Normal and disrupted lumbar longitudinal ligaments: correlative MR and anatomic study

Area of Science:

• Radiology
• Orthopedic Surgery
• Spinal Imaging

Background:

• The posterior and anterior longitudinal ligaments are crucial for lumbar spine stability.
• These ligaments appear as low-signal intensity lines on sagittal spin-echo MR images.
• Disruption of these ligaments can occur during lumbar disc herniations.

Purpose of the Study:

• To prospectively evaluate the MR imaging appearance of lumbar longitudinal ligaments in patients with herniated nucleus pulposus (HNP).
• To correlate MR findings with surgical outcomes to assess the reliability of MR in detecting ligamentous disruption.
• To determine the sensitivity and specificity of MR imaging in identifying posterior ligament rupture.

Main Methods:

• Prospective evaluation of 17 patients with 19 HNPs using MR imaging.
• Correlation of MR findings with intraoperative surgical findings.
• Analysis of the signal intensity and continuity of the peripheral line representing the longitudinal ligaments around the HNP.

Main Results:

• Absence of the low-signal peripheral line around the HNP was the most reliable sign of posterior ligament rupture (100% sensitivity, 78% specificity).
• The peripheral line was disrupted in 8 of 19 cases, correlating with surgical findings.
• Chemical shift artifact between epidural fat and HNP caused two false-positive findings.
• A continuous peripheral line excluded ligament disruption.

Conclusions:

• MR imaging is a highly sensitive tool for detecting posterior longitudinal ligament disruption in lumbar disc herniations.
• The absence of a continuous low-signal peripheral line on MR images is a strong indicator of ligament rupture.
• MR imaging findings can aid in surgical planning by accurately identifying ligamentous integrity.