Introduction

Background

Diskitis is an inflammation of the vertebral disk space often related to infection. Infection of the disk

space must be considered with vertebral osteomyelitis, as these conditions are almost always

present together and share much of the same pathophysiology, symptoms, and treatment.

Although diskitis and associated vertebral osteomyelitis are uncommon conditions, they are often

the causes of debilitating neurologic injury. Unfortunately, morbidity can be exacerbated by a delay

in diagnosis and treatment of this condition. The lumbar region is most commonly affected,

followed by the cervical spine and, lastly, the thoracic spine.1,2,3,4,5 See images below.

Axial CT scan in a patient with diskitis demonstrates extensive destruction of the

vertebral endplate. Note the preservation of the posterior elements, including

facet joints, lamina, and spinous process. This is characteristic for pyogenic

diskitis and less common in tuberculosis (Pott disease).

Sagittal T1-weighted MRI of the lumbar spine in a 74-year-old man, revealing

diskitis of the L4-L5 disk space. Note extensive destruction of the endplates of

the adjacent vertebral bodies. No compression of the thecal sac is present,

which is an important consideration when contemplating surgical intervention.

Contrast-enhanced sagittal T1-weighted MRI image in a 55-year-old woman

shows thoracic diskitis with an associated epidural abscess and spinal cord

compression. Because of the significant cord compression, this patient

underwent surgical decompression.

Trajectory of a needle in a biopsy of the infected disk space guided by CT scan.

Care is taken to avoid the thecal sac and nerve roots.

Recent studies

Sharma et al reported on the severe complication of diskitis following diskography. They found that

based on the available clinical evidence, IV or intradiskal antibiotics during diskography have not

been conclusively shown to decrease the rate of diskitis over sterile technique alone. Animal

model research supports prophylactic antibiotic use when used before iatrogenic inoculation of

intervertebral disks. Both single- and double-needle techniques when used with stylettes are

superior to nonstyletted techniques, according to the authors.6

Maus et al studied procalcitonin (PCT) as a diagnostic tool and monitoring parameter for

spondylodiskitis and for discrimination between bacterial infection and aseptic inflammation of the

spine. A total of 17 patients with spondylodiskitis and 18 patients with disk herniation used as

controls were included in this study. The findings showed, however, that PCT is not useful as

diagnostic tool or monitoring parameter for spondylodiskitis, nor was it useful for the discrimination

between a bacterial infection and an aseptic inflammation of the spine.7

Karadimas et al retrospectively analyzed the outcome of a large series of patients treated either

nonoperatively or surgically for spondylodiskitis. The patients were divided into 3 groups: (A) 70

patients who had nonoperative treatment, (B) 56 patients who underwent posterior decompression

alone, and (C) 37 patients who underwent decompression and stabilization. At 12-month follow-up,

nonoperative treatment (group A) had failed in 8/70 patients. In 24 of 56 group B patients and in 6

of 37 group C patients, reoperation was necessary. Group A patients had no neurologic

symptoms; in group B, 11 had neurologic deficits, and surgery was beneficial for 5 of them; and in

group C, 11 patients had altered neurologic deficits.8

Pathophysiology

An infection does not ordinarily originate in the vertebra or disk space, but rather, it spreads there

from other sites via the bloodstream. Spinal arteries form 2 lateral anastomotic chains and 1

median anastomotic chain along the posterior surface of the vertebral bodies. The spinal arteries

are the origins of the periosteal arteries, which in turn give rise to metaphyseal arteries.

In the child, anastomoses between metaphyseal arteries are made by the intermetaphyseal

arteries; however, in the adult, these intermetaphyseal arteries degenerate, causing direct diffusion

from the adjacent endplate to be the only source of nutrients for the disk. Septic emboli travelling

through this arterial system enter the metaphyseal arteries, which have become end arteries in the

adult, causing a large area of infarction. Infarction of the vertebral endplates is followed by

localized infection that subsequently spreads through the vertebral body and into the poorly

vascularized disk space. Infection can then spread to the epidural space or paraspinal soft tissues.

