Spine

The guidelines are published by the Infectious Disease Society of America. These guidelines include evidence and opinion-based recommendations for the diagnosis and management of patients with native vertebral osteomyelitis treated with antimicrobial therapy, with or without surgical intervention.

Native vertebral osteomyelitis in adults is often the result of hematogenous seeding of the adjacent disc space from a distant focus.

It is a rare spinal condition, native vertebral osteomyelitis is the most common form of hematogenous osteomyelitis for patients 50 to 70 years of age.^.

Native vertebral osteomyelitis (NVO) can be a difficult disease to diagnose as the symptoms are non-specific. These symptoms could be a back pain that does not relieve, fever, and elevated inflammation markers.

The new guidelines present a comprehensive framework for proper clinical diagnostics and treatment of the condition.

Here are the recommendations.

When to Suspect Native Vertebral Osteomyelitis

NVO should be suspected in patients with

• New or worsening back or neck pain and fever
•  New or worsening back or neck pain + elevated ESR or CRP
• new or worsening back or neck pain and bloodstream infection or infective endocarditis (strong, low).
• Fever and new neurologic symptoms with or without back pain
• New neck or back pain, following a recent episode of Staphylococcus aureus bloodstream infection

Recommendations for Diagnostic Work Up

• Medical and motor/sensory neurologic examination

• Obtain bacterial (aerobic and anaerobic) blood cultures (2 sets) and baseline ESR and CRP
• Spine MRI

• If MRI is contraindicated (eg, implantable cardiac devices, cochlear implants, claustrophobia, or unavailability) or unavailable, consider one of the following

• • Spine gallium/Tc99 bone scan
  • Computed tomography scan
  • Positron emission tomography when MRI cannot be obtained
• Special tests
  • Consider blood cultures and serologic tests for Brucella species in patients from endemic areas for brucellosis
  • Fungal blood cultures in patients at risk for fungal infection
  • Tuberculin test purified protein derivative test or an interferon alpha release assay in patients at risk for Mycobacterium tuberculosis NVO (endemic areas, low immunity, HIV)

• Aspiration/Biopsy
  • When clinical, laboratory and imaging studies suggest NVO and microbiologic diagnosis has not been established by blood cultures or serologic tests.

• • In patients with S. aureus, S. lugdunensis, or Brucella species bloodstream infection
  • Not recommended in patients with suspected subacute NVO (high endemic setting) and strongly positive Brucella serology (strong, low).
  • Addition of fungal, mycobacterial, or brucella cultures on image-guided biopsy and aspiration specimens should be done in patients with suspected NVO if epidemiologic, host risk factors, or characteristic radiologic clues are present (weak, low).
  • Histopathology/cytology if sufficient sample is available

• Repeat Aspiration Biopsy/ percutaneous endoscopic discectomy and drainage/Excisional Biopsy
• Growth of skin concomitants from previous aspiration and the absence of concomitant bloodstream infection
• To exclude difficult-to-grow organisms (eg, anaerobes, fungi, Brucella species, or mycobacteria) in negative first image-guided aspiration biopsy

Treatment Recommendation for Non-Vertebral Osteomyelitis

If the patient is normal, stable hemodynamics and stable neurologic examination  – wait for culture and sensitivity before starting antibiotic therapy.

Empirical antibiotic therapy should be started in cases of hemodynamic instability, sepsis, or severe or progressive neurologic symptoms. The antibiotics can be switched to specific antibiotics.

Antibiotics are recommended for a period of six weeks.

In case of  Brucella species infection, antibiotics are given for 3 months.

Antibiotic agents that can be onsidered are given in the table

Indications for Surgery

• Progressive neurologic deficits, progressive deformity, and spinal instability with or without pain despite adequate antimicrobial therapy.

• Surgical debridement with or without stabilization in patients with persistent or recurrent bloodstream infection  if another source without alternative source has been ruled out
• Worsening pain despite appropriate medical therapy

It is advised to refrain from surgery in with worsening bony imaging findings at 4–6 weeks in the setting of improvement in clinical symptoms, physical examination, and inflammatory markers.

