A 55-year-old postmenopausal woman with known osteoporosis is investigated for back pain. On MRI of the lumbar spine, a vertebral compression fracture at L2 shows low signal intensity on T1, high signal on STIR/fat-suppressed T2, restricted diffusion on DWI, and convex posterior cortex bulging. What feature most reliably distinguishes this as a pathological (malignant) rather than an osteoporotic fracture?

• A Posterior element involvement and an associated paraspinal soft tissue mass ✓
• B Convex posterior cortical bulging into the spinal canal
• C Diffuse low T1 signal throughout the entire vertebral body
• D Presence of a fluid-filled intravertebral cleft (vacuum cleft sign)

Explanation

Distinguishing malignant from osteoporotic vertebral fractures on MRI is clinically critical. Features favouring malignancy include: involvement of the pedicles and posterior elements (which have a rich blood supply and are targeted by haematogenous metastases), a convex posterior cortex, complete marrow replacement (diffuse low T1 signal), paraspinal or epidural soft tissue mass, and multiple level involvement. Posterior element involvement with a paraspinal mass is highly specific for malignancy. The vacuum cleft or intravertebral cleft sign (fluid or gas within the fracture) and preservation of normal fat signal islands within the vertebra are features that favour benign osteoporotic fracture.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.