BONE PATHOLOGY

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BONE PATHOLOGY
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The Skeletal System

• Parts of the skeletal system
• Bones (skeleton)
• Joints
• Cartilages
• Ligaments (bone to bone)(tendonbone to muscle)
• Divided into two divisions
• Axial skeleton
• Appendicular skeleton limbs and girdle

• The skeleton has 206 bones

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Functions of Bones

• Support of the body
• Protection of soft organs
• Movement due to attached skeletal muscles
• Storage of minerals and fats
• Blood cell formation

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Normal bone
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Types of Bone Cells

• Osteocytes
• Mature bone cells
• Osteoblasts
• Bone-forming cells
• Osteoclasts
• Bone-destroying cells
• Break down bone matrix for remodeling and release
  of calcium
• Bone remodeling is a process in which both
  osteoblasts and osteoclasts participate

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Bone Fractures

• A break in a bone
• Types of bone fractures
• Closed (simple) fracture break that does not
  penetrate the skin
• Open (compound) fracture broken bone penetrates
  through the skin
• Bone fractures are treated by reduction and
  immobilization
• Realignment of the bone

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Stages in the Healing of a Bone Fracture
Slide 5.19
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Stages in the Healing of a Bone Fracture

• 1-Haematoma formation
• 2-Fibrocartilage callus formation
• 3-Boney callus formation
• 4-Bone remodelling

Slide 5.19
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Classification of Bone Pathology

• Infectious Diseases of Bone
• Developmental Disorders of Bone
• Metabolic Disorders of Bone
• Avascular Bone Necrosis (Osteonecrosis)
• Pagets Disease of Bone
• Tumors of Bone

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Infectious Diseases of Bone

1. Osteomyelitis
2. Potts Disease

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OSTEOMYELITIS

• Definition
• This is inflammation of bone and bone marrow

Classification

• Non- bacterial osteomyelitis
• Viral osteomyelitis
• Sarcoidosis
• Radiation osteomyelitis

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• Bacterial osteomyelitis
• Acute suppurative osteomyelitis
• Acute haematogenous osteomyelitis
• Acute non-haematogenous osteomyelitis
• Chronic osteomyelitis
• Chronic non-specific osteomyelitis
• Chronic specific osteomyelitis ( TB Syphilis)

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ACUTE HAEMATOGENIUS OSTEOMYELITIS

• Definition Acute osteomyelitis is an acute
  inflammation of bone caused by an infecting
  organism

• Haematogenous osteomyelitis is predominantly seen
  in children and involves the highly vascular long
  bones especially those of the lower limbs.
• In adults, haematogenous spread is more common to
  the lumbar vertebral bodies than elsewhere.

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Pathogenesis

• The spread of infection is usually haematogenous.
  
• 1-Among children the metaphysis of the long
  bones is the most common site, where blood flow
  slows in the sinusoids, allowing bacteria to
  adhere to the vascular membranes.
• 2-Local trauma with skin penetration and seeding
  of organisms is another pathway.
• 3-Localized trauma without skin penetration to
  the bone causing haematoma, vascular obstruction
  in the metaphyseal region and bacteraemia at
  around the same time result in infection.

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Metapheseal blood sinsoids
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Stages of disease

• 1-Inflammation Initial inflammation with
  vascular congestion and increased intra-osseous
  pressure.
• 2-Suppuration Pus within the bones forces its
  way through the Haversian system and forms a
  subperiosteal abscess in 2-3 days.

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• 3-Sequestrum Vascular obstruction and infective
  thrombus decrease or obstruct the periosteal and
  endosteal blood supply, causing bone necrosis and
  sequestrum formation in approximately 7 days.
• 4-Involucrum This is new bone formation from the
  stripped surface of periosteum.
• 5-Resolution or progression to complications
  With antibiotics and surgical treatment early in
  the course of disease, osteomyelitis resolves
  without any complications.

