An anatomical study of the lumbar external foraminal ligaments: appearance at MR imaging.

PURPOSE

The purpose of this study was to examine the MRI appearance of the ligaments within the external space of the lumbar intervertebral foramen by correlating MR images with the corresponding anatomic dissection of the cadaver lumbar spine.

METHODS

This was a two part study. Part I of the anatomic study consisted of the dissection of lumbar specimens from one embalmed adult male cadaver. At each lumbar level the external ligamentous structures were identified and their origin, insertion and position were determined. Part II of the study consisted of the anatomical analysis of the external transforaminal ligaments in the 180 lumbar intervertebral foramina on the MR images (1.5 T) in the sagittal plane. The diagnostic procedure was performed on 18 individuals from 18 to 25 years of age.

RESULTS

The external transforaminal ligaments were observed at all levels and from both sides in the lumbar intervertebral foramen. The presence of the superior corporotransverse ligament was found in 45.56% intervertebral foramina, while the inferior corporotransverse ligament was found in 61.67% intervertebral foramina in the MRI.

CONCLUSION

Our results confirm that external transforaminal ligaments are common structures in the intervertebral foramen. The results of this study show that the external transforaminal ligaments can be clearly visualized in MR images. It is crucial to have previous knowledge of the cadaveric specimens to recognize the transforaminal ligaments in MR images. The presence of these ligaments is clinically important because the ligaments could be the cause of nerve root compression or the low back pain syndrome.