{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T09:23:03Z","timestamp":1771492983528,"version":"3.50.1"},"reference-count":27,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2024,6,13]],"date-time":"2024-06-13T00:00:00Z","timestamp":1718236800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000005","name":"Department of Defense","doi-asserted-by":"publisher","award":["W81XWH-22-1-0836"],"award-info":[{"award-number":["W81XWH-22-1-0836"]}],"id":[{"id":"10.13039\/100000005","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000005","name":"Department of Defense","doi-asserted-by":"publisher","award":["T32 AR007505"],"award-info":[{"award-number":["T32 AR007505"]}],"id":[{"id":"10.13039\/100000005","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health","award":["W81XWH-22-1-0836"],"award-info":[{"award-number":["W81XWH-22-1-0836"]}]},{"name":"National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health","award":["T32 AR007505"],"award-info":[{"award-number":["T32 AR007505"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>For individuals with spinal cord injuries (SCIs) above the midthoracic level, a common complication is the partial or complete loss of trunk stability in the seated position. Functional neuromuscular stimulation (FNS) can restore seated posture and other motor functions after paralysis by applying small electrical currents to the peripheral motor nerves. In particular, the Networked Neuroprosthesis (NNP) is a fully implanted, modular FNS system that is also capable of capturing information from embedded accelerometers for measuring trunk tilt for feedback control of stimulation. The NNP modules containing the accelerometers are located in the body based on surgical constraints. As such, their exact orientations are generally unknown and cannot be easily assessed. In this study, a method for estimating trunk tilt that employed the Gram\u2013Schmidt method to reorient acceleration signals to the anatomical axes of the body was developed and deployed in individuals with SCI using the implanted NNP system. An anatomically realistic model of a human trunk and five accelerometer sensors was developed to verify the accuracy of the reorientation algorithm. Correlation coefficients and root mean square errors (RMSEs) were calculated to compare target trunk tilt estimates and tilt estimates derived from simulated accelerometer signals under a variety of conditions. Simulated trunk tilt estimates with correlation coefficients above 0.92 and RMSEs below 5\u00b0 were achieved. The algorithm was then applied to accelerometer signals from implanted sensors installed in three NNP recipients. Error analysis was performed by comparing the correlation coefficients and RMSEs derived from trunk tilt estimates calculated from implanted sensor signals to those calculated via motion capture data, which served as the gold standard. NNP-derived trunk tilt estimates exhibited correlation coefficients between 0.80 and 0.95 and RMSEs below 13\u00b0 for both pitch and roll in most cases. These findings suggest that the algorithm is effective at estimating trunk tilt with the implanted sensors of the NNP system, which implies that the method may be appropriate for extracting feedback signals for control systems for seated stability with NNP technology for individuals who have reduced control of their trunk due to paralysis.<\/jats:p>","DOI":"10.3390\/s24123816","type":"journal-article","created":{"date-parts":[[2024,6,13]],"date-time":"2024-06-13T06:23:11Z","timestamp":1718259791000},"page":"3816","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Anatomical Registration of Implanted Sensors Improves Accuracy of Trunk Tilt Estimates with a Networked Neuroprosthesis"],"prefix":"10.3390","volume":"24","author":[{"given":"Matthew W.","family":"Morrison","sequence":"first","affiliation":[{"name":"Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA"},{"name":"Motion Study Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA"}]},{"given":"Michael E.","family":"Miller","sequence":"additional","affiliation":[{"name":"Motion Study Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA"}]},{"given":"Lisa M.","family":"Lombardo","sequence":"additional","affiliation":[{"name":"Motion Study Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0984-5803","authenticated-orcid":false,"given":"Ronald J.","family":"Triolo","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA"},{"name":"Motion Study Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5737-1708","authenticated-orcid":false,"given":"Musa L.","family":"Audu","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA"},{"name":"Motion Study Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA"}]}],"member":"1968","published-online":{"date-parts":[[2024,6,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1276","DOI":"10.1016\/S0003-9993(03)00200-4","article-title":"The relationship between sitting stability and functional performance in patients with paraplegia","volume":"84","author":"Chen","year":"2003","journal-title":"Arch. Phys. Med. Rehabil."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1186\/1743-0003-12-8","article-title":"A neuroprosthesis for control of seated balance after spinal cord injury","volume":"12","author":"Audu","year":"2015","journal-title":"J. NeuroEng. Rehabil."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1089\/neu.2004.21.1371","article-title":"Targeting Recovery: Priorities of the Spinal Cord-Injured Population","volume":"21","author":"Anderson","year":"2004","journal-title":"J. Neurotrauma"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1682\/JRRD.2011.11.0213","article-title":"Functional priorities, assistive technology, and brain-computer interfaces after spinal cord injury","volume":"50","author":"Collinger","year":"2013","journal-title":"J. Rehabil. Res. Dev."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"998","DOI":"10.1038\/s41393-020-0457-z","article-title":"Recovery target priorities of people with spinal cord injuries in Korea compared with other countries: A survey","volume":"58","author":"Huh","year":"2020","journal-title":"Spinal Cord"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1146\/annurev.bioeng.6.040803.140103","article-title":"Functional Electrical Stimulation for Neuromuscular Applications","volume":"7","author":"Peckham","year":"2005","journal-title":"Annu. Rev. Biomed. