Bone Response to Injury Lecture 1

Question 1

woven bone

Answer 1

immature bone

Question 2

woven bone cellularity

Answer 2

hypercellular

Question 3

formation of woven bone

Answer 3

rapid

Question 4

mineralization of woven bone

Answer 4

very radiolucent, poorly mineralized

Question 5

lamellar bone cellularity

Answer 5

low cellularity

Question 6

organization in woven bone versus lamellar bone

Answer 6

woven bone is disorganized and lamellar bone is organized

Question 7

formation of lamellar bone

Answer 7

slow

Question 8

mineralization of lamellar bone

Answer 8

mineralized and radiopaque

Question 9

eventually, woven bone becomes

Answer 9

lamellar bone

Question 10

sites of repair for new bone formation

Answer 10

periosteum (outer fibrous layer and inner cellular layer with mesenchymal cells)

endosteum (interface between marrow and bone)

Question 11

mechanisms of new bone formation

Answer 11

cutting cones (slow)
IO
EO

Question 12

IO

Answer 12

bone formed directly from mesenchymal cells without cartilage template

Question 13

EO

Answer 13

hyaline cartilage template mineralizes, osteoclasts remove chondrocytes, osteoblasts form bone from the cartilage template

Question 14

traumatic fracture

Answer 14

broken by excessive force

Question 15

pathological fracture

Answer 15

abnormal bone broken by minimal trauma or during normal weight bearing forces

Question 16

direct fracture healing

Answer 16

contact healing (surgical fixation), gap healing, rigid fracture stabilization (pins)

Question 17

indirect fracture healing

Answer 17

biomechanical environment dictates which type takes place
limited intervention

Question 18

stages of indirect bone healing

Answer 18

1. Inflammation: hematoma formation (0-7 days)
2. Repair: soft callus (woven: 1-3 weeks), bony callus (lamellar: 3-6 weeks)
3. Bone remodeling

Question 19

first step of fracture healing

Answer 19

1. tearing of the periosteum and displacement of fracture ends
2. hemorrhage with hematoma and clot formation by fibrin polymerization

Question 20

steps of fracture healing after hematoma

Answer 20

3. impaired blood flow leading to necrosis of the bone fragments
4. release of cytokines and growth factors by platelets and macrophages within the clot

Question 21

steps of fracture after cytokines and growth factors are released

Answer 21

5. influx of proliferation of mesenchymal cells and granulation tissue forms (there is a blood supply present) (7-10 days)

Question 22

steps after mesenchymal cells and granulation tissue forms

Answer 22

6. proliferation and differentiation of mesenchymal cells into osteoblasts and woven bone is formed!!!

Question 23

steps after woven bone is formed

Answer 23

7. granulation tissue conversion from soft callus to hard callus

Question 24

composition of bridging callus and timeframe

Answer 24

bridging or primary callus usually takes 1-6 weeks to form and is a mixture of woven bone and cartilage

Question 25

what does the soft callus consist of

Answer 25

woven bone and cartilage with periosteal vessels (radiolucent)

Question 26

why is cartilage present in the soft callus

Answer 26

low oxygen tension will result in hyaline cartilage formation that is radiolucent

Question 27

hard callus composition

Answer 27

forms from EO and is mineralized

Question 28

what does the primary callus provide

Answer 28

provides stability for some degress of limb function until the healing phase is complete

Question 29

what does the primary callus provide

Answer 29

provides stability for some degree of limb function until the healing phase is complete

Question 30

fracture callus remodeling

Answer 30

remodeling the primary callus which will eventually disappear and the woven bone will become strong lamellar bone. once lamellar bone is restored, the shape and strength of the bone will come back

can take months to years!

Question 31

3 complications of fracture healing

Answer 31

excessive motion leading to fibrous non-union

inadequate blood supply leading to necrotic, dead bone

infection by surgery or during time of injury

Question 32

fibrous non-union explain

Answer 32

mesenchymal progenitors become fibroblasts which replaces the bone, and this will not undergo mineralization