Healing Of Fractures

Osteology – Healing of Fractures

Osteology – Healing of Fractures • 5 histologic stages of fracture healing: 1. Fracture 2. Formation of granulation tissue around fractured bone ends 3. Replacement of granulation tissue by callus 4. Replacement of callus by lamellar bone 5. Remodeling of bone to normal contour

Osteology – Healing of Fractures 1. Fracture 2. Formation of granulation tissue 3. Replacement of granulation tissue by callus 4. Replacement of callus by lamellar bone 5. Remodeling of bone to normal contour

Reactive phase

Reparative phase

Remodeling phase

Osteology – Healing of Fractures • Fracture causes haemorrhage and tissue destruction; blood clot forms (hours) • Proliferating fibroblasts and capillary sprouts grow into blood clot in injured area, forming granulation tissue, in response to cytokines released by tissue damage (days)

Fracture Healing

Haemorrhage Tissue destruction Proliferating fibroblasts and capillary sprouts grow into blood clot in injured area, forming granulation tissue

Modified from Junqueira

Osteology – Healing of Fractures - continued • Invaded by polymorphonuclear leukocytes, macrophages (also responding to cytokines), which phagocytize debris (blood clot, cells, damaged matrix) • Granulation tissue becomes denser • Cartilage formed (? from primitive mesenchymal cells or demodulation of other cells) (weeks)

Fracture Healing

Invaded by neutrophils, macrophages which phagocytize debris Granulation tissue becomes denser Cartilage forms Modified from Junqueira

Osteology – Healing of Fractures - continued • Connective tissue + cartilage tissue = callus • Callus temporarily binds, stabilizes bone • Dormant osteogenic cells of periosteum enlarge and become osteoblasts • Osseous tissue deposited on outside of bone some distance from fracture • Formation of new bone continues toward fractured ends of bone

Fracture Healing Connective tissue + Cartilage tissue = Callus Callus temporarily binds and stabilizes bone Dormant osteogenic cells of periosteum enlarge, become osteoblasts, deposit osseous material on outside of bone centripetally Modified from Junqueira

Osteology – Healing of Fractures - continued • U.S. Civil War studies quoted by Norman Sauer (in Forensic Osteology, 2nd edition, K. Reichs, ed.), macroscopic evidence of bone healing is seen as early as 7 days post injury, and on average is seen at 13 days post injury

Osteology – Healing of Fractures - continued • Finally forms sheath of bone over fibrocartilaginous callus (1-2 months) • Osteogenic buds invade fibrocartilaginous callus and replace it with bony callus • In replacement of fibrocartilaginous callus, cartilage undergoes calcification and absorption same as intracartilaginous bone formation

Fracture Healing Sheath of bone is formed over fibrocartilaginous callus; osteogenic buds invade this callus and replace it with bony callus; in replacement of this callus, cartilage undergoes calcification and absorption same as in intracartilaginous bone formation

Modified from Junqueira

Osteology – Healing of Fractures - continued • Intramembranous bone formation also occurs • When subperiosteal bone formation is occurring, medullary bone forms centripetally from both sides of fracture, aiding bony union (Junqueira); Cormack indicates that medullary bone forms centrifugally

Summary diagram of bone healing

From Cormack

Fracture Healing

From Junqueira

Osteology – Healing of Fractures - continued • Process varies with degree of displacement of fractured ends of bone and degree of trauma inflicted • Uneven or protruding surfaces are gradually removed and healed bone, especially in young individuals, assumes its normal contour – remodeling (months to years) (Junqueira)

Fracture Healing

From Junqueira

Summary diagram of bone healing

From Cormack

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