Biomechanical evaluation of the 3D printing brace for the lumbar spine

Biomechanical evaluation of the 3D printing brace for the lumbar spine | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Biomechanical evaluation of the 3D printing brace for the lumbar spine Hsiang-Chieh Hsu, Po-Yin Chen, Chen-Sheng Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8586922/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose To evaluate the biomechanical effects of a customized 3D printing brace (3DP), comparing with standardized braces (Medi-H, Medi-S) in healthy adults. Methods Sixteen participants (13 females, three males) performed four tasks—static standing, trunk flexion, trunk extension, and pick-up, while wearing each brace. Interface pressure distribution was measured across seven regions—upper/middle/lower spine and erector spinae, and quadratus lumborum. Thoracic and lumbar range of motion (ROM) were simultaneously assessed from C7 to T8, and from T8 to L3. A repeated-measures ANOVA was used to examine the effects of braces. Results Both 3DP and Medi-H generated significantly higher overall pressures than Medi-S, which averaged only 60% of their values. In flexion and pick-up tasks, 3DP enhanced support at the middle regions but showed markedly reduced pressure in the lower region compared with Medi-H. 3DP provided greater support at the erector spinae regions, while Medi-H produced higher spinal pressures, especially during extension. Across all tasks, thoracic and lumbar ROM ranged between 20° and 30°, with no significant differences between the three braces, indicating that restriction of sagittal motion was comparable. Conclusion Within a similar restriction of both ROM, the 3DP provided superior biomechanical support at upper and middle support compared with standardized braces, but it requires further refinement in the lower regions. spinal braces 3D printing pressure distribution range of motion biomechanics Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Spinal braces are widely used across prevention and rehabilitation settings to restrict excessive trunk motion, protect the spine, and enhance postural stability during daily activities. Modern lifestyle patterns such as prolonged sitting or repetitive trunk movements, frequently impose repetitive mechanical loading on our spine, which may lead to low back discomfort, detrimental postural control, and clinically diagnosed pathology [ 1 ]. Previous studies have demonstrated that providing an appropriate external spinal support can improve motor control and functional performance, making spinal braces a valuable conservative intervention, not only after spinal surgery but also for individuals with subacute spinal symptoms [ 2 , 3 ]. Two studies have indicated that the prevalence rates of wearing spinal braces after lumbar surgery of 49% and 38% [ 4 , 5 ]. Although the prevalence of wearing spinal braces in subacute patients is unclear, the study pointed out that wearing a lumbar brace can still reduce low-back pain [ 6 ]. Despite their clinical utility, most commercially available spinal braces are manufactured in standardized sizes, which often result in a suboptimal fit, reduced comfort, and heat retention due to limited airflow, ultimately leading to decreased user compliance [ 3 , 7 ]. The mechanical rationale of spinal braces generally falls into two primary design strategies. The primary objective is to increase intra-abdominal pressure by providing circumferential compression, thereby enhancing spinal stability through increased core muscle activation [ 8 ]. Braces that adopt this approach are typically fabric-based and lighter but may cause heat buildup during prolonged wear. The second strategy involves directly restricting trunk motion through their structural rigidity [ 9 ]. Although rigid braces provide more effective restriction of the spinal range of motion, their bulkier profile and limited flexibility frequently compromise comfort and movement compatibility. As a result, finding an optimal balance between support, mobility, breathability, and user comfort remains a challenge in spinal brace designs. To address the limitations of standardized braces, customized spinal braces have become increasingly popular in recent years for meeting the needs of every specific group. Enabled by advancements in 3D body scanning, computer-aided design, and manufacturing technologies, these braces can be tailored to every individual’s torso geometry and their requirements. Customized braces have been shown to increase adherence, maintain better spinal curves, and decrease manufacturing time and cost compared to traditional designs [ 10 , 11 ]. However, although customized spinal braces have emerged in recent years, existing research has predominantly focused on scoliosis populations, with the primary goal being curve correction [ 12 – 15 ]. In contrast, previous studies examining spinal braces for general users mainly compared standardized braces in terms of their materials and ROM restriction [ 7 , 8 , 16 , 17 ]. Consequently, little is known about customized spinal braces for general users, including the differences in structural design and material properties, as well as biomechanical performances such as regional pressure distribution and ROM restriction during daily movements. Given these gaps, this study aims to evaluate the biomechanical characteristics of a 3D-printed spinal brace compared with two standardized braces commonly used in clinical practice. By examining regional interface pressure and spinal angles across various functional tasks, this study aims to determine whether a customized 3D printing brace offers advantages in support distribution and motion control. The findings are expected to provide essential biomechanical evidence that may guide clinical decisions and inform the future development of a personalized spinal brace. Methods Participants Sixteen healthy adults (13 females, three males; mean age 23 year-old, BMI 21 kg/m²; mean waistline 70.9 cm) were recruited. Exclusion criteria included a history of spinal disease, recent low back pain, and anthropometric values outside World Health Organization (WHO) standards (BMI 18.5–24 kg/m²; waist circumference ≤ 90 cm for men and ≤ 80 cm for women). This study was approved by the Institutional Review Board of National Yang Ming Chiao Tung University (NYCU 113149AE). The participant provided informed consent prior to the experiment. Spinal braces Three types of spinal braces were chosen: a customized 3D-printed brace (3DP; Cheng-Chuan Prosthetics & Orthotics Co., Taipei, Taiwan), a relatively rigid spinal brace (Medi-H; Lumbamed® disc, Medi GmbH & Co. KG, Germany), and a relatively soft brace (Medi-S; Lumbamed® disc, Medi GmbH & Co. KG, Germany). (Fig. 1). In terms of the design purpose, three braces all focus on increasing contact pressure, while 3DP and Medi-H also have more directly rigidity limitation related to their material. 