Musculoskeletal
Osteoporosis
Osteoporosis is a systemic disease characterized by:
- Low bone mineral density (BMD)
- Micro-architectural deterioration of bone tissue
- Increase in bone fragility
- Increased risk of fracture
Osteoporosis is clinically importance since:
- Normally 50% of women and 20% of men over the age of 50 years will sustain a fragility fracture.
- Bone mineral density in later life depends largely on peak bone mass achieved in adolescence or young adulthood.
Children who have cancer treatment during the normal period of bone mass accrual, can’t mineralize their bones properly and are at risk for future deficits in bone mineral density (BMD) leading to:
- Fractures
- Kyphosis
- Pain
Maximal peak bone mass:
- An important determinant of osteoporosis and fracture associated with aging
- In normal individuals, bone mass rises rapidly during puberty
- Usually reaches its peak at the end of sexual development
Definition of Osteoporosis:
Please see Bone Health for Life: The Jean Hailes Foundation
The World Health Organization (WHO) Working Group defines osteoporosis according to measurements of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA).
Osteoporosis is defined as a bone density T score at or below 2.5 SD (standard deviations) below normal peak values for young adults.
Established or severe osteoporosis is present when there is at least one or more fragility fracture in conjunction with a T score < -2.5.
The definition in young adults or children after treatment for cancer has yet to be established
Osteopaenia refers to T scores between –1.0 and –2.5.
Normal bone density is present if the T score is greater than –1.
These criteria were initially established for the assessment of osteoporosis in Caucasian women.
BMD reports may include a “Z score” which is the number of standard deviations by which the subject of interest differs from the mean for their age. This is of greater clinical utility in younger individuals.
| DEXA BMD Values | Definition |
T score > -1.0 S.D |
Normal bone mineral density |
T score between –1.0 and –2.5 SD |
Osteopaenia |
T score < - 2.5 SD |
Osteoporosis |
T score < - 2.5 SD |
Severe osteoporosis |
The WHO definition of osteoporosis only takes into consideration measurement of bone density, with no component of bone quality.
A clinical definition of osteoporosis was developed in 2001 by the NIH Consensus Development Panel on Osteoporosis. It stated: “Osteoporosis is defined as a skeletal disorder characterized by compromised bone strength predisposing a person to an increased risk of fracture”.
This definition takes into consideration that there are other factors that influence bone quality such as the microarchitecture of bone. However, measurement of BMD remains the most useful clinical tool available for diagnosing osteoporosis.
The International Society for Clinical Densitometry (ISCD)
- Supports the WHO classification of osteoporosis when describing BMD in postmenopausal females
- Further refines the use of standard deviation T- and Z-scores and terminology for patients who are not postmenopausal females.
- For children, men less than 50 years old or premenopausal women use a mechanism to reflect the relationship of the patient’s BMD to age-matched normative standards:
- T-score:
- A comparison of an individual BMD to that of maximum normal healthy adults.
- Osteopenia is defined as a T-score between -1 and -2.5 , and osteoporosis as a T-score below -2.5.
- Z-score
- Relates individual BMD to age, gender and, depending on the modality, race-matched normal population.
- In children, a T score is not useful and age and sex adjusted Z scores or standard deviation scores (SDS) are required.
