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Orbach MR, Mahoney J, Bucklen BS, Balasubramanian S. In vitro coupled motions of the whole human thoracic and lumbar spine with rib cage. JOR Spine 2023; 6:e1257. [PMID: 37780824 PMCID: PMC10540827 DOI: 10.1002/jsp2.1257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 04/07/2023] [Accepted: 04/13/2023] [Indexed: 10/03/2023] Open
Abstract
Study design In vitro biomechanical study investigating the coupled motions of the whole normative human thoracic spine (TS) and lumbar spine (LS) with rib cage. Objective To quantify the region-specific coupled motion patterns and magnitudes of the TS, thoracolumbar junction (TLJ), and LS simultaneously. Background Studying spinal coupled motions is important in understanding the development of complex spinal deformities and providing data for validating computational models. However, coupled motion patterns reported in vitro are controversial, and no quantitative data on region-specific coupled motions of the whole human TS and LS are available. Methods Pure, unconstrained bending moments of 8 Nm were applied to seven fresh-frozen human cadaveric TS and LS specimens (mean age: 70.3 ± 11.3 years) with rib cages to elicit flexion-extension (FE), lateral bending (LB), and axial rotation (AR). During each primary motion, region-specific rotational range of motion (ROM) data were captured. Results No statistically significant, consistent coupled motion patterns were observed during primary FE. During primary LB, there was significant (p < 0.05) ipsilateral AR in the TS and a general pattern of contralateral coupled AR in the TLJ and LS. There was also a tendency for the TS to extend and the LS to flex. During primary AR, significant coupled LB was ipsilateral in the TS and contralateral in both the TLJ and LS. Significant coupled flexion in the LS was also observed. Coupled LB and AR ROMs were not significantly different between the TS and LS or from one another. Conclusions The findings support evidence of consistent coupled motion patterns of the TS and LS during LB and AR. These novel data may serve as reference for computational model validations and future in vitro studies investigating spinal deformities and implants.
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Affiliation(s)
- Mattan R. Orbach
- School of Biomedical Engineering, Science and Health SystemsDrexel UniversityPhiladelphiaPennsylvaniaUSA
| | - Jonathan Mahoney
- Musculoskeletal Education and Research CenterA Division of Globus Medical, IncAudubonPennsylvaniaUSA
| | - Brandon S. Bucklen
- Musculoskeletal Education and Research CenterA Division of Globus Medical, IncAudubonPennsylvaniaUSA
| | - Sriram Balasubramanian
- School of Biomedical Engineering, Science and Health SystemsDrexel UniversityPhiladelphiaPennsylvaniaUSA
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Wang Y, Huang K. Research progress of diagnosing methodology for lumbar segmental instability: A narrative review. Medicine (Baltimore) 2022; 101:e28534. [PMID: 35029921 PMCID: PMC8735792 DOI: 10.1097/md.0000000000028534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 12/19/2021] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE Lumbar segmental instability (LSI) is due to a pathologic movement of the vertebral body on the vertebra below and often causes clinical symptoms. The study was to achieve the research progress of diagnosing methodology for lumbar segmental instability and help clinicians make treatment choices. METHODS The data for this study were collected from the MEDLINE, Springer, Web of Science, PubMed, EMBASE, the Cochrane Central Register of Controlled Trials, Evidence Based Medicine Reviews, VIP, and CNKI. The search terms were integrated as follows: "(∗lumbar instability∗ OR ∗lumbar spondylolisthesis∗) and (∗image∗ or ∗diagnosis∗)". Studies without clear radiographic instable criteria, case reports, letter, and basic research were excluded. RESULT In total, 39 articles published met our inclusion criteria. The various modalities were used to diagnosis LSI in these studies included radiographs, facet joint degeneration and physical examination tests. CONCLUSION Overall, there have been a variety of researches to develop the diagnosing methodology for LSI, and many have been successful, although no consensus has been reached yet. However, it is believed that the diagnosis of LSI will become easier and more accurate in the near future.
