- Email: [email protected]
Spine loading and deformation – From loading to recovery
Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Contents lists available at ScienceDirect
Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com
Editorial
Spine loading and deformation – From loading to recovery art ic l e i nf o Keywords: Spine Loads Deformation Intervertebral disc Biomechanics
1. Introduction There is ample evidence in the literature of a strong association between low back disorders and spine loading and deformation that are present particularly during repetitive heavy lifting and awkward postures (NIOSH, 1997). The human spine has the fundamental function of the support, control and transmission of upper trunk loads (i.e., body weight, loads carried in hands and on shoulders, inertial loads) while performing tasks and movements common in daily recreational, sport and workplace activities. Peak and repetitive loads and deformations at levels approaching tissue injury thresholds, jerky movements and sudden unforeseen perturbations regularly put this function (i.e., the resistant, reflex response, control and system stability) to the test. Acute or accumulated tissue injuries, degenerations, contaminations in neural network, deformities and instability likely increase the risk of further deteriorations and pain. Adequate knowledge of spine loading and deformation in various conditions and mechanical environments remains hence crucial for effective risk evaluation, workplace safety, prevention programs, rehabilitation, tissue regeneration, tissue replacement and surgery of the human spine. From early attempts on measurement of the intradiscal pressure (e.g., Nachemson and Morris, 1964), spinal shrinkage (e.g., Eklund and Corlett, 1984), intra-abdominal pressure (e.g., Davis, 1959), muscle electromyography activity (e.g., McGill and Norman, 1986) to more recent ones using instrumented vertebral implants (Rohlmann et al., 1999), researchers have aimed to estimate mechanical loading on the human spine in various activities. In parallel, in vitro studies have for long (e.g., Hirsch and Nachemson, 1954; Roaf, 1960) shed light on the passive resistance and failure mechanisms of the spinal components and tissues. While the foregoing measurements have substantially improved our understanding of the functional biomechanics of the spine in normal and injured conditions, it has long been recognized that they alone are not sufficient to quantify the complex mechanisms in action prior, during and subsequent to injuries. Computational models have hence been employed (e.g., Belytschko et al., 1974) with the http://dx.doi.org/10.1016/j.jbiomech.2016.02.024 0021-9290/& 2016 Elsevier Ltd. All rights reserved.
expectation to accurately determine the spatial and temporal variations of stresses, strains, fluid flow, cell viability and solute transport throughout the spinal tissues (see review paper; Schmidt et al., 2013). It has never been as evident that further meaningful progress in this field can only materialize through complementary investigations taking full consideration of all these tools.
2. Berlin workshop After about a year of its inception, the current workshop on spine loading and deformation, organized by Hendrik Schmidt and Aboulfazl Shirazi-Adl, took place with 75 participants from 14 countries around the globe at Julius Wolff Institute of Charité– Universitätsmedizin in Berlin during 3 days of July 2–4, 2015; http://workshop.spine-biomechanics.com/. The workshop aimed to gather researchers working in different disciplines and fields of application in health care, biological science, biomechanics and ergonomics together in order to share, discuss and re-examine the potentials of their recent works on the spine. Research topics covered trunk loads and motion measurements (imaging, sensors and video camera) and predictions during static and dynamic tasks with focus on the lumbar and thoracic spines. More than 50 renowned experts in the field were initially contacted. Submitted abstracts were evaluated and authors of accepted ones were invited to present their work at the meeting and submit an original paper for consideration in this special issue of the Journal of Biomechanics. In total 33 works were presented and 22 research papers finally accepted after peer review for inclusion in the current issue. The meeting ended with a round table discussion on four topics chosen based on relevance to the materials presented at podium; (1) What does the medical devices industry expect from spine biomechanists? Appropriateness of testing criteria and their dependence on the patient age, condition and lifestyle were discussed as related to the evaluation of relative
Editorial / Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
safety and effectiveness of products. (2) How accurately should we replicate in vivo physiological conditions in vitro? Issues on suitability of animal models, intact normal specimen versus degenerate and injured ones, preconditioning and specific objective of in vitro tests were debated. (3) What is the role of the disc annulus interlaminar interface in disc function and failure? The crucial effects of ageing, disc-endplate interface, fluid content and nucleus pressurization were discussed. (4) How to make full subjectspecific trunk musculoskeletal models? Different aspects, from kinematics to material/structural properties and geometry besides the potential of various established and emerging technologies in providing the datasets needed both as input and for validation were discussed.
