Bone Disorders Flashcards
what is osteoporosis
progressive systemic skeletal disease characterised by low bone mass and micro architectural deterioration of bone tissue with subsequent increase in bone fragility and susceptibility to fracture
where does bone remodelling occur
at bone remodelling units
what is the process of bone remodelling
osteoclasts resorb the bone
osteoclasts are replaced by osteoblasts which fill the cavity by putting down osteoid that is mineralised to form new bone
what causes osteoporosis
relative or absolute increase in resorption over formation that leads to bone loss (more osteoclast than blast activity)
what architechtural changes occur in osteoporosis
decrease in trabecular thickness and connections between vertical trabeculae
what causes peak bone mass
genetics, body weight, sex hormones, diet, exercise
what causes bone loss
sex hormone deficiency body weight genetics diet immobility diseases drugs- glucocorticoids, aromatase inhibitors
how do the dexa scans work
compares your bone score with what is should have been at its best as with average for young adult reference
what are the parameters for DEXA scans
Normal : BMD within 1 SD of the young adult reference mean
Osteopenia (low bone mass) :BMD >1 SD below the young adult mean but <2.5 SD below this value
Osteoporosis : BMD ≥ 2.5 SD below the young adult mean
Severe osteoporosis : BMD ≥2.5 SD below the young adult mean with fragility fracture
who should get dexa scans
patients over 50 with low trauma fracture
what are the modifiable risk factors for fragility fractures
BMD Alcohol Weight Smoking Physical inactivity Pharmacological risk factors
what are the secondary causes of low bone density
Endocrine e.g. hyperthyroidism, hyperparathyroidism, Cushing’s disease
Gastrointestinal e.g. coeliac disease, IBD, chronic liver disease, chronic pancreatitis
Respiratory e.g. CF, COPD
Chronic kidney disease
what is the lifestyle advice for osteoporosis
High intensity strength training Low-impact weight-bearing exercise (standing, one foot always on the floor) Avoidance of excess alcohol Avoidance of smoking Fall prevention
what are the dietary sources of calcium
dairy bread and cereals fish with bones nuts green veg beans
what are the drug treatments for osteoporosis
Calcium & vitamin D supplementation
Bisphosphonates
Denosumab
Teriparatide
HRT
SERMS (Selective Estrogen Receptor Modulators)
Testosterone (hypogonadism in a younger man)
what are bisphosphonates
ant resorbtive agents
what is denosumab
monoclonal antibody that targets and binds with high affinity and specificity to RANKL (receptor activator of nuclear factor-kB ligand)- inhibits the development and activity of osteoclasts
how do corticosteroids cause a decrease in bone density
Reduction of osteoblast activity and lifespan
Suppression of replication of osteoblast precursors
Reduction in calcium absorption
Inhibition of gonadal and adrenal steroid production
what is pagets disease
abnormal osteoclastic activity followed by increased osteoblastic activity - abnormal bone structure with reduced strength and increased fracture risk
what bones are commonly affected by pagets
long bones, pelvis, lumbar spine and skull (can cause hearing loss)
how does pagets present
bone pain, deformity, deafness, compression neuropathies
what cancer is a rare complication of pagets
osteosarcoma
what are the findings of pagets
isotope bone scan
raised alk phos
normal LFTs
what is the treatment for pagets
bisphosphonates if pain not responding to analgesia
how can you FEEL if pagets is active
feels hot
what is osteogenesis imperfecta
genetic conditions affect bone
what mutations cause oestogenesis imperfecta
mutations of type 1 collagen genes (COL1A1, COL1A2)
autosomal dominant
what signs can osteogenesis imperfecta be associated with
blue sclera and dentinogenesis imperfecta
what is the treatment for osteogenesis imperfecta
no cure –only fracture fixation, surgery to correct deformities, bisphosphonates
what is the T score in dexa scans
deviation away from young adult mean
what is the Z score in dexa scans
score that is age matched
why is vitamin D important
need it to absorb calcium
what are the signs of vitamin D deficiency
bony pain, muscle weakness, proximal myopathy
what hormones are found in primary hyperparathyroidism
high PTH
high alk phos
high bilirubin
hypercalcaemic
high calcium should suppress PTH, will have endogenous production of PTH- e.g. thyroid adenoma
what symptoms in hyperparathyroidism
osteoporosis) Kidney stones. Excessive urination and thirst. Abdominal pain. Tiring easily or weakness. Depression or forgetfulness. Bone and joint pain.
what cancers metastasise to bone
breast, bowel, bronchus (lung), renal, prostate
what biochem would be seen in bone metastasis
calcium high
PTH will be low, appropriate suppression by high calcium
If PTH was high might be PTHrp being released by the tumour
what medication to bring down calcium
bisphonphonates
what is seen on x ray
cortico thickening, coarse trabecular patterning
when is alk phos raised on its own
pagets
high alk phos + pain =
pagets