Follow Up

• Monitoring systemic inflammatory markers (ESR and or CRP) after approximately 4 weeks of antimicrobial therapy, in conjunction with a clinical assessment.
• A follow-up MRI to assess spinal tissues in patients with  are judged to have a poor clinical response

Treatment Failure

Unchanged or increasing values of serum markers [ESR and CRP] after 4 weeks of treatment along with clinical assessment should bring suspicion of treatment failure.

• Obtain a follow-up MRI
• Obtain additional tissue samples for microbiologic either by aspiration biopsy or by open surgery.
•  surgical sampling

Samples should be for histopathology, aerobic and anaerobic bacterial cultures, and fungal, brucella, and mycobacterial cultures. In select circumstances, serologic assays for uncommon causes should be considered as well.

Source

Spinal tuberculosis  with neural deficit can occur in the lesions when disease comrpresses the cord. Potts paraplegia is term for this deficit in TB spine

Spinal tuberculosis  is the most common form of skeletal tu­berculosis accounting for 50 percent of osteoarticular tuberculosis. Neural compression in spinal tuberculosis may lead to tetraparesis-tetraplegia or paraparesis-paraplegia.

Pathology of Neurological Complications in Spinal Tuberculosis

A neurological complication is observed mostly with dorsal spine affection because

• Most commonly affected
• Narrow canal
• Anterior longitudinal ligaments contain the abscess which produces cord compression unlike in lumbar spine where it trickles down in psoas muscle.

Pott’s paraplegia is of two types

• Paraplegia of early-onset – found in the early and active stage of the disease usually within the first 2 years
• Paraplegia of late onset-found late in the course of the disease usually many years after the apparent quiescence of the disease

Causes of Pott’s paraplegia are discussed below

During Active Disease

Extrinsic causes

• Abscess
• Granulation tissue
• Tubercular debris
• Tuberculous caseous tissue
• Localized pressure due to salient (internal gibbus)
• Pathological subluxation/dislocation of vertebrae.

Intrinsic causes

• Inflammatory edema
• The affection of meninges and cord by tu­berculous inflammation
• Infective thrombosis/endarteritis of spinal vessels

In Healed Disease

Extrinsic causes

• A transverse ridge of bone anterior to spinal cord producing localized pressure.
• Constricting scarring around/or dura.

Intrinsic causes

• Inflammatory edema.
• Stretching of cord over the internal salient leading of interstitial gliosis.

More than one cause may be acting at the same time.

Extrinsic causes of paraplegia causing compression on the spinal cord can be demonstrated objec­tively on imaging like myelography or MRI.

It has been found that up to 75 percent canal occu­pancy can occur without affecting neural status.

But, when other causative factors such as a vascular cause or mechanical instability can add to produce paraplegia at lesser canal compromise.

With magnetic resonance imaging, the cord and soft tissue could be visualized directly and the patient showing relatively preserved cord size with evidence of myelitis/edema respond well to chemotherapy with or without surgical decompression.

Predominantly fluid collection in extradural space resolves well with antitubercular chemotherapy alone, and a conservative trial is likely to be rewarding in cases who along with this finding have apparently normal cord parenchyma at the inception of treatment.

In patients with an extradural collection of mixed or granulomatous (dry) nature showing en­trapment of a normal size cord or a constric­tion of the cord with features suggestive of myelitis shows improvement in neural deficit if taken up for surgical decompression early.

Patients have significant cord compression/constriction showing strangulation with evidence of myelomalacia are those in which irreversible changes have already set in and are not likely to show a favorable response even after surgical decompression

Mild cord atrophy was observed in all patients who had excellent neural recovery after non-operative/operative treatment. In paraplegia with the healed disease, the cord was found atrophied with edema in patients having a mild neural deficit.

Staging of Neural Deficit

Frankel’s classification and ASIA Score classify the severity of neu­ral deficit in cases of acute spinal trauma. But these do not classify all types of neural deficit.

Following classification is by Tuli seems most rational, and it classifies all cases of paraplegia.

Stage I

The patient does not appreciate weakness but clinician notices clumsiness of gait and signs sug­gestive of upper motor neuron lesion (planter ex­tensor and ankle clonus)

Stage II

Patient has motor weakness, signs of upper motor neuron lesion, but power is sufficient that he/she manages to walk (motor power grade 3 or above)

Stage III

The patient is bedridden (severe mo­tor weakness) with signs of upper motor neuron paraplegia, sensory loss less than 50 percent.