The other anastomotic vascular system of the spine is the venous system. The venous system of

the spine, like the arterial system, also forms an anastomotic plexus (ie, Batson plexus) in the

epidural space. This plexus drains each segmental level and is continuous with the pelvic veins.

Retrograde flow through this plexus during periods of high intra-abdominal pressure has been

postulated to allow the spread of infection from the pelvic organs. Support for this hypothesis

comes from the observation that pelvic disease is one of the most common primary sites of

infection in patients with diskitis. Other authors take issue with this hypothesis, citing animal

studies that show retrograde flow through the epidural venous plexus only at extremely high intra-

abdominal pressures that are not physiologic.

Frequency

United States

Incidence ranges from 1 in 100,000 population to 1 in 250,000 population.

International

In other developed nations, the incidence of diskitis is similar to that in the United States; however,

in less developed nations, infectious diskitis is much more common. In some areas of Africa, it has

been reported that 11% of all patients seen for back pain were diagnosed with diskitis.

Mortality/Morbidity

Mortality associated with diskitis occurs from the spread of infection, either through the nervous

system or through other organs. Mortality has been reported to be 2-12%.

Race

No specific racial predilection has been noted.

Sex

The predominance of diskitis in males is more pronounced in adults, with male-to-female ratios

ranging from 2:1 to as high as 5:1. Childhood diskitis has a slight male prevalence, with a male-to-

female ratio of 1.4:1.

Age

A bimodal distribution of ages occurs with diskitis. Childhood diskitis affects patients with a mean

age of 7 years. The incidence of diskitis then decreases until middle age, when a second peak in

incidence is observed at approximately 50 years of age. Some authors argue that childhood

diskitis is a separate disease entity and should be considered independently.

Clinical

History

Unfortunately, adult diskitis has a slow, insidious onset, which can cause diagnosis to be

delayed for months. Neck or back pain with localized tenderness is the initial presenting

complaint. Movement exacerbates these symptoms, which are not alleviated with

conservative treatment (eg, analgesics, bed rest).

o In patients who are chronically ill, a high incidence of epidural extension of the

infection exists, causing lower extremity weakness or plegia. Fever, chills, weight

loss, and symptoms of systemic disease may be present but are not common. o In postoperative patients, symptoms usually begin days to weeks after surgery.

Symptoms are similar to those experienced by patients with spontaneous diskitis,

which consists of pain without neurologic abnormality. Limited movement and

localized tenderness also occur; however, superficial signs of infection are rare

(only 10% of cases). Diagnosis is rarely delayed in postoperative patients, which

is the main reason that neurologic deficit is uncommon in these cases.

The disease has a more acute course in children. A sudden onset of back pain, refusal to

walk, and irritability are the most common symptoms. Fever is often present,

accompanied by local tenderness and limited back motion.

Physical

Localized tenderness over the involved area with concomitant paraspinal muscle spasm is the

most common physical sign. If the cervical or lumbar segments are involved, restricted mobility

secondary to pain occurs. Reported rates of neurologic deficit (eg, radiculopathy, myelopathy) vary

widely from 2% to 70%. Cervical disease is associated with a much higher rate of neurologic

deficit.

Causes

Diskitis is thought to spread to the involved intervertebral disk via hematogenous spread

of a systemic infection (eg, urinary tract infection [UTI]). Many sites of origin have been

implicated, but UTI, pneumonia, and soft-tissue infection seem to be the most common.

Direct trauma has not been conclusively shown to be related to diskitis. Intravenous drug

use with contaminated syringes offers direct access to the bloodstream for a variety of

organisms. Often, no other site of infection is discovered.

