Makindo Medical Notes

🦴 Osteochondroma is the most common benign bone tumour, arising as a cartilage-capped bony projection from the metaphysis of long bones. 🔎 Often found near growth plates (especially knee & proximal humerus), it is usually asymptomatic but can occasionally cause pain, mechanical problems, or—rarely—malignant transformation.

📖 About

• Definition: A benign bone tumour composed of bone & cartilage, projecting from the metaphysis.
• Types:
  • Solitary Osteochondroma: Single lesion, usually incidental & asymptomatic.
  • Multiple Osteochondromas (Hereditary Multiple Exostoses, HME): Autosomal dominant, multiple lesions, limb deformities, higher malignancy risk.

📊 Classification

📈 Epidemiology

• Accounts for 20–50% of benign bone tumours.
• Most cases diagnosed in childhood/adolescence (linked with growth spurts).
• More common in males.
• HME prevalence: ~1 in 50,000.

🧬 Pathophysiology

• Originates from growth plate (physis), growing outward as a stalk capped with cartilage.
• In HME: mutations in EXT1/EXT2 genes (heparan sulfate synthesis).
• Malignant change (rare): usually to secondary chondrosarcoma.

🩺 Clinical Features

• Asymptomatic: Incidental finding on X-ray.
• Symptomatic:
  • Local pain/discomfort.
  • Mechanical restriction of joint movement.
  • Neurovascular compression → numbness, tingling, weakness, or ischaemia.
  • Visible or palpable hard bony lump.

🔬 Diagnosis

• Clinical: Hard, painless mass near a joint.
• Imaging:
  • 📸 X-ray: Bony outgrowth with cortex & medulla continuous with parent bone.
  • 🖥️ CT: Defines bony architecture.
  • 🧲 MRI: Key for measuring cartilage cap (>1.5–2 cm in adults → suspicious for malignancy).
• Biopsy: Rare, reserved for suspicious cases.
• Genetics: EXT1/EXT2 testing in HME.

💊 Management

• Observation: Asymptomatic cases → regular follow-up.
• Surgical Excision:
  • Indicated if pain, deformity, restricted motion, or neurovascular compression.
  • Complete removal of bony stalk + cartilage cap prevents recurrence.
• Malignant Transformation:
  • Red flags: rapid growth, worsening pain, cap thickening >2 cm.
  • Requires wide resection ± oncology input.
• Genetic Counselling: For HME families.

📉 Prognosis

• Excellent for solitary lesions.
• HME: ↑ risk of deformity & ~1–5% chance of malignant change.

⚠️ Complications

• Chondrosarcoma transformation.
• Limb length discrepancies or angular deformities.
• Nerve/vascular compression.

📚 References

• NCBI Bookshelf – Osteochondroma
• Medscape – Osteochondroma
• Merck Manual
• UpToDate