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===Fracture classification===
*'''Traumatic''' - normal bone broken by excessive force
*'''Pathologic''' - abnormal bone broken by minimal or no trauma
**E.g. due to [[Osteomyelitis|osteomyelitis]], [[:Category:Bones - Neoplastic Pathology|bone neoplasia]]
*'''Closed''' - overlying skin and soft tissue is intact
*'''Compound''' - overlying skin and soft tissue are perforated
*'''Comminuted''' - bone is shattered at fracture site
*'''Compresses''' - the ends of the fracture are impacted into each other
*'''Avulsed''' - due to pull of a ligament
*'''Transverse'''
*'''Spiral'''
===Fracture repair===
[[Image:Recent healing fracture.jpg|right|thumb|100px|<small><center>Recent healing fracture (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Fracture
**Ruptured blood vessels -> haemorrhage and clot formation, some ischaemic necrosis
***Dead marrow liquefies and is phagocytosed
***Dead bone is removed by [[Bones - Anatomy & Physiology|osteoclasts]]
****Continues long after bone has been united by callus
**[[Bones - Anatomy & Physiology|Periosteum]] tears, fragments displaced
*-> Haematoma formation, necrosis of any isolated fragments
*-> Mesenchymal cells proliferate in haematoma - [[Granulation Tissue|granulation tissue]]
**Invading cells: endothelial, fibroblasts, osteoprogenitor
*-> Loose collagenous tissue (primary callus)
*-> Mesenchymal cells differentiate to [[Bones - Anatomy & Physiology|osteoblasts]] and chondroblasts
*-> [[Bones - Anatomy & Physiology|Woven bone]] (secondary callus)
**External callus - from periosteum
***Periosteal growth eventually bridges the gap between the fracture ends
***Blood supply is outstripped
***Cartilage is produced instead of osteoid
***Blood vessels invade cartilage -> [[Bone & Cartilage Development - Anatomy & Physiology|endochondral ossification]]
***Osteoid becomes ossified
**Internal callus - from endosteum
***Rarely forms cartilage
***May occlude the medullary cavity
**Osteoid remodelled by [[Bones - Anatomy & Physiology|osteoclastic resorption]]
*-> Mature [[Bones - Anatomy & Physiology|lamellar bone]]
*Early reactive fracture repair may be mistaken for [[Osteosarcoma|osteosarcoma]] on biopsy
===Complications of fracture repair===
*Malnutrition
*Lack of adequate blood supply (leads to hypoxia)
**Leads to excess cartilage in callus
**Healing can still occur since this can turn to bone
*Excess movement
**Leads to excess fibrous tissue in callus adn formation of false joint (below)
*Presence of necrotic bone (may form a sequestrum)
*Poor alignment
*[[Osteitis|Bacterial infection]]
===Pseudoarthrosis===
*False joint
*Non-osseus union
*From infection, poor imobilisation, avascularity, extensive tearing damage to periosteum
*Composed of fibrous tissue
*If mobility continues -> hyaline cartilage forms -> neoarthrosis (formation of new joint)
*In [[Hyperparathyroidism|''Osteodystrophia fibrosa'']], [[Osteomalacia|osteomalacia]] and [[Rickets|rickets]] - callus forms but does not mineralise
===Head and neck of femur fracture===
*Vascularisation from joint capsule -> if complete separation -> bone and marrow undergo avascular necrosis
*Fibrovascular tissue and osteogenic cells invade -> deposit new bone
*Resorption of articular cartilage and subchondral bone -> '''osteoarthropathy''' commonly develops
===Sore shins===
*Dorsal metacarpal disease of racehorses
*In 2-3 year olds
*Excessive compressive stress on dorsal cortex of third metacarpal -> microfractures
*Hyperaemic overlying periosteum - -> new bone production to cover the lesion
===Causes of Fracture===
===Causes of Fracture===
* The causes of fracture fit into two distinct categories:
* The causes of fracture fit into two distinct categories:
# Infection delays healing due to the effects of the toxins on theproliferating cells.
# Infection delays healing due to the effects of the toxins on theproliferating cells.
#* May give rise to a systemic infection affecting the rest of the body.
#* May give rise to a systemic infection affecting the rest of the body.
[[Category:Bones - Degenerative Pathology]]