Osteomyelitis & Bone Tumours

Osteomyelitis

• Definition: Inflammation of the bone & marrow
• Challenging to treat
  • less choice of effective antibiotics
  • less penetrance of antibiotics into the bone
  • infection will lead to disability/morbidity!
    • viruses
    • bacteria
    • parasites
    • fungi

2 types of osteomyelitis

• Pyogenic osteomyelitis (Acute)
  • Infection reach bone by
    • Hematogenous spread (most common)
    • Extension from contiguous site
    • Direct implantation
  • Microorganisms
    • Staphylococcus Aureus (most common)
    • UTI & IV drug abusers
      • E. Coli
      • Pseudomonas
      • Klebsiella
    • Haemophilus influenza
      • children
    • Salmonella
      • sickle cell anemia
  • Pathophysiology
    • On Location:
      • infection reaches metaphysis
      • bacteria proliferates
        • causing bone death
          • Sequestrum: piece of dead bone
        • bone necrosis
      • sub-periosteal abscess formation
        • lifts the periosteum
        • further impair the blood supply
      • Rupture of Periosteum
        • abscess in surrounding soft tissue
      • Sinus formation
        • to drain fluid
    • Host response:
      • Release cytokines from leukocytes
        • stimulate osteoclastic bone resorption
      • Fibrous tissue formation
        • Reactive bone deposition in periphery
        • Forms a sleeve of new viable bone
          • Involucrum: new bone
  • Clinical course
    • Acute systemic illness
      • Pain
      • Tenderness
      • Immobility
    • Xray
      • Lytic focus of bone destruction
      • Followed by zone of sclerosis
    • Blood culture
      • can be +ve
    • Biopsy
      • invasive
      • confirms the diagnosis
  • Complications
    • Pathological fracture
    • Secondary amyloidosis
    • Endocarditis
    • Sepsis
    • Sinus tract squamous cell carcinoma (rare)
    • Epiphyseal infection
      • Joint cartilage is rigid
        • last to get infected
      • infection spreads to articular surface
      • spreads to joint capsule
        • suppurative/septic arthritis
      • lead to extensive destruction of articular cartilage
        • permanent disability
• Mycobacterial/Tuberculous osteomyelitis (Chronic)
  • 1-3% of TB cases
  • Infection sites:
    • Ribs
      • direct involvement
    • Vertebrae
      • from lymphatic drainage
      • common in thoracic & lumbar vertebrae
  • Spine TB: Pott’s spine
    • Infection breaks through intervertebral disc
      • involve vertebrae & soft tissue
      • forming abscesses
  • Complications
    • Psoas abscess formation
    • Compression fracture
      • of the vertebrae
    • Scoliosis or kyphosis
    • Spinal cord compression
      • neurological deficits
    • TB arthritis
    • Abscess
      • Sinus tract formation

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Bone tumours

• Rare
  • 40% malignant
• Aetiology
  • No obvious cause (usually)
  • Ionising radiation
  • Predisposing conditions:
    • Paget’s disease
    • Fibrous dysplasia
    • Retinoblastoma
      • genetic
    • Syndromes
      • Gardner’s
      • Ollier’s disease

Category/Classification

• Primary
• Bone-producing tumours
• Osteoid osteoma
• Osteoblastoma
• paediatric
• Osteosarcoma*
• Cartilage-producing tumours
• Osteochondroma*
• Chondroma (enchondroma)
• Chondrosarcoma*
• Miscellaneous tumors
• Ewing’s sarcoma*
• Giant cell tumor of bone*
• Secondary
• Metastases
• Tumour-like bone tumour (mimicry)
• Bone cysts
• Simple bone cyst
• Aneurysmal bone cyst
• Fibrous-osseous lesion
• Fibrous dysplasia
• Eosinophilic granuloma
• Langerhans histiocytosis

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Primary (more common in the young)

Osteosarcoma

 

