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Hsiao CK, Hsiao HY, Tsai YJ, Hsu CM, Tu YK. Influence of Simulated State of Disc Degeneration and Axial Stiffness of Coupler in a Hybrid Performance Stabilisation System on the Biomechanics of a Spine Segment Model. Bioengineering (Basel) 2023; 10:1042. [PMID: 37760144 PMCID: PMC10525081 DOI: 10.3390/bioengineering10091042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 08/21/2023] [Accepted: 09/04/2023] [Indexed: 09/29/2023] Open
Abstract
Spinal fusion surgery leads to the restriction of mobility in the vertebral segments postoperatively, thereby causing stress to rise at the adjacent levels, resulting in early degeneration and a high risk of adjacent vertebral fractures. Thus, to address this issue, non-fusion surgery applies some pedicle screw-based dynamic stabilisation systems to provide stability and micromotion, thereby reducing stress in the fusion segments. Among these systems, the hybrid performance stabilisation system (HPSS) combines a rigid rod, transfer screw, and coupler design to offer a semi-rigid fixation method that preserves some mobility near the fusion site and reduces the adjacent segment compensatory effects. However, further research and confirmation are needed regarding the biomechanical effects of the dynamic coupler stiffness of the HPSS on the intrinsic degenerated adjacent segment. Therefore, this study utilised the finite element method to investigate the impact of the coupler stiffness of the HPSS on the mobility of the lumbar vertebral segments and the stress distribution in the intervertebral discs under flexion, extension, and lateral bending, as well as the clinical applicability of the HPSS on the discs with intrinsic moderate and severe degeneration at the adjacent level. The analytical results indicated that, regardless of the degree of disc degeneration, the use of a dynamic coupler stiffness of 57 N/mm in the HPSS may reduce the stress concentrations at the adjacent levels. However, for severely degenerated discs, the postoperative stress on the adjacent segments with the HPSS was still higher compared with that of the discs with moderate degeneration. We conclude that, when the discs had moderate degeneration, increasing the coupler stiffness led to a decrease in disc mobility. In the case of severe disc degeneration, the effect on disc mobility by coupler stiffness was less pronounced. Increasing the coupler stiffness ked to higher stress on intervertebral discs with moderate degeneration, while its effect on stress was less pronounced for discs with severe degeneration. It is recommended that patients with severe degeneration who undergo spinal dynamic stabilisation should remain mindful of the risk of accelerated adjacent segment degeneration.
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Affiliation(s)
- Chih-Kun Hsiao
- Department of Medical Research, E-Da Hospital, I-Shou University, Kaohsiung 824, Taiwan; (C.-K.H.); (Y.-J.T.)
- Department of Orthopedics, E-Da Hospital, I-Shou University, Kaohsiung 824, Taiwan;
| | - Hao-Yuan Hsiao
- Department of Orthopedics, E-Da Hospital, I-Shou University, Kaohsiung 824, Taiwan;
- Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung 804, Taiwan
| | - Yi-Jung Tsai
- Department of Medical Research, E-Da Hospital, I-Shou University, Kaohsiung 824, Taiwan; (C.-K.H.); (Y.-J.T.)
