Instantaneous helical axis methodology to identify aberrant neck motion

Cervical spine and muscle adaptation after spaceflight and relationship to herniation risk: protocol from 'Cervical in Space' trial

Background

Astronauts have a higher risk of cervical intervertebral disc herniation. Several mechanisms have been attributed as causative factors for this increased risk. However, most of the previous studies have examined potential causal factors for lumbar intervertebral disc herniation only. Hence, we aim to conduct a study to identify the various changes in the cervical spine that lead to an increased risk of cervical disc herniation after spaceflight.

Methods

A cohort study with astronauts will be conducted. The data collection will involve four main components: a) Magnetic resonance imaging (MRI); b) cervical 3D kinematics; c) an Integrated Protocol consisting of maximal and submaximal voluntary contractions of the neck muscles, endurance testing of the neck muscles, neck muscle fatigue testing and questionnaires; and d) dual energy X-ray absorptiometry (DXA) examination. Measurements will be conducted at several time points before and after astronauts visit the International Space Station. The main outcomes of interest are adaptations in the cervical discs, muscles and bones.

Discussion

Astronauts are at higher risk of cervical disc herniation, but contributing factors remain unclear. The results of this study will inform future preventive measures for astronauts and will also contribute to the understanding of intervertebral disc herniation risk in the cervical spine for people on Earth. In addition, we anticipate deeper insight into the aetiology of neck pain with this research project.

Trial registration

German Clinical Trials Register, DRKS00026777. Registered on 08 October 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05684-0.

Kinematics of the Cervical Spine Under Healthy and Degenerative Conditions: A Systematic Review

Knowledge of spinal kinematics is essential for the diagnosis and management of spinal diseases. Distinguishing between physiological and pathological motion patterns can help diagnose these diseases, plan surgical interventions and improve relevant tools and software. During the last decades, numerous studies based on diverse methodologies attempted to elucidate spinal mobility in different planes of motion. The authors aimed to summarize and compare the evidence about cervical spine kinematics under healthy and degenerative conditions. This includes an illustrated description of the spectrum of physiological cervical spine kinematics, followed by a comparable presentation of kinematics of the degenerative cervical spine. Data was obtained through a systematic MEDLINE search including studies on angular/translational segmental motion contribution, range of motion, coupling and center of rotation. As far as the degenerative conditions are concerned, kinematic data regarding disc degeneration and spondylolisthesis were available. Although the majority of the studies identified repeating motion patterns for most motion planes, discrepancies associated with limited sample sizes and different imaging techniques and/or spine configurations, were noted. Among healthy/asymptomatic individuals, flexion extension (FE) and lateral bending (LB) are mainly facilitated by the subaxial cervical spine. C4-C5 and C5-C6 were the major FE contributors in the reported studies, exceeding the motion contribution of sub-adjacent segments. Axial rotation (AR) greatly depends on C1-C2. FE range of motion (ROM) is distributed between the atlantoaxial and subaxial segments, while AR ROM stems mainly from the former and LB ROM from the latter. In coupled motion rotation is quantitatively predominant over translation. Motion migrates caudally from C1-C2 and the center of rotation (COR) translocates anteriorly and superiorly for each successive subaxial segment. In degenerative settings, concurrent or subsequent lesions render the association between diseases and mobility alterations challenging. The affected segments seem to maintain translational and angular motion in early and moderate degeneration. However, the progression of degeneration restrains mobility, which seems to be maintained or compensated by adjacent non-affected segments. While the kinematics of the healthy cervical spine have been addressed by multiple studies, the entire nosological and kinematic spectrum of cervical spine degeneration is partially addressed. Large-scale in vivo studies can complement the existing evidence, cover the gaps and pave the way to technological and clinical breakthroughs.

Normative cervical spine kinematics of a circumduction task

Neck pain is a prevalent condition and clinical examination techniques are limited and unable to assess out-of-plane motion. Recent works investigating cervical kinematics during neck circumduction (NC), a dynamic 3D task, has shown the ability to discern those with and without neck pain. The purposes of this study were to establish 1) confidence and prediction intervals of head-to-torso kinematics during NC in a healthy cohort, 2) a baseline summative metric to quantify the duration and magnitude of deviations outside the prediction interval, and 3) the reliability of NC. Thirty-nine participants (25.6 ± 6.3 years, 19F/20M) without neck pain completed left and right NC. A two-way smoothing spline analysis of variance was utilized to determine the mean-fitted values and 90% confidence and prediction intervals for NC. A standardized effect size was calculated and aggregated across all axes (Delta RMSD aggregate), as a summative metric of motion quality. Confidence and prediction intervals were comparable for left and right NC and demonstrated excellent reliability. The average sum of the Delta RMSD aggregate was 2.76 ± 0.55 for left NC and 2.74 ± 0.63 for right NC. The results of this study demonstrate the feasibility of utilizing normative intervals of a NC task to assess head-to-torso kinematics.

