Spondylodiscitis

  • Discitis is an infection of the disc space and vertebral endplate that is caused by hematogenous or postoperative inoculation.
  • It affects intervertebral discs of the spine.
    • The lower lumbar discs are most commonly involved.
    • However, the infection may occur in any disc.
  • Classification:
    • Spontaneous (hematogenous)
    • Iatrogenic (after discectomy or discogram)
Epidemiology
  • Hematogenous infection is uncommon.
  • The mean age of occurrence of hematogenous (spontaneous) discitis is 7 years, but it may affect individuals of any age.
Incidence
The incidence of infection after discectomy is <1%.
 
Risk Factors
  • Compromised host (patients with diabetes, alcohol abuse, transplants)
  • Intravenous drug abuse
  • Procedures involving the disc (discography, discectomy, spinal anesthesia)
Etiology
  • Bacterial infection:
    • The causative organism most commonly is Staphylococcus, except in the compromised host or intravenous drug abuser, in whom Gram-negative aerobic bacteria and Candida are more common (for these patients, biopsy is indicated).
  • Vascularity issues in children <8 years old:
    • The blood supply to the disc comes from the adjacent vertebral body.
    • Vessels cross the cartilaginous endplate in children until they are approximately 8 years old, and the resultant vascularity renders younger children susceptible to infection in the area.
Associated Conditions
Vertebral osteomyelitis
 
Diagnosis
Signs and Symptoms
  • Symptoms:
    • Back pain, usually insidious in onset but increasing with time
    • Abdominal pain
    • Loss of appetite
    • Malaise
  • Signs:
    • Back stiffness
    • Refusal to walk
    • Pain on spinal percussion
    • Loss of lordosis
    • Fever: Usually low-grade, but may be absent
Physical Exam
  • Note the presence or absence of normal lumbar lordosis.
  • Look for pain or refusal to bend forward.
  • Look for pain on paraspinal percussion.
  • Look for pain on abdominal palpation in lumbar discitis.
  • Neurologic examination remains normal, except in late presentations of fulminant discitis.
Tests
Lab
  • White blood cell count, ESR, and C-reactive protein usually are mildly elevated but may be normal.
  • Obtain a blood culture even though it is positive <30% of the time.
  • No specific laboratory tests exists for this disorder.
Imaging
  • Plain films are positive only after several weeks; they show irregularity and narrowing of the disc space, with mild osseous involvement.
  • MRI:
    • For suspected cases of discitis, shows the pathologic features before abnormalities are visible radiographically.
    • Gives more detailed anatomic information than a bone scan, but a bone scan is an acceptable alternative
Pathological Findings
  • Chronic inflammation
  • Destruction of disc structure and endplates
Differential Diagnosis
  • Tuberculosis (usually shows more destruction of adjacent bone)
  • Vertebral osteomyelitis (more destruction of bone than disc, but these 2 entities may merge)
Treatment
General Measures
  • Rest
  • Immobilization
  • Antibiotics
  • For childhood spontaneous discitis, no biopsy or debridement is needed because treatment of staphylococcal infection is virtually always successful.
    • This treatment should be given intravenously if the patient is severely ill, orally if the patient is only mildly symptomatic.
    • Bed rest and bracing may be used if pain is pronounced.
    • For discitis in the compromised host, biopsy and drainage should be performed.
Special Therapy
Physical Therapy
Therapy is useful for adults with severe back stiffness after treatment has begun.
 
Medication (Drugs)
  • For routine spontaneous discitis, oxacillin, dicloxacillin, and cephalosporin are indicated.
  • For complicated cases or in compromised hosts, broad-spectrum antibiotics effective against Gram-negative and anaerobic organisms should be added.
  • NSAIDs or mild narcotics may help patients with severe pain initially until the infection is controlled.
Surgery
  • Biopsy may be required in the immunocompromised patient, or one for whom medical therapy has failed.
    • Anterolateral or posterolateral approach with fluoroscopic guidance
  • Drainage may be required for patients who fail to respond to medical management alone.
    • Usually obtained via an anterior approach to allow adequate visualization, debridement, and safety
  • Surgical reconstruction of the spine segment may be indicated for adults with substantial disc space destruction or endplate compromise.
Follow-up
Prognosis
  • Prognosis is good once the infection has cleared.
  • After childhood discitis, the vertebrae adjacent to the infected disc usually develop a spontaneous painless fusion.
  • In adults, spontaneous fusion does not always occur, and back pain may persist.
Complications
Persistence of infection (lack of symptom improvement in 1-2 weeks) requires accurate identification of the organism and adequate debridement.
 
Patient Monitoring
  • Physical examination is the most useful means for monitoring infection healing.
  • The examiner should check for tenderness to percussion and range of forward flexion.
  • Radiographs and ESR lag far behind the clinical course.