Fracture Management Flashcards
What are the 5 functions of bone?
Locomotion Haemopoesis Support Protection Lipid and mineral storage
Where does red marrow reside in?
Cancellous bone
What are osteogenic stem cells?
Derived from mesenchymal stem cells and have the capacity to differentiate into osteoblasts and chondroblasts.
What are osteocytes?
Osteocytes are mature osteoblasts that have been enveloped within the bone matrix.
• Continue to form bone to an extent (maintain strength of the bone matrix).
• Osteocytes reside within the lacuna and communicates with surroundings by canaliculi.
• Cytoplasmic processes of the osteocyte extend distally from the cell towards other osteocytes by canaliculi – waste product and nutrient exchange is supported to maintain viability.
Where do osteocytes reside?
Lacuna
What is the main function of osteocytes?
Capable of bone deposition and resorption involved in bone deformation caused by muscular activity
Strengthens bone in response to additional stresses
What are osteoblasts?
Responsible for the catalysing and synthesising the mineralisation of osteoid during bone formation and remodelling.
• Arise from the differentiation of osteogenic cells in the periosteum – the tissue that covers the superficial surface of bone and in the endosteum (marrow cavity).
• Differentiation requires constant supply of blood.
• Secrete alkaline phosphatase, collagenase, growth factors, collagen and osteocalcin.
Which cells do osteoblasts arise from?
Osteogenic cells
What is the periosteum?
The tissue that covers the superficial surface of bone
What do osteoblasts secrete?
Alkaline phosphatase Colleganase Growth factors Collagen Osteocalcin
Which cells mediate bone resorption through phagocytosis?
Osteoclasts
What are osteoclasts?
Osteoclasts are large multinucleated cells responsible for the dissolution and absorption of bone – mediators of bone destruction by phagocytosis.
Where do osteoclasts reside?
Within Howship Lacunae - caused by ther erosion of bone by osteoclast derived enzymes
How do osteoclasts mediate bone resorption?
- Ruffled border (invaginations of the plasma membrane) is formed by osteoclasts, which define the active region where acid phosphatase enzymes are secreted to dissolve the organic collagen and inorganic calcium & phosphate of the bone.
- Attach to the bone by osteopontin and sialoprotein forming a sealing zone between the osteoclast and bone.
- Calcium hydroxyapatite crystals are removed from the bone by acidification – the osteoid is protected against osteoclastic resorption.
How is calcium stored within bone?
As calcium hydroxyapetite crystals
What are the two main types of bone?
Immature woven bone (primary bone)
Mature bone
Which cells are predominantly found within immature woven bone?
Osteocytes
How are the collagen fibres organised within woven bone?
In a haphazard organisation
What is the first type of bone formed in embryonic development and fracture healing?
Primary bone - immature woven bone
What are the two forms of mature bone?
Cortical bone
Cancellous bone
Which type of bone ensheathes the bony medulla?
Cortical bone
How is cortical bone organised?
lamellar configuration
Densely arranged osteons (Haversian systems)
What is an osteon?
Contain a central canal that is surrounded by concentric rings (lamella) of the matrix
osteocytes located between lamellae within the small cavities -lacunae
Canaliculi radiate from the launcae to the Haversian canal to provide passageways through the hard matrix
How do the blood vessels interconnect within bone?
By Volkmann’s canal
How is cancellous bone organised?
Cancellous bone is characterised by a trabecular structure that is comparatively less dense, softer, weaker and less stiff than cortical bone.
Where does cancellous bone reside?
Within the epiphysis of the bone and within the medullary canal
What is the function of cancellous bone?
- Greater surface area is ideal for metabolic activity - exchange of calcium ions
- High vascular and red bone marrow support haemopoiesis.
What is the function of flat bones?
Protects internal organs
What type of bone is the cranial cavity?
Flat bone
What is the function of long bones?
Support and facilitate movement
What is the function of irregular bones?
Vary in shape and structure
What type of bone is the humerus?
Long bone
What is the function of short bones?
No diaphysis, as wide as they are long, provide stability and some movement
What is the function of sesamoid bones?
Embedded within the tendons potentially protects tendons from stress or wear
What type of bone is patella?
Sesamoid bone
What is the diaphysis?
A tubular shaft that traverses between the proximal and distal ends of the bone.
The hollow region within the diaphysis is considered to be the medullary cavity
What does the medullary cavity encapsulate?
Yellow marrow
What are the walls of the diaphysis composed of?
Dense and hard compact bone
What is the membranous lining of the medullary cavity?
Endosteum
What is the outer surface of the medullary cavity?
Periosteum
Where does the red marrow occupy?
The cavities of the trabeculae within the epiphysis
What is the epiphysis?
Wider terminal ends of bone that are filled with cancellous bone
What is the point at which the epiphysis meets the diaphysis?
Metaphysis
What is the metaphysis?
Narrow segments that contain the epiphyseal growth plates - a layer of hyaline in a growing bone
Which type of collagen forms the bone?
Type I bone (90%) and type V
What is intramembranous ossification?
