125. Bone and Joint Infections Flashcards
Acute vs subacute infection - timeline?
acute within 2 weeks of onset
subacute 1-several months
Compact bone
compact - shaft of long bone and covers epiphysis
- dense, without cavities, longitudinaly running Haversian systems (house vasculature and nerves)
Trabecular/spongy bone
trabecular - within epiphysis and makes up irregular bone
- bony lattice, traveculae, which located within medullary cavity and contains marrow, more metabolically active
-central Haversian canals in spongy bone parallel to long axis of bone - bloody supply and reticular ct for haversian system
Diaphysis
shaft of bone
compact cortical bone overlying periosteum and medullary canal containing marrow
Metaphysis
junctional region epi and diaphysis
trabecular bone and cortical thins here
Epiphysis
area at either end of a long bone and made of abundant trabecular bone
thin shell cortical bone
Cartilage in a mature adult on the epiphysis of bone - what does this allow?
frictionless movment
Joints - synovial capsule mechanism?
structural integrity
sleeve to attach to articulating bones
Osteomyelitis: ?
infection of bone and medullay cavity
Osteomyelitis: RF for infection?
trauma
distruption of blood flow
large inoculum of bloodborn or external microorganisms
FB
Osteomyelitis: why does infection start at metaphysis
area of turbulent blood flow
Osteomyelitis: why is surgery typically needed?
inflammatory cell migration to the area to help causes edema, vascular congestion and small vessel thrombosis so that IO pressure increases to compromise flow to bone - as such medication hard to get here
Involucrum
new bony tissue growth at area of infection to compensate for tensile stress from lack of blood supply
Why do neonates and infant more often get septic arthritis from OM?
readily advances through joint space
Adult progression of OM to joint space?
post epi plate fusion –> anastomoses between metaphyseal and epiphyseal blood vessel fro infection to spteady to epi, then synovium and joint space
Gram stain can be negative in OM - how?
only picks planktonic/bacteria in a single state (typically those least R) - therefore often times biofilm other stages are still virulent
Definitive diagnosis of OM?
can only be done by culture of synovial fluid aspirate or synovial tissue
Source of spread of bacteria in children’s OM and adult vertebral OM?
hematogenous
Source of spread of bacteria in appenduclar skeleton adult (foot, hand, skul, maxilla, mandible) OM?
contigious source infection
direct implantation (bite, open fracture, surgical instrumentation)
Head and neck OM source of spread?
sinus disease
odontogenic infection
Usual source of spread of septic arthritis?
hematogenous unless direct source into joint
Typical microbiology of septic arthritis: kids
staph aureus > strep > gram neg, neisseria > H influ
Typical microbiology of septic arthritis: young adult
neisseria > staph > strep, gram neg and h influ rare
Typical microbiology of septic arthritis: adult
staph > strep > gram neg > gonorrhea > h influ
Typical microbiology of septic arthritis: older adults
staph > gram neg > strep > rare h influ, gonorrhea
In what pt pop does pseudmonas need to be strongly considered as a source of septic arthritis?
puncture wounds
post surgical
sickle cell anemia
Underlying disease RF for bone-joint infection risk
diabetes
chronic steroid
IVDU
preexisting joint disease (RA)
other immunosuppressed states
Empiric abx for neonate to <3mo with OM
cephalosporin third gen
Penicillinase R pen like amox clav or vanco (if MRSA) +gent
Empiric abx for neonate to <3mo with Septic arthritis
amox clav + ceftriaxone
or amox clav and gent
if MRSA + switch amox clav for vanco
Common organisms OM and septic arthritis for neonates and children <3mo
S aureus
gbs
enterbacteriaceae
Common organisms 3mo- 14y OM
staph aureus
gas
h influ
Common organisms 3mo- 14y septic arthritis
s aureus
strep spp
enterbacteriacease
Tx 3mo-14mo om:
ceftriaxone + amox clav/septra
or vanco and ceftri, chloramphenicol
amox clav or ceftr with allergy pen or clinca with allergy to pen + ceftr
Tx 3mo-14mo septic arhtritis
amox clav/septra and ceftriaxone
Tx 14y- adult: what bug for OM?