Intuitive assessment of modeled lumbar spinal motion by clustering and visualization of finite helical axes

A variety of medical imaging procedures, cadaver experiments, and computer models have been utilized to capture, depict, and understand the motion of the human lumbar spine. Particular interest lies in assessing the relative movement between two adjacent vertebrae, which can be represented by a temporal evolution of finite helical axes (FHA). Mathematically, this FHA evolution constitutes a seven-dimensional quantity: one dimension for the time, two for the (normalized) direction vector, another two for the (unique) position vector, as well as one for each the angle of rotation around and the amount of translation along the axis. Predominantly in the literature, however, movements are assumed to take place in certain physiological planes on which FHA are projected. The resulting three-dimensional quantity - the so-called centrode - is easily presentable but leaves out substantial pieces of available data. Here, we investigate and assess several possibilities to visualize subsets of FHA data of increasing dimensionality. Finally, we utilize an agglomerative hierarchical clustering algorithm and propose a novel visualization technique, namely the quiver principal axis plot (QPAP), to depict the entirety of information inherent to hundreds or thousands of FHA. The QPAP method is applied to flexion-extension, lateral bending, and axial rotation movements of a lumbar spine within both a reduced model as well as a complex upper body system.

Influences of functional structures on the kinematic behavior of the cervical spine

BACKGROUND CONTEXT

A few studies have already investigated the influences of functional structures of the cervical spine on its biomechanical behavior. In most studies, this has been done by measuring the range of motion. However, this parameter lacks of qualitative information about the overall kinematic behavior, such as coupled motions or translations. These data are essential for future development of cervical implants and surgical techniques.

PURPOSE

An investigation of the influences of cervical structures on the kinematic behavior of the cervical spine under in vivo conditions is almost impossible due to ethical reasons. Therefore, an in vitro study was conducted which allowed the analysis of these influences using three-dimensional helical axes.

STUDY DESIGN/SETTING

An in vitro test applying pure moments on mono-segmental specimens was designed in order to investigate the influences of a series of structures on the kinematic behavior of the cervical spine using three-dimensional helical axes.

METHODS

In this study we extracted motion segments C2-C3, C4-C5, and C6-C7 from 6 human cadaveric specimens with an average age of 48 years. The specimens were carefully selected using X-ray images. For the in vitro experiments, seven states were defined. The first state represented the intact state of each specimen. The remaining six states correspond with the subsequent resection of the following structures in the given order: interspinous ligament, ligamentum flavum, facet capsule, vertebral arch, posterior longitudinal ligament, and anterior longitudinal ligament. Each state was tested using a well-established spine tester. Each test sequence included 3.5 quasi-static motion cycles in all three bending directions using pure moments of 1 Nm. All motions were recorded using a motion tracking device and six reflective markers which were attached to the specimens. The recordings were then used to calculate the 3D helical axes, which were matched with the X-ray images. Due to the small number of specimens, qualitative results, such as the helical axes, were analyzed using descriptive statistics.

RESULTS

In general, the overall range of motion was increased in all loading directions due to the resection steps. The least change in the kinematic behavior of the cervical spine was observed during flexion/extension. For lateral bending and axial rotation the greatest change in the pattern of the helical axes was observed during the resection of the vertebral arch. For some specimens, however, typical patterns regarding the orientation of the helical axes remained until the last state. For lateral bending, it could be observed that the deviation in the axes' orientation increased whereas for axial rotation it decreased.

CONCLUSION

Resection of the cervical ligaments are much less crucial than the removal of guiding structures such as the facet joint. Furthermore, coupled motions not only result from the orientations of the articular surfaces of the facet joints but also from the overall shape of the cervical vertebrae including the uncinate processes.

CLINICAL SIGNIFICANCE

It is well-known that coupled motions play a substantial role in cervical kinematics. However, the influences of cervical structures on the overall kinematic behavior of the cervical spine are not yet fully understood. Knowledge of these influences could help to reduce or even prevent iatrogenic degeneration after surgical intervention. Furthermore, the data provided by this study can be helpful for future developments of cervical implants as well as finite element models for more advanced numerical investigations.

