Hospital Medicine

Vertebral osteomyelitis and discitis

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Vertebral osteomyelitis

I. What every physician needs to know.

Osteomyelitis, an infection of bone, is usually caused by pyogenic bacteria and mycobacteria. Microorganisms can enter the bone by hematogenous dissemination, by spread from a contiguous focus of infection, or by a penetrating wound. Trauma, ischemia, and foreign bodies enhance the susceptibility of bone to microbial invasion. The vertebrae are the most common sites of hematogenous osteomyelitis in adults. The organisms reach the well-perfused vertebral body via spinal arteries and quickly spread from the end plate into the disk space and then to the adjacent vertebral body. Sources of bacteremia include the urinary tract, dental abscesses, soft tissue infections, and contaminated IV lines.

II. Diagnostic Confirmation: Are you sure your patient has vertebral osteomyelitis?

Bone biopsy with microbiologic and/or pathologic confirmation is the gold standard. MRI has 90% accuracy, but not 100% specificity.

A. History Part I: Pattern Recognition:

Back pain is the most common initial symptom. Fever is present only 30%-60% of the time, perhaps because of the concurrent use of analgesics, which have antipyretic properties. The location of pain is usually lumbar (60%), thoracic (30%), or cervical (10%). Neurologic impairment (e.g., weakness, sensory disturbance, radiculopathy) is noted in a third of cases. Particularly severe, sharp, or lancinating pain may indicate the presence of an epidural abscess.

B. History Part 2: Prevalence:

The incidence of vertebral osteomyelitis has been estimated at 2.4 cases per 100,000 population, with the incidence increasing with increasing age (from 0.3 per 100,000 among persons younger than age 20 to 6.5 per 100,000 among persons older than age 70).

Risk factors for spinal infection include diabetes mellitus requiring insulin injection, a recent invasive medical procedure, hemodialysis, immunosuppressive disorders, and injection drug use.

C. History Part 3: Competing diagnoses that can mimic vertebral osteomyelitis.

"Viral syndrome"

Pancreatitis

Pyelonephritis

Osteoporotic fracture

Spinal stenosis

A combination of laboratory findings and imaging studies will help to differentiate vertebral osteomyelitis from the other diagnoses on the differential.

D. Physical Examination Findings.

Sensory loss, weakness, and radiculopathy associated with the specific vertebrae involved occur in about 30% of cases.

Tenderness of the spine on palpation was found in only 20% of subjects in one study.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and blood cultures should be ordered. Elevated ESR and CRP levels are 98% and 100% sensitive, respectively, which are much more sensitive than an elevated WBC count.

A positive blood culture precludes the need for more invasive testing unless the infection is thought to be polymicrobial (e.g., intrabdominal sepsis), in which case a bone biopsy should be sought.

If blood cultures are negative in the setting of a clinical history suggestive of vertebral osteomyelitis and imaging studies that point to the diagnosis, a bone biopsy should be pursued to obtain cultures for aerobic and anaerobic bacteria, and fungi. If the patient has a history of a stay in a region in which relevant bacteria are endemic or if the patient presents subacutely, then cultures should be sent for mycobacteria and brucella species.

The use of CT-guided or open biopsy is determined by the center at which you practice. If CT-guided biopsy yields negative results, yet suspicion for the disease remains high, consider pursuing open biopsy.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

MRI with gadolinium enhancement is the test of choice (particularly in patients with neurologic symptoms), as it has 90% sensitivity for vertebral osteomyelitis and may help identify the presence of an epidural abscess. MRI will typically show high signal intensity within the disc on T2-weighted sequences and loss of the intranuclear cleft. The vertebral end plates are rapidly destroyed, and high-signal-intensity marrow edema is visible. Typically, the disc space and two adjacent vertebral bodies are involved.

Plain X-ray is not as sensitive as MRI, especially in early osteomyelitis. It may be useful to look for anatomic abnormalities (e.g., fractures) or foreign bodies.

If MRI is not available or if the patient cannot undergo MRI (e.g., presence of a pacemaker or renal insufficiency), then consider positron-emission tomographic (PET) scanning with 18F-fluorodeoxyglucose has a diagnostic accuracy similar to that of MRI. Ga-67 scintigraphy with single-photon-emission CT (SPECT) can also be used with similar sensitivity as MRI, but it is less sensitive for the diagnosis of epidural abscess. Three-phase bone scan is highly sensitive in acute infection, but less sensitive if blood flow is poor and has poor specificity.

Erosive osteochondrosis secondary to degenerative changes is the most difficult diagnosis to differentiate from vertebral osteomyelitis via MRI. If comparison films are available from prior studies, this may help differentiate the two disease processes.

F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.

In a series of patients with staphylococcal vertebral osteomyelitis, an elevated WBC count or increased percentage of neutrophils was found in only 64% and 39% of cases, respectively. Therefore, the CBC is not a very sensitive or specific test.

III. Default Management.

A. Immediate management.

Determination of neurologic compromise by a thorough physical examination and expedited imaging of the spinal cord will determine the need for more aggressive interventions that should be completed in a timely manner (e.g., surgical debridement via open approach or with the assistance of interventional radiology).

