcedureEvidence of vertebral osteomyelitis has been found in Egyptian mummies. Hippocrates first described the infection of the vertebral column. Later on, Galen related this infectious process to spinal deformity. Prior to the development of antibiotics and bacteriology, little knowledge was added to the basic understandings of the Hippocratic school until Servino and Potts characterized and described the pathology of tuberculosis infection of the spine. In 1879, Lannelonge described bacterial osteomyelitis as we recognize it today. Although successful treatment of spinal abscess with surgical drainage was reported early on, the high complication rate from secondary infection caused this surgery to remain in poor favor. Following the introduction of antisepsis, surgical intervention for spinal infections became feasible. The initial procedure introduced for the surgical treatment of spinal infections was a laminectomy. However, this procedure did not allow access to anterior abscesses and contributed to spinal instability, which often resulted in progressive deformity. Ito et al first described the anterior approach to the spine. Later, Hodgson and Stock extensively reported this procedure in the treatment of tuberculosis of the spine. Late spinal deformity was prevented with spinal fusion and instrumentation. While Hodgson and Stock performed fusions from the anterior approach, Hibbs and Albee independently presented techniques for posterior spinal fusion in the treatment of tuberculosis of the spine. Currently, the advancement of bacteriology and the development of modern chemotherapeutic agents have changed the characteristics of spinal osteomyelitis. ProblemVertebral osteomyelitis, if untreated, can lead to permanent paralysis, significant spinal deformity, or death. FrequencyVertebral osteomyelitis is considered uncommon, with an incidence of 1 case per 100,000-250,000 population per year. However, some reviews suggest that the incidence of spinal infections is now increasing. This increase may be secondary to increased use of vascular devices and other forms of instrumentation and to increasing rates of intravenous drug abuse. Because of its rarity and vague initial signs and symptoms, diagnosis is often delayed. No specific predilection for a particular race has been noted. Osteomyelitis has a predilection for males. A bimodal age distribution occurs in diskitis. Diskitis and osteomyelitis peak in pediatric patients; the incidence of spinal infections then decreases until middle age, when a second peak in incidence is observed at approximately age 50 years. Some authors argue that childhood diskitis is a separate disease entity and should be considered independently. In developed nations, incidence of spinal osteomyelitis is similar to that in the United States. However, in less developed nations, infectious osteomyelitis is more common. In some areas of Africa, a reported 11% of all patients seen for back pain were diagnosed with diskitis and osteomyelitis. EtiologyPresumably, a distant focus of infection provides an infective nidus from which bacteria spread by the bloodstream to the spinal column. The skin and the genitourinary tract are common antecedent sites, but a review of the literature reveals multiple foci, such as septic arthritis, sinusitis, subacute bacterial endocarditis, and respiratory, oral, or gastrointestinal infection. Approximately 30-70% of patients with vertebral osteomyelitis have no obvious prior infection. Risk factors for developing osteomyelitis include conditions that compromise the immune system, such as the following:
Intravenous drug abuse is a growing cause of spinal infections. Typically, the organism most likely to infect the spine is Staphylococcus aureus; however, in intravenous drug users, Pseudomonas species are also a common cause. Nonpyogenic osteomyelitis can be caused by tuberculosis, fungus, yeast, or parasitic organisms. Fungal infections of the spine are rare and generally occur in patients who are debilitated or have diabetes or a compromised immune system. Patients with acute leukemia, those with lymphoma, recipients of organ transplants, and those receiving chemotherapy are particularly susceptible. Most vertebral body infections occur in the lumbar spine because of the blood flow to this region of the spine. Tuberculosis infections have a predilection for the thoracic spine, and intravenous drug abusers are more likely to contract an infection of the cervical spine. PathophysiologyApproximately 95% of pyogenic spinal infections involve the vertebral body, and only 5% involve the posterior elements of the spine. This disparity has been attributed in part to the voluminous blood supply to the vertebral body and its rich, cellular marrow. Bacteria circulating through the blood may enter a vertebra or a disk space via its arterial blood supply or via the venous system. In the typical case, bacteria enter the vertebral body through small metaphyseal arteries arising from larger primary periosteal arteries that, in turn, branch from the spinal arteries. In adults, blockage of metaphyseal arteries by septic thrombi may infarct relatively large amounts of bone. Subsequently, bacteria can readily colonize a large bony sequestrum adjacent to the disk. In the adult, after bacterial colonization of the metaphyseal region, the avascular disk is secondarily invaded by bacteria from the endplate region. Intermetaphyseal communicating arteries allow the spread of septic thrombi from one metaphysis to the other in a single vertebral body without involvement of the mid portion of the vertebra. Although the arterial route is the usual route of bacterial spread to a vertebra, another proposed route of infection is the retrograde seeding of venous blood via the Batson plexus. During periods of increased intra-abdominal pressure, venous blood is shunted toward the vertebral venous plexus. Some authors have proposed that the venous system may be the route of bacterial spread from genitourinary tract infections. Another possible means of infection is by the spread of contiguous infection into the vertebrae and disk (eg, from a retropharyngeal abscess or a retroperitoneal abscess), resulting in osteomyelitis and diskitis. ClinicalThe onset is usually insidious. Back pain is the most common symptom. Most patients have a history of several weeks or months of gradually progressing neck or back pain that increases with movement. The pain is initially localized at the level of the involved area, and gradually increases in intensity. Thereafter, the pain eventually becomes so severe that it is not relieved by analgesics or even complete bedrest. Usually, neurologic signs are not present until late in the disease course and may be associated with destruction and collapse of the vertebral body. In the typical case with mild symptoms, physical examination reveals only mild tenderness over the spinous process of the involved vertebra, and minimal spasm may be present in nearby paravertebral muscles. A decreased range of motion is also common. Only about half of patients are febrile. Later, neurologic