Análisis de Flexo-extensión del Cuello Mediante el Uso de Visión Artificial

En el tratamiento del dolor cervical se emplean equipos y técnicas que no miden la intensidad del dolor del paciente, sino que únicamente permiten observar los daños estructurales de dicha región. Sin embargo, la evaluación de éste dolor se puede llevar a cabo al analizar las variables cinemáticas de los tres movimientos de la articulación cervical: flexo-extensión, flexo-lateral y rotación. En este trabajo estudiaremos la fiabilidad de la técnica de fotogrametría, mediante el uso de una cámara de bajo costo, denominado Kinect V1. La cámara Kinect adquirirá los parámetros cinemáticos del movimiento de flexo-extensión de la articulación del cuello y, técnicas de visión artificial y de procesamiento de imágenes de profundidad/color del sensor Kinect serán empleadas para obtener las trayectorias de los marcadores anatómicos y técnicos. Se utilizará un filtro de Kalman para corregir el seguimiento continuo de las trayectorias de los marcadores técnicos y, consecuentemente, las coordenadas espaciales de cada marcador. Los datos fueron obtenidos de siete sujetos de prueba, entre hombres y mujeres, físicamente sanos. Las edades de los sujetos están comprendidas entre 17 y 40 años. Asociados a las coordenadas de cada marcador técnico, calculamos los parámetros cinemáticos de velocidad angular, aceleración angular y desplazamiento angular, para obtener los parámetros de fiabilidad y correlación entre pruebas. Esto último se realizó al analizar el error estándar medio, el índice de correlación múltiple y los índices de correlación de Pearson, empleados para análisis clínico. El alto índice de correlación entre los ensayos realizados nos permite ratificar la fiabilidad de nuestra metodología.

Paths of the cervical instantaneous axis of rotation during active movements-patterns and reliability

The instantaneous helical axis (IHA) is a characteristic of neck movement that is very sensitive to changes in coordination and that has potential in the assessment of functional alterations. For its application in the clinical setting, normative patterns must be available, and its reliability must be established. The purpose of this work is to describe the continuous paths of the IHA during cyclic movements of flexion-extension (FE), lateral bending (LB), and axial rotation (AR) and to quantify their reliability. Fifteen healthy volunteers participated in the study; two repetitions were made on the same day (by different operators) and over an 8-day interval (by the same operator) to evaluate the inter-operator and inter-session reliability, respectively. The paths described by the IHA suggest a sequential movement of the vertebrae in the FE movement, with a large vertical displacement (mean, 10 cm). The IHA displacement in LB and AR movements are smaller. The paths described by the IHAs have a very high reliability for FE movement, although it is somewhat lower for LB and RA movements. The standard error of measurement (SEM) is less than 0.5 cm. These results show that the paths of the IHA are reliable enough to evaluate changes in the coordination of intervertebral movement. Graphical abstract A video photogrammetry system is used to record the cyclic movements of the neck, from which the continuous trajectories of the associated instantaneous helical axis (IHA) are calculated. We have analyzed the movements of flexion-extension (FE), lateral flexion (LB), and axial rotation (AR) for a sample of 15 healthy subjects. The measurements have been repeated with two different operators (in the same session) and in two separate sessions (same operator). IHA displacement patterns have been obtained in each movement, and the reliability of the measurement of such IHA trajectories has been estimated.

The role of the facet capsular ligament in providing spinal stability

Low back pain (LBP) is the most common type of pain in America, and spinal instability is a primary cause. The facet capsular ligament (FCL) encloses the articulating joints of the spine and is of particular interest due to its high innervation - as instability ensues, high stretch values likely are a cause of this pain. Therefore, this work investigated the FCL's role in providing stability to the lumbar spine. A previously validated finite element model of the L4-L5 spinal motion segment was used to simulate pure moment bending in multiple planes. FCL failure was simulated and the following outcome measures were calculated: helical axes of motion, range of motion (ROM), bending stiffness, facet joint space, and FCL stretch. ROM increased, bending stiffness decreased, and altered helical axis patterns were observed with the removal of the FCL. Additionally, a large increase in FCL stretch was measured with diminished FCL mechanical competency, providing support that the FCL plays an important role in spinal stability.

