A 70-year-old man presents with bilateral leg pain, weakness, and heaviness on walking that is relieved by sitting or bending forward (shopping trolley sign). MRI shows multilevel lumbar stenosis. What is the pathophysiology of the posture-dependent symptom relief?

• A Flexion reduces arterial supply to the cauda equina, reducing metabolic demand
• B Extension increases the spinal canal diameter by unfolding the posterior longitudinal ligament
• C Bending forward reduces venous congestion by reversing CSF pressure gradients
• D Flexion widens the spinal canal by stretching the ligamentum flavum and increasing foraminal dimensions, reducing neural compression ✓

Explanation

In lumbar canal stenosis, extension narrows the canal further as the ligamentum flavum buckles inward and facet joints override; flexion stretches the ligamentum flavum, increasing anterior-posterior canal diameter and enlarging the neural foramina. This explains why patients are relieved bending over a trolley (neurogenic claudication). Vascular claudication does not change with posture. The symptom-posture relationship differentiates neurogenic from vascular claudication.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.