BONE PATHOLOGY

The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments (bone to bone)(tendon=bone to muscle) Divided into two divisions Axial skeleton Appendicular skeleton – limbs and girdle The skeleton has 206 bones

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

Normal bone

Types of Bone Cells Osteocytes Osteoblasts Osteoclasts 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

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

Stages in the Healing of a Bone Fracture Slide 5.19

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

Classification of Bone Pathology: Infectious Diseases of Bone Developmental Disorders of Bone Metabolic Disorders of Bone Avascular Bone Necrosis (Osteonecrosis) Paget’s Disease of Bone Tumors of Bone

Infectious Diseases of Bone Osteomyelitis Pott’s Disease

OSTEOMYELITIS Classification: Definition: This is inflammation of bone and bone marrow Classification: Non- bacterial osteomyelitis: Viral osteomyelitis Sarcoidosis Radiation osteomyelitis

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

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.

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.

Metapheseal blood sinsoids

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.

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.

MP of acute osteomyelitis Inflammation of bone

Acute osteomyelitis

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

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.

Pott’s Disease

Tuberculosis of the spine in an Egyptian mummy

Clinical presentation: Back pain Fever Night sweating Anorexia Weight loss Spinal mass, sometimes associated with numbness, paraesthesia or muscle weakness of the legs

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

Pott’s Disease; X-ray Pott’s Disease; MRI

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

Tuberculous in long bones Commonly around the knee, affects metaphysis and epiphysis, rarely diaphysis Well-defined lytic area

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.

HEREDITARY BONE DISORDERS Achondroplasia Osteogenesis imperfecta osteopetrosis

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

Achondroplasia

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

Laxity of joint ligments leads to hypermobilty Involvement of the bones of the inner and middle ear produces deafness Some patients have dentinogenesis imperfecta: small, fragile and discolored teeth due to deficiency of dentin The skin may be abnormally thin and the skin is susceptible to easy bruising

Osteogenesis imperfecta Laxity of joint ligaments Osteogenesis imperfecta Brittle bones

Dentinogenesis imperfecta

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

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

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

Metabolic Diseases of Bone

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.

Osteoporotic vertebral body Normal Vertebral body Osteoporotic vertebral body (right) shortened by compression fractures, compared with a normal vertebral body. Osteoporotic vertebral body Normal Vertebral body

Fracture Osteoporosis Vertebrae, osteoporosis - Gross, cut surfaces  

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) Cushing’s disease (Hypercortisolism) Drugs (Heparin and Steroids)

Postmenopausal Osteoporosis Due to estrogen deficiency Estrogen deficiency  increased resorption of bone by osteoclasts and decreased formation of bone by osteoblasts.

Osteoporosis Genetic factors Physical activity Peak bone mass Nutrition Menopause ↓ estrogen ↑ osteoclast activity Aging ↓ activity of osteoblasts ↓ physical activity Pathophysiology of postmenopausal and senile osteoporosis Osteoporosis

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

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

Osteonecrosis (Avascular Necrosis)

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.

Osteonecrosis Femoral head with a subchondral, wedge-shaped pale yellow area of osteonecrosis

Osteonecrosis Osteonecrosis of the head of the femur. A coronal section shows a circumscribed area of subchondral infarction with partial detachment of the overlying articular cartilage and subarticular bone.

PAGET’S DISEASE

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

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

Diagrammatic representation of Paget disease of bone, demonstrating the three phases in the evolution of the disease.

Etiology: Possible slow virus infection Possible genetic predisposition

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

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

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

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

Osteolytic changes of the skull

Mosaic pattern of lamellar bone

BONE TUMORS BENIGN TUMORS OF BONE

Classification of benign tumors of bone: Osteoma Osteoid osteoma Osteoblastoma Osteochondroma Osteochondromatosis Enchondroma

Osteoma Definition: Benign neoplasm that frequently involves the skull and facial bones

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

Osteoid osteoma

Osteoblastoma Similar to an osteoid osteoma but is larger (>2cm) and often involves vertebrae

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)

Osteochondroma

Osteochondromatosis Multiple hereditary exostosis in which there is multiple symmetric osteochondromas

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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