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Osteoporosis and Osteomalacia:

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Osteoporosis:

Osteoporosis describes a state in which bone is fully mineralised but its structure is abnormally porous and its strength is less than normal for a person of that age and sex.

Bone mass in unit volume is decreased.

Bone depletion may be caused by predominant resorption, decreased bone formation, or both.

Bone strength is reduced due to reduction in bone mass, and due to structural failure in the new trabeculae.

This leads to a weak bone that fails upon minor strain especially in cancellous vertebrae and at diaphysio-metaphysis junction.

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Radiographic features:

Thinner cortices and loss of trabecular difinition

Osteopenia.

Classification of Osteoporosis:

Regional vs generalised

Primary (aging and reduction of gonadal activity) vs secondary

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Risk factors of primary Osteoporosis:1- Caucasoid (white) or Asiatic ethnicity2- A family history of osteoporosis3- A history of anorexia nervosa and / or amenorrhea4- Low peak bone mass in early adulthood5- Early onset of menopause6- Skinny or emaciated build7- Dietary insufficiency8- Alcohol abuse9- Cigarette smoking10- Chronic lack of exercise11- Low calcium intake is on the other hand controversial

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Clinical features of primary osteoporosis:

A woman, with back pain and increased thoracic kyphosis, and diminished height.

X-rays at this stage, show wedging of one or more vertebral bodies.

Sometimes, the first sign is a low-energy fracture of the distal radius.

Rx and prevention:

Upon approaching menopause, women should be advised to maintain adequate levels of dietary calcium and vitamin D, to keep up a high level of physical activity and to avoid smoking and excessive consumption of alcohol.

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If necessary, the recommended daily requirements should be met by taking calcium and vitamin D supplements.

Oestrogen (good and bad).

DEXA scan for screening, Bisphosphonates, Calcitonin, and Flouride.

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Osteomalacia (Rickets):

The disease involves inadequate mineralisation of bone. Bone tissue throughout the skeleton is incompletely calcified, and therefore ‘softened’ (osteomalacia). In children there are also effects on physeal growth and ossification, resulting in deformities of the endochondral skeleton (rickets).

Inadequacy may be due to:

1- Calcium deficiency 2- Hypophosphotaemia 3- Defects anywhere along the metabolic pathway for vitamin D 4- Nutritional lack 5- Underexposure to sunlight 6- Intestinal mal-absorption

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Pathology:

Inability to calcify the intercellular matrix in the deeper layers of the physis.

The proliferative zone is active as ever, but the cells, instead of arranging themselves in orderly columns, pile up irregularly; the entire physeal plate increases in thickness, the zone of calcification is poorly mineralised and bone formation is sparse in the zone of ossification

The new trabeculae are thin and weak, and with joint loading the metaphysis becomes broad and cup-shaped.

Away from the physis, the signs are those of osteomalacia; sparse islnads of bone, thin cortices, stress #s.

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If the disease is long standing, stress deformities apear; indentation of the pelvis, bending of the femoral neck (coxa vara) and bowing of the femora and tibiae.

Clinical features:

Children: tetany or convulsions, failure to thrive, listlessness and muscular flaccidity, cranio-tabes, thickening of the knees, ankles and wrists from physeal overgrowth. ‘Rickety rosary’ and Harrison’s sulcus may also appear. Distal tibial bowing.

Adults: bone pain and backache may continue for years before diagnosis is established. Loss of height and vertebral collapse and increment of older deformities.

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X-rays:

In active rickets:

Thickening and widening of the growth plates,

Cupping of the metaphysis,

Bowing of diaphysis,

Classic feature= Looser zone= a thin transverse band of rarefaction in an otherwise normal-looking bone seen usually in the shafts of long bones, are due to incomplete stress fractures.

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Biconcave vertebrae,Lateral indentation of acetabula (trefoil pelvis), Spontaneous #s of the ribs, pubic rami, femoral neck, shafts above and below knee.

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