OSTEOPOROSIS

Osteoporosis

Definition: —It is defined as the disease, characterized by low bone mass & micro-architectural deterioration of bone tissue leading to enhanced bone fragility & a consequent increase in fracture risk.
—There is a generalized reduction in bone mass due to subnormal osteoid production, excessive rate of deossification & sub-normal osteoid mineralization.

Two types: Generalized & Localized.

Generalized–
A) Primary: Type I → Post-menopausal (Osteoclast mediated);
Type II → Senile (Osteoblast mediated).

B) Secondary: ♦Hormonal,
♦Nutritional,
♦Drug related,
♦Inherited Metabolic Disorder…

Localized– ▪Prolonged Immobilization of limb (Disuse Osteoporosis)
▪Monoarticular RA
▪Sudeck’s Osteodystrophy (Complex regional pain syndrome 1)

Term Definition
BMD patient-specific bone marrow density score of certain anatomic areas
T score BMD relative to normal young matched controls (30-year-old adult of same sex & ethnicity)
Z score BMD relative to the control of same age, sex & ethnicity.
Osteopenia T score -1 to -2.5 of L2-4 vertebrae
Osteoporosis T score <-2.5 of L2-4 vertebrae

 

Methods of diagnosing Osteoporosis:

  1. Clinical Method- Moderate to severe low back pain, posterior mid-thoracic ache, with/without paravertebral muscle spasm.
  2. Physical Method- a)determining the density of bone by taking biopsy sample of Iliac Crest & utilizing the ‘Archimedes’ Principle of Buoyancy’ (Density=Mass/Volume);
    b)    Measurement of ageing of bone using “Tetracycline labelling” using ‘Isotope Kinetic Studies’.
  3. Chemical Methods- i)Hexosamine/Cellulose ratio (H:C ratio)- < 20% in old & osteoporotic people
    ii)EDTA soluble mucopolysaccharides- <50% in aged people.
  4. Radiological Method- a) Visual- Presence of Kyphosis, Biconcavity of vertebral bodies & compression fracture of the spine.
  5. b) Morphometric method- 1)Vertical height of vertebra in the centre & anteriorly on X-ray. In elderly osteoporotic person, height at the centre is less than 81% of the height anteriorly.
    2)Cortical thickness of 2nd metacarpal of Rt hand on X-ray AP view- the cortical thickness of <44% of total diameter in the midpoint of 2nd metacarpal of Rt hand.
    3) Singh Index- Grade 6– All normal groups of trabeculae are visible in X-ray of the Proximal femur.

    Singh-Index for Osteoporosis

Grade 5- Secondary compression trabeculae are not clearly visible; bone-biopsy shows normal histology.
Grade 4- Secondary tensile trabeculae are not clear; bone-biopsy normal

Grade 3- Principal tensile trabeculae are seen only in upper part & not visible in lower part- indicates definite Osteoporosis.
Grade 2- Principal tensile trabeculae are not seen even in upper part, indicating advanced Osteoporosis.
Grade 1- Even the principal Compressive trabeculae are not clearly visible, this shows the severe degree of Osteoporosis.

6. Microradiological methods

7. Histological methods.

 

DEXA (Dual Energy X-ray Absorptiometry)-
Advantages:

  • Higher beam intensity; faster scan (<5min for Lumbar spine)
  • Improved spatial resolution with easier identification of vertebrae
  • Better precision- usually done in AP-position; site- L1-L4 (most common).
  • Recently, the Lateral position is used, with the advantage of eliminating posterior arch & spine of vertebrae as well as aortic calcification from the measurement.

NEUTRON ACTIVATION ANALYSIS (NAA)-

  • relies on the fact that 99% of the calcium in the body is in the skeleton.
  • When the area under examination is irradiated with neutrons, many of its constituent elements become radioactive & can be identified & quantified by examining the characteristic gamma-ray emission.
  • Part-body NAA & Whole body NAA.

 

WHO Criteria:

  1. Osteopenia- T-score -1 to -2.5 SD
  2. Osteoporosis- T-score <-2.5 SD
  3. Established Osteoporosis- T-score <-2.5 along with a fracture.