{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T14:42:07Z","timestamp":1787755327741,"version":"build-2784847793"},"reference-count":29,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"2","license":[{"start":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T00:00:00Z","timestamp":1775001600000},"content-version":"unspecified","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["lww.com","ovid.com"],"crossmark-restriction":true},"short-container-title":[],"abstract":"\n Background:<\/jats:title>\n Functional safe zones for implant positioning in total hip arthroplasty (THA) have primarily been evaluated in static postures. However, no studies have examined sit-to-stand movements, which carry a high risk of posterior dislocation. In this study, we recorded sit-to-stand motion post-THA using a dynamic x-ray system to analyze pelvic tilt and hip flexion angles during sitting and standing, including sex differences and the influence of sitting posture, and identify preoperative factors associated with standing alignment.<\/jats:p>\n <\/jats:sec>\n \n Methods:<\/jats:title>\n We retrospectively evaluated 118 patients 6 months post-THA. Sequential lateral radiographs were used to capture maximal anterior pelvic tilt during standing. The sacral slope (SS) and pelvic\u2013femoral angle (PFA) were measured; changes from the sitting position were calculated. Sex differences and correlations with sitting posture were assessed, and regression analyses identified predictors of standing SS and PFA.<\/jats:p>\n <\/jats:sec>\n \n Results:<\/jats:title>\n \n The mean \u0394SS was 29.6\u00b0 \u00b1 8.7\u00b0, and the mean \u0394PFA was 24.8\u00b0 \u00b1 8.7\u00b0. \u0394SS showed no sex difference (p = 0.331), whereas \u0394PFA was larger in women (25.8\u00b0 \u00b1 8.6\u00b0) than in men (20.5\u00b0 \u00b1 8.3\u00b0, p = 0.011). \u0394SS correlated negatively with sitting SS (r = \u22120.550,\n p<\/jats:italic>\n < 0.001), and \u0394PFA correlated positively with sitting PFA (r = 0.478,\n p<\/jats:italic>\n < 0.001). Age, preoperative hip flexion, and pelvic incidence\u2013lumbar lordosis (PI-LL) moderately predicted standing PFA.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion:<\/jats:title>\n During sit-to-stand motions post-THA, the pelvis tilted anteriorly by approximately 30\u00b0, and the hip flexed by approximately 25\u00b0, influenced by sex and sitting posture. Standing hip flexion was affected by age, preoperative hip flexion angle, and PI-LL.<\/jats:p>\n <\/jats:sec>\n \n Level of Evidence:<\/jats:title>\n \n Diagnostic\n Level III<\/jats:underline>\n . See Instructions for Authors for a complete description of levels of evidence.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.2106\/jbjs.oa.26.00085","type":"journal-article","created":{"date-parts":[[2026,6,15]],"date-time":"2026-06-15T18:06:10Z","timestamp":1781546770000},"update-policy":"https:\/\/doi.org\/10.1097\/lww.0000000000001000","source":"Crossref","is-referenced-by-count":0,"title":["Dynamic Radiography Analysis of Functional Safe Zone During Sit-to-Stand Motion After Total Hip Arthroplasty and Its Association with Preoperative Factors"],"prefix":"10.2106","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3280-6370","authenticated-orcid":false,"given":"Hiroki","family":"Shimodaira","sequence":"first","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1146-3476","authenticated-orcid":false,"given":"Keiji","family":"Tensho","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Marunouchi Hospital, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7744-3967","authenticated-orcid":false,"given":"Suguru","family":"Koyama","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5698-549X","authenticated-orcid":false,"given":"Daiki","family":"Kumaki","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-6461-7526","authenticated-orcid":false,"given":"Yusuke","family":"Maezumi","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-3782-964X","authenticated-orcid":false,"given":"Yusuke","family":"Koyama","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-7431-6425","authenticated-orcid":false,"given":"Manabu","family":"Takei","sequence":"additional","affiliation":[{"name":"Radiology Division, Shinshu University