Staphylococcus aureus is the organism most commonly found; however, Escherichia coli

and Proteus species are more common in patients with UTIs. Pseudomonas aeruginosa

and Klebsiella species are other gram-negative organisms observed in intravenous drug

abusers, although they are not seen as commonly as S aureus. Not surprisingly, medical

conditions that predispose patients to infections elsewhere in the body are associated with

diskitis. Diabetes, AIDS, steroid use, cancer, and chronic renal insufficiency are common

comorbidities.1

Although rare, infection of the disk space can also occur following surgical intervention at

the site. The rate of infection following anterior cervical diskectomy has been quoted at

0.5% of cases. The rate of infection for lumbar diskectomy is half of that. In such cases,

infection is transmitted through direct inoculation of the operative site. As in spontaneous

diskitis, the most common organism is S aureus, but Staphylococcus epidermidis and

Streptococcus species also should be considered.

Childhood diskitis has not been consistently associated with an initial causative infection

elsewhere in the body. S aureus is the most common organism found.

Differential Diagnoses

Osteomyelitis

Rheumatoid Spondylitis

Spinal Tumors

Other Problems to Be Considered

Spinal epidural abscess

Pyelonephritis

Rheumatoid arthritis

Workup

Laboratory Studies

Hematology o Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are

the most consistent laboratory abnormalities seen in cases of diskitis. o The mean ESR for patients with diskitis is 85-95 mm per hour. ESR utility can be

extended by serial measurements during treatment. o A 50% decline in ESR can usually be expected with successful treatment, and

ESR often continues to decline after treatment. o Frequently, ESR may not return to normal levels despite adequate therapy.

Leukocytosis is often present in systemic disease but is frequently absent in diskitis

cases. Diskitis is generally accompanied by a normal peripheral white blood cell (WBC)

count if the primary site of infection has been treated.

Microbiology o Blood cultures must be obtained on a frequent basis for any patient suspected of

harboring an infected disk. o Appropriate therapy may be instituted for positive blood cultures without the need

for invasive tests. o Unfortunately, blood cultures are positive in only one third to one half of diskitis

cases.

Sputum and urine cultures are necessary to locate any other sources of infection,

including respiratory and genitourinary sites.

Imaging Studies

Plain radiography o Although radiographic films of the spine can be very useful in diagnosing diskitis,

abnormalities are visible only after several weeks following the onset of disease. o The most common early finding on plain films is disk-space narrowing, followed

by irregularities and erosion of the adjacent endplates and calcification of the

anulus around the affected disk. o As osteomyelitis progresses, bone density decreases, with loss of the normal

trabeculation of the vertebra. If bone destruction continues, subluxation (with

possible instability of the spine) becomes evident.

Nuclear medicine o Gallium-67 and technetium-99m have been utilized in the detection of diskitis with

similar results. Radionuclide scanning has demonstrated a high degree of

sensitivity shortly after the onset of symptoms. Diffuse initial uptake is followed by

more focal uptake on delayed scans. Technetium-99m has been recommended

more often because of its lower cost and smaller radiation dose. o Because of the availability and sensitivity of other tests, radionuclide scans may

be most useful in the workup of patients with fever of unknown origin. o Indium-111 WBC scintigraphy has been shown to have a low sensitivity for

diskitis and is not the test of choice.

CT scan o CT scanning has the ability to detect diskitis earlier than plain radiographs.

o Findings include hypodensity of the intervertebral disk and destruction of the

adjacent endplate and bone, as seen in the image below, with edematous

surrounding tissues.

Axial CT scan in a patient with diskitis demonstrates

extensive destruction of the vertebral endplate. Note the

preservation of the posterior elements, including facet

joints, lamina, and spinous process. This is characteristic

for pyogenic diskitis and less common in tuberculosis (Pott

disease).

o Organisms at the affected site can also produce a gas that is easily detected on

CT scans. o The advantage of CT scans over radiographs is that associated paraspinal

disease can also be detected, especially when combined with intravenous

contrast or myelography. o Use of CT scanning can supplement magnetic resonance imaging (MRI), as it is

better at distinguishing between bone and soft tissue than MRI. o CT can help monitor successful treatment, which is accompanied by increased

bone density and sclerosis.