3DP is fabricated by thermoplastic polyurethane (TPU) with a breathable grid structure design, which is known by its outstanding elasticity and stretchability. The Medi-H is covered by fabric, with metal straps inserted, and an external plastic panel that leads to higher rigidity. In contrast, the Medi-S only relies on fabric coverage. Before constructing 3DP, the subject's trunk circumference is measured (Fig. 2 ). Necessary measurements include full and half chest circumference, waist circumference, and hip circumference. Contact pressure measurement A pressure sensor mat (Tactilus® Seat Pressure Mapping System, Sensor Products International Srl., Bologna, Italy) was placed between braces and the individual torso to recorded pressures across seven anatomical regions: upper, middle, and lower spine regions (SU, SM, SL); upper, middle, and lower erector spinae regions (EU, EM, EL); and both side of quadratus lumborum (QL) (Fig. 3 ). Note 1. SU: upper spine region; 2. SM: middle spine region; 3. SL: lower spine regions 4. EU: upper erector spinae region; 5. EM: middle erector spinae regions; 6. EL: lower erector spinae regions 7. QL: both sides of the quadratus lumborum Motion analysis Three inertial measurement units (IMUs, DOT, Xsens, Enschede, Netherlands) were placed at the spinous processes of C7, T8, and L3 (Fig. 4 ). After zeroing the sensors’ baseline Euler angle at static standing posture, the relative angles were measured at each task’s end-of-motion. Thoracic ROM (∆θ_thoracic) is defined as the change in sagittal plane angle between the C7 and T8 IMU, whereas lumbar ROM (∆θ_lumbar) is between T8 and L3. The formulas are as follows: ∆θ_thoracic = (θ_C7 - θ_T8) ∆θ_lumbar = (θ_T8 - θ_L3) Procedures All participants performed the following tasks while wearing each brace: 1. Static standing : The first 5 seconds of the upright position before starting all tasks. 2. Trunk flexion : Forward bending to the maximum comfortable range. 3. Trunk extension : Backward leaning to the maximum comfortable range. 4. Pick-up : Squatting and forward bending to pick up the object, which was placed one arm's length in front of the participants, by using their dominant hand. For each condition, pressure distribution and IMU data were recorded simultaneously. All movements were measured three times consecutively, with speed controlled by the subject (Fig. 5 ). Data analysis Repeated-measures ANOVA was used to assess the effects of braces on all pressure and ROM, using IBM SPSS Statistics version 29.0.1.1. All statistical data are presented as means with standard deviations. Statistical significance was set at p < 0.05. Result Overall average pressure To fully understand the effect of the spinal brace, the study calculated the mean pressure across all pressure regions for the three braces. 3DP and Medi-H produced significantly higher mean pressures than Medi-S in all tasks (p < 0.001), with Medi-S showing only about 60% of the values of 3DP and Medi-H. Differences between 3DP and Medi-H were not significant (Table 1 ). Table 1 Comparison of average pressure in all tasks Unit: N/cm 2 3DP Medi-H Medi-S Standing 0.089 0.094 0.061 Flexion 0.102 0.101 0.066 Extension 0.160 0.155 0.104 Pick-up 0.087 0.095 0.062 Regional average pressure Static Standing Significant differences across the spinal regions (SU, SM, and SL) were observed between the one brace and each other (Fig. 6 ). The highest pressure at SM was produced by 3DP (0.056 N/cm²), approximately 51% greater than Medi-H. While the highest pressures at SU and SL were generated by Medi-H (0.084 and 0.111 N/cm²), over 25% higher than 3DP. Unit: 10 − 3 N/cm 2 Note 1. Yellow parts: The maximum pressure value in each region between the three braces; 2. the value is magnified 1000 times. (For example, 121 is 0.121 N/cm²) Flexion All braces concentrated force at the middle regions (SM and EM). 3DP showed a significant highest EM pressure (0.207 N/cm²), greater than Medi-H (0.131 N/cm²) and Medi-S (0.089 N/cm²). Conversely, 3DP was the lowest at EL (0.036 N/cm²), whereas Medi-H exerted the highest (0.082 N/cm²) (Fig. 7 ). Unit: 10 − 3 N/cm 2 Note Yellow parts: The maximum pressure value in each region between the three braces Pick-up The distribution was similar to the flexion task, with pressures focused on SM and EM, but all slightly lower. 3DP maintained the greatest EM value of 0.156 N/cm², significantly higher than Medi-H (0.123 N/cm²) and Medi-S (0.073 N/cm²). The same pattern observed at EL was also evident at Medi-H, where the highest pressure was recorded (0.091 N/cm²), while 3DP had the lowest pressure (0.039 N/cm²). Extension Pressures were generally elevated at the upper and lower regions. At the same time, Medi-H produced the highest values in the spine region (SU and SL), with SL exceeding 0.25 N/cm² and significantly greater than those of the others. In contrast, 3DP showed the greatest pressures in the erector spinae region (EU and EL), with EU (0.256 N/cm²) significantly higher than Medi-H (0.194 N/cm²) and Medi-S (0.155 N/cm²) (Fig. 8). (A) (B) (C) Unit: 10 − 3 N/cm 2 Figure 8 Pressure distribution in extension task (A) 3DP (B) Medi-H (C) Medi-S Note Yellow parts: The maximum pressure value in each region between three braces ROM data Overall, there were no significant differences in thoracic (C7-T8) and lumbar (T8-L3) ROM between the three braces in all tasks (Table 2 ). While the flexion task was most restricted by 3DP (29.64°), the extension task was most restricted by Medi-H (-22.59°), followed by the pick-up task, which was restricted by Medi-S (23.47°) and 3DP (24.16°). Table 2 Thoracic and lumbar ROM in the sagittal plane Tasks 3DP ( \(\:^\circ\:\) ) Medi-H ( \(\:^\circ\:\) ) Medi-S ( \(\:^\circ\:\) ) Flexion C7-T8 24.86 (11.53) 27.85 (14.01) 29.12 (15.06) T8-L3 29.64 (2.73) 34.07 (2.28) 30.28 (3.44) Extension C7-T8 -23.60 (10.79) -22.42 (10.08) -23.36 (10.92) T8-L3 -32.66 (22.8) -22.59 (11.73) -39.22 (18.97) Pick up C7-T8 22.28 (13.37) 29.34 (21.51) 21.48 (9.99) T8-L3 24.16 (11.23) 27.55 (11.17) 23.47 (11.49) Note: Mean (SD), positive values mean the forward movement, negative values are backward Discussion Supportive force across braces In this study, we consider pressures have different implications for trunk support at upper, middle, and lower regions. Overall, pressure in the upper and middle regions is more matched to the “supportive force” on biomechanical definition. The upper region pressure can be considered the “upward support force” provided by braces, which is intended to support an individual’s trunk and reduce spinal intervertebral disc load. Pressure applied to the middle region is particularly important for maintaining lumbar lordosis, as this region corresponds to the apex of the normal lumbar curvature. This role is especially critical in static postures such as standing, where the middle region closely approximates the body’s center of gravity and therefore plays a key role in postural stability. As for the lower region, its primary function is to stabilize the sacrum and anchor the brace to the torso; therefore, it exerts a relatively limited direct influence on lumbar motion compared to the upper and middle regions. In addition, our study interprets a higher interface pressure value as indicating better supportive performance of the brace; the pressure recorded in this study reached a maximum value of only 0.25 N/cm². In contrast, excessive pressure is typically defined as a prolonged vertical loading that exceeds the capillary closing pressure 0.42 N/cm² [ 18 ]. In the results, wearing 3DP demonstrated a more even pressure distribution compared with the other two standardized braces in static standing, reflecting its superior conformity and supportive force to the torso. Notably, the highest peak pressures in the upper and middle regions (SU, SM, EU, EM) were also predominantly observed with 3DP, suggesting a more effective supportive function in these essential regions. This finding is particularly meaningful when performing a forward movement task, as the middle region aligns with the L3–L4 segment, which experiences the greatest shear force during trunk flexion [ 19 ]. Therefore, the increased pressure in the middle region (EM and SM) provided by 3DP further explains its superior protective performance during our flexion and pick-up tasks. Conversely, the pressure distribution at the lower region (EL and SL) showed an opposite pattern, with 3DP exhibiting the lowest pressures and Medi-H the highest. Particularly at EL