Osteoporosis - Dushan Atkinson 26/5/2005
Osteoporosis is “a systemic skeletal disease characterised by low bone mass and microarchitectural deterioration with a consequent increase in bone fragility with susceptibility to fracture”(Consensus on OP Am J Med 2000 109:324-326)
1.2 million women in the
Up to 40% of women and 13% of men will have an osteoporotic # in their lifetime
50% of hip fracture patients will have long-term disability and 25% will require long-term nursing home care. 14,000 annual deaths from hip # in
With an aging world population Osteoporotic Fractures expected to become an epidemic, rising from1.66 million in 1990 to 6.26 million by 2050 (Gullberg
Osteoporosis Int. 1997; 7:407-413)
BMD (Bone mineral density)
gives an indication of bone strength.
DEXA
(Dual energy Xray absorptiometry – 2 different xray energies) gold standard at present
Preferred site is
BMD at the hip
(most likely to predict #, esp hip fracture) (
www.rcplondon.ac.uk/pubs/online_home
)
Also Check Hb, ESR, serum Ca, TFT, creatinine. Look for underlying cause
A BMD T-score compares to the mean value of the same-sex healthy young adult’s, expressed as standard deviations (Z-score is age-matched). WHO definition of
Osteoporosis is a Tscore of less than -2.5
(osteopenia is T-score –1
to –2.5)
When assessing response totreatment, BMD of vertebra is best, as spine is the most responsive site! (RCP,college guidelines
www.rcplondon.ac.uk/pubs/online_home
)
- However BMD has fairly low sensitivity and specificity. If you use BMD for selecting patients for prophylactic treatment using a T-score of -2.5, you may be
missing out on 60%
of those patients who are actually at risk.
- Others suggest that in patients with a
prior fracture
, a low BMD
predicts
the likelihood of new fracture (Gardsell et al 1989 Calcif Tissue Int
45:327-30)
- Possibility that having a previous fracture is a better predictor for further fracture (Wallace WA 1990 Current research in osteoporosis and bone mineral measurement, Br Inst Radiol:61)
- Patients with
one osteoporotic # run increased risk of another fracture often within one year
. (Klotzbuecher JBone Miner Res 2000 15:721-39 meta-analysis)
New techniques such as peripheral
Quantitative CT
scanning (QCT) testing bone structure,geometry and strength.
No difference in accuracy(94%)
Spinal QCT has benefit inability to detect changes in trabecular bone structure, microfractures,separately from cortical bone
- CT 10 mins c/w 30 mins
- CT less confounding from osteophytes
- DEXA lower radiation
- DEXA gives also total body bone density
Bonnick SL. Bone densitometry in clinical practice: application and interpretation.
Ultrasound is currently being investigated, and not as yet proven
RISK FACTORS
(and those in whom one considers BMD measurement) - RCPguidelines
X-ray evidence of osteopenia or vertebral fracture
Decrease in height
Previous low-impact/fragility fracture
Long-term steroid (>7.5mg for > 6 months)
Menopause earlier than 45 years
History of amenorrhoea for more than one year
Primary hypogonadism
Chronic disorders ass/wi osteoporosis (RA, coeliac, AS,
Hyperthyroidism, Hyperparathyroidism, renal osteodystrophy
Maternal family history of hip fracture
BMI < 19
(espin Caucasians and Asians)
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