Overview
Spinal infections account for 3-5% of all osteomyelitis; diagnosis is often delayed because symptoms are nonspecific (Campbell). Infection may involve the vertebral body, disc, paraspinal tissues or epidural space; spread is hematogenous, contiguous or by direct inoculation. Staphylococcus aureus is the most common organism (Campbell).
Pathoanatomy (Campbell)
The adult disc is avascular; the vascular bony endplate, with slow flow in end arterioles, is where septic emboli lodge. Arterial spread is more common than venous spread through Batson's plexus.
Pyogenic spondylodiscitis: lumbar 50%, thoracic 30%, cervical 15%; 20% are multifocal. About a quarter of patients present with neurologic deficit, more often at higher levels. One-year mortality is 15-20% whether treated medically or surgically.
Risk factors: immunosuppression and frailty, malignancy, diabetes, renal failure, hepatic disease, spine surgery, genitourinary infection or procedure, bacteremia, IV drug use (more often Pseudomonas), HIV and alcoholism. Enterococcal and streptococcal infections suggest endocarditis.
Clinical Presentation (Campbell)
Localized back or neck pain is the most common symptom; insidious, often worse at night, with spasm and loss of motion; diagnosis may be delayed up to 6 months.
Fever is present in only about 50% but should immediately raise suspicion.
Psoas extension may present as swelling in the groin below the inguinal ligament.
Neurologic deficits are rarely the presenting complaint; they suggest compression by abscess, collapse or direct neural infection and can progress rapidly.
Laboratory Studies (Campbell)
CRP is the most sensitive marker and is almost always elevated. After uncomplicated spine surgery CRP peaks within 2 days and normalizes by 14 days; persistent elevation beyond 4-7 days or a second rise strongly suggests infection. CRP is used to monitor treatment.
ESR remains elevated for weeks after successful treatment; after surgery it peaks at about 5 days (about 25 mm/h). Persistent elevation at 4 weeks with clinical findings suggests infection.
White cell count is not especially helpful. Positive blood cultures may suffice to guide antibiotics.
Imaging (Campbell)
Radiographs: changes appear 2 weeks to 3 months after onset (disc space narrowing, endplate irregularity, subchondral defects, sclerosis); late collapse, kyphosis, ankylosis.
CT: better for paraspinal abscess and bony destruction. Myelography risks seeding the subarachnoid space; use only when MRI is unavailable.
MRI with and without gadolinium is the modality of choice (96% sensitivity, 93% specificity): T1 hypointense and T2 hyperintense disc and adjacent bodies; abscesses bright on T2; fat suppression and gadolinium improve sensitivity. Image the entire spine because noncontiguous infection occurs in 15-20%.
Serial MRI is not indicated unless the patient fails to improve; bony findings may look unchanged or worse despite clinical improvement. Follow soft-tissue findings and the clinical course.
FDG-PET has sensitivity and specificity similar to MRI; combined technetium and gallium scanning is accurate; indium-labeled WBC scans distinguish hematoma or seroma from infection.
Biopsy (Campbell)
Biopsy is the best way to confirm infection and identify the organism. IDSA guidance: image-guided tissue biopsy when blood cultures are negative, and withhold antibiotics in hemodynamically stable patients without neurologic deficit until after biopsy.
CT-guided needle versus open biopsy: diagnostic yield 48% versus 76% in one comparison (93% versus 22% microbiologic yield in another). Core biopsy of subchondral bone improves yield; abscess fluid is often sterile. A negative needle biopsy should not preclude open biopsy when clinical suspicion is strong.
Differential diagnosis: primary and metastatic tumors, metabolic bone disease with fracture, psoas, hip, abdominal or genitourinary infection, rheumatoid arthritis, ankylosing spondylitis and Charcot spine.
Nonoperative Treatment (Campbell)
Organism-specific antibiotics are the primary therapy, even with an associated epidural abscess when there is no neurologic deficit; medical management succeeds in 75-80%.
IV antibiotics usually for about 6 weeks, followed by oral antibiotics guided by CRP, ESR and clinical response; lifelong suppression is sometimes recommended when instrumentation is present.
Monitor with clinical symptoms and serial CRP. Failure suggests a multiorganism infection: consider repeat (open) biopsy, debridement of sequestrum or abscess drainage.
Brace patients at risk for pathologic fracture or in pain. Most pyogenic infections resolve within 9-24 months.
