The case of the Crumbling Spine Flashcards
Fragility fracture?
Fragility fracture
fracture caused by fall from standing height or less or spontaneous
Causes of Fragility Fractures (4)
reduced bone mineral density
altered bone architecture
changed bone material properties
treatment non-adherence
how do we measure bone mineral density?
how do we measure bone mineral density? bone densitometry (DEXA)
how do we evaluate bone architecture?
how do we evaluate bone architecture?
trabecular bone score
high res peripheral CT
what bone materials can change causing fragility fractures?
type 1 collagen
hydroxyapatite crystals
what bone materials can change causing fragility fractures?
get advanced glycation end products which can damage collagen
how can collagen be linked to fragility fractures?
mutations causing not enough or abnormal collagen
Bone remodelling cycle
Quiescence, resorption, reversal, formation
osteoclast action
resorption of bone
How are osteoblasts activated?
growth factors are released by osteoclasts
how do oestoblasts and osteoclasts change in menopause?
osteoclasts become more active than osteoblasts
How are osteoclasts activated?
RANKL from osteoblasts binds and causes osteoclast precursors to mature
Osteoprotegerin (OPG)
decoy receptor
blocks binding of RANK to RANK-L > reduces osteoclast differentiation
increases bone density
How does menopause cause osteoporosis?
reduced oestrogen causes reduced Osteoprotegerin expression
osteoclasts more active
mechanism of demosumab
decoy receptor for RANKL, mimics action of OPG
how is demosumab administered?
6 monthly injection
sclerostin
Made by osteocytes and suppresses bone formation
Wnt pathway in osteoporosis
canonical wnt pathway enhances osteoblast differentiation, upregulates OPG and down regulates RANKL
mechanism of romosozumab
antisclerostin antibody so enables Wnt system to remain active
get bone rebuilding
2 monoclonal antibodies used in the treatment of osteoporosis
denosumab
romosozumab
grancalcin
a protein that represses osteogenesis
what secretes grancalcin?
senescent immune cells
Osteoporosis
disorder of bone characterised by low bone mass and microarchitectural deterioration, increased fracture risk
primary osteoporosis type 1
postmenopausal, accelerated decrease in bone mass that occurs when estrogen falls
primary osteoporosis type 2
senile
affects men and women>70 yo
Primary osteoporosis T1 vs T2
postmenopausal, accelerated decrease in bone mass that occurs when estrogen falls = t1
senile
affects men and women>70 yo = t2
which sex suffer from primary osteoporosis more?
females
secondary osteoporosis
conditions in which bone is lost because of the presence of another disease, such as rheumatoid arthritis or certain drug use
what drugs cause secondary osteoporosis?
steroids aromatase inhibitors anti-epileptics thyroxine proton pump inhibitors
what determines bone mass?
- heredity
- nutrition
- exercise
- hormone function
DEXA
dual-energy x-ray absorptiometry
which sites does DEXA image?
lumbar spine
hip
right forearm
when do you DEXA scan right forearm?
in hyperparathyroidism or non-diagnostic spine/hip
How does DEXA work?
measures bone density based on how easily low dose x-rays go through the bone
T score
Standard deviation between BMD and that of a young healthy adult (30?)
Z score
standard deviation between BMD and that of someone the same age
what factors do the T and Z scores take into account?
gender and ethnicity
normal T score for post menopausal women or men over 50
equal or greater than -1
What T score shows osteoporosis?
equal or below -2.5
what T score shows osteopenia?
what T score shows osteopenia?
between -1 and -2.5
what does a Z score of below -2 mean?
BMD lower than it should be for someone age matched
which score out of the sites imaged should you use for diagnostic purposes?
lowest score out of total spine, total hip, NOF or total forearm
which DEXA score do you use for premenopausal women or men under 50?
Z score only
FRAX
Fracture risk assessment tool developed by WHO
what does FRAX use?
femoral neck BMD score
clinical risk factors e.g. age, steroid use, height
what does FRAX calculate?
10yr risk of osteoporotic fracture
do people under 50 need a low BMD for diagnosis of osteoporosis?
no, can give diagnosis if they have a fragility fracture regardless
cortical bone
dense outer bone, strength determined by thickness and porosity
trabecular bone
interior, spongy bone with a porous, honeycomb structure, strength determined by thickness, lattice number and porosity
trabecular bone score
from textural analysis of DEXA
independent fracture risk assessment
can the same BMD score have a different trabecular bone score?
yes
HR-pQCT
research tool that does high res CT of wrist and ankles, looks at volume of bone
what does osteoporosis look like on X-ray?
cortical thinning/increased radiolucency
pencilling of vertebrae
osteoporosis x-ray
the time abnormalities defected by X-ray 25-30 % of bone tissue may have been lost
interventional radiology - what is it?
image guided diagnostic or therapeutic procedures achieved through percutaneous puncture of a vessel or organ
examples of IR
iliac angioplasty
interventional oncology
visceral embolisation
stenting
what are most preventable deaths from trauma caused by?
unrecognised haemorrhage, especially abdomen
aortic transection
Injury to the aorta consisting of laceration of all 3 layers of the vessel wall
Sign of aortic transection
aortic transection
fatality rates in aortic transection
30% fatal within 6hrs, 40% in 24hrs
what can you repair aortic transection with?
Dacron graft
how can a fracture cause limb ischaemia?
how can a fracture cause limb ischaemia?
oedema or bone compresses artery causing ischaemia
examples of embolic agents
coils
cyanoacrylate glue
temporary gelatin sponge
Grades of renal trauma
TACE interventional oncology
high dose chemo straight into tumour via arteries which feed them
radiofrequency ablation
thin needle in core of tumor extends prongs, these are heated and cook tumour
optimum tumour size for radio frequency ablation
2cm
cryoablation
removing tumours with liquid nitrogen causing cell apoptosis
