A ligament in the lumbar foramina: inverted Y ligament: an anatomic report.

OBJECTIVES The objective of this study was to investigate the ligaments in the exit zone of lumbar foramen and describe their anatomic relationships with adjacent structures. Few studies have been reported on the ligaments of foramen and the anatomic relationships on the lumbar level. The ligament described in this study is novel since it has not been reported previously. METHODS Ten male and five female cadavers were used to investigate intraforaminal area and ligaments of the lumbar level. The cadavers were filled with colored latex, and the lumbar foramen were examined under operative microscope. RESULTS A lumbar foramen branched off into two or three main passages, composed of inverted Y ligament form. The medial lower arm of Y ligament was attached to the upper and anterior surface of the superior articular process of the lower corpus vertebra. Its lateral lower arm was attached to the upper surface of the area where the lower corpus vertebra and its pedicle met, and the upper arm was attached to the lower surface of the pedicle of upper vertebra where it met with transverse process. The anatomic properties of vascular and nervous structures in foramen and the relations among them are described. CONCLUSION The ligament detected in the study was different from the other reported descriptions of foraminal ligaments. It divided the lumbar foramen into three passages. Because of its relations with adjacent structures, such as nerves and vessels, the inverted Y ligament may be an important structure for lumbar foramen. Thus, it may be an important anatomic landmark.