6: Delayed Union/Nonunion - Drown

Question 1

3 main blood supplies to adult long bone

Answer 1

• principal nutrient a (penetrates cortex direct to medullary canal, main supply to diaphysis)
• metaphyseal-epiphyseal a (penetrate corteca t both metaphyssi, anastomose with medullary aa)
• periosteal a (supply outer 1/4 to 1/3 boen)

Question 2

inflammatory phase of secondary fracture healing

Answer 2

• immediately post injury
• hematoma forms
• mast cells, PMNs, macrophages, lysosomal enzymes present
• pain and swelling occurs to splint area and to immoilize fracture site
• 3-4 d

Question 3

proliferative phase of secondary fracture healing

Answer 3

• fibrin scaffold provided durign inflammatory phase replaced with emsenchymal cells producing granulation tissue
• callus begins as islands of cartilage and osteoid in granulation tissue
• 7-10 d chondrocytes produce matrix spanning fx site allowing stabilization
• cartilage replaced by bone during enchondral ossification

Question 4

remodeling phase of secondary fracture healing

Answer 4

• after fx bridged

- osteoclastic resorption of woven bone and replaced with lamellar bone

Question 5

why phase is skipped with primary bone healing?

Answer 5

fibrocartilagnious callus phase
- heals through haversian remodeling and cutting cones (leading tips of osteoclasts tha phagocytose osteoid at end of haversian canals)

Question 6

non-anatomical alignment at fracture stie

Answer 6

malunion

ex: angulation, shortening, rotation, translation
tx: none -> surgical itnervention

Question 7

any fx not healed in reasonable period of time

Answer 7

delayed union

Question 8

radiographic findings delayed union

Answer 8

• serial radiographs show unchanged irritation callus, persistance of fracture cleft
• also see persistent edema dn pain

Question 9

tx delayed union

Answer 9

• NWB and immobilization

- electrical bone growth stimulation

Question 10

nonunion = failure to achieve stable fx healing after ____ of tx

Answer 10

8-9 months

Question 11

reasons for non-union

Answer 11

• distraction
• poor reduction
• soft tissue interposition
• infection
• vascular compromise
• excessive motion at fx site

Question 12

3 types of viable non-unions

Answer 12

• hypertrophic “elephant foot”
• slightly hypertrophic “horses foot”
• oligotrophic (no callus formation, bone scan says vascular bone ends)

Question 13

contraindications electrical bone stimulation

Answer 13

• gap greater than 1/2 diameter of bone involved
• pseudoarthritis
• isolated malunion
• isolated usage in pathological fx due to tumor or infection

Question 14

4 types non-viable nonunion

Answer 14

• dystrophic (torsional wedge - only one side good)
• necrotic (comminuted fracture)
• defect (gap present)
• atrophic (end result)

all considered avascular

Question 15

indications for bone grafting

Answer 15

• delayed union
• non-union
• pseudo arthroses
• osseous defect left after taruma, infection, tumor
• arthrodesis of jts
• congenital defect

Question 16

osteogenesis v osteoconduction v osteoinduction of bone grafts

Answer 16

• formation of new bone by living cells in autografts
• structural framework
• ability to transfrom pluripotent stem cells in recipient bed into osteoblasts

Question 17

coil applied over fracture site

Answer 17

inductive coupling and combined magnetic field EBGS

Question 18

two electrode discs applied on oppostie sides of fx site

Answer 18

capacitive coupling

Question 19

autograft
isograft
allograft/homograft
xenogragt

Answer 19

• you
• identical twin
• donor
• other species