{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T15:26:25Z","timestamp":1793978785316,"version":"4.8.0"},"reference-count":23,"publisher":"Journal of Neurosurgery Publishing Group (JNSPG)","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,2,27]]},"abstract":"<jats:sec>\n                    <jats:title>OBJECTIVE<\/jats:title>\n                    <jats:p>The aim of this study was to investigate whether postoperative reorientation of the psoas muscle is associated with hip flexion weakness in patients who underwent posterior-only spinal realignment surgery (SRS). It was hypothesized that changes in spinal alignment might indirectly contribute to hip flexion weakness by altering the anatomical orientation and function of the psoas muscle.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>METHODS<\/jats:title>\n                    <jats:p>A total of 101 patients who underwent posterior-only SRS between 2012 and 2022 were retrospectively reviewed. Patients without evidence of intraoperative nerve injury, as confirmed by intraoperative neurophysiological monitoring, and without postoperative nerve injury, as confirmed by electromyography or nerve conduction velocity studies were included. Radiographic parameters were measured to assess psoas muscle orientation using two novel reference lines: the vertical line (VL) and the diagonal line (DL). Cross-sectional areas (CSAs) of the psoas muscle were evaluated on axial MRI at the L4\u20135 disc level. Group comparisons were conducted to assess differences in radiological parameters and CSAs between patients with and without hip flexion weakness.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>RESULTS<\/jats:title>\n                    <jats:p>Hip flexion weakness was observed in 14 patients (13.9%) and recovered in all cases with a median recovery time of 55.2 days. Postoperatively, VL and DL measurements increased significantly, and the psoas muscle CSAs decreased. Changes in VL, DL, and CSAs were significantly greater in the group with hip flexion weakness. Correlation analysis revealed significant negative associations between VL\/DL changes and CSA reduction. In multivariate regression, only VL changes remained an independent predictor of postoperative CSA reduction.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>CONCLUSIONS<\/jats:title>\n                    <jats:p>This study demonstrates that postoperative hip flexion weakness can occur after SRS, even without direct nerve or muscle injury. The findings suggest that spinal alignment changes alone might mechanically rearrange the psoas muscle, contributing to transient hip flexion weakness.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3171\/2025.10.spine25877","type":"journal-article","created":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T11:44:53Z","timestamp":1772192693000},"page":"722-730","source":"Crossref","is-referenced-by-count":0,"title":["Muscle reorientation as a novel cause of motor weakness after spinal realignment surgery: a hypothesis based on psoas muscle overstretching"],"prefix":"10.3171","volume":"44","author":[{"given":"Moon-Soo","family":"Han","sequence":"first","affiliation":[{"name":"Department of Neurosurgery, Chonnam National University Medical School & Research Institute of Medical Sciences, Gwangju, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jong-Hwan","family":"Hong","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Chonnam National University Medical School & Research Institute of Medical Sciences, Gwangju, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ji-Ho","family":"Jung","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Chonnam National University Medical School & Research Institute of Medical Sciences, Gwangju, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jung-Kil","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Neurosurgery, Chonnam National University Medical School & Research Institute of Medical Sciences, Gwangju, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1754","reference":[{"issue":"18","key":"b1","series-title":"Spine (Phila Pa 1976)","first-page":"2024","article-title":"The impact of positive sagittal balance in adult spinal deformity","volume":"30","author":"Glassman SD","year":"2005","unstructured":"Glassman SD, Bridwell K, Dimar JR, Horton W, Berven S, Schwab F. The impact of positive sagittal balance in adult spinal deformity. Spine (Phila Pa 1976). 