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Affiliation(s)
- Yingfeng Wang
- Department of Spinal Surgery, Huangshan Peiple's Hospital, Anhui, China
| | - Kai Huang
- Department of Spinal Surgery, The Second People's Hospital of Changshu, The Affiliated Changshu Hospital of Xuzhou Medical Hospital, Jiangsu, China
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The rib cage stiffens the thoracic spine in a cadaveric model with body weight load under dynamic moments. J Mech Behav Biomed Mater 2018; 84:258-264. [PMID: 29852313 DOI: 10.1016/j.jmbbm.2018.05.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/12/2018] [Accepted: 05/09/2018] [Indexed: 01/23/2023]
Abstract
The thoracic spine presents a challenge for biomechanical testing. With more segments than the lumbar and cervical regions and the integration with the rib cage, experimental approaches to evaluate the mechanical behavior of cadaveric thoracic spines have varied widely. Some researchers are now including the rib cage intact during testing, and some are incorporating follower load techniques in the thoracic spine. Both of these approaches aim to more closely model physiological conditions. To date, no studies have examined the impact of the rib cage on thoracic spine motion and stiffness in conjunction with follower loads. The purpose of this research was to quantify the mechanical effect of the rib cage on cadaveric thoracic spine motion and stiffness with a follower load under dynamic moments. It was hypothesized that the rib cage would increase stiffness and decrease motion of the thoracic spine with a follower load. Eight fresh-frozen human cadaveric thoracic spines with rib cages (T1-T12) were loaded with a 400 N compressive follower load. Dynamic moments of ± 5 N m were applied in lateral bending, flexion/extension, and axial rotation, and the motion and stiffness of the specimens with the rib cage intact have been previously reported. This study evaluated the motion and stiffness of the specimens after rib cage removal, and compared the data to the rib cage intact condition. Range-of-motion and stiffness were calculated for the upper, middle, and lower segments of the thoracic spine. Range-of-motion significantly increased with the removal of the rib cage in lateral bending, flexion/extension, and axial rotation by 63.5%, 63.0%, and 58.8%, respectively (p < 0.05). Neutral and elastic zones increased in flexion/extension and axial rotation, and neutral zone stiffness decreased in axial rotation with rib cage removal. Overall, the removal of the rib cage increases the range-of-motion and decreases the stiffness of cadaveric thoracic spines under compressive follower loads in vitro. This study suggests that the rib cage should be included when testing a cadaveric thoracic spine with a follower load to optimize clinical relevance.
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Spinal fusion without instrumentation - Experimental animal study. Clin Biomech (Bristol, Avon) 2017; 46:6-14. [PMID: 28463696 DOI: 10.1016/j.clinbiomech.2017.04.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 02/17/2017] [Accepted: 04/24/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND The number and cost of instrumented spinal fusion surgeries have increased rapidly, primarily for the treatment of lumbar segmental instabilities. However, what if the organism itself is able to restore segmental stability over time? This large-animal study using sheep aimed to investigate whether the reparative response after destabilization via facetectomy and nucleotomy without instrumentation can effectively fuse the spinal segment comparable to instrumented standard fusion surgery. METHODS The following four surgical interventions were investigated: dorsal fixation via internal fixator, ventral fixation via cage as well as facetectomy and nucleotomy without additional instrumentation. Six months postoperatively, the animals were sacrificed, and the lumbar spines were used for biomechanical tests. FINDINGS Spinal stability was restored to the destabilized spinal segments at six months postoperatively and was comparable to the results of conventional surgery via screws and cages. Iatrogenic hypomobilization caused significant reductions in facet joint space and intervertebral disc height of segments at index and adjacent level. Restabilized segments after iatrogenic hypermobilzation also significantly decreased facet joint space and disc height at index level, but revealed no influence on adjacent segments. INTERPRETATION These findings in the sheep model question the necessity of costly instrumentation and suggest the alternative possibility of stimulating the reparative capacity of the body in human lumbar spine fusion surgery.
