Vol.:(0123456789) 1 3 Surgical and Radiologic Anatomy https://doi.org/10.1007/s00276-017-1963-3 ORIGINAL ARTICLE A morphological comparison of the extraforaminal ligament between the cervical and thoracic regions Pawaree Nonthasaen 1  · Hisayo Nasu 1  · Eiichiro Kagawa 1,2  · Keiichi Akita 1 Received: 3 July 2017 / Accepted: 18 December 2017 © Springer-Verlag France SAS, part of Springer Nature 2017 Abstract Purpose The current study was conducted to clarify the morphology of the extraforaminal ligament (EFL) at the cervicotho- racic junction and to compare the attachment of the EFL and the positional relation between the EFL and the spinal nerves, additionally to clarify the details within the connecting bundles at the cervicothoracic junction. Materials and methods The EFLs from the 4th cervical to the 4th thoracic vertebrae were dissected in 56 sides of 28 Japa- nese cadavers (11 males, 17 females). The range of age was 62.0–99.0 years. In addition, connecting bundles were analyzed by histological examination. Results Ventral to the spinal nerve, the capsulotransverse ligament (CTL), transforaminal ligament (TFL) and the ligament between the 7th cervical vertebra and the 1st rib were attached to the transverse process and rib. The EFL ventral to the 1st thoracic nerve was not observed in all sides. Dorsal to the spinal nerve, the anterior part of the superior costotransverse ligament (ASCL) and the ligament homologous to the ASCL were attached to the transverse process and rib. The superior radiating ligament (SRL) and the ligament homologous to the SRL were identifed. The connecting bundles identifed between the 7th cervical and the 1st thoracic nerve were histologically confrmed to consist of nerves and vessels. Conclusions The EFLs at the cervicothoracic junction were found to be homologous. The connecting bundles were observed between the 7th cervical and the 1st thoracic nerve. Interestingly, the 1st thoracic level alone might be a unique level at the cervicothoracic junction. Keywords Extraforaminal ligament · Cervicothoracic junction · Transforaminal ligament · Superior costotransverse ligament · Capsulotransverse ligament · Superior radiating ligament Abbreviations C 5 Body of the 5th cervical vertebra C 6 Body of the 6th cervical vertebra C 7 Body of the 7th cervical vertebra T 1 Body of the 1st thoracic vertebra T 2 Body of the 2nd thoracic vertebra TPc 6 The transverse process of the 6th cervical vertebra TPc 7 The transverse process of the 7th cervical vertebra TPt 1 The transverse process of the 1st thoracic vertebra TPt 2 The transverse process of the 2nd thoracic vertebra Nc 5 The 5th cervical nerve Nc 6 The 6th cervical nerve Nc 7 The 7th cervical nerve Nc 8 The 8th cervical nerve Nt 1 The 1st thoracic nerve Nt 2 The 2nd thoracic nerve Introduction The extraforaminal ligament (EFL) was defned by Amonoo- Kuof et al. [2] as a ligament related to the external aspect of the intervertebral foramen. There have been many researches about the EFL in the lumbar region [2, 3, 15, 18, 20, 21, 23, 32]. Recently, some studies about the EFL in the cervical [4, 17, 19, 28] or thoracic [13, 16] regions have been con- ducted. Kraan et al. [15–17] investigated the EFLs in the cervical, thoracic, and lumbar segment levels and described the lengths, widths, and angles for all ligaments were similar * Keiichi Akita akita.fana@tmd.ac.jp 1 Department of Clinical Anatomy, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan 2 JA Kyosai Research Institute, JA Kyosai Building 5th Floor, 2-7-9 Hirakawacho, Chiyoda-ku, Tokyo 102-0093, Japan