Download 9- Bone diseases

Bone disorders
Types of Bone
 Lamellar
 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
by osteoclasts
>>>
Amount of bone formed
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
absorption
Urinary Calcium
excretion
Osteoblast
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
Clinical picture
 Narrowing of joint space (loss of disk)
 Increased thickness of subchondral bone
 Subchondral bone cysts
5- Rheumatoid arthritis
 Systemic chronic inflammatory disease
 Autoimmune disease
 STARTS AS SYNOVIAL DISEASE
 More common in women
3:1
 Remissions and exacerbations
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
Primary gout
 Hyperuricemia in the absence of other disease
 Asymptomatic hyperuricemia can precede gout
 Impaired secretion by kidneys
Secondary gout
 Tumors
 Leukemias
 Lymphomas
 After chemotherapy
 Alcoholism
 Accelerated ATP catabolism
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
Bone Tumors
 Bone Forming
 Benign: Osteoma
 Malignant:
Osteoid Osteoma
Osteoblastoma
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