MRI Measurement of Neuroforaminal Dimension at the Index and Supradjacent Levels after Anterior Lumbar Interbody Fusion: A Prospective Study

Radiculopathy caused by degenerative disc disease is one of the most common indications for spine surgery. Treatment options include direct methods of nerve root decompression (e.g., foraminotomy) as well as indirect methods of decompression (e.g., distraction across the segment). Such indirect methods are commonly employed within the cervical spine.1-3) In contrast, radiculopathy arising from lumbar foraminal stenosis is generally addressed through more direct posteriorly-based techniques.4) Possible reasons for this difference may include the relative safety of the posterior lumbar approach, as well as uncertainty as to the degree of decompression attainable through indirect methods of distraction such as anterior lumbar interbody fusion (ALIF). Relatively few authors have sought to determine how much indirect decompression of the lumbar nerve root can be achieved through anterior distraction alone. In addition, little has been written about the effects of lumbar fusion and segmental distraction upon the dimensions of the supradjacent neuroforamina. If the neural foramen could be reliably expanded through indirect means without negative effect on the supradjacent segment foramen dimension, it is possible that the indications for certain current and future anterior lumbar procedures could be expanded. To our knowledge, no prior study has assessed prospectively the relative change in magnetic resonance imaging (MRI) demonstrated neuroforaminal dimensions in a consecutive series of patients after anterior interbody fusion without any posterior decompression. We sought to compare preoperative foraminal dimensions at each operative level with the corresponding postoperative size to determine the change attributable to anterior distraction alone in patients undergoing surgery for degenerative disease of the lumbar spine.