Bone Healing Objectives

1
Bone Healing Objectives

• Elaina Turner
• August 2nd 2005

2
Bone healing is divided into direct and indirect
healing. What conditions are required for direct
bone healing to occur?

• Occurs with anatomical alignment and absolute
  stability and if a gap is present it must be less
  than 1mm.

3
What conditions will lead to indirect bone
healing?

• Interfragmentary deformation, impaired blood
  supply or fracture gap greater than 1mm.

4
Which type is more common?
5
Is there a difference in strength of bone that
results from the 2 types of bone healing?
6
Indirect bone healing is divided into 4 stages.
Describe the events of each stage. In general
terms, including approximate timing.

• Inflammation
• Begins w/ fx and ends w/ fibrous tissue or
  cartilage formation. Hematoma is formed, becomes
  organized, granulation tissue formation.
• Soft callus
• Begins in 3 to 4 days with the appearance of
  granulation tissue, matures into fibrous tissue
  and firbrocartilage, stabilizes site w/ internal
  and external callus, pain and inflammation end.
• Hard callus
• May last up to 2 mths. Mineralization and
  conversion to bone. Endochondral ossification of
  fibrocartilage forming cancellous bone.
• Remodeling
• May require yrs for completion. Cancellous bone
  is remodeled to longitudinally oriented lamellar
  bone. Contour of bone is restored. Contour is
  less perfectly restored in older animal.

7
Which stage is the longest?

• Remodeling

8
The remodeling stage of bone healing is mediated
by Wolffs Law. What is Wolffs Law?

• Form follows function

9
How is it translated into an effect on the bone?

• Bone is laid down in accordance to stress placed
  upon it.

10
What does this tell you about the relationship
between use of the fractured bone and remodeling?

• Bone that is not used, especially with a fracture
  will experience a delay in healing because of its
  lack of function.

11
Is use of the bone beneficial in other stages of
bone healing?

• Yes it is beneficial in all stages of healing???

12
Direct bone healing is divided into 3 subtypes.
Describe the conditions under which subtype will
occur.

• Contact healing
• Anatomical alignment and absolute stability
• Gap healing
• Stability of fracture fragments w/ a gap less
  than 1mm between fragments.
• Secondary osteonal reconstruction
• Occurs with pin and wire stabilization of oblique
  fractures.

13
What are the different events that occur in these
subtypes.

• Contact
• Bone absorption and formation occur
  simultaneously, cutting cone of osteoclasts
  crosses fracture plane, followed by osteoblasts,
  cone advances at 50 to 80 um/day.
• Gap Healing
• Gap fills w/ blood, at 2wks osteoblasts deposit
  lamellar bone in gap perpendicular to fragments,
  3-4wks cutting cones in new bone and fragment
  ends cross fracutre plane, new lamellar bone
  becomes longitudinally oriented.
• Secondary osteonal reconstruction
• Bone resorption of fragment ends, external callus
  is formed, implant allows for rapid bridging of
  external callus, if gap is small then gap healing
  occurs, if gap is large then indirect healing
  occurs.

14
When are bone grafts commonly used?

• To enhance healing

15
What are the classifications of bone grafts,
based on a) type of donor used b) type of bone
used?

• A
• Autograft patients own bone
• Allograft bone from another individual of same
  species as patient
• Xenograft bone from individual of another
  species
• B
• Cancelloous
• Cortical
• Cortical-cancellous

16
In what 3 ways do bone grafts promote
osteogenesis?

• Graft provides cells directly
• Osteoinduction
• Osteoconduction

17
For each of the previous 3 ways, which type of
graft is used?

• Graft provides cells directly
• Cancellous graft
• Osteoinduction
• Cancellous graft
• Osteoconduction
• Cancellous graft, cortical graft

18
What is another function of bone grafts?

• Mechanical support

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Which type of graft is used for this function?

• Cortical graft

20
Where and how are cancellous and
cortical-cancellous bone grafts collected in dogs
and cats?

• Cancellous
• Hole is drilled through cortex with IM pin or
  bone drill, bone is harvested with bone curette,
  keep on moist sponge
• Proximal humerus, proximal tibia, wing of ilium.
  
• Cortical-cancellous
• Bone is cut with osteotome, oscillating saw or
  bone cutter
• Rib, iliac crest