Bone Growth and Fractures Flashcards
what is the role of sex steroids in bone growth?
stimulate bone growth spurt but promote close of epiphyseal plates
what happens to bone growth at end of puberty?
- growth in length ceases
- cell proliferation slows and plate thins
- plate invaded by blood vessels
- epiphyseal and diaphyseal vessels unite
- may leave visible line on x-rays
which bones have only one ossification centre?
- carpals
- tarsals
- ear ossicles
which bones have 2+ ossification centres?
head of humerus has 3
what are the zones of the epiphyseal plate?
- ossification (osteogenic)
- calcification
- hypertrophic
- growth (proliferation)
- resting zone
what is the function of the resting zone?
matrix production
what is the function of the growth zone?
cell proliferation
what is the function of the hypertrophic zone?
calcification of matrix
what is the function of the metaphysis zone?
- bone formation
- vascularisation
what are examples of diseases due to defects in resting zone?
diastrophic dwarfism:
- defective collagen synthesis/processing of proteoglycans
what are examples of diseases due to defects in growth zone?
achondroplasia; malnutrition; irradiation injury:
- deficiency in cell proliferation and/or matrix synthesis
gigantism:
- increased cell proliferation
what are examples of diseases due to defects in hypertrophic zone?
rickets; osteomalacia:
- insufficiency of calcium or phosphate for normal calcification
what are examples of diseases due to defects in metaphysis zone?
osteomyelitis:
- bacterial infection
osteogenesis imperfecta:
- abnormality
scurvy:
- inadequate collagen turnover
what are the requirements of normal growth and bone development?
- calcium
- phosphorus
- vitamin A, C, D
- balance between growth hormone, thyroid/parathyroid, oestrogen/androgens
what is the ratio of cortical/compact bone to cancellous/trabecular bone?
8:2
what is the location of cortical/compact bone?
shaft of long bones
what is the location of cancellous/trabecular bone?
- ends of long bones
- vertical bodies
- flat bones
what is the structure of cortical/compact bone?
concentrically arranged lamellae - haversian systems
what is the structure of cancellous/trabecular bone?
meshwork of trabeculae with intercommunicating spaces
what is the function of cortical/compact bone?
mechanically strong
what is the function of cancellous/trabecular bone?
metabolic
what is turnover like in cortical/compact bone?
slow
what is the turnover like in cancellous/trabecular bone?
fast
what is the periosteum like in cortical/compact bone?
thick
what is the periosteum like in cancellous/trabecular bone?
thin
what is blood supply like in cortical/compact bone?
slow
what is blood supply like in cancellous/trabecular bone?
rich
what is the fracture pattern of cortical/compact bone?
direct or indirect violence may result in deficits at the fracture site leading to non-union
what is the fracture pattern of cancellous/trabecular bone?
honeycomb structure fails as the result of compression ( e.g. fall from height compacts bone)
what information does x-ray imaging provide?
- site and bones involved
- clues on soft tissue injury
- clues on energy transfer e.g wide displacement, comminuted, multiple fracture sites
what is a fracture?
a complete or incomplete break in a bone
what ways are there to describe a fracture?
- site
- open to surface
- contaminated
- associated soft tissue injury
- joint involvement
- number of pieces
- alignment
- degree of separation
what are some types of fracture patterns?
- transverse
- linear
- oblique non-displaced
- oblique displaced
- spiral
- greenstick
- comminuted
avulsion fracture
a fragment of bone is separated from main mass
buckle fracture
- a.k.a impacted fractur, torus fracture
- ends are driven into each other
- commonly seen in arm fracture in children
compression or wedge fracture
usually involves vertebrae
pathological fracture
caused by a disease that weakens the bones
stress fracture
a hairline crack
what types of fracture are limb threatening/non-union risk?
- dislocation
- comminuted
- compound
- compartment syndrome
- vascular/nerve injury
- significant soft tissue injury
- pathological bone
what are the 3 major phases of fracture healing?
- reactive phase
- reparative phase
- remodelling phase
what is involved in the reactive phase of fracture healing?
- fracture and inflammatory phase (haematoma)
- fibroblasts in periosteum proliferate to form granulation tissue around fracture site
what is involved in the reparative phase of fracture healing?
- callus formation: osteoblasts quickly form woven bone to bridge gap
- woven bone is weak as collagen fibres arranged irregularly
- lamellar bone laid down, collagen organised in regular sheets to give strength and resilience
what is involved in the remodelling phase of fracture healing?
remodelling by osteoclasts to restore original bone shape
when are conservative forms of fracture treatment used?
simple fracture with low risk of non-union:
- dependent on natural healing process
- +/- immobilisation
- rehabilitation
when are forms of intervention treatment used for fractures?
fractures with limb threat or risk on non-union:
- augment natural healing with replacement of strengthening
- +/- immobilisation
- rehabilitation