metaphyses & cartilaginous end plates - starting areas for blood-borne infections
in adults > 30 years the intervertebral disc receives its nutrition from tissue fluids rather
than from direct blood supply
Blood supply
arterial supply to the vertebrae
vertebral artery, intercostal artery, or lumbar arteries provide nutrient vessels that enter the vertebral body
posterior spinal branch arteries enter the spinal canal through each neural foramen & separate into ascending and descending branches that anastomose with similar branches at each level
intervertebral disc is centrally avascular & dependent on diffusion for its nutrition
pelvic veins drain into the spinal venous plexus - frequent metastasis of pelvic tumours & infections to the spine
Mechanism
iatrogenic infection - usually through surgical manipulation directly or percutaneously
local spread from contiguous structures
from the colon via subphrenic abscesses
arterial spread of pyogenic bacteria
most common method
originates in the end plate of the vertebra or in the vertebral body itself
spreads to the disc secondarily as the infection progresses
bacterial infections rapidly attack the intervertebral disc
TB & non bacterial infections preserve intervertebral disc
Aetiology
Organism
Staphylococcus aureus & S.epidermidis most common in pyogenic infection (60%)
increase in the resistant strains of the organism
intravenous drug users commonly infected w/ Pseudomonas aeruginosa
Mycobacterium tuberculosis is the most common nonpyogenic infecting agent
Cause
spinal surgery is the most common cause of iatrogenic disc infection
genitourinary infection most common predisposing factor for blood-borne infection
respiratory and dermal infections are less frequently implicated
decreased natural immune response
diabetes, alcoholism, rheumatoid arthritis
chronic renal disease
AIDS
Site
vertebral end plate > disc space > epidural abscess formation > paraspinal abscess
thoracic & lumbar spinal vertebrae - most common areas of pyogenic infection
thoracolumbar junction - TB
Diagnosis
Physical Examination
History
recent infection is not uncommon
immune-suppressing disease
Symptoms
pain most common 85%
w/ changes in position, ambulation
intensity varies from mild to extreme
other symptoms - anorexia, malaise, night sweat, intermittent fever & weight loss
spinal deformity late presentation of the disease
paralysis is complication - rarely is the presenting complaint
Signs
temperature elevation usually minimal
localised tenderness
paraspinal spasm
limitation of motion of the involved spinal segments
iv. antibiotics for about 6 weeks & followed by oral
until the ESR returns to normal
failure of improvement in the ESR or continued persistence of symptoms should initiate re-evaluation of the therapy, and possibly repeat biopsy or even open biopsy for cultures or to remove sequestered and infected material
Prognosis
most spinal infections resolve symptomatically and roentgenographically w/in 9-24/12
recurrence of the infection & periods of decreased immune response are always possible
delayed complications of kyphosis, paralysis & myelopathy
Indications for surgery
progressive neurology on conservative rx.
instability of spinal column
Specific infections
Pyogenic Infections
males > females
adults > children
peak ages between 45-65 years
most common organism reported is S. aureus
Infections in children
syndrome of discitis(vertebral osteomyelitis)
average age of onset 6-7 yrs
characterised by fever & >> ESR
followed by disc space narrowing on plain X-rays
frequently difficulty in walking, malaise, irritability
most culture reports are positive for S. aureus
in children younger than 6 years of age may be viral in origin
diagnosis difficult initially
plain roentgenograms usually negative
may be a mild febrile reaction, but patients do not appear systemically ill
only an elevated ESR
best test either MRI scanning or a combination of bone scanning & gallium scanning
blood cultures helpful if obtained during the initial febrile period of the illness
treatment
bed rest and immobilisation
diagnosis confirmed w/ blood cultures - intravenous AB
surgical procedures rarely are required
Disc space infection in adults
in adults intervertebral disc avascular - can't occur by a blood-borne route
surgical manipulation
incidence of disc space infection after disc surgery range from 1% to 2.8%
after discography 1% w/ single-needle technique 0.5% with the double-needle tech
infecting organism is S. aureus
diagnosis difficult and is almost always delayed
pain most common complaint
diagnostic studies - ESR, bone scan & gallium scan positive 4-6 weeks after surgery
MRI the best way to identify
biopsy - closed or open
Rx: specific or empiric antibiotics
Epidural space infection
low reported incidence - increased in immunosuppressed patients
morbidity and mortality are high
may complicate a primary disc space infection
the infection frequently spans three to five vertebral segments, even whole canal
S. aureus is the most common
clinical findings
several distinct differences:
a more rapid development of neurologic symptoms (days instead of weeks)
a more acute febrile illness
signs of meningeal irritation, including radicular pain w/ positive straight leg-raising
test and neck rigidity
MRI is critical to the determination
treatment
surgical drainage and appropriate antibiotic therapy
Brucellosis
results in a noncaseating, acid-fast, negative granuloma
caused by a gram-negative capnophilic coccobacillus
individuals involved in animal husbandry and meat processing
symptoms
polyarthralgia, fever, malaise, night sweats, anorexia & headache
psoas abscesses are found in 12% of patients
bone involvement, most frequently the spine, occurs in 2-30% of patients
X-ray
steplike erosions of the margin of the vertebral body require 2 months to develop
disc space thinning and vertebral segment ankylosis by bridging
CT scans and MRI - may show soft tissue involvement
brucella titers of 1:80 or greater; confirmatory cultures
treatment
antibiotic therapy for 4 months and close monitoring of the brucella titers
Fungal infections
noncaseating, acid-fast, negative infections
usually occur as opportunistic infections in immunocompromised patients
development of symptoms usually is slow
pain is less prominent as a physical symptom than in other forms of spinal osteomyelitis
laboratory and roentgenographic findings are similar to those of pyogenic infections
Diff.dg
tubercular infection
tumours
direct culture by biopsy is the only method of absolute determination
Aspergillus and cryptococcal infections are of special note