{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T11:51:24Z","timestamp":1776167484244,"version":"3.50.1"},"reference-count":22,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T00:00:00Z","timestamp":1776124800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCM"],"abstract":"<jats:p>Background\/Objectives: The external auditory meatus (EAM) is widely used as a surrogate cranial reference point, based on its proximity to the midpoint of the nasion\u2013inion line (MNI). However, its radiographic clarity has not been thoroughly validated. This study aimed to evaluate the radiographic clarity and interobserver reproducibility of the EAM compared with the sella turcica as a control landmark. Methods: A retrospective review was performed on patients who underwent surgical correction for sagittal spinal deformity between 2021 and 2024. Preoperative standing whole-spine radiographs were analyzed. Horizontal and vertical distances from the EAM and the posterior border of the sella turcica to the MNI were measured. Radiographic clarity was categorized into three groups. Five independent neurosurgeons conducted all measurements, and interobserver reliability was assessed using the intraclass correlation coefficient with a two-way random-effects model [ICC(2,1)]. Results: The EAM was horizontally closer to the MNI (1.1 mm vs. 13.8 mm) but exhibited poorer radiographic clarity, with only 14.1% classified as single point and clear compared with 84.5% for the sella turcica. Interobserver reproducibility was lower for the EAM (ICC: 0.84 horizontal, 0.89 vertical) than for the sella turcica (0.97, 0.95). Horizontal deviation among observers was significantly greater for the EAM (major deviation 6.3 mm vs. 2.2 mm, p &lt; 0.001), whereas vertical deviation did not differ significantly. Conclusions: Although anatomically close to the MNI, the EAM demonstrated inferior radiographic clarity and reproducibility. These findings suggest that the EAM may have limitations as a cranial reference landmark.<\/jats:p>","DOI":"10.3390\/jcm15082971","type":"journal-article","created":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T10:29:08Z","timestamp":1776162548000},"page":"2971","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Radiographic Clarity of the External Auditory Meatus as a Cranial Reference Point in Spinal Deformity Patients: A Pilot Interobserver Study"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6509-1167","authenticated-orcid":false,"given":"Dongkyu","family":"Kim","sequence":"first","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dong Kyu","family":"Chin","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-1570-9116","authenticated-orcid":false,"given":"Sejun","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jaemin","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Insu","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jun-Woo","family":"Ha","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hyun Jun","family":"Jang","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kyung Hyun","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jeong Yoon","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sung Uk","family":"Kuh","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3384-5638","authenticated-orcid":false,"given":"Keun Su","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7087-8597","authenticated-orcid":false,"given":"Pyung Goo","family":"Cho","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Ajou University Medical Center, Suwon-si 16499, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1681-9734","authenticated-orcid":false,"given":"Bong Ju","family":"Moon","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, The Spine and Spinal Cord Institute, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,14]]},"reference":[{"key":"ref_1","unstructured":"Beier, G., Schuck, M., Schuller, E., and Spann, W. (2026, March 14). Determination of Physical Data of the Head. I. Center of Gravity and Moments of Inertia of Human Heads. Available online: https:\/\/apps.dtic.mil\/sti\/html\/tr\/ADA080333\/."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1007\/BF02427845","article-title":"Anatomical bases of the study of the constraints to which the cervical spine is subject in the sagittal plane A study of the center of gravity of the head","volume":"8","author":"Vital","year":"1986","journal-title":"Surg. Radiol. Anat."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"141","DOI":"10.3171\/2013.4.SPINE12838","article-title":"Cervical spine alignment, sagittal deformity, and clinical implications: A review","volume":"19","author":"Scheer","year":"2013","journal-title":"J. Neurosurg. Spine"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"372","DOI":"10.3171\/2019.3.SPINE18703","article-title":"Novel radiographic parameters for the assessment of total body sagittal alignment in adult spinal deformity patients","volume":"31","author":"Kim","year":"2019","journal-title":"J. Neurosurg. Spine"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"199","DOI":"10.1016\/j.wneu.2016.03.078","article-title":"Cranial center of mass compared to C7 plumb line alignment in adult spinal deformity","volume":"91","author":"McClendon","year":"2016","journal-title":"World Neurosurg."