Bone disorders

Types of BoneLamellar

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 OsteoporosisMost commonUncertain etiologyPostmenopausal womenElderly persons (senile)

Genetic: peak bone massEstrogens: decreasedAging Calcium intakeEnvironmental 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

Majority of bone loss occurs in the beginning (10-20%)25% may experience a fracture4 fold increase in all fracturesUsually affects vertebrae, ribs, hipRisk higher in patients with higher dose, taking longer duration

Cause

Calcium Urinary Calcium Osteoblast absorption excretion formation and

function

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- OsteonecrosisAvascular, 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- GoutIncrease 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 featuresAcute 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 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