region, pressures measured during the flexion and pick-up tasks were 127% and 133% higher for Medi-H than for 3DP, respectively. This difference may be explained by the design of 3DP, which focuses on conforming closely to the spinal curvature in static posture but tends to tilt outward at the inferior edge during forward movements. Such behavior may reduce effective anchoring at the lower region, leading to decreased contact pressure. Whereas forward movement tasks primarily challenge anterior shear control, trunk extension increases posterior contact demands and loading of the paraspinals. During the extension task, pressure was primarily concentrated at the superior and inferior ends of all braces. Notably, 3DP generated 54% higher average pressure across all regions compared with Medi-S, indicating enhanced support during backward movement. Similar findings have been reported by Terai et al. [ 20 ], demonstrating that pressure during trunk extension is also mainly distributed at the superior and inferior ends of the braces, with the custom-made stay brace exhibiting mean pressure values approximately 60% greater than those of the aluminum-stayed brace and nearly double those of the plastic-stayed brace. Together, these findings further support the role of customized spinal braces in providing effective stabilization during trunk extension. In addition, the observed pressure patterns further highlight the structural differences between the three braces. 3DP generated greater pressures in the erector spinae regions (EU and EL), whereas higher pressures in the spinal vertebral regions (SU and SL) were observed with Medi-H. The increased paraspinal pressures associated with 3DP are likely attributable to its thicker 3D printed structure along the erector spinae, which provides enhanced supportive force during trunk extension. In contrast, the elevated pressures observed with Medi-H over the spinal regions (SU and SL), along with a localized peak at the EM region, are likely the result of its rigid external plastic panel and strap configuration, which applies direct contact forces to these areas. Based on the present findings, 3DP brace demonstrated superior overall supportive performance compared with standardized braces. The advantages of the 3DP were attributed to the semi-rigid 3D printing material and semi-custom-made orthosis. However, lower pressure patterns were observed at the lower region during the flexion and pick-up tasks, where 3DP tended to tilt outward and exhibit reduced contact pressure. To address this limitation, future design modifications could consider optimizing the strap configuration at the lower region to enhance direct contact pressure. Such adjustments may improve lower-region stabilization, which similar to the localized pressure effect observed at EM region of Medi-H. ROM limitation The three spinal segments selected (C7, T8, and L3) represent the apex of normal lumbar curvature and have also been commonly used to evaluate spinal ROM in previous studies [ 7 , 8 ]. Overall, the thoracic and lumbar ROM results under different tasks were roughly similar and with no statistically significant difference across the three braces, indicating that they could effectively limit individuals to a comparable extent. The best limitation in the flexion task was 3DP (29.64°), the extension task was Medi-H (-22.59°), and the pick-up task was Medi-S (23.47°). When considered alongside previous studies, the present results indicate that customized spinal braces generally provide greater motion restriction than standardized designs, and that this effect is closely associated with the material stiffness of aluminum and plastic [ 20 ]. Lang et al. [ 21 ] reported that customized rigid and semi-rigid braces achieved superior ROM restriction compared with a standardized brace. Similar findings were reported by Terai et al. [ 20 ], who demonstrated that extension ROM restriction decreased from custom-made braces (− 27.5°) to 3DP (− 32.66°), aluminum-stayed braces (− 33.4°), and plastic-stayed braces (− 34.3°). These findings support a positive relationship between brace stiffness and ROM restriction during controlled flexion and extension tasks, provided that the brace is appropriately conforming and fitted to the individual’s trunk. The semi-rigid material of the 3DP was suitable for the application of the spinal brace, as it provided a supportive effect and limited the range of motion. Notably, the pick-up task demonstrated a different pattern, where Medi-S provided the greatest restriction (23.47°), followed by 3DP (24.16°), then Medi-H (27.55°). This observation aligns with Fercho et al.[ 8 ]. The Hohmann brace, characterized by a lower rigidity, has the lowest lumbar inclination angle (1.3°), indicating that it could maintain the posture in a relatively upright position. Those results confirm that for complex movements, the ROM restriction may not be entirely due to the stiffness of the brace, but rather mainly comes from the muscle response induced by the biofeedback mechanism and the intra-abdominal pressure. A softer brace may be more effective in this regard. The study was performed with some considerations. The study population was limited to healthy volunteers rather than clinical patients, which may affect the generalizability of the results to individuals with spinal pathologies. Additionally, a skewed gender ratio may have introduced biological or anatomical biases into the data. While 3DP was utilized, the orthoses were produced in three standardized sizes rather than being fully customized to each participant's unique anatomy. The use of IMU sensors provides an estimate of movement but may not perfectly reflect the internal kinematics of the spine due to soft tissue artifacts. The research was cross-sectional in nature; therefore, the long-term physiological effects and durability of the 3DP device remain unknown. Conclusion Overall, 3DP demonstrated superior supportive performance compared with the standardized braces. The elevated pressures observed in the upper region highlight its effective upward supportive force, while the increased pressure in the middle region indicates its potential for maintaining lumbar curvature, with 3DP was at least 58% and 27% higher than those of the standardized braces (Medi-H and Medi-S) during the flexion and pick-up tasks, respectively. In addition, thoracic and lumbar ROM did not differ significantly among the three braces across all tasks, with values consistently ranging between 20° and 30°. Declarations Competing Interests The authors declare that this study was conducted as an industry-academia cooperation project supported by the Ministry of Science and Technology Council, and Cheng-Chuan Prosthetics & Orthotics Co. The manufacturer provided the 3D-printed braces used in this study. However, the manufacturer had no role in the study design, data collection, analysis, data interpretation, or the decision to submit the manuscript for publication. Author Contribution Conceptualization, C.-S.C.; methodology, C.-S.C.; formal analysis, H.-C.H.; investigation, H.-C.H.; resources, C.-S.C.; data curation, H.-C.H..; writing—original draft preparation, H.-C.H.; writing—review and editing P.-Y.C., supervision, C.-S.C.; funding acquisition, C.-S.C. All authors have read and agreed to the published version of the manuscript. References GBD 2021 Low Back Pain Collaborators (2023) Global, regional, and national burden of low back pain, 1990–2020, its attributable risk factors, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021. Lancet Rheumatol 5(6):e316–e329. https://doi.org/10.1016/S2665-9913(23)00098-X Calmels P, Queneau P, Hamonet C, Le Pen C, Maurel F, Lerouvreur C, Thoumie P et al (2009) Effectiveness of a lumbar belt in subacute low back pain: an open, multicentric, and randomized clinical study. 