Photos of some participants during the workshop.
3. Special issue content The issue begins with two review papers. The first one focuses on what has been learnt regarding the fundamentals of spinal biomechanics in the past 25 years and challenges that lie ahead in future (Oxland, 2016). The second one reviews earlier attempts to estimate spinal loads with focus on measurements of the intradiscal pressure
and loads on vertebral replacements. Various musculoskeletal models are also presented and discussed in details with attention on their assumptions and validation (Dreischarf et al., 2016b). The fluid content, inflow, outflow and pressure distribution are crucial parameters that govern the time-dependent response of intervertebral discs in loading and unloading periods and as such should be accurately represented in vitro if in vivo physiological conditions are to be replicated (Schmidt et al., 2016; Vergroesen et al., 2016). Concerns on the accuracy of intradiscal pressure measurements using sensors with different sizes are examined in vitro in two species (Bashkuev et al., 2016). The beneficial effect of vertebroplasty in restoring geometry and reducing creep in fractured vertebrae is demonstrated in vitro (Luo et al., 2016).
Compression fatigue fracture strength of 41 lumbar functional spinal units is found in vitro to be related primarily to the endplate area and bone mineral density (Huber et al., 2016). Lifting from the floor while anchoring one hand on the thigh is recommended as a technique to reduce loads on the back (Kingma et al., 2016). Using an instrumented vertebral replacement system in 4 patients, the effect of lifting techniques on the measured loads on implants is investigated (Dreischarf et al., 2016a). Inertial sensor and force plate measurements are used in 60 subjects to explore the likely effects of age on kinematics and moment demands during lowering and lifting a 4.5 kg weight (Shojaei
Editorial / Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
et al., 2016). The suitability of an inertial motion capture system to estimate L5/S1 moments and ground reaction forces is demonstrated in dynamic and asymmetric tasks (Faber et al., 2016). A measurement device using strain gauges and inertial sensors is used in 309 subjects to record lumbopelvic rhythm in flexion as a function of age and gender (Pries et al., 2016). Range of motion of the thoracic spine in forward flexion is measured and compared to that of the lumbar spine in 40 young subjects using inertial sensors (Hajibozorgi and Arjmand, 2016). Magnetic resonance imaging is utilized to construct 9 subject-specific geometries and investigate spine biomechanics while driven by recorded movements from supine to standing and sitting positions (Zanjani-Pour et al., 2016). The effect of age and pre-perturbation effort on the trunk stiffness in upright standing is investigated under sudden perturbation displacements (Vazirian et al., 2016). Increases in the trunk kinematics and electromyography activities are recorded in 10 subjects during perturbed compared to unperturbed gait at 1 m/s walking speed on a split-belt treadmill (Muller et al., 2016). Recorded kinematics of subjects seated on a wobble chair are used to drive musculoskeletal models of 6 normal and 6 low back pain individuals to estimate transient muscle forces and spinal loads (Shahvarpour et al., 2016). Musculoskeletal models of the trunk are introduced (1) to estimate muscle forces, lumbar loads and trunk stability as the hand-held pulling load elevation, magnitude and orientation alter (El Ouaaid et al., 2016), (2) to evaluate the effect of changes in lumbar spine vertebra and disc dimensions on predicted spinal loads (Putzer et al., 2016) and (3) to study the influence of the consideration of the thoracic rib cage on spinal loads (Ignasiak et al., 2016). With the objective to reduce existing complexity in estimating muscle exertions, the muscle synergies in a multimuscle model under various tasks and cost functions are investigated (Eskandari et al., 2016). Finally, the load sharing among passive lumbar spine components under combined sagittal loads are presented and discussed using finite element model studies (Naserkhaki et al., 2016). In summary, this special issue is a demonstration of recent progress in the spine biomechanics made possible using state of the art, existing and novel, measurement and computational techniques. This workshop highlights that tangible progress is possible only by effective exchange and collaboration between researchers working in various disciplines related to the spinal function, dysfunction and care. It has increasingly become evident that the key to further success in providing the most effective care for patients suffering from spinal disorders lies in intensified cross communications and collaborations between all those working in imaging, health care, epidemiology, biomedical industry and experimental and computational environments; in other words as elegantly phrased by late Alf Nachemson, by inter specialty migrations. Prevention, performance enhancement and rehabilitation programs stand also to substantially benefit.