Stage IV

The complete motor weakness with loss of sensation more than 50 percent and/or bladder bowel in­volvement and/or flaccid paraplegia and/or paraplegia with flexor spasm.

Lesions around conus and cauda equina present with sphincter involvement very early in the disease process and also have upper/lower motor neuron presentation.

Deficit associated with Intraspinal granuloma and with the atypical location of lesions may not always fit in the classification which accounts for less than 5 % of tuberculosis lesions.

Clinical Presentation

The patient has pain which aggravates on the movement of the spine. The pain is acute and stabbing,. Sometimes the patient may present with acute neural deficit f especially in cases of intraspinal granuloma or posterior complex disease.

Imaging

X-rays

Plain radiography can provide adequate information about a number of vertebrae involved, the level of bone destruction and the angle of kyphosis particularly in a paradiscal tuberculous lesion. The lesion is seen as rarefaction of the affected vertebrae, the fuzziness of the adjacent disc margin to complete obliteration of intervertebral disk space, the collapse of ver­tebrae leading to kyphosis of the vertebral column.

The paravertebral shadows are seen as a fusiform shadow in the Dorsal spine and increased prevertebral soft tissue shadow in the cervical spine.

The involvement of the neural arch is not well seen in a plain radiograph if the lesion is less than 1.5 cm in diameter.

Therefore the lesion is visualized on x-ray after some progression of the disease.

CT

CT scan detects bone destruction earlier than an x-ray. It can define the site and extent of bony involvement and soft tissue affection.

It is very useful in the detection of neural arch disease which could often be missed on x-rays.

CT scan shows bone destruction earlier than plain X-Rays. It helps in early detection of the tuberculous lesion and helps in evaluating the healing of the lesion. It is a good imaging tool in such location of disease which can’t be appreciated on plain x-ray such as in the junctional area of the spine.

CT guided fine needle aspiration cytology is a useful and minimally invasive method ascertaining the histological diagnosis of the ver­tebral lesion.

MRI

MRI is more sensitive for detection of the presence of musculoskeletal infection. It possesses high tissue contrast resolution with multiplanar capabilities. The lesion seen hence is more extensive than seen on plain x-ray. The better soft tissue resolution helps in evaluating the spinal cord and pre-paravertebral abscesses.

MRI can detect cord health and surrounding fluid, therefore has overtaken myelo, CT myelo to check continuity of the space.

Ultrasound

Ultrasonography can differentiate between the solid or cystic nature of abscesses.

Treatment of Pott’s Paraplegia

The best treatment of neurological complica­tions in the tuberculous spine is the prevention of para/quadriplegia by early identification and treatment.

A detailed discussion of the treatment of tuberculosis of the spine

Paraplegia of early onset (with active disease)

Tuberculosis of spine with neurological complications warrants urgent and meticu­lous care. Any delay in establishing the diagnosis and in instituting appropriate treatment is a major contributory factor to incomplete neural recovery, increased morbidity, and even mortality. Three definite methodologies has been described.

Earlier, most surgeons preferred non-operative treatment and rarely performed surgery for fear of worsening the already existing neural deficit.

Then emerged the second school of thought which advocated uni­versal surgical extirpation in all cases of tu­berculous paraplegia with the advantage of good quality and speedy neural recovery. The improved drug penetration was achieved since surgical decompression removes a fibrous barrier to drugs and the diagnosis is established beyond doubt.

Both method­ology of management are extreme. An absolute non-operative approach to Pott’s paraplegia is considered unjustifiable because very valuable time may be lost, while at the same time, surgery in every patient also seems to be unnecessary for every patient.

This has been very well achieved by Middle Path Regime [named so because it stands somewhere in the middle of the above two approaches.

A judicious combination of conservative therapy and operative decom­pression when needed should form a comprehensive integrated course of treatment for tuberculosis of the spine with neurologi­cal complications.

The approach of this treatment is shown in the diagram above.

The rationale of Middle Path Regime

Tubercular liquid pus, granulation tissue, caseous tissue causing compression and inflammatory edema are amenable to non-operative treatment.

In middle path regimen, 3 to 4 weeks delay will give a chance for above-mentioned reasons of neural deficit to subside for the patient to show a neural recovery, thus, to avoid surgical de­compression in those cases which would otherwise show neural improvement.

