The value of MR in differentiating subligamentous from supraligamentous lumbar disk herniations.

Purpose: To determine the value of MR criteria in differentiating subligamentous from supraligamentous lumbar disk herniations.

Methods: A retrospective review of surgical reports and MR images of 50 patients undergoing first-time lumbar surgery was performed. Three MR imaging criteria were assessed: the presence and integrity of a low-signal-intensity line posterior to the disk herniation, the size of the disk herniation in comparison with the size of the spinal canal, and the presence of disk fragments.