when bones go wrong

Bone Fractures

  • A fracture is a break in bone continuity

  • Caused by trauma, repeated stress, or weakened bone

  • Different fracture patterns exist

  • Healing depends on blood supply, bone remodelling, nutrition, and hormones

Bone Disorders – Overview

  • Bone disorders occur when normal bone structure or function is disrupted

  • Major causes include:

    • Developmental defects

    • Abnormal remodelling

    • Hormonal imbalance

    • Nutritional deficiencies

    • Aging

  • Bone health is influenced by:

    • Age

    • Hormone levels

    • Calcium and phosphate levels

    • Mechanical stress (exercise)

Disorders of Bone Development

  • Agenesis: failure of bone or part of a bone to develop

  • Osteogenesis imperfecta:

    • Genetic connective tissue disorder

    • Autosomal dominant inheritance

    • Caused by defects in type I collagen (COL1A1, COL1A2)

    • Leads to fragile bones

    • May also affect teeth, ligaments, and eyes

  • Spina bifida: congenital defect of the spine due to incomplete vertebral closure

  • Achondroplasia: disorder of bone growth causing short-limbed dwarfism

Disorders of Bone Remodelling

  • Normal bone remodelling balances:

    • Osteoclast-mediated bone resorption

    • Osteoblast-mediated bone formation

  • Disruption of this balance leads to weak or abnormal bone

  • Influenced by:

    • Aging

    • Hormonal changes

    • Calcium/phosphate imbalance

    • Reduced mechanical stress

Endocrine Bone Disorders

  • Gigantism

  • Acromegaly

  • Pituitary dwarfism

  • Hyperparathyroidism

  • Hypoparathyroidism

  • Postmenopausal osteoporosis

Nutritional Bone Disorders

  • Rickets:

    • Vitamin D deficiency in children

    • Poor bone mineralisation

  • Osteomalacia:

    • Vitamin D deficiency in adults

    • Soft, weak bones

  • Scurvy:

    • Vitamin C deficiency

    • Impaired collagen synthesis

Bone Disorders Linked to Aging

  • Osteopenia:

    • Mild reduction in bone mass

  • Osteoporosis:

    • Severe reduction in bone mass

    • Increased fracture risk

Changes in Bone Mass with Aging

  • Peak bone mass achieved in early adulthood

  • After mid-30s:

    • Gradual loss of bone mass begins

  • Bone loss accelerates in women after menopause

  • Bone loss also occurs in men

  • Poor diet and lack of physical activity increase risk

Osteoporosis

  • Bone resorption exceeds bone formation

  • Results in reduced bone strength and increased fracture risk

  • Associated with deterioration of skeletal microarchitecture

WHO Definition:

  • Bone mineral density ≥ 2.5 standard deviations below young adult mean

  • T-score ≤ −2.5

Pathophysiology:

  • In young adults:

    • Bone resorbed is replaced by equal new bone

  • After age 30–45:

    • Resorption exceeds formation

  • Imbalance varies by skeletal site

  • More pronounced in postmenopausal women

  • Primarily a disease of disordered bone architecture

Risk Factors:

  • Genetic disorders

  • Chronic disease

  • Poor nutrition

  • Reduced physical activity

  • Altered bone remodelling

Paget’s Disease of Bone

  • Chronic disorder of bone remodelling

  • Bone is broken down and rebuilt too rapidly

What Goes Wrong:

  • Osteoclasts become overactive

  • Excessive bone resorption occurs

  • Osteoblasts respond by rapidly forming new bone

  • Newly formed bone is disorganised:

    • Woven or mosaic bone

    • Not normal lamellar bone

Result:

  • Bone may be enlarged and denser

  • Bone is structurally weak

  • Increased risk of fractures