On plain radiograph, 'Looser zones' (pseudofractures) are ribbon-like translucent lines perpendicular to the bone cortex with sclerotic margins. In which condition are they characteristically bilateral and symmetrical?
- A Paget's disease
- B Stress fractures from overuse
- C Osteomalacia ✓
- D Hyperparathyroidism (Brown tumours)
Explanation
Looser zones (also called Milkman lines or pseudofractures) are narrow transverse radiolucent bands perpendicular to the bone cortex with sclerotic margins, representing non-mineralised osteoid accumulation at sites of mechanical stress — a hallmark of osteomalacia. They are classically bilateral, symmetrical, and occur at characteristic sites: medial femoral neck, pubic rami, lateral scapular margins, ribs, and proximal ulna. Paget's disease shows 'blade of grass' fractures propagating along the long bone cortex. Stress fractures are typically unilateral and lack sclerotic margins. Brown tumours (hyperparathyroidism) are expansile lytic lesions without perpendicular orientation.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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