9. Infections Flashcards
Diabetic, steroid-immunosuppressed, and
hemodialysis patients are particularly vulnerable
to
suppurative osteomyelitis
mc source/spread of osteomyelitis
Hematogenous
4 Major Pathways of Spread of Suppurative
Osteomyelitis:
- Hematogenous
- Spread from contiguous source of infection
- Direct implantation
- Postoperative infection (iatrogenic)
- Fever
- Chills
- Pain
- Swelling
- Loss of limb function
- Elevated WBC
- ESR, +CRP
Suppurative Infection Infants/Young Children
- Chronic, insidious process
- Fever
- Malaise
- Edema
- Erythema
- Pain
Suppurative Infection
in Adults
Boys between ages 2-12 are most
susceptible to
suppurative osteomyelitis
Usually affects large tubular bones of
extremities
suppurative osteomyelitis
Diaphyseal and metaphyseal vessels penetrate physis to enter epiphysis
Infantile Vascular Pattern of infection
Physis becomes effective barrier around age
8-18 months
High incidence of septic arthritis with epiphyseal
involvement in
infantile osteomyelitis
Slow turbulent blood flow in metaphysis
rendering great environment for infection
with no metaphyseal vessels penetrating the
physis
Childhood Vascular Pattern of infection
In adults communication between epiphysis and
metaphysis occurs via
blood vessels that
gradually penetrate physis as it fuses
Increased intramedullary pressure in bone due to
pus formation
Hyperemia adjacent to infarction that stimulates
osteoclastic activity resulting in
regional osteoporosis
Infection penetrates endosteum entering Haversion systems crossing cortex to the
subperiosteal space
Few Sharpe’s fibers attaching periosteum to cortex in children, thus periosteum is easily stripped away
from cortex which results in
periostitis aka periosteal reaction
Cortical and medullary infarcts result in
Sequestrum
Dead bone
to wrap or cover
involucrum
defect in involucrum which decompresses bone by discharging inflammatory products
from bone
Cloaca
Associated with chronic osteomyelitis and allows seeding of adjacent soft tissues
Cloaca
Chronic ulcer with draining sinus, that has
become malignant
Marjolin Ulcer
defined as the
malignant degeneration of a chronic wound or scar
Marjolin’s Ulcer
On biopsy Marjolin’s Ulcer have been most commonly identified as
squamous cell and basal cell carcinomas
If even remote clinical suspicion of bone
infection, do
bone scan or MRI
MRI with and without Gd contrast is Excellent for Detecting
Infection
Soft tissue findings on plain film may be seen within
__ days of bacterial contamination of bone
3
Bone sequestrum occurs ~3-6 weeks after onset usually appear
sclerotic
90% of infections involve
extremities
Highest incidence of suppurative spondylitis occurs in
debilitated patients (50-60)
cortical erosion and
intramedullary sequestrum seen in
Chronic Osteomyelitis
mc complaint in spinal infection
Back pain
what % of the time is spinal infection misdiagnosed?
33%
- < 20
- Loss of disc height
- Paraspinal edema (abscess)
- Endplate destruction patchy lysis of vertebral body
disc infection
Initial focus of Irregularity and radiolucency at anterior vertebral endplate
Adult Spondylitis
a spreading diffuse
inflammatory process with formation of suppurative/purulent exudates or pus.
Phlegmon
Localized aborted form of suppurative osteomyelitis
Brodies Abscess
Presentation mimics osteoid osteoma with localized limb pain that is nocturnal; alleviated by aspirin
brodies abscess
Usually have had distant infection that has seeded to bone and mc male children
Brodies Abscess
what is mc found with Brodies Abscess,
however lesion may be sterile
Staphylococcus Aureus
Oval, elliptical, serpiginous, radiolucency with
margin of heavy reactive sclerosis usually >1.0cm
Brodies Abscess
Brodies abscess MRI findings
Variable signal internally, with low signal of marginal sclerosis
(penumbra sign)
Eccentrically located
radiolucent lesion crossing
the epiphyseal plate
Brodies Abscess:
Subacute osteomyelitis
Proper ID of pathogen is essential for TX of
Chronic Osteomyelitis (MC Staphylococcus aureus)
Sclerosis, cortical thickening, periosteal reaction
(laminated or solid), lysis, sequestra
Chronic Osteomyelitis
Why might antibiotics not help much for chronic osteomyelitis?
