Vertebral osteomyelitis

May be acute, subacute or chronic.

Vertebra may be infected from hematogenous spread, directly from the time of spinal surgery or spread from adjacent soft tissues.

Incidence 2.4 cases per 100,000 population.

Incidence increases with age with 0.3 per 100,000 below the age of 20 years and 6.5 per 100,000 persons older than 65 years (Grammatico L).

Most common agents involve bacterial agents Staphylococcus aureus and E. coli (Mylona E).

Following spinal surgery, particularly if fixation devices are present, is associated most commonly with coagulase negative staphylococci or Proprionibacterium acnes (McHenry MC).

In the presence of chronic infections and prolonged bacteremia hematogenous infections may be due to low virulence bacteria.

The primary site of infection in 253 cases of vertebral osteomyelitis was identified in 51% of the cases and included: the urinary tract, skin, soft tissues, vascular access device, endocardium, bursitis, or septic joint (McHenry MC).

Most cases of infectious hematogenously derived osteomyelitis occur in individuals with comorbid processes such as diabetes, coronary heart disease, cancer, immunosuppressive therapy, renal failure on dialysis, and intravenous drug abuse.

Complications of vertebral osteomyelitis include paravertebral, epidural and psoas abscesses.

In the McHenry review of 253 cases complications included epidural abscesses (17%), paravertebral abscess (26%), and disc space abscess (5%).

Epidural abscess complicates vertebral osteomyelitis in the cervical, thoracic, and lumbar spine, spine 28%, 22% and 12% of cases, respectively.

Motor weakness and paralysis may occur and these problems are more likely with cervical spine osteomyelitis.

Spinal involvement occurs most commonly in the lumbar spine (58%), thoracic pain (30%), and cervical spine (11%).

Overall 36% of patients with vertebral osteomyelitis have neurological complications (Pigrau C).

One third of patients complain of sensory loss, weakness or radicular pain.

In a review of pyogenic vertebral osteomyelitis 8% of patients relapse and 6% die.(Mylona E).

Back pain is the most common presenting symptom and it occurs in 86% of patients (Mylona E).

Fever may be present in 35-60% of patients.

Spinal percussion associated with pain occurs in one fifth of patients (Priest DH).

The primary infection may dominate the initial clinical presentation before vertebral osteomyelitis is recognized.

Endocarditis is diagnosed in as many as one third of cases of vertebral osteomyelitis (Pigrau C).

Leukocytosis and shift to the left with increase neutrophils common.

Elevation of erythrocyte sedimentation rate and CRP seen in 98% and 100% of cases, respectively.

CRP a better marker of inflammation than ESR, particularly after postoperative vertebral osteomyelitis (Zimmerli W).

Positive blood cultures in 30-78% of cases (Mylona E).

If clinical suspicion for the diagnosis of vertebral osteomyelitis is present and blood cultures are negative, biopsy should be considered.

When polymicrobial vertebral osteomyelitis is considered, as with an abdominal abscess, biopsy should be performed (Palestro CJ).

A culture of a vertebral biopsy has a higher yield (47-100%)than does blood cultures (Mylona E).

Bone biopsies should be cultures for aerobic and anaerobic bacteria, and for fungal organisms.

Under appropriate clinical conditions bone biopsy cultures for mycobacteria and brucella species should be considered.

Histologic evaluation of vertebral biopsy may help determine the type of infection by the presence of neutrophils or granuloma.

Vertebral biopsy is preferentially a closed CT guided one, but open biopsy may be needed if the exam is not rewarding.

If patients are on antibiotics, cultures may be false negative.

Antibiotic treatment may be held in patients that are not toxic until cultures confirm an infectious process.

In patients on antibiotics, they may be discontinued for an antibiotic free period and then the patient may be cultured.

When psoas abscess, paravertebral or epidural abscess is present aspiration and culture preclude the necessity of bone biopsy.

MRI imaging has a high accuracy for diagnosis of 90%.

MRI imaging should be the initial imaging study when considering vertebral osteomyelitis as the diagnosis when there is also neurological impairment.

MRI in vertebral osteomyelitis high signal intensity within the disk on T2 weighted sequences, vertebral end plates have high signal intensity marrow edema.

Usually the disk space and adjacent 2 vertebrae are involved.

MRI more sensitive diagnostic tool than CT scan and the latter should be used when contraindications for MRI are present.

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