Osteoporosis is the most common of all bone diseases in adults.It is prevalent in postmenopausal women but also occurs in males.Osteoporosis is defined as reduction of bone mass ( or density)It results from diminished organic bone matrix ( Guyton Page 588) Harrison ‘S book Of Internal Medicine says that Osteoporosis results from changes in remodeling process.
How is bone formed?
It is formed in three stages.
1) Osteoid formation
2) Mineralization Of Osteoid
3) Modeling till puberty & later on remodeling
Osteoid formation- Bone is composed of tough organic matrix,which consists of 90 to 95% collagen fibers with gelatinous ground substance. Collagen fibers extend primarily along the line of tensions force.Ground substance is composed of extracellular fluid plus proteoglycans namely chondroitin sulphate & hyluronic acid.They help in deposition of calcium salts.These are formed by osteoblast cells of bone.As Osteoid is formed some of the osteoblasts are trapped in it which are called osteocytes.
Mineralization Of Osteoid- ocurres within a few days of Osteoid formation, by deposition of calcium & phosphate on the surface of collagen fibers which grow over a period of days & weeks to form the finished product called hydroxyapatite.Other ions present in bone are magnesium,sodium,potassium & carbonate.Collagen fibers offer great tensile strength & calcium salts offer great compressive strength to bone.
Modeling & remodeling – The skeleton increases in size by linear growth & by apposition of new bone tissue on the outer surface of cortex. This apposition process is the phenomenon of modeling which also allows the adaptation in shape to respond to stressplaced upon them.Once the peak skeletal mass is attained,the process of remodeling becomes the principle metabolic activity of skeleton.This has three primary functions.
1) Repair microdamage in the bone
2) To maintain bone strength
3) To supply calcium from skeleton to maintain serum calcium level.
Process Of remodeling occur by actions of osteoblast cells to form the bone & osteoclast cells to absorb the bone. This is regulated by estrogen,androgens,Vitamin D & Parathyroid hormone. Osteoclast cells are large,multinucleted,phagocytic cells.They are under influence of Parathyroid hormone.The net result of remodeling is mass of the bone remaining constant by balance of osteoblast & osteoclast cells activity.
Pathophysiology of Osteoporosis –
1) After the age of 30 to 45 the resorption & formation process becomes imbalanced. The resorption exceeds formation.It May begin at different age & vary at different skeletal sites.
2) Nutrition – Sufficient protein intake is necessary for Osteoid formation.Inadequate calcium & or Vitamin D will lead to secondary hyperparathyroidism leading to increased osteoclastic activity.Hence adequate calcium & Vitamin D is essential to maintain normal bone mass.
3) Physical activity – helps to maintain bone mass by stimulating osteoblast activity.Athletes & rural people have more bone mass due to physical activity
4) Menopause – Estrogen deficiency causes bone loss by reduced osteoblast activity.This leads to imbalance of bone formation & resorption. ( remodeling imbalance) Remodeling is initiated at surface of bone.Trabecular bone has larger surface area than cortical bone,hence get affected more commonly.Bones which have more trabecular component e.g. vertebrae face fractures more commonly.
5) Chronic Diseases – Of different types may lead to excessive bone loss by poor nutrition,less physical activity & factors affecting remodeling rates. e.g. Cushing’s syndrome,Rheumatoid arthritis
6) Medications – Glucocorticoids,anticonvulsants,immunosuppressants are found to lead to bone loss.
7) Cigarette consumption – for a long period may lead to bone loss by toxic effect on osteoblast cells
Measurement of bone mass
DXA ( DEXA scan ) is highly accurate X ray technique to measure bone mass ( density) T score of -1 is normal Less upto – 2.5 is suggestive of Osteopenia Less than – 2.5 is considered as Osteoporosis.It is tested in Lumbar vertebrae & neck of femur.
Ultrasound is used for screening for osteoporosis.It detects bone mass by calculating the attenuation of signal as it passes through the bone.
Calcium,Vitamin D,Protein supplementation
Bisphophonates – reduce osteoclstic activity
Calcitonin nasal spray – reduces the osteoclasic activity
Teriparatide injection given subcutaneously for three months, which is a synthetic form of Parathyroid Hormone.Its intermittent use stimulates osteoblast to deposit bone to increase bone mass.
Yoga as a controlled Physical activity- Carefully selected Yogic Postures offer a safe & easy form of physical activity involving many bones,joints & muscles.
* This information is applied in Medical Yoga Therapy to help the patients.