Source / episode info

• **Episode:**269
• **Title:**Divine Intervention Episode 269 – NBME Ortho Series 1: Bone Tumors.
• **Published:**2020-10-21
• Source:Episode page

One-liner

This episode reviews high-yield orthopedic bone pathologies, emphasizing the differential diagnosis of common benign lesions (osteoid osteoma, enchondroma, osteochondroma) based on clinical and radiographic clues, while detailing the risk factors, presentation, and management principles for malignant tumors like osteosarcoma, Ewing sarcoma, and multiple myeloma.

High-yield summary

• Osteoid Osteoma: Characterized by pain worse at night, relieved by NSAIDs (COX inhibitors). Radiographically presents with a "bull's eye" pattern: radiolucent center surrounded by dense sclerotic bone. It is a unilateral process.
• Multiple Myeloma (MM): A plasma cell malignancy presenting with the mnemonic CRAB: Chypercalcemia, Renal failure, Anemia, and Bone pain. Plasma cells secrete Osteoclast Activating Factor (OAF), leading to bone resorption.
• Osteosarcoma: Highly aggressive malignant tumor. Key risk factors include history of retinoblastoma, Paget's disease, radiation exposure to the extremity, or prolonged use (>2 years) of PTH analogs like Teriparatide. Metastasis most commonly involves the lungs (requires CT chest).
• Ewing Sarcoma: Typically seen in young children/adolescents with an acute, infectious presentation (high fever, severe pain, elevated inflammatory markers). Biopsy shows small round blue cells and is associated with the EWS-FLI translocation.
• Osteochondroma: A benign bone lesion appearing like a mushroom; the head of the "mushroom" is cartilage, capping the underlying bone.
• Bone Metastases: The most common primary sources are prostate cancer (classically osteoblastic/sclerotic) and breast cancer (can be mixed or lytic). Elevated alkaline phosphatase (ALP) suggests bone pathology, but must be confirmed with elevated GGT or 5'-nucleotides for a diagnosis of metastatic disease.

Learning objectives

• Differentiate between common benign bone lesions (osteoid osteoma, enchondroma, osteochondroma) using clinical history and radiographic findings.
• Recognize the classic signs and symptoms associated with Multiple Myeloma, including the CRAB criteria.
• Identify key risk factors for malignant bone tumors such as Osteosarcoma and Ewing Sarcoma.
• Understand the pathophysiology of bone resorption in plasma cell dyscrasias (e.g., MM).
• Recall standard prophylactic measures required before orthopedic surgery.