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Spinal biomechanics

Marina Obradov, Menno R Bénard, Michiel M A Janssen, Patricia G Anderson, Petra J C Heesterbeek, Maarten Spruit
Study Design A prospective cohort study. Objective Decompression and fusion of cervical vertebrae is a combined procedure that has a high success rate in relieving radicular symptoms and stabilizing or improving cervical myelopathy. However, fusion may lead to increased motion of the adjacent vertebrae and cervical deformity. Both have been postulated to lead to adjacent segment pathology (ASP). Kinematic magnetic resonance imaging (MRI) has been increasingly used to evaluate range of motion (ROM) of the cervical spine and ASP...
November 2016: Global Spine Journal
Adnan Bashir Bhatti, Sunny Kim
A 79-year-old female presented with incapacitating chronic neck pain. The patient's pain which was greatest on the left side persisted for 18 months and was described as stabbing in nature (10/10 intensity). In addition to her neck pain, the patient described having frequent headaches. After six weeks of physical therapy and undergoing a rhizotomy procedure, she showed no prolonged improvement. An epidural steroid injection provided only temporary pain relief and was followed by a successful posterior fusion using the Harms technique with iliac crest autogenous bone grafting and placement of polyaxial screws in the C1 lateral masses and C2 pedicles...
September 21, 2016: Curēus
Thomas Beez, Jennifer Brown
BACKGROUND: Atlanto-occipital dislocation (AOD) is a rare but severe sequela of high energy trauma. Children are at increased risk, due to their immature spine and biomechanical characteristics. LITERATURE REVIEW: The prevailing mechanism of injury is motor vehicle collision as passenger. AOD commonly presents with cardiorespiratory arrest, spinal cord injury or cranial nerve deficits. Concomitant injuries, such as traumatic brain injury, are frequently encountered...
October 18, 2016: Child's Nervous System: ChNS: Official Journal of the International Society for Pediatric Neurosurgery
Ruozhou Zhou, Zhiping Huang, Xiang Liu, Jie Tong, Wei Ji, Sheting Liu, Qingan Zhu
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)...
October 5, 2016: Clinical Biomechanics
Leo Fradet, Xiaoyu Wang, Lawrence G Lenke, Carl-Eric Aubin
BACKGROUND: Proximal junctional failure is a severe proximal junctional complication following adult spinal instrumentation and involving acute proximal junctional kyphotic deformity, mechanical failure at the upper instrumented vertebra or just above, and/or proximal junctional osseoligamentous disruption. Clinical studies have identified potential risk factors, but knowledge on their biomechanics is still lacking for addressing the proximal junctional failure issues. The objective of this study was to develop comprehensive computational modeling and simulation techniques to investigate proximal junctional failure...
October 11, 2016: Clinical Biomechanics
A Ireland, R F Capozza, G R Cointry, L Nocciolino, J L Ferretti, J Rittweger
: Fibula response to disuse is unknown; we assessed fibula bone in spinal cord injury (SCI) patients and able-bodied counterparts. Group differences were smaller than in the neighbouring tibia which could not be explained by bone geometry. Differential adaptation of the shank bones may indicate previously unknown mechanoadaptive behaviours of bone. INTRODUCTION: The fibula supports only a small and highly variable proportion of shank compressive load (-8 to +19 %), and little is known about other kinds of stresses...
October 12, 2016: Osteoporosis International
Rafael Ekmejian, Pooria Sarrami, Justine M Naylor, Ian A Harris
BACKGROUND: Motorcyclists are a vulnerable road-user population who are overrepresented in traffic injuries. Utilisation of back protectors may be an effective preventive measure for spine injuries in motorcyclists. Since use of back protectors is increasing it is important that clinical evidence supports their use. The study aimed to investigate the current evidence on the ability of back protectors to reduce the rate of back injuries and patient mortality in motorcycle crashes. METHODS: A systematic literature search was conducted using various electronic databases...
October 4, 2016: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine
Sriram Balasubramanian, James R Peters, Lucy F Robinson, Anita Singh, Richard W Kent
PURPOSE: Based on the structural anatomy, loading condition and range of motion (ROM), no quadruped animal has been shown to accurately mimic the structure and biomechanical function of the human spine. The objective of this study is to quantify the thoracic vertebrae geometry of the kangaroo, and compare with adult human, pig, sheep, and deer. METHODS: The thoracic vertebrae (T1-T12) from whole body CT scans of ten juvenile kangaroos (ages 11-14 months) were digitally reconstructed and geometric dimensions of the vertebral bodies, endplates, pedicles, spinal canal, processes, facets and intervertebral discs were recorded...
