Infection of the bony and soft tissue structures involving the spine is a devastating and potentially fatal condition, which can result spontaneously in response to bacteremia or as a complication of surgery, injury, or procedures. This represents 2% to 4% of all osteomyelitis or infection of the bones. There are multiple confusing terms, such as discitis, vertebral osteomyelitis, pyogenic spondylitis, and Pott’s disease. Recent literature suggests that the term spondylodiscitis is the correct terminology to describe primary spinal infections. Other infection sites seem to be a localized extension.1,2
Primary infections are hematogenous. The infective organism seeds the vertebral bodies during times of bacteremia. Secondary infections are introduced into the spine via nonhematogenous routes, including trauma, surgery, and injections. Primary discitis in adults is not commonly seen in adults because the disc is avascular. It is seen secondary to vertebral osteomyelitis or is iatrogenic following a discogram, surgery, or inadvertent disc injection during a spinal procedure.
Epidemiology including risk factors and primary prevention
The incidence of spondylodiscitis is estimated at 2.4 cases per 100,000, and increases with age (6.5 cases per 100,000 in people over the age of 70).3 The mean age of diagnosis is 60 years old (range, 18-84 years). In a study of 111 patients with pyogenic vertebral osteomyelitis, researchers found that 61 patients (55%) were 60 years old or older, 54% were men, and 44 patients (40%) had an impaired immune system.4 Pyogenic spondylodiscitis is most commonly caused by Staphylococcus aureus, and secondly by Escherichia coli.3
The most common infection risk factors in order of most common to least common are:5
- Age >65 years
- Prior nonspine infection (in past 1 month)
- Spine Surgery (>1 year)
- Nonspine malignancy
- Diabetes Mellitus
- Current nicotine use
- Spine Surgery (<1 year)
- Prior spine infection
- Immune suppression or corticosteroid use
- Decubitus or other skin ulcer
- Intravenous or illicit drug use
- Spine fracture / trauma
- Indwelling catheters, intravenous cannulas
The vertebral arteries form end arteries on either side of the disc. This grants the infective organism access adjacent to the endplates. The primary site of infection is usually osteomyelitis.6 In patients under age 20, there is residual blood supply to the disc; if infection does spread to the disc, primary discitis occurs. In adults, the intervertbral disc is a relatively avascular structure and provides some protection against hematogenous spread of infection to the disc. Infection can spread locally into the disc from the adjacent vertebral osteomyelitis. The anatomy reveals that the outer two thirds of the disc is firmly adherent to the vertebral endplate, however, the central portion of the disc may be more loosely adherent and have endplate openings to allow venous drainage which can be a site of pathogen entry.
Batson venous plexus, because of its rich anastomosis with pelvic organs and its network adjacent to the intervertebral disc, is considered the most likely infectious pathway from pelvic and abdominal sources.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
An infective organism causes localized suppuration. This cuts off the nutrient supply to the disc, causing rapid deterioration. The intervertebral disc, which is acellular, offers no resistance and local tissue necrosis ensues. Collapse of the intervertebral disc space is often early. Infection then spreads anteriorly into the prevertebral space and into the psoas muscle, posteriorly into the epidural space causing an epidural abscess and/or meningitis, or longitudinally into the adjacent disc and vertebra.
Specific secondary or associated conditions and complications
In rare cases, the infection is walled off and becomes chronic because of formation of dead bone or involucrum. This can lead to recurrence of infection. In about 10% of cases, especially with Staphylococcus aureus or mycobacterial infection, systemic dissemination results in paralysis and death.
A lack of direct arterial and venous supply of the disc makes it a nidus for infection which can be difficult to treat with antibiotics.6
Spread of infection into the epidural space can cause cord compression and may lead to permanent cord damage if not decompressed within 72 hours.
2. ESSENTIALS OF ASSESSMENT
In adults, spondylodiscitis commonly presents as dull aching and insidious onset spine pain. In children, it can present as inability to walk or move and may be mistaken for muscle strain. Cervical spine infections commonly present with a stiff neck. There may be history of minor trauma. About 50% of patients give a history of fever. Patients with infection often complain of nocturnal pain. Radicular symptoms suggest epidural involvement. In subacute and chronic cases, there may be weight loss, loss of appetite, and malaise.
- There are no classical clinical signs for spine infections, but a very detailed spine and neurologic evaluation is essential.
- Tenderness and deformity of the spinous process along with muscle spasm and reduced range of motion is noted.
- Pseudoparalysis may be noted in children secondary to pain.
- Pain may be reproduced with vertical pressure on the vertebra and disc (Anvil test).
- If vertebral collapse occurs, there may be palpable deformity.
- Positive straight-leg raise tests may suggest epidural involvement.
- Associated abdominal examination might be needed to assess for the presence of psoas abscess.
- Cardiac examination may be indicated to rule out infective endocarditis.
One needs to assess if the patient can safely ambulate, whether because of pain or weakness. If there is any question of central nervous system involvement, a formal cognitive assessment would be needed.
