A 20-year-old presents with nocturnal bone pain in the proximal femur that is dramatically relieved by aspirin/NSAIDs. Plain X-ray shows a 1.5 cm lucent nidus surrounded by dense sclerotic bone. This classic presentation is diagnostic of:

• A Osteoblastoma
• B Osteoid osteoma ✓
• C Enchondroma
• D Brodie's abscess

Explanation

Osteoid osteoma is a benign osteoblastic tumor characterised by a central vascularised nidus (<2 cm by definition, usually <1.5 cm) surrounded by reactive sclerosis in cortical bone. The hallmark is severe nocturnal pain dramatically relieved by aspirin/NSAIDs, due to prostaglandin E2 production by the nidus. CT is the gold standard for localising the nidus. Treatment options include radiofrequency ablation (RFA — first line) or en-bloc excision. Osteoblastoma (A) is histologically similar but >2 cm, lacks the intense pain response to salicylates, and is more centrally located (posterior spinal elements, vertebral bodies).

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.