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Holsgrove TP, Miles AW, Gheduzzi S. The application of physiological loading using a dynamic, multi-axis spine simulator. Med Eng Phys 2017; 41:74-80. [DOI: 10.1016/j.medengphy.2016.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 11/03/2016] [Accepted: 12/18/2016] [Indexed: 11/26/2022]
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Zhou R, Huang Z, Liu X, Tong J, Ji W, Liu S, Zhu Q. Kinematics and load-sharing of an anterior thoracolumbar spinal reconstruction construct with PEEK rods: An in vitro biomechanical study. Clin Biomech (Bristol, Avon) 2016; 40:1-7. [PMID: 27756005 DOI: 10.1016/j.clinbiomech.2016.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 07/04/2016] [Accepted: 10/04/2016] [Indexed: 02/07/2023]
Abstract
BACKGROUND Polyetheretherketone rod constructs provide adequate spinal stability. Kinematics and load sharing of anterior thoracolumbar reconstruction with polyetheretherketone rods under preload remains unknown. METHODS Eight human cadaveric specimens (T11-L3) were subjected to a pure moment of 5.0Nm in flexion-extension, lateral bending and axial rotation, and flexion-extension with a compressive preload of 300N. An anterior reconstruction of L1 corpectomy was conducted with a surrogate bone graft and anterior rod constructs (polyetheretherketone or titanium rods). An axial load-cell was built in the surrogate bone graft to measure the compressive force in the graft. Range of motion, neutral zone and compressive force in the graft were compared between constructs. FINDINGS The polyetheretherketone rod construct resulted in more motion than the titanium rod construct, particularly in extension (P=0.011) and axial rotation (P=0.001), but less motion than the intact in all directions except in axial rotation. There was no difference in range of motion or neutral zone between constructs in flexion-extension under preload. The polyetheretherketone rod construct kept the graft compressed 52N which was similar to the titanium rod construct (63N), but allowed the graft compressed more under the preload (203N vs. 123N, P=0.003). The compressive forces fluctuated in flexion-extension without preload, but increased in flexion and decreased in extension under preload. INTERPRETATION The polyetheretherketone rod construct allowed more motion compared to the titanium rod construct, but provided stability in flexion and lateral bending without preload, and flexion and extension under preload. The anterior graft shared higher load under preload, particularly for the polyetheretherketone rod construct. The results of this study suggest that rigidity of rods in the anterior reconstruction affects kinematic behavior and load sharing.
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Affiliation(s)
- Ruozhou Zhou
- Department of Spine Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China; Department of Spine Surgery, the First People's Hospital of Chenzhou, Chenzhou, Hunan, People's Republic of China
| | - Zhiping Huang
- Department of Spine Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Xiang Liu
- Department of Spine Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Jie Tong
- Department of Spine Surgery, the First People's Hospital of Chenzhou, Chenzhou, Hunan, People's Republic of China
| | - Wei Ji
- Department of Spine Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China
| | - Sheting Liu
- Department of Spine Surgery, the First People's Hospital of Chenzhou, Chenzhou, Hunan, People's Republic of China
| | - Qingan Zhu
- Department of Spine Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, People's Republic of China.
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Naserkhaki S, El-Rich M. Sensitivity of lumbar spine response to follower load and flexion moment: finite element study. Comput Methods Biomech Biomed Engin 2016; 20:550-557. [PMID: 27848266 DOI: 10.1080/10255842.2016.1257707] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The follower load (FL) combined with moments is commonly used to approximate flexed/extended posture of the lumbar spine in absence of muscles in biomechanical studies. There is a lack of consensus as to what magnitudes simulate better the physiological conditions. Considering the in-vivo measured values of the intradiscal pressure (IDP), intervertebral rotations (IVRs) and the disc loads, sensitivity of these spinal responses to different FL and flexion moment magnitudes was investigated using a 3D nonlinear finite element (FE) model of ligamentous lumbosacral spine. Optimal magnitudes of FL and moment that minimize deviation of the model predictions from in-vivo data were determined. Results revealed that the spinal parameters i.e. the IVRs, disc moment, and the increase in disc force and moment from neutral to flexed posture were more sensitive to moment magnitude than FL magnitude in case of flexion. The disc force and IDP were more sensitive to the FL magnitude than moment magnitude. The optimal ranges of FL and flexion moment magnitudes were 900-1100 N and 9.9-11.2 Nm, respectively. The FL magnitude had reverse effect on the IDP and disc force. Thus, magnitude for FL or flexion that minimizes the deviation of all the spinal parameters together from the in-vivo data can vary. To obtain reasonable compromise between the IDP and disc force, our findings recommend that FL of low magnitude must be combined with flexion moment of high intensity and vice versa.