- Complete blood count, erthrocyte sedimentation rate, C-reactive protein, and blood cultures x 3 from different sites, including aerobic and anaerobic, especially when febrile.
- The most common organism responsible for pyogenic infections is Staphylococcus aureus, followed by Escherichia coli. Fungal infections are more likely to be seen in immunocompromised individuals and intravenous drug addicts.
- Testing for human immunodeficiency virus, syphilis, and tuberculosis are recommended.
- Magnetic resonance imaging (MRI) is the test of choice.7
- Computed tomography (CT) scan can help look for osteomyelitis, sequestrum, disc space collapse, and prevertebral and psoas abscess.
- Plain radiographs are a good initial test to evaluate bone damage. If the Xray is abnormal then infection is likely.
- Technetium Tc 99m scan: this is typically positive in a few days following onset of symptoms.
- Indium-111 labeled white blood cell is a good tool for diagnosis of peridural abscess.
- Gallium citrate Ga 67 scans have been found to have a sensitivity close to 100%, with increased uptake 1 day earlier than for the Technetium Tc 99m scan. Also, gallium is helpful for chronic osteomyelitis. Gallium-citrate positron-emission tomography (PET)/CT can be useful to differentiate between spinal infections and tumors.
- PET with fluorodeoxyglucose is not affected by implants and is preferable to MRI in diagnosing spondylodiscitis in the postoperative period.
- Ultrasound has been used to diagnose discitis in infants.8 Its role is primarily to diagnose and follow-up on psoas and other prevertebral abscesses.
Supplemental assessment tools
Unfortunately, blood cultures are positive only in 50% of cases.9 Because isolation of the organism will impact treatment, vertebral biopsy is required if the blood cultures are negative. McHenry et al,10 in a Cleveland Clinic study, noted that biopsy is positive for the causative organism in about 78% of cases. CT or ultrasound-guided biopsy of the lesion is currently the most common and accurate method of securing a histopathologic diagnosis. This is crucial in subacute and chronic cases to rule out a neoplasm. Open biopsy may also be performed if the patient is being treated surgically.9
Early predictions of outcomes
Generally, the indicators of poor long-term outcome include the following:
- Presence of neurologic signs
- Longer time to diagnosis
- Hospital-acquired infection
- Level of spine involvement (cervical > thoracic > thoracolumbar > lumbosacral)
Social role and social support system
Social and home care agencies need to be involved early to prepare for after care and home antibiotic therapy.
Missing this diagnosis can have serious consequences for both the physician and the patient. Misdiagnosis of spinal infections is a frequent cause of malpractice suits. Worse still are the consequences for the patient: paralysis and even death may result.
3. REHABILITATION MANAGEMENT AND TREATMENTS
At different disease stages
Appropriate broad spectrum intravenous antibiotics for at least 4 to 6 weeks is the treatment of choice for uncomplicated infection. Patients with an undrained abscess and retained hardware with infection might need treatment for as long as 3 months.
In patients with tuberculosis, treatment with a combination of antituberculous agents is recommended for at least 12 months.
Surgical intervention is required for the following:
- Open biopsy
- Epidural/paravertebral/psoas abscess
- Neurologic deficits
- Catastrophic infections, which are not responding to nonsurgical treatment
- Infections related to foreign bodies
Delayed surgery might be needed to stabilize the spine, this is particularly true in children where there is a significant risk for kyphoscoliosis.
Outcomes are based on rapid diagnosis and treatment. Patients treated with at least 4 weeks of intravenous antibiotics revealed a 12-month survival without relapse of 88%.
Patients with vertebral osteomyelitis followed for a median of 6.5 years revealed complete recovery in 57%, relapse in 14%, and death in 11%.10 About 31% of patients had incomplete disability because of residual motor weakness, severe pain-limiting function, and isolated neurogenic bladder.
If the patient has severe cord compression, the time window for surgical decompression and potential reversal is about 24 to 72 hours.11
A multicenter study with 2,056 patients, suggested that intrawound vancomycin was associated with reduced risk of surgical site infections (SSI) after posterior approach spinal cord surgery. Spinal SSI required extended rehabilitation and were associated with further complications extending LOS.12 Another practice is to use antibacterial-coated sutures which are associated with decreased wound infections.13
Because of recent emergence of antibiotic-resistant Staphylococcus aureus, some centers are trying combination therapies. Fluoroquinolones and rifampin are some of the oral regimens being tried after patients show response to initial intravenous therapy.14
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
Spine infections are diagnostically challenging because of the different presentations. Prompt diagnosis and early treatment allows for the best chance for meaningful recovery.15 Spinal infections must be suspected in all patients with severe continuous spine pain with weight loss and unexplained fever. It is only with careful clinical examination, diagnostic testing and prompt treatment that we will be able to limit the potential damage and disability this condition can produce. These patients have more severe functional impairments on rehabilitation admission and discharge and longer inpatient rehabilitation LOS.5
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Cutting edge concepts and practice
In light of Staphylococcus aureus being the most common cause of spondylodiscitis, some studies are focused on developing a serum antibody test to help guide prophylaxis and therapy in a future of personalized medicine and pathogen-specific treatments.16
Finally, in a society where increasing antibiotic resistance is responsible for the emergence of multidrug-resistant bacteria, we must find a way to curb inappropriate use. One proposed solution is to have a multifaceted approach that integrates patient-based omics information such as genetic predisposition to infections (genomics), immune response to infection (proteomics and transcriptomics), transcriptomics, proteomics, microbiome and drug metabolism kinetics to generate accurate physician-friendly algorithms together with comprehensive pathogen profiling. This would result in more accurate diagnosis and appropriate treatments.17
Antibiotic stewardship should continue to be stressed in globally in healthcare.
