Post on 14-Jan-2016
Session VII
Bone healing
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.
ORIF primary bone healing
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.
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.
Casts are stress sharing so secondary healing is expected.
3 months later
Secondary Bone
Callus formation expected with medullary nails.
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
Callus formation with/without ORIF
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
Bone callus just showing
4-6 weeks or more callus is more easily seen radiographically than earlier.
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
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 10-14 days
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…
Immediate Post Op
1 day
Less than 1 week
Less than 1 week
Less than 1 week
Fuzzy more rounded fx surfaces. 1-2 weeks
3-6 weeks with stable fixation.
Some motion is occurring to produce the visible bone callous.
3-6 weeks callus is now visible.
6-10 weeks Can you explain this to your patient?
8-10 weeks
12-16 weeks Bone Callus formation is maturing
Bone Callus Formation with trabecular bridging
About 12-16 weeks post injury. The
moderate amount of callus indicates little motion has
occured. Cautious weight bearing
OK??
Delayed union at 6 months.A Non Union is determined after
about 12 months healing.
If this was your patient at 6 months what would be your assessment?