conditions and diseases

Question 1

AVN pathophysiology

Answer 1

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.

Question 2

what bones affected by AVN the most? 5

Answer 2

epiphysis most common: femoral head, humeral head. femoral condyles

scaphoid and talus cuz they are covered with cartilage and have single terminal blood supply

Question 3

causes of AVN 3

Answer 3

1. intravascular occlusion: coagulopathy
2. vascular interruption: trauma
3. intraosseous extravascular compression: alcohol/malignancy/gaucher disease

Question 4

how do alcohol/corticosteroids cause AVN

Answer 4

both increase fat content in
the bone marrow exerting
pressure on the vessels that
pass through it and can
possibly result in fat emboli

Question 5

AVN example causes (ASEPTIC)

Answer 5

Alcohol
SLE/sickle cell (coagulopathy)
Exogenous/endogenous steroids
Pancreatitis/pregnancy
Trauma
Infection/idiopathic
hyperCoagulopathy

Question 6

alcohol consumer or steroid user with groin pain?

Answer 6

AVN until proven otherwise

Question 7

AVN exam findings

Answer 7

pain with WB
limited ROM
antalgic gait

Question 8

AVN gold standard diagnosis

Answer 8

MRI

Question 9

MRI findings AVN 2

Answer 9

1. decreased signal intensity indicative of marrow oedema (early finding)
2. double line sign: outer hypointense line T1 indicating bone ischaemia
   inner hyperintense line T2 indicating hypervascular granulation tissue (diagnostic of AVN)

Question 10

AVN classification

Answer 10

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

Question 11

AVN tx

Answer 11

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

Question 12

osteomyelitis common locations 3

Answer 12

vertebrae (lumbar
metaphysis of long bones
pelvis

Question 13

why is osteomyelitis common in metaphysis

Answer 13

rich vascularity and sluggish blood flow

Question 14

osteomyelitis risk factors

Answer 14

▪ Recent trauma or surgery or presence of foreign body.
▪ Comorbidities: diabetes mellitus, sickle cell disease, immuncompromsied (HIV).
▪ Vascular insufficiency.
▪ IV drug use.

Question 15

osteomyelitis classification

Answer 15

anatomic: cierny and mader classification
timeline:
acute: <2 weeks
subacute: 2-6 wks
chronic: >6 wks

Question 16

routes of pathogenesis of osteomyelitis 3

Answer 16

1. hematogenous spread (children) (vertebrae in adults)
2. direct inoculation (trauma)
3. contiguous spread (from nearby infected tissue like septic joint or diabetic ulcer)

Question 17

osteomyelitis organisms SSGGP

Answer 17

1. staph aureus: most common
2. salmonella: sickle cell pathognomic
3. gram negative bacilli (e.coli, kleibsella) neonates, IV drug users
4. group B strep: infants
5. psuedomonas: IV drug users

Question 18

define sequestreum

Answer 18

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.

Question 19

define involucrum

Answer 19

It is a thick sheath of new periosteal bone encasing a
sequestrum.

Question 20

osteomyelitis investigations

Answer 20

cbc, ESR/CRP, blood cultures, wound cultures

Question 21

osteomyelitis xray findings 4

Answer 21

xray:
- codman triangle: periosteal thickening
- brodies abscess: lytic lesion with surrounding sclerosis
- sequestreum/involucrum presence
- cloaca: cortical defects that drain pus into adjacent tissue

Question 22

osteomyelitis gold standard

Answer 22

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

Question 23

osteomyelitis blood culture negative but clinical suspicion high?

Answer 23

open bone biopsy/needle aspiration with gram stain, culture, histology (gold standard)

Question 24

osteomyelitis tx:
supportive
nonoperative

Answer 24

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

Question 25

osteomyelitis operative indications? 3

Answer 25

• failure to improve to abx in 24-48 hrs
• evidence of abscess
• chronic OM

Question 26

osteomyelitis operative steps?

Answer 26

1. abscess drainage
2. debridement of necrotic tissue
3. management of dead space left behind with abx beads/vascularised bone graft/vacuum assisted closure
4. soft tissue coverage
5. stabilisation with ex fix
6. IV abx