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1038\/sj.sc.3101864","article-title":"Gait training regimen for incomplete spinal cord injury using functional electrical stimulation","volume":"44","author":"Thrasher","year":"2006","journal-title":"Spinal Cord"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"202","DOI":"10.1016\/S0090-3019(98)00074-3","article-title":"Functional neuromuscular stimulator for short-distance ambulation by certain thoracic-level spinal-cord-injured paraplegics","volume":"50","author":"Graupe","year":"1998","journal-title":"Surg. Neurol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"117","DOI":"10.1186\/s12984-021-00912-5","article-title":"Selective neural stimulation methods improve cycling exercise performance after spinal cord injury: A case series","volume":"18","author":"Gelenitis","year":"2021","journal-title":"J. NeuroEng. Rehabil."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1109\/TNSRE.2004.827222","article-title":"The effects of trunk stimulation on bimanual seated workspace","volume":"12","author":"Kukke","year":"2004","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1766","DOI":"10.1016\/j.apmr.2013.02.023","article-title":"Effects of Stimulating Hip and Trunk Muscles on Seated Stability, Posture, and Reach After Spinal Cord Injury","volume":"94","author":"Triolo","year":"2013","journal-title":"Arch. Phys. Med. Rehabil."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Tharu, N.S., Wong, A.Y.L., and Zheng, Y.-P. (2023). Neuromodulation for recovery of trunk and sitting functions following spinal cord injury: A comprehensive review of the literature. Bioelectron. Med., 9.","DOI":"10.1186\/s42234-023-00113-6"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1138","DOI":"10.1109\/TNSRE.2014.2324825","article-title":"Miniature Low-Power Inertial Sensors: Promising Technology for Implantable Motion Capture Systems","volume":"22","author":"Lambrecht","year":"2014","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"747","DOI":"10.1682\/JRRD.2013.09.0200","article-title":"Feasibility of closed-loop controller for righting seated posture after spinal cord injury","volume":"51","author":"Murphy","year":"2014","journal-title":"J. Rehabil. Res. Dev."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1186\/s12984-022-01113-4","article-title":"Feedback control of upright seating with functional neuromuscular stimulation during a reaching task after spinal cord injury: A feasibility study","volume":"19","author":"Friederich","year":"2022","journal-title":"J. NeuroEng. Rehabil."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1222174","DOI":"10.3389\/fresc.2023.1222174","article-title":"Stabilizing leaning postures with feedback controlled functional neuromuscular stimulation after trunk paralysis","volume":"4","author":"Friederich","year":"2023","journal-title":"Front. Rehabil. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"81","DOI":"10.1049\/htl.2019.0113","article-title":"Powering strategies for implanted multi-function neuroprostheses for spinal cord injury","volume":"7","author":"Kilgore","year":"2020","journal-title":"Healthc. Technol. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"281","DOI":"10.1109\/TBCAS.2021.3066838","article-title":"Design and Testing of Stimulation and Myoelectric Recording Modules in an Implanted Distributed Neuroprosthetic System","volume":"15","author":"Makowski","year":"2021","journal-title":"IEEE Trans. Biomed. Circuits Syst."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"347","DOI":"10.1088\/0967-3334\/32\/3\/006","article-title":"A method to deal with installation errors of wearable accelerometers for human activity recognition","volume":"32","author":"Jiang","year":"2011","journal-title":"Physiol. Meas."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Chen, Y., Hu, W., Yang, Y., Hou, J., and Wang, Z. (2014, January 28\u201330). A method to calibrate installation orientation errors of inertial sensors for gait analysis. Proceedings of the 2014 IEEE International Conference on Information and Automation (ICIA), Hailar, China.","DOI":"10.1109\/ICInfA.2014.6932724"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Bradach, M.M., Gaudette, L.W., Tenforde, A.S., Outerleys, J., De Souza J\u00fanior, J.R., and Johnson, C.D. (2023). The Effects of a Simple Sensor Reorientation Procedure on Peak Tibial Accelerations during Running and Correlations with Ground Reaction Forces. Sensors, 23.","DOI":"10.3390\/s23136048"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Friederich, A.R.W., Audu, M.L., and Triolo, R.J. (2022). Trunk Posture from Randomly Oriented Accelerometers. Sensors, 22.","DOI":"10.3390\/s22197690"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"743","DOI":"10.1007\/s00586-008-0586-0","article-title":"Trunk posture monitoring with inertial sensors","volume":"17","author":"Wong","year":"2008","journal-title":"Eur. Spine J."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"20620","DOI":"10.3390\/s141120620","article-title":"Chronically Implanted Pressure Sensors: Challenges and State of the Field","volume":"14","author":"Yu","year":"2014","journal-title":"Sensors"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1093","DOI":"10.1109\/TMTT.2018.2886844","article-title":"Radio Frequency Backscatter Communication for High Data Rate Deep Implants","volume":"67","author":"Khaleghi","year":"2019","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_26","first-page":"2012","article-title":"Tilt Sensing Using a Three-Axis Accelerometer","volume":"1","author":"Pedley","year":"2013","journal-title":"Free. Semicond. Appl. Note"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Liu, R., and Liu, M. (2010, January 18\u201320). Recognizing Human Activities Based on Multi-Sensors Fusion. Proceedings of the 2010 4th International Conference on Bioinformatics and Biomedical Engineering, Chengdu, China.","DOI":"10.1109\/ICBBE.2010.5514802"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/12\/3816\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:57:51Z","timestamp":1760108271000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/24\/12\/3816"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,6,13]]},"references-count":27,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2024,6]]}},"alternative-id":["s24123816"],"URL":"https:\/\/doi.org\/10.3390\/s24123816","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,6,13]]}}}