Difference between revisions of "Fractures"
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− | * [[ | + | ===Fracture classification=== |
− | * [[ | + | |
− | * [[Non- | + | *'''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=== | ||
+ | * The causes of fracture fit into two distinct categories: | ||
+ | *# '''Fracture of trauma''' | ||
+ | *#* Breakage of normal healthy bone due to excessive stress pressure of short duration. | ||
+ | *# '''Pathological fracture''' | ||
+ | *#* Breakage of bone weakened by some underlying metabolic, inflammatory or neoplastic condition. | ||
+ | |||
+ | ===Description of a Fracture=== | ||
+ | * There are various terms to describe a fracture's appearance. | ||
+ | * Separation of the ends of the fracture may be '''complete''' or '''incomplete'''. | ||
+ | * When there is no penetration of the overlying skin, a the fracture is described as '''closed'''. | ||
+ | * When the sharp ends penetrate the overlying skin, the fracture is '''compound'''. | ||
+ | ** In this scenario there is the danger of introducing infection. | ||
+ | *'''Comminuted''' describes a fracture where there are multiple small fragments of bone at the site of breakage. | ||
+ | * Where the edges of the fracture are impacted into each other, the fracture is said to be '''compressed'''. | ||
+ | * When one side of the fracture is depressed below the plane of the other, the term '''depressed''' is used. | ||
+ | ** This occurs in the flat bones of the skull. | ||
+ | * '''Microfractures''' are fractures that are only visible on histological section as cracks in the bone. | ||
+ | ** Grossly, there might be evidence of some haemorrhage in the area. | ||
+ | |||
+ | ===Fracture Repair=== | ||
+ | [[Image:fracture repair.jpg|thumb|right|150px|Fracture repair (Courtesy of BioMed Archive)]] | ||
+ | * On breakage, there is rupture of the periosteal, cortical and medullary vessels, causing: | ||
+ | ** A blood clot in the breakage area. | ||
+ | *** Fibrin is the important component. | ||
+ | ** Local necrosis of tissue supplied by these vessels. | ||
+ | *** This lowers the local pH. | ||
+ | * The fate of the blood clot depends upon its location. | ||
+ | ** The periosteal portion is lysed and disappears; | ||
+ | ** The medullary portion is removed by macrophages. | ||
+ | * The necrotic material is removed by phagocytosis. | ||
+ | ** Necrotic [[Bone Marrow - Anatomy & Physiology|bone marrow]] is removed by [[Macrophages|macrophages]]. | ||
+ | *** This is a fairly rapid process. | ||
+ | ** Osteoclasts remove necrotic bone. | ||
+ | *** This is a slow process. | ||
+ | * On the periosteal side, the periosteum proliferates into the clot. | ||
+ | ** Forms a fibrous collar around the bone called the soft callus. | ||
+ | * 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)]] | ||
+ | ** Grow across the divide between the two fragments, laying down coarse woven bone. | ||
+ | * The woven bone laid is known as the hard callus. | ||
+ | ** This periosteal coarse bone is of utmost importance in repair. | ||
+ | *** It is responsible for much of the strength of the fracture repair. | ||
+ | ** This is replaced over a period of time by mature compact bone. | ||
+ | *** Aligns itself according to the stresses applied to it. | ||
+ | * Periosteal cells that are further away from the fracture fragments differentiate into cartilage-producing cells. | ||
+ | ** Produce a cone of cartilage between the two fragments. | ||
+ | *** As the local pH changes to more alkaline conditions, this cartilage undergoes calcification, with invasion by blood vessels and osteoblasts. | ||
+ | **** The cartilage is replaced by bone - endochondral ossification. | ||
+ | * On the medullary side, the endosteum proliferates and invades the clot, laying down bone. | ||
+ | ** This bone may totally occlude the medulla and is later remodelled to reconstitute a patent lumen. | ||
+ | |||
+ | ===Complications=== | ||
+ | * There are several possible complications that may arise in the repair of bone. | ||
+ | # Inadequate immobilisation of the fractured ends will lead to incomplete repair by callus formation. | ||
+ | #* An intervening mass of fibrocartilage remains, forming a false joint. | ||
+ | #** In some cases the false joint can even appear to form a synovial lining. | ||
+ | #* If the fractured ends are sufficiently far apart, no substantial callus forms. | ||
+ | #** The intervening space is taken up by connective tissue organisation. | ||
+ | # Failure to align the fractured ends in proper apposition to one another will produce excessive callus. | ||
+ | #* This takes a longer time to be remodelled by the adult compact bone. | ||
+ | # [[Healing and Repair - Pathology#Description of a Fracture|Comminution]] delays healing due to persistent irritation. | ||
+ | # 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. | ||
+ | |||
+ | |||
+ | [[Category:Bones - Degenerative Pathology]] |
Latest revision as of 13:16, 3 March 2011
Fracture classification
- Traumatic - normal bone broken by excessive force
- Pathologic - abnormal bone broken by minimal or no trauma
- E.g. due to osteomyelitis, 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
- Fracture
- Ruptured blood vessels -> haemorrhage and clot formation, some ischaemic necrosis
- Dead marrow liquefies and is phagocytosed
- Dead bone is removed by osteoclasts
- Continues long after bone has been united by callus
- Periosteum tears, fragments displaced
- Ruptured blood vessels -> haemorrhage and clot formation, some ischaemic necrosis
- -> Haematoma formation, necrosis of any isolated fragments
- -> Mesenchymal cells proliferate in haematoma - granulation tissue
- Invading cells: endothelial, fibroblasts, osteoprogenitor
- -> Loose collagenous tissue (primary callus)
- -> Mesenchymal cells differentiate to osteoblasts and chondroblasts
- -> 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 -> endochondral ossification
- Osteoid becomes ossified
- Internal callus - from endosteum
- Rarely forms cartilage
- May occlude the medullary cavity
- Osteoid remodelled by osteoclastic resorption
- External callus - from periosteum
- -> Mature lamellar bone
- Early reactive fracture repair may be mistaken for 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
- 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 Osteodystrophia fibrosa, osteomalacia and 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
- The causes of fracture fit into two distinct categories:
- Fracture of trauma
- Breakage of normal healthy bone due to excessive stress pressure of short duration.