Acknowledgments The organization of the current workshop was not possible without extraordinary efforts and dedication by Dr. F. Graichen as coordinator and B. Schiller as secretary of the workshop. With considerable attention to details, they provided a perfect, flawless and pleasant environment throughout from the initial announcement and invitation to the preparation of program and abstract book to the final moments of the meeting as well as during the scientific sessions to the social events. We are also grateful to the Editorial Office of the Journal of Biomechanics for the opportunity
3
and assistance to publish all the papers within this special issue. Finally, the generous financial contributions of our sponsors (Epionics SPINE, CeramTec, Silony Medical, B Braun, German Research Foundation (SCHM 2572/3-1) and Deutsche ArthroseHilfe e.V.) are acknowledged.
References Bashkuev, M., Vergroesen, P.P.A., Dreischarf, M., Schilling, C., van der Veen, A.J., Schmidt, H., Kingma, I., 2016. Intradiscal pressure measurements: a challenge or a routine? J. Biomech. Belytschko, T., Kulak, R.F., Schultz, A.B., Galante, J.O., 1974. Finite element stress analysis of an intervertebral disc. J. Biomech. 7, 277–285. Davis, P.R., 1959. Posture of the trunk during the lifting of weights. Br. Med. J. 1, 87–89. Dreischarf, M., Rohlmann, A., Graichen, F., Bergmann, G., Schmidt, H., 2016a. In vivo loads on a vertebral body replacement during different lifting techniques. J. Biomech. Dreischarf, M., Shirazi-Adl, A., Arjmand, N., Rohlmann, A., Schmidt, H., 2016b. Estimation of loads on human lumbar spine: a review of in vivo and computational model studies. J. Biomech. Eklund, J.A., Corlett, E.N., 1984. Shrinkage as a measure of the effect of load on the spine. Spine 9, 189–194. El Ouaaid, Z., Shirazi-Adl, A., Plamondon, A., 2016. Effects of variation in external pulling force magnitude, elevation, and orientation on trunk muscle forces, spinal loads and stability. J. Biomech. Eskandari, A.H., Sedaghat-Nejad, E., Rashedi, E., Sedighi, A., Arjmand, N., Parnianpour, M., 2016. The effect of parameters of equilibrium-based 3-D biomechanical models on extracted muscle synergies during isometric lumbar exertion. J. Biomech. Faber, G.S., Chang, C.C., Kingma, I., Dennerlein, J.T., van Dieen, J.H., 2016. Estimating 3D L5/S1 moments and ground reaction forces during trunk bending using a full-body ambulatory inertial motion capture system. J. Biomech. Hajibozorgi, M., Arjmand, N., 2016. Sagittal range of motion of the thoracic spine using inertial tracking device and effect of measurement errors on model predictions. J. Biomech. Hirsch, C., Nachemson, A., 1954. New observations on mechanical behaviour of lumbar discs. Acta Orthop. Scand. 22, 254–283. Huber, G., Nagel, K., Skrzypiec, D.M., Klein, A., Puschel, L., Morlock, M.M., 2016. A description of spinal fatigue strength. J. Biomech. Ignasiak, D., Dendorfer, S., Ferguson, S.J., 2016. Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading. J. Biomech. Kingma, I., Faber, G.S., van Dieen, J.H., 2016. Supporting the upper body with the hand on the thigh reduces back loading during lifting. J. Biomech. Luo, J., Pollintine, P., Annesley-Williams, D.J., Dolan, P., Adams, M.A., 2016. Vertebroplasty reduces progressive “creep” deformity of fractured vertebrae. J. Biomech. McGill, S.M., Norman, R.W., 1986. Partitioning of the L4–L5 dynamic moment into disc, ligamentous, and muscular components during lifting. Spine 11, 666–678. Muller, J., Muller, S., Engel, T., Reschke, A., Baur, H., Mayer, F., 2016. Stumbling reactions during perturbed walking: Neuromuscular activity and 3-D kinematics of the trunk—a pilot study. J. Biomech. Nachemson, A., Morris, J.M., 1964. In vivo measurements of intradiscal pressure. J. Bone Jt. Surg. 64A, 1077–1092. Naserkhaki, S., Jaremko, J.L., Adeeb, S., El-Rich, M., 2016. On the load-sharing along the ligamentous lumbosacral spine: finite element modeling and static equilibrium approach. J. Biomech. NIOSH, 1997. Bernard, B.P. (Ed.), Musculoskeletal Disorders and Workplace Factors. US Department of Health and Human Services, Cincinnati, OH. Oxland, T.R., 2016. Fundamental biomechanics of the spine—what we have learned in the past 25 years and future directions. J. Biomech. Pries, E., Dreischarf, M., Bashkuev, M., Putzier, M., Schmidt, H., 2016. The effects of age and gender on the lumbopelvic rhythm in the sagittal plane in 309 subjects. J. Biomech. 48, 3080–3087. Putzer, M., Ehrlich, I., Rasmussen, J., Gebbeken, N., Dendorfer, S., 2016. Sensitivity of lumbar spine loading to anatomical parameters. J. Biomech. Roaf, R., 1960. A study of the mechanics of spinal injuries. J. Bone Jt. Surg. 42B, 810–823. Rohlmann, A., Bergmann, G., Graichen, F., 1999. Loads on internal spinal fixators measured in different body positions. Eur. Spine J. 8, 354–359. Schmidt, H., Galbusera, F., Rohlmann, A., Shirazi-Adl, A., 2013. What have we learned from finite element studies of lumbar intervertebral discs in the past four decades? J. Biomech. 46, 2342–2355. Schmidt, H., Schilling, C., Puente Reyna, A.L., Shirazi-Adl, A., Dreischarf, M., 2016. Fluid-flow dependent response of intervertebral discs under cyclic loading: on the role of specimen preparation and preconditioning. J. Biomech. Shahvarpour, A., Shirazi-Adl, A., Lariviere, C., 2016. Active-passive biodynamics of the human trunk when seated on a wobble chair. J. Biomech. Shojaei, I., Vazirian, M., Croft, E., Nussbaum, M.A., Bazrgari, B., 2016. Age related differences in mechanical demands imposed on the lower back by manual material handling tasks. J. Biomech.
4
Editorial / Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Vazirian, M., Shojaei, I., Tromp, R.L., Nussbaum, M.A., Bazrgari, B., 2016. Age and gender differences in trunk intrinsic stiffness. J. Biomech. Vergroesen, P.P.A., van der Veen, A.J., Emanuel, K.S., van Dieen, J.H., Smit, T.H., 2016. The poro-elastic behaviour of the intervertebral disc: a new perspective on diurnal fluid flow. J. Biomech. Zanjani-Pour, S., Winlove, C.P., Smith, C.W., Meakin, J.R., 2016. Image driven subjectspecific finite element models of spinal biomechanics. J. Biomech.
Aboulfazl Shirazi-Adl n Division of Applied Mechanics, Department of Mechanical Engineering, École Polytechnique, Montréal, Canada E-mail address: [email protected]
n Correspondence to: Department of Mechanical Engineering, École Polytechnique, P.O. Box 6079, Station “centre-ville”, Montréal, Québec, Canada H3C 3A7. Fax: þ1 514 340 4176.
