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 UK have osteoporosis, 7.8 million in US

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 UK

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.
(Chen MB, 1999 21 st meeting of the American society for bone and mineral research ASBMR 1999)

- 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)

  • Previous and subsequentvertebral #; 4.4 x greater c/w no previous #
  • Wrist and further wrist3.3 x c/w no previous #
  • Hip and further hip 2.3x
  • Pooled around 2 xgreater for all #s after any previous #


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

Radiographic Diagnosis of Osteoporosis

Type of device

Radiation exposure

Cost

Use in monitoring therapy

DEXA

Low

Moderate

Accepted

Quantitative US of heel

None

Low

Not accepted

Quantitative CT

High

High

Not accepted

Bonnick SL. Bone densitometry in clinical practice: application and interpretation. Totowa , N.J. :Humana, 1998.

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, IDDM , MS ,OI, IBD)

Hyperthyroidism, Hyperparathyroidism, renal osteodystrophy

Maternal family history of hip fracture

BMI < 19 (espin Caucasians and Asians)


Drugs also ass/wi Osteoporosis are

Excess thyroid Tx
Prolongedheparin use
Premenopausal tamixofen
Immunosuppressants
Antidepressants
Testosterone antagonists.
High Caffeine intake


PRIMARY & SECONDARY PREVENTION OF OSTEOPOROTIC #s

TREAT THE OSTEOPOROSIS

If T-score is -1 to -2.5

1) Calcium (1000-1500mg)Vitamin D (400-800IU) supplements .

- Calcium supplementation 1000-1200mg dailydecreases menopause related bone loss and reduces the rate of vertebral andnon-vertebral fractures. It is more efficacious with Vitamin D in the elderly.

- RCT post-menopause, calcium 1000mg for atleast 2 yrs decreased bone loss at hip and spine; greatest effect in 1 st year. (Mackerras D, Bone 1997 21:527-533),

- RCT >65 yrs 500mg Calcium and 700IU VitaminD daily for 3 yrs, reduced risk of nonvertebral #s by 50% NNT 15 (Dawson-HughesB NEJM 1997 337:670-676)

- RCT ambulatory elderly 1200mg calcium and800IU vitamin D for 18 months, reduced risk of hip fracture (NNT 48) and othernon-vertebral #s(NNT 26) RR 0.25 (Chapuy MC NEJM 1992 327:1637-1642)

- If previous vertebral #, reduces risk ofadditional fractures

RCT 1200mg calciumRR 0.26 (Recker RR J Bone Miner Res 1996 11:1961-1966).



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