s aureus
Tx 14y- adult: septic arthritis
s aureus
strep
enterbacteriaceae
Tx 14y- adult: OM
septra or amox clav
alt vanco
Tx 14y- adult: septic arthritis
amox clav/septra or ceftr
alt: vanco and cetr or penicillin and gent or ceftr
Infection subsets: septic arthritis in a yung sexually active adult or adult with acute arhthrits concern for gonorrhea - tx?
ceftriaxone
or spectinomicin or penicillin if sn
Infection subsets: OM in chronic OM and db foot infrection tx:
amox clav or septra + flq + metronidazole
or amoxclav/septra + ceftr + clinda
Infection subsets: OM in infected prosthesis - bugs?
staoh aureus
staph epidermidis
pseudmonoas
Infection subsets: OM in infected prosthesis - tx?
vanco + flq
alt: imipenem
Infection subsets: septic arthris in infected prosthesis - bugs?
staph aureus
s epidermidis
pseudomonas (same as OM)
Infection subsets: septic arthris in infected prosthesis - tx
vanco + flx
or amox/clav/septra and gentamicin
Infection subsets: OM/septic arhtritis n IVDU - bugs?
staph aureus
pseudomonas
enterobactericease
Infection subsets: OM/septic arhtritis n IVDU - tx?
3rd gen cephaosporin and aminoglycoside
or 3rd gen alone
for septic arth: amox calv/septra and gent or flq
or vanco and flq
Infection subsets: plantar puncture wound OM/septic arthritis - bug?
pseudomonas
Infection subsets: plantar puncture wound OM/septic arthritis - tx?
ceftrazidie/cefepime
or flq
Infection subsets: human or animal bite OM/septic arthritis risk- bugs?
eikenella corrodons
pasteurella multicoda
Infection subsets: human or animal bite OM/septic arthritis risk- tx?
pencillin +/- cefepime or ceftazidine
or 3rd gen cephalosporin and septra
MC forms TB for bone and joint infections?
- Potts - vertebral OM
- Tubercular arthritis - like low grade RA
HIV: what bug is particularly characteristic of OM?
bacillary angiomatosis
gram negative rikettsia like organism causing ostelytic bone lesions
Sx OM:
fever
rigor
toxi possible
Key sx in children OM?
limp, or cannot weight bear
Predominant PE finding of septic arthritis
point tenderness over infected segment
Complications of acute OM
bacteremia
sepsis
septic arhtritis
brain abscess
meningitis
spinal cord compression
pneumonia
empyemea
children.= issues of growth
OM in children: where is usual site of infection?
distal metaphysis due to increased vascularity
OM in children: sx
fever
chills vomit
dehydration
malaise
not usually toxic
point tender
limp or cannot weight bear
OM in children: what 2 things are sign for dx?
blood culture (hematogenous spread)
PE
OM in children: subacute osteomyeltitis - what might this look like?
s+sx slow to appear
radiographs show small areas of OM in metaphysis
cultures often negative
OM in children: chronic recurrent multifocal OM - what might this look like?
small foci of infection
defined by mult episodes of indolent infection
culture often negative, xr help
Vertebral OM: RF
IV access devices
indwelling lines
asx uti
yo - IVDU
Vertebral OM: why is spine so susceptible?
two way blood flow
transverse and longitudal anastomoses
Vertebral OM: MC areas?
lumar
thoracic
cervical
Vertebral OM: mc sx?
back pain
insiduous onset
tenderness over sp
Vertebral OM: Neuro deficits common?
only 40%
moreso if + epidural abscess
Vertebral OM: helpful labs?
esr
crp
blood culture also useful
Vertebral OM: tx
imaging
start abx empirically
early orth/spine involvement
Best imaging test for Vertebral OM:
MRI
ct good for bone descrution
Cervical OM can cause what ENT disease?
retropharyngeal abscess
Vertebral OM: L spine OM can be complicated with which other ortho disease?
psoas m abscess
Vertebral OM: vascular complications (3)
sc ischemia
septic thrombosis
compresion of local bl vessels
Vertebral OM: thoracic complications - 3
empyema
reactive pleural effusion
paraspinal abscess
Vertebral OM: most dreaded complication?
infection into spinal canal
epidural abscess
then causing SCI
paralysis
Vertebral OM: RF for paralysis from SC progression?
oa
cervical spine OM
RA/diabetes
Vertebral OM: when does surgery need to be considered in addition to IV abx?