MRI o The most sensitive and specific test for diskitis is MRI. T1-weighted images, as

seen in the image below, show narrowing of the disk space and low signals

consistent with edema in the marrow of adjacent vertebral bodies. T2-weighted

images show increased signals in both the disk space and the surrounding

vertebral bodies.

Sagittal T1-weighted MRI of the lumbar spine in a 74-year-

old man, revealing diskitis of the L4-L5 disk space. Note

extensive destruction of the endplates of the adjacent

vertebral bodies. No compression of the thecal sac is

present, which is an important consideration when

contemplating surgical intervention.

o MRI is very useful in helping distinguish between infectious diskitis, neoplasia,

and tuberculosis. o Disk space involvement directs attention to infection, as it only is involved late in

tuberculosis and very rarely in neoplasia. o With the use of intravenous contrast, as seen in the image below, MRI, like CT,

can detect paraspinal disease (eg, paraspinal phlegmon, epidural abscess).

Contrast-enhanced sagittal T1-weighted MRI image in a 55-

year-old woman shows thoracic diskitis with an associated

epidural abscess and spinal cord compression. Because of

the significant cord compression, this patient underwent

surgical decompression.

o A large amount of paraspinal soft-tissue swelling and a psoas abscess are often

associated with spinal tuberculosis.

Bone scans are not specific for infection over inflammation; therefore, they are ineffective

in postoperative patients.

Other Tests

Echocardiography can detect bacterial endocarditis, which is a common source of diskitis

and embolic infection throughout the body.

Procedures

Needle biopsy o Needle or trocar placement into the infected area is a minimally invasive test

used to obtain histologic confirmation of the disease and tissue samples for

culture. o Yield and safety of the procedure are maximized by the use of CT scanning for

guidance (see image below).

Trajectory of a needle in a biopsy of the infected disk space

guided by CT scan. Care is taken to avoid the thecal sac and

nerve roots.

o As in blood cultures, positive tissue cultures occur in only half of biopsies,

especially if antibiotic therapy has already been initiated. In such cases, needle

biopsy can be repeated or the patient can be referred for open surgical biopsy.

Surgical biopsy o Open biopsy has been found in some studies to have the highest yield in terms of

positive cultures and diagnosis confirmation. o Open biopsy is the most invasive test.

o While some surgeons prefer to combine open biopsy with surgical debridement,

no difference has been found between antibiotics and debridement when

compared with antibiotics alone in cases of early diskitis.

Histologic Findings

The histologic findings of diskitis are similar to those of any bacterial pyogenic infection. Local

destruction of the disk and endplates occurs with infiltration of neutrophils in the early stages.

Later, a lymphocytic infiltrate predominates.

Treatment

Medical Care

Antibiotic treatment must be tailored to the isolated organism and any other sites of

infection. o Broad-spectrum antibiotics must be used if no organism is isolated; however, this

is very rare, and other disease processes (eg, spinal tuberculosis) must be

considered in the face of persistently negative cultures. o Parenteral treatment is usually administered for 6-8 weeks. Before parenteral

therapy is discontinued, the ESR should have dropped by one half to one third,

the patient should have no pain on ambulation, and there should be no

neurologic deficits.1,3

o The use of oral antibiotics following intravenous treatment has not been shown to

be of added benefit. o Any laboratory or clinical sign of persistent infection should prompt another

biopsy and continued antibiotic therapy.

