{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T13:14:55Z","timestamp":1783602895605,"version":"3.55.0"},"reference-count":25,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T00:00:00Z","timestamp":1782432000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Bioengineering"],"abstract":"<jats:p>Background: Mechanical complications remain a concern after vertebral body replacement (VBR), especially during rehabilitation. Yet exercise prescription is often guided by body posture or single loading measures. This study characterized mechanical demands during rehabilitation exercises after VBR and examined the effects of posture and postoperative time. Methods: Telemetric in vivo load data from instrumented VBRs in the OrthoLoad database were analyzed. A total of 119 trials across 21 exercises, performed in supine, prone, seated, and standing positions, were collected from five patients over 0.1\u201363 postoperative months. Mechanical demand was quantified across six biomechanical domains and integrated into a composite SafetyIndex. Posture- and time-related effects were assessed using linear mixed-effects models. Worst-case demand was defined as the 95th percentile of SafetyIndex values. Results: SafetyIndex showed a right-skewed distribution (median 8.5, IQR 3.7\u201314.1), with marked inter-exercise variability. Composite SafetyIndex did not differ between postures (all p &gt; 0.13). However, posture-dependent effects emerged at the domain level: peak shear ratio was greater in prone than in sitting, standing, and supine positions (all p &lt; 0.05); peak force was greater in standing than prone (p = 0.007 and p = 0.013 in unadjusted and adjusted models); and peak resultant moment was smaller in supine than prone (p = 0.036 and p = 0.046). Postoperative time was positively associated with peak force (\u03b2 = +0.40 %BW\/month, p = 0.042), peak resultant moment (\u03b2 = +0.025 Nm\/month, p &lt; 0.001), and SafetyIndex (\u03b2 = +0.25\/month, p = 0.011), but not peak shear ratio (p = 0.879). Worst-case SafetyIndex_P95 values ranged from 0.6 to 85.0, with stable ranking across percentile thresholds (Spearman\u2019s \u03c1 = 0.995\u20130.997). Conclusions: Mechanical demand after VBR is task-specific and domain-dependent and cannot be inferred from posture alone. Axial and bending-related components increased over postoperative time, whereas shear-related loading remained task-dependent.<\/jats:p>","DOI":"10.3390\/bioengineering13070753","type":"journal-article","created":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T05:58:04Z","timestamp":1782799084000},"page":"753","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["In Vivo Mechanical Demands on Vertebral Body Replacements During Rehabilitation Exercises: A Multidimensional and Longitudinal Analysis"],"prefix":"10.3390","volume":"13","author":[{"given":"Maria Cesarina","family":"May","sequence":"first","affiliation":[{"name":"IRCCS Azienda Ospedaliera Metropolitana, 16132 Genoa, Italy"},{"name":"Department of Integrated Surgical Diagnostic Sciences (DISC), Orthopedic Clinic, University of Genoa, 16132 Genoa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2578-1133","authenticated-orcid":false,"given":"Andrea","family":"Zanirato","sequence":"additional","affiliation":[{"name":"IRCCS Azienda Ospedaliera Metropolitana, 16132 Genoa, Italy"},{"name":"Department of Integrated Surgical Diagnostic Sciences (DISC), Orthopedic Clinic, University of Genoa, 16132 Genoa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0825-2707","authenticated-orcid":false,"given":"Luca","family":"Puce","sequence":"additional","affiliation":[{"name":"Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DINOGMI), University of Genoa, 16132 Genoa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matteo","family":"Formica","sequence":"additional","affiliation":[{"name":"IRCCS Azienda Ospedaliera Metropolitana, 16132 Genoa, Italy"},{"name":"Department of Integrated Surgical Diagnostic Sciences (DISC), Orthopedic Clinic, University of Genoa, 16132 Genoa, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8517-0057","authenticated-orcid":false,"given":"Carlo","family":"Biz","sequence":"additional","affiliation":[{"name":"Department of Orthopedics and Orthopedic Oncology, University of Padova, 35128 Padova, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9617-9882","authenticated-orcid":false,"given":"Pietro","family":"Ruggieri","sequence":"additional","affiliation":[{"name":"Department of Orthopedics and Orthopedic Oncology, University of Padova, 35128 Padova, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1412","DOI":"10.1016\/j.wneu.2015.06.072","article-title":"Corpectomy and Vertebral Body Reconstruction with Expandable Cage Placement and Osteosynthesis via the Single-Stage Posterior Approach: A Retrospective Series of 34 Patients with Thoracic and Lumbar Spine Vertebral Body Tumors","volume":"84","author":"Joubert","year":"2015","journal-title":"World Neurosurg."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1442","DOI":"10.3390\/curroncol29030121","article-title":"Complication Avoidance in Surgical Management of Vertebral Column Tumors","volume":"29","author":"Feler","year":"2022","journal-title":"Curr. Oncol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"828","DOI":"10.1186\/s13018-023-04310-6","article-title":"A Novel Artificial Vertebral Implant with Gyroid Porous Structures for Reducing the Subsidence and Mechanical Failure Rate after Vertebral Body Replacement","volume":"18","author":"Shang","year":"2023","journal-title":"J. Orthop. Surg. Res."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"179","DOI":"10.17816\/2311-2905-17750","article-title":"Subsidence of Vertebral Body Replacement Prostheses in Spinal Tumors: A Systematic Review","volume":"31","author":"Zaborovskii","year":"2025","journal-title":"Traumatol. Orthop. Russ."