Osteoporosis is currently defined as
A systemic skeletal disease characterised by low bone mass and
microarchitectural deterioration of bone tissue, with a consequent
increase in bone fragility and susceptibility to fracture risk
Thus 'osteoporosis' presents as a complex multifactorial condition,
comprising several important determinants, mainly bone mass and the
degree of trauma the skeleton experiences. However osteoporosis is
usually asymptomatic until fractures occur, which then become a major
public health problem. Fractures therefore represent the visible
complication of the underlying symptomless deterioration of the skeleton.
Osteoporosis, hypercholesterolemia and hypertension thus share some
common medical similarities. It is also true that people with osteoporosis
will not all invariably experience non-traumatic fractures.
Osteoporotic fractures are commonly associated with the
At age 50 years 40% of women will sustain one or more osteoporotic
fractures within their lifetime. In comparison the equivalent risk for breast
cancer is 9% and 40% for cardiovascular disease.
While a definition of osteoporosis allows a general understanding of this
condition, actual diagnosis requires specific criteria. Consequently
osteoporosis is diagnosed by the measurement of bone mineral density
(BMD) at various skeletal sites and interpreted with respect to the subject's
percentile position within the corresponding young healthy adult reference
population. The World Health Organisation in 1994 issued the following
guidelines to classify BMD measurements
Spine (vertebral crush or wedge fractures)which
may lead to loss of height, kyphosis (spine curvature) and chronic back pain
Forearm (Colles' fracture - distal radius)
Hip (proximal femur)-
associated with the highest morbidity, mortality, and healthcare costs,
particularly amongst elderly women and men
Currently, BMD is most often measured at the spine and hip using a
technique called dual-energy x-ray absorptiometry (DEXA). Because BMD
accounts for about 75-85% of the variance in strength of bone tissue, it is not
only significant to the diagnosis of osteoporosis, but also allows
Normal - a BMD value greater than 1 SD (standard deviation) below the
young adult mean. This classifies 84.1% of the young adult population as
normal and 15.9% as abnormal.
Osteopenia (Low bone mass) - a BMD value between 1 and 2.5 SD below
the young adult mean. This classifies 15.2% of the young adult population
Osteoporosis - a BMD value more than 2.5 SD below the young adult mean.
This classifies 0.6% of the young adult population as osteoporotic
Established Osteoporosis - a BMD value more than 2.5 SD below the
young adult mean and the presence of one or more fragility fractures.
Strategies for reduction of the projected massive health care cost due to
fractures, particularly hip fractures, are directed at fracture prevention rather
than post-fracture treatment. Controversy still exists however on the
question of general population screening for osteoporosis, especially with
respect to whether only high-risk groups should be targeted and the best
agent for the individual patient.
- prediction of future fracture risk
- assessment of the rate of bone loss with time
- information on the success of intervention or prevention therapy
- extra data on decisions involving possible prescription of estrogen replacement therapy