| | - Chao-Ming Hsu
- Department of Mechanical Engineering, National Kaohsiung University of Science and Technology, Kaohsiung 824, Taiwan
| | - Yuan-Kun Tu
- Department of Orthopedics, E-Da Hospital, I-Shou University, Kaohsiung 824, Taiwan;
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Tavana S, Davis B, Canali I, Scott K, Leong JJH, Freedman BA, Newell N. A novel tool to quantify in vivo lumbar spine kinematics and 3D intervertebral disc strains using clinical MRI. J Mech Behav Biomed Mater 2023; 140:105730. [PMID: 36801782 DOI: 10.1016/j.jmbbm.2023.105730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 01/27/2023] [Accepted: 02/11/2023] [Indexed: 02/15/2023]
Abstract
Medical imaging modalities that calculate tissue morphology alone cannot provide direct information regarding the mechanical behaviour of load-bearing musculoskeletal organs. Accurate in vivo measurement of spine kinematics and intervertebral disc (IVD) strains can provide important information regarding the mechanical behaviour of the spine, help to investigate the effects of injuries on the mechanics of the spine, and assess the effectiveness of treatments. Additionally, strains can serve as a functional biomechanical marker for detecting normal and pathologic tissues. We hypothesised that combining digital volume correlation (DVC) with 3T clinical MRI can provide direct information regarding the mechanics of the spine. Here, we have developed a novel non-invasive tool for in vivo displacement and strain measurement within the human lumbar spine and we used this tool to calculate lumbar kinematics and IVD strains in six healthy subjects during lumbar extension. The proposed tool enabled spine kinematics and IVD strains to be measured with errors that did not exceed 0.17 mm and 0.5%, respectively. The findings of the kinematics study identified that during extension the lumbar spine of healthy subjects experiences total 3D translations ranging from 1 mm to 4.5 mm for different vertebral levels. The findings of strain analysis identified that the average of the maximum tensile, compressive, and shear strains for different lumbar levels during extension ranged from 3.5% to 7.2%. This tool can provide base-line data that can be used to describe the mechanical environment of healthy lumbar spine, which can help clinicians manage preventative treatments, define patient-specific treatments, and to monitor the effectiveness of surgical and non-surgical interventions.
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Affiliation(s)
- S Tavana
- Department of Bioengineering, Imperial College London, London, UK
| | - B Davis
- Fortius Clinic, Fitzhardinge Street, London, UK
| | - I Canali
- Fortius Clinic, Fitzhardinge Street, London, UK
| | - K Scott
- Fortius Clinic, Fitzhardinge Street, London, UK
| | - J J H Leong
- Royal National Orthopaedic Hospital, Stanmore, UK; UCL Institute of Orthopaedics and Musculoskeletal Science, London, UK
| | | | - N Newell
- Department of Bioengineering, Imperial College London, London, UK.
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Zheng HD, Sun YL, Kong DW, Yin MC, Chen J, Lin YP, Ma XF, Wang HS, Yuan GJ, Yao M, Cui XJ, Tian YZ, Wang YJ. Deep learning-based high-accuracy quantitation for lumbar intervertebral disc degeneration from MRI. Nat Commun 2022; 13:841. [PMID: 35149684 PMCID: PMC8837609 DOI: 10.1038/s41467-022-28387-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 01/21/2022] [Indexed: 11/14/2022] Open
Abstract
To help doctors and patients evaluate lumbar intervertebral disc degeneration (IVDD) accurately and efficiently, we propose a segmentation network and a quantitation method for IVDD from T2MRI. A semantic segmentation network (BianqueNet) composed of three innovative modules achieves high-precision segmentation of IVDD-related regions. A quantitative method is used to calculate the signal intensity and geometric features of IVDD. Manual measurements have excellent agreement with automatic calculations, but the latter have better repeatability and efficiency. We investigate the relationship between IVDD parameters and demographic information (age, gender, position and IVDD grade) in a large population. Considering these parameters present strong correlation with IVDD grade, we establish a quantitative criterion for IVDD. This fully automated quantitation system for IVDD may provide more precise information for clinical practice, clinical trials, and mechanism investigation. It also would increase the number of patients that can be monitored.
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Affiliation(s)
- Hua-Dong Zheng
- School of Automation and Mechanical Engineering, Shanghai University, Shanghai, 200072, China
- Shanghai Key Laboratory of Intelligent Manufacturing and Robotics, Shanghai, 200072, China
| | - Yue-Li Sun
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China
- Spine Research Institute, Shanghai Academy of TCM, Shanghai, 200032, China
- Key Laboratory of the Ministry of Education of Chronic Musculoskeletal Disease, Shanghai, 200032, China
| | - De-Wei Kong
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China
| | - Meng-Chen Yin
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China
- Key Laboratory of the Ministry of Education of Chronic Musculoskeletal Disease, Shanghai, 200032, China
| | - Jiang Chen
- Dongzhimen Hospital, Beijing University of Chinese Medicine, Beijing, 100700, China
| | - Yong-Peng Lin
- Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, 510120, China
| | - Xue-Feng Ma
- Shenzhen Pingle Orthopedics Hospital, Shenzhen, 518118, China
| | - Hong-Shen Wang
- Guangdong Provincial Hospital of Chinese Medicine, Guangzhou, 510120, China
| | - Guang-Jie Yuan
- School of Automation and Mechanical Engineering, Shanghai University, Shanghai, 200072, China
- Shanghai Key Laboratory of Intelligent Manufacturing and Robotics, Shanghai, 200072, China
| | - Min Yao
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China
- Spine Research Institute, Shanghai Academy of TCM, Shanghai, 200032, China
- Key Laboratory of the Ministry of Education of Chronic Musculoskeletal Disease, Shanghai, 200032, China
| | - Xue-Jun Cui
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China
- Spine Research Institute, Shanghai Academy of TCM, Shanghai, 200032, China
- Key Laboratory of the Ministry of Education of Chronic Musculoskeletal Disease, Shanghai, 200032, China
| | - Ying-Zhong Tian
- School of Automation and Mechanical Engineering, Shanghai University, Shanghai, 200072, China.