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"537","DOI":"10.1227\/01.NEU.0000325260.00628.DC","article-title":"Vertebral Body Replacement Systems with Expandable Cages in the Treatment of Various Spinal Pathologies: A Prospectively Followed Case Series of 60 Patients","volume":"63","author":"Arts","year":"2008","journal-title":"Neurosurgery"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"222","DOI":"10.14444\/8207","article-title":"Anterior 1\u20132 Level Cervical Corpectomy and Fusion for Degenerative Cervical Disease: A Retrospective Study with Lordotic Porous Tantalum Cages. Long-Term Changes in Sagittal Alignment and Their Clinical and Radiological Implications after Cage Subsidence","volume":"16","year":"2022","journal-title":"Int. J. Spine Surg."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1253","DOI":"10.1007\/s00402-011-1284-7","article-title":"Biomechanical Comparison of the End Plate Design of Three Vertebral Body Replacement Systems","volume":"131","author":"Penzkofer","year":"2011","journal-title":"Arch. Orthop. Trauma Surg."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"632","DOI":"10.1016\/j.jbmt.2025.06.038","article-title":"Effects of Musculoskeletal Rehabilitation in Patients with Lumbosacral Transitional Vertebra: A Systematic Review","volume":"44","author":"Guilherme","year":"2025","journal-title":"J. Bodyw. Mov. Ther."},{"key":"ref_9","first-page":"CD009644","article-title":"Rehabilitation following Surgery for Lumbar Spinal Stenosis","volume":"12","author":"McGregor","year":"2013","journal-title":"Cochrane Database Syst. Rev."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1016\/j.medengphy.2006.06.012","article-title":"An Instrumented Implant for Vertebral Body Replacement That Measures Loads in the Anterior Spinal Column","volume":"29","author":"Rohlmann","year":"2007","journal-title":"Med. Eng. Phys."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1170","DOI":"10.1097\/BRS.0b013e3181722d52","article-title":"Loads on a Telemeterized Vertebral Body Replacement Measured in Two Patients","volume":"33","author":"Rohlmann","year":"2008","journal-title":"Spine"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"560","DOI":"10.1016\/j.jbiomech.2015.01.007","article-title":"In Vivo Implant Forces Acting on a Vertebral Body Replacement during Upper Body Flexion","volume":"48","author":"Dreischarf","year":"2015","journal-title":"J. Biomech."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"511","DOI":"10.1016\/j.jbiomech.2012.10.022","article-title":"Lifting up and Laying down a Weight Causes High Spinal Loads","volume":"46","author":"Rohlmann","year":"2013","journal-title":"J. Biomech."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1016\/j.jbiomech.2015.01.011","article-title":"Spinal Loads as Influenced by External Loads: A Combined In Vivo and In Silico Investigation","volume":"48","author":"Zander","year":"2015","journal-title":"J. Biomech."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.jbiomech.2016.11.060","article-title":"Comparison of In Vivo Measured Loads in Knee, Hip and Spinal Implants during Level Walking","volume":"51","author":"Damm","year":"2017","journal-title":"J. Biomech."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2015","DOI":"10.1097\/BRS.0b013e3181d55d52","article-title":"Different Arm Positions and the Shape of the Thoracic Spine Can Explain Contradictory Results in the Literature about Spinal Loads for Sitting and Standing","volume":"35","author":"Dreischarf","year":"2010","journal-title":"Spine"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1972","DOI":"10.1016\/j.jbiomech.2005.03.028","article-title":"Spine Biomechanics","volume":"38","author":"Adams","year":"2005","journal-title":"J. Biomech."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"817","DOI":"10.1080\/001401398186667","article-title":"Spine Loading during Asymmetric Lifting Using One versus Two Hands","volume":"41","author":"Marras","year":"1998","journal-title":"Ergonomics"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1016\/j.clinbiomech.2007.09.011","article-title":"Loads on a Telemeterized Vertebral Body Replacement Measured in Three Patients within the First Postoperative Month","volume":"23","author":"Rohlmann","year":"2008","journal-title":"Clin. Biomech."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.clinbiomech.2013.03.010","article-title":"Effect of an Orthosis on the Loads Acting on a Vertebral Body Replacement","volume":"28","author":"Rohlmann","year":"2013","journal-title":"Clin. Biomech."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"109517","DOI":"10.1016\/j.jbiomech.2019.109517","article-title":"In Vivo Hip and Lumbar Spine Implant Loads during Activities in Forward Bent Postures","volume":"102","author":"Damm","year":"2020","journal-title":"J. Biomech."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1007\/s00586-013-3087-8","article-title":"In Vivo Measurements of the Effect of Whole Body Vibration on Spinal Loads","volume":"23","author":"Rohlmann","year":"2014","journal-title":"Eur. Spine J."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2342","DOI":"10.1016\/j.jbiomech.2013.07.014","article-title":"What Have We Learned from Finite Element Model Studies of Lumbar Intervertebral Discs in the Past Four Decades?","volume":"46","author":"Schmidt","year":"2013","journal-title":"J. Biomech."},{"key":"ref_24","unstructured":"Bergmann, G., and Damm, P. (2008). OrthoLoad, Berlin Institute of Health at Charit\u00e9\u2014Universit\u00e4tsmedizin Berlin. Available online: http:\/\/www.OrthoLoad.com."},{"key":"ref_25","unstructured":"(1997). Mechanical Vibration and Shock\u2014Evaluation of Human Exposure to Whole-Body Vibration\u2014Part 1: General Requirements (Standard No. ISO 2631-1:1997)."}],"container-title":["Bioengineering"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-5354\/13\/7\/753\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T12:29:03Z","timestamp":1783600143000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-5354\/13\/7\/753"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,26]]},"references-count":25,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["bioengineering13070753"],"URL":"https:\/\/doi.org\/10.3390\/bioengineering13070753","relation":{},"ISSN":["2306-5354"],"issn-type":[{"value":"2306-5354","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,26]]}}}