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JC Surgery + O&T > O&T: Spinal Infections > Flashcards

O&T: Spinal Infections Flashcards

1
Q

Classifications of Spinal infections

A

Causative agents (most common —> least common):
1. Bacterial
2. Mycobacterial
3. Fungal
4. Parasitic

Pathologies:
1. **Spondylodiscitis (Most common, infection of **Vertebral body + Disc space)
2. **Spondylitis (TB)
3. **Paraspinal abscess (e.g. Psoas abscess, Abscesses at paraspinal muscles)
4. ***Epidural abscess (cause neurological deficits)
5. Discitis (Children)
6. Facet joint septic arthritis

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2
Q

Changes in epidemiology

A

Past: TB spine
Current: Staph. aureus

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3
Q

Source of infection

A
  1. ***Haematogenous
  2. ***Direct inoculation (Iatrogenic: surgery, injection)
  3. Contiguous spread
    - ***UTI (most common)
    - Dermal infection
    - IVDU with contaminated syringes
    - GI / Pelvic infection
    - RTI
    - Oral cavity
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4
Q

Timeframe

A

Chronicity:
- Acute (<6 weeks)
- Subacute (6-12 weeks)
- Chronic (>12 weeks)

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5
Q

Risk factors

A
  • IVDU
  • Immunocompromised (DM, long term steroids)
  • CRF
  • Malnutrition
  • Chronic alcoholism
  • Post-irradiation (e.g. Radiotherapy of NPC damaging mucosal layer protecting spine)
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6
Q

***Clinical presentations of Pyogenic spondylitis vs TB spondylitis

A

Pyogenic spondylitis:
- **High fever
- Old
- **Short symptom to diagnosis
- ↑↑ ESR, CRP

TB spondylitis:
—> Acute: Neurology + **Back pain
—> Late sequelae (Pott’s paraplegia): Neurological deficit ∵ Reactivation, Kyphosis, Cord atrophy
- Intermittent fever
- Younger
- **Long symptom to diagnosis (∴ often cause ***kyphotic deformity, spine instability and collapse)
- ↑ ESR, CRP

***S/S:
1. Pain (90%)
2. Constitutional symptoms
3. Kyphotic deformity
4. Spine instability
5. Neurological compromise

Difficult differentiation:
- Onset
- Systemic symptoms

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7
Q

***Investigations of Spinal infections

A
  1. Blood tests
    - CBC + D/C
    - CRP, ESR
    - Blood culture
  2. Radiographs
    - Diagnosis
    - Monitoring
    - Prognostication
  3. MRI
    - Disease extent
    - Presence + Extent of abscess
    - Spinal cord compromise
  4. CT
    - Guide for biopsy
    - Extent of abscess, Use of contrast
    - Extent of bone destruction
    - Canal compromise
  5. Radionuclide scan
    - Gallium 67 scan
  6. PET-CT
  7. Biopsy
    - Gold standard
    - Diagnostic
    - Prior to antibiotics
    - AFB smear and culture
  8. TB investigations
    - PCR
    - IFNγ release assays (IGRA)
    - Core for histology
    - Tuberculin skin test
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8
Q

Investigations: Blood tests

A
  1. CBC, D/C
  2. ESR / CRP
    - High in pyogenic infection
    - Monitoring treatment response
    —> **CRP跌先: CRP normalises rapidly (∵ +ve APP)
    —> **    ESR後跌: ESR ↓ after **1 month of treatment
    —> WCC **    not useful
  3. Blood culture +ve (25-59%)
    - during fever, multiple sites
    - 80-85% have bacteriological diagnosis
  4. Urine culture (from SpC O/T)
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9
Q

Investigations: Radiographs

A

Use:
1. Diagnosis
2. Monitoring
3. Prognostication

Problems:
- **Low sensitivity + Low specificity (need a great change in structure to see changes in radiograph)
- **Delayed changes: 2-8 weeks
- Need high index of suspicion