Hendrik Schmidt Julius Wolff Institute Charité – Universitätsmedizin Berlin, Berlin, Germany Idsart Kingma Research Institute MOVE, Department of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands 8 February 2016
Contents lists available at ScienceDirect
Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com
Editorial
Spine loading and deformation – From loading to recovery art ic l e i nf o Keywords: Spine Loads Deformation Intervertebral disc Biomechanics
1. Introduction There is ample evidence in the literature of a strong association between low back disorders and spine loading and deformation that are present particularly during repetitive heavy lifting and awkward postures (NIOSH, 1997). The human spine has the fundamental function of the support, control and transmission of upper trunk loads (i.e., body weight, loads carried in hands and on shoulders, inertial loads) while performing tasks and movements common in daily recreational, sport and workplace activities. Peak and repetitive loads and deformations at levels approaching tissue injury thresholds, jerky movements and sudden unforeseen perturbations regularly put this function (i.e., the resistant, reflex response, control and system stability) to the test. Acute or accumulated tissue injuries, degenerations, contaminations in neural network, deformities and instability likely increase the risk of further deteriorations and pain. Adequate knowledge of spine loading and deformation in various conditions and mechanical environments remains hence crucial for effective risk evaluation, workplace safety, prevention programs, rehabilitation, tissue regeneration, tissue replacement and surgery of the human spine. From early attempts on measurement of the intradiscal pressure (e.g., Nachemson and Morris, 1964), spinal shrinkage (e.g., Eklund and Corlett, 1984), intra-abdominal pressure (e.g., Davis, 1959), muscle electromyography activity (e.g., McGill and Norman, 1986) to more recent ones using instrumented vertebral implants (Rohlmann et al., 1999), researchers have aimed to estimate mechanical loading on the human spine in various activities. In parallel, in vitro studies have for long (e.g., Hirsch and Nachemson, 1954; Roaf, 1960) shed light on the passive resistance and failure mechanisms of the spinal components and tissues. While the foregoing measurements have substantially improved our understanding of the functional biomechanics of the spine in normal and injured conditions, it has long been recognized that they alone are not sufficient to quantify the complex mechanisms in action prior, during and subsequent to injuries. Computational models have hence been employed (e.g., Belytschko et al., 1974) with the http://dx.doi.org/10.1016/j.jbiomech.2016.02.024 0021-9290/& 2016 Elsevier Ltd. All rights reserved.
expectation to accurately determine the spatial and temporal variations of stresses, strains, fluid flow, cell viability and solute transport throughout the spinal tissues (see review paper; Schmidt et al., 2013). It has never been as evident that further meaningful progress in this field can only materialize through complementary investigations taking full consideration of all these tools.
2. Berlin workshop After about a year of its inception, the current workshop on spine loading and deformation, organized by Hendrik Schmidt and Aboulfazl Shirazi-Adl, took place with 75 participants from 14 countries around the globe at Julius Wolff Institute of Charité– Universitätsmedizin in Berlin during 3 days of July 2–4, 2015; http://workshop.spine-biomechanics.com/. The workshop aimed to gather researchers working in different disciplines and fields of application in health care, biological science, biomechanics and ergonomics together in order to share, discuss and re-examine the potentials of their recent works on the spine. Research topics covered trunk loads and motion measurements (imaging, sensors and video camera) and predictions during static and dynamic tasks with focus on the lumbar and thoracic spines. More than 50 renowned experts in the field were initially contacted. Submitted abstracts were evaluated and authors of accepted ones were invited to present their work at the meeting and submit an original paper for consideration in this special issue of the Journal of Biomechanics. In total 33 works were presented and 22 research papers finally accepted after peer review for inclusion in the current issue. The meeting ended with a round table discussion on four topics chosen based on relevance to the materials presented at podium; (1) What does the medical devices industry expect from spine biomechanists? Appropriateness of testing criteria and their dependence on the patient age, condition and lifestyle were discussed as related to the evaluation of relative
Editorial / Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
safety and effectiveness of products. (2) How accurately should we replicate in vivo physiological conditions in vitro? Issues on suitability of animal models, intact normal specimen versus degenerate and injured ones, preconditioning and specific objective of in vitro tests were debated. (3) What is the role of the disc annulus interlaminar interface in disc function and failure? The crucial effects of ageing, disc-endplate interface, fluid content and nucleus pressurization were discussed. (4) How to make full subjectspecific trunk musculoskeletal models? Different aspects, from kinematics to material/structural properties and geometry besides the potential of various established and emerging technologies in providing the datasets needed both as input and for validation were discussed.