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Eur J Orthop Surg Traumatol 24(Suppl 1):S239–S243. https://doi.org/10.1007/s00590-014-1446-8 Lang G, Hirschmüller A, Patermann S, Eichelberger P, Strohm P, Baur H, Südkamp NP, Herget GW (2018) Efficacy of Thoracolumbar Bracing in Spinal Immobilization: Precise Assessment of Gross, Intersegmental, and Segmental Spinal Motion Restriction by a 3D Kinematic System. World Neurosurg 116:e128–e146. https://doi.org/10.1016/j.wneu.2018.04.133 Additional Declarations Competing interest reported. The authors declare that this study was conducted as an industry-academia cooperation project supported by the Ministry of Science and Technology Council, and Cheng-Chuan Prosthetics & Orthotics Co. The manufacturer provided the 3D-printed braces used in this study. However, the manufacturer had no role in the study design, data collection, analysis, data interpretation, or the decision to submit the manuscript for publication. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8586922","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":585781567,"identity":"1dc8875f-5613-4a7f-a5c6-1faf5351e579","order_by":0,"name":"Hsiang-Chieh Hsu","email":"","orcid":"","institution":"National Yang Ming Chiao Tung University","correspondingAuthor":false,"prefix":"","firstName":"Hsiang-Chieh","middleName":"","lastName":"Hsu","suffix":""},{"id":585781568,"identity":"01ba3e0e-e4ec-404e-ac3f-fea8c5fb6434","order_by":1,"name":"Po-Yin Chen","email":"","orcid":"","institution":"National Yang Ming Chiao Tung University","correspondingAuthor":false,"prefix":"","firstName":"Po-Yin","middleName":"","lastName":"Chen","suffix":""},{"id":585781569,"identity":"ee2912ba-8cf7-4647-8164-c25cdca5d3ac","order_by":2,"name":"Chen-Sheng Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+klEQVRIiWNgGAWjYHACNiCWkOPnbz4AFUggSouNseSMYzClQPoATtVwLWmJBgdyDIjTwt9/+NmDjzsOJzAcOPPtMU/NYQZ+9hwD5o9tuLVI3EgzN5x55nAeY3PvdmOeY4cZJHveGDAcxKPFQIKHTZq37XAxM8PZbdK8DYcZDG4AXXhwGx4t/GfYpP+2HU5sY8h5BtZiT1ALQw6bNGNbWmIPiAG2RYKAFqBfzCR722yMJSSOmUnOOZbOI3HmWcGBs/9wawGFmMTPNgk5+/PNzyTe1FjL8bcnb3xQcQa3FhTAxMPAwANiHCBSAwMD4w+ilY6CUTAKRsFIAgB/e1MCkiANlgAAAABJRU5ErkJggg==","orcid":"","institution":"National Yang Ming Chiao Tung University","correspondingAuthor":true,"prefix":"","firstName":"Chen-Sheng","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2026-01-13 03:53:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8586922/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8586922/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102180750,"identity":"fe0caf06-7b8d-496f-8c29-3f8548f2c171","added_by":"auto","created_at":"2026-02-09 07:13:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":512122,"visible":true,"origin":"","legend":"\u003cp\u003eSpinal braces used in the study (A)3DP (B)Medi-H (C)Medi-S\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/41a83053bde76b4baf7c549b.png"},{"id":102180760,"identity":"c512a77c-df84-40b1-b3ce-515643ed32bb","added_by":"auto","created_at":"2026-02-09 07:13:47","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":456757,"visible":true,"origin":"","legend":"\u003cp\u003e3DP measurement. (i) chest circumference: measured at the lower chest line, (ii) waist circumference: measured at the narrowest part of the waist, (iii) hip circumference: measured at the midway between anterior superior iliac spine (ASIS) and greater trochanter\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/b92545fed26a740110377059.png"},{"id":102180755,"identity":"72fe2dc4-82b5-4f87-81d9-34abb6256329","added_by":"auto","created_at":"2026-02-09 07:13:46","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":795080,"visible":true,"origin":"","legend":"\u003cp\u003ePressure pad regions (A) mapping system diagram (B) actual wearing diagram\u003c/p\u003e\n\u003cp\u003eNote:\u003c/p\u003e\n\u003cp\u003e1. SU: upper spine region;\u003c/p\u003e\n\u003cp\u003e2. SM: middle spine region;\u003c/p\u003e\n\u003cp\u003e3. SL: lower spine regions\u003c/p\u003e\n\u003cp\u003e4. EU: upper erector spinae region;\u003c/p\u003e\n\u003cp\u003e5. EM: middle erector spinae regions;\u003c/p\u003e\n\u003cp\u003e6. EL: lower erector spinae regions\u003c/p\u003e\n\u003cp\u003e7. QL: both sides of the quadratus lumborum\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/4c49338e84508f9a0a442c78.png"},{"id":102180751,"identity":"c3daa4bd-d421-43f1-9da9-3547f527d902","added_by":"auto","created_at":"2026-02-09 07:13:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":111490,"visible":true,"origin":"","legend":"\u003cp\u003eThree IMUs placements\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/ebd712232e560340610764ac.png"},{"id":102180754,"identity":"a79efc76-202a-4166-8c14-9594fe773b7e","added_by":"auto","created_at":"2026-02-09 07:13:46","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":884292,"visible":true,"origin":"","legend":"\u003cp\u003eTasks instruction (A) flexion (B) extension (C) pick-up\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/d7b31015906d3f97deb463aa.png"},{"id":102180757,"identity":"0240881a-1355-41e7-ae20-498954d49402","added_by":"auto","created_at":"2026-02-09 07:13:47","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":450935,"visible":true,"origin":"","legend":"\u003cp\u003ePressure distribution in static standing (A) 3DP (B) Medi-H (C) Medi-S\u003c/p\u003e\n\u003cp\u003eUnit: 10\u003csup\u003e-3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eNote: 1. Yellow parts: The maximum pressure value in each region between the three braces; 2.\u0026nbsp;\u0026nbsp; the value is magnified 1000 times. (For example, 121 is 0.121 N/cm²)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/cebee47b2d07bdcc3942efb8.png"},{"id":102180758,"identity":"c695c7ab-8a28-4bc8-adcc-229efadcd6af","added_by":"auto","created_at":"2026-02-09 07:13:47","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":471447,"visible":true,"origin":"","legend":"\u003cp\u003ePressure distribution in flexion task (A) 3DP (B) Medi-H (C) Medi-S\u003c/p\u003e\n\u003cp\u003eUnit: 10\u003csup\u003e-3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eNote: Yellow parts: The maximum pressure value in each region between the three braces\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/f41e8195ae6d6c1e395b00e6.png"},{"id":102180759,"identity":"cba84fa1-46da-49e6-92d0-9ca97d1684fd","added_by":"auto","created_at":"2026-02-09 07:13:47","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":486447,"visible":true,"origin":"","legend":"\u003cp\u003ePressure distribution in extension task (A) 3DP (B) Medi-H (C) Medi-S\u003c/p\u003e\n\u003cp\u003eNote: Yellow parts: The maximum pressure value in each region between three braces Unit: 10\u003csup\u003e-3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/e7bfa5af674cdd8dc56b2e06.png"},{"id":104790909,"identity":"421be66a-891f-49be-8b1e-251f99f567e5","added_by":"auto","created_at":"2026-03-17 08:35:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6261081,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8586922/v1/23a52104-8c8c-4a2a-8445-4e26b6232b8b.pdf"}],"financialInterests":"Competing interest reported. The authors declare that this study was conducted as an industry-academia cooperation project supported by the Ministry of Science and Technology Council, and Cheng-Chuan Prosthetics \u0026 Orthotics Co. The manufacturer provided the 3D-printed braces used in this study. However, the manufacturer had no role in the study design, data collection, analysis, data interpretation, or the decision to submit the manuscript for publication.","formattedTitle":"Biomechanical