The patient showing relatively preserved cord with evidence of edema/myelitis with the predominantly fluid collection in extradural space will resolve well on non-operative treatment.

The compression in the tu­berculous spine and thus neurological complication is a slowly developing process (exception vascular catastrophe and pathological subluxation/ dislocation). A short delay in surgical decompression does not significantly alter the long-term recovery of neurological function.

Indications of surgery in Tuberculous Para/quadriplegia

Clinical factors

• Paraplegia with rapid onset [Indicates unusually severe paralysis from the mechanical accident]
• Severe paraplegia
  • Flaccid paraplegia
  • Paraplegia in flexion
  • Complete sensory loss
  • Complete loss of motor power for more than 6 months.
• Spinal tumor syndrome [the condition shows neural deficit without any local clinical signs or changes on x-ray images]
• Recurrent paraplegia.
• Paraplegia accompanied by uncontrolled spasticity of such severity that reasonable rest and immobilization are impossible.
• Patient with massive prevertebral abscess [ Neurological signs are associated with the difficulty of swallowing/ respiration.]
• Pretreatment Kyphosis more than 60°.

Treatment factors

• Neurological complications developing during conservative treatment.
• Neural complications not showing signs of improvement after a fair trial of conservative treatment (3-4 weeks).
• Neural deficit getting worse on non-operative treatment.

Patient factors

• Painful paraplegia
  • Pain resulting from severe spasm or root compression.
• Paraplegia with onset in old age
  • Hazards of immobilization.

Surgery for Pott’s Paraplegia

The surgery aims to decompress the spinal cord. As the vertebral body is affected in almost 98% cases of tuberculosis of the spine, the surgical decompression should include full exposure of the front of the dura mater at the apex of Kyphosis.

The decompression is done by an anterior approach or anterolateral approach. Anterior decompression allows direct access to the focus of disease to expose the duramater.

Laminectomy as surgical decompression is indicated in isolated neural arch affection and in the compressive myelopathy by intraspinal tuberculous granuloma presenting as spinal tumor syndrome.

Prognosis in Tuberculous Para/ Quadriplegia with Active Disease

Factors affecting neurological recovery in tuberculous para/quadriplegia are

Age

Young patients show good neural recovery as compared to elderly patients. The children show the best neural improvement.

General Condition of the Patient.

Patients with the good nutritional state show better neural recovery. The disease in nutritionally poor patients is more aggressive as immune status is poor. Such patients tolerate surgery poorly.

Region of Spine

Cervicodorsal junction and upper dorsal spine show poor neural recovery as the canal is narrowest here.

Type of Paraplegia

The patients of neurological complications with the active disease show better neurological recovery as compared to with healed disease.

Kyphosis

he patient with severe Kyphosis show poor neural recovery. so is the case of the patients with loss of more than two vertebrae.

Duration of Paraplegia

Neurological complications of shorter duration show better neurological recovery than of longer duration because permanent changes in the cord develop in long-standing cases.

Similarly, decompression after 12 months of neurological deficit is unlikely to respond.

Progression of Neurological Complications

Rapidly developing neurological complications show poor recovery as compared to slowly developing paraplegia.

Rapidly progressive paraplegia signifies more chances of compression by disc/ sequestrae or pathological subluxation/dislocation or vascular catastrophe and permanent cord damage is more likely.

Severity of Neurological Complications

Patient presenting with severe paraplegia as stage IV paraplegia or paraplegia with flexor spasm or with sphincter involvement or with complete sensory loss show poor neural improvement whereas less severe grade of neural deficits shows a partial cord involvement thus better chances of neural recovery.

Type of compression

• Extradural compression of fluid nature resolve well on treatment, and patients show a good neural recovery.
• A preserved cord with edema/myelitis of cord on MRI would show a good neural recovery whereas the cord showing myelomalacia or syringomyelia would show a poor neural recovery.
• During surgery, if pus is drained out (wet lesion) along with extradural compression of granulation tissue, the patient is likely to show better neural recovery in comparison to thick inspissated pus, caseous tissue, fibrous tissue, bony sequestrae and disc (dry lesion).

Late-onset Paraplegia

The patient usually has a history of extensive spinal tuberculosis but made an apparent recovery. The patient has been asymptomatic apart from increasing kyphosis. The paraplegia sets after a long asymptomatic period [4-40 years]

This type of paraplegia is usually seen in patients with severe kyphosis.