Immobilization is necessary, especially in the initial stages of the disease. o Two weeks of bed rest should be followed by external immobilization with a brace

when the patient gets out of bed. o Any pain on ambulation is an indication for continued bed rest.

o The goal of immobilization is to provide the opportunity for the affected vertebrae

to fuse in an anatomically aligned position. o Generally, bracing is used for 3-6 months following initiation of treatment;

however, even with the use of appropriate antibiotics and bracing, collapse of the

vertebral segments and kyphos formation may occur.

Pain control is an important adjunct to antibiotics and immobilization.2

Surgical Care

Indications for surgery beyond open biopsy include neurologic deficit, spinal deformity, disease

progression, noncompliance, and antibiotic toxicity. The goal of surgery is to remove diseased

tissue, decompress neural structures, and ensure spinal stability. Although in most cases the

vertebrae fuse spontaneously following diskitis and osteomyelitis, operative fusion can be a useful

adjunct by allowing earlier mobilization of the patient. Despite early concerns, use of a fusion plug

and metallic instrumentation in an infected field has not been shown to impede successful

treatment.

Consultations

Infectious disease

Neurosurgery

Orthopedic spine surgery

Diet

No particular diet has been shown to have a clinical benefit in patients with diskitis.

Activity

Many authors believe that 2 weeks of bed rest with initial treatment helps prevent the development

of a kyphotic deformity. Use of an orthotic brace to help stabilize the spine while spontaneous

fusion takes place is recommended for 3-6 months. Ambulation is recommended only if the patient

has neither pain nor radiographic signs of instability.

Medication

Parenteral narrow-spectrum antibiotics should be prescribed according to the organism isolated. If

cultures are consistently negative, administer broad-spectrum antibiotics for several weeks.

Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the

context of the clinical setting.

Vancomycin (Lyphocin, Vancocin, Vancoled)

Potent antibiotic that is directed against gram-positive organisms and is active against

Enterococcus species. Useful in the treatment of septicemia and skin structure infections.

Indicated for patients who cannot receive or have failed to respond to penicillins or cephalosporins

or who have infections with resistant staphylococci. For abdominal penetrating injuries, it is

combined with an agent active against enteric flora and/or anaerobes.

To avoid toxicity, the current recommendation is to assay vancomycin trough levels after the third

dose is drawn and a half an hour prior to the next dose. Use CrCl to adjust the dosage in patients

diagnosed with renal impairment.

Used in conjunction with gentamicin for prophylaxis in patients who are allergic to penicillin and are

undergoing gastrointestinal or genitourinary procedures.

Dosing

Interactions

Contraindications

Precautions

Adult

500 mg/d to 2 g/d IV divided tid/qid for 7-10 d

Pediatric

40 mg/kg/d IV divided tid/qid for 7-10 d

Dosing Interactions Contraindications Precaution

sDosing Interactions Contraindications Precautions Dosing Interactions Contraindications Precautions Gentamicin

(Garamycin, Gentacidin)Aminoglycoside antibiotic for gram-negative coverage. Used in

combination with both an agent against gram-positive organisms and one that covers anaerobes.

Not the drug of choice (DOC). Consider if penicillins or other less toxic drugs are contraindicated,

in mixed infections caused by susceptible staphylococci and gram-negative organisms, or when

clinically indicated.

Dosing regimens are numerous; adjust dose based on CrCl and changes in volume of distribution.

May be given IV/IM.Dosing

Interactions

Contraindications

Precautions

Adult

Serious infections and normal renal function: 3 mg/kg/dose IV q8h

Loading dose and maintenance dose: 1.0-2.5 mg/kg IV and 1.0-1.5 mg/kg IV, respectively, q8h

Extended dosing regimen for life-threatening infections: 5 mg/kg/d IV/IM q6-8h

Follow each regimen by at least a trough level drawn on the third or fourth dose (0.5 h before

dosing); may draw a peak level 0.5 h after 30-min infusion

Pediatric

<5 years: 2.5 mg/kg/dose IV/IM q8h

>5 years: 1.5-2.5 mg/kg/dose IV/IM q8h or 6.0-7.5 mg/kg/d divided q8h; not to exceed 300 mg/d;

monitor as in adults

Dosing Interactions Contraindications Precaution

sDosing Interactions Contraindications Precautions Dosing Interactions Contraindications Precautions Nafcillin

(Unipen, Nallpen, Nafcil)Initial therapy for suspected penicillin-G–resistant streptococcal or

staphylococcal infections. Use parenteral therapy initially for severe infections. Change to oral

therapy as condition warrants.

