Pathology: Osteochondritis and Avascular Necrosis

Question 1

what is the most common site of AVN in chronic alcoholics

Answer 1

femoral head

Question 2

how does chronic alcoholism cause AVN in the femoral head

Answer 2

• alcohol inc the NADH to NAD ratio
• this inc in NADH results in alteration of fat metabolism which can result in mobilisation of fat into the circulation which slugs up the capillary system and promotes coagulation within prone areas of bone
• • inc fat content of marrow can compress venous outflow casuing stasis and ischaemia
    *

Question 3

why does AVN occur in other areas

Answer 3

death of tissue due to disruption to blood supply

Question 4

name some susceptible locations to AVN

Answer 4

• scaphoid bone in the wrist due to retrograde blood supply
  
  • fractures of scaphoid after a fall on outstretched hand are often missed and can result in AVN
• intracapsular hip fracture
• talar fracture

Question 5

what is dead bone seen as microscopically

Answer 5

trabeculae without osteocytes in the lacuna

Question 6

creeping substitution

Answer 6

almost pathognomic of AVN attempt to repair dead bone where it is slowly encircled by new viable bone and eventually replaced

Question 7

osteochondritis

Answer 7

• also called osteochondroses
• group of disorders that are characterised by abnormal endochondral ossification of epiphyseal growth during childhood
• pain and swelling after exercise
• intermittent swelling and locking

Question 8

pathology of osteochondritis

Answer 8

impact or traction causes bleeding and oedema in the bone resulting in capillary compression

bone necrosis ensues resulting in compression, fragmentation or separation of bone (and over lying cartilage if intra articular)

this may cause flattening and incongruence of a joint or pothole on the surface

Question 9

freiburgs disease - osteochondritis

Answer 9

2nd metatarsal head affected by compression

Question 10

what can osteochondritis progress to if a joint is invovled

Answer 10

pain and arthritis

Question 11

kohlers disease

Answer 11

navicualr bone affected by osteochondritis

Question 12

Kienbock’s disease

Answer 12

lunate affected by osteochondritis

Question 13

panners disease

Answer 13

capitulum of elbow affected by osteochondritis

Question 14

scheuermanns disease

Answer 14

vertebral compression causes osteochondritis - normal ossification affected

Question 15

apophysis

Answer 15

bony tubercule where tendon attached

Question 16

osgood schlatter

Answer 16

tibial tuberosity apophysis

repeated traction is thought to cause inflammation and chronic avulsion of the 2y ossification centre of the tibial tuberosity

Question 17

severs disease

Answer 17

calcaneal apophysitis is an inflammation of the growth plate in the heel of growing children, typically adolescents.

The condition presents as pain in the heel and is caused by repetitive stress to the heel and is thus particularly common in active children.

Question 18

osteochondritis dissecans

Answer 18

fragmentation wtih separation of bone and cartilage

Question 19

name some sites that are predisposed to osteochondritis dissecans

Answer 19

lateral part of medial femoral condyle in the knee

anteromedial talar dome

superomedial femoral head

humeral capitulum

Question 20

what is the benefit of surgical realigment (osteotomy)if a joint is damaged from osteochondritis

Answer 20

shift the load in a joint froma damaged area to an undamaged area

Question 21

treatment of osteochondritis dissecans

Answer 21

pinning of unstable fragments or removal of detached fragments

Question 22

AVN

Answer 22

ischaemic necrosis of the bone predominantly in adults

Question 23

what can AVN be cause by

Answer 23

secondary to fractures that disrupt the blood supply

alocholism and steroid abuse

Question 24

how does primary hyperlipidaemia result in AVN

Answer 24

same as alcoholism

inc NADH - alters fat metabolism, inc fat content of bone marrow causes compression of venous outflow and stasis and ischaemia

Question 25

name some other caues of AVN

Answer 25

thrombophilia, sickle cell disease, and antiphospolipid deficiency

• inc coagulability

Question 26

what is a rare cause of AVN

Answer 26

caissons disease (decompression sickness) which causes AVN from N2 gas bubbles forming in the circulation

Question 27

what occurs secondary to AVN

Answer 27

OA

Question 28

what does AVN do to bone

Answer 28

necrosis of a segmnet resulting in patchy sclerosis and then subchondral collapse and irregularity of articular surface

Question 29

treatment of AVN if articular surface hasnt collapsed

Answer 29

drilling can be performed under fluouroscopy to decompress the bone, prevent further necrosis and help healing

Question 30

treatment of AVN if articular surface has collapsed

Answer 30

joint replacement