Usually, dorsal and dorsolumbar spine are involved as the kyphosis does not progress so severely in the cervical and lumbar spine.

It is attributed to

• Stretching of spinal cord over internal salient.  [often on a sharp ridge at the angle of kyphosis]
• Prolonged anterior impingement from constriction caused by fibrosis around the neural element.

It is always associated with severe kyphosis.

Management

It is important to differentiate paraplegia of healed disease from a reactivation or recrudescence.

Clinically paraplegia because of reactivation/recrudescence is severe and relatively rapidly developing as compared to late-onset paraplegia with the healed lesion.

Paraplegia with reactivation/recrudescence responds early and better to treatment than paraplegia with healed lesions.

In absence of reactivation/recrudescence, anterior decompression with removal of internal gibbus. But the treatment is fraught with the complication of deterioration of neural deficit.

The risk involved is high as severe kyphosis, with costovertebral impingement makes these patients have a poor pulmonary reserve.

The pognosis in this type of paraplegia is guarded and the prospects of recovery from treatment are not very bright. Yet it is advised to attempt removal of the internal gibbus and full anterior decompression of the cord in cases of paraplegia in healed disease. There is always the danger of worsening of neurological status following and due to surgery.

Therefore, it is suggested that internal gibbus should be removed only in cases with moderate to severe paraplegia, while mild paraplegics should not be decompressed.

The best form of treatment of late-onset paraplegia is the prevention of development of severe kyphosis.

Pyogenic infection of the spine is rare, constituting only about 2-8% of overall pyogenic infection. The spectrum of pyogenic infections includes spondylitis, discitis, spondylodiscitis, pyogenic facet arthropathy, epidural infections, meningitis, and myelitis.

The incidence of spinal infections has increased recently due to globalization, improved life expectancy, comorbidities like diabetes, overuse of antibiotics, immunosuppression and other immunocompromised conditions and spinal surgery.

The rise in intravenous drug use is also responsible for increased incidence.

It is difficult to differentiate the pyogenic infection of the spine from degenerative processes, inflammatory disorders, metabolic disorders, and tumors.

The reported incidence is 0.2-2 cases per 100000 per year.

Men are affected twice as compared to women and peak incidence is in the sixth decade.

However, it is being reported more commonly in 20-40 years old people. This is secondary to intravenous drug abuse and HIV in­fection. This group also has more cases of the atypical location of infection and presentation.

Vertebral osteomyelitis, discitis, and epidural abscess are the types of pyogenic infections of the spine. SPondylodiscitis is the name given when vertebra and disc are affected together.

Risk Factors or Predisposing Factors for Pyogenic Infection of Spine

• Immunocompromised person
• Diabetes
• HIV positive
• Malignancy
• Chronic use of steroid
• Renal failure
• Recent spinal surgery
• Presence of intravascular devices
• Presence of focus of organisms or wound contamination
• Radiation therapy
• Smoking
• Rheumatoid arthritis
• Intravenous drug abuse
• Poor nutritional status

Pathology of Pyogenic Infections of Spine

To understand pathology, an idea about anatomy of spine is needed. Following anatomy articles would guide you through the anatomy of the spine and its constituents.

• Anatomy of spine
• Vertebral canal Anatomy
• Cervical Spine Anatomy
• Thoracic Spine Anatomy
• Lumbar Spine Anatomy
• Anatomy of Intervertebral Disc

About 95% of pyogenic spinal infections involve the vertebral body and only 5% involve the posterior elements of the spine. The difference is due to the volume of supply that anterior vertebra receives

Hematogenous spread, direct inoculation and spread from adjacent sites [contoguous spread] are main routes infections of the spine.

Infection of the spinal column may typi­cally manifest as discitis, vertebral osteomyelitis or epidural abscess.] though the spectrum includes meningitis, subdural empyema, and spinal cord abscess too.

The organism causing Pathogenic organisms reach the spine hematogenously through arteries or veins (via Batson’s plexus), or by direct inoculation from a diagnostic or a surgical procedure.

