disorders of bone health including osteopersosis Flashcards
what is osteoporosis?
-progressive systemic skeletal disease characterised by low bone mass and micro architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture
where does the bone remodelling cycle occur?
-at distinct sites called bone remodelling units
what process contributes to calcium homeostasis and skeletal repair?
the continual bone remodelling cycle
what are the 3 main types of bone cells?
- osteoclasts
- osteoblasts
- osteocytes
what are osteoclasts?
-multinucleated cells responsible for bone reabsorption, derived from haematopoietic progenitors
what are osteoblasts?
-mononucleated cells derived from mesenchymal cells in the bone marrow stroma, responsible for bone formation
what are osteocytes?
-primary cell of mature bone and most common type of bone cell, derived from the osteoblasts which become buried in bone matrix
what are the three phases of bone remodelling in a bone remodelling unit?
- resting phase
- active bone resorption
- bone formation
what bone cell is responsible for active bone resorption?
osteoclasts
C=cut
what is bone resorption?
-destruction of bone tissue, promoting bone loss
what bone cell is responsible for bone formation?
-osteoblasts
B=build
describe the bone microarchitecture at a healthy 20 year old
- good strong trabecular
- healthy bone
describe the bone microarchitecture of a 50 year old
-decrease in trabecular thickness which is more pronounced for non load-bearing horizontal trabeculae
describe the bone microarchitecture of a 50 year old
-decrease in
describe bone microarchitecture in 80 years?
-decrease in number of connections between vertical trabeculae which causes a decrease in trabeculae strength
what are bone trabeculae?
-highly porous forms of bone tissue that are organised into a network of interconnected rods and plates
what occurs to the tubercular in osteoporotic bone?
-they’re a lot weaker and there’s breaks between them
what factors can lead to bone loss?
- sex hormone deficiency
- changes in body weight
- genetics
- diet
- immobility
- disease
- drugs especially glucocorticoids and aromatase inhibitors
what are some non-modifiable risks of a fragility fracture?
- age
- gender
- ethnicity
- previous fracture
- family history
- menopause <45
what are some modifiable risks of a fragility fracture?
- BMD
- alcohol
- weight
- smoking
- physical inactivity
- drugs
what is used to determine fracture risk?
QFracture score
who would you do a risk factor assessment on?
> 50 with risk factors
<50 with very stron clinical factors:
- early menopause
- glucocorticoids
when to refer for DXA (dual energy Xray)?
-patients >50 years with low trauma fracture
- patients at increased risk of fracture based on risk factures (calculated using risk essessment tool e.g. FRAX or Q fracture)
- this would have to be >10% risk of fracture over 10 years
what is the most widely used method of measuring bone mass density?
DEXA scans
what is the T score?
way of measuring risk of osteoperosis
-compare the patients BMD with an estimate of what their BMD would’ve been when they were a young adult (at peak bone density)
what is a normal BMD?
within 1 SD (standard deviation) of the young adult reference mean
what would be classed as osteopenia (low bone mass)?
BMD> 1 SD below the young adult meant but <2.5 SD below this value
what would be classed as osteoporosis?
BMD> or equal to 2.5 SD below the young adult mean
what would be classed as severe osteoporosis?
BMD equal to or over 2.5 SD below the young adult mean fragility with fragility fracture
what is used to class BMD if a patient is <20?
Z score report
what is the Z score?
the average bone density of an aged match group of patients
used in patients <20
what is the relationship between T score and risk of fracture?
- for every additional SD below normal there is a doubling of fracture risk
- As the T score increases the fracture risk increases
what are some endocrine secondary causes of osteoporosis?
- hyperthyroidism
- hyperparathyroidism
- cushings disease
what are some GI secondary causes of osteoperosis?
- coeliac
- IBD
- chronic liver disease
- chronic pancreatitic
what are some resp secondary causes of osteoperosis?
- CF
- COPD
what are some renal secondary causes of osteoperosis?
-chronic kidney disease
what investigations are done for a patient with suspected osteoperosis?
- U + Es
- LFTs
- FBC
- PV
- TSH levels
- bone biochemistry
what is some lifestyle advice for patients diagnosed with osteoporosis?
- High intensity strenght training
- low impact weight bearing excercise (standing, one foot always on floor)
- avoid of excess alcohol
- smoking cessation
- fall prevention
what is some diet advice for patients with osteoporosis?
- 700mg of calcium (2-3 portions from milk and dairy food groups)
- post menopausal women aim dietary intake 1000mg calcium per (3-4 portion calcium rich foods)
- bread and cereal
- fish with bones
- nuts
- green vegetables
- beans
what is the drug treatment for osteoperosis?
- calcium and vitamin D
- biphsophonates= 1st line
- denosumab
- teriparatide
- romosozumab
- HRT
- SERMs (selective estrogen receptor modulators)
- testosterone
when is osteoporosis treated?
-majority of patients, consider treatment with antiresorptive therapy when T score /=7.5mg prednisolone for 3 months or more if there is a prevalent vertebral fracture, consider treatment with T score
what drug is used if patients are intolerant to biphosphonates or are high risk?
- Zoledronic Acid (given IV infusion for 3 years)
- Denosumab
what are the side effects of donsumab?
- hypocalcaemia
- eczema
- cellulitis
when is donsumab contraindicated?
severe renal impairement
when is Teriparatide recommended?
-patients with most severe osteoperosis especially patients with non trauma vertebral fractures in postmenapausal women
when is romosozumab recommended?
recommended for postmenopausal women with severe osteoporosis who have had a fragility fracture and are at imminent risk of further fracture (24 months)
what are the direct effects that corticosteroids have on bone?
- reduction of osteoblast activity and lifespan
- suppression of replication of osteoblasts precursors
- reduction in calcium absorptions
what is an indirect effect of corticosteroids and bone?
-inhibition of gonadal and adrenal steroid production
what is Paget’s disease?
- abnormal osteoclastic activity followed by increase osteoblastic activity
- abnormal bone structure with reduced strength and increased fracture risk
what bones does Paget’s usually affect?
- long bones
- pelvis
- lumbar spine
- skull