- Shanghai Key Laboratory of Intelligent Manufacturing and Robotics, Shanghai, 200072, China.
| | - Yong-Jun Wang
- Longhua Hospital, Shanghai University of TCM, Shanghai, 200032, China.
- Spine Research Institute, Shanghai Academy of TCM, Shanghai, 200032, China.
- Key Laboratory of the Ministry of Education of Chronic Musculoskeletal Disease, Shanghai, 200032, China.
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Zehra U, Noel-Barker N, Marshall J, Adams MA, Dolan P. Associations Between Intervertebral Disc Degeneration Grading Schemes and Measures of Disc Function. J Orthop Res 2019; 37:1946-1955. [PMID: 31042314 DOI: 10.1002/jor.24326] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 04/08/2019] [Indexed: 02/04/2023]
Abstract
Disc degeneration is a major cause of spinal dysfunction and pain, but grading schemes concentrate on tissue changes rather than altered function. The aim of this study was to compare disc degeneration grading systems with each other, and with biomechanical measures of disc function. Sixty-six motion segments (T8-9 to L5-S1) were dissected from cadavers aged 48-98 years. Disc function was assessed by measuring nucleus pressure (IDP) and maximum stresses in the annulus under 1 kN of compression. Detailed "scores" of disc degeneration were based on independent radiographic, macroscopic, and microscopic evaluations. For each evaluation, scores were used to assign a degeneration "grade" (I-IV), and functional measures were then correlated with degeneration scores and grades. Results showed that all measures were reliable (intraclass correlation coefficients: 0.82-0.99). Macroscopic and microscopic assessments were highly correlated with each other (r: 0.57-0.89, p < 0.001) but only weakly correlated with radiographic features. The overall macroscopic and microscopic scores of degeneration increased significantly with age and at lower spinal levels, although the influence of age was less marked in the case of the microscopic scores. IDP decreased with age and at lower spinal levels, but annulus stresses were more variable. Importantly, IDP and annulus stresses decreased consistently with all measures of disc degeneration, and these associations remained strong after controlling for age, gender, and spinal level. We conclude that radiographic and tissue-based assessments of disc degeneration are consistent with each other, and are more closely related to mechanical (dys)function than to age or spinal level. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1946-1955, 2019.