blood supply
is separated from organisms due to bone
fragmentation
Leading cause of death in Western Society at
beginning of 20th Century from Inhalation of Mycobacterium tuberculosis
Non-Suppurative Osteomyelitis:
Tuberculosis (TB)
Infection of the musculoskeletal system from TB is
commonly caused by
hematogenous spread of primary pulmonary focus
Insidious back pain, decreased ROM, focal
tenderness NOT accompanied by fever,
night sweats, toxicity, or prostration
Non-Suppurative Osteomyelitis:
Tuberculosis (TB)
sudden onset of lower limb paraplegia
Pott’s Paraplegia
70% of TB patients are
<5yo
Pott’s Paraplegia is associated with
TB
Tubercular Spondylitis, aka
Pott’s Disease
Pott’s Disease is mc in
lower thoracic and upper lumbar spine
Pott’s Disease spreads via
Batson’s venous plexus
What is initially involved, in Pott’s disease?
Subchondral anterior vertebral endplate
Tubercular Spondylitis: Pott’s Disease, spreads by into the disc by
direct extension into disc as vertebral body
collapse occurs
- Abscess formation
- Subligamentous dissection
- Granulomatous formation
- May cause Pott’s paraplegia
Paravertebral soft tissue involvement from Pott’s Disease
Calcification of psoas abscess indicates
healing of abscess in muscle and inactivity of
infection
Computed tomographic scan of the abdomen showing a left iliopsoas abscess (arrow) that likely originated from
tuberculous osteomyelitis
Extensive paraspinal abscess formation with little osseous involvement
Subligamentous Dissection
Produces shallow erosion of anterior vertebral body that resembles lymph node or aortic aneurysm erosion
Subligamentous Dissection
Subligamentous extension may lead to Pott’s disease (disc space narrowing with vertebral
collapse) resulting in
Gibbus Deformity
Subligamentous extension may lead to Pott’s disease (disc space narrowing with vertebral
collapse) resulting in
Gibbus Deformity
Advanced TB causing multiple level collapse with infection and disc deterioration
Pott’s Paraplegia
75% of Tubercular Arthritis affect
hip and knee
Initial lesions of Tubercular Arthritis simulate
RA since affects bare
areas of joint initially
– Nonuniform destruction of joint
– Cartilage and bone destruction with sequestrum
formation
Tubercular Arthritis
Low grade TB results in hyperemia which causes
localized osteoporosis
21 days latent radiographic period, Early changes include lytic destructive lesion
places in anterior corner of vertebral endplate,
coupled with loss of disc space height
Tubercular Spondylitis
Displacement of paraspinal line (extrapleural sign)
and Usually affects TL junction, usually L1
Tubercular Spondylitis
Pear shaped configuration that frequently calcifies
Tubercular Spondylitis
Vertebral body lysis results in pathologic vertebral
body collapse, coupled with disc destruction and
inability to visualize discs
Tubercular Spondylitis
Angular kyphotic deformity aka
Gibbus Deformity
Gibbus Deformity may cause ____ vertebra
tall
tubercular arthritis shoes early
joint widening due to effusion
- Early joint widening due to effusion
- Subchondral bone destruction
- Articular cartilage destruction
- joint space
narrowing - periarticular osteoporosis
Tubercular Arthritis:
End stage tubercular spondylitis is
fibrous ankylosis of joint
Bony ankylosis and periosteal reaction is common in
pyogenic infection
Management of skeletal TB includes
debridement and arthrodesis
Diffuse soft tissue swelling, bone expansion, and thinning of cortex
spina ventosa in Tuberculous Dactylitis
