conditions and diseases Flashcards
AVN pathophysiology
Interrupted subchondral microcirculation (due to injured vessels, intravascular
coagulation or external compression) > bone ischemia and eventual necrosis (wedgeshaped infarct with the apex pointing to the bone center) subchondral
microfractures and collapse pain, loss of joint function and long-term damage.
what bones affected by AVN the most? 5
epiphysis most common: femoral head, humeral head. femoral condyles
scaphoid and talus cuz they are covered with cartilage and have single terminal blood supply
causes of AVN 3
- intravascular occlusion: coagulopathy
- vascular interruption: trauma
- intraosseous extravascular compression: alcohol/malignancy/gaucher disease
how do alcohol/corticosteroids cause AVN
both increase fat content in
the bone marrow exerting
pressure on the vessels that
pass through it and can
possibly result in fat emboli
AVN example causes (ASEPTIC)
Alcohol
SLE/sickle cell (coagulopathy)
Exogenous/endogenous steroids
Pancreatitis/pregnancy
Trauma
Infection/idiopathic
hyperCoagulopathy
alcohol consumer or steroid user with groin pain?
AVN until proven otherwise
AVN exam findings
pain with WB
limited ROM
antalgic gait
AVN gold standard diagnosis
MRI
MRI findings AVN 2
- decreased signal intensity indicative of marrow oedema (early finding)
- double line sign: outer hypointense line T1 indicating bone ischaemia
inner hyperintense line T2 indicating hypervascular granulation tissue (diagnostic of AVN)
AVN classification
Ficat or Steinberg
Stage Radiographic (x-ray) findings MRI and bone scan findings
0 (preclinical &
preradiographic -
silent hip)
Normal Normal
I Normal Abnormal MRI and/or bone scan
II Cystic/sclerotic changes Abnormal MRI and/or bone scan
III Crescent sign (subchondral microfx
and collapse) Abnormal MRI and/or bone scan
IV Femoral head flattening/collapse Abnormal MRI and/or bone scan
V Joint space narrowing Abnormal MRI and/or bone scan
VI Advanced degenerative changes Abnormal MRI and/or bone scan
AVN tx
consevative for stage 1/2:
NSAIDs, bisphosphonates, mnagement of underlying conditions
surgical: core decompression:
helps relieve intraosseous pressure enhancing revascularisation
bone grafting can be added to core decompression:
ex: free vascularised fibular graft: sutured to retinacular vessels (good for young pts)
THR for stage 3 and above
osteomyelitis common locations 3
vertebrae (lumbar
metaphysis of long bones
pelvis
why is osteomyelitis common in metaphysis
rich vascularity and sluggish blood flow
osteomyelitis risk factors
▪ Recent trauma or surgery or presence of foreign body.
▪ Comorbidities: diabetes mellitus, sickle cell disease, immuncompromsied (HIV).
▪ Vascular insufficiency.
▪ IV drug use.
osteomyelitis classification
anatomic: cierny and mader classification
timeline:
acute: <2 weeks
subacute: 2-6 wks
chronic: >6 wks
routes of pathogenesis of osteomyelitis 3
- hematogenous spread (children) (vertebrae in adults)
- direct inoculation (trauma)
- contiguous spread (from nearby infected tissue like septic joint or diabetic ulcer)
osteomyelitis organisms SSGGP
- staph aureus: most common
- salmonella: sickle cell pathognomic
- gram negative bacilli (e.coli, kleibsella) neonates, IV drug users
- group B strep: infants
- psuedomonas: IV drug users
define sequestreum
It is a devascularized floating piece of bone with
surrounding necrosis and resorption. Due to its avascularity, it cannot be reached
by antibiotics and hence, acts as a reservoir for infection.
define involucrum
It is a thick sheath of new periosteal bone encasing a
sequestrum.
osteomyelitis investigations
cbc, ESR/CRP, blood cultures, wound cultures
osteomyelitis xray findings 4
xray:
- codman triangle: periosteal thickening
- brodies abscess: lytic lesion with surrounding sclerosis
- sequestreum/involucrum presence
- cloaca: cortical defects that drain pus into adjacent tissue
osteomyelitis gold standard
MRI
T2 sequence shows a central hyperintense lesion (intraosseous/Brodie’s abscess)
with surrounding more diffuse hyperinsensity (indicative of bone marrow
edema) - T1 sequence shows these two findings as hypointense signals
osteomyelitis blood culture negative but clinical suspicion high?
open bone biopsy/needle aspiration with gram stain, culture, histology (gold standard)
osteomyelitis tx:
supportive
nonoperative
supportive:
- IV fluids and analgesics
nonoperative:
- bone biopsy/blood samples/ labs
- empiric iv abx based on gram stain
- switch to specific abx once culture and sensitivity is out
- continue abx for 4-6 wks
osteomyelitis operative indications? 3
- failure to improve to abx in 24-48 hrs
- evidence of abscess
- chronic OM
osteomyelitis operative steps?
- abscess drainage
- debridement of necrotic tissue
- management of dead space left behind with abx beads/vascularised bone graft/vacuum assisted closure
- soft tissue coverage
- stabilisation with ex fix
- IV abx