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Affiliation(s)
- Uruj Zehra
- Department of Anatomy, University of Health Sciences, Lahore, Pakistan
| | - Natasha Noel-Barker
- Centre for Applied Anatomy, Faculty of Health Sciences, University of Bristol, Southwell Street Bristol, Bristol, BS2 8EJ, UK
| | - John Marshall
- Centre for Applied Anatomy, Faculty of Health Sciences, University of Bristol, Southwell Street Bristol, Bristol, BS2 8EJ, UK
| | - Michael A Adams
- Centre for Applied Anatomy, Faculty of Health Sciences, University of Bristol, Southwell Street Bristol, Bristol, BS2 8EJ, UK
| | - Patricia Dolan
- Centre for Applied Anatomy, Faculty of Health Sciences, University of Bristol, Southwell Street Bristol, Bristol, BS2 8EJ, UK
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Luo J, Annesley-Williams DJ, Adams MA, Dolan P. How are adjacent spinal levels affected by vertebral fracture and by vertebroplasty? A biomechanical study on cadaveric spines. Spine J 2017; 17:863-874. [PMID: 28167249 DOI: 10.1016/j.spinee.2017.01.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/21/2016] [Accepted: 01/30/2017] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Spinal injuries and surgery may have important effects on neighboring spinal levels, but previous investigations of adjacent-level biomechanics have produced conflicting results. We use "stress profilometry" and noncontact strain measurements to investigate thoroughly this long-standing problem. PURPOSE This study aimed to determine how vertebral fracture and vertebroplasty affect compressive load-sharing and vertebral deformations at adjacent spinal levels. STUDY DESIGN We conducted mechanical experiments on cadaver spines. METHODS Twenty-eight cadaveric spine specimens, comprising three thoracolumbar vertebrae and the intervening discs and ligaments, were dissected from fourteen cadavers aged 67-92 years. A needle-mounted pressure transducer was used to measure the distribution of compressive stress across the anteroposterior diameter of both intervertebral discs. "Stress profiles" were analyzed to quantify intradiscal pressure (IDP) and concentrations of compressive stress in the anterior and posterior annulus. Summation of stresses over discrete areas yielded the compressive force acting on the anterior and posterior halves of each vertebral body, and the compressive force resisted by the neural arch. Creep deformations of vertebral bodies under load were measured using an optical MacReflex system. All measurements were repeated following compressive injury to one of the three vertebrae, and again after the injury had been treated by vertebroplasty. The study was funded by a grant from Action Medical Research, UK ($143,230). Authors of this study have no conflicts of interest to disclose. RESULTS Injury usually involved endplate fracture, often combined with deformation of the anterior cortex, so that the affected vertebral body developed slight anterior wedging. Injury reduced IDP at the affected level, to an average 47% of pre-fracture values (p<.001), and transferred compressive load-bearing from nucleus to annulus, and also from disc to neural arch. Similar but reduced effects were seen at adjacent (non-fractured) levels, where mean IDP was reduced to 73% of baseline values (p<.001). Vertebroplasty partially reversed these changes, increasing mean IDP to 76% and 81% of baseline values at fractured and adjacent levels, respectively. Injury also increased creep deformation of the vertebral body under load, especially in the anterior region where a 14-fold increase was observed at the fractured level and a threefold increase was observed at the adjacent level. Vertebroplasty also reversed these changes, reducing deformation of the anterior vertebral body (compared with post-fracture values) by 62% at the fractured level, and by 52% at the adjacent level. CONCLUSIONS Vertebral fracture adversely affects compressive load-sharing and increases vertebral deformations at both fractured and adjacent levels. All effects can be partially reversed by vertebroplasty.
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Affiliation(s)
- Jin Luo
- School of Applied Sciences, London South Bank University, 103 Borough Rd, London SE1 0AA, UK
| | - Deborah J Annesley-Williams
- Department of Neuroradiology, Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Derby Rd, Nottingham NG7 2UH, UK
| | - Michael A Adams
- Centre of Applied Anatomy, University of Bristol, Southwell St, Bristol, BS2 8EJ, UK
| | - Patricia Dolan
- Centre of Applied Anatomy, University of Bristol, Southwell St, Bristol, BS2 8EJ, UK.