October 4, 2016: European Spine Journal
Fon-Yih Tsuang, Chia-Hsien Chen, Lien-Chen Wu, Yi-Jie Kuo, Shang-Chih Lin, Chang-Jung Chiang
BACKGROUND: Failure of pedicle screw is a major concern in spinal surgery. The threaded and unthreaded portions of the pedicle screw provide the ability to anchor and squeeze the surrounding bone, respectively. This study aimed to investigate the anchoring and squeezing effects of different design of the threaded/unthreaded portions of a pedicle screw to vertebrae. METHODS: Four variations (one fully and three partially threaded, with a 1/3, 1/2, and 2/3 unthreaded designs at the proximal portion) of screws were used to measure pullout strength and withdrawn energy using synthetic and porcine specimens...
September 23, 2016: Clinical Biomechanics
Brian D Stemper, Brian D Corner
Synopsis Despite considerable research effort, the incidence of whiplash injury during automotive collisions has continued to rise. This is due, at least in part, to a limited recognition of biomechanical injury mechanisms and factors influencing injury risk. While automotive safety modifications reduced injury risk in some cases, impact on the overall whiplash incidence was limited. This is likely attributable to significant occupant-related differences that have a profound impact on injury risk. Many of those differences were outlined in research studies, and examples include female sex and the associated sex-based anthropometrical variation that can affect seating orientation; cervical spinal posture; and anatomical attributes, including cervical column slenderness and neck muscle morphometry...
October 2016: Journal of Orthopaedic and Sports Physical Therapy
Veronica Cimolin, Nicola Cau, Elena Tacchini, Manuela Galli, Chiara Rigoldi, Marco Rinolfi, Valentina Aspesi, Edda M Capodaglio, Paolo Capodaglio
BACKGROUND: Nurses are exposed to the risk of injury while handling patients. This is particularly true for obese patients. OBJECTIVE: The goal of this paper is to estimate the spinal loads and the related risk of injury to nurses while lifting obese patients from the floor with a bariatric sheet during a hospital emergency. METHODS: Six male nurses participated in this study. The biomechanical analysis focused on the lifting strategy. Thirty obese in-patients were enrolled to take part in the experimental study and divided into three groups according to their Body Mass Index (BMI)...
2016: La Medicina del Lavoro
Emmanuelle Chaleat-Valayer, Agnès Troncy, Marion Montané, Soline Bellaiche, Eric Berthonnaud
OBJECTIVE: The goal of this preliminary study is to analyze the biomechanical strategies of spine, pelvis and lower limbs (LL) with tridimensional motion analysis during stand-to-sit task, an understudied movement in the literature, however, source of questioning in clinical practice. OBSERVATIONS: One female and one male, healthy participants, (respectively 28 and 48 years old) were included without history of pathology and with normal pelvic incidences. Participants performed stand-to-sit movements on a stool without using their hands...
September 2016: Annals of Physical and Rehabilitation Medicine
M M van Rijsbergen, V M P Barthelemy, A C T Vrancken, S P M Crijns, H-J Wilke, W Wilson, B van Rietbergen, K Ito
The two main load bearing tissues of the intervertebral disc are the nucleus pulposus and the annulus fibrosus. Both tissues are composed of the same basic components, but differ in their organization and relative amounts. With degeneration, the clear distinction between the two tissues disappears. The changes in biochemical content lead to changes in mechanical behaviour of the intervertebral disc. The aim of the current study was to investigate if well-documented moderate degeneration at the biochemical and fibre structure level leads to instability of the lumbar spine...
September 23, 2016: Biomechanics and Modeling in Mechanobiology
Nihat Acar, Ahmet Karakasli, Ahmet A Karaarslan, Mehmet Hilal Ozcanhan, Fatih Ertem, Mehmet Erduran
OBJECTIVE: Rod-screw fixation systems are widely used for spinal instrumentation. Although many biomechanical studies on rod-screw systems have been carried out, but the effects of rod contouring on the construct strength is still not very well defined in the literature. This work examines the mechanical impact of straight, 20° kyphotic, and 20° lordotic rod contouring on rod-screw fixation systems, by forming a corpectomy model. METHODS: The corpectomy groups were prepared using ultra-high molecular weight polyethylene samples...
