Kinematics of the Cervical Spine: Path of the Instant Axis of Rotation in Flexion and Extension

2000 ◽  
Author(s):  
Denis J. DiAngelo ◽  
Keith Vossel ◽  
Kevin T. Foley
Keyword(s):  
Cervical Spine ◽  
Vertebral Body ◽  
Measurement System ◽  
Axis Of Rotation ◽  
Rotational Components ◽  
Flexion Extension ◽  
Vertebral Kinematics ◽  
Set Up ◽  
Flexion And Extension

Abstract Previous Biomechanical Measures of Vertebral Kinematics. White and Panjabi (1990) have suggested that the Instant Axis of Rotation (IAR) be used to describe the 2-D motion of a vertebral body. However, the location of the IAR for the cervical spine varies amongst spine researchers. White and Panjabi (1990) have suggested the IAR of each vertebra is located in the anterior region of the subjacent vertebra; Porterfield and Derosa (1995) suggest it is located in the mid-region of the subjacent vertebra; and Mameren et al. (1992) found it to lay in the central region of the vertebral body being tracked. Goel and Winterbottom (1991) stated that during flexion and extension, the axis of rotation is located somewhere within the vertebral body itself. Unfortunately, no accurate calculations of the IAR paths of the cervical spine exist; typical vertebral measurements only include the rotational components. Estimation of the vertebrae’s IAR location in vitro depends on the experimental set-up (motion and loading mechanics), anatomical structure, mathematical reduction technique, and accuracy of the measurement equipment. Crisco et al. (1994) determined the theoretical error in calculating the location of the IAR as a function of the measurement system specifications and the placement of the markers on the spinal body. Conventional tracking systems having translational resolutions of 0.1mm to 0.05mm were found to calculate the location of the IAR to within 7mm to 10mm, respectively. This error became significantly larger as the resolution of the measurement system dropped off. Most investigators only calculate the rotational components of a body’s motion and seldom calculate the error involved in their mathematical analysis. Furthermore, overall head movement is often reported (i.e., C0 to T1), but smaller flexion-extension movements of individual spinal bodies are either void in the literature or suspect to large theoretical errors. The objective of the study was to determine the IAR of the sub-axial cervical vertebral bodies under physiological flexion and extension conditions in vitro.

Does Placement of the Axis of Rotation of the Cervical Spine Affect Motion Segment Mechanics During Flexion and Extension?

2009 ◽  
Author(s):  
Brian P. Kelly ◽  
Henry Bonin ◽  
Kyle Fraysur ◽  
Karen Sedacki ◽  
Denis J. DiAngelo
Keyword(s):  
Gold Standard ◽  
Dynamic State ◽  
Limited Data ◽  
Axis Of Rotation ◽  
Motion Segment ◽  
Rotational Components ◽  
Spinal Mechanics ◽  
Implanted Device ◽  
Flexion And Extension

Current in vitro testing methodologies remain limited in the ability to explore spinal mechanics. The gold standard of flexibility testing has traditionally focused only on evaluating rotational components of motion within a motion segment unit (MSU). While such data may be applied towards evaluation of the Center of Rotation (CoR) of a joint, many systems lack the needed sensitivity. The result is that there is currently no consensus on the location of the CoR of the spine. Further, very limited data or insight can be gathered as to the precise kinematic or dynamic state of the MSU, the influence of surgically implanted motion restoration devices, or the influence of subtle changes to an implanted device.

In vitro 3D-kinematics of the upper cervical spine: helical axis and simulation for axial rotation and flexion extension

2009 ◽  
Vol 32 (2) ◽  
pp. 141-151 ◽  
Author(s):  
Pierre-Michel Dugailly ◽  
Stéphane Sobczak ◽  
Victor Sholukha ◽  
Serge Van Sint Jan ◽  
Patrick Salvia ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Axial Rotation ◽  
Helical Axis ◽  
Upper Cervical Spine ◽  
3D Kinematics ◽  
Flexion Extension ◽  
Upper Cervical

scholarly journals Evaluation of RSA set-up from a clinical biplane fluoroscopy system for 3D joint kinematic analysis

