O&T: Spinal Infections Flashcards
Classifications of Spinal infections
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
Changes in epidemiology
Past: TB spine
Current: Staph. aureus
Source of infection
- ***Haematogenous
- ***Direct inoculation (Iatrogenic: surgery, injection)
- Contiguous spread
- ***UTI (most common)
- Dermal infection
- IVDU with contaminated syringes
- GI / Pelvic infection
- RTI
- Oral cavity
Timeframe
Chronicity:
- Acute (<6 weeks)
- Subacute (6-12 weeks)
- Chronic (>12 weeks)
Risk factors
- IVDU
- Immunocompromised (DM, long term steroids)
- CRF
- Malnutrition
- Chronic alcoholism
- Post-irradiation (e.g. Radiotherapy of NPC damaging mucosal layer protecting spine)
***Clinical presentations of Pyogenic spondylitis vs TB spondylitis
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
***Investigations of Spinal infections
- Blood tests
- CBC + D/C
- CRP, ESR
- Blood culture - Radiographs
- Diagnosis
- Monitoring
- Prognostication - MRI
- Disease extent
- Presence + Extent of abscess
- Spinal cord compromise - CT
- Guide for biopsy
- Extent of abscess, Use of contrast
- Extent of bone destruction
- Canal compromise - Radionuclide scan
- Gallium 67 scan - PET-CT
- Biopsy
- Gold standard
- Diagnostic
- Prior to antibiotics
- AFB smear and culture - TB investigations
- PCR
- IFNγ release assays (IGRA)
- Core for histology
- Tuberculin skin test
Investigations: Blood tests
- CBC, D/C
- 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 - Blood culture +ve (25-59%)
- during fever, multiple sites
- 80-85% have bacteriological diagnosis - Urine culture (from SpC O/T)
Investigations: Radiographs
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)
Investigations: MRI
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
Difference between infection and tumour
Pyogenic infection:
- Usually Vertebra only
- Preferentially destruct Anterior spine
Tumour:
- Vertebra + Disc
Investigations: CT
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
Investigations: Radionuclide scanning
- Tc-99 bone scan
- not specific for infection - ***Gallium 67 scan
- detection of osteomyelitis - Indium 111 WBC scan
- useful for detecting abscesses
- not recommended, poor sensitivity
Indication:
- Bone lesion not well localised
- ***Post-op infection
Investigations: PET-CT
Use:
- Diagnosis of early ***post-op infections
Investigations: Biopsy
**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
Investigations: TB investigations
- ***PCR
- can be done even in formaldehyde solution / paraffin-embedded specimens - ***IFNγ release assays (IGRA)
- whole blood plasma
- immune reactivity to M. Tb within 24 hours - ***Core for histology
- if patients already on antibiotics (fewer bacteria in blood samples)
- adequate tissue sample
- wide bore needle - Tuberculin skin test
Causative bacteria in Spinal infections
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)
Antibiotics treatment
***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
Causative agents in Immunocompromised patient
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)
Duration of antibiotics
Very variable: few weeks to few months
***Depends on:
1. Clinical
2. Serological (ESR, CRP)
3. Radiological (routine plain X ray)
***Antibiotics: Pyogenic infections
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
***Indications for operation
- Uncertain diagnosis
- Multiple intraoperative cultures - Decompress a clinically significant abscess
- Drain abscess
- Debridement of sequestered (bone + necrotic) bone and disc
- Decompress spinal cord - Failed non-operative treatment
- Neurological deficit / deterioration (refers to TB)
- Progressive deformity / instability
- Stabilise spine
- Prevent / Correct deformity
(6. Severe pain (from SpC O/T))
***Surgical treatment principles
- ***Drain abscess
- Multiple intraoperative ***cultures (get it once and for all)
- ***Debridement of sequestered (bone + necrotic) bone and disc
- Decompress spinal cord
- Stabilise spine
- Prevent / Correct deformity
Surgical principles
- Anterior approach
- Debridement
- Reconstruction of anterior column - Avoid instrumentation but not absolutely CI
- risk of seeding / biofilm formation - 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 - Bone graft to enhance structural strength
- anterior column support