Indications for Surgery (Campbell)
Disease progression despite appropriate antimicrobial therapy.
Spinal instability with significant deformity or pain.
Instability or epidural abscess with cord or cauda equina compression, or impending neural compression.
Debridement in the presence of sepsis.
To obtain tissue when a diagnosis is not otherwise possible.
Surgical Principles for Spondylodiscitis (Campbell)
Vertebral osteomyelitis compromises the anterior column, so an approach that allows thorough anterior debridement and reconstruction is usually necessary; posterior-only surgery is generally not indicated, except for some patients with a predominant epidural abscess.
Goals: thorough debridement, decompression of the neural elements, stabilization and correction of deformity. Often a corpectomy with structural autograft or allograft or a mesh or expandable cage is required; all are acceptable.
Cervical spine: an anterior approach is often adequate, sometimes with posterior supplementation. Thoracic and lumbar spine: the body can be reached anteriorly or posteriorly; posterior stabilization depends on remaining stability and the length of the anterior construct.
Instrumentation can be used in active infection because the spine is well vascularized, supplemented by a course of IV antibiotics.
Spinal Epidural Abscess (SEA) (Campbell)
Incidence 0.5-2 per 10,000 admissions; usually spans three to five segments. Most occur in the lower lumbar region; neurologic risk is highest in the cervical spine.
Abscesses from vertebral osteomyelitis are usually ventral; those from facet infection are dorsal.
The classic triad of pain, fever and neurologic deficit is unreliable. Compared with osteomyelitis: faster neurologic progression (days), more acute fever and meningeal signs. Heusner's progression: spinal ache, root pain, weakness, then paralysis, which may occur suddenly. Do not wait for neurologic deficit, which is a poor prognostic sign.
Diagnosis by MRI with gadolinium (sensitivity and specificity above 90%), imaging the entire spine. The clinical course matters more than follow-up imaging in deciding on surgery.
Treatment of SEA (Campbell)
SEA without neurologic involvement and with a known organism can usually be managed with antibiotics alone under close observation; also consider medical management in high surgical risk, pan-spinal disease without focal compression, or complete deficit present for more than 48 hours.
Cervical SEA: medical management alone failed in 75% with poor motor outcomes; all patients should have early decompression.
Failure of medical management is reported in 27-41%. Risk factors for failure: age over 65, diabetes, MRSA, CRP above 115 mg/L, WBC above 12.5 x 10^9/L, progressive or significant deficit, fulminant sepsis and circumferential dural enhancement on MRI.
Empiric antibiotics should cover Gram-positive organisms (S. aureus, other staphylococci, streptococci, enterococci), but hold antibiotics until cultures are obtained in stable patients.
Drainage: early neurologic deficits are usually mechanical and reversible with prompt decompression. Dorsal, lateral and some ventral abscesses: laminectomy with drainage. Abscess with osteomyelitis and instability: anterior or posterolateral exposure to treat both. Laminectomy, especially in the cervical spine, often leads to late deformity, so add posterior instrumentation. CT-guided aspiration is not recommended by the authors.
Postoperative Spinal Infection (Campbell)
After posterior procedures: posterior debridement and irrigation, retaining well-fixed implants and adherent graft and removing necrotic tissue and nonvascularized graft.
Pediatric Spondylodiscitis (Campbell)
Neonatal (under 6 months, S. aureus, often multifocal with sepsis), infantile (6 months-4 years, 60-70%, often Kingella kingae; PCR from a throat swab helps) and juvenile (4-16 years).
Children may refuse to walk; ESR is elevated more often than CRP; radiographs are negative early. CT biopsy is reserved for nonresponders or uncertain diagnosis.
Treatment: organism-specific IV antibiotics and rest until comfortable, then oral antibiotics; spontaneous fusion occurs in about 25%; surgery is rarely needed except in tuberculosis and other caseating infections.
Tuberculosis (Campbell)
Spreads beneath the anterior longitudinal ligament to adjacent levels, relatively sparing the discs and skipping levels; fine paravertebral calcification is the only specific radiographic sign.
PCR speeds diagnosis. Multidrug therapy for about a year is usually effective if started before major destruction or deficit; when surgery is required, anterior debridement and strut grafting with posterior stabilization are typical.
References
Williams KD, Orland KJ. Infections and tumors of the spine. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 49.