[Note: Batson venous plexus is a network of veins with no valves that connect deep pelvic veins to the internal vertebral venous plexus. These form an important route for infections and tumors to spread]

Discitis or isolated infection of the intervertebral disc occurs initially in the children and involvement of end plates is subsequent. It occurs more commonly in children because of the presence of extensive anastomosis between the metaphyseal arteries and arteries of vertebral endplates.

In adults, a small septic embolus may lodge in the subchondral spongy bone is supplied by nutrients end arteries leading to bone infarction and eventually vertebral osteomyelitis. [spondylitis]

Contiguous spread to the disc can cause discitis in addition to osteomyelitis. [Spondylodiscitis]

Spread to the adjacent vertebra occurs through anastomotic vessels between the metaphysis.

The postoperative or iatrogenic infection is caused by direct inoculation.

The lumbar spine is the most common loca­tion, followed by the thoracic and cervical spine.

Posterior surgeries at higher risk than anterior. Those surgeries where instrumentation is carried have a higher risk.

Epidural abscess the pus collection as a collection of pus and is seen in about 18% of patients with spondylodiscitis. An epidural abscess can be seen in facet joint infections and posterior infections too.

The neural deficit is seen in about 20% of the patients of pyogenic infection of the spine and in almost 50% of epidural abscess cases. The deficit results from direct infection of neural elements, compression by an abscess or due to instability.

Very rarely intradural abscess is seen.

Facet joint infection is also rare but has increased recently probably as a result of the increased elderly population, immunocompromised patients, and spine procedures.

Facet joint can result in epidural/paraspinal abscesses too.

The infection of a facet joint is often hematogenous but epidural anesthesia and spinal procedures can also cause it.

It has more acute presentation than the spondylodiscitis.

L4–L5 facet joints are most commonly involved.

Degenerated facet joints may pose an increased risk for infection.

Organisms

Gram-positive aerobic cocci are the most common organisms causing pyogenic infections of the spine. Staphylococcus aureus is the predominant organism (55%).

In infants and children, S. aureus is the commonest organism like adults but Streptococcus pyogenes is seen more frequently than in adults.

Gram-negative bacteria could be the common organism in cases where the lesion is secondary to urinary tract in­fection or instrumentation. Common gram negative bacteriae include E. coli and rarely Proteus, Klebsiella, Enterobacter, and Serratia.

Anaerobic infections are responsible for 3% of axial skeleton infections. They are more common in diabetic patients.

Main anaerobic bacgteria are Bacteroides spp., Peptococcusspp., and Propionibacterium acnes.

Pseudomonas is frequently seen in Intra­venous drug users.

Postoperative wound infection is most commonly due to S. aureus. But multiple organisms are frequently seen in this group.

Polymicrobial infections are much more common in sacral osteomyelitis.

Clinical Presentation

Presentation in Adults

A history of infection somewhere [UTI, pneumonia, skin infection] or of an organ transplant may be present. common

Gradual onset back pain is the commonest presentation. Pain is worse at night and activity may aggravate pain.

Pain may mimic mechanical back pain but paravertebral muscle spasm and stiffness may be out of proportion to pain.

A pain that wakes the patient up in the night should be investigated for infection or malignancy.

Fever is not a consistent feature. Only one-third of patients have it.

Pain may radiate to the abdomen, hip, leg, scrotum, groin or perineum.

On examination, there would be tenderness and spasm in paravertebral muscle spasm. The movements of the spine would be limited.

Atypical presentations may occur

• Acute abdomen or chest pain
• Osteomyelitis may present as non-traumatic compression fracture.
  • A patient with a fracture with fever and raised ESR is considered to have an infection
• Intra-venous drug abusers and diabetics have an acute presentation
• Progression of spinal pain to radicular signs followed by weakness/paralysis suggest
  • Formation of an epidural abscess
  • The collapse of the infected vertebra

Presentation in Children

The presentation of discitis in children depends on age.

Younger than 3 years

• Irritability
• Refusal to walk or even sit
• Prefer lying

Between 3-10 years

• Abdominal pain
• Tight hamstrings
• Back tenderness
• Rigidity

>10 years

These children usually present with predominant back pain. Marked fever is less likely. His­tory of trauma may be present but usually unrelated to the cause of infection.

In infants, vertebral osteomyelitis pre­sents  with pain, fever, gibbus, raised leucocyte count, and com­plete dissolution of the vertebral body. These patients require a very aggressive treatment.

