{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T11:04:03Z","timestamp":1781003043578,"version":"3.54.1"},"reference-count":39,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T00:00:00Z","timestamp":1780963200000},"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: Cage subsidence after minimally invasive transforaminal lumbar interbody fusion raises revision risk and costs. Intraoperative computed tomography (CT) provides high-resolution, three-dimensional visualization of the endplate\u2013cage interface and serves as a practical\u2014though itself imperfect\u2014reference standard for early subsidence, but it is not available at all institutions. Plain X-ray is widely available and inexpensive, but lower in resolution. The clinically relevant question is therefore not whether CT and X-ray are equivalent, but rather which X-ray protrusion depth measurement most reliably identifies CT-confirmed subsidence, and whether a positive intraoperative CT meaningfully predicts later radiographic subsidence. Objective: Using intraoperative CT as reference, we aimed to (1) determine the optimal X-ray protrusion depth threshold for CT-confirmed early subsidence; (2) test whether intraoperative CT predicts late radiographic subsidence; and (3) examine how early X-ray depth relates to intervertebral disc height (IVDH) and segmental lordosis (SL) loss. Methods: In a retrospective single-surgeon cohort (March 2015\u2013July 2023), subsidence was defined as \u22652.0 mm endplate penetration on CT and measured on X-ray by parallax technique. Sensitivity, specificity, accuracy, and Cohen\u2019s \u03ba were calculated. Receiver operating characteristic (ROC) analysis evaluated X-ray depth as a continuous predictor and identified the Youden-optimal cutoff. Intraoperative CT was tested against late radiographic subsidence; no-intercept linear models estimated per-millimeter IVDH and SL loss. Results: Of 100 patients, 93 had paired imaging (mean age 66.7 years; body mass index 26.8 kg\/m2). Subsidence appeared on CT in 16.1% and on X-ray in 15.1%. X-ray showed 80.0% sensitivity, 97.4% specificity, 94.6% accuracy, and \u03ba = 0.80; ROC analysis demonstrated strong discrimination (area under the curve 0.91; 95% confidence interval 0.81\u20131.00), Youden-optimal cutoff 1.90 mm. Intraoperative CT predicted late subsidence (n = 76) with only 45.8% sensitivity and 96.2% specificity; missed cases had penetration depths indistinguishable from non-subsiders. Each 1 mm of early X-ray depth corresponded to 0.45 mm IVDH and 0.37\u00b0 SL loss. Conclusions: An X-ray protrusion depth of 2.0 mm reliably identifies CT-confirmed early subsidence, providing a preliminary diagnostic cutoff for use when CT is unavailable. Intraoperative CT is highly specific but insensitive for late subsidence; meaningful risk stratification will require additional inputs. These hypothesis-generating findings warrant prospective validation.<\/jats:p>","DOI":"10.3390\/jcm15124458","type":"journal-article","created":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T09:46:54Z","timestamp":1780998414000},"page":"4458","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Identifying an X-Ray Threshold for Cage Subsidence After Single-Level Minimally Invasive Transforaminal Lumbar Interbody Fusion: A Diagnostic Threshold Study Using Intraoperative CT as the Reference Standard"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-4095-0798","authenticated-orcid":false,"given":"Ahmet","family":"Kartal","sequence":"first","affiliation":[{"name":"Department of Neurological Surgery, Och Spine at NewYork-Presbyterian Hospital, Weill Cornell Medicine, 525 East 68th Street, Box 99, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5535-2706","authenticated-orcid":false,"given":"Gayle R.","family":"Salama","sequence":"additional","affiliation":[{"name":"Division of Neuroradiology, Department of Radiology, Weill Cornell Medicine, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-6410-9490","authenticated-orcid":false,"given":"Lawrance K.","family":"Chung","sequence":"additional","affiliation":[{"name":"Department of Neurological Surgery, Och Spine at NewYork-Presbyterian Hospital, Weill Cornell Medicine, 525 East 68th Street, Box 99, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-1028-5659","authenticated-orcid":false,"given":"Noel F.","family":"Manalil","sequence":"additional","affiliation":[{"name":"Department of Neurological Surgery, Och Spine at NewYork-Presbyterian Hospital, Weill Cornell Medicine, 525 East 68th Street, Box 99, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0894-9486","authenticated-orcid":false,"given":"Galal A.","family":"Elsayed","sequence":"additional","affiliation":[{"name":"Department of Neurological Surgery, Och Spine at NewYork-Presbyterian Hospital, Weill Cornell Medicine, 525 East 68th Street, Box 99, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roger","family":"H\u00e4rtl","sequence":"additional","affiliation":[{"name":"Department of Neurological Surgery, Och Spine at NewYork-Presbyterian Hospital, Weill Cornell Medicine, 525 East 68th Street, Box 99, New York, NY 10065, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1103","DOI":"10.14444\/8363","article-title":"Subsidence of Spinal Fusion Cages: A Systematic Review","volume":"16","author":"Parisien","year":"2022","journal-title":"Int. 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