Presentation:
- **Endplate erosion
- **Bone erosion
- **Vertebral / Disc collapse
- Reduced disc space
- Kyphosis
- **Paravertebral calcification
- **Soft tissue swelling
—> Lumbar spine (AP view): Loss of psoas shadow
—> Thoracic spine (AP view): Fusiform swelling in paravertebral shadow (from SpC O/T))
—> Cervical spine (Lateral view): Anterior cervical swelling behind esophagus
- **Spontaneous bony fusion (Fibrous ankylosis in pyogenic infection)

Features suggesting TB:
- **Multi-level involvement
- **Skip lesions
- Relative **sparing of disc
- **Subligamental (e.g. posterior longitudinal ligament) spread to adjacent vertebra
- Bony ankylosis (SpC Revision)

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10
Q

Investigations: MRI

A

Use:
1. **Disease extent
2. Presence + Extent of **abscess
3. Spinal cord compromise

***High sensitivity + specificity + accuracy
- signs appear as early as 2 weeks in 90%

Problems:
- Difficult to monitor treatment result as signal changes may ***persist after treatment (i.e. infection must be completely cleared to see normal MRI)

Marrow signal change
- **Low T1 + High T2
- Contrast differentiation a must
- **Hyperintense (lesion / inflammatory changes) + Hypointense necrotic centre

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11
Q

Difference between infection and tumour

A

Pyogenic infection:
- Usually Vertebra only
- Preferentially destruct Anterior spine

Tumour:
- Vertebra + Disc

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12
Q

Investigations: CT

A

Use (Guide for **biopsy (alternative to X ray) rather than routine assessment):
1. Extent of abscess, Use of contrast
2. Extent of **bone destruction
3. Canal compromise

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13
Q

Investigations: Radionuclide scanning

A
  1. Tc-99 bone scan
    - not specific for infection
  2. ***Gallium 67 scan
    - detection of osteomyelitis
  3. Indium 111 WBC scan
    - useful for detecting abscesses
    - not recommended, poor sensitivity

Indication:
- Bone lesion not well localised
- ***Post-op infection

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14
Q

Investigations: PET-CT

A

Use:
- Diagnosis of early ***post-op infections

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15
Q

Investigations: Biopsy

A

**Gold standard
- Diagnostic
- Prior to antibiotics
- **AFB smear and culture (grows in 6-8 weeks)

Indications:
1. Spinal lesion of uncertain diagnosis (e.g. ***no +ve blood culture)
2. Non-operative cases

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16
Q

Investigations: TB investigations

A
  1. ***PCR
    - can be done even in formaldehyde solution / paraffin-embedded specimens
  2. ***IFNγ release assays (IGRA)
    - whole blood plasma
    - immune reactivity to M. Tb within 24 hours
  3. ***Core for histology
    - if patients already on antibiotics (fewer bacteria in blood samples)
    - adequate tissue sample
    - wide bore needle
  4. Tuberculin skin test
17
Q

Causative bacteria in Spinal infections

A

Gram +ve aerobic cocci (80%)
- ***Staph. aureus (1st)
- Streptococcus (2nd)
- Coagulase -ve Staph (3rd) (S. epidermidis, S. saprophyticus)

Gram -ve aerobic bacilli
- **E. coli
- **P. aeruginosa (IVDA)
- Proteus spp.
- Salmonella (rare)

18
Q

Antibiotics treatment

A

***Avoid antibiotics before identification of organisms

Unless:
- Patients very septic
- Biopsy is difficult if not possible

Risk / Benefit of open biopsy vs Empirical broad spectrum antimicrobial treatment (can significant reduce yield in blood culture)

From SpC O/T:
- Obtain bacteriological diagnosis
- Tailor antibiotic use according to culture and sensitivity

19
Q

Causative agents in Immunocompromised patient

A

Any organisms
- Gram -ve bacteria
- MRSA
- Fungal infection
- TB

  • Tend to more aggressive
  • ***Harder to get organism before antibiotics (try if feasible)
  • ***As conservative as possible (avoid large scale surgery)
20
Q