Codman’s triangle & Sunburst appearance in Osteosarcoma

 
Osteosarcoma – spread towards cortex

 
Osteosarcoma – Lacy osteoid

• Because bone is a CT
• most common primary tumour
• young adults (10-25 yo)
• rare in later age, due to secondary causes
• Genetic
• mutations to RG gene
• Morphology
• Location
• metaphysis of long bone
• around knee
• tibia, fibula
• In old age
• flat & long bones
• Anatomical portion of bone
• Intramedullary
• most common
• tumour can break through cortex
• Intracortical
• Surface
• good prognosis
• Gross
• Form bulky tumours
• Gritty, gray white, yellowish mass
• Invasion to surrounding tissues
• Infiltrate the medullary canal & spread towards cortex
• epiphyseal penetration is rare
• Joint invasion
• later stages
• Microscopy
• Tumour cells are osteoblastic cells
• histologic variants:
• osteoblastic
• chrondroblastic
• small cell
• Formation of lacy osteoid by tumour cells
• Variation in size, shape
• bizarre features
• Tumour giant cells
• Hyperchromatism
• Mitiosis
• Binucleation
• Vascular & blood vessels invasion
• Xray
• large destructive mass lesion
• mixed lytic & sclerotic areas
• Elevation of periosteum
• Codman’s triangle
• Sunburst appearance
• spread of tumour into surrounding soft tissue

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Osteochondroma

 

• Cartilage covered by bony excrescense (exostosis)
• formation of new bone on surface of bone
• Can be solitary or multiple
• Spontaneous
• Location
• metaphysis
• diaphysis
• Morphology
• painless skeletal swelling
• slowly growing mass
• palpable bony masses
• Complications
• can lead to limb shortening
• when bone is still actively growing
• 1st – 2nd decade of life
• fractures
• bone deformities
• neurologic/vascular injuries
• bursa formation
• malignant transformation
• rare
• Osteochondromatosis
• autosomal dominant condition
• short stature
• multiple osteochondroma
• located close to metaphysis
• sessile or pedunculated
• cortex of lesion continuous with cortex of bone
• with a homogenous continuation of the medulla
• asymmetric growth
• knees
• ankles
• may lead to deformities

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Chondrosarcoma

 

Chondrosarcoma – affects axial skeleton

 
Chondrosarcoma – affecting the finger

• 2nd most common malignant primary bone tumour
• older adults
• 30-60 yo
• can arise from previous enchondroma
• many are sporadic
• location
• axial skeleton
• pelvis
• pectoral girdles
• ribs
• spine
• Aggressive
• erodes & invades soft tissue
• *Metastasize to: (suspect chondrosarcoma)
• lungs
• liver
• kidney
• brain
• Gross
• large bulky tumours
• grey white, translucent
• Microscopy
• malignant cartilage
• with anaplastic chondrocytes in spaces
• focal enchondral ossification & calcification
• hypercellularity, atypia, mitosis
• Treatment
• resistant to chemotherapy
• therefore must be surgical resection

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Giant cell tumour of bone (Osteoclastoma)

• Osteoclastoma
• potentially malignant
• mostly benign
• arise in epiphysis
• develop after fusion of cartilage
• after epiphyseal plate thins out
• lytic lesion at end of bone
• knee
• elbow
• ankle
• Treatment
• resection
• recurrence is common
• Pathology
• osteoclastic giant cells
• 100 or more nuclei
• nuclei similar to those of stromal cells
• giant cells are not malignant
• mesenchymal cells
• ovoid
• mononuclear cells
• Haemorrhage and necrosis present

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Secondary (metastatic)

Looking at the pattern of bone lesion, you should also screen for these primary cancer sites

• more common in the old
• most commmon malignant tumour in skeleton
• metastasize from:
  • breast tumour
  • kidney tumour
  • thyroid
  • lung
• Generally occur in
• vertebrae
• pelvis
• if primary tumour from pelvis, can spread to lumbosacral spine
• proximal parts of the
• femur
• humerus
• ribs
• skull
• Rare
• hands
• feet
• Marrow neoplasm (hemopoietic):
• myeloma
• leukemia
• lymphoma

Mixed lytic and sclerotic lesion

 
Sclerotic lesions