Bone Healing Flashcards
Osteoblasts Function
Produce osteoid (unmineralized bone matrix) on bone surface to form Haversian System Transport Calcium and phosphorus from extracellular matrix into osteoid seam High levels of protein synthesis
Osteocytes
Osteoblasts that have been encased in mineralized matrix
House in lacunae with cytoplasmic processes within canaliculi
Osteocytes function
Maintain bone matrix
Osteoclasts
Large multinucleated cells derived from pluripotential cells of bone marrow
Active in areas of bone remodeling
Osteoclasts function
Resorb bone through degradation of: Collagenous proteins, Non-collagenous proteins, and Bone Minerals
Phases of Bone Healing
Inflammatory Phase
Repair Phase
Remodeling Phase
Inflammatory Phase
Death of osteocytes at results in release of lysosomal enzymes
Necrotic material at site of fracture is source of inflammatory response
Release of acute phase proteins
Release of growth factors form platelets, macrophages, granulocytes, and lymphocytes
Osteoclasts resorb and remove devitalized bone at fracture ends
How long does the inflammatory phase last?
2-3 weeks
Repair Phase
Migration of osteoprogenitor cells to form external periosteal callus
Angiogenesis results in transient blood supply from surrounding soft tissues
Chondro-, fibro-, and osteoblasts inhabit callus producing collagen
Deposition of calcium hydroxyapatite in matrix resulting in callus mineralization - rapid increase in stability
Cartilage replaced by bone via endochondral ossification
Remodeling Phase
Begins when fracture is bridges by callus
Woven bone remodeled into lamellar bone via action of osteoclasts and osteoblasts
Slow process directed by stresses of weight bearing
What are the primary/direct types of bone healing?
Gap Healing
Contact Healing
Contact Healing
Occurs under compression of bone ends under rigid fixation
No cartilaginous callus formed
Cutting cones form across fracture line followed by longitudinal deposition of lamellar bone
Gap Healing
Gap between fracture ends less than 1 mm
Granulation tissue at gap followed by transversely oriented lamellar bone
Haversarian remodeling occurs at 3 weeks post stabilization
Secondary Bone Healing
Fracture ends do not touch
Micromotion at fracture promotes formation of callus - Results in release of growth factors that promote bone union
Bone heals via mineralization of fibrocartilaginous callus into bony callus
Why are fracture ends not compressed?
Protection of surrounding soft tissues
Protection of blood supply at site of fracture
MIPO
Minimally Invasive Plate Osteosynthesis
What is used in secondary bone healing?
Plates in Bridging Mode
External Skeletal Fixation
Interlocking nails
What is the average healing time of fractures?
6-8 weeks
What are the factors that affect bone healing?
Fracture configuration/severity Soft tissue damage Stability of repair Presence of Infection Patient factors Compliance
A’s of evaluation of bone healing
Alignment
Apposition
Apparatus
Activity
Assessment of Bone Healing
Lysis
Periosteal reaction
New Bone formation
Bone resorption
Delayed Union
Healing is prolonged beyond normal expected time course
Fracture line remains evident with feathery/wooly ends
Callus is visible but lacks appropriate mineralization
No sclerosis of bone ends
Sclerosis
no blood supply to the fracture
Malunion
Failure to re-establish normal form and function in the face of healing
Nonunion Viable
Biologically active fracture with cartilage and fibrous tissue between fracture ends
Nonunion Nonviable
Fracture ends are sclerotic with rounded bone edges and visible fracture gap
Characteristics of Nonviable Nonunion fractures
Dystrophic
Necrotic
Defect
Atrophic
Treatment of Delayed Union
Bone grafts
Increased mechanical stiffness of implants
Bone morphogenic protein
Treatment option of Non-union
Rigid stabilization
Removal of loose implants
Encourage biologically active environment: Bone graft, Bone marrow, Demineralized bone matrix, Bone morphologenic proteins
Removal of non-viable bone
What are other options for treatment of non bone healing?
Extracorporeal shock wave therapy
Pulsed Electromagnetic Field
Low intensity pulsed Ultrasonography