Variability of the helical axis during active cervical movements in people with chronic neck pain

BACKGROUND

Recent work described parameters of the helical axis in asymptomatic people with potential for investigating kinematic changes in the cervical region. This approach could provide novel information on movement variability in people with neck pain, however this has never been investigated. This study aimed to investigate movement variability during active neck movements performed at different speeds in people with and without chronic neck pain.

METHODS

This observational case-control study examined 18 participants with chronic neck pain of either idiopathic or traumatic origin and 18 gender-matched asymptomatic participants. Cervical kinematics were captured with 3D motion capture as people with and without chronic neck pain performed flexion-extension, bilateral lateral flexion and bilateral rotation at different speeds (natural, slow, and fast). The mean distance and mean angle parameters of the helical axis were extracted to describe 3D motion and quantify movement variability.

FINDINGS

A smaller mean distance was observed in those with neck pain compared to the asymptomatic participants during flexion-extension (P = 0.019) and rotation movements (P = 0.007). The neck pain group displayed smaller values for the mean angle during rotation movements with different speeds (P = 0.01). These findings indicate less variable movement for those with neck pain relative to the asymptomatic participants. No difference in the mean angle was observed between groups for flexion-extension and lateral flexion.

INTERPRETATION

The findings reiterate the importance of data derived from kinematic measures, and its potential for providing clinicians with further insight into the quality of active neck movements in people with chronic neck pain.

Experimental assessment of cervical ranges of motion and compensatory strategies

Background

Literature is still limited regarding reports of non-invasive assessment of the cervical range of motion in normal subjects. Investigations into compensatory motions, defined as the contribution of an additional direction to the required motion, are also limited.

The objectives of this work were to develop and assess a reliable method for measuring the cervical range of motion in order to investigate motion and compensatory strategies.

Methods and data collection

Ninety-seven no neck-related pain subjects (no severe cervical pathology, 57 women, age: 28.3 ± 7.5y. old, BMI: 22.5 ± 3.2 kg/m²) underwent a non-invasive cervical range of motion assessment protocol. In-vivo head’s motion relative to the thorax was assessed through the measurement of the main angular amplitudes in the 3 directions (flexion/extension, axial rotations and lateral inclinations) and associated compensatory motions using an opto-electronic acquisition system.

Results

The principal motion reproducibility resulted in intra-class correlation coefficients ranging from 0.81 to 0.86. The following maximum ranges of motion were found: 127.4 ± 15.1° of flexion/extension, 89.3 ± 12° of lateral inclinations and 146.4 ± 13° of axial rotations after 6 outlier exclusions. Compensatory motions highly depend on the associated principal motion: for flexion/extension: (3.5 ± 7.6;-2.1 ± 7.8°), for rotation: (25.7 ± 17.9°;0.4 ± 4.7)°, for inclination: (22.9 ± 34.7°;-0.04 ± 8.7°). Age, BMI and weight significantly correlated with flexions (p < 0.032). Motion patterns were identified through clustering.

Conclusions

This kinematic analysis has been proven to be a reliable diagnostic tool for the cervical range of motion. The non-unicity and variability of motion patterns through the clustering of motion strategy identification have been shown. Compensatory motions contributed to such motion pattern definition despite presenting significant intra-individual variability.

Head-trunk kinematics during high-velocity-low-amplitude manipulation of the cervical spine in asymptomatic subjects: helical axis computation and anatomic motion modeling

OBJECTIVE

This study aimed to analyze the in vivo 3-dimensional kinematics of the head during cervical manipulation including helical axis (HA) computation and anatomic motion representation.

METHODS

Twelve asymptomatic volunteers were included in this study. An osteopathic practitioner performed 1 to 3 manipulations (high-velocity and low-amplitude [HVLA] multiple component technique) of the cervical spine (between C2 and C5) with the patient in the sitting position. During manipulation, head motion was collected using an optoelectronic system and expressed relative to the thorax. Motion data were processed to analyze primary and coupled motions and HA parameters. Anatomic motion representation including HA was obtained.

RESULTS

During manipulation, average maximal range of motion was 39° (SD, 6°), 21° (SD, 7°), and 8° (SD, 5°) for lateral bending (LB), axial rotation (AR), and flexion extension, respectively. For the impulse period, magnitude averaged of 8° (SD, 2°), 5° (SD, 2°), and 3° (SD, 2°), for LB, AR, and flexion extension, respectively. Mean impulse velocity was 139°/s (SD, 39°/s). Concerning AR/LB ratios, an average of 0.6 (SD, 0.3) was observed for global motion, premanipulation positioning, and impulse. Mean HA was mostly located ipsilateral to the impulse side and displayed an oblique orientation.