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Affiliation(s)
- Sadegh Naserkhaki
- a Department of Civil and Environmental Engineering , University of Alberta , Edmonton , Canada
| | - Marwan El-Rich
- a Department of Civil and Environmental Engineering , University of Alberta , Edmonton , Canada
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Naserkhaki S, Jaremko JL, Adeeb S, El-Rich M. On the load-sharing along the ligamentous lumbosacral spine in flexed and extended postures: Finite element study. J Biomech 2015; 49:974-982. [PMID: 26493346 DOI: 10.1016/j.jbiomech.2015.09.050] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/11/2015] [Accepted: 09/27/2015] [Indexed: 10/22/2022]
Abstract
A harmonic synergy between the load-bearing and stabilizing components of the spine is necessary to maintain its normal function. This study aimed to investigate the load-sharing along the ligamentous lumbosacral spine under sagittal loading. A 3D nonlinear detailed Finite Element (FE) model of lumbosacral spine with realistic geometry was developed and validated using wide range of numerical and experimental (in-vivo and in-vitro) data. The model was subjected to 500 N compressive Follower Load (FL) combined with 7.5 Nm flexion (FLX) or extension (EXT) moments. Load-sharing was expressed as percentage of total internal force/moment developed along the spine that each spinal component carried. These internal forces and moments were determined at the discs centres and included the applied load and the resisting forces in the ligaments and facet joints. The contribution of the facet joints and ligaments in supporting bending moments produced additional forces and moments in the discs. The intervertebral discs carried up to 81% and 68% of the total internal force in case of FL combined with FLX and EXT, respectively. The ligaments withstood up to 67% and 81% of the total internal moment in cases of FL combined with EXT and FLX, respectively. Contribution of the facet joints in resisting internal force and moment was noticeable at levels L4-S1 only particularly in case of FL combined with EXT and reached up 29% and 52% of the internal moment and force, respectively. This study demonstrated that spinal load-sharing depended on applied load and varied along the spine.
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Affiliation(s)
- Sadegh Naserkhaki
- Department of Civil and Environmental Engineering, University of Alberta, Canada
| | - Jacob L Jaremko
- Department of Radiology and Diagnostic Imaging, University of Alberta, Canada
| | - Samer Adeeb
- Department of Civil and Environmental Engineering, University of Alberta, Canada
| | - Marwan El-Rich
- Department of Civil and Environmental Engineering, University of Alberta, Canada.
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Hartman RA, Yurube T, Ngo K, Merzlak NE, Debski RE, Brown BN, Kang JD, Sowa GA. Biological responses to flexion/extension in spinal segments ex-vivo. J Orthop Res 2015; 33:1255-64. [PMID: 25865090 DOI: 10.1002/jor.22900] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 03/10/2015] [Indexed: 02/04/2023]
Abstract
Mechanical loading is a salient factor in the progression of spinal disorders that contribute to back pain. Biological responses to loading modes like flexion/extension (F/E) in relevant spinal tissues remain unstudied. A novel, multi-axial experimental system was developed to subject viable functional spinal units (FSUs) to complex, in-situ loading. The objective was to determine biological effects of F/E in multiple spinal tissues-annulus fibrosus, nucleus pulposus, facet cartilage, and ligamentum flavum. Rabbit lumbar FSUs were mounted in a bioreactor within a robotic testing system. FSUs underwent small (0.17/0.05 Nm) and large (0.5/0.15 Nm) range-of-motion F/E for 1 or 2 h of cycling. Outcomes in each tissue, compared to unloaded FSUs, included (i) relative mRNA expression of catabolic (MMP-1, 3 and ADAMTS-5), pro-inflammatory (COX-2), and anabolic (ACAN) genes and (ii) immunoblotting of aggrecan degradation. Total energy applied to FSUs increased in groups subject to large range-of-motion and 2-h cycling, and moment relaxation was higher with large range-of-motion. F/E significantly modulated MMP1,-3 and COX-2 in facet cartilage and MMP-3 and ACAN in annulus fibrosus. Large range-of-motion loading increased MMP-mediated aggrecan fragmentation in annulus fibrosus. Biological responses to complex loading ex vivo showed variation among spinal tissues that reflect tissue structure and mechanical loading in F/E.
