Bone disorders

Types of Bone Lamellar Woven Forms the adult skeleton \\ Arrangement of collagen fibers Few osteocytes Uniform osteocytes in lacunae // to long axis of collagen fibers Woven Irregular Many osteocytes of various size and shape In adults signifies always a pathologic condition

Cells Osteoblasts: bone forming cells Produce the protein Osteoid Osteocyte: bone maintaining cells Osteoblast within bone in a lacuna Osteoclast: bone eating cells Multinucleated Resorbs bone Howship’s lacunae

Types of bone disorders Metabolic Conditions: Osteoporosis, Osteomalacia and rickets Hereditary and Congenital Disorders Inflammatory Neoplasms

Metabolic Conditions

1- Osteoporosis : The Silent Thief - Osteoporosis is a metabolic bone disease characterized by low bone mass and micro-architectural defect of the bone tissue, with a consequent increase in bone fragility and susceptibility to fracture - Are of two types: primary and secondary Amount of bone resorbed >>> Amount of bone formed by osteoclasts by osteoblasts BONE LOSS

Primary Osteoporosis Most common Uncertain etiology Postmenopausal women Elderly persons (senile) Genetic: peak bone mass Estrogens: decreased Aging Calcium intake Environmental factors: smoking leads to estrogen

Secondary Osteoporosis Corticosteroids Inhibition of osteoblastic activity Impair of vit. D dependant intestinal calcium absorption Hematologic malignancies Malabsorption: GI and liver diseases Alcoholism Inhibition of osteoblasts, ↓ absorption of calcium

Steroid-induced Osteoporosis Cause Calcium Urinary Calcium Osteoblast absorption excretion formation and function Majority of bone loss occurs in the beginning (10-20%) 25% may experience a fracture 4 fold increase in all fractures Usually affects vertebrae, ribs, hip Risk higher in patients with higher dose, taking longer duration

2- Osteomalacia and rickets Inadequate mineralization of newly formed bone matrix (osteomalacia) Rickets: children, epiphyseal plates open; also problem with cartilage Beaded appearance of costo-chondral junctions Dental abnormalities Vitamin D deficiency Phosphate deficiency Defects in mineralization process

3- Hyperparathyroidism Parathyroid adenoma, hyperplasia, rare malignancy Promotes excretion of phosphate in the urine and stimulates osteoclastic activity resulting in hypercalcemia

Hereditary and Congenital Diseases

1- Osteogenesis imperfecta Many types Mutations of collagen type I gene Multiple fractures (starting in utero) Dental findings: Dentinogenesis imperfecta

2- Achondroplasia 80% new mutations Most common form of inherited dwarfism Absence or decreased area of proliferative cartilage Epiphyseal disorder (plate closes prematurely preventing bone growth) Head and torso are normal Vertebral column and hip abnormality

Inflammatory and Non-Inflammatory (Non-neoplastic) Disorders

1- Osteonecrosis Avascular, aseptic Ischemic death of bone and marrow in absence of infection Emboli: bone infarction Trauma Corticosteroids Radiation Alcoholism Systemic diseases: sickle cell anemia, gout, metabolic diseases Osteochondritis dissecans: dead piece of cartilage Site specific: head of femur

2- Myositis Ossificans Formation of reactive bone in muscle as a result of injury More common in lower limbs Diagnosis: radiographically and histologically

3- Osteomyelitis Inflammation of bone caused by an infectious organism Staphylococcus, streptococcus, neisseria gonorrhea,….. Direct penetration Wounds, fractures, surgery Hematogenous Bloodstream, teeth; metaphyses Knee, ankle, hip

Complications of Osteomyelitis Septicemia Acute bacterial arthritis Pathologic fractures Squamous cell carcinoma Chronic osteomyelitis

4- Osteoarthritis Most common joint disease Slow progressive degeneration of articular cartilage Weight bearing joints Fingers Primary: defect in cartilage, not an inflammatory disease Secondary: trauma, crystal deposits, infection Interphalangeal joints, knees, hips, cervical and lumbar spine 23

Clinical picture Narrowing of joint space (loss of disk) Increased thickness of subchondral bone Subchondral bone cysts 24

5- Rheumatoid arthritis Systemic chronic inflammatory disease Autoimmune disease STARTS AS SYNOVIAL DISEASE More common in women 3:1 Remissions and exacerbations 25

6- Gout Increase in serum uric acid and deposition of urate crystals in the joints and kidneys Only 15% of patients with ↑ uric acid suffer from gout Gout can result from: Overproduction of purines Augmented catabolism of nucleic acids Decreased uric acid secretion Primary gout Secondary gout 26

Primary gout Hyperuricemia in the absence of other disease Asymptomatic hyperuricemia can precede gout Impaired secretion by kidneys 27

Secondary gout Tumors Alcoholism Leukemias Lymphomas After chemotherapy Alcoholism Accelerated ATP catabolism 28

Clinical features Acute gouty arthritis Painful Involves one joint initially, then polyarticular Podagra (painful, red metatarsophalangeal joint) Tophaceous gout Development of tophi Chalky, cheesy, yellow-white, pasty deposits of monosodium urate crystals 29

Bone Tumors

Bone Forming Benign: Osteoma Osteoid Osteoma Osteoblastoma Malignant: Primary and secondary osteosarcoma Cartilagenous Benign: Chodroma Osteochodroma Malignant: Chodrosarcoma Other Giant cell tumor of bone Ewing sarcoma

Metastatic Tumors of the Jaws Most common form of cancer involving bone Breast and prostate carcinomas are most common Variety of symptoms: pain, swelling, loose teeth, ……. Site from which tooth was removed for local pain or mobility Prognosis is poor; most patients die within a year