A 48-year-old man on prednisolone 60 mg/day for pemphigus vulgaris for 8 months presents with progressive right groin pain worsened by weight bearing. MRI shows a serpiginous subchondral line in the femoral head with a double line sign. The mechanism of this complication is:
- A Fat hypertrophy and embolisation occluding subchondral end arteries of the femoral head ✓
- B Direct suppression of osteoblast activity leading to trabecular microfractures
- C Steroid-induced hypercalcaemia causing deposition of calcium crystals in the joint
- D Increased osteoclast activation secondary to secondary hyperparathyroidism
Correct answer: A. Fat hypertrophy and embolisation occluding subchondral end arteries of the femoral head
Explanation
Glucocorticoids cause avascular (aseptic) necrosis of the femoral head, the most commonly affected site. The accepted mechanism is hypertrophy of marrow adipocytes raising intraosseous pressure plus fat embolism obstructing the terminal subchondral vessels, which lack collateral supply. Suppression of osteoblasts and increased osteoclast activity explain steroid-induced osteoporosis, a separate complication, which makes option B the strongest distractor but does not produce focal femoral head infarction.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.