Joints ◽  
2016 ◽  
Vol 04 (02) ◽  
pp. 121-125 ◽  
Author(s):  
Tommaso Bonanzinga ◽  
Cecilia Signorelli ◽  
Marco Bontempi ◽  
Alessandro Russo ◽  
Stefano Zaffagnini ◽  
...  
Keyword(s):  
Rigid Body ◽  
Kinematic Analysis ◽  
In Vitro Test ◽  
Flexion Extension ◽  
Vitro Test ◽  
Set Up ◽  
Static Conditions ◽  
Biplane Fluoroscopy

Purpose: dinamic roentgen stereophotogrammetric analysis (RSA), a technique currently based only on customized radiographic equipment, has been shown to be a very accurate method for detecting threedimensional (3D) joint motion. The aim of the present work was to evaluate the applicability of an innovative RSA set-up for in vivo knee kinematic analysis, using a biplane fluoroscopic image system. To this end, the Authors describe the set-up as well as a possible protocol for clinical knee joint evaluation. The accuracy of the kinematic measurements is assessed. Methods: the Authors evaluated the accuracy of 3D kinematic analysis of the knee in a new RSA set-up, based on a commercial biplane fluoroscopy system integrated into the clinical environment. The study was organized in three main phases: an in vitro test under static conditions, an in vitro test under dynamic conditions reproducing a flexion-extension range of motion (ROM), and an in vivo analysis of the flexionextension ROM. For each test, the following were calculated, as an indication of the tracking accuracy: mean, minimum, maximum values and standard deviation of the error of rigid body fitting. Results: in terms of rigid body fitting, in vivo test errors were found to be 0.10±0.05 mm. Phantom tests in static and kinematic conditions showed precision levels, for translations and rotations, of below 0.1 mm/0.2º and below 0.5 mm/0.3º respectively for all directions. Conclusions: the results of this study suggest that kinematic RSA can be successfully performed using a standard clinical biplane fluoroscopy system for the acquisition of slow movements of the lower limb. Clinical relevance: a kinematic RSA set-up using a clinical biplane fluoroscopy system is potentially applicable and provides a useful method for obtaining better characterization of joint biomechanics.

Analysis of adjacent-segment cervical kinematics: the role of construct length and the dorsal ligamentous complex

2020 ◽  
Vol 32 (1) ◽  
pp. 15-22
Author(s):  
Daniel Lubelski ◽  
Andrew T. Healy ◽  
Prasath Mageswaran ◽  
Robb Colbrunn ◽  
Richard P. Schlenk
Keyword(s):  
Cervical Spine ◽  
Industrial Robot ◽  
Adjacent Segment ◽  
Segmental Motion ◽  
Lateral Mass ◽  
Subaxial Cervical Spine ◽  
Flexion Extension ◽  
Cervical Kinematics

OBJECTIVELateral mass fixation stabilizes the cervical spine while causing minimal morbidity and resulting in high fusion rates. Still, with 2 years of follow-up, approximately 6% of patients who have undergone posterior cervical fusion have worsening kyphosis or symptomatic adjacent-segment disease. Based on the length of the construct, the question of whether to extend the fixation system to undisrupted levels has not been answered for the cervical spine. The authors conducted a study to quantify the role of construct length and the terminal dorsal ligamentous complex in the adjacent-segment kinematics of the subaxial cervical spine.METHODSIn vitro flexibility testing was performed using 6 human cadaveric specimens (C2–T8), with the upper thoracic rib cage and osseous and ligamentous integrity intact. An industrial robot was used to apply pure moments and to measure segmental motion at each level. The authors tested the intact state, followed by 9 postsurgical permutations of laminectomy and lateral mass fixation spanning C2 to C7.RESULTSConstructs spanning a single level exerted no significant effects on immediate adjacent-segment motion. The addition of a second immobilized segment, however, created significant changes in flexion-extension range of motion at the supradjacent level (+164%). Regardless of construct length, resection of the terminal dorsal ligaments did not greatly affect adjacent-level motion except at C2–3 and C7–T1 (increasing by +794% and +607%, respectively).CONCLUSIONSDorsal ligamentous support was found to contribute significant stability to the C2–3 and C7–T1 segments only. Construct length was found to play a significant role when fixating two or more segments. The addition of a fused segment to support an undisrupted cervical level is not suggested by the present data, except potentially at C2–3 and C7–T1. The study findings emphasize the importance of the C2–3 segment and its dorsal support.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation

2021 ◽  
pp. 1-9
Keyword(s):  
Interbody Fusion ◽  
Posterior Instrumentation ◽  
Axial Rotation ◽  
Posterior Fixation ◽  
Interbody Cage ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Lateral Interbody ◽  
Flexion And Extension

OBJECTIVE Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies. METHODS An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4–5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared. RESULTS The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%–82% for LIF, and 69%–86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%–87% for TLIF, 86%–91% for LIF, and 90%–92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios. CONCLUSIONS Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

Numerical investigation on the stability of human upper cervical spine (C1–C3)

2021 ◽  
pp. 1-13
Author(s):  
Waseem Ur Rahman ◽  
Wei Jiang ◽  
Guohua Wang ◽  
Zhijun Li
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Axial Rotation ◽  
Upper Cervical Spine ◽  
Fe Model ◽  
Facet Joints ◽  
Flexion Extension ◽  
Upper Cervical ◽  
The Stability

BACKGROUND: The finite element method (FEM) is an efficient and powerful tool for studying human spine biomechanics. OBJECTIVE: In this study, a detailed asymmetric three-dimensional (3D) finite element (FE) model of the upper cervical spine was developed from the computed tomography (CT) scan data to analyze the effect of ligaments and facet joints on the stability of the upper cervical spine. METHODS: A 3D FE model was validated against data obtained from previously published works, which were performed in vitro and FE analysis of vertebrae under three types of loads, i.e. flexion/extension, axial rotation, and lateral bending. RESULTS: The results show that the range of motion of segment C1–C2 is more flexible than that of segment C2–C3. Moreover, the results from the FE model were used to compute stresses on the ligaments and facet joints of the upper cervical spine during physiological moments. CONCLUSION: The anterior longitudinal ligaments (ALL) and interspinous ligaments (ISL) are found to be the most active ligaments, and the maximum stress distribution is appear on the vertebra C3 superior facet surface under both extension and flexion moments.

Inertial Loading of the Human Cervical Spine

1997 ◽  
Vol 119 (3) ◽  
pp. 237-240 ◽  
Author(s):  
N. Yoganandan ◽  
F. A. Pintar
Keyword(s):  
Cervical Spine ◽  
Wave Form ◽  
Spine Biomechanics ◽  
Human Cadaver ◽  
Kinematic Data ◽  
Flexion Extension ◽  
Angular Velocities ◽  
Applied Forces ◽  
Inertial Loading ◽  
Flexion And Extension

While the majority of experimental cervical spine biomechanics research has been conducted using slowly applied forces and/or moments, or dynamically applied forces with contact, little research has been performed to delineate the biomechanics of the human neck under inertial “noncontact” type forces. This study was designed to develop a comprehensive methodology to induce these loads. A minisled pendulum experimental setup was designed to test specimens (such as human cadaver neck) at subfailure or failure levels under different loading modalities including flexion, extension, and lateral bending. The system allows acceleration/deceleration input with varying wave form shapes. The test setup dynamically records the input and output strength information such as forces, accelerations, moments, and angular velocities; it also has the flexibility to obtain the temporal overall and local kinematic data of the cervical spine components at every vertebral level. These data will permit a complete biomechanical structural analysis. In this paper, the feasibility of the methodology is demonstrated by subjecting a human cadaver head-neck complex with intact musculature and skin under inertial flexion and extension whiplash loading at two velocities.

scholarly journals Subject-Specific Inverse Dynamics of the Head and Cervical Spine During in Vivo Dynamic Flexion-Extension

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
William J. Anderst ◽  
William F. Donaldson ◽  
Joon Y. Lee ◽  
James D. Kang
Keyword(s):  
Finite Element ◽  
Cervical Spine ◽  
Inverse Dynamics ◽  
Total Force ◽  
Finite Element Models ◽  
Moment Arms ◽  
Flexion Extension ◽  
Subject Specific

The effects of degeneration and surgery on cervical spine mechanics are commonly evaluated through in vitro testing and finite element models derived from these tests. The objectives of the current study were to estimate the load applied to the C2 vertebra during in vivo functional flexion-extension and to evaluate the effects of anterior cervical arthrodesis on spine kinetics. Spine and head kinematics from 16 subjects (six arthrodesis patients and ten asymptomatic controls) were determined during functional flexion-extension using dynamic stereo X-ray and conventional reflective markers. Subject-specific inverse dynamics models, including three flexor muscles and four extensor muscles attached to the skull, estimated the force applied to C2. Total force applied to C2 was not significantly different between arthrodesis and control groups at any 10 deg increment of head flexion-extension (all p values ≥ 0.937). Forces applied to C2 were smallest in the neutral position, increased slowly with flexion, and increased rapidly with extension. Muscle moment arms changed significantly during flexion-extension, and were dependent upon the direction of head motion. The results suggest that in vitro protocols and finite element models that apply constant loads to C2 do not accurately represent in vivo cervical spine kinetics.