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MP of acute osteomyelitis
Inflammation of bone
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Acute osteomyelitis
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Complications of osteomyelitis

1. Pathological fracture
2. Spread of infection eg. Arthritis (joint
   inflammation), myositis (muscle inflammation) or
   neuritis (nerve inflammation)
3. Blood spread causing toxaemia septicaemia
4. Chronic suppurative osteomyelitis including
   sequestrum formation and skin sinus formation
5. Damage to the growth plate causing subsequent
   growth deformity

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Pott's disease

• Pott's disease is a presentation of extra
  pulmonary tuberculosis that affects the spine, a
  kind of tuberculous arthritis of the
  intervertebral joints.
• The lower thoracic and upper lumbar vertebrae are
  the areas of the spine most often affected.

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Potts Disease
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Tuberculosis of the spine in an Egyptian mummy
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Clinical presentation

1. Back pain
2. Fever
3. Night sweating
4. Anorexia
5. Weight loss
6. Spinal mass, sometimes associated with numbness,
   paraesthesia or muscle weakness of the legs

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Diagnosis

• Blood tests elevated erythrocyte sedimentation
  rate (ESR)
• Tuberculin skin test
• Radiographs of the spine
• Bone scan
• CT of the spine
• Bone biopsy
• MRI

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Potts Disease X-ray
Potts Disease MRI
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Complications

• Vertebral collapse resulting in kyphosis
• Spinal cord compression
• Sinus formation
• Paraplegia (called Pott's paraplegia)

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Tuberculous in long bones

• Commonly around the knee, affects metaphysis and
  epiphysis, rarely diaphysis
• Well-defined lytic area

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Tuberculous arthritis

• The hip and knee are the
• most commonly affected
• peripheral joints.
• Characterized by joint space
• narrowing and erosions which
• may lead to extensive destruction
• of the articular cortex.

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HEREDITARY BONE DISORDERS

1. Achondroplasia
2. Osteogenesis imperfecta
3. osteopetrosis

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Achondroplasia

• Clinically
• Long bones are short and thick ? short
  extremities ? dwarfism
• Cranial and vertebral bone spared ? relatively
  large head and trunk
• Normal intelligence, life span and reproductive
  ability

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Achondroplasia
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Osteogenesis imperfecta

• 1-Generalized osteopenia brittle
• bones, resulting in recurrent
• fractures and skeletal deformity
• 2-Most patients have an
• abnormally thin sclera with
• blue hue

Abnormally thin sclera with blue hue
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1. Laxity of joint ligments leads to hypermobilty
2. Involvement of the bones of the inner and middle
   ear produces deafness
3. Some patients have dentinogenesis imperfecta
   small, fragile and discolored teeth due to
   deficiency of dentin
4. The skin may be abnormally thin and the skin is
   susceptible to easy bruising

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Laxity of joint ligaments
Osteogenesis imperfecta
Brittle bones
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Dentinogenesis imperfecta
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Osteopetrosis

• Marble bone
• Hereditary defect leading to thick sclerotic
  bones
• Pathology
• -Increased bone density and thickening of bone
  cortex
• -The thickened bones are brittle and fracture
  easily

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• X-ray findings
• Symmetrically generalized osteosclerosis
• Long bones may have broadened metaphyses,
  resulting in an "Erlenmeyer flask" deformity

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Osteopetrosis X-ray findings

• Symmetrically generalized
• Osteosclerosis
• Long bones may have broadened
• metaphyses, resulting in an
• "Erlenmeyer flask" deformity

Osteosclerosis
Erlenmeyer flask shaped deformity
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Metabolic Diseases of Bone
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Osteoporosis

• Refers to increased porosity of skeleton.
• Osteoporotic bones
• Thin and fragile and are susceptible to fracture.

• Occurs due to
• Loss of organic bone matrix and minerals.
• Resulting in
• Decreased bone mass and density.
• Decreased thickness of cortical and trabecular
  bone.

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Osteoporotic vertebral body
Normal Vertebral body
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Types of Osteoporosis

• Localized e.g. disuse of a limb
• Generalized involves entire skeleton.
• Primary
• Old age (Senile)
• Estrogen deficiency (postmenopausal)
• Secondary (due to underlying disease)
• Cushings disease (Hypercortisolism)
• Drugs (Heparin and Steroids)

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Postmenopausal Osteoporosis

• Due to estrogen deficiency
• Estrogen deficiency ? increased resorption of
  bone by osteoclasts and decreased formation of
  bone by osteoblasts.

