“Notes: Bone Injury & Repair”

(1) Bone Injury(1) Bone Injury

• Increased weight on bone/joint

• Irregular movement/manipulation– Twisting– Rotation– Bending

(2) Types of Fractures(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

Fracture Types Continued…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)

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

Fracture Types Continued…Fracture Types Continued…

(3) Bone Repair(3) Bone Repair

1- [Instantly] Hematoma Formation

2- [~2-3days] Fibrocartilaginous Callus Formation

3- [~7days] Bony Callus Formation

4- [~6-8weeks] Bone Remodeling

(4) Hematoma Formation(4) Hematoma Formation

1. Bone breaks, blood vessels are torn and hemorrhage.

2. Mass of clotted blood forms at fracture site.

3. Bone cells are deprived of nutrition and die.

4. Tissue at fracture site becomes swollen, painful and inflamed.

(5) Fibrocartilaginous Callus (5) Fibrocartilaginous Callus FormationFormation

1. Capillaries from surrounding vessels grow into the hematoma.

2. Phagocytic cells (Macrophages + Osteoclasts) invade hematoma and clean up debris.

3. Osteoblasts + Osteocytes invade and begin to rebuild bone.

4. Collagen fibers are secreted to connect ends of bone.

(6) Bony Callus Formation(6) Bony Callus Formation

1. Fibrocartilaginous callus develops and hardens to form a bony callus of spongy bone.

2. Bone cells, collagen fibers and chondrocytes (cartilage cells) are continuously secreted to strengthen matrix.

(7) Final Remodeling(7) Final Remodeling

1. Excess material on outside of diaphysis is removed.

2. Compact bone is laid down to reconstruct shaft walls.