Stress Changes in Intervertebral Discs of the Cervical Spine Due to Partial Discectomies and Fusion

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Abraham Tchako ◽  
Ali M. Sadegh
Keyword(s):  
Cervical Spine ◽  
Bone Graft ◽  
Vertebral Body ◽  
Surgical Procedure ◽  
Donor Site ◽  
Compressive Force ◽  
High Rate ◽  
Flexion Extension ◽  
Stress Changes ◽  
Autologous Bone

Spine discectomy and fusion is a widely used surgical procedure to correct irreversible degenerative diseases and injuries to the intervertebral disk. The surgical procedure involves the removal of the damage disk material, the decortication of the fusion site, and the placement of the bone graft. Fusion is believed to generate additional stresses in the neighboring disks, which can subsequently lead to new disk degeneration and re-operation. The autologous bone has proven to be the best material for the fusion. However, the autologous bone has three major disadvantages: the high rate of donor site morbidity, the limited and sometimes poor quality of the amounts of bone available, and the extra operative time needed for harvest. For these reasons this study is undertaken to estimate the optimum amount of bone graft needed for a discectomy and correlate it to the change in stress in adjacent levels. A detailed and validated 3D finite element model of the complete human cervical spine (C1-T1) was altered to simulate segmental full and partial discectomies. One full fusion (bone graft occupies about 90% of the vertebral body) and seven partial fusions (bone graft occupies about 10%, 20%, 30%, 40%, 50%, 65%, and 75% of the vertebral body) were simulated at each of the four mid- and lower single levels of the cervical spine and the relationship between the change in stresses in the adjacent levels and the bone graft size (area) was studied. The changes in stress were compared with the previously obtained results of the unfused models. The fused and unfused models were preloaded with a 73.6 N compressive force representing the weight of the head and with a 1.5 Nm physiological moment in flexion, extension, lateral bending, and axial rotation. More than 132 cases were analyzed. The results showed that the necessary amount of bone graft needed for discectomy depends on the cervical disk level to be fused and varies between 30% and 75% of the disk area. The results also suggested that there is a threshold size of the bone graft area, before and/or after which, the long-term effects of the change in stresses in adjacent disks are biomechanically consequential.

In Vitro Study of the C2-C7 Sheep Cervical Spine

2011 ◽  
Author(s):  
Nicole A. DeVries ◽  
Anup A. Gandhi ◽  
Douglas C. Fredericks ◽  
Joseph D. Smucker ◽  
Nicole M. Grosland
Keyword(s):  
Cervical Spine ◽  
Surgical Techniques ◽  
In Vitro Study ◽  
Axial Rotation ◽  
Lateral Bending ◽  
Disc Space ◽  
Flexion Extension ◽  
Biomechanical Responses ◽  
Experimental Biomechanics

Due to the limited availability of human cadaveric specimens, animal models are often utilized for in vitro studies of various spinal disorders and surgical techniques. Sheep spines have similar geometry, disc space, and lordosis as compared to humans [1,2]. Several studies have identified the geometrical similarities between the sheep and human spine; however these studies have been limited to quantifying the anatomic dimensions as opposed to the biomechanical responses [2–3]. Although anatomical similarities are important, biomechanical correspondence is imperative to understand the effects of disorders, surgical techniques, and implant designs. Some studies [3–5] have focused on experimental biomechanics of the sheep cervical functional spinal units (FSUs). Szotek and colleagues [1] studied the biomechanics of compression and impure flexion-extension for the C2-C7 intact sheep spine. However, to date, there is no comparison of the sheep spine using pure flexion-extension, lateral bending, or axial rotation moments for multilevel specimen. Therefore, the purpose of this study was to conduct in vitro testing of the intact C2-C7 sheep cervical spine.

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