Photos of some participants during the workshop.
3. Special issue content The issue begins with two review papers. The first one focuses on what has been learnt regarding the fundamentals of spinal biomechanics in the past 25 years and challenges that lie ahead in future (Oxland, 2016). The second one reviews earlier attempts to estimate spinal loads with focus on measurements of the intradiscal pressure
and loads on vertebral replacements. Various musculoskeletal models are also presented and discussed in details with attention on their assumptions and validation (Dreischarf et al., 2016b). The fluid content, inflow, outflow and pressure distribution are crucial parameters that govern the time-dependent response of intervertebral discs in loading and unloading periods and as such should be accurately represented in vitro if in vivo physiological conditions are to be replicated (Schmidt et al., 2016; Vergroesen et al., 2016). Concerns on the accuracy of intradiscal pressure measurements using sensors with different sizes are examined in vitro in two species (Bashkuev et al., 2016). The beneficial effect of vertebroplasty in restoring geometry and reducing creep in fractured vertebrae is demonstrated in vitro (Luo et al., 2016).
Compression fatigue fracture strength of 41 lumbar functional spinal units is found in vitro to be related primarily to the endplate area and bone mineral density (Huber et al., 2016). Lifting from the floor while anchoring one hand on the thigh is recommended as a technique to reduce loads on the back (Kingma et al., 2016). Using an instrumented vertebral replacement system in 4 patients, the effect of lifting techniques on the measured loads on implants is investigated (Dreischarf et al., 2016a). Inertial sensor and force plate measurements are used in 60 subjects to explore the likely effects of age on kinematics and moment demands during lowering and lifting a 4.5 kg weight (Shojaei
Editorial / Journal of Biomechanics ∎ (∎∎∎∎) ∎∎∎–∎∎∎
et al., 2016). The suitability of an inertial motion capture system to estimate L5/S1 moments and ground reaction forces is demonstrated in dynamic and asymmetric tasks (Faber et al., 2016). A measurement device using strain gauges and inertial sensors is used in 309 subjects to record lumbopelvic rhythm in flexion as a function of age and gender (Pries et al., 2016). Range of motion of the thoracic spine in forward flexion is measured and compared to that of the lumbar spine in 40 young subjects using inertial sensors (Hajibozorgi and Arjmand, 2016). Magnetic resonance imaging is utilized to construct 9 subject-specific geometries and investigate spine biomechanics while driven by recorded movements from supine to standing and sitting positions (Zanjani-Pour et al., 2016). The effect of age and pre-perturbation effort on the trunk stiffness in upright standing is investigated under sudden perturbation displacements (Vazirian et al., 2016). Increases in the trunk kinematics and electromyography activities are recorded in 10 subjects during perturbed compared to unperturbed gait at 1 m/s walking speed on a split-belt treadmill (Muller et al., 2016). Recorded kinematics of subjects seated on a wobble chair are used to drive musculoskeletal models of 6 normal and 6 low back pain individuals to estimate transient muscle forces and spinal loads (Shahvarpour et al., 2016). Musculoskeletal models of the trunk are introduced (1) to estimate muscle forces, lumbar loads and trunk stability as the hand-held pulling load elevation, magnitude and orientation alter (El Ouaaid et al., 2016), (2) to evaluate the effect of changes in lumbar spine vertebra and disc dimensions on predicted spinal loads (Putzer et al., 2016) and (3) to study the influence of the consideration of the thoracic rib cage on spinal loads (Ignasiak et al., 2016). With the objective to reduce existing complexity in estimating muscle exertions, the muscle synergies in a multimuscle model under various tasks and cost functions are investigated (Eskandari et al., 2016). Finally, the load sharing among passive lumbar spine components under combined sagittal loads are presented and discussed using finite element model studies (Naserkhaki et al., 2016). In summary, this special issue is a demonstration of recent progress in the spine biomechanics made possible using state of the art, existing and novel, measurement and computational techniques. This workshop highlights that tangible progress is possible only by effective exchange and collaboration between researchers working in various disciplines related to the spinal function, dysfunction and care. It has increasingly become evident that the key to further success in providing the most effective care for patients suffering from spinal disorders lies in intensified cross communications and collaborations between all those working in imaging, health care, epidemiology, biomedical industry and experimental and computational environments; in other words as elegantly phrased by late Alf Nachemson, by inter specialty migrations. Prevention, performance enhancement and rehabilitation programs stand also to substantially benefit.
