Fx management and healing (Lewis)

Question 1

Primary goal of fracture management

Answer 1

• Early and complete return to function

Question 2

Reduction

Answer 2

• reapposing the fracture fragments and/or segments
• describes precision of apposition of fracture segments/fragments
  
  • anatomic
  • near anatomic
  • non-anatomic

Question 3

Anatomic reconstruction of comminuted fractures

Answer 3

• rigid fixation promotes weight-bearing and fracture healing
• anatomic reduction allows load sharing between bone and implats
• assure anatomic alignment

Question 4

Biological fixation

Answer 4

• Preserve local fracture environment
  
  • vascular supply
• Bridging osteosynthesis
  
  • external skeletal fixation, plates or intramedullary fixation
• Approaches
  
  • closed
  • limited reductions

Question 5

Carpenter vs. Gardener

Answer 5

• Trend over past decade to move away from anatomic reconstruction towards biologic approach for fracture management

Question 6

Alignment

Answer 6

• Refers to orientation of joints proximal and distal to fracture
• greater impact on function than reduction
• anatomic reduction not necessary to achieve anatomic or at least functional alignment

Question 7

Fixation / stabilization

Answer 7

• means to maintain fracture segments in position
• Major fracture segments should be maintained in a functional position
• systems utilized in veterinary medicine
  
  • coaptation
  • external skeletal fixation
  • wires
  • intramedullary fixation (nails and pins)
  • Plates and scres

Question 8

Bone healing

Answer 8

• Bone can regenerate without scarring
• Healing = union
• remodeling
  
  • dependant on mechanical environment
  • haversion systems laid down along lines of stress

Question 9

Fracture healing

Answer 9

• Primary
• Secondary

Question 10

Secondary bone healing

Answer 10

1. inflammatory phase
2. reparative phase
3. remodeling phase
4. strength dependent on callus formation
   
   • extraperiosteal callous-early
   • endosteal callous-after

*blood supply goes from inside out

Question 11

Steps of secondary bone healing

Answer 11

1. hematoa
2. granulation tissue
3. connective tissue
4. cancellous bone
5. bone
6. haversian remodeling

Question 12

Primary bone healing

Answer 12

• Requires anatomic reduction and rigid fixation
• Contact healing
  
  • direct apposition
• Gap healing
  
  • gaps < 1mm
• Associated with minimal callus formation

*only with screws and plates ush

Question 13

Two types of primary bone healing

Answer 13

• Gap Healing
  
  • woven bone laid down without the endochondral ossification step
• Contact Healing
  
  • osteoclast (Multinucleated giant cell) cuts across fx line
  • osteoblasts come behind and lay down a new haversian system

*will probs always have some callous formation from tearing periosteum

Question 14

Every form of fixation used….

Answer 14

• want to distribute forces away from fx line
  
  • distribute load

Question 15

Which type of bone healing is stable quicker?

Answer 15

secondary

-cause of huge callous

Question 16

Radiographic interpretation of fx healing

Answer 16

• Dependant upon
  
  • age of animal
  • fracture type/location
    
    • metaphyseal fx heals quicker (b/c of cancellous bone?!)
• callus should be evident in 2-4 weeks
  
  • periosteal disruption results in some callus
• Fracture lines may initially widen
• Fracture segments and fragments remodel
• Sequential events are very important
  
  • long zones of transition not generally good
• Character and amount of callous is important
• Radiographic appearance lags behind clinical status

Question 17

Bone Grafting

Answer 17

• transfer of bone from one site/source to antother
  
  • facilitate and promote bone healing (osseous union)
• Arthrodeses
• uses cancellous bone
  
  • lots of osteoblasts
• Dogs harvest from
  
  • greater tubercle of humerus

Question 18

Bone grafting

Indications

Answer 18

• Enhance union
  
  • acute fx
  • nonunion fx
  • delayed union fx
• Replace areas of bone loss
  
  • neoplasia
  • infection
  • trauma
  • cysts
• Stimulate fusion of arthrodeses

Question 19

Types of graft

Answer 19

• Immunologic type
  
  • autografts
  • allografts
  • xenografts
• Histologic type
  
  • cancellous
  • cortical
  • corticocancellous

Question 20

Function of bone graft

Answer 20

1. osteogenesis
   
   • osteoblasts
2. osteoinduction
   
   • BMPs (cytokines)
   • induce pleuropotential mesencymal cells to differentiate into osteoblasts
3. osteoconduction
   
   • trabeculae act as scaffolds
   • promotes union
4. structural support (only cortical grafts)

*first three cancellous graft

*NO SALINE, osteoblasts can’t swim! :-D

Question 21

Osteogenesis

Test question

Answer 21

• Direct new bone formation
  
  • osteoblasts
  • osteoprogenitors
• Fresh autogenous graft
• Viable transfer of osteoblasts
  
  • 10-50% survival

Question 22

Cancellous bone grafting

sites

Answer 22

• Greater tubercle
• Iliac crest
• Proximal tibia

*store in sterile container to prevent contamination and desiccation

Question 23

Osteoinduction

Test question

Answer 23

• Recruitment & differentiation of osteoprogenitor cells
• Induces bone synthesis
• Bone morphogenic proteins (BMPs)

Question 24

Osteoconduction

Test question

Answer 24

• Graft provides scaffold for in-growth of capillaries and mesenchymal cells
• Graft eventually resorbed and replaced

Question 25

Structureal support

Answer 25

• Only provided acutely by cortical (allo) grafts
• Slow and progressive
  
  • never complete remodeling
• creeping substitution of the graft