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Luo J, Pollintine P, Annesley-Williams D, Dolan P, Adams M. Vertebroplasty reduces progressive ׳creep’ deformity of fractured vertebrae. J Biomech 2016; 49:869-874. [DOI: 10.1016/j.jbiomech.2015.09.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 08/04/2015] [Accepted: 09/14/2015] [Indexed: 01/25/2023]
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Landham PR, Baker-Rand HLA, Gilbert SJ, Pollintine P, Annesley-Williams DJ, Adams MA, Dolan P. Is kyphoplasty better than vertebroplasty at restoring form and function after severe vertebral wedge fractures? Spine J 2015; 15:721-32. [PMID: 25450656 DOI: 10.1016/j.spinee.2014.11.017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 11/06/2014] [Accepted: 11/21/2014] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT The vertebral augmentation procedures, vertebroplasty and kyphoplasty, can relieve pain and facilitate mobilization of patients with osteoporotic vertebral fractures. Kyphoplasty also aims to restore vertebral body height before cement injection and so may be advantageous for more severe fractures. PURPOSE The purpose of this study was to compare the ability of vertebroplasty and kyphoplasty to restore vertebral height, shape, and mechanical function after severe vertebral wedge fractures. STUDY DESIGN/SETTING This is a biomechanical and radiographic study using human cadaveric spines. METHODS Seventeen pairs of thoracolumbar "motion segments" from cadavers aged 70-98 years were injured, in a two-stage process involving flexion and compression, to create severe anterior wedge fractures. One of each pair underwent vertebroplasty and the other kyphoplasty. Specimens were then compressed at 1 kN for 1 hour to allow consolidation. Radiographs were taken before and after injury, after treatment, and after consolidation. At these same time points, motion segment compressive stiffness was assessed, and intervertebral disc "stress profiles" were obtained to characterize the distribution of compressive stress on the vertebral body and neural arch. RESULTS On average, injury reduced anterior vertebral body height by 34%, increased its anterior wedge angle from 5.0° to 11.4°, reduced intradiscal (nucleus) pressure and motion segment stiffness by 96% and 44%, respectively, and increased neural arch load bearing by 57%. Kyphoplasty caused 97% of the anterior height loss to be regained immediately, although this reduced to 79% after consolidation. Equivalent gains after vertebroplasty were significantly lower: 59% and 47%, respectively (p<.001). Kyphoplasty reduced vertebral wedging more than vertebroplasty (p<.02). Intradiscal pressure, neural arch load bearing, and motion segment compressive stiffness were restored significantly toward prefracture values after both augmentation procedures, even after consolidation, but these mechanical effects were similar for kyphoplasty and vertebroplasty. CONCLUSIONS After severe vertebral wedge fractures, vertebroplasty and kyphoplasty were equally effective in restoring mechanical function. However, kyphoplasty was better able to restore vertebral height and reverse wedge deformity.
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Affiliation(s)
- Priyan R Landham
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK
| | - Holly L A Baker-Rand
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK
| | - Samuel J Gilbert
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK
| | - Phillip Pollintine
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK
| | | | - Michael A Adams
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK
| | - Patricia Dolan
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell St, Bristol BS2 8EJ, UK.
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Liu Q, Wang TY, Yang XP, Li K, Gao LL, Zhang CQ, Guo YH. Strain distribution in the intervertebral disc under unconfined compression and tension load by the optimized digital image correlation technique. Proc Inst Mech Eng H 2014; 228:486-493. [DOI: 10.1177/0954411914529756] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The unconfined compression and tension experiments of the intervertebral disc were conducted by applying an optimized digital image correlation technique, and the internal strain distribution was analysed for the disc. It was found that the axial strain values of different positions increased obviously with the increase in loads, while inner annulus fibrosus and posterior annulus fibrosus experienced higher axial strains than the outer annulus fibrosus and anterior annulus fibrosus. Deep annulus fibrosus exhibited higher compressive and tensile axial strains than superficial annulus fibrosus for the anterior region, while there was an opposite result for the posterior region. It was noted that all samples demonstrated a nonlinear stress–strain profile in the process of deforming, and an elastic region was shown once the sample was deformed beyond its toe region.
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Affiliation(s)
- Qing Liu
- Tianjin Key Laboratory for Control Theory & Applications in Complicated Industry Systems, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, P.R. China
| | - Tai-Yong Wang
- School of Mechanical Engineering, Tianjin University, Tianjin, P.R. China
| | - Xiu-Ping Yang
- Tianjin Key Laboratory for Control Theory & Applications in Complicated Industry Systems, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, P.R. China
| | - Kun Li
- School of Electronic Information Engineering, Tianjin University of Technology, Tianjin, P.R. China
| | - Li-Lan Gao
- Tianjin Key Laboratory for Control Theory & Applications in Complicated Industry Systems, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, P.R. China
| | - Chun-Qiu Zhang
- Tianjin Key Laboratory for Control Theory & Applications in Complicated Industry Systems, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, P.R. China
| | - Yue-Hong Guo
- Tianjin Key Laboratory for Control Theory & Applications in Complicated Industry Systems, School of Mechanical Engineering, Tianjin University of Technology, Tianjin, P.R. China
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Adams MA, Dolan P. Biomechanics of vertebral compression fractures and clinical application. Arch Orthop Trauma Surg 2011; 131:1703-10. [PMID: 21805360 DOI: 10.1007/s00402-011-1355-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Indexed: 12/27/2022]
Abstract
Local biomechanical factors in the etiology of vertebral compression fractures are reviewed. The vertebral body is particularly vulnerable to compression fracture when its bone mineral density (BMD) falls with age. However, the risk of fracture, and the type of fracture produced, does not depend simply on BMD. Equally important is the state of degeneration of the adjacent intervertebral discs, which largely determines how compressive forces are distributed over the vertebral body. Disc height also influences load-sharing between the vertebral body and neural arch, and hence by Wolff's Law can influence regional variations in trabecular density within the vertebral body. Vertebral deformity is not entirely attributable to trauma: it can result from the gradual accumulation of fatigue damage, and can progress by a quasi-continuous process of "creep". Cement injection techniques such as vertebroplasty and kyphoplasty are valuable in the treatment of these fractures. Both techniques can stiffen a fractured vertebral body, and kyphoplasty may contribute towards restoring its height. The presence of cement can limit endplate deformation, and thereby partially reverse the adverse changes in load-sharing which follow vertebral fracture. Cement also reduces time-dependent "creep" deformation of damaged vertebrae.