Neurosurgical or orthopedic consultation may be necessary if there is evidence of cord compromise and if a spinal implant is in place.

Immediate use of antibiotics is often not warranted when the diagnosis of vertebral osteomyelitis is made unless the patient is in severe sepsis or septic shock.

B. Physical Examination tips to guide management.

Each day, the hospitalist should conduct a thorough neurological examination focused on where the disease is located; a cardiovascular exam to listen for murmurs that may indicate the presence of endocarditis in association with vertebral osteomyelitis; and an examination of the skin (e.g., to search for sources of infection or to detect the presence of petechial rashes to suggest the development of DIC).

Hyperreflexia may be seen below the level of compression. In the case of cauda equina syndrome, however, hyporeflexia is the typical finding.

Sensory abnormalities, which occur less commonly, include bilateral ascending parasthesias, saddle anesthesia, and unilateral parasthesias in a radicular pattern. Any patient who reports saddle anesthesia should be considered to have cauda equina syndrome until proved otherwise.

Bowel or bladder dysfunction is frequently a late finding of cord compression. Nonetheless, acute urinary retention with overflow incontinence may be the initial (and only) finding of cord compression. Any report of urinary retention mandates that a post-void residual be checked.

Looking for signs of cord compression each day is essential. The predominant neurologic symptoms of epidural spinal cord compression are motor weakness, parasthesias, bowel and bladder dysfunction, and gait abnormalities. Motor weakness, the most common symptom, affects 60%-85% of patients at the time of diagnosis and is usually symmetric.

C. Laboratory tests to monitor response to and adjustments in management.

A clinical assessment should be made four weeks after initiation of therapy. Continued fever or pain and a persistently elevated CRP (>30 mg/L) predict treatment failure.

Routine follow-up MRI is not indicated and should be reserved only for patients who have worsening pain or continued elevation of CRP (>30 mg/L) at four weeks or at any time if new neurologic symptoms emerge that suggest cord compression.

If patient is on vancomycin, trough levels should be checked before the fourth dose (with a goal of 15-20 mg/L) and every week thereafter, with dosages adjusted accordingly. Weekly basic metabolic panel (BMP) and complete blood count (CBC) to monitor renal function and platelet count should also be done while a patient is on vancomycin.

D. Long-term management.

Eighty percent to 90% of patients are disease-free 1 year after treatment. There is no need for long-term management other than counseling the patient on avoiding any high-risk behaviors that may have been associated with developing vertebral osteomyelitis (e.g., IVDA) and long-term control of any other co-morbid conditions (e.g., diabetes).

E. Common pitfalls and side effects of management

All treatments should be given for six weeks. Choice of antibiotics should be based on culture sensitivities.

For culture-negative vertebral osteomyelitis not associated with a surgical procedure, Cefazolin 1-2 g IV q 8 hours should be given.

For culture-negative vertebral osteomyelitis associated with a surgical procedure, Vancomycin 1 g IV q 12 hours (goal trough 15-20 mg/L) should be given.

If a spinal implant is infected, add rifampin 300 mg PO q12 hours to regimen.

When an organism is identified, suggested regimens are:

  • S. aureus or coagulase negative staphylococcus (methicillin sensitive): Cefazolin 1-2 g IV q 8 hours

  • S. aureus or coagulase negative staphylococcus (methicillin resistant): Vancomycin 1 g IV q 12 hours (goal trough 15-20 mg/L)

  • Streptococcal species: Penicillin G 5 million units IV q 6 hours (or Ceftriaxone 2 g IV q day) (If the patient has a penicillin allergy, use vancomycin.)

  • Enterobacteriaceae, quinolone susceptible: Ciprofloxacin 750 mg PO q 12 hours

  • Enterobacteriaceae, quinolone resistant or ESBL: Imipenem 500 mg IV q 6 hours

  • Pseudomonas aeruginosa: Cefepime 2 g IV q8 hours × 2-4 weeks followed by Ciprofloxacin 750 mg PO q 12 hours × 2-4 weeks.

  • Anaerobes: Clindamycin 600 mg IV q 8 hours

IV. Management with Co-Morbidities

A. Renal insufficiency.

Renal dosing is available for all medications,

B. Liver insufficiency.

If the patient is coagulopathic, weigh the risks and benefits of invasive diagnostic procedures.

C. Systolic and diastolic heart failure

No change in standard management.

D. Coronary artery disease or peripheral vascular disease

No change in standard management.

E. Diabetes or other endocrine issues

Maintain glucose <180 mg/dL throughout treatment to improve outcomes.

F. Malignancy

Chemotherapeutic agents that weaken the immune system should be used with extreme caution during treatment of vertebral osteomyelitis. Coordinate with an oncology consultant.

If the patient has indwelling vascular access for chemotherapy administration, this is the likely source of infection, and it should be removed without delay.

G. Immunosuppression (HIV, chronic steroids, etc).

No change in standard management.

