The Morphology and Clinical Significance of the Extraforaminal Ligaments at the Cervical Level

STUDY DESIGN: A dissection-based study of 10 embalmed human cadavers. OBJECTIVE: The purpose of this study was to describe the extraforaminal ligaments in the exit regions of the T1-T12 intervertebral foramina and to discuss their possible clinical significance. SUMMARY OF BACKGROUND DATA: The ligaments at the lumbar intervertebral foramina have been well studied. However, detailed descriptions of the extraforaminal ligaments at the T1-T12 levels are lacking. METHODS: Two hundred forty T1-T12 intervertebral foramina from 10 embalmed cadavers were studied. The presence of the ligament was noted. The quantity, morphology, distributions, proximal attachments, distal attachments, and spatial orientations of the extraforaminal ligaments in the exit regions of the T1-T12 intervertebral foramina were examined. The length, width, diameter, and thickness of the ligaments were measured with digital calipers by three independent investigators. RESULTS: A total of 564 extraforaminal ligaments were identified in the 229 intervertebral foramina; no ligaments were found in the other 11 intervertebral foramina, resulting in an occurrence rate of extraforaminal ligaments of 95.42%. One hundred thirty-six (24.11%) of the extraforaminal ligaments were radiating ligaments, and 428 (75.89%) were transforaminal ligaments. Radiating ligaments had a tendency to be abundant at T1 and T9-T12 and sparse at T2-T8. There were 245 (43.44%) ligaments at the anterior aspect of the exit regions of the intervertebral foramina, 225 (39.89%) ligaments at the posterior aspect, 64 (11.35%) ligaments at the inferior aspect, and 30 (5.32%) ligaments at the superior aspect. CONCLUSION: In the exit region of thoracic intervertebral foramina, there are two types of extraforaminal ligaments. They may serve as a protective mechanism against traction and play a role in the positioning of the nerves in the intervertebral foramen. Transforaminal ligaments may be an underlying cause of rib or chest pain after thoracic fracture and may be of clinical importance to surgeons. LEVEL OF EVIDENCE: N/A.