1. Session VII Bone healing

2. Bone Healing Possibility 1: Primary Bone Healing: What we Love to See.
Direct and intimate contact between fracture fragments
ORIF with atraumatic technique
Intact intramedullary vasculature
New bone grows directly across the compressed bone ends
Osteoclastic resorption followed by osteoblastic deposition
Rigid internal fixation. No movement.

3. ORIF primary bone healing

5. 2nd Possibility: Secondary Bone Healing What we usually see.
Denotes mineralization and bony replacement of a cartilage matrix with characteristic callus formation.
Some movement occurs at the fracture
No fixation or immobilization
Cast immobilization
External fixation
A study in the 80’s showed ORIF stronger for 4-6 weeks, then ORIF equal to casts for 4-6 weeks, then cast fractures stronger! Casts may allow an “ideal” amount of movement for piezogenic effect on osteoblasts. But it will be secondary bone healing.

6. Secondary Bone Healing: The fragments move slightly generating visible bone callus.
1 week: resorption of necrotic bone at fracture
10-14 days weeks: appearance of bone callus
6-12 weeks: callus increases (if motion is moderate to excessive) forming an exuberant callus. Creates risk of delayed union (6months+) or non-union (12months+) If motion is minimal callus gains density but not size.
3-6 months-bone strength increases, callus becomes more calcified and shows visible trabecular patterns.
6-12 months-callus remodels, reduces in size, angulation deformities may normalize.

7. Casts are stress sharing so secondary healing is expected.
3 months later

8. Secondary Bone
Callus formation expected with medullary nails.

9. Staging Healing Stage I: Inflammatory
Inflammatory phase: 10%
Lasts 1-2 weeks
Increased vascularity
Hematoma is invaded by inflammatory cells forming a meshwork
PDGF and TGF-ß -
Neutrophils, macrophages and osteoclasts
Debridement of wound
Strength is 0/4

11. Callus formation with/without ORIF

12. Stage II: Reparative Duration is several months
Differentiation of pluripotential mesenchymal cells
Hematoma invaded by chrondroblasts and fibroblasts that create a callus matrix
Formation of granulation tissue procallus.
Formation of fibrous callus. Collagen types I,II and III
Insulin, insulin like growth factors, osteogenin and morphogenic protein
Osteoblasts then mineralize the fibrous callus forming a hard or bony callus/woven bone.
Strength 3/4
Weak immature bone-fracture stability indicates the end of this phase
Delayed union and non union result from errors in this phase
Strength is 1-2/4

13. Bone callus just showing

14. 4-6 weeks or more callus is more easily seen radiographically than earlier.

15. Stage III: Remodeling Months to years to complete
Replacement of immature disorganized woven bone with mature organized lamellar bone. Increases stability. Shift to type I collagen
Resorption of bone from convex surfaces and deposition on concave surfaces.
Radiographically the fx is usually no longer visible.
Strength is 4/4

18. Fracture Healing: Variables
Remember a transverse fx is clean and possibly relatively atraumatic but…
May injury nutrient foramen if midshaft
Has little surface area for healing
Is mechanically very weak and unstable.
Oblique fx may create more initial trauma but…
Nutrient artery intact?
Great surface area for healing
Stress fx: no visible fx line. Watch for callus formation instead. May not be invisible for days

19. Variables on X-ray
Metaphyseal fractures show little callus
Impaction of fragments, interdigitation of spicules, minimum periosteum
Diaphyseal fx, even if fixated, show external callus
Lack of impaction, presence of gap
Intracapsular fx show little callus because of absence of periosteum
Femoral neck intracapsular but intertrochanteric are extracapsular
Rigidly fixated fx show less callus
Overall trauma and age
OK, here goes a high speed review of fracture healing…

20. Immediate Post Op

21. 1 day

22. Less than 1 week

23. Less than 1 week

24. Less than 1 week

25. Fuzzy more rounded fx surfaces. 1-2 weeks

26. 3-6 weeks with stable fixation.
Some motion is occurring to produce the visible bone callous.

27. 3-6 weeks callus is now visible.

28. 6-10 weeks Can you explain this to your patient?

29. 8-10 weeks

30. 12-16 weeks Bone Callus formation is maturing

31. Bone Callus Formation with trabecular bridging

32. About 12-16 weeks post injury
About weeks post injury. The moderate amount of callus indicates little motion has occured. Cautious weight bearing OK??

33. If this was your patient at 6 months what would be your assessment?
Delayed union at 6 months. A Non Union is determined after about 12 months healing.