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

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.