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| − | ===Fracture classification===
| + | * [[Diaphyseal Fractures - Small Animal]] |
| − | | + | * [[Fractures - Bovine]] |
| − | *'''Traumatic''' - normal bone broken by excessive force
| + | * [[Fractures - Equine]] |
| − | *'''Pathologic''' - abnormal bone broken by minimal or no trauma
| + | * [[Non-diaphyseal Fractures - Small Animal]] |
| − | **E.g. due to [[Osteomyelitis|osteomyelitis]], [[:Category:Bones - Neoplastic Pathology|bone neoplasia]]
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| − | *'''Closed''' - overlying skin and soft tissue is intact
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| − | *'''Compound''' - overlying skin and soft tissue are perforated
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| − | *'''Comminuted''' - bone is shattered at fracture site
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| − | *'''Compresses''' - the ends of the fracture are impacted into each other
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| − | *'''Avulsed''' - due to pull of a ligament
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| − | *'''Transverse'''
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| − | *'''Spiral'''
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| − | ===Fracture repair===
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| − | [[Image:Recent healing fracture.jpg|right|thumb|100px|<small><center>Recent healing fracture (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | *Fracture
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| − | **Ruptured blood vessels -> haemorrhage and clot formation, some ischaemic necrosis
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| − | ***Dead marrow liquefies and is phagocytosed
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| − | ***Dead bone is removed by [[Bones - Anatomy & Physiology|osteoclasts]]
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| − | ****Continues long after bone has been united by callus
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| − | **[[Bones - Anatomy & Physiology|Periosteum]] tears, fragments displaced
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| − | *-> Haematoma formation, necrosis of any isolated fragments | |
| − | *-> Mesenchymal cells proliferate in haematoma - [[Granulation Tissue|granulation tissue]]
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| − | **Invading cells: endothelial, fibroblasts, osteoprogenitor
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| − | *-> Loose collagenous tissue (primary callus)
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| − | *-> Mesenchymal cells differentiate to [[Bones - Anatomy & Physiology|osteoblasts]] and chondroblasts
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| − | *-> [[Bones - Anatomy & Physiology|Woven bone]] (secondary callus) | |
| − | **External callus - from periosteum
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| − | ***Periosteal growth eventually bridges the gap between the fracture ends
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| − | ***Blood supply is outstripped
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| − | ***Cartilage is produced instead of osteoid
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| − | ***Blood vessels invade cartilage -> [[Bone & Cartilage Development - Anatomy & Physiology|endochondral ossification]]
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| − | ***Osteoid becomes ossified
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| − | **Internal callus - from endosteum
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| − | ***Rarely forms cartilage
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| − | ***May occlude the medullary cavity
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| − | **Osteoid remodelled by [[Bones - Anatomy & Physiology|osteoclastic resorption]]
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| − | *-> Mature [[Bones - Anatomy & Physiology|lamellar bone]]
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| − | *Early reactive fracture repair may be mistaken for [[Osteosarcoma|osteosarcoma]] on biopsy
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| − | ===Complications of fracture repair===
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| − | *Malnutrition
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| − | *Lack of adequate blood supply (leads to hypoxia)
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| − | **Leads to excess cartilage in callus
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| − | **Healing can still occur since this can turn to bone
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| − | *Excess movement
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| − | **Leads to excess fibrous tissue in callus adn formation of false joint (below)
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| − | *Presence of necrotic bone (may form a sequestrum)
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| − | *Poor alignment
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| − | *[[Osteitis|Bacterial infection]]
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| − | ===Pseudoarthrosis===
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| − | *False joint
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| − | *Non-osseus union
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| − | *From infection, poor imobilisation, avascularity, extensive tearing damage to periosteum
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| − | *Composed of fibrous tissue
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| − | *If mobility continues -> hyaline cartilage forms -> neoarthrosis (formation of new joint)
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| − | *In [[Hyperparathyroidism|''Osteodystrophia fibrosa'']], [[Osteomalacia|osteomalacia]] and [[Rickets|rickets]] - callus forms but does not mineralise
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| − | ===Head and neck of femur fracture===
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| − | *Vascularisation from joint capsule -> if complete separation -> bone and marrow undergo avascular necrosis
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| − | *Fibrovascular tissue and osteogenic cells invade -> deposit new bone
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| − | *Resorption of articular cartilage and subchondral bone -> '''osteoarthropathy''' commonly develops
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| − | ===Sore shins===
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| − | *Dorsal metacarpal disease of racehorses
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| − | *In 2-3 year olds
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| − | *Excessive compressive stress on dorsal cortex of third metacarpal -> microfractures
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| − | *Hyperaemic overlying periosteum - -> new bone production to cover the lesion
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| − | ===Causes of Fracture===
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| − | * The causes of fracture fit into two distinct categories:
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| − | *# '''Fracture of trauma'''
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| − | *#* Breakage of normal healthy bone due to excessive stress pressure of short duration.