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Affiliation(s)
- Michael A Adams
- Centre for Comparative and Clinical Anatomy, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK.
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Luo J, Bertram W, Sangar D, Adams MA, Annesley-Williams DJ, Dolan P. Is kyphoplasty better than vertebroplasty in restoring normal mechanical function to an injured spine? Bone 2010; 46:1050-7. [PMID: 20004264 DOI: 10.1016/j.bone.2009.11.036] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 11/30/2009] [Accepted: 11/30/2009] [Indexed: 11/22/2022]
Abstract
INTRODUCTION Kyphoplasty is gaining in popularity as a treatment for painful osteoporotic vertebral body fracture. It has the potential to restore vertebral shape and reduce spinal deformity, but the actual clinical and mechanical benefits of kyphoplasty remain unclear. In a cadaveric study, we compare the ability of vertebroplasty and kyphoplasty to restore spine mechanical function, and vertebral body shape, following vertebral fracture. METHODS Fifteen pairs of thoracolumbar "motion segments" (two vertebrae with the intervening disc and ligaments) were obtained from cadavers aged 42-96 years. All specimens were compressed to induce vertebral body fracture. Then one of each pair underwent vertebroplasty and the other kyphoplasty, using 7 ml of polymethylmethacrylate cement. Augmented specimens were compressed for 2 hours to allow consolidation. At each stage of the experiment, motion segment stiffness was measured in bending and compression, and the distribution of loading on the vertebrae was determined by pulling a miniature pressure transducer through the intervertebral disc. Disc pressure measurements were performed in flexed and extended postures with a compressive load of 1.0-1.5 kN. They revealed the intradiscal pressure (IDP) which acts on the central vertebral body, and they enabled compressive load-bearing by the neural arch (F(N)) to be calculated. Changes in vertebral height and wedge angle were assessed from radiographs. The volume of leaked cement was determined by water displacement. Volumetric bone mineral density (BMD) of each vertebral body was calculated using DXA and water displacement. RESULTS Vertebral fracture reduced motion segment compressive stiffness by 55%, and bending stiffness by 39%. IDP fell by 61-88%, depending on posture. F(N) increased from 15% to 36% in flexion and from 30% to 58% in extension (P<0.001). Fracture reduced vertebral height by an average 0.94 mm and increased vertebral wedging by 0.95 degrees (P<0.001). Vertebroplasty and kyphoplasty were equally effective in partially restoring all aspects of mechanical function (including stiffness, IDP, and F(N)), but vertebral wedging was reduced only by kyphoplasty (P<0.05). Changes in mechanical function and vertebral wedging were largely maintained after consolidation, but height restoration was not. Cement leakage was similar for both treatments. CONCLUSIONS Vertebroplasty and kyphoplasty were equally effective at restoring mechanical function to an injured spine. Only kyphoplasty was able to reverse minor vertebral wedging.