- Pathological fracture
- Breakage of bone weakened by some underlying metabolic, inflammatory or neoplastic condition.
- Fracture of trauma
Description of a Fracture
- There are various terms to describe a fracture's appearance.
- Separation of the ends of the fracture may be complete or incomplete.
- When there is no penetration of the overlying skin, a the fracture is described as closed.
- When the sharp ends penetrate the overlying skin, the fracture is compound.
- In this scenario there is the danger of introducing infection.
- Comminuted describes a fracture where there are multiple small fragments of bone at the site of breakage.
- Where the edges of the fracture are impacted into each other, the fracture is said to be compressed.
- When one side of the fracture is depressed below the plane of the other, the term depressed is used.
- This occurs in the flat bones of the skull.
- Microfractures are fractures that are only visible on histological section as cracks in the bone.
- Grossly, there might be evidence of some haemorrhage in the area.
Fracture Repair
- On breakage, there is rupture of the periosteal, cortical and medullary vessels, causing:
- A blood clot in the breakage area.
- Fibrin is the important component.
- Local necrosis of tissue supplied by these vessels.
- This lowers the local pH.
- A blood clot in the breakage area.
- The fate of the blood clot depends upon its location.
- The periosteal portion is lysed and disappears;
- The medullary portion is removed by macrophages.
- The necrotic material is removed by phagocytosis.
- Necrotic bone marrow is removed by macrophages.
- This is a fairly rapid process.
- Osteoclasts remove necrotic bone.
- This is a slow process.
- Necrotic bone marrow is removed by macrophages.
- On the periosteal side, the periosteum proliferates into the clot.
- Forms a fibrous collar around the bone called the soft callus.
- The cells in the inner aspect of the soft callus, particularly those near the fracture fragments, differentiate into osteoblasts.
- Grow across the divide between the two fragments, laying down coarse woven bone.
- The woven bone laid is known as the hard callus.
- This periosteal coarse bone is of utmost importance in repair.
- It is responsible for much of the strength of the fracture repair.
- This is replaced over a period of time by mature compact bone.
- Aligns itself according to the stresses applied to it.
- This periosteal coarse bone is of utmost importance in repair.
- Periosteal cells that are further away from the fracture fragments differentiate into cartilage-producing cells.
- Produce a cone of cartilage between the two fragments.
- As the local pH changes to more alkaline conditions, this cartilage undergoes calcification, with invasion by blood vessels and osteoblasts.
- The cartilage is replaced by bone - endochondral ossification.
- As the local pH changes to more alkaline conditions, this cartilage undergoes calcification, with invasion by blood vessels and osteoblasts.
- Produce a cone of cartilage between the two fragments.
- On the medullary side, the endosteum proliferates and invades the clot, laying down bone.
- This bone may totally occlude the medulla and is later remodelled to reconstitute a patent lumen.
Complications
- There are several possible complications that may arise in the repair of bone.
- Inadequate immobilisation of the fractured ends will lead to incomplete repair by callus formation.
- An intervening mass of fibrocartilage remains, forming a false joint.
- In some cases the false joint can even appear to form a synovial lining.
- If the fractured ends are sufficiently far apart, no substantial callus forms.
- The intervening space is taken up by connective tissue organisation.
- An intervening mass of fibrocartilage remains, forming a false joint.
- Failure to align the fractured ends in proper apposition to one another will produce excessive callus.
- This takes a longer time to be remodelled by the adult compact bone.
- Comminution delays healing due to persistent irritation.
- 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.