The ligamentum flavum at L4-5: relationship with anthropomorphic factors and clinical findings in older persons with and without spinal disorders.

OBJECTIVE

To examine the relationship between ligamentum flavum thickness and clinical spinal stenosis.

DESIGN

A validation study.

SETTING

Clinical research laboratory.

PATIENTS

A total of 119 subjects from the Michigan Spinal Stenosis Study (MSSS).

METHODS

Two new measurement techniques were compared by use of magnetic resonance images of 4 asymptomatic subjects by 2 examiners. The technique with the best interrater reliability was then used to measure the ligamentum flavum at L4-L5 in 119 subjects in the MSSS who, on the basis of clinical examination without imaging, were thought to have lumbar stenosis, mechanical back pain, or no pain. These findings were related to other radiologic findings, demographics, clinical severity, and electrodiagnostic findings.

MAIN OUTCOME MEASUREMENTS

Perpendicular on the inside of the spinal canal from the deepest point of concavity of the lamina to the edge of the ligament.

RESULTS

The ligamentum flavum width measurement had high interrater (r = 0.774) and intrarater (r = 0.768) reliability. In 28 asymptomatic volunteers, ligamentum flavum width averaged 5.72 ± 0.95 mm, with the left side significantly thinner than the right (t = 2.117, P = .044), and thicker ligaments with age (r = 0.653, P < .001). Asymptomatic persons whom radiologists thought had stenosis had thicker ligaments (t = 2.273, P = .032). Persons with clinical stenosis (n = 48) and mechanical pain (n = 43) had ligament thickness similar to that of asymptomatic volunteers. Among patients with clinical stenosis, ligamentum flavum thickness did not relate to symptom severity (pedometer and laboratory ambulation tests, Pain Disability Index, and visual analog scale for pain). Most neurophysiological findings had no relationship with ligamentum flavum width, except the presence of limb fibrillation potentials related to a thinner ligament (t = 2.915, P = .004).

CONCLUSIONS

The measurement technique is standardized for the ligamentum flavum for future use. Although the ligamentum flavum appears to get thicker with age, other factors, including clinical diagnosis, pain, and function, do not appear to relate to the ligamentum flavum width.