evaluation of the 3D printing brace for the lumbar spine","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSpinal braces are widely used across prevention and rehabilitation settings to restrict excessive trunk motion, protect the spine, and enhance postural stability during daily activities. Modern lifestyle patterns such as prolonged sitting or repetitive trunk movements, frequently impose repetitive mechanical loading on our spine, which may lead to low back discomfort, detrimental postural control, and clinically diagnosed pathology [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePrevious studies have demonstrated that providing an appropriate external spinal support can improve motor control and functional performance, making spinal braces a valuable conservative intervention, not only after spinal surgery but also for individuals with subacute spinal symptoms [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Two studies have indicated that the prevalence rates of wearing spinal braces after lumbar surgery of 49% and 38% [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Although the prevalence of wearing spinal braces in subacute patients is unclear, the study pointed out that wearing a lumbar brace can still reduce low-back pain [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Despite their clinical utility, most commercially available spinal braces are manufactured in standardized sizes, which often result in a suboptimal fit, reduced comfort, and heat retention due to limited airflow, ultimately leading to decreased user compliance [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe mechanical rationale of spinal braces generally falls into two primary design strategies. The primary objective is to increase intra-abdominal pressure by providing circumferential compression, thereby enhancing spinal stability through increased core muscle activation [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Braces that adopt this approach are typically fabric-based and lighter but may cause heat buildup during prolonged wear. The second strategy involves directly restricting trunk motion through their structural rigidity [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Although rigid braces provide more effective restriction of the spinal range of motion, their bulkier profile and limited flexibility frequently compromise comfort and movement compatibility. As a result, finding an optimal balance between support, mobility, breathability, and user comfort remains a challenge in spinal brace designs.\u003c/p\u003e \u003cp\u003eTo address the limitations of standardized braces, customized spinal braces have become increasingly popular in recent years for meeting the needs of every specific group. Enabled by advancements in 3D body scanning, computer-aided design, and manufacturing technologies, these braces can be tailored to every individual\u0026rsquo;s torso geometry and their requirements. Customized braces have been shown to increase adherence, maintain better spinal curves, and decrease manufacturing time and cost compared to traditional designs [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, although customized spinal braces have emerged in recent years, existing research has predominantly focused on scoliosis populations, with the primary goal being curve correction [\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In contrast, previous studies examining spinal braces for general users mainly compared standardized braces in terms of their materials and ROM restriction [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Consequently, little is known about customized spinal braces for general users, including the differences in structural design and material properties, as well as biomechanical performances such as regional pressure distribution and ROM restriction during daily movements.\u003c/p\u003e \u003cp\u003eGiven these gaps, this study aims to evaluate the biomechanical characteristics of a 3D-printed spinal brace compared with two standardized braces commonly used in clinical practice. By examining regional interface pressure and spinal angles across various functional tasks, this study aims to determine whether a customized 3D printing brace offers advantages in support distribution and motion control. The findings are expected to provide essential biomechanical evidence that may guide clinical decisions and inform the future development of a personalized spinal brace.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003eSixteen healthy adults (13 females, three males; mean age 23 year-old, BMI 21 kg/m\u0026sup2;; mean waistline 70.9 cm) were recruited. Exclusion criteria included a history of spinal disease, recent low back pain, and anthropometric values outside World Health Organization (WHO) standards (BMI 18.5\u0026ndash;24 kg/m\u0026sup2;; waist circumference\u0026thinsp;\u0026le;\u0026thinsp;90 cm for men and \u0026le;\u0026thinsp;80 cm for women). This study was approved by the Institutional Review Board of National Yang Ming Chiao Tung University (NYCU 113149AE). The participant provided informed consent prior to the experiment.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSpinal braces\u003c/h3\u003e\n\u003cp\u003eThree types of spinal braces were chosen: a customized 3D-printed brace (3DP; Cheng-Chuan Prosthetics \u0026amp; Orthotics Co., Taipei, Taiwan), a relatively rigid spinal brace (Medi-H; Lumbamed\u0026reg; disc, Medi GmbH \u0026amp; Co. KG, Germany), and a relatively soft brace (Medi-S; Lumbamed\u0026reg; disc, Medi GmbH \u0026amp; Co. KG, Germany). (Fig.\u0026nbsp;1).\u003c/p\u003e \u003cp\u003eIn terms of the design purpose, three braces all focus on increasing contact pressure, while 3DP and Medi-H also have more directly rigidity limitation related to their material. 3DP is fabricated by thermoplastic polyurethane (TPU) with a breathable grid structure design, which is known by its outstanding elasticity and stretchability. The Medi-H is covered by fabric, with metal straps inserted, and an external plastic panel that leads to higher rigidity. In contrast, the Medi-S only relies on fabric coverage. Before constructing 3DP, the subject's trunk circumference is measured (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Necessary measurements include full and half chest circumference, waist circumference, and hip circumference.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eContact pressure measurement\u003c/h3\u003e\n\u003cp\u003eA pressure sensor mat (Tactilus\u0026reg; Seat Pressure Mapping System, Sensor Products International Srl., Bologna, Italy) was placed between braces and the individual torso to recorded pressures across seven anatomical regions: upper, middle, and lower spine regions (SU, SM, SL); upper, middle, and lower erector spinae regions (EU, EM, EL); and both side of quadratus lumborum (QL) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNote\u003c/strong\u003e \u003cp\u003e1. SU: upper spine region;\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e2. SM: middle spine region;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e3. SL: lower spine regions\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e4. EU: upper erector spinae region;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e5. EM: middle erector spinae regions;\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e6. EL: lower erector spinae regions\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e7. QL: both sides of the quadratus lumborum\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e\n\u003ch3\u003eMotion analysis\u003c/h3\u003e\n\u003cp\u003eThree inertial measurement units (IMUs, DOT, Xsens, Enschede, Netherlands) were placed at the spinous processes of C7, T8, and L3 (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e). After zeroing the sensors\u0026rsquo; baseline Euler angle at static standing posture, the relative angles were measured at each task\u0026rsquo;s end-of-motion. Thoracic ROM (∆θ_thoracic) is defined as the change in sagittal plane angle between the C7 and T8 IMU, whereas lumbar ROM (∆θ_lumbar) is between T8 and L3. The formulas are as follows:\u003c/p\u003e \u003cp\u003e∆θ_thoracic = (θ_C7 - θ_T8)\u003c/p\u003e \u003cp\u003e∆θ_lumbar = (θ_T8 - θ_L3)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eProcedures\u003c/h3\u003e\n\u003cp\u003eAll participants performed the following tasks while wearing each brace:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e1. \u003cb\u003eStatic standing\u003c/b\u003e: The first 5 seconds of the upright position before starting all tasks.