Acknowledgments The organization of the current workshop was not possible without extraordinary efforts and dedication by Dr. F. Graichen as coordinator and B. Schiller as secretary of the workshop. With considerable attention to details, they provided a perfect, flawless and pleasant environment throughout from the initial announcement and invitation to the preparation of program and abstract book to the final moments of the meeting as well as during the scientific sessions to the social events. We are also grateful to the Editorial Office of the Journal of Biomechanics for the opportunity
3
and assistance to publish all the papers within this special issue. Finally, the generous financial contributions of our sponsors (Epionics SPINE, CeramTec, Silony Medical, B Braun, German Research Foundation (SCHM 2572/3-1) and Deutsche ArthroseHilfe e.V.) are acknowledged.
References Bashkuev, M., Vergroesen, P.P.A., Dreischarf, M., Schilling, C., van der Veen, A.J., Schmidt, H., Kingma, I., 2016. Intradiscal pressure measurements: a challenge or a routine? J. Biomech. Belytschko, T., Kulak, R.F., Schultz, A.B., Galante, J.O., 1974. Finite element stress analysis of an intervertebral disc. J. Biomech. 7, 277–285. Davis, P.R., 1959. Posture of the trunk during the lifting of weights. Br. Med. J. 1, 87–89. Dreischarf, M., Rohlmann, A., Graichen, F., Bergmann, G., Schmidt, H., 2016a. In vivo loads on a vertebral body replacement during different lifting techniques. J. Biomech. Dreischarf, M., Shirazi-Adl, A., Arjmand, N., Rohlmann, A., Schmidt, H., 2016b. Estimation of loads on human lumbar spine: a review of in vivo and computational model studies. J. Biomech. Eklund, J.A., Corlett, E.N., 1984. Shrinkage as a measure of the effect of load on the spine. Spine 9, 189–194. El Ouaaid, Z., Shirazi-Adl, A., Plamondon, A., 2016. Effects of variation in external pulling force magnitude, elevation, and orientation on trunk muscle forces, spinal loads and stability. J. Biomech. Eskandari, A.H., Sedaghat-Nejad, E., Rashedi, E., Sedighi, A., Arjmand, N., Parnianpour, M., 2016. The effect of parameters of equilibrium-based 3-D biomechanical models on extracted muscle synergies during isometric lumbar exertion. J. Biomech. Faber, G.S., Chang, C.C., Kingma, I., Dennerlein, J.T., van Dieen, J.H., 2016. Estimating 3D L5/S1 moments and ground reaction forces during trunk bending using a full-body ambulatory inertial motion capture system. J. Biomech. Hajibozorgi, M., Arjmand, N., 2016. Sagittal range of motion of the thoracic spine using inertial tracking device and effect of measurement errors on model predictions. J. Biomech. Hirsch, C., Nachemson, A., 1954. New observations on mechanical behaviour of lumbar discs. Acta Orthop. Scand. 22, 254–283. Huber, G., Nagel, K., Skrzypiec, D.M., Klein, A., Puschel, L., Morlock, M.M., 2016. A description of spinal fatigue strength. J. Biomech. Ignasiak, D., Dendorfer, S., Ferguson, S.J., 2016. Thoracolumbar spine model with articulated ribcage for the prediction of dynamic spinal loading. J. Biomech. Kingma, I., Faber, G.S., van Dieen, J.H., 2016. Supporting the upper body with the hand on the thigh reduces back loading during lifting. J. Biomech. Luo, J., Pollintine, P., Annesley-Williams, D.J., Dolan, P., Adams, M.A., 2016. Vertebroplasty reduces progressive “creep” deformity of fractured vertebrae. J. Biomech. McGill, S.M., Norman, R.W., 