H. Primary lung disease (COPD, asthma, ILD)

No change in standard management.

I. Gastrointestinal or nutrition issues

Wound healing will be slow if nutritional needs are not met; consider nutrition consultation while the patient is hospitalized.

J. Hematologic or coagulation issues

Weigh the risks and benefits of placing a PICC line in patients who are hypercoagulable or who have bleeding tendencies.

K. Dementia or psychiatric illness/treatment

These patients may not be able to receive treatment at home. Get case management involved early to assist with discharge planning.

V. Transitions of Care

A. Sign-out considerations while hospitalized.

Provide cross coverage with the current status of neurologic function and trends in the fever curve, as well as the status of cultures from blood or biopsy.

Instruct cross coverage to have a low threshold for re-imaging with MRI if neurologic symptoms worsen or if pain worsens, as an epidural abscess may have formed.

Inform cross coverage of which consultants are on the case.

B. Anticipated length of stay.

Expected length of stay is 5 to 7 days.

C. When is the patient ready for discharge?

When the patient shows a pattern of improvement in symptoms and objective markers (i.e., less pain, better muscle strength, downward-trending fever curve), he or she is ready for discharge. The patient is also ready for discharge after PT/OT makes final recommendations on where care can best be delivered (e.g., home, SNF, inpatient rehab).

D. Arranging for clinic follow-up

1. When should clinic follow-up be arranged and with whom?

Follow-up should be arranged with an internal medicine physician within one week of discharge to ensure timely and effective administration of antibiotics and to re-assess the neurologic status of the patient. An internist should be able to follow up with safety labs, to monitor drug levels, and to follow up on any pending cultures from the hospital visit.

If the patient had a surgical intervention, then follow up with that surgical specialty should be arranged after a first visit with an internist.

2. What tests should be conducted prior to discharge to enable the best first clinic visit?

If the cause of vertebral osteomyelitis is high-risk behavior (e.g., IVDA), then testing for HIV, hepatitis B, and hepatitis C before discharge with follow-up of results before discharge or at the time of first clinic visit is ideal.

3. What tests should be ordered as an outpatient prior to or on the day of the clinic visit?

ESR and CRP should be checked at four weeks after initiating therapy.

A set of "safety labs" (e.g., BMP, CBC) to monitor the toxicity of certain antibiotic treatments.

E. Placement considerations.

The patient will need a PICC line for extended IV antibiotic therapy. Choosing a regimen with once or twice daily dosing is optimal so that a home health agency can coordinate the administration of the drug.

If home health is not an option because of the patient's lack of health care benefits or need for a more complex treatment regimen, check with your case manager to see whether there is an infusion center the patient could attend to receive therapy or whether a SNF will accept the patient.

Obtain PT/OT consultation early in the hospital stay to anticipate discharge needs, particularly if there are neurologic deficits noted on admission.

F. Prognosis and patient counseling.

There is an 80%-90% survival rate at 1 year without relapse with 6 weeks of antibiotic therapy, but there is more chance of relapse if concomitant endocarditis is present. In general, if a patient walks into the hospital and diagnosis is not delayed, he or she will walk out of the hospital.

VI. Patient Safety and Quality Measures

A. Core indicator standards and documentation.

None identified.

B. Appropriate prophylaxis and other measures to prevent readmission.

Fall precautions

DVT prophylaxis

Rehabilitation and abstinence from IV drug use

What is the evidence?ZimmerliW. Vertebral osteomyelitis. N Engl J Med2010;362:1022-9.LavyCJamesAWilson-MacDonaldJFairbankJl. Cauda equina syndrome. BMJ2009;338:b936.RybakMJLomaestroBMRotschaferJC, et al. Vancomycin therapeutic guidelines: a summary of consensus recommendations from the Infectious Diseases Society of America, the American Society of Health-System Pharmacists, and the Society of Infectious Diseases Pharmacists. Clin Infect Dis2009;49:325-7.BagatellSJWeimerSMVanDykeRBBraceySV. Neck pain. Clin Pediatr (Phila)2007;46:280-2.WintersMEKluetzPZilbersteinJ. Back pain emergencies. Med Clin North Am2006;90:505-23.KowalskiTJLaytonKFBerbariEF, et al. Follow-up MR imaging in patients with pyogenic spine infections: lack of correlation with clinical features. AJNR Am J Neuroradiol2007;28:693-99.YoonSHChungSKKimKJ, et al. Pyogenic vertebral osteomyelitis: identification of microorganism and laboratory markers used to predict clinical outcome. Eur Spine J2010;19:575-82.MarschallJBhavanMJOlsenMA, et al. The impact of prebiopsy antibiotics on pathogen recovery in hematogenous vertebral osteomyelitis. Clin Infect Dis2011;52:867-72.CornettCAVincentSACrowJHewlettA. Bacterial spine infections in adults: evaluation and management. J Am Acad Orthop Surg2016;24:11-8.BerbariEFKanjSSKowalskiTJ, et al. 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. Clin Infect Dis2015;61(6):e26-46.
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