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Affiliation(s)
- Robert A Hartman
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, 3471 5th Avenue, Pittsburgh, Pennsylvania, 15213.,Department of Bioengineering, University of Pittsburgh, 300 Technology Drive, 360B Center for Bioengineering, Pittsburgh, Pennsylvania, 15219
| | - Takashi Yurube
- Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
| | - Kevin Ngo
- Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
| | - Nicolas E Merzlak
- Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
| | - Richard E Debski
- Department of Bioengineering, University of Pittsburgh, 300 Technology Drive, 360B Center for Bioengineering, Pittsburgh, Pennsylvania, 15219.,Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
| | - Bryan N Brown
- Department of Bioengineering, University of Pittsburgh, 300 Technology Drive, 360B Center for Bioengineering, Pittsburgh, Pennsylvania, 15219.,McGowan Institute for Regenerative Medicine, 450 Technology Drive, Suite 300, Pittsburgh, Pennsylvania, 15219
| | - James D Kang
- Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
| | - Gwendolyn A Sowa
- Department of Physical Medicine and Rehabilitation, University of Pittsburgh, 3471 5th Avenue, Pittsburgh, Pennsylvania, 15213.,Department of Bioengineering, University of Pittsburgh, 300 Technology Drive, 360B Center for Bioengineering, Pittsburgh, Pennsylvania, 15219.,Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, Pennsylvania, 15261
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Abstract
STUDY DESIGN An in vitro biomechanical human cadaveric study of T1-T12 thoracic specimens was performed with 4 conditions (with and without rib cage, instrumented and uninstrumented) in flexion-extension, lateral bending, and axial rotation. OBJECTIVE The objective was to understand the influence of the rib cage on motion and stiffness parameters of the human cadaveric thoracic spine. Hypotheses tested for overall motion in all modes of bending for both uninstrumented and instrumented specimens were (i) in-plane range of motion and neutral and elastic zones will be greater without the rib cage, (ii) neutral and elastic zone stiffness values will be different for specimens without the rib cage, and (iii) out-of-plane rotations will be different for specimens without the rib cage. SUMMARY OF BACKGROUND DATA The rib cage is presumed to provide significant stability to the thoracic spine, but no studies have been conducted to determine the influence of the rib cage in both uninstrumented and instrumented conditions in the full thoracic human cadaveric specimens. METHODS Seven human cadaveric spine specimens (T1-T12) with 4 conditions (with and without rib cage, instrumented and uninstrumented) were subjected to 5 N·m pure moments in flexion-extension, lateral bending, and axial rotation. Range of motion, neutral and elastic zones, neutral and elastic zone stiffness values, and out-of-plane rotations were calculated for the overall specimen. RESULTS In-plane range of motion was significantly higher without a rib cage for most modes of bending. Out-of-plane motions were also influenced by the rib cage. Neutral zone stiffness was significantly higher with a rib cage present. CONCLUSION Testing without a rib cage yields different motion and stiffness measures, directly impacting the translation of research results to clinical interpretation. Researchers should consider these differences when evaluating the mechanical impact of surgical procedures or instrumentation in cadaveric or computational models. LEVEL OF EVIDENCE 5.
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Mannen EM, Ranu SS, Villanueva AM, Friis EA. Validation of a Novel Spine Test Machine. J Med Device 2015. [DOI: 10.1115/1.4028759] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A novel spine test machine was developed for physiological loading of spinal segments. It can be used in conjunction with external motion-capture systems (EMCS) to measure angular displacement, but can also measure in-plane rotations directly, though the inherent error is unknown. This study quantified error inherent in the displacement measurement of the machine. Synthetic specimens representative of cadaveric spinal specimens were tested. Machine displacement was compared to EMCS displacement. The maximum machine displacement error was <2 deg for lumbar and thoracic specimens. The authors suggest that researchers use EMCS in conjunction with the test machine when high accuracy measurements are required.
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Affiliation(s)
- Erin M. Mannen
- Mechanical Engineering, The University of Kansas, 1530 W. 15th Street, Learned Hall, Room 3138, Lawrence, KS 66045 e-mail:
| | - Sahibjit S. Ranu
- The University of Kansas, Bioengineering Graduate Program, 1530 W 15th Street, Learned Hall Room 3135A, Lawrence, KS 66045 e-mail:
| | - Ana M. Villanueva
- Mechanical Engineering, The University of Kansas, 1530 W 15th Street, Learned Hall Room 3138, Lawrence, KS 66045 e-mail:
| | - Elizabeth A. Friis
- Mechanical Engineering, The University of Kansas, 1530 W 15th Street, Learned Hall Room 3138, Lawrence, KS 66045 e-mail:
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