2005;30(18):2024\u20132029. doi:10.1097\/01.brs.0000179086.30449.96"},{"issue":"3","key":"b2","series-title":"Neurospine","first-page":"467","article-title":"Thoracolumbar slope is useful parameter for evaluating healthrelated quality of life and sagittal imbalance aggravation in adult spinal deformity: a prospective observational cohort study","volume":"18","author":"Moon BJ","year":"2021","unstructured":"Moon BJ, Han MS, Kim JY, Lee JK. Thoracolumbar slope is useful parameter for evaluating healthrelated quality of life and sagittal imbalance aggravation in adult spinal deformity: a prospective observational cohort study. Neurospine. 2021;18(3):467\u2013474. doi:10.14245\/ns.2142408.204"},{"issue":"2","key":"b3","series-title":"Neurospine","first-page":"502","article-title":"Radiographic and clinical outcomes of transverse process hook placement at the proximal thoracic upper instrumented vertebra in adult spinal deformity surgery","volume":"21","author":"Lee SH","year":"2024","unstructured":"Lee SH, Raad M, Kim AH, Cohen DB, Kebaish KM. Radiographic and clinical outcomes of transverse process hook placement at the proximal thoracic upper instrumented vertebra in adult spinal deformity surgery. Neurospine. 2024;21(2):502\u2013509. doi:10.14245\/ns.2347116.558"},{"issue":"2","key":"b4","series-title":"Neurol Clin","first-page":"269","article-title":"Intraoperative monitoring for spinal surgery","volume":"40","author":"Agarwal N","year":"2022","unstructured":"Agarwal N, Shabani S, Huang J, Ben-Natan AR, Mummaneni PV. Intraoperative monitoring for spinal surgery. Neurol Clin. 2022;40(2):269\u2013281. doi:10.1016\/j.ncl.2021.11.006"},{"key":"b5","series-title":"World Neurosurg","first-page":"56","article-title":"Spinal robotics in single-position lateral surgery: a narrative review of key concepts and considerations","volume":"190","author":"Hernandez NS","year":"2024","unstructured":"Hernandez NS, Pennington Z, Patel S, Brown NJ, Broughton A, Pham MH. Spinal robotics in single-position lateral surgery: a narrative review of key concepts and considerations. World Neurosurg. 2024;190:56\u201364. doi:10.1016\/j.wneu.2024.07.030"},{"issue":"12","key":"b6","series-title":"Spine J","first-page":"1990","article-title":"Psoas weakness following oblique lateral interbody fusion surgery: a prospective observational study with an isokinetic dynamometer","volume":"22","author":"Lee S","year":"2022","unstructured":"Lee S, Kim AR, Bang WS,  Psoas weakness following oblique lateral interbody fusion surgery: a prospective observational study with an isokinetic dynamometer. Spine J. 2022;22(12):1990\u20131999. doi:10.1016\/j.spinee.2022.07.091"},{"key":"b7","series-title":"J Clin Neurosci","first-page":"165","article-title":"Radiographs assessment of changes in the psoas muscle at L4-L5 level after single-level lateral lumbar interbody fusion in patients with postoperative motor weakness","volume":"90","author":"Hiyama A","year":"2021","unstructured":"Hiyama A, Katoh H, Nomura S, Sakai D, Sato M, Watanabe M. Radiographs assessment of changes in the psoas muscle at L4-L5 level after single-level lateral lumbar interbody fusion in patients with postoperative motor weakness. J Clin Neurosci. 2021;90:165\u2013170. doi:10.1016\/j.jocn.2021.05.057"},{"issue":"9","key":"b8","series-title":"Eur Spine J","first-page":"1937","article-title":"Thoracolumbar junction orientation: its impact on thoracic kyphosis and sagittal alignment in both asymptomatic volunteers and symptomatic patients","volume":"28","author":"Moon HJ","year":"2019","unstructured":"Moon HJ, Bridwell KH, Theologis AA,  Thoracolumbar junction orientation: its impact on thoracic kyphosis and sagittal alignment in both asymptomatic volunteers and symptomatic patients. Eur Spine J. 2019;28(9):1937\u20131947. doi:10.1007\/s00586-019-06078-y"},{"key":"b9","series-title":"Man