Hospital, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2890-2183","authenticated-orcid":false,"given":"Hiroshi","family":"Horiuchi","sequence":"additional","affiliation":[{"name":"Department of Rehabilitation, Shinshu University Hospital, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5227-2900","authenticated-orcid":false,"given":"Jun","family":"Takahashi","sequence":"additional","affiliation":[{"name":"Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"276","published-online":{"date-parts":[[2026,4]]},"reference":[{"issue":"2","key":"R1-20260615","doi-asserted-by":"crossref","first-page":"217","DOI":"10.2106\/00004623-197860020-00014","article-title":"Dislocations after total hip-replacement 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Arthroplasty"},{"issue":"4","key":"R5-20260615","doi-asserted-by":"crossref","first-page":"706","DOI":"10.1016\/j.arth.2022.05.016","article-title":"High prevalence of spinopelvic risk factors in patients with post-operative hip dislocations","volume":"38","author":"Vigdorchik","year":"2023","journal-title":"J Arthroplasty"},{"issue":"1","key":"R6-20260615","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1097\/CORR.0000000000001923","article-title":"A modeling study of a patient-specific safe zone for THA: calculation, validation, and key factors based on standing and sitting sagittal pelvic tilt","volume":"480","author":"Tang","year":"2022","journal-title":"Clin Orthop Relat Res."},{"issue":"4","key":"R7-20260615","doi-asserted-by":"crossref","first-page":"690","DOI":"10.1097\/CORR.0000000000002382","article-title":"What changes in pelvic sagittal tilt occur 20 years after THA?","volume":"481","author":"Hamada","year":"2023","journal-title":"Clin Orthop Relat 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J."},{"issue":"4","key":"R11-20260615","doi-asserted-by":"crossref","first-page":"577","DOI":"10.1016\/S0021-9290(02)00232-4","article-title":"Kinematics, kinetics, and finite element analysis of commonplace maneuvers at risk for total hip dislocation","volume":"36","author":"Nadzadi","year":"2003","journal-title":"J Biomech."},{"issue":"7","key":"R12-20260615","doi-asserted-by":"crossref","first-page":"S57","DOI":"10.1016\/j.arth.2019.01.012","article-title":"A preoperative workup of a \u201chip-spine\u201d total hip arthroplasty patient: a simplified approach to a complex problem","volume":"34","author":"Luthringer","year":"2019","journal-title":"J Arthroplasty"},{"issue":"4","key":"R13-20260615","doi-asserted-by":"crossref","first-page":"818","DOI":"10.1097\/CORR.0000000000002106","article-title":"Small random angular variations in pelvic tilt and lower extremity can cause error in static image-based preoperative hip arthroplasty planning: a computer modeling study","volume":"480","author":"Eslam","year":"2022","journal-title":"Clin Orth Relat Res."},{"issue":"6","key":"R14-20260615","doi-asserted-by":"crossref","first-page":"S123","DOI":"10.1016\/j.jse.2022.12.023","article-title":"Variation in scapulohumeral rhythm on dynamic radiography in pathologic shoulders: a novel diagnostic tool","volume":"32","author":"Xiao","year":"2023","journal-title":"J Shoulder Elbow Surg."},{"issue":"6","key":"R15-20260615","doi-asserted-by":"crossref","first-page":"871","DOI":"10.1016\/j.resinv.2021.07.005","article-title":"Two cases of chronic obstructive pulmonary disease evaluated by dynamic-ventilatory digital radiography for pulmonary function and assessment of treatment efficacy","volume":"59","author":"Ohkura","year":"2021","journal-title":"Respir Invest."},{"issue":"8","key":"R16-20260615","doi-asserted-by":"crossref","first-page":"1788","DOI":"10.1007\/s11999-016-4787-2","article-title":"Does degenerative lumbar spine disease influence femoroacetabular flexion in patients undergoing total hip arthroplasty?","volume":"474","author":"Esposito","year":"2016","journal-title":"Clin Orthop Relat Res."},{"issue":"4","key":"R17-20260615","doi-asserted-by":"crossref","first-page":"482","DOI":"10.1177\/11207000231223706","article-title":"\u201cStuck in the middle\u201d: the missing Lumbosacral link in total hip arthroplasty","volume":"34","author":"Scanlon","year":"2024","journal-title":"HIP Int."