osteoporosis Flashcards
definition of osteoporosis
reduced bone density (<2.5 standard deviations below beak bone mass achieved by health adults, ie T score of
resulting in bone fragility and increased fracture risk
osteopenia is a T score between -1 and -2.5
aetiology of osteoporosis
primary - idiopathic (<50yrs), post-menopausal
secondary:
- malignancy - myeloma, met carcinoma
- endocrine - cushings, thyrotoxicosis, hyperPTH, hypogonadism
- drugs - corticosteroids, heparin
- rheumatological - RA, ankolysing spondylitis
- GI - malabsorption syndromes (eg coeliac, partial gastrectomy), liver disease (primary biliary cirrhosis), anorexia
RF for osteoporosis
age
FH
low BMI
low ca intake
smoking
lack of physical exercise
low exposure to sunlight
alcohol abuse
late menarche
early menopause, untreated
hypogonadism
prolongued immobility
pneumonic for osteoporosis RF
SHATTERED
steroid use >5mg/d prednisolone
hyperthyroidism, hyperPTH, hypercalciuria
Alcohol and tobacco
Thin
testosterone low (eg antiandrogen ca prostate treatment)
early menopause
renal or luver failure
erosive/IBD - myeloma, RA
diet - low Ca, malabsorption, t1dm
epidemiology of osteoporosis
common
in >50yr - 1/3 women, 1/12 men
women lose trabeculae with age
men - reduced bone formation but numbers of trabeculae are stable and lifetime risjk of fracture is less
causes >200000 fractures annually in UK (especially hip)
more in caucasians, than afrocaribbeans
symptoms of osteoporosis
asymptomatic until characteristic fractures
femoral neck fractures if cortical bone affected - commonly after minimal trauma
vertebral fractures - loss of height or stooped bosture, or acute back pain in lifting
colles’ fracture of the distal radius afte rfall onto outstretched hand
signs of osteoporosis
none until complications
tenderness on percussion over vertebral fractures
thoracic kyphosis if multiple vertebral fractures
severe pain with leg shortened and externally rotated - in femoral neck fracture
classes of investigation for osteoporosis
bloods
XR
isotope bone scans
bone densitometry (dueal-energy XR absorptiometry)
biopsy - unreliable and unnecessary
bloods for osteoporosis
Ca PH4 3- and AlkPhos are normal in primary (unless a result of secondary causes)
XR for osteoporosis
diagnose fractures when symptomatic
often normal (>30% loss in density before show radiolucency, abnormal trabeculae or cortical thinning)
biconcave vertebrae
crush fractures - if trabecular bone is affected
isotope bone scans for osteoporosis
highlight stress or microfractures - not commonly used
bone densitometry for osteoporosis
DEXA
obtain T and Z score of bone density
T score - number of SD the BMD measurement is above or below the young normal mean BMD. Used to define osteoporosis
Z score - number of SD the measurement is above or below the age matched mean BMD. May be useful on identifying pts who need a work up for secondary causes of osteoporosis
scan hip, better than lumbar spine
each decrease of 1SD = 2.6fold increase in risk of hip fracture
indications for DEXA
previous low trauma fracture, or women >=65yrs with 1 or more RF, or younger iof 2 or more RF
not needed pre-treatment for women >75yrs if previous low trauma fracture or >=2 of RA, alcohol, FH
prior to steroids long term
osteopenia if low trauma, non-vertebral fracture
bone and remodelling disorders - eg parathyroid disorders, myeloma, HIV esp if on protease inhibitors
how do steroids cause osteoporosis
promote osteoclast bone resorption
reduced muscle mass
reduced ca absorption from the gut
mx of osteoporosis in post-menopausal women
- bisphosphonate (alendronic acid) for post-menopausal women
- Ca and vit D supplementations
- Denosumab - monoclonal antibody that inhibits osteoclast formation
- parathyroid hormone receptor agonist
if not tolerated - Selective oestrogen receptor modulator, or HRT
exercise