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| − | *# '''Pathological fracture'''
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| − | *#* Breakage of bone weakened by some underlying metabolic, inflammatory or neoplastic condition.
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| − | ===Description of a Fracture===
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| − | * There are various terms to describe a fracture's appearance.
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| − | * Separation of the ends of the fracture may be '''complete''' or '''incomplete'''.
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| − | * When there is no penetration of the overlying skin, a the fracture is described as '''closed'''.
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| − | * When the sharp ends penetrate the overlying skin, the fracture is '''compound'''.
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| − | ** In this scenario there is the danger of introducing infection.
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| − | *'''Comminuted''' describes a fracture where there are multiple small fragments of bone at the site of breakage.
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| − | * Where the edges of the fracture are impacted into each other, the fracture is said to be '''compressed'''.
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| − | * When one side of the fracture is depressed below the plane of the other, the term '''depressed''' is used.
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| − | ** This occurs in the flat bones of the skull.
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| − | * '''Microfractures''' are fractures that are only visible on histological section as cracks in the bone.
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| − | ** Grossly, there might be evidence of some haemorrhage in the area.
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| − | ===Fracture Repair===
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| − | [[Image:fracture repair.jpg|thumb|right|150px|Fracture repair (Courtesy of BioMed Archive)]]
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| − | * On breakage, there is rupture of the periosteal, cortical and medullary vessels, causing:
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| − | ** A blood clot in the breakage area.
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| − | *** Fibrin is the important component.
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| − | ** Local necrosis of tissue supplied by these vessels.
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| − | *** This lowers the local pH.
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| − | * The fate of the blood clot depends upon its location.
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| − | ** The periosteal portion is lysed and disappears;
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| − | ** The medullary portion is removed by macrophages.
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| − | * The necrotic material is removed by phagocytosis.
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| − | ** Necrotic [[Bone Marrow - Anatomy & Physiology|bone marrow]] is removed by [[Macrophages|macrophages]].
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| − | *** This is a fairly rapid process.
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| − | ** Osteoclasts remove necrotic bone.
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| − | *** This is a slow process.
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| − | * On the periosteal side, the periosteum proliferates into the clot.
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| − | ** Forms a fibrous collar around the bone called the soft callus.
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| − | * The cells in the inner aspect of the soft callus, particularly those near the fracture fragments, differentiate into osteoblasts. [[Image:fracture callus.jpg|thumb|right|150px|Fracture callus (Courtesy of BioMed Archive)]]
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| − | ** Grow across the divide between the two fragments, laying down coarse woven bone.
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| − | * The woven bone laid is known as the hard callus.
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| − | ** This periosteal coarse bone is of utmost importance in repair.
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| − | *** It is responsible for much of the strength of the fracture repair.
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| − | ** This is replaced over a period of time by mature compact bone.
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| − | *** Aligns itself according to the stresses applied to it.
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| − | * Periosteal cells that are further away from the fracture fragments differentiate into cartilage-producing cells.
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| − | ** Produce a cone of cartilage between the two fragments.
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| − | *** As the local pH changes to more alkaline conditions, this cartilage undergoes calcification, with invasion by blood vessels and osteoblasts.
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| − | **** The cartilage is replaced by bone - endochondral ossification.
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| − | * On the medullary side, the endosteum proliferates and invades the clot, laying down bone.
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| − | ** This bone may totally occlude the medulla and is later remodelled to reconstitute a patent lumen.
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| − | ===Complications===
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| − | * There are several possible complications that may arise in the repair of bone.
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| − | # Inadequate immobilisation of the fractured ends will lead to incomplete repair by callus formation.
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| − | #* An intervening mass of fibrocartilage remains, forming a false joint.
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| − | #** In some cases the false joint can even appear to form a synovial lining.
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| − | #* If the fractured ends are sufficiently far apart, no substantial callus forms.
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| − | #** The intervening space is taken up by connective tissue organisation.
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| − | # Failure to align the fractured ends in proper apposition to one another will produce excessive callus.
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| − | #* This takes a longer time to be remodelled by the adult compact bone.
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| − | # [[Healing and Repair - Pathology#Description of a Fracture|Comminution]] delays healing due to persistent irritation.
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| − | # Infection delays healing due to the effects of the toxins on theproliferating cells.
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| − | #* May give rise to a systemic infection affecting the rest of the body.
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| − | [[Category:Bones - Degenerative Pathology]]
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