A 72-year-old man comes to the primary care clinic with a 6-month history of back and bilateral thigh pain provoked by walking. He normally can walk only 2-3 blocks before having to stop due to pain. However, when he is out walking with his grandchild, leaning on the stroller seems to provide pain relief. The patient also notices an occasional tingling sensation in his lower extremities. He has no prior trauma or history of rheumatologic disorders. On physical examination, muscular strength is normal and the sensory findings are unremarkable. Peripheral pulses are full and symmetric. Thickening of which of the following ligaments is most likely contributing to this patient's current presentation?
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This patient presents with spinal stenosis, an abnormal narrowing of the spinal canal occurring most commonly in the lumbar region. Compression of nerve roots results in a number of neurologic symptoms, including lower extremity pain, numbness/paresthesia, and weakness. The onset of pain with walking is referred to as "neurogenic claudication" as it may resemble symptoms seen in vascular claudication. However, the symptoms of spinal stenosis are posture-dependent. Extension of the lumbar spine (eg, standing, walking upright) further narrows the spinal canal and worsens the symptoms, whereas lumbar flexion (eg, walking uphill, leaning on a stroller/shopping cart) relieves the pain.
Degenerative arthritis of the spine is the most common cause of spinal stenosis, typically occurring in patients age >60. Over time, the intervertebral disc degenerates and begins to protrude, resulting in a corresponding loss in disc height. This loss of height places a disproportionate load on the posterior aspect of the spinal column, leading to formation of facet joint osteophytes and hypertrophy of the ligamentum flavum (a strong elastic ligament supporting the posterior aspect of the spinal canal). These physiologic changes lead to mechanical compression of nerve roots and corresponding neurologic symptoms.
(Choice A) The anterior longitudinal ligament covers the anterior aspect of the vertebral bodies, preventing excess spinal extension.
(Choice B) The iliolumbar ligament connects the fifth lumbar vertebrae to the iliac crest, strengthening the lumbosacral joint.
(Choice C) The interspinous ligaments connect the spinous processes and help limit flexion of the spine.
(Choice E) The sacroiliac ligament prevents distraction of the sacroiliac joint.
Educational objective:
Spinal stenosis occurs most commonly in the lumbar region and presents with posture-dependent lower extremity pain, numbness/paresthesia, and weakness. The most common cause is degenerative arthritis of the spine, which results in narrowing of the spinal canal due to intervertebral disc herniation, ligamentum flavum hypertrophy, and osteophyte formation affecting the facet joints.