Post-operative infection

Postoperative wound infection is most of­ten diagnosed between 10 days and 2 weeks. Fever beyond the first few days, and continued wound discharge beyond 10 days and discharges which initially wanes and then increases often indicate infection.

Fever may not be present in nearly half the patients. Treatment must be initiated aggres­sively and early on the basis of clinical diag­nosis.

Differential Diagnoses

Degenerative spine

• Primary tumors or Metastases
• Disc herniation
• Vertebral compression fracture
• Inflammatory spondyloarthropathies
  • Ankylosing spondylitis
  • Reactive arthritis

• Visceral Infection/inflammation
  • Pyelonephritis
  • Appendicitis
  • Abdominal abscess

Lab Studies

The white blood cell count is often normal. It may be elevated in 35-50% of patients but rarely exceeds 12,000 cells/mm3.

An elevation of the erythrocyte sedimentation rate (ESR), is usually seen in almost all cases.

CRP, like ESR, is also elevated in most of the patients. Serial measurements of both can be used to monitor disease progression. CRP is said to be more reliable than ESR.

Blood, urine and any other infective focus should be cultured.

About 50% of the patients have blood cultures positive.

Cultures help to isolate the organism and are helpful in guiding the choice of antimicrobial therapy.

If the cultures listed above are negative, tissue should be obtained from the lesion by CT guided percutaneous needle biopsy can be performed.

In difficult cases, open biopsies may be considered.

Whenever possible, antibiotics should be held until cultures have been obtained.

Biposy, tisssue cultures for fungi and mycobacteria may also be done where there is a higher suspicion for such infections [A subacute presentation, negative gram stain, and bacterial culture.]

Imaging

X-rays

The nonspecific changes of infection may take as long as 2 to 12 weeks to appear in plain radiographs. The earliest changes usually observed are an erosion of the endplate and loss of disc height, and these usually occur within 3 to 6 weeks.

More destructive changes occur during the next 6 to 12 weeks, which includes osteolytic compression of the ver­tebral body, paravertebral soft tissue shad­ows.

With the progress of infection, the erosion of the end-plate and adjacent bone becomes more prominent. This leads to the narrowing of the disc space and segmental collapse.

Reactive sclerosis may be observed after 2 months, followed later by bone bridges across the disc, and then, typically, autofusion. Fusion may take as long as 5 years.

Others develop a fibrous union.

Children with discitis present early radiological findings. Narrowing of disc space may be observed within 2 weeks of first symptoms. Endplate erosion occurs later, progressing to reactive sclerosis without vertebral body destruction. Restoration of disc height may occur within 3-12 months with successful early treatment.

Radionuclide Bone Imaging

Radionuclide bone scanning is able to identify infection in the early days.

Sequential bone/gallium imaging and 67Ga-SPECT are currently the radionuclide procedures of choice.

The specificity of bone scintigraphy is in the range of 75–80%.

CT

CT offers a superior definition of extra-spinal soft-tis­sue abscess and epidural abscess. It is also useful in distinguishing between pyogenic and tubercular infections and tu­mors.

The pyogenic infection causes diffuse bony destruction and soft tissue involve­ment whereas tuberculosis exhibits patchy lytic le­sions with sclerosed margins at times, and a large well defined paravertebral mass or abscess.

CT scan with metrizamide myelography may be useful to define epidural abscess. The commonest use of the CT lies in CT guided biopsy and aspiration of the paravertebral abscess.

CT scan is particularly useful tool for surgical planning too.

MRI

This is the most helpful diag­nostic imaging test for pyogenic infection in the spine. MRI is more sensitive than the bone scan and became the gold standard in the evaluation of pyogenic infections of the spine.

It has a sensitivity of 96%, a specificity of 92%.

MRI is especially helpful in detecting the epidural abscesses that often have signal characteristics similar to CSF and may be missed in unenhanced MRI, but show rim enhancement with gadolinium. T

MRI can also be used for monitoring of the treatment response.

Treatment

If recognized early, the treatment is simple and effective but is often recognized late due to the non-specific picture of the disease.

The goals of treatment are relief from pain, regaining neural functions if affected,  eradicate infection, prevent relapse, and establish spinal stability.

