Pathology of Bone, Joint and Soft Tissue Flashcards
What are metabolic bone conditions?
Osteoporosis
Rickets and osteomalacia
Hyperparathyroidism
What are some tumour-like lesions of bone?
Cysts
Metaphyseal fibrous defect
Fibrous dysplasia
Langerhans’ cell histiocytosis
What are bone forming tumours?
Osteoma
Osteoid osteoma and osteoblastoma
Osteosarcomas
What are cartilage forming tumours?
Osteochondroma
Chondromas
Chondrosarcoma
What is Paget’s disease of bone?
Disorder of bone formation >
- Deformity
- Decreased structural strength
- Increased bone mass
- Effects on other systems
What is the cause of Paget’s disease of bone?
Uncertain
Abnormal osteoclast activation
What are the three phases of Paget’s disease of bone?
Lytic
Mixed
Burnt out
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
What is leontiasis ossea?
Lion face syndrome
Due to overgrowth of facial cranial bones
What is platybasia?
Flattening of skull base > cranial nerve lesions, esp deafness
What does Paget’s disease of bone look like macroscopically?
Thickened, deformed vascular bone
What does Paget’s disease of bone look like microscopically?
Mosaic
Haphazard
Jigsaw patterns with variable osteoclastic/blastic activity
Increased marrow vascularity
What is avascular necrosis?
Bone necrosis
Most commonly idiopathic
Can be secondary to numerous conditions
What are the causes of secondary avascular necrosis?
Steroids Trauma Infection Dysbarism Pregnancy Collagen disease Sickle cell disease Alcohol Pancreatitis Tumours Epiphyseal disorders
What is the mechanism of avascular necrosis?
Ischaemia
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
What is Gaucher’s disease?
Can’t metabolise sphingolipid > sphingolipid deposition
What are the macroscopic features of avascular necrosis?
Medullary cancellous bone - well demarcated lesion
Cortex has collaterals
Cartilage viable
Fracture can occur
Why is cartilage viable in avascular necrosis?
Separate blood supply
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
