Metabolic Bone Disorders

Dr. Mohammed M. ZamzamAssociate Professor & Consultant

Pediatric Orthopedic Surgeon

Calcium Homeostasis

- Bone is not only for support

- Bone formation & bone resorption

- Hydroxyapatite crystals

- Calcium & phosphate control

* Intestinal absorption

* Renal excretion

* Bone

Vitamin D

* Sources - Diet

- Ultraviolet rays on skin

* Cholecalciferol activation

- PTH

- Phosphate concentration

* Action - Intestinal absorption of Ca

- Bone resorption

Parathyroid Hormone

- Fine regulator of Ca exchange

- Serum Ca regulate its secretion

- Action

* Increase phosphate excretion

* Increase Ca reabsorption

* Vitamin D activation

Calcitonin

- C cells of thyroid gland

- Serum Ca regulates its secretion

- Action

* Rapid hypocalcaemic effect by inhibiting

bone resorption

Secondary rule

Other Hormones Non-hormonal Factors

- Estrogen

- Corticosteroids

- Thyroxin

- Mechanical stress

- Prostaglandin E

- Acid-base balance

Rickets & Osteomalacia

- Different expressions of the same disease

- Inadequate mineralization

- Rickets

* Areas of endochondral growth

- Osteomalacia

* All skeleton is incompletely calcified

Rickets & Osteomalacia* Causes

- Calcium deficiency

- Hypophosphataemia

- Defect in Vitamin D metabolism

nutritional

underexposure to sunlight

intestinal malabsorption

liver & kidney diseases

Rickets & OsteomalaciaSymptoms & Signs

*Rickets

- Tetany or convulsions ?

- Failure to thrive , muscle flaccidity

- Craniotabes , joint thickening

- Pigeon chest , rickety rosary , Harrison’s sulcus

- Deformities

Rickets & OsteomalaciaSymptoms & Signs

*Osteomalacia

- Bone pain , backache

- Muscle weakness

- Vertebral collapse kyphosis

loss of height

- Deformities & stress fractures

Rickets & OsteomalaciaBiochemistry

Hypocalcaemia,… Hypocalcuria

High alkaline phosphatase

Rickets & OsteomalaciaX-rays

*Rickets - Growth plate widening & thickening

- Metaphyseal cupping

- Diaphyseal deformities

*Osteomalacia - Looser zone , biconcave vertebra , protrusio acetabuli

- Spontaneous fractures

*Signs of secondary hyperparathyroidism

Rickets & OsteomalaciaTreatment

*Vitamin D deficiency

- Rickets controlled Vitamin D

sun exposure

correct residual deformities

- Osteomalacia Vit. D + Ca

fracture management

correct deformity if needed

Hyperparathyroidism

*Primary

hyperplasia - adenoma - carcinoma

*Secondary

persistent hypocalcaemia

*Tertiary

secondary leads to hyperplasia

Hyperparathyroidism

Pathology

- PTH overproduction

- Increased renal tubular absorption , intestinal

absorption and bone resorption of Ca

- Hypercalcaemia and hypercalciuria

- Suppressed phosphate tubular reabsorption

- Hypophosphataemia and hyperphosphaturia

Hyperparathyroidism

Pathology

*Hypercalcaemia

calcinosis , stone formation , recurrent infection and soft tissue calcification

*Bone resorption

loss of bone substance , subperiosteal erosion

osteitis fibrosa cystica and brown tumors

Hyperparathyroidism

Symptoms & Signs

*Hypercalcaemia

anorexia , nausea , depression and polyuria

*Bone rarefaction

pain , pathological fractures and deformities

*Biochemistry

hypercalcaemia , hypophosphataemia , high

alk. Phosphatase and serum PTH

Hyperparathyroidism

X-rays

- Subperiosteal bone resorption

- Generalized decrease in bone density

- Brown tumors

- Chondrocalcinosis

knee , wrist and shoulder

Hyperparathyroidism

Treatment

Surgical excision of adenoma or hyperplastic

parathyroid tissue

*Hungry bone syndrome

treated by vitamin D

Osteoporosis

* Normal mineralization

* Decrease bone mass

(amount of bone per unit volume)

* Age related

* Associated or manifestation of other conditions

Osteoporosis

Causes

* Idiopathic

* Nutritional

* Endocrine disorders

* Drug induced

* Malignant diseases

* Miscellaneous

Osteoporosis

- Idiopathic osteoporosis - normal investigations

- In old patients we have to role out malignancy

and multiple myeloma

- Younger patients must be fully investigated

- Several causes may be involved

- Osteoporosis can be associated with osteomalacia

Osteoporosis

Symptoms & Signs

- Bony aches

- Easy fractures

spine - lower radius - femoral neck

- Rib fracture , chest pain

- Normal biochemistry

Osteoporosis

X-rays

- Decrease bone density

- Wedging or biconcave vertebrae

- Thin cortex and deformities

- Dexa Scan

- Biopsy

Osteoporosis

Treatment

- Treat underlying cause

- Idiopathic , extremely difficult

- Calcium and vitamin D

- Fluoride and triple therapy

- Calcitonin , Diphosphonate

- Treat fractures

Osteoporosis

Prevention

* Good diet

* Exercise

* Exposure to sun light

* Ca supplement

* Hormone therapy