Ther","first-page":"268","article-title":"Investigating the contribution of the upper and lower lumbar spine, relative to hip motion, in everyday tasks","volume":"21","author":"Alqhtani RS","year":"2016","unstructured":"Alqhtani RS, Jones MD, Theobald PS, Williams JM. Investigating the contribution of the upper and lower lumbar spine, relative to hip motion, in everyday tasks. Man Ther. 2016;21:268\u2013273. doi:10.1016\/j.math.2015.09.014"},{"issue":"12","key":"b10","series-title":"Spine (Phila Pa 1976)","first-page":"1077","article-title":"Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study","volume":"37","author":"Schwab F","year":"2012","unstructured":"Schwab F, Ungar B, Blondel B,  Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine (Phila Pa 1976). 2012;37(12):1077\u20131082. doi:10.1097\/BRS.0b013e31823e15e2"},{"issue":"11","key":"b11","series-title":"Eur Spine J","first-page":"3644","article-title":"Global tilt: a single parameter incorporating spinal and pelvic sagittal parameters and least affected by patient positioning","volume":"25","author":"Obeid I","year":"2016","unstructured":"Obeid I, Boissi\u00e8re L, Yilgor C,  Global tilt: a single parameter incorporating spinal and pelvic sagittal parameters and least affected by patient positioning. Eur Spine J. 2016;25(11):3644\u20133649. doi:10.1007\/s00586-016-4649-3"},{"issue":"6","key":"b12","series-title":"Neurosurg Focus","first-page":"E4","article-title":"A novel classification of coronal malalignment in degenerative lumbar scoliosis for predicting postoperative coronal imbalance: a multicenter cohort study","volume":"58","author":"Qiu W","year":"2025","unstructured":"Qiu W, Sun Z, Chen Z,  A novel classification of coronal malalignment in degenerative lumbar scoliosis for predicting postoperative coronal imbalance: a multicenter cohort study. Neurosurg Focus. 2025;58(6):E4. doi:10.3171\/2025.3.FOCUS2524"},{"issue":"13","key":"b13","series-title":"J Am Acad Orthop Surg","first-page":"e620","article-title":"The iliopsoas: anatomy, clinical evaluation, and its role in hip pain in the athlete: a scoping review","volume":"32","author":"Tramer JS","year":"2024","unstructured":"Tramer JS, Holmich P, Safran MR. The iliopsoas: anatomy, clinical evaluation, and its role in hip pain in the athlete: a scoping review. J Am Acad Orthop Surg. 2024;32(13):e620\u2013e630. doi:10.5435\/JAAOS-D-23-01166"},{"issue":"6","key":"b14","series-title":"Asian Spine J","first-page":"814","article-title":"An objective and reliable method for identifying sarcopenia in lumbar spine surgery patients: using morphometric measurements on computed tomography imaging","volume":"14","author":"Tomov M","year":"2020","unstructured":"Tomov M, Alvi MA, Elminawy M,  An objective and reliable method for identifying sarcopenia in lumbar spine surgery patients: using morphometric measurements on computed tomography imaging. Asian Spine J. 2020;14(6):814\u2013820. doi:10.31616\/asj.2019.0319"},{"key":"b15","series-title":"Clin Nutr ESPEN","first-page":"410","article-title":"Muscle mass evaluation using psoas muscle mass index by computed tomography imaging in hemodialysis patients","volume":"44","author":"Ito K","year":"2021","unstructured":"Ito K, Ookawara S, Imai S,  Muscle mass evaluation using psoas muscle mass index by computed tomography imaging in hemodialysis patients. Clin Nutr ESPEN. 2021;44:410\u2013414. doi:10.1016\/j.clnesp.2021.04.029"},{"issue":"10","key":"b16","series-title":"Brain","first-page":"2838","article-title":"Aids to the investigation of peripheral nerve injuries. Medical Research Council: Nerve Injuries Research Committee. His Majesty\u2019s Stationery Office: 1942; pp. 48 (iii) and 74 figures and 7 diagrams; with aids to the examination of the peripheral nervous system By Michael O\u2019Brien for the Guarantors of Brain. Saunders Elsevier: 2010; pp. 64 and 94 Figures","volume":"133","author":"Compston A","year":"2010","unstructured":"Compston A. Aids to the investigation of peripheral nerve injuries. Medical Research Council: Nerve Injuries Research Committee. His Majesty\u2019s Stationery Office: 1942; pp. 48 (iii) and 74 figures and 7 diagrams; with aids to the examination of the peripheral nervous system By Michael O\u2019Brien for the Guarantors of Brain. Saunders Elsevier: 2010; pp. 64 and 94 Figures. Brain. 