Conservative treatment

The conservative treatment consists of following

• Identification of organism
• Appropriate antibiotics
• Spinal immobilization
• Monitor for progression of disease and evidence of spinal instability

After samples are sent to the lab for microbiological diagnosis, the patient is put on bed rest or spine is immobilized, depending on the site of disease. Tissue diagnosis may be required in certain cases.

Cervical spine is placed in a halo halo immobilization or cervical collar.

For rest of the spine, bed rest is prescribed until the pain diminishes and then a brace [TLSO] is provided for becoming upright.

Spinal immobilization and activity restriction should be continued for 10–12 weeks or until radiographic evidence of healing is present.

Either the antibiotics are held until the organism is identified or started on empiric broad antibiotic therapy based on the clinical assessment.

Once an organism has been identified, antibiotics should be administered intravenously for 4-6 weeks. It is followed by oral antibiotics for the next 6-8 weeks. The total duration of antibiotic therapy is 12 weeks.

Choice of antibiotics is guided by the sensitivity report. A rough guide of various antibiotics used is given below.

 Gram positive bacteria i.e. Staph Aureus

Pencillinase producing

• Semisynthetic Peniciliin
  • Oxacillin
  • Nafcillin
• First generation cephalosporins
  • Cephalothin
  • Cefalexin
  • Cefazolin
• Second generation cephalosporin
  • Cefuroxime

Methicillin resistant

• Vancomycin
• Teicoplanin
• Tigercyline
• Daptomycin

Gram Negative Bacteria

Pseudomonas aeruginosa

• Ticaricillin
• Piperacillin
• Mezocillin
• Ceftazidime
• Cefepime
• Carbapenem
• Aztreonam
• Ciprofloaxillin

Aminoglycosides [Gentamycin, Tobramycin, Amikacin] may or may not be added.

Other than Pseudomonas

• 2nd or third generation cephalosporins [as per sensitivity results]
• Resistant bacteria are treated as same as Pseudomonas

CRP level can be used to monitor the course of the disease.

Operative Treatment

Over one-third of patients fail to respond to conservative therapy.

Indications for sur­gery are

• Significant neurologi­cal impairment
• Presence of large abscess
• Severe intractable pain
• Progressive deformity
• Gross instability

Surgical treatment should

• Removal of infected tissue
• Decompression of neural elements
• Restoration of alignment
• Correction of instability

In most of the cases, anterior vertebral elements are involved in infection and intact posterior elements provide some stability, thus preventing significant subluxation.

Therefore posterior decompression like laminectomy without stabilization may my alone may further destabilize the spine.

Most of the authors advocate anterior surgeries or a posterolateral approach that preserves the laminae, facets, and pedicles.

Some recent studies have recommended additional posterior spinal fixation after anterior decompression and fusion depending on the quality of bone, the number of segments involved, and the presence of pre-existing kyphotic deformity

Bone graft is used where spinal fusion is contemplated.

Anterior decompression with or without autologous bone graft and instrumentation:

The most satisfactory method to achieve a thorough debridement of the destructive lesion is by an anterior approach. It is often nec­essary to use autograft or allografts to restore stability.

Instrumentation may be done to decrease the need for prolonged immobilization. Depending on the condition of the lesion and patient, it could be done as a single stage procedure or in two stages.

Posterior decompression without fusion

As mentioned before, isolated posterior decompression fur­ther destabilizes the spine producing pro­gressive deformity and worsening the neurologi­cal deficit. In rare instances, when infection principally involves posterior ele­ments, or the epidural abscess is posterior or lateral to the dural sac, a laminectomy may be indicated.

Posterior decompression with fusion and instrumentation

Extensive surgery than just a abscess drainage is required when the disease includes anterior elements too. To approach the disease posteriorly various approaches like posterolateral approaches, transpedicular decompression or costotransversectomy approaches are often required to achieve decompression.

Following debridement, it is usually necessary to restore stability with interbody bone grafts, using autograft rib or fibular allograft. Posterior instrumentation is often required for adequate stabilization.

When instrumentation is required, it could be done in the second stage after the posterior wound is healed following the initial debridement.

Alternately one stage procedure can be done.

Complications

• Pharyngeal abscess in cervical spine lesions
• Mediastinitis in thoracic spine lesions
• Epidural abscess
• Subdural abscess
• Meningitis
• Segmental collapse with spinal instability
• Progressive neurological defici