Flashcards in Avascular necrosis Deck (17)
Which sites are most susceptible to avascular necrosis?
Head of humerus
Proximal poles of scaphoid and talus
Describe how ischaemia can occur in avascular necrosis
Severance of local blood supply
Venous stasis and retrograde arteriolar stoppage
Compression of capillaries and vascular sinusoids by marrow swelling
List the common causes of traumatic osteonecrosis
Fracture and dislocation of hip: retinacular arteries supplying femoral head +/- ligamentum teres
Fractures of scaphoid or talus
Impact injuries and osteoarticular fractures of any convex articular surfaces ➔ osteochondrosis (small segments of osteonecrosis)
Name 5 causes of non-traumatic osteonecrosis
Define Perthe's disease
Childhood avascular necrosis of hip ➔ collapse and flattening of the femoral head
Describe the clinical features of osteonecrosis
Patients tend to present when lesion is advanced.
Usual complaint is pain: near joint with stiffness
Local tenderness and nearby joint swelling
What x-ray changes are seen with osteonecrosis?
Subarticular segment of increased bone density*: due to reactive new bone formation
Fracturing and collapse of necrotic segment
Normal joint space*: differentiates from OA
How is osteonecrosis investigated?
MRI scan shows early signs
X-ray changes tend to occur after several months
Outline the staging of osteonecrosis of hip
ARCO staging of osteonecrosis
0. Biopsy shows osteonecrosis. Asymptomatic with normal clinical investigations
1. X-ray normal, MRI shows osteonecrosis
2. X-ray and/or MRI show necrosis, but no distortion of bone shape or fracture
3. X-ray shows early abnormality, but femoral head still spherical
4. Signs of flattening or collapse of femoral head
5. As above + loss of joint space
6. As above + destruction of articular surface
What is crescent sign of avascular necrosis?
Subchondral lucency of femoral head: indicates imminent articular collapse
How is osteonecrosis treated?
Treat any underlying causes where possible
Stage 1 and 2: weight relief, splint, surgical decompression (if venous stasis or marrow oedema)
Stage 3: realignment osteotomy: transfers stress to an undamaged area
Stage 4-6: treatment similar to OA
What is the treatment for stage 4-6 osteonecrosis?
Treatment similar to OA
Education, advice, assisted devices, strengthening exercises, weight loss
Paracetomal and/or topical NSAIDs (knee/hand)
Intra-articular corticosteroids: temporary
Codeine: last resort
Arthroplasty: shoulder, hip, knee
Arthrodesis (fusion): ankle, wrist
Define sickle-cell disease
An autosomal recessive disorder affecting red blood cells, which predominantly affects African or Afro-Caribbean ethnicity). Characteristically features HbS which becomes distorted and sickle-shaped (esp in hypoxia).
This can result in anaemia and sickle cell crisis (vaso-occlusion).
Which organism commonly causes acute osteomyelitis in patients with sickle-cell disease?
Define Caisson disease (Decompression sickness)
Rapid decompression of blood and tissues supersaturated with nitrogen causes release of gas bubbles. This causes local tissue damage and generalised embolic phenomena.
Symptoms: pain near joints (the bends), breathing difficulties, vertigo
Define Gaucher's disease
Autosomal recessive disorder of enzyme deficiency resulting in abnormal accumulation of the lipid glucocerebroside. Effects mainly seen in liver, spleen, and bone marrow.
Accumulation causes increased medullary cell volume and capillary compression ➔ bone complications including osteonecrosis.