Bone injury and fracture healing

Question 1

What is bones response to injury

Answer 1

1) bleeding
2) cellular infiltration (inflammation)
3) cell death (necrosis, apoptosis)
4) cellular proliferation
5) differentiation and replacement of tissue with bone or other tissue

Question 2

what are the goals of fracture fixation

Answer 2

• -early weight bearing and ambulation. (remember benefits to mechanical loading)
• -stable fixation
• -optimization of fracture healing potential
• -preservation of vascularity
• -restoration of anatomy (especially with intraarticular fractures which require anatomic reconstruction)

Question 3

primary bone healing

Answer 3

need stable conditions

two forms: gap and contact healing

Question 4

secondary bone healing

Answer 4

Unstable
Hallmark is callus formation which biologically and mechanically unites fracture fragments
Repair recapitulates endochondral ossification
Potential for stronger repair due to callus

Question 5

delayed union

Answer 5

implies fracture has not healed in a reasonable period of time
NOT always predictive of a non-union

Question 6

Malunion

Answer 6

bones heal in an abnormal manner
either functional or nonfunctional(require treatment)
Intra-articular malunions lead to a risk of secondary degenerative joint disease

Question 7

non-union

Answer 7

the absence of any further reparative response without fracture union
fractures at risk of non-union are radius/ulna esp in toy breeds

Question 8

disadvantages of primary bone healing through use of rigid internal fixation

Answer 8

damage to adjacent muscle/soft tissue impedes fracture healing
removal or periosteum slows healing
excessive interfragmentary motion reduces blood vessel formation

Question 9

Fracture factors affecting healing

Answer 9

1) Geography of fracture–distance between bone fragments and degree of fragmentation
2) Age of fracture and previous healing
3) Mechanical stability at fracture site
4) blood supply

Question 10

Key distinguishing feature between primary and secondary bone healing

Answer 10

presence or absence of a callus

Question 11

Gap Healing

Answer 11

larger gaps with stable bone fragment
intramembranous bone formation with the gap
progressive remodeling osteon formation

Question 12

Contact healing

Answer 12

minimal gaps facilitated by fracture site compression
Absences of callus formation
Cutting cones across the fracture line to initiate osteonal remodeling

Question 13

three phases of secondary bone healing

Answer 13

inflammation, repair, remodeling

Inflammatory stage is the shortest and remodeling stage is the longest.

Question 14

healing under relative instability

Answer 14

a degree of interfragmentary motion can be beneficial to callus formation (principle of dynamization)
however excessive motion predisposes to mal- or non-union

Question 15

Host factors affecting healing

Answer 15

1-Age of patient
2-infection
3-drugs
4-concurrent disease(endocrinopathies)
5-excessive weight
6-excessive or not enough post-operative activity