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Affiliation(s)
- Jin Luo
- Department of Anatomy, University of Bristol, Southwell Street, Bristol BS2 8EJ, UK
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Abstract
STUDY DESIGN Mechanical testing of cadaveric spines. OBJECTIVE To test the hypothesis that, in the ageing spine, vertebrae deform more than discs, and contribute to time-dependent creep. SUMMARY OF BACKGROUND DATA Intervertebral discs and vertebrae deform under load, narrowing the intervertebral foramen and increasing the risk of nerve root entrapment. Little is known about compressive deformations when elderly spines are subjected to sustained physiologic loading. METHODS A total of 117 thoracolumbar motion segments, aged 19 to 96 yrs (mean, 69), were subjected to 1kN compressive loading for 0.5, 1, or 2 hours. Deformations during the first 7 seconds were designated "elastic" and subsequent deformations as "creep". A 3-parameter model was fitted to experimental data in order to characterize their viscous modulus E1, elastic modulus E2 (initial stiffness), and viscosity eta (resistance to fluid flow). Intradiscal pressure (IDP) was measured using a miniature needle-mounted transducer. In 17 specimens loaded for 0.5 hours, an optical MacReflex system measured compressive deformations separately in the disc and each vertebral body. RESULTS On average, the disc contributed 28% of the spine's elastic deformation, 51% of the creep deformation, and 38% of total deformation. Elastic, creep, and total deformations of 84 motion segments in 2-hour tests averaged 0.87, 1.37, and 2.24 mm respectively. Measured deformations were predicted accurately by the model (average r2 = 0.97), but E1, E2, and eta depended on the duration of loading. E1 and eta decreased with advancing age and disc degeneration, in proportion to falling IDP (P < 0.001). Total compressive deformation increased with age, but rarely exceeded 3 mm. CONCLUSION When the ageing spine is compressed, vertebral bodies show greater elastic deformations than intervertebral discs, and creep by a similar amount. Responses to axial compression depend largely on IDP, but deformations appear to be limited by impaction of adjacent neural arches. Total compressive deformations are sufficient to cause foraminal stenosis in some individuals.
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Vertebroplasty: only small cement volumes are required to normalize stress distributions on the vertebral bodies. Spine (Phila Pa 1976) 2009; 34:2865-73. [PMID: 20010394 DOI: 10.1097/brs.0b013e3181b4ea1e] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN.: Biomechanical study of vertebroplasty in cadaver motion segments. OBJECTIVES.: To determine how the volume of injected cement influences: (a) stress distributions on fractured and adjacent vertebral bodies, (b) load-sharing between the vertebral bodies and neural arch, and (c) cement leakage. SUMMARY OF BACKGROUND DATA.: Vertebroplasty is increasingly used to treat vertebral fractures, but there are problems concerning adjacent level fracture and cement leakage, both of which may depend on the volume of injected cement. METHODS.: Nineteen thoracolumbar motion segments from 13 cadavers (42-91 years) were loaded to induce fracture. Fractured vertebrae received 2 sequential injections (VP1 and VP2) of 3.5 cm of polymethylmethacrylate cement. Before and after each intervention, motion segment stiffness was measured in compression and in bending, and "stress profilometry" was used to quantify the distribution of compressive stress in the intervertebral disc (which presses equally on fractured and adjacent vertebrae). Stress profiles were obtained by pulling a pressure transducer through the disc while the motion segment was compressed in flexed and extended postures. Stress profiles yielded the intradiscal pressure (IDP), the magnitude of stress peaks in the anterior and posterior (SPP) anulus, and the percentage of the applied compressive force resisted by the neural arch (FN). Cement leakage and vertebral body volume were quantified using water-immersion, and the percentage cement fill was estimated. RESULTS.: Bending and compressive stiffness fell by 37% and 50% respectively following fracture, and were restored only after VP2. Depending on posture, IDP fell by 59-85% after fracture whereas SPP increased by 107- 362%. VP1 restored IDP and SPP to prefracture values, and VP2 produced no further changes. Fracture increased FN from 11% to 39% in flexion, and from 33% to 59% in extension. FN was restored towards prefracture values only after VP2. Cement leakage increased after VP2 and was negatively correlated to vertebral body volume. Following VP2, increases in IDP and compressive stiffness were proportional to percentage fill. CONCLUSION.: About 3.5 cm of PMMA largely restored normal stress distributions to fractured and adjacent vertebral bodies, but 7 cm were required to restore motion segment stiffness and load-sharing between the vertebral bodies and neural arch. Cement leakage, IDP and compressive stiffness all increased with percentage fill.