- scc
- abscess drainage or debridement
- correction of progressive anatomic deformity
- if infection recurs after adequate tx
Diskitis: what is this?
varient of vertebral OM: disk is avascular and gets nutrition from nearby blood vessels, so possible for bacteria o flourish here
Isolated diskitis is mc in what population?
children
when to use MRI vs CT for diskitis?
anatomy of diskitis
ct - guide aspiration
diskitis typical tx op or non?
non op
What kinds of injuries/general categories can cause posttraumatic OM?
open fracture
burn
bite
puncture wound
surgery and invasive procedure
When to prosthetic joint OM from surgery typically display themselves? (weeks)
12
typically not better with pain post surgery
What is the treatment choice for infection following TKA?
I+D
prosthetic rentesion
following total knee arthroplasty
Dx of prosthetic joint infection
join aspiration
synovial fluid analysis
bone bx
difficult for imaging given metal
Why do people with diabetes get more OM?
compromised vascularity
polyneuropathy
hyperglycemia impairs healing
( allows bacteria to proliferate, impaired wbc function, defective chemotaxis, abn phagocytosis, decr bactericidal function, defect abody synthesis, decr completement )
Radioraphic features of diabeticOM
osteopenia
periosteal thickening
cortical erosions
new bone formation
mottled lytic lesions
Mainstay of diabetic OM tx?
amp
also can try 10 week abx tx *IV then oral in select pt
Why are sickle cell disease pt at risk OM?
asplenia
Sickle cell OM: where on bone does it effect?
diaphysis
Sickle cell OM: mc organism?
salmonella
Sickle cell OM: bone infarction vs OM - ways to consider oM more likely?
fever
toxic appearance
elevate esr
mri
response to conversative therapyY; bone infarct better after 24-48h whereas bone infection worsens
Chronic OM: clinical signs this has become chronic?
formation of sequestra
presence of draining tracts of fistula
chronic OM dx: only reliable is…
direct bone bx
DDX OM
osteoid osteomas, chondoblastoma, metastases, lymphoma
Ewing sarcuma
occult fracture
For diabetes, what level of ESR (“greater than ?”) incr likelihood of underlying bone infection
70
CRP and ESR - which is better for early onset disease vs following resolution
crp - early
Early OM on xray - findings?
lucent lytic areas of cortical bone descrution (often takes 2 weeks though so can miss if early)
3-5d:
soft tissue edema
distorted fascial planes
altered fat
Children xray OM findings?
periosteal reaction - hypertrophy or elevation of periosteum and presence of involucrum
More advanced disease OM findings on xray?
lytic lesion surrounding dense sclerotic bone
possible sequestra
When should CT be used for ID OM?
when MRI CI/unavailable
for assessing involucrum, sequestrum
better view than plain of sternum, vertebrae, pelvis bones, calcaneus
Why is a swab not reliable/acceptable for dx of OM?
bugs may be different than those effecting bone
OM Dx *A few key points should be considered with use of this algorithm:
* Radiographs lag behind the clinical picture.
* In infants and children, the amount of radiation exposure with imaging techniques must be considered.
* If the clinical presentation strongly suggests osteomyelitis, a lengthy diagnostic evaluation should not delay empirical treatment. Culture specimens of blood, urine, and other appropriate sites should be obtained and antibiotic treatment started.
* Early osteomyelitis is best identified on MRI with contrast. Other imaging modalities are useful later in the disease course and play an important role, especially when MRI is unavailable or contraindi- cated, and in concert with other clinical and laboratory findings.
-
What cases of OM are feasible for medical management?
asymptomatic OM for pt with fever, w loss or bacteria, hematongeous infection/vertebral OM caused by sn bacteria
Penicillin is reserved for bone contaminated with soil to cover which bug?
corynebacteruim - can cause gas gangrene
Penicillin and gentamicin are reserved for bone infections contaminated with what?
feces
Septic arthritis: 3 main ways of spread
- contigious focus of infection
- direct inoculation from trauma
- iatrogenically after joint aspiration/injection
MC organism septic arthritis?
staph aureus
Waldvogel classification for OM
hematogenous
contiguous - vascular insuff or none
chronic