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e2. \u003cb\u003eTrunk flexion\u003c/b\u003e: Forward bending to the maximum comfortable range.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e3. \u003cb\u003eTrunk extension\u003c/b\u003e: Backward leaning to the maximum comfortable range.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003e4. \u003cb\u003ePick-up\u003c/b\u003e: Squatting and forward bending to pick up the object, which was placed one arm's length in front of the participants, by using their dominant hand.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eFor each condition, pressure distribution and IMU data were recorded simultaneously. All movements were measured three times consecutively, with speed controlled by the subject (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eRepeated-measures ANOVA was used to assess the effects of braces on all pressure and ROM, using IBM SPSS Statistics version 29.0.1.1. All statistical data are presented as means with standard deviations. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Result","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eOverall average pressure\u003c/h2\u003e \u003cp\u003eTo fully understand the effect of the spinal brace, the study calculated the mean pressure across all pressure regions for the three braces. 3DP and Medi-H produced significantly higher mean pressures than Medi-S in all tasks (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), with Medi-S showing only about 60% of the values of 3DP and Medi-H. Differences between 3DP and Medi-H were not significant (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of average pressure in all tasks Unit: N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3DP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMedi-H\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedi-S\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStanding\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.089\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.094\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.061\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlexion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.066\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExtension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.155\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.104\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePick-up\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.087\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.095\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.062\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eRegional average pressure\u003c/h2\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003eStatic Standing\u003c/h2\u003e \u003cp\u003eSignificant differences across the spinal regions (SU, SM, and SL) were observed between the one brace and each other (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The highest pressure at SM was produced by 3DP (0.056 N/cm\u0026sup2;), approximately 51% greater than Medi-H. While the highest pressures at SU and SL were generated by Medi-H (0.084 and 0.111 N/cm\u0026sup2;), over 25% higher than 3DP.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUnit: 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNote\u003c/strong\u003e \u003cp\u003e1. Yellow parts: The maximum pressure value in each region between the three braces; 2. the value is magnified 1000 times. (For example, 121 is 0.121 N/cm\u0026sup2;)\u003c/p\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eFlexion\u003c/h2\u003e \u003cp\u003eAll braces concentrated force at the middle regions (SM and EM). 3DP showed a significant highest EM pressure (0.207 N/cm\u0026sup2;), greater than Medi-H (0.131 N/cm\u0026sup2;) and Medi-S (0.089 N/cm\u0026sup2;). Conversely, 3DP was the lowest at EL (0.036 N/cm\u0026sup2;), whereas Medi-H exerted the highest (0.082 N/cm\u0026sup2;) (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUnit: 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNote\u003c/strong\u003e \u003cp\u003eYellow parts: The maximum pressure value in each region between the three braces\u003c/p\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePick-up\u003c/h2\u003e \u003cp\u003eThe distribution was similar to the flexion task, with pressures focused on SM and EM, but all slightly lower. 3DP maintained the greatest EM value of 0.156 N/cm\u0026sup2;, significantly higher than Medi-H (0.123 N/cm\u0026sup2;) and Medi-S (0.073 N/cm\u0026sup2;). The same pattern observed at EL was also evident at Medi-H, where the highest pressure was recorded (0.091 N/cm\u0026sup2;), while 3DP had the lowest pressure (0.039 N/cm\u0026sup2;).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eExtension\u003c/h2\u003e \u003cp\u003ePressures were generally elevated at the upper and lower regions. At the same time, Medi-H produced the highest values in the spine region (SU and SL), with SL exceeding 0.25 N/cm\u0026sup2; and significantly greater than those of the others. In contrast, 3DP showed the greatest pressures in the erector spinae region (EU and EL), with EU (0.256 N/cm\u0026sup2;) significantly higher than Medi-H (0.194 N/cm\u0026sup2;) and Medi-S (0.155 N/cm\u0026sup2;) (Fig.\u0026nbsp;8).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e(A) (B) (C)\u003c/h2\u003e \u003cp\u003eUnit: 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e N/cm\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;8 Pressure distribution in extension task (A) 3DP (B) Medi-H (C) Medi-S\u003c/p\u003e \u003cp\u003e \u003cstrong\u003eNote\u003c/strong\u003e \u003cp\u003eYellow parts: The maximum pressure value in each region between three braces\u003c/p\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eROM data\u003c/h2\u003e \u003cp\u003eOverall, there were no significant differences in thoracic (C7-T8) and lumbar (T8-L3) ROM between the three braces in all tasks (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). While the flexion task was most restricted by 3DP (29.64\u0026deg;), the extension task was most restricted by Medi-H (-22.59\u0026deg;), followed by the pick-up task, which was restricted by Medi-S (23.47\u0026deg;) and 3DP (24.16\u0026deg;).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThoracic and lumbar ROM in the sagittal plane\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTasks\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3DP (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedi-H (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMedi-S (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eFlexion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC7-T8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24.86 (11.53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.85 (14.01)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e29.12 (15.06)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT8-L3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e29.64 (2.