Duration of antibiotics

A

Very variable: few weeks to few months

***Depends on:
1. Clinical
2. Serological (ESR, CRP)
3. Radiological (routine plain X ray)

21
Q

***Antibiotics: Pyogenic infections

A

Antibiotics alone successful in 75% patients
1. **Penicillin / **1st gen Cephalosporin (Cefalexin)
2. Additional **Fusidic acid / Rifampicin (good for implant related infections)
3. Immunocompromised/ IVDU: **3rd gen Cephalosporin (Ceftriaxone, Cefotaxime) + Aminoglycoside / Quinolone

MRSA:
- **Daptomycin
- **Linezolid (good bone penetration)
- Tigecycline

Mean duration:
- **2-4 weeks IV antibiotics till CRP normalised —> change to oral for **3 months
- ↑ risk of failure if <4 weeks total

22
Q

***Indications for operation

A
  1. Uncertain diagnosis
    - Multiple intraoperative cultures
  2. Decompress a clinically significant abscess
    - Drain abscess
    - Debridement of sequestered (bone + necrotic) bone and disc
    - Decompress spinal cord
  3. Failed non-operative treatment
  4. Neurological deficit / deterioration (refers to TB)
  5. Progressive deformity / instability
    - Stabilise spine
    - Prevent / Correct deformity

(6. Severe pain (from SpC O/T))

23
Q

***Surgical treatment principles

A
  1. ***Drain abscess
  2. Multiple intraoperative ***cultures (get it once and for all)
  3. ***Debridement of sequestered (bone + necrotic) bone and disc
  4. Decompress spinal cord
  5. Stabilise spine
  6. Prevent / Correct deformity
24
Q

Surgical principles

A
  1. Anterior approach
    - Debridement
    - Reconstruction of anterior column
  2. Avoid instrumentation but not absolutely CI
    - risk of seeding / biofilm formation
  3. Low propensity of adherence to Titanium than Stainless steel by bacteria
    - Anterior debridement + additional Posterior instrumentation (bacteria cannot reach posterior)
    —> Better deformity correction + Faster rate of fusion
  4. Bone graft to enhance structural strength
    - anterior column support
25
Q

Biofilm in implant

A
  1. Bacteria
  2. Glycocalyx barrier (around bacteria + sticking on implant)
  3. Implant

Glycoclayx barrier:
- Release **cytokines to attract bacteria to enter cavity
- Sugar coat provide ****nutrients to bacteria
- **Mechanical barrier to debridement (hard to scrape off, may need to remove whole implant)

26
Q

Antibiotics: Spinal TB infection

A

1st line:
- ***HREZ (Isoniazid, Rifampicin, Ethambutol, Pyrazinamide)

2nd line:
- Amikacin, Ciprofloxacin, Streptomycin, Clarithromycin

Duration:
- WHO: HREZ 2 months + HR 4 months
- American Thoracic Society: HREZ 2 months + HR 7 months
- Region dependent

27
Q

Indications for surgery in TB spine

A
  1. Neurological compromise
  2. Spinal instability / Refractory pain
  3. Progressive kyphotic deformity (>45 deg) e.g. Gibbus deformity
  4. Severe sepsis
  5. Unknown diagnosis
  6. No / Inadequate response to conservative treatment
  7. ***At-risk areas

Others:
- Age < 5 yo
- Thoracic involvement
- >2 Vertebrae
- Endplate involvement
- Facet separation
- Posterior retropulsion (may lead to spinal cord compression)
- Lateral translation
- Toppling sign

28
Q

Medical Research Counsel trials for spinal TB

A

Anterior radical debridement + Strut graft fusion
- 87% favourable outcome
- Faster relief of pain
- Earlier resolution of abscesses and sinus tracts
- No neurological deterioration
- Higher rate of earlier bone fusion
- Less deformity
- Rare for biofilm formation by M. Tb on instrumentation
- Posterior added if > 2 levels

Hong Kong operation for TB spine:
Anterior debridement + Spinal fusion
- Direct drainage of abscess
- Decompression of granulation tissue
- Stabilisation by spinal fusion (avoid kyphosis)

29
Q

Pott’s paraplegia of healed disease

A

Very difficult to treat

Causes:
1. **Internal bony ridge
2. **Fibrous tissue (in canal)
3. **Reactivation of TB
4. **Adjacent deformity (spinal fusion causing stress at adjacent segments)
5. ***Cord atrophy