1986. Partitioning of the L4–L5 dynamic moment into disc, ligamentous, and muscular components during lifting. Spine 11, 666–678. Muller, J., Muller, S., Engel, T., Reschke, A., Baur, H., Mayer, F., 2016. Stumbling reactions during perturbed walking: Neuromuscular activity and 3-D kinematics of the trunk—a pilot study. J. Biomech. Nachemson, A., Morris, J.M., 1964. In vivo measurements of intradiscal pressure. J. Bone Jt. Surg. 64A, 1077–1092. Naserkhaki, S., Jaremko, J.L., Adeeb, S., El-Rich, M., 2016. On the load-sharing along the ligamentous lumbosacral spine: finite element modeling and static equilibrium approach. J. Biomech. NIOSH, 1997. Bernard, B.P. (Ed.), Musculoskeletal Disorders and Workplace Factors. US Department of Health and Human Services, Cincinnati, OH. Oxland, T.R., 2016. Fundamental biomechanics of the spine—what we have learned in the past 25 years and future directions. J. Biomech. Pries, E., Dreischarf, M., Bashkuev, M., Putzier, M., Schmidt, H., 2016. The effects of age and gender on the lumbopelvic rhythm in the sagittal plane in 309 subjects. J. Biomech. 48, 3080–3087. Putzer, M., Ehrlich, I., Rasmussen, J., Gebbeken, N., Dendorfer, S., 2016. Sensitivity of lumbar spine loading to anatomical parameters. J. Biomech. Roaf, R., 1960. A study of the mechanics of spinal injuries. J. Bone Jt. Surg. 42B, 810–823. Rohlmann, A., Bergmann, G., Graichen, F., 1999. Loads on internal spinal fixators measured in different body positions. Eur. Spine J. 8, 354–359. Schmidt, H., Galbusera, F., Rohlmann, A., Shirazi-Adl, A., 2013. What have we learned from finite element studies of lumbar intervertebral discs in the past four decades? J. Biomech. 46, 2342–2355. Schmidt, H., Schilling, C., Puente Reyna, A.L., Shirazi-Adl, A., Dreischarf, M., 2016. Fluid-flow dependent response of intervertebral discs under cyclic loading: on the role of specimen preparation and preconditioning. J. Biomech. Shahvarpour, A., Shirazi-Adl, A., Lariviere, C., 2016. Active-passive biodynamics of the human trunk when seated on a wobble chair. J. Biomech. Shojaei, I., Vazirian, M., Croft, E., Nussbaum, M.A., Bazrgari, B., 2016. Age related differences in mechanical demands imposed on the lower back by manual material handling tasks. J. Biomech.
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Vazirian, M., Shojaei, I., Tromp, R.L., Nussbaum, M.A., Bazrgari, B., 2016. Age and gender differences in trunk intrinsic stiffness. J. Biomech. Vergroesen, P.P.A., van der Veen, A.J., Emanuel, K.S., van Dieen, J.H., Smit, T.H., 2016. The poro-elastic behaviour of the intervertebral disc: a new perspective on diurnal fluid flow. J. Biomech. Zanjani-Pour, S., Winlove, C.P., Smith, C.W., Meakin, J.R., 2016. Image driven subjectspecific finite element models of spinal biomechanics. J. Biomech.
Aboulfazl Shirazi-Adl n Division of Applied Mechanics, Department of Mechanical Engineering, École Polytechnique, Montréal, Canada E-mail address: [email protected]
n Correspondence to: Department of Mechanical Engineering, École Polytechnique, P.O. Box 6079, Station “centre-ville”, Montréal, Québec, Canada H3C 3A7. Fax: þ1 514 340 4176.
Hendrik Schmidt Julius Wolff Institute Charité – Universitätsmedizin Berlin, Berlin, Germany Idsart Kingma Research Institute MOVE, Department of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands 8 February 2016