Vertebral Osteomyelitis

Epidemiology

 

M:F =2:1

 

30-40 years

 

20% diabetic

 

50-80% identifiable source

 

Site

 

Lumbar (50%) > Thoracic > Cervical (<10%)

 

Pathogenesis

 

1.  Haematogenous

- arterial rather than venous

 

Risk factors

- UTI (40% of all cases)

- IVDU

- elderly

- respiratory infection

- immunocompromised

- DM

 

2.  Direct spread

- pelvis or psoas

- percutaneous or open spinal procedures

 

Organism

 

Staph aureus 60%

 

Streptococcus

 

Gm negative

- Ecoli, Proteus

- UTI / GUT procedures

 

Salmonella in sickle cell

 

Pseudomonas in IVDU

 

TB / Fungus

- in immunocompromised

- may require life long therapy

 

Patients

 

Elderly

IVDU

Immunocompromised

- steroids

- transplant

- DM, RA

 

Pathology

 

Initial focus at end plates

- septic emboli to end arterial circulation

- series of inter-metaphyseal artery allows infection of contiguous vertebrae

- spreads by direct extension to adjacent vertebrae unlike TB

 

Disc destruction

- disc is avascular 

- allows infection to spread here as well

- forms collection / abscess

 

Deformity

- due to body and disc destruction

- kyphotic

 

Neurology

- compression from epidural abscess

- infarction of regional supply to cord

- pathological fracture fragments

- kyphosis

 

Clinical Presentation

 

Back pain / tenderness + fever + elevated ESR

 

Diagnosis often delayed 4-6/12 due to vague symptoms

 

90% back pain

- insidious, non-mechanical, night pain

- localised tenderness

 

50% fever

 

< 10% neurological deficit

 

Bloods

 

ESR elevated > 90%

- most sensitive test

 

WCC elevated 35%

 

Blood culture's

- often negative

- especially if low virulence

 

Urine culture

 

Malnutrition

- albumin / lymphocyte count

 

X-ray 

 

Changes 4-6/52

 

Findings

- loss of disc height

- end plate irregularities/erosions

- vertebral destruction

- contiguous vertebrae

- collapse usually without severe kyphosis of TB

 

CT

 

Soft tissue involvement

Good for TB 

 

Cervical Osteomyelitis CT

 

Bone Scan

 

Localise area of problem if diagnostic dilemma

 

MRI 

 

Vertebral Osteomyelitis MRICervical osteomyelitis

 

Investigation of choice

- 95% accurate

- diagnose vertebral osteomyelitis

- look for epidural abscess

 

Early

- T1 loss of distinction between disc and end plate

- T2 loss of normal disc intranuclear cleft

- specific for infection

 

Gadolinium T1

- ring enhancement

 

DDx

 

Tumour 

- preservation of disc

 

TB 

- no increased T2 in disc

 

CT guided biopsy 

 

Indication

- If organism unknown

 

Technique

- aspiration if abscess

- bone biopsy otherwise

 

Results

- culture 75% of microbes prior to antibiotics

- only 25% after antibiotics given

 

Open biopsy

 

Indication

- if no CT available / unsuccessful

 

Technique

- posterior approach

- specimen obtained through pedicles 

- T-spine through costotransversectomy

 

Results

- culture aerobic / anaerobic / AFB / fungus

- diagnostic in > 80% cases

 

TB VS Pyogenic

 

Pyogenic                         TB

Single focus                      Multisegments involved

Symmetric collapse           Kyphosis

Spread bone                     Fascial planes

Disc destroyed                  Disc sequestered

Anterior column                All 3 columns (posterior inv)

Epidural abscess               Paravertebral abscess

More acute                       Insidious

 

Management

 

Non-Operative

 

Principles

 

1.  Important to delay antibiotics until cultures taken

- BC's

- urine M/C/S

- CT biopsy

 

2.  After biopsy

- most settle with antibiotics

- 6-8 weeks IV treatment (until ESR norm)

- continue orals 3-6/12

 

3.  Immobilisation important

- Bed rest

- TLSO

 

4.  Adequate nutrition important

- serum albumin

- WCC

- transferrin

 

5.  Spontaneous fusion occurs in 60%

 

Operative Management

 

Indications

 

1.  Biopsy for diagnosis and M/C/S

 

2.  Failure medical management

- systemically unwell

 

3.  Neurological deficit

 

4.  Deformity / instability

 

Anterior approach & corpectomy

 

1.  Adequate debridement crucial

 

2.  Autograft preferred

- iliac crest, fibula, rib

- can use allograft 

 

3.  Instrumentation

- anterior +/- supplemental posterior

 

Results

 

Lu et al Neurosurgery 2009

- review of 36 patients treated with corpectomy + titanium cage

- nearly all patients required anterior + posterior instrumentation

- 2 infection recurrences, 1 each with autograft and allograft

- all had neurological improvement

- 81% pain free