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1111\/joa.12586","article-title":"Standing sagittal alignment of the whole axial skeleton with reference to the gravity line in humans","volume":"230","author":"Hasegawa","year":"2017","journal-title":"J. Anat."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"484","DOI":"10.1097\/BRS.0b013e318273a1c0","article-title":"Redefining global spinal balance: Normative values of cranial center of mass from a prospective cohort of asymptomatic individuals","volume":"38","author":"Sugrue","year":"2013","journal-title":"Spine"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"575","DOI":"10.1007\/s11102-014-0609-2","article-title":"Sella turcica: An anatomical, endocrinological, and historical perspective","volume":"18","author":"Tekiner","year":"2014","journal-title":"Pituitary"},{"key":"ref_9","unstructured":"Bonneville, J.F., and Dietemann, J.L. (2012). Radiology of the Sella Turcica, Springer Science & Business Media."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/j.nec.2012.12.009","article-title":"Clinical and radiographic evaluation of the adult spinal deformity patient","volume":"24","author":"Smith","year":"2013","journal-title":"Neurosurg. Clin."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"190","DOI":"10.4184\/asj.2017.11.2.190","article-title":"Novel measurement technique for the sagittal vertical Axis and its clinical application in adult spinal deformity","volume":"11","author":"Yoshida","year":"2017","journal-title":"Asian Spine J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1121","DOI":"10.1097\/BRS.0000000000000360","article-title":"Craniopelvic alignment in elderly asymptomatic individuals: Analysis of 671 cranial centers of gravity","volume":"39","author":"Yoshida","year":"2014","journal-title":"Spine"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"662","DOI":"10.1227\/NEU.0b013e31826100c9","article-title":"The impact of standing regional cervical sagittal alignment on outcomes in posterior cervical fusion surgery","volume":"71","author":"Tang","year":"2012","journal-title":"Neurosurgery"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"269","DOI":"10.14444\/5033","article-title":"Relationship of cervical sagittal vertical alignment after sagittal balance correction in adult spinal deformity: A retrospective radiographic study","volume":"12","author":"Manoharan","year":"2018","journal-title":"Int. J. Spine Surg."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"101299","DOI":"10.1016\/j.inat.2021.101299","article-title":"Radiological comparison of the midpoint of the nasion-inion line and the external auditory canal for measuring the cranial center of the gravity-sagittal vertical axis","volume":"26","author":"Makino","year":"2021","journal-title":"Interdiscip. Neurosurg."},{"key":"ref_16","unstructured":"Dubousset, J. (1994). Three-dimensional analysis of the scoliotic deformity. The Pediatric Spine: Principles and Practice, Raven Press."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/s00586-014-3632-0","article-title":"Sagittal parameters of global cervical balance using EOS imaging: Normative values from a prospective cohort of asymptomatic volunteers","volume":"24","author":"Demezon","year":"2015","journal-title":"Eur. Spine J."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1889","DOI":"10.1007\/s00586-019-06083-1","article-title":"Sagittal balance of the spine","volume":"28","author":"Thompson","year":"2019","journal-title":"Eur. Spine J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1007\/s00586-018-5462-y","article-title":"Which parameters are relevant in sagittal balance analysis of the cervical spine? A literature review","volume":"27","author":"Ling","year":"2018","journal-title":"Eur. Spine J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"e517","DOI":"10.1016\/j.wneu.2021.04.071","article-title":"Spino cranial angle and degenerative cervical spondylolisthesis","volume":"151","author":"Wang","year":"2021","journal-title":"World Neurosurg."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1186\/s13018-021-02200-3","article-title":"Influence of SCA on clinical outcomes and cervical alignment after laminoplasty in patients with multilevel cervical spondylotic myelopathy","volume":"16","author":"Wang","year":"2021","journal-title":"J. Orthop. Surg. Res."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1411","DOI":"10.1007\/s00586-021-06825-0","article-title":"Sagittal balance of the cervical spine: A systematic review and meta-analysis","volume":"30","author":"Azimi","year":"2021","journal-title":"Eur. Spine J."}],"container-title":["Journal of Clinical Medicine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2077-0383\/15\/8\/2971\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T10:56:39Z","timestamp":1776164199000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2077-0383\/15\/8\/2971"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,14]]},"references-count":22,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["jcm15082971"],"URL":"https:\/\/doi.org\/10.3390\/jcm15082971","relation":{},"ISSN":["2077-0383"],"issn-type":[{"value":"2077-0383","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,14]]}}}