CONCLUSION

This study demonstrated limited range of AR during cervical spine manipulation and provided new perspectives for the development of visualization tools, which might be helpful for practitioners and for the analysis of cervical manipulation using HA computation and anatomic representation of motion.

Trend-Centric Motion Visualization: Designing and Applying a New Strategy for Analyzing Scientific Motion Collections

In biomechanics studies, researchers collect, via experiments or simulations, datasets with hundreds or thousands of trials, each describing the same type of motion (e.g., a neck flexion-extension exercise) but under different conditions (e.g., different patients, different disease states, pre- and post-treatment). Analyzing similarities and differences across all of the trials in these collections is a major challenge. Visualizing a single trial at a time does not work, and the typical alternative of juxtaposing multiple trials in a single visual display leads to complex, difficult-to-interpret visualizations. We address this problem via a new strategy that organizes the analysis around motion trends rather than trials. This new strategy matches the cognitive approach that scientists would like to take when analyzing motion collections. We introduce several technical innovations making trend-centric motion visualization possible. First, an algorithm detects a motion collection's trends via time-dependent clustering. Second, a 2D graphical technique visualizes how trials leave and join trends. Third, a 3D graphical technique, using a median 3D motion plus a visual variance indicator, visualizes the biomechanics of the set of trials within each trend. These innovations are combined to create an interactive exploratory visualization tool, which we designed through an iterative process in collaboration with both domain scientists and a traditionally-trained graphic designer. We report on insights generated during this design process and demonstrate the tool's effectiveness via a validation study with synthetic data and feedback from expert musculoskeletal biomechanics researchers who used the tool to analyze the effects of disc degeneration on human spinal kinematics.

Altered helical axis patterns of the lumbar spine indicate increased instability with disc degeneration

Although the causes of low back pain are poorly defined and indistinct, degeneration of the intervertebral disc is most often implicated as the origin of pain. The biochemical and mechanical changes associated with degeneration result in the discs' inability to maintain structure and function, leading to spinal instability and ultimately pain. Traditionally, a clinical exam assessing functional range-of-motion coupled with T2-weighted MRI revealing disc morphology are used to evaluate spinal health; however, these subjective measures fail to correlate well with pain or provide useful patient stratification. Therefore, improved quantification of spinal motion and objective MRI measures of disc health are necessary. An instantaneous helical axis (IHA) approach provides rich temporal three-dimensional data describing the pathway of motion, which is easily visualized. Eighteen cadaveric osteoligamentous lumbar spines (L4-5) from throughout the degenerative spectrum were tested in a pure moment fashion. IHA were calculated for flexion-extension and lateral bending. A correlational study design was used to determine the relationship between disc measurements from quantitative T2* MRI and IHA metrics. Increased instability and out-of-plane rotation with diminished disc health was observed during lateral bending, but not flexion-extension. This new analysis strategy examines the entire pathway of motion, rather than simplifying spinal kinematics to its terminal ends of motion and provides a more sensitive kinematic measurement of disc health. Ultimately, through the use of 3D dynamic fluoroscopy or similar methods, a patient's functional IHA in lateral bending may be measured and used to assess their disc health for diagnosis, progression tracking, and treatment evaluation.

Influence of movement speed on cervical range of motion

PURPOSE

Cervical range of motion (RoM) has been the subject of many studies. However, only very few of these studies have considered the influence of movement execution speed on the cervical kinematics. The aim of this study is to evaluate the influence of movement speed on cervical RoM.

METHOD

Cervical RoM was recorded using an optoelectronic system; 32 healthy subjects performed movements in two modes: the best possible and as fast as possible.

OUTCOME MEASURES

The primary movements (flexion-extension, lateral bending, axial rotation) and coupled movements were studied. Paired Student's tests were performed to compare the two modes of movement.

RESULTS

The results showed that cervical RoM differed significantly between movement speeds. Amplitudes were higher for each movement (p < 0.001 for flexion-extension, p < 0.001 for lateral flexion, p = 0.008 for axial rotations) when movements were performed as quickly as possible. The range of movements carried out the best possible reached only 95% of those during movements carried out as fast as possible. Concerning coupled movements, an increase in rotational movements coupled to lateral flexion during fast movements was observed.

CONCLUSION

The range of motion reported in the literature corresponds to movement carried out in a mode resembling the best possible of our study. Movements made as quickly as possible can display larger motion ranges.