Prognosis:
- Paraplegic if no surgery
- Surgical result not good generally (∵ too much deformity), majority remained paraparesis

30
Q

Clinical problem in adulthood

A
  • Prolonged cord kinking due to deformity
  • ~20 years after initial infection
  • Progressive neurological deficit if untouched
31
Q

Surgical options

A
  1. Halo-pelvic distraction
    - Multiple stages of osteotomies and fusion
    - lowest risk of neurological compromise
  2. Internal kyphectomy and strut graft
    - removal of bony prominence
  3. Closing-opening wedge osteotomy
    - higher risk procedures
32
Q

Summary

A
  1. Treatment principles
    - important to establish microbiological diagnosis of spinal infection
    - provide appropriate antibiotic
  2. Rest the spine
  3. Monitor for **spinal instability + **neurological deterioration
  4. Clinical + Serological + Radiological
  5. Get responsible bacteria during surgery
  6. Low threshold of debridement
  7. Try to avoid removing implant in early infection —> avoid instability

Indications of operation:
1. Uncertain diagnosis
2. **Decompress
- Drain clinically significant abscess
- Culture
- Debridement of sequestered (bone + necrotic) bone and disc
- Decompress spinal cord
3. Failed non-operative treatment
4. **Neurological deficits / deterioration
5. ***Progressive deformity / instability

33
Q

Treated NPC with abnormal C1/2

A

DDx:
- Infection
- Recurrence
- Avascular necrosis

34
Q

Epidural abscess

A
  • Primary vs Secondary
  • 0.2-1.2 per 10000 hospital admissions
  • Commonest organism: ***Staph aureus (60%)

Presentation:
- Local **Spine pain +/- Radicular pain
- **Acute clinical course
- ***Weakness / Paralysis
- Delay in diagnosis common (esp. Primary epidural abscess) —> infective parameters may not have time to elevate
- Rapid progression

Diagnosis:
1. High index of suspicion
2. Infective parameters
3. Blood culture
4. MRI
- Radiography may not be useful
- Biopsy not feasible in primary epidural abscess

Treatment:
1. Surgical emergency
- Spinal cord / nerve decompression
- Bacteriological diagnosis

  1. Non-operative treatment
    - Empirical antibiotic ***Vancomycin
    - absolute CI for any surgery
    - no neurological deficit
    - close monitoring
35
Q

Q fever

A
  • Acute febrile illness
  • Negative serology

***Coxiella burnetii
- Rickettsiaceae (family) (different from rickettsia)
- Gram -ve
- Obligate intracellular
- Proteobacterium
- Resistant to high temp, low pH, dessication (remain in soil for many years)
- Infect human by inhalation of aerolised organism, raw milk, fresh goat cheese

Pathogenesis:
- enter cell —> multiply within cytoplasmic vacuoles —> expand —> burst cells
- Histiocytes / Granuloma
- Doughnut appearance (central clear space surrounded by inflammatory cells and fibrin)

Prevalence:
- worldwide ~10%

Symptoms:
1. Acute
- asymptomatic, self-limiting
- flu like symptoms, atypical pneumonia, hepatitis

  1. Chronic
    - ***osteomyelitis
    - endocarditis
    - vascular infection
    - hepatitis

Phase variation and Immune process
- Complex surface structures
—> Phase 1 (virulent phase)
—> Phase 2
- IgM / IgG to Phase 1/2 antigens
—> Double edged sword: both killing and proliferation requires intracellular location

Diagnosis:
1. Culture
—> Cannot be grown with usual inoculation, not recommended as can transmit with minimal exposure
—> ***Cultivate in cell culture with animal embryo

  1. Serological diagnosis
    - IFA, CF, ELISA
  2. Pattern (Ratio of ***Phase 2:1 antigen)
    - >1 acute
    - >=1 subacute
    - <1 chronic
    - Phase 1 Ab titre >200 diagnostic of chronic active infection

Treatment:
- Doxycycline + Quinolone (prolonged / until Ab titre falls)
- Prevention
—> eradicate herd, vaccination for cattles
—> vaccines for high risk groups

JC Surgery + O&T (10 decks)

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