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Adams MA, Dolan P, McNally DS. The internal mechanical functioning of intervertebral discs and articular cartilage, and its relevance to matrix biology. Matrix Biol 2009; 28:384-9. [DOI: 10.1016/j.matbio.2009.06.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Revised: 06/18/2009] [Accepted: 06/22/2009] [Indexed: 01/01/2023]
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Malátová R, Dřevikovská P. Testing procedures for abdominal muscles using the muscle dynamometer SD02. Proc Inst Mech Eng H 2009; 223:1041-8. [DOI: 10.1243/09544119jeim575] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The aim of this study was to compare two tests both frequently used for determination of the state of the lumbar spine muscle system during static and dynamic loads. The sit-up test is a commonly used terrain test, while the diaphragm test is a more exact laboratory procedure. For both tests, measurements conducted by the muscular dynamometer SD02 were used to assure congruency in evaluation. The tests are based on the general information that the muscles of the deep stabilizing spine system (DSSS) are interconnected and form one functional unit, and that dysfunction of just one of these muscles may cause total dysfunction of the whole muscle system. It is therefore expected that the participation and force generated by the largest muscles of the area, musculus rectus abdominis and musculus transversus abdominis, will be comparable also during the testing procedures. Forty-five healthy women joined in the research, with the average age of 21.6 years. The results obtained were statistically evaluated using Statistica 6. The results showed the clear incapability of the sit-up test to indicate correctly the imbalances of the muscles of the DSSS, also implying that the tested subjects suffer to a high degree from dysfunctions of the DSSS.
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Affiliation(s)
- R Malátová
- Department of Physical Education and Sport, Faculty of Pedagogy, University of Southern Bohemia, České Budějovice, Czech Republic
| | - P Dřevikovská
- Department of Physical Education and Sport, Faculty of Pedagogy, University of Southern Bohemia, České Budějovice, Czech Republic
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Skrzypiec DM, Pollintine P, Przybyla A, Dolan P, Adams MA. The internal mechanical properties of cervical intervertebral discs as revealed by stress profilometry. EUROPEAN SPINE JOURNAL : OFFICIAL PUBLICATION OF THE EUROPEAN SPINE SOCIETY, THE EUROPEAN SPINAL DEFORMITY SOCIETY, AND THE EUROPEAN SECTION OF THE CERVICAL SPINE RESEARCH SOCIETY 2007; 16:1701-9. [PMID: 17671801 PMCID: PMC2078298 DOI: 10.1007/s00586-007-0458-z] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 07/03/2007] [Accepted: 07/11/2007] [Indexed: 10/23/2022]
Abstract
Extensive anatomical differences suggest that cervical and lumbar discs may have functional differences also. We investigated human cervical discs using "stress profilometry". Forty-six cadaveric cervical motion segments aged 48-90 years were subjected to a compressive load of 200 N for 20 s, while compressive 'stress' was recorded along the posterior-anterior midline of the disc using a pressure transducer, side-mounted in a 0.9 mm diameter needle. Stress profiles were repeated with the transducer orientated horizontally and vertically, and with the specimen in neutral, flexed and extended postures. Profiles were repeated again following creep loading (150 N, 2 h) which simulated diurnal water loss in vivo. Stress profiles were reproducible, and measured "stress" at each location was proportional to applied load. Stress profiles usually showed a hydrostatic nucleus with regions of higher compressive stress concentrated anteriorly in flexion, and posteriorly in extension. Stress concentrations increased in degenerated discs and following creep. Some features were unique to cervical discs: many showed a stress gradient across their central regions, even though vertical and horizontal stresses were equal to each other, and stress concentrations in the posterior annulus were generally small. Central regions of many cervical discs show the characteristics of a "tethered fluid" which can equalise stress over small distances, but not large. This may be attributable to their fibrous texture. The small radial diameter of the cervical posterior annulus may facilitate buckling and thereby prevent it from sustaining high compressive stresses.
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Affiliation(s)
| | - Phillip Pollintine
- Department of Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ UK
| | | | - Patricia Dolan
- Department of Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ UK
| | - Michael A. Adams
- Department of Anatomy, University of Bristol, Southwell Street, Bristol, BS2 8EJ UK
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