- Mesenchymal cells undergo differentiation and specialises into osteogenic cells and ultimately osteoblasts. Clusters of osteoblasts form an ossification centre.
- Osteoblasts secrete osteoid, uncalcified matrix consists of collagen precursors and organic proteins which calcifies due to mineralisation – therefore entrapping osteoblasts.
- Osteoblasts that are entrapped within the matrix become osteocytes. As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue differentiate into osteoblasts at the edges of growing bone.
- Clusters of osteoid unite around capillaries Forms a trabecular matrix.
- Osteoblasts on the surface of newly formed spongy bone become the cellular layer of the periosteum. The periosteum secretes compact bone superficial to the cancellous bone.
- Cancellous bone aggregates near blood vessels condensing into red bone marrow.
What is endochondral ossification?
The bone develops through hyaline cartilage replacement - Behaving as a template to be completely replaced by new bone
Compare the rate at which intramembranous and endochondral ossification occur?
Endochondral ossification is longer than intramembranous ossification
What is the process of endochondral ossification?
- Formation of matrix increases cartilaginous model size – blood vessels in the perichondrium brings osteoblasts to the edges of the structure.
- Arriving osteoblasts deposit osteoid in concentric formation around the diaphysis. Bony edges of the developing structure prevent nutrients from diffusing into the centre of the hyaline cartilage Chondrocyte death.
- Periosteal bud invasion: Without cartilage inhibiting blood vessel invasion, blood vessels penetrate the resulting space – enlarging the cavities and transferring osteogenic cells with them – forming osteoblasts.
N.B: The enlarged spaces become the medullary cavity. - Chondrocytes and cartilage continue to grow at the epiphyses, increasing length. Continued growth is accompanied by remodelling inside the medullary cavity, and overall lengthening of the diaphysis.
- Cartilage remains at the epiphyses and at joint surfaces as articulate cartilage.
- Secondary ossification centre forms
Which factors are released from osteoblasts?
Osteoclast activating factor
What is the mechanostat theory?
A regulatory mechanism in bone that senses changes in mechanical demands exerted on it, and thus stimulating adjustments in its architecture to accommodate the habitual load.
• Below a certain threshold of mechanical use Bone is resorbed
• Above threshold Bone formation occurs.
Describe Wolff’s Law
States that bone grows and remodels in response to the forces that are exerted onto it. Placing stress in specific directions stimulate osteocyte activity.
What T score diagnoses osteoporosis?
Less than -2.5 on a DEXA scan
What are the three causes of bone disorders?
Postmenopausal
Senile
Secondary
What is Rickets/Osteomalacia?
- Vitamin D or calcium deficiency in children (Rickets) or adults (osteomalacia)
- Osteoid mineralises poorly and remains pliable.
- In rickets, the epiphyseal growth plates can become distorted under weight of the body.
- In osteomalacia, increased risk of fracture
What is osteogenesis imperfecta?
There is a reduction in type I collagen secretion. Collagen is an extracellular matrix protein secreted by fibroblast & osteoblasts. Collagen provides mechanical strength and rigidity to bone.
• Autosomal recessive/dominant condition.
• Increased fragility of bones, bone deformities and blue sclera.
• Can be mistaken as NAD in children – diagnosis is important medicolegally.
What are 4 criteria when categorising a fracture?
A fracture is a discontinuity of the bone and is defined by four factors:
- Orientation
- Transverse, oblique, spiral or comminated - Location
- Epiphysis, metaphysis, and diaphysis (proximal 1/3, middle 1/3 and distal 1/3) - Displacement
- Displaced and Undisplaced - Skin penetration
- Open or closed fractures
What is a transverse fracture ?
Occurs straight across the long axis of the bone
What is an oblique fracture?
Occurs at an able that is not perpendicular
What is a spiral fracture?
Bone segments are pulled apart as a result of twisting notion
What is a comminuted fracture?
Multiple breaks result in many small pieces between two large segments (simple fracture = 2 pieces)
What is an impacted fracture?
One fracture is driven into the other as a result of compression
What is a greenstick fracture?
Partial fracture in which one side of the bone is broken
What are the description classifications of fractures?
Garden, Schatzer, Neer, Wber
What is an open fracture?
A fracture in which at least one end of the bone penetrates the skin – presenting a potential risk of infection.
What is a closed fracture?
A fracture in which the skin remains intact
Which type of fracture is associated with soft tissue injury?
Tscherne (Closed), or Gustilo-Anderson (Open)
What is the universal fracture classification?
OTA classification
What is primary bone healing?
Intermembranous healing is associated with absolute stability.
• Osteoblasts move into fracture. In primary bone healing, the bone ends are in contact therefore the osteoblasts can traverse across and bone formation is accelerated, membrane forms.
• Membrane formation behaves as a conduit for osteoblasts to pass.
• Haversian remodelling occurs in circumstances that there is a little or no gap <500mm.
• Slow process using a cutter cone concept.
What are the phases of primary bone healing?
