Bone growth and fracture healing

Question 1

what actions does cortical and cancellous bone resist?

Answer 1

cortical: bending and torsion
cancellous: compression

Question 2

what type of bone makes up the diaphysis and metaphysis?

Answer 2

diaphysis = cortical 
metaphysis = cancellous

Question 3

what causes a bone to fracture?

Answer 3

high energy in normal bone i.e. trauma
repetitive stress in a normal bone i.e. stress fracture
low energy transfer in an abnormal bone i.e. osteoporosis, osteomalacia, metastatic tumour etc

Question 4

what are the 4 stages of fracture repair?

Answer 4

inflammation - haematoma and fibrin clot

soft callus - bridges break in bone with cartilage or fibrous tissue

hard callus - conversion of cartilage to woven bone

bone remodelling - woven bone to lamellar bone

Question 5

what is secondary bone healing?

Answer 5

formation of hard callus from the stages of healing when cartilage/fibrous tissue is converted to bone via membranous and/or endochondral ossification

Question 6

what is delayed union?

Answer 6

failure to heal in expected time

Question 7

what factors can cause delayed union / failure of healing in expected time?

Answer 7

NSAIDS
steroids
warfarin
smoking
ciproflaxacin 
high energy injury
distraction
instability 
infection
immune suppressants 
diabetics

Question 8

what is non union?

Answer 8

failure to heal

Question 9

what are the causes of non union of a fracture?

Answer 9

failure of ossification of cartilage 
instability (abundant osteoclasts)
abundant callus formation 
persistent fracture line
sclerosis