1. “Notes: Bone Injury & Repair”

2. (1) Bone Injury Increased weight on bone/joint
Irregular movement/manipulation
Twisting
Rotation
Bending

4. (2) Types of Fractures Comminuted:
Bone fragments into 3 or more pieces
Common in aged people, when bones are more brittle
Spiral:
Ragged break
Result of excessive twisting forces
Common sports fracture
Depressed:
Portion of broken bone pressed inward
Typical skull fracture

5. Fracture Types Continued…
Transverse
Bone breaks straight through bone (perpendicular)
Clean Break
Oblique
Bone breaks on diagonal
Clean break
Open
Bone breaks and pierces skin
Common in forearm and shin (leg)

6. Fracture Types Continued…
Compression:
Bone is crushed
Common in porous bones (due to osteoporosis)
Common in vertebral column
Epiphyseal:
Epiphysis separates from diaphysis along epiphyseal plate
Usually occurs where cartilage cells are dying and calcifying
Greenstick:
Bone breaks incompletely (like a twig)
Only one side of the shaft breaks, other side bends
Common in children, when bones are more flexible

7. (3) Bone Repair 1- [Instantly] Hematoma Formation
2- [~2-3days] Fibrocartilaginous Callus Formation
3- [~7days] Bony Callus Formation
4- [~6-8weeks] Bone Remodeling

8. (4) Hematoma Formation
Bone breaks, blood vessels are torn and hemorrhage.
Mass of clotted blood forms at fracture site.
Bone cells are deprived of nutrition and die.
Tissue at fracture site becomes swollen, painful and inflamed.

10. (5) Fibrocartilaginous Callus Formation
Capillaries from surrounding vessels grow into the hematoma.
Phagocytic cells (Macrophages + Osteoclasts) invade hematoma and clean up debris.
Osteoblasts + Osteocytes invade and begin to rebuild bone.
Collagen fibers are secreted to connect ends of bone.

12. (6) Bony Callus Formation
Fibrocartilaginous callus develops and hardens to form a bony callus of spongy bone.
Bone cells, collagen fibers and chondrocytes (cartilage cells) are continuously secreted to strengthen matrix.

13. (7) Final Remodeling
Excess material on outside of diaphysis is removed.
Compact bone is laid down to reconstruct shaft walls.