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
- Tasdemiroglu, E., A. Sengoz, and E. Bagatur, Iatrogenic spondylodiscitis. Case report and review of literature. Neurosurg Focus, 2004. 16(6): p. Ecp1.
- Di Martino, A., et al., Spondylodiscitis: standards of current treatment. Curr Med Res Opin, 2012. 28(5): p. 689-99.
- Zimmerli, W., Clinical practice. Vertebral osteomyelitis. N Engl J Med, 2010. 362(11): p. 1022-9.
- Carragee, E.J., Pyogenic vertebral osteomyelitis. J Bone Joint Surg Am, 1997. 79(6): p. 874-80.
- Brubaker, M.L., M.T. Luetmer, and R.K. Reeves, Clinical features and inpatient rehabilitation outcomes of infection-related myelopathy. Spinal Cord, 2016.
- Wiley, A.M. and J. Trueta, The vascular anatomy of the spine and its relationship to pyogenic vertebral osteomyelitis. J Bone Joint Surg Br, 1959. 41-b: p. 796-809.
- Berbari, E.F., et al., Executive Summary: 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. Clin Infect Dis, 2015. 61(6): p. 859-63.
- Brown, R., et al., Discitis in young children. J Bone Joint Surg Br, 2001. 83(1): p. 106-11.
- Colmenero, J.D., et al., Pyogenic, tuberculous, and brucellar vertebral osteomyelitis: a descriptive and comparative study of 219 cases. Ann Rheum Dis, 1997. 56(12): p. 709-15.
- McHenry, M.C., K.A. Easley, and G.A. Locker, Vertebral osteomyelitis: long-term outcome for 253 patients from 7 Cleveland-area hospitals. Clin Infect Dis, 2002. 34(10): p. 1342-50.
- Liebergall, M., et al., Pyogenic vertebral osteomyelitis with paralysis. Prognosis and treatment. Clin Orthop Relat Res, 1991(269): p. 142-50.
- Devin, C.J., et al., Intrawound Vancomycin Decreases the Risk of Surgical Site Infection after Posterior Spine Surgery-A Multicenter Analysis. Spine (Phila Pa 1976), 2015.
- Ueno, M., et al., Triclosan-coated sutures reduce wound infections after spinal surgery: a retrospective, nonrandomized, clinical study. Spine J, 2015. 15(5): p. 933-8.
- Schrenzel, J., et al., A randomized clinical trial to compare fleroxacin-rifampicin with flucloxacillin or vancomycin for the treatment of staphylococcal infection. Clin Infect Dis, 2004. 39(9): p. 1285-92.
- Nas, K., et al., Rehabilitation in spinal infection diseases. World J Orthop, 2015. 6(1): p. 1-7.
- Nishitani, K., et al., A Diagnostic Serum Antibody Test for Patients With Staphylococcus aureus Osteomyelitis. Clin Orthop Relat Res, 2015. 473(9): p. 2735-49.
- Cohen, A., et al., A multifaceted ‘omics’ approach for addressing the challenge of antimicrobial resistance. Future Microbiol, 2015. 10(3): p. 365-76.
Braddom R. Physical Medicine and Rehabilitation. 2nd ed. Elsevier: 2000. Gold RH, Hawkins RA, Katz RD. Bacterial osteomyelitis: findings on plain radiography, CT, MR, and scintigraphy. AJR Am J Roentgenol. 1991;157:365-370.
Kothari NA, Pelchovitz DJ, Meyer JS. Imaging of musculoskeletal infections. Radiol Clin North Am. 2001;39:653-671.
Ross JS, Zepp R, Modic MT. The postoperative lumbar spine: enhanced MR evaluation of the intervertebral disk. AJNR Am J Neuroradiol. 1996;17:323-331.
Termaat MF, Raijmakers PG, Scholten HJ, Bakker FC, Patka P, Haarman HJ. The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systematic review and meta-analysis. J Bone Joint Surg Am. 2005;87:2464-2471.
Spinal Infections. Spine: State of the Art Reviews Vol 13, No. 1, 1999.
Wong DA. Macnabâ’s Backache. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2007.
Original Version of the Topic
Sarjoo M. Bhagia, MD, Jamal Balouch, MD, Kartik Swaminathan, MD. Spine Infections. 09/20/2013.
Vincent Huang, MD
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Raman Sharma, MD
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Conrad Fischer, MD
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