Inflammatory phase (Duration: Hours-Days)
• Broken bones result in disrupted blood vessels, thus the formation of a blood clot & haematoma. This elicits an inflammatory reaction which results in the release of cytokines, growth factors & prostaglandins.
• Fracture haematoma becomes organised & infiltrated by fibrovascular tissues Forms matrix for bone formation & primary callus.
Reparative phase (Duration: Days-weeks) • Thick mass callus formation around bone ends, from the fracture haematoma. Osteoblasts are recruited in order to deposit type-I collagen derived osteoid. • Thich mass callus is evident on radiographs within 7-10 days post-injury. • Soft callus remodelled Hard callus Soft callus: Plastic, easily deformed or bend, if the fracture is not adequately supported. Hard callus: Weaker in comparison to normal bone however has better capability to withstand external forces and equates to the stage of clinical union.
Remodelling phase (Duration: Months-years)
• Longest phase.
• During remodelling, the healed fracture and surrounding callus responds to activity, external forces, functional demands and growth (Wolf’s law).
• The external callus is no longer needed and is therefore removed through osteoclast activity, and fracture site is smoothed & sculpted.
• Epiphyses realign and residual angulation corrected.
What happens during the inflammatory phase?
- Broken bones result in disrupted blood vessels, thus the formation of a blood clot & haematoma. This elicits an inflammatory reaction which results in the release of cytokines, growth factors & prostaglandins.
- Fracture haematoma becomes organised & infiltrated by fibrovascular tissues Forms matrix for bone formation & primary callus.
What happens during the reparative phase?
• Thick mass callus formation around bone ends, from the fracture haematoma. Osteoblasts are recruited in order to deposit type-I collagen derived osteoid.
• Thich mass callus is evident on radiographs within 7-10 days post-injury.
• Soft callus remodelled Hard callus
Soft callus: Plastic, easily deformed or bend, if the fracture is not adequately supported.
Hard callus: Weaker in comparison to normal bone however has better capability to withstand external forces and equates to the stage of clinical union.
What happens during the remodelling phase?
- Longest phase.
- During remodelling, the healed fracture and surrounding callus responds to activity, external forces, functional demands and growth (Wolf’s law).
- The external callus is no longer needed and is therefore removed through osteoclast activity, and fracture site is smoothed & sculpted.
- Epiphyses realign and residual angulation corrected.
What is secondary bone healing?
• Fast process resulting in callus formation (fibrocartilage).
Step I (Week 1): Bleeding/haematoma Prostaglandin/cytokine released; growth factors increase local blood flow Periosteal supply dominates.
Step II (Week 2-4): Granulation (Connective/fibrotic) tissue deposited Soft callus formation (Type-II collagen Cartilage; fibroblasts woven blood (immature bone)).
Step III (1-4 months): Fracture is bridged with soft callus Hard callus formation succeeds (Laying down of osteoid Type I collagen) facilitated by increased osteoblast activity.
Step IV (4-12 months): Bone is remodelled through endochondral ossification, lamellar bone in its place. Callus responds to activity, external forces and the functional demands exerted onto the bone. • Balance of osteoclast and osteoblast activity to remodel bone (removal of excess).
N.B: Haematoma Soft callus Hard callus Remodelling (endochondral ossification).
What is the pre-requisite for healing?
- Minimal fracture gap
- No movement if direct (primary) bone healing or minimal movement if indirect (secondary) bone healing.
- Consider patients physiological state – nutrients, growth factors, age, diabetic, smoker.
What non-union fracture?
Failure of bone healing within an expected time frame
What is atrophic healing complications?
Healing completely ceased with no X-rays changes
What is hypertrophic healing complications?
Excessive movement can facilitate hard callus formation (Secondary bone healing in response to sustained stimuli on the bone)
What is pseudoarthrosis?
A joint fibrocartilage capsule is formed due to a non-union fracture, the two fragments of bone of a fracture have not united.
What is malunion?
Bone healing occurs but outside of the normal parameters of alignment.
What is reduce?
Reduction involves restoring the anatomical alignment of a fracture or dislocation of the deformed limb
The main principle is to correct the deforming forces - that resulted in the injury
What is a non-cast traction?
- Essential for long bone fractures including the femur and humerus.
- Adhesive dressing is applied over the fracture site, and weights are added; this pulls on the fractured bone using pulleys, applying a tensive and gravitational force – Straightens position and aligns end.
- Can provide immediate relief.
What is the conservative method of treatment for a fracture?
Hold describes fracture immobilisation – consider whether traction is required, whereby the muscular pull across the fracture site is strong, and the fracture is inherently unstable.
• Plaster casts and simple splints are employed to immobilise fracture.
• Provide overlying dress to enable fracture to swell, otherwise there is a risk of the patient developing compartment syndrome.
• In acute injury, individuals swell, where a circumferential definitive cast, the site of fracture will swell within a confined area Limiting capacity for blood flow.
What is the treatment for a displaced intra-capsular fractures?
- Total hip replacement -The femoral head and acetabulum is replaced.
- Hemi-arthroplasty – The head of femur is replaced by a prosthesis