},{"key":"R18-20260615","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1016\/j.jor.2024.08.008","article-title":"Spinopelvic alignment and precise cup placement in total hip arthroplasty - a systematic review","volume":"60","author":"Ram Sudhan","year":"2025","journal-title":"J Orthop"},{"issue":"8","key":"R19-20260615","doi-asserted-by":"crossref","first-page":"3931","DOI":"10.1007\/s00590-024-04079-2","article-title":"Dynamic change of acetabular component position in total hip arthroplasty based on the spinopelvic classification: a prospective radiographic study","volume":"34","author":"Hagiwara","year":"2024","journal-title":"Eur J Orthop Surg Traumatol."},{"key":"R20-20260615","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1097\/01.blo.0000238862.92356.45","article-title":"Functional pelvic orientation measured from lateral standing and sitting radiographs","volume":"453","author":"DiGioia","year":"2006","journal-title":"Clin Orthop Relat Res."},{"issue":"4","key":"R21-20260615","doi-asserted-by":"crossref","first-page":"1036","DOI":"10.1016\/j.arth.2019.11.020","article-title":"Lumbar spine degeneration and flatback deformity alter sitting-standing spinopelvic mechanics-implications for total hip arthroplasty","volume":"35","author":"Buckland","year":"2020","journal-title":"J Arthroplasty"},{"issue":"6","key":"R22-20260615","doi-asserted-by":"crossref","first-page":"1910","DOI":"10.1016\/j.arth.2016.12.039","article-title":"Total hip arthroplasty in the spinal deformity population: does degree of sagittal deformity affect rates of safe zone placement, instability, or revision?","volume":"32","author":"DelSole","year":"2017","journal-title":"J Arthroplasty"},{"issue":"1","key":"R23-20260615","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.arth.2018.10.034","article-title":"Functional safe zone is superior to the Lewinnek safe zone for total hip arthroplasty: why the Lewinnek safe zone is not always predictive of stability","volume":"34","author":"Tezuka","year":"2019","journal-title":"J Arthroplasty"},{"issue":"6","key":"R24-20260615","doi-asserted-by":"crossref","first-page":"S255","DOI":"10.1016\/j.arth.2020.02.029","article-title":"How can patients with mobile hips and stiff lumbar spines be identified prior to total hip arthroplasty? A prospective, diagnostic cohort study","volume":"35","author":"Innmann","year":"2020","journal-title":"J Arthroplasty"},{"issue":"7","key":"R25-20260615","first-page":"609","article-title":"Biomechanical analysis of the sit-to-stand motion in elderly persons","volume":"73","author":"Millington","year":"1992","journal-title":"Arch Phys Med Rehabil."},{"issue":"3","key":"R26-20260615","doi-asserted-by":"crossref","first-page":"77","DOI":"10.14245\/kjs.2017.14.3.77","article-title":"Pelvic incidence can be changed not only by age and sex, but also by posture used during imaging","volume":"14","author":"Moon","year":"2017","journal-title":"Korean J Spine"},{"issue":"17","key":"R27-20260615","doi-asserted-by":"crossref","first-page":"1828","DOI":"10.1097\/BRS.0b013e3181a13c08","article-title":"Sagittal plane considerations and the pelvis in the adult patient","volume":"34","author":"Schwab","year":"2009","journal-title":"Spine"},{"issue":"11","key":"R28-20260615","doi-asserted-by":"crossref","first-page":"991","DOI":"10.2106\/JBJS.19.00300","article-title":"The effects of pelvic incidence in the functional anatomy of the hip joint","volume":"102","author":"Ike","year":"2020","journal-title":"J Bone Jt Surg."},{"issue":"12","key":"R29-20260615","first-page":"3087","article-title":"Impact of spinal alignment and stiffness on impingement after total hip arthroplasty: a radiographic study of pre- and post-operative spinopelvic alignment","volume":"29","author":"Hagiwara","year":"2020","journal-title":"Eur Spine J."}],"container-title":["JBJS Open Access"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.ovid.com\/10.2106\/JBJS.OA.26.00085","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T13:41:19Z","timestamp":1787751679000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.ovid.com\/10.2106\/JBJS.OA.26.00085"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4]]},"references-count":29,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026]]}},"URL":"https:\/\/doi.org\/10.2106\/jbjs.oa.26.00085","relation":{},"ISSN":["2472-7245"],"issn-type":[{"value":"2472-7245","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4]]}}}