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Genetic factors
Nutrition
Peak bone mass
Physical activity

• Menopause
• ? estrogen
• ? osteoclast activity

• Aging
• ? activity of osteoblasts
• ? physical activity

Osteoporosis
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Clinical findings

• Bone pain
• Weight bearing bones predisposed to
• Compression of vertebral bodies (most common)
• Colles fracture of distal radius.
• Fracture femoral neck.
• Loss of height and kyphosis

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• Diagnosis
• Dual energy X ray absorptiometry (DEXA) to
  evaluate bone density.

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Osteonecrosis (Avascular Necrosis)
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Osteonecrosis (Avascular necrosis)

• Ischemic infarction of bone bone marrow.
• Causes of ischemia
• Vascular interruption (fracture)
• Corticosteroids (most common)
• Sickle cell disease
• Common sites include
• Femoral head
• Scaphoid bone.

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Osteonecrosis
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Osteonecrosis
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PAGETS DISEASE
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• Definition
• Localized disorder of bone
• Due to Excessive bone resorption followed by
  disorganized bone replacement
• Resulting in Thickened but weak bone that is
  susceptible to deformity and fracture

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• Stages of paget disease
• Osteolytic osteoclastic activity predominates
• Mixed ostelytic-osteoblastic
• Osteosclerotic osteoblastic activity
  predominates " burnout stage"

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• Etiology
• Possible slow virus infection
• Possible genetic predisposition

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• Clinical features
• Asymptomatic in most cases
• Bone pain and deformities
• Fractures
• Warmth of overlying skin due to hypervascularity

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• Forms of involvement
• Monosteotic (15) involving one bone
• Polyosteotic (85) involving multiple bones
• Common sites include the skull, pelvis, femur and
  vertebrae

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PATHOLOGY

• Microscopically
• Haphazard arrangement of cement lines, creating a
  mosaic pattern
• Skull involvement
• Increase head size
• Foramina narrowing causes impingement of cranial
  nerves, often leading to deafness
• Involvement of facial bones may produce a
  lion-like facies

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• X-rays
• Bone enlargement with lytic and sclerotic areas
• Lab investigation
• Highly elevated serum alkaline phosphatase
• Complication
• Osteosarcoma
• Others sarcomas

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Osteolytic changes of the skull
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Mosaic pattern of lamellar bone
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BONE TUMORS

• BENIGN TUMORS OF BONE

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Classification of benign tumors of bone

1. Osteoma
2. Osteoid osteoma
3. Osteoblastoma
4. Osteochondroma
5. Osteochondromatosis
6. Enchondroma

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Osteoma

• Definition
• Benign neoplasm that frequently involves the
  skull and facial bones

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Osteoid osteoma

• Definition
• Benign, painful growth of the diaphysis of a long
  bone, often the tibia or femur
• Clinically
• Malesgt females
• Age 5-25 years
• Pain that is worse at night and relieved by
  aspirin
• X-ray
• Central radiolucency surrounded by sclerotic rim

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Osteoid osteoma
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Osteoblastoma

• Similar to an osteoid osteoma but is larger
  (gt2cm) and often involves vertebrae

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Osteochondroma (Exostosis)

• Definition
• Benign boney capped with cartilage that
  originates from epiphyseal growth plate
• Clinical presentation
• Adolescent males
• Firm solitary growths at the end of the long
  bones
• They may be asymptomatic or it causes pain,
  deformity or it can undergo malignant
  transformation (rare)

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Osteochondroma
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Osteochondromatosis

• Multiple hereditary exostosis in which there is
  multiple symmetric osteochondromas

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Enchondroma

• Definition
• Benign cartilaginous growth within the medullary
  cavity of bone, usually involving the hands and
  feet
• Typically solitary and asymptomatic and require
  no treatment

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