compromise is caused by bony collapse, spread of the infection underneath the posterior longitudinal ligament, or frank epidural abscess with compression of the spinal cord or nerve roots. A progression to radicular signs followed by weakness and paralysis suggests the formation of an epidural abscess. Spinal epidural abscess occurs in 5-18% of cases and is most commonly located anteriorly in the epidural space. Cervical vertebral osteomyelitis is associated with paralysis more commonly than either thoracic or lumbar infection. Children with vertebral osteomyelitis and associated diskitis usually present with an abrupt onset of malaise, fever, and back pain. They commonly demonstrate back stiffness, restricted motion, guarded walking, and spine tenderness. Some patients can also present acutely with fever, night sweats, elevated leukocyte counts, and signs and symptoms of shock. In patients with neurologic compromise, a detailed motor and sensory examination should be performed. Muscle strength and weakness are graded ranging from a strength of 5/5, considered normal, to a strength of 0/5, or paralysis, as follows:
The sensory examination should include detection of a sensory level, posterior column function, normal and abnormal reflexes, and examination of rectal tone and perianal sensation. The presence of a Babinski sign should also be noted and documented. The neurologic examination should be repeated and documented at regular intervals to serve as a reference for improvement or deterioration of the patient's neurologic status over time. INDICATIONSThe 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 pathological fractures, caused by the softening of the bone, and present with acute spinal cord compression. 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. RELEVANT ANATOMYThe anatomy of the spine includes the vertebral bodies, intervertebral disks, and associated joints, muscles, tendons, ligaments, and neural elements. The intervertebral disk is a fibrocartilaginous remnant of the embryonic notochord, which provides the spine with strength, mobility, and resistance to strain. It consists of 3 parts: the annulus fibrosus, the nucleus pulposus, and the cartilaginous endplates. The annulus fibrosus, is made up of type I collagen fibrils, which are arranged in 15-20 concentric lamellae brought together into parallel bundles. These bundles are firmly attached to the vertebral bodies and are arranged in layers to provide strength and limit vertebral movement when the disk is compressed. The nucleus pulposus is composed of type II collagen and represents 30-60% of the disk volume. The nucleus pulposus is supplied with blood vessels through small perforations in the central cartilaginous endplates. The cervical spine consists of the first 7 vertebrae in the spinal column. Typically these vertebrae are small and posses a foramen on the transverse process for the vertebral artery. The thoracic spine consists of the next 12 vertebrae and is stabilized by the attached rib cage and intercostal musculature. The lumbar spine consists of a mobile segment of 5 vertebrae, located between the relatively immobile segments of the thoracic and sacral segments. The lumbar vertebrae are particularly large and heavy compared to the cervical and thoracic vertebrae. The bodies are wider and have shorter and heavier pedicles, and the transverse processes project somewhat more laterally and ventrally than the other spinal segments. The laminae are shorter vertically than the bodies and are bridged by strong ligaments. The spinal processes are broader and stronger than those in the thoracic and cervical spine. CONTRAINDICATIONSMost patients with pyogenic vertebral osteomyelitis respond to medical management. However, surgery may be required if medical management is unsuccessful. 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. WORKUPLab Studies
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Diagnostic Procedures
Histologic FindingsHistologic findings are similar to those of any bacterial pyogenic infection. Local destruction of the disk and endplates occurs with infiltration of neutrophils in the early stages. Later, a lymphocytic infiltrate predominates. TREATMENTMedical therapyThe 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 initially instituted until the organism is isolated. Most cases of vertebral osteomyelitis are caused by S aureus, which is generally 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. 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. 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 a bony fusion is seen on radiographs or until the patient's pain subsides. A rigid brace works best and only needs to be worn 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. Pediatric Dose-40 mg/kg/d IV. Surgical therapyAlthough 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. 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. Preoperative detailsMost 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. Intraoperative detailsInfections 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 carefully padded 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. Postoperative detailsSignificant 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. In order 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. Follow-upOnce correct treatment is implemented, patients require neurologic monitoring to exclude progressive neurologic deterioration. Home health care may help provide parenteral antibiotics, which are typically 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. Reduction of CRP levels has been shown to be more sensitive than ESR. Serial radiographic studies are needed to detect bony collapse or deformity. COMPLICATIONSPatients dying from vertebral osteomyelitis typically succumb, either from the spinal-neural infection or from 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 eighth nerve and renal toxicity, skin rashes, and other sequelae associated with specific antimicrobials. These complications are more often seen after long-term antibiotic therapy. During the postoperative period, patients with neurologic deficits are prone to multiple complications, including skin decubitus, pulmonary problems, deep venous thrombosis, and urinary sepsis. OUTCOME AND PROGNOSISBoth bony and neural status must be considered in the evaluation of treatment outcome. Most patients can be cured by a treatment protocol that includes antibiotics alone or in combination with surgery. For patients with an incomplete neurologic compromise, several studies indicate that with aggressive antibiotic and surgical therapy, paresis may improve or resolve. Only 15% of patients experience permanent neurologic deficits. Recrudescence of infection occurs in 2-8% of patients. FUTURE AND CONTROVERSIESIn 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 be subsequently implanted next to the spine. These osteoinductive factors enhance the activation and differentiation of pluripotent stem cells to develop into mature bone. MULTIMEDIA
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