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e34.07 (2.28)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e30.28 (3.44)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eExtension\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC7-T8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-23.60 (10.79)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-22.42 (10.08)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-23.36 (10.92)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT8-L3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-32.66 (22.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e-22.59 (11.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-39.22 (18.97)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePick up\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC7-T8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.28 (13.37)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e29.34 (21.51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e21.48 (9.99)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eT8-L3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e24.16 (11.23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e27.55 (11.17)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e23.47 (11.49)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eNote: Mean (SD), positive values mean the forward movement, negative values are backward\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eSupportive force across braces\u003c/h2\u003e \u003cp\u003eIn this study, we consider pressures have different implications for trunk support at upper, middle, and lower regions. Overall, pressure in the upper and middle regions is more matched to the \u0026ldquo;supportive force\u0026rdquo; on biomechanical definition. The upper region pressure can be considered the \u0026ldquo;upward support force\u0026rdquo; provided by braces, which is intended to support an individual\u0026rsquo;s trunk and reduce spinal intervertebral disc load. Pressure applied to the middle region is particularly important for maintaining lumbar lordosis, as this region corresponds to the apex of the normal lumbar curvature. This role is especially critical in static postures such as standing, where the middle region closely approximates the body\u0026rsquo;s center of gravity and therefore plays a key role in postural stability. As for the lower region, its primary function is to stabilize the sacrum and anchor the brace to the torso; therefore, it exerts a relatively limited direct influence on lumbar motion compared to the upper and middle regions. In addition, our study interprets a higher interface pressure value as indicating better supportive performance of the brace; the pressure recorded in this study reached a maximum value of only 0.25 N/cm\u0026sup2;. In contrast, excessive pressure is typically defined as a prolonged vertical loading that exceeds the capillary closing pressure 0.42 N/cm\u0026sup2; [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the results, wearing 3DP demonstrated a more even pressure distribution compared with the other two standardized braces in static standing, reflecting its superior conformity and supportive force to the torso. Notably, the highest peak pressures in the upper and middle regions (SU, SM, EU, EM) were also predominantly observed with 3DP, suggesting a more effective supportive function in these essential regions. This finding is particularly meaningful when performing a forward movement task, as the middle region aligns with the L3\u0026ndash;L4 segment, which experiences the greatest shear force during trunk flexion [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Therefore, the increased pressure in the middle region (EM and SM) provided by 3DP further explains its superior protective performance during our flexion and pick-up tasks. Conversely, the pressure distribution at the lower region (EL and SL) showed an opposite pattern, with 3DP exhibiting the lowest pressures and Medi-H the highest. Particularly at EL region, pressures measured during the flexion and pick-up tasks were 127% and 133% higher for Medi-H than for 3DP, respectively. This difference may be explained by the design of 3DP, which focuses on conforming closely to the spinal curvature in static posture but tends to tilt outward at the inferior edge during forward movements. Such behavior may reduce effective anchoring at the lower region, leading to decreased contact pressure.\u003c/p\u003e \u003cp\u003eWhereas forward movement tasks primarily challenge anterior shear control, trunk extension increases posterior contact demands and loading of the paraspinals. During the extension task, pressure was primarily concentrated at the superior and inferior ends of all braces. Notably, 3DP generated 54% higher average pressure across all regions compared with Medi-S, indicating enhanced support during backward movement. Similar findings have been reported by Terai et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], demonstrating that pressure during trunk extension is also mainly distributed at the superior and inferior ends of the braces, with the custom-made stay brace exhibiting mean pressure values approximately 60% greater than those of the aluminum-stayed brace and nearly double those of the plastic-stayed brace. Together, these findings further support the role of customized spinal braces in providing effective stabilization during trunk extension. In addition, the observed pressure patterns further highlight the structural differences between the three braces. 3DP generated greater pressures in the erector spinae regions (EU and EL), whereas higher pressures in the spinal vertebral regions (SU and SL) were observed with Medi-H. The increased paraspinal pressures associated with 3DP are likely attributable to its thicker 3D printed structure along the erector spinae, which provides enhanced supportive force during trunk extension. In contrast, the elevated pressures observed with Medi-H over the spinal regions (SU and SL), along with a localized peak at the EM region, are likely the result of its rigid external plastic panel and strap configuration, which applies direct contact forces to these areas.\u003c/p\u003e \u003cp\u003eBased on the present findings, 3DP brace demonstrated superior overall supportive performance compared with standardized braces. The advantages of the 3DP were attributed to the semi-rigid 3D printing material and semi-custom-made orthosis. However, lower pressure patterns were observed at the lower region during the flexion and pick-up tasks, where 3DP tended to tilt outward and exhibit reduced contact pressure. To address this limitation, future design modifications could consider optimizing the strap configuration at the lower region to enhance direct contact pressure. Such adjustments may improve lower-region stabilization, which similar to the localized pressure effect observed at EM region of Medi-H.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eROM limitation\u003c/h2\u003e \u003cp\u003eThe three spinal segments selected (C7, T8, and L3) represent the apex of normal lumbar curvature and have also been commonly used to evaluate spinal ROM in previous studies [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Overall, the thoracic and lumbar ROM results under different tasks were roughly similar and with no statistically significant difference across the three braces, indicating that they could effectively limit individuals to a comparable extent. The best limitation in the flexion task was 3DP (29.64\u0026deg;), the extension task was Medi-H (-22.59\u0026deg;), and the pick-up task was Medi-S (23.47\u0026deg;).