September 2016: Journal of Korean Neurosurgical Society
Daniel G Tobert, Valentin Antoci, Shaun P Patel, Ehsan Saadat, Christopher M Bono
Adjacent segment disease (ASD) is disappointing long-term outcome for both the patient and clinician. In contrast to adjacent segment degeneration, which is a common radiographic finding, ASD is less common. The incidence of ASD in both the cervical and lumbar spine is between 2% and 4% per year, and ASD is a significant contributor to reoperation rates after spinal arthrodesis. The etiology of ASD is multifactorial, stemming from existing spondylosis at adjacent levels, predisposed risk to degenerative changes, and altered biomechanical forces near a previous fusion site...
September 16, 2016: Clinical Spine Surgery
Kingsley R Chin, Fabio J R Pencle, André V Coombs, Mohamed Elsharkawy, Corrine F Packer, Elijah A Hothem, Jason A Seale
STUDY DESIGN: Level III. OBJECTIVE: To report on the outcomes of midline cortical bone trajectory (CBT) pedicle screw surgical technique for posterior lumbar fixation in the outpatient surgery center (OSC) compared with traditional pedicle screws in the hospital. SUMMARY OF BACKGROUND DATA: Traditional pedicle screws have been the gold standard for posterior lumbar fusion. Advances in spine surgery, including less invasive procedures have propelled the design of instruments and implants to achieve greater posterior spinal fixation, with decreased tissue destruction and higher safety margins...
September 16, 2016: Clinical Spine Surgery
Franck Le Navéaux, A Noelle Larson, Hubert Labelle, Xiaoyu Wang, Carl-Éric Aubin
BACKGROUND: Optimal implant densities and configurations for thoracic spine instrumentation to treat adolescent idiopathic scoliosis remain unknown. The objective was to computationally assess the biomechanical effects of implant distribution on 3D curve correction and bone-implant forces. METHODS: 3D patient-specific biomechanical spine models based on a multibody dynamic approach were created for 9 Lenke 1 patients who underwent posterior instrumentation (main thoracic Cobb: 43°-70°)...
September 9, 2016: Clinical Biomechanics
Seonhong Hwang, Yen-Sheng Lin, Nathan S Hogaboom, Lin-Hwa Wang, Alicia M Koontz
Wheelchair propulsion is a major cause of upper limb pain and injuries for manual wheelchair users with spinal cord injuries (SCIs). Few studies have investigated wheelchair turning biomechanics on natural ground surfaces. The purpose of this study was to investigate the relationship between tangential push force and linear velocity of the wheelchair during the turning portions of propulsion. Using an instrumented handrim, velocity and push force data were recorded for 25 subjects while they propel their own wheelchairs on a concrete floor along a figure-eight-shaped course at a maximum velocity...
August 17, 2016: Biomedizinische Technik. Biomedical Engineering
Sukrit Jain, Adam E M Eltorai, Roy Ruttiman, Alan H Daniels
Since the late 1980s, spinal interbody cages (ICs) have been used to aid bone fusion in a variety of spinal disorders. Utilized to restore intervertebral height, enable bone graft containment for arthrodesis, and restore anterior column biomechanical stability, ICs have since evolved to become a highly successful means of achieving fusion, being associated with less postoperative pain, shorter hospital stay, fewer complications and higher rates of fusion when than bone graft only spinal fusion. IC design and materials have changed considerably over the past two decades...
August 2016: Orthopaedic Surgery
Mingzheng Zhang, Fang Pu, Liqiang Xu, Linlin Zhang, Hang Liang, Deyu Li, Yu Wang, Yubo Fan
Spinal cages are used to create a suitable mechanical environment for interbody fusion in cases of degenerative spinal instability. Due to individual variations in bone structures and pathological conditions, patient-specific cages can provide optimal biomechanical conditions for fusion, strengthening patient recovery. Finite element analysis (FEA) is a valuable tool in the biomechanical evaluation of patient-specific cage designs, but the time- and labor-intensive process of modeling limits its clinical application...
September 14, 2016: Computer Methods in Biomechanics and Biomedical Engineering
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