Due to thrombophlebitis, particularly in the elderly, administer parenterally only for short term (1-2

d); change to oral route as clinically indicated.Dosing

Interactions

Contraindications

Precautions

Adult

250 mg to 1 g PO q4-6h

Alternatively, 500 mg to 1 g IV/IM q4-6h

Pediatric

0-4 kg (neonates): 10 mg/kg IM bid

4-40 kg: 25 mg/kg IM bid or 50 mg/kg/d PO divided qid

Alternatively, 100-200 mg/kg/d IV/IM in 4-6 divided doses

Dosing Interactions Contraindications Precaution

sDosing Interactions Contraindications Precautions Dosing Interactions Contraindications Precautions Ceftazidime

(Tazidime, Tazicef, Ceptaz, Fortaz)Third-generation cephalosporin with broad-spectrum,

gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against

resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding

proteins.Dosing

Interactions

Contraindications

Precautions

Adult

250-500 mg to 2 g IV/IM q8-12h

Pediatric

Neonates: 30 mg/kg IV q12h

Infants and children: 30-50 mg/kg/dose IV q8h; not to exceed 6 g/d

Adolescents: Administer as in adults

Follow-up

Further Inpatient Care

Once the correct treatment is implemented, monitor patients to rule out progressive

neurologic deficit.

Further Outpatient Care

Laboratory analysis o A falling ESR is consistent with successful treatment.

o Although ESR values should fall by at least one third to one half, rarely do they

return to preinfection levels. o Reduction of CRP levels has been shown to be more sensitive in some studies

than ESR.

Radiography o Serial radiographic examination is a necessity to detect bony collapse or

deformity. o Successful treatment is accompanied by appropriate changes, including sclerosis

of the endplates, on plain films and CT scans. o Nevertheless, radiographic findings are significantly slower than clinical response

and cannot be used to assess eradication of infection.

Inpatient & Outpatient Medications

Parenteral antibiotics are a requirement, even for outpatients.

Pain medications can be a useful adjunct, as they allow for increased mobilization.

Transfer

Transfer to an institution with neurosurgical or orthopedic spinal care is warranted for any

patient demonstrating neurologic decline for decompression and possible stabilization.

Deterrence/Prevention

No specific deterrence is available for diskitis except treatment of the underlying disease

(eg, diabetes, sepsis).

Complications

Neurologic deficits develop in 13-40% of patients, especially those with diabetes or other

systemic illnesses.

Long-term antibiotic therapy may lead to ototoxicity or renal toxicity.

Prognosis

Most patients are cured by a treatment protocol of antibiotics, either alone or in

combination with surgery.

Only 15% of patients experience permanent neurologic deficits.

Recrudescence of infection occurs in 2-8% of patients.

Patient Education

The significance of antibiotic regimen compliance is the single most important factor in

patient education. Incomplete treatment can lead to resistance with devastating results.

The importance of orthotic brace compliance must also be stressed.

Educate patients on early neurologic signs, and instruct patients to return for medical

attention on detection of the slightest deficit.

Miscellaneous

Medicolegal Pitfalls

The most significant pitfall associated with diskitis is failure to diagnose an epidural

abscess. A significant number of epidural abscess cases go undetected until serious

neurologic decline has occurred. Neurologic deficit is sometimes thought to be caused by

a vascular ischemic event rather than simple compression. In these cases, the prognosis

for complete recovery is unfavorable once a serious deficit has occurred.