\u003c/p\u003e \u003cp\u003eWhen considered alongside previous studies, the present results indicate that customized spinal braces generally provide greater motion restriction than standardized designs, and that this effect is closely associated with the material stiffness of aluminum and plastic [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Lang et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] reported that customized rigid and semi-rigid braces achieved superior ROM restriction compared with a standardized brace. Similar findings were reported by Terai et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], who demonstrated that extension ROM restriction decreased from custom-made braces (\u0026minus;\u0026thinsp;27.5\u0026deg;) to 3DP (\u0026minus;\u0026thinsp;32.66\u0026deg;), aluminum-stayed braces (\u0026minus;\u0026thinsp;33.4\u0026deg;), and plastic-stayed braces (\u0026minus;\u0026thinsp;34.3\u0026deg;). These findings support a positive relationship between brace stiffness and ROM restriction during controlled flexion and extension tasks, provided that the brace is appropriately conforming and fitted to the individual\u0026rsquo;s trunk. The semi-rigid material of the 3DP was suitable for the application of the spinal brace, as it provided a supportive effect and limited the range of motion.\u003c/p\u003e \u003cp\u003eNotably, the pick-up task demonstrated a different pattern, where Medi-S provided the greatest restriction (23.47\u0026deg;), followed by 3DP (24.16\u0026deg;), then Medi-H (27.55\u0026deg;). This observation aligns with Fercho et al.[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The Hohmann brace, characterized by a lower rigidity, has the lowest lumbar inclination angle (1.3\u0026deg;), indicating that it could maintain the posture in a relatively upright position. Those results confirm that for complex movements, the ROM restriction may not be entirely due to the stiffness of the brace, but rather mainly comes from the muscle response induced by the biofeedback mechanism and the intra-abdominal pressure. A softer brace may be more effective in this regard.\u003c/p\u003e \u003cp\u003eThe study was performed with some considerations. The study population was limited to healthy volunteers rather than clinical patients, which may affect the generalizability of the results to individuals with spinal pathologies. Additionally, a skewed gender ratio may have introduced biological or anatomical biases into the data. While 3DP was utilized, the orthoses were produced in three standardized sizes rather than being fully customized to each participant's unique anatomy. The use of IMU sensors provides an estimate of movement but may not perfectly reflect the internal kinematics of the spine due to soft tissue artifacts. The research was cross-sectional in nature; therefore, the long-term physiological effects and durability of the 3DP device remain unknown.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOverall, 3DP demonstrated superior supportive performance compared with the standardized braces. The elevated pressures observed in the upper region highlight its effective upward supportive force, while the increased pressure in the middle region indicates its potential for maintaining lumbar curvature, with 3DP was at least 58% and 27% higher than those of the standardized braces (Medi-H and Medi-S) during the flexion and pick-up tasks, respectively. In addition, thoracic and lumbar ROM did not differ significantly among the three braces across all tasks, with values consistently ranging between 20\u0026deg; and 30\u0026deg;.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003cp\u003eThe authors declare that this study was conducted as an industry-academia cooperation project supported by the Ministry of Science and Technology Council, and Cheng-Chuan Prosthetics \u0026amp; Orthotics Co. The manufacturer provided the 3D-printed braces used in this study. However, the manufacturer had no role in the study design, data collection, analysis, data interpretation, or the decision to submit the manuscript for publication.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, C.-S.C.; methodology, C.-S.C.; formal analysis, H.-C.H.; investigation, H.-C.H.; resources, C.-S.C.; data curation, H.-C.H..; writing\u0026mdash;original draft preparation, H.-C.H.; writing\u0026mdash;review and editing P.-Y.C., supervision, C.-S.C.; funding acquisition, C.-S.C. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGBD 2021 Low Back Pain Collaborators (2023) Global, regional, and national burden of low back pain, 1990\u0026ndash;2020, its attributable risk factors, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021. 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World Neurosurg 116:e128\u0026ndash;e146. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.wneu.2018.04.133\u003c/span\u003e\u003cspan address=\"10.1016/j.wneu.2018.04.133\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"spinal braces, 3D printing, pressure distribution, range of motion, biomechanics","lastPublishedDoi":"10.21203/rs.3.rs-8586922/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8586922/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose\u003c/h2\u003e \u003cp\u003eTo evaluate the biomechanical effects of a customized 3D printing brace (3DP), comparing with standardized braces (Medi-H, Medi-S) in healthy adults.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eSixteen participants (13 females, three males) performed four tasks\u0026mdash;static standing, trunk flexion, trunk extension, and pick-up, while wearing each brace. Interface pressure distribution was measured across seven regions\u0026mdash;upper/middle/lower spine and erector spinae, and quadratus lumborum. Thoracic and lumbar range of motion (ROM) were simultaneously assessed from C7 to T8, and from T8 to L3. A repeated-measures ANOVA was used to examine the effects of braces.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eBoth 3DP and Medi-H generated significantly higher overall pressures than Medi-S, which averaged only 60% of their values. In flexion and pick-up tasks, 3DP enhanced support at the middle regions but showed markedly reduced pressure in the lower region compared with Medi-H. 3DP provided greater support at the erector spinae regions, while Medi-H produced higher spinal pressures, especially during extension. Across all tasks, thoracic and lumbar ROM ranged between 20\u0026deg; and 30\u0026deg;, with no significant differences between the three braces, indicating that restriction of sagittal motion was comparable.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eWithin a similar restriction of both ROM, the 3DP provided superior biomechanical support at upper and middle support compared with standardized braces, but it requires further refinement in the lower regions.\u003c/p\u003e","manuscriptTitle":"Biomechanical evaluation of the 3D printing brace for the lumbar spine","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-09 07:13:22","doi":"10.21203/rs.3.rs-8586922/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b657339c-631a-45a9-8180-3bca33d46bf5","owner":[],"postedDate":"February 9th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-01T12:24:17+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-09 07:13:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8586922","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8586922","identity":"rs-8586922","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}