2010;133(10):2838\u20132844. doi:10.1093\/brain\/awq270"},{"key":"b17","series-title":"Braddom\u2019s Physical Medicine and Rehabilitation","first-page":"115","article-title":"Electrodiagnostic medicine","author":"Dillingham T","year":"2021","unstructured":"Dillingham T, Andary M, Dumitru D. Electrodiagnostic medicine. In: Braddom\u2019s Physical Medicine and Rehabilitation. Elsevier; 2021:115-152.e15."},{"key":"b18","article-title":"Straightforward Statistics for the Behavioral Sciences","author":"Evans JD","year":"1996","unstructured":"Evans JD. Straightforward Statistics for the Behavioral Sciences. Thomson Brooks\/Cole Publishing Co;1996."},{"issue":"19","key":"b19","series-title":"Spine (Phila Pa 1976)","first-page":"1337","article-title":"Failure in adult spinal deformity surgery: a comprehensive review of current rates, mechanisms, and prevention strategies","volume":"47","author":"Burke JF","year":"2022","unstructured":"Burke JF, Scheer JK, Lau D,  Failure in adult spinal deformity surgery: a comprehensive review of current rates, mechanisms, and prevention strategies. Spine (Phila Pa 1976). 2022;47(19):1337\u20131350. doi:10.1097\/BRS.0000000000004435"},{"issue":"3","key":"b20","series-title":"Neurosurgery","first-page":"E347","article-title":"Anterior column realignment: analysis of neurological risk and radiographic outcomes","volume":"87","author":"Saigal R","year":"2020","unstructured":"Saigal R, Akbarnia BA, Eastlack RK,  Anterior column realignment: analysis of neurological risk and radiographic outcomes. Neurosurgery. 2020;87(3):E347\u2013E354. doi:10.1093\/neuros\/nyaa064"},{"issue":"6","key":"b21","series-title":"Spine J","first-page":"1229","article-title":"Cause and effect of revisions in adult spinal deformity surgery: a multicenter study on outcomes based on etiology","volume":"25","author":"Passias PG","year":"2025","unstructured":"Passias PG, Dave P, Smith JS,  Cause and effect of revisions in adult spinal deformity surgery: a multicenter study on outcomes based on etiology. Spine J. 2025;25(6):1229\u20131235. doi:10.1016\/j.spinee.2024.12.023"},{"issue":"1570","key":"b22","series-title":"Philos Trans R Soc Lond B Biol Sci","first-page":"1466","article-title":"Skeletal muscle design to meet functional demands","volume":"366","author":"Lieber RL","year":"2011","unstructured":"Lieber RL, Ward SR. Skeletal muscle design to meet functional demands. Philos Trans R Soc Lond B Biol Sci. 2011;366(1570):1466\u20131476. doi:10.1098\/rstb.2010.0316"},{"issue":"1","key":"b23","series-title":"Sports Med","first-page":"37","article-title":"The relationship between length and active force for submaximal skeletal muscle contractions: a review","volume":"55","author":"Zimmermann HB","year":"2025","unstructured":"Zimmermann HB, Macintosh BR, Pupo JD. The relationship between length and active force for submaximal skeletal muscle contractions: a review. Sports Med. 2025;55(1):37\u201347. doi:10.1007\/s40279-024-02140-y"}],"container-title":["Journal of Neurosurgery: Spine"],"original-title":[],"link":[{"URL":"https:\/\/thejns.org\/view\/journals\/j-neurosurg-spine\/44\/5\/article-p722.xml","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/thejns.org\/downloadpdf\/journals\/j-neurosurg-spine\/44\/5\/article-p722.xml","content-type":"text\/html","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/thejns.org\/downloadpdf\/journals\/j-neurosurg-spine\/44\/5\/article-p722.xml","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,11,6]],"date-time":"2026-11-06T14:49:59Z","timestamp":1793976599000},"score":1,"resource":{"primary":{"URL":"https:\/\/thejns.org\/view\/journals\/j-neurosurg-spine\/44\/5\/article-p722.xml"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,27]]},"references-count":23,"journal-issue":{"issue":"5"},"URL":"https:\/\/doi.org\/10.3171\/2025.10.spine25877","relation":{},"ISSN":["1547-5654"],"issn-type":[{"value":"1547-5654","type":"print"}],"subject":[],"published":{"date-parts":[[2026,2,27]]}}}