Bone healing Flashcards
Strain
-Means a change in length (compression or stretch)
Which cells are better at handling strain?
- Granulation tissue 100%
- fibrous tissue 15%
- chondrocytes 10%
- osteoblasts 2%
Number of pieces of bone and how that relates to strain
More pieces= lower strain at each individual fracture site
less pieces= all strain concentrated at one position
Size of the gap and how it relates to strain
Larger gap= less strain
What affects bone healing?
The type of bone healing depends on:
1. size of the gap between fragments
2. the amount of motion at the fracture site
Types of bone healing
- secondary (indirect) healing
- Primary (direct) healing
Components of primary (direct) healing
- contact healing
- gap healing
Other names for Secondary healing
**Indirect healing **Endochondral ossification
**healing by callus formation
Secondary healing
Healing by a sequence of tissue types that make progressively stiffer matrix
When does secondary healing occur?
occurs in fractures that have some movement and/or more than 1mm gap
Steps of secondary healing
- fracture
- hematoma followed by fibrin clot
- fibrous tissue formation
- fibrocartilage formation from chondrocytes
*less mobile so cartilage can begin mineralizing - cartilage mineralization and blood vessel ingrowth
- bone formation from osteoblasts
- remodeling
Wolff’s Law
Bone will remodel in response to stress
*laid down where it is needed and reabsorbed where it is not needed
Growth factors affecting bone healing
Primary (direct) healing
-formation of bone without intermediate tissues coming first
What is needed for primary healing?
- close apposition of fragments
- blood supply
- rigid stabilization
Contact healing phase
- requires direct contact between fragments
- bone multicellular units (led by cutting cones) form spot welds
- then remodeling of laminar bone occurs
Gap healing component of primary healing
Need gap of 1mm or less between fragments and stabilized fracture
Steps of gap healing
- hematoma
- connective tissue/blood vessels in hematoma
- osteoblasts lay down lamellar bone in gap
- cutting cones go across new bone
Bone supply to the bone
- nutrient artery (medullary canal and endosteum)
- metaphyseal blood vessels
- periosteal blood vessels
- extraosseous blood supply of healing
*comes from muscle attachment so don’t disrupt them
Fracture repair with less blood disruption
- casts/splints
- external fixators
- cerclage wires if not tight
- bone plates (allow for gaps)
Anatomic repair
Perfect alignment and apposition of fragments
-some early weight transmission possible through reconstructed bone sparing the apparatus
What is required for anatomic repair?
Generous exposure and direct manipulation of fragments
Issue with anatomic repair
Disrupts the blood supple/early healing response to some extent
When do you choose anatomic repair?
-only for fractures that can be reconstructed
-when you expect fracture to heal slowly under the best of circumstances
-good when callus is undesirable
Biologic repair
No big attempt to reconstruct the fracture
-min blood supply disruption
-hardware bears all forces until fracture heals
Limb is pulled out to length and angular and rotational deformity are corrected
What are the approaches of biologic repair
1.closed
2. open but do not touch (OBDNT)
Issue with biologic repair
Bone usually heals more quickly BUT until the healing occurs, the hardware bears all of the forces of weightbearing
When should you choose to do a biologic repair?
-when you have a fracture with good blood supply that you expect to heal quickly
-fractures that you can’t reconstruct
*do not use in areas where a callus would be bad
