Pathology of Bone, Joint and Soft Tissue Flashcards by Srishti D

What are metabolic bone conditions?

Osteoporosis
Rickets and osteomalacia
Hyperparathyroidism

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What are some tumour-like lesions of bone?

Cysts
Metaphyseal fibrous defect
Fibrous dysplasia
Langerhans’ cell histiocytosis

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What are bone forming tumours?

Osteoma
Osteoid osteoma and osteoblastoma
Osteosarcomas

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What are cartilage forming tumours?

Osteochondroma
Chondromas
Chondrosarcoma

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What is Paget’s disease of bone?

Disorder of bone formation >

Deformity
Decreased structural strength
Increased bone mass
Effects on other systems

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What is the cause of Paget’s disease of bone?

Uncertain

Abnormal osteoclast activation

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What are the three phases of Paget’s disease of bone?

Lytic
Mixed
Burnt out

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What are the clinical features of Paget’s disease of bone?

Middle age-elderly
Males slightly >females
White European descent predominance
Often asymptomatic with x-ray changes
Most polyostotic
Proximal femur common ~80% - small bones less common
Localised pain
Leontiasis ossea
Platybasia
Long bone bowing
Secondary osteoarthritis
Chalkstick and vertebral compression fractures
AV shunts > 
- Heart failure
- Warm skin
Osteosarcoma and other tumours
Radiological bone cortex thickening
Biochemical changes of increased serum ALP and hydroxyproline

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What is leontiasis ossea?

Lion face syndrome

Due to overgrowth of facial cranial bones

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What is platybasia?

Flattening of skull base > cranial nerve lesions, esp deafness

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What does Paget’s disease of bone look like macroscopically?

Thickened, deformed vascular bone

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What does Paget’s disease of bone look like microscopically?

Mosaic
Haphazard
Jigsaw patterns with variable osteoclastic/blastic activity
Increased marrow vascularity

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What is avascular necrosis?

Bone necrosis
Most commonly idiopathic
Can be secondary to numerous conditions

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What are the causes of secondary avascular necrosis?

Steroids
Trauma
Infection
Dysbarism
Pregnancy
Collagen disease
Sickle cell disease
Alcohol
Pancreatitis
Tumours
Epiphyseal disorders

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What is the mechanism of avascular necrosis?

Ischaemia

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What are the clinical features of avascular necrosis?

Pain common when subchondral
Osteoarthritis - depends on site
Asymptomatic if medullary infarcts small
Pain with big infarcts in
- Gaucher's
- Sickle cell disease
- Dysbarism

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What is Gaucher’s disease?

Can’t metabolise sphingolipid > sphingolipid deposition

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What are the macroscopic features of avascular necrosis?

Medullary cancellous bone - well demarcated lesion
Cortex has collaterals
Cartilage viable
Fracture can occur

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Why is cartilage viable in avascular necrosis?

Separate blood supply

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What are the microscopic features of avascular necrosis?

Lacunae devoid of osteocytes
Necrotic fat cells
Creeping substitution over dead scaffolding
Sometimes sloughing of articular cartilage

What is osteomyelitis?

Infection of bone

What are the causes of osteomyelitis?

Most commonly pyogenic bacteria
Less commonly
- Mycobacteria
- Viruses
- Fungi
- Parasites

What are the clinical features of osteomyelitis?

Acute
- Fever
- Malaise
- Chills
- Throbbing pain over infected site
Less obvious in
- Infants
- Elderly

What are the complications of osteomyelitis?

Necrosis
Flare-ups
Amyloid
Fracture
Endocarditis
Sepsis
Tumours

What are the investigations for osteomyelitis?

``` FBE - leukocytosis X-ray CRP Cultures Biopsy ```

What populations are particularly affected by TB?

Immigrants Immunosuppressed Indigenous Australians

What is the treatment for osteomyelitis?

Systemic ABs | +/- drainage

What are the microscopic features of osteomyelitis?

Acute inflammation Bacteria Caseating granulomata Other organisms

What is septic arthritis?

Organism-induced joint inflammation

What are the causes of septic arthritis?

Haematogenous | Direct inoculation

What are the causative agents of septic arthritis?

``` Pyogenic bacteria Mycobacteria Borrelia burgdorferi Viral Others ```

What are the clinical features of septic arthritis?

Acute inflammation | Knee common site

In what populations is septic arthritis more common?

``` Infants Immunosuppressed Pre-existing joint disease Drug users Joint trauma Sexually active ```

What are the investigations for septic arthritis?

Similar to osteomyelitis | Joint aspirate instead of biopsy

What are the tests run on joint aspirates for septic arthritis?

Gross description Cell count and differential Gram stain and culture Crystal examination

What is osteosarcoma?

Malignant mesenchymal tumour > tumour cells produce bone

What mutations in osteosarcoma are important?

RB | p53

Where is osteosarcoma more common?

Sites of bone growth

What are the clinical features of osteosarcoma?

``` Bimodal incidence - <20 years - Elderly Painful masses sometimes with fracture Aggressive > 10-20% with pulmonary metastases at diagnosis Metastases common cause of death ```

What are the radiographic features of osteosarcoma?

Destructive Lytic Blastic infiltrating lesions Reactive raised periosteum

What is the treatment for osteosarcoma?

Assumes presence of metastasses Multi-modal chemotherapy Limb salvaging surgery

What are the macroscopic features of osteosarcoma?

``` Knee commonest at metaphysis Flat bones with increasing age Bulky, grey, gritty White with haemorrhage Necrosis Soft tissue infiltration Uncommonly involves joint and tendo-ligamentous structures ```

What are the microscopic features of osteosarcoma?

Pleomorphic cells Sometimes multinucleated Abnormal mitoses Producing bone

What are the main types of soft tissue tumours?

``` Fatty tumours Fibrous tumours and tumour-like lesions Fibrohistiocytic tumours Tumours of skeletal muscle Tumours of smooth muscle Vascular tumours Peripheral nerve tumours ```

What are Baker's cysts associated with?

Osteoarthritis in knee

Where are Baker's cysts found?

Back of knee

What can rupture of a Baker's cyst cause?

Local inflammation and swelling at top of calf

What is the differential diagnosis for a ruptured Baker's cyst?

DVT