Bone Growth Flashcards
Describe the state of the ossification centres in a long bone at birth.
When does bone growth stop?
Describe the mechanism by which bone stops growing.
- Growth in height ceases at the end of puberty.
- Sex steroids stimulate a growth spurt but promote closure of the epiphyseal plates.
- Growth in length ceases, cell proliferation slows and the plate thins.
- The plate is invaded by blood vessels, epiphyseal and diaphyseal vessels unite.
- May leave a visible line on X-rays.
Give examples of bones with only one ossification centre.
- Carpals
- Tarsals
- Ear ossicles
How many ossification centres does the head of the humerus have?
3
Name each of the zones of this epiphyseal plate.
What is the function of the resting zone of the epiphyseal plate?
Give an example of a disease which can affect this zone.
- Function = matrix production.
- Diastrophic dysplasia causes defective collagen synthesis / processing of proteoglycans.
What is the function of the growth zone of the epiphyseal plate?
Give an example of a disease which can affect this zone.
- Function = cell proliferation.
- Achondroplasia, malnutrition or irradiation injury would all cause deficiency in cell proliferation and / or matrix synthesis.
- Gigantism would cause increased cell proliferation.
What is the function of the hypertrophic zone of the epiphyseal plate?
Give an example of a disease which can affect this zone.
- Function = calcification of the matrix.
- Rickets would cause insufficiency of calcium or phosphate for normal calcification.
What is the function of the metaphysis zone of the epiphyseal plate?
Give an example of a disease which can affect this zone.
- Functions = bone formation and vascularisation.
- Osteomyelitis could be caused by a bacterial infection.
- Osteogenesis imperfecta is an abnormality of osteoblasts and collagen synthesis.
- Scurvy causes inadequate collagen turnover.
Describe the effects of achondroplasia on the epiphyseal growth plate.
Describe the effects of rickets on the epiphyseal growth plate.
What are the substances required for normal bone growth?
- Calcium
- Phosphorus
- Vitamins A, C and D
- Balance between growth hormone, thyroid and parathyroid hormones, oestrogen and androgens.
- Abnormalities of these can affect bone growth; also effects on fracture healing.
What are the different mechanisms of injury in a fracture?
-
Direction of force:
- Direct vs angular
- Rotational
- Compression
-
Energy transfer
- Cause
- Site
How do you describe a fracture?
- Site
- Open to surface
- Contaminated
- Associated soft tissue injury
- Joint involvement
- Number of pieces
- Alignment
- Degree of separation
What is the definition of a fracture?
A complete or incomplete break in a bone
Which type of fracture pattern is depicted?
Transverse
Which type of fracture pattern is depicted?
Linear
Which type of fracture pattern is depicted?
Oblique non-displaced
Which type of fracture pattern is depicted?
Oblique displaced
Which type of fracture pattern is depicted?
Spiral
Which type of fracture pattern is depicted?
Greenstick
Which type of fracture pattern is depicted?
Comminuted
What is an avulsion fracture?
A fragment of bone is separated from the main mass.
What is a buckled fracture?
- AKA impacted fracture; torus fracture.
- Ends are drived into each other.
- Commonly seen in arm fractures in children.
What is a pathologic fracture?
A fracture caused by a disease that weakens the bones.
What is a stress fracture?
A hairline crack in a bone.
How does bone heal after a fracture?
- Depends on the activity of the cells of the periosteum.
- ‘Bone remodelling units’:
- Consists of osteoclasts and osteoblasts
- Keep adult bone mass relatively constant in the face of developmental, physiological and physical demands.
- Bone has a remarkable capacity to heal well, unlike articular cartilage.
- Fracture healing depends on the activity of osteoblasts in the local periosteum.
- Takes 2-20 weks for healing, depending on:
- Severity of fracture
- Age of patient
There are 3 major phses of fracture healing.
Describe the 1st phase.
- Reactive phase
- Fracture and inflammatory phase (haematoma).
- Fibroblasts in the periosteum proliferate to form granulation tissue around the fracture site.
There are 3 major phses of fracture healing.
Describe the 2nd phase.
-
Reparative phase
- Callus formation - osteoblasts quickly form woven bone, to bridge the gap.
- Woven bone is weak as the collagen fibres are arranged irregularly.
- Lamellar bone is laid down - collagen is organised in regular sheets to give strength and resilience.
There are 3 major phses of fracture healing.
Describe the 3rd phase.
- Remodelling phase
- Remodelling by osteoclasts to restore original bone shape.
Describe non-union fractures.
What are the risk factors for non-union fractures?
- Complete cessation of reparative processes of bone healing.
- Overall risk est. 1.9-4.9%
- Tibial risk reported as high as 23%
- Atrophic - inadequate biological factors.
- Hypertrophic - excessive callus formation outwith the fracture site.
What is the conservative treatment for fractures?
- Indicated in simple fractures with low risk of non-union.
- Dependent on natural healing process.
- +/- immobilisation
- Rehabilitation
What are the indications for intervention in fracture treatment?
- Fractures with limb threat or risk of non-union.
- Augment natural healing with replacement or strengthening.
- +/- immobilisation
- Rehabilitation
What are the types of osteoconductive scaffolding which can be used in the treatment of fractures?
- Autologous bone graft
- Often from iliac crests
- Allografts
- Cadaveric
- Synthetic
- Hydroxyapatite
- Collagen
What are the other treatments with the potential to help heal fractures?
- Inducing mechanical strain
- Shockwaves and low-intensity ultrasound
- Growth factors and pharmacological interventions:
- Parathyroid hormone
- Bone morphogenic proteins
- Anti-sclerostin abs
- Statins
- Dasatinib
