Examining motion in the cervical spine I: imaging systems and measurement techniques

Instruments for measuring mobility in the cervical spine range from plumb-lines and inclinometers to sophisticated optoelectronic systems. In order to investigate the need and possible uses for an enhancement to a new diagnostic instrument, we examine some of the available diagnostic systems suitable for cervical motion analysis. These should be of practical use in a clinical setting for the diagnosis of soft tissue injuries. We begin by evaluating the respective roles of plain radiographs, cineradiography, computer tomography, and magnetic resonance imaging in examining the cervical spine. Then we consider Moiré photography, inclinometers, and some opto-electronic scanners, as well as the mathematical techniques needed to correlate skin and spine motion with these devices. We find that there does not appear to be an effective non-invasive tool for comprehensive clinical cervical motion analysis; in particular, coupled joint motion is inadequately quantified. Improperly diagnosed cervical spine injuries, such as hyperextension and hyperflexion, may result in chronic long-term effects. Therefore, instrumentation that would permit objective, routine clinical evaluation of patients could help to avoid such situations.     

Between-session reliability of opto-electronic motion capture in measuring sagittal posture and 3-D ranges of motion of the thoracolumbar spine

This study evaluated between-session reliability of opto-electronic motion capture to measure trunk posture and three-dimensional ranges of motion (ROM). Nineteen healthy participants aged 24–74 years underwent spine curvature, pelvic tilt and trunk ROM measurements on two separate occasions. Rigid four-marker clusters were attached to the skin overlying seven spinous processes, plus single markers on pelvis landmarks. Rigid body rotations of spine marker clusters were calculated to determine neutral posture and ROM in flexion, extension, total lateral bending (left-right) and total axial rotation (left-right). Segmental spine ROM values were in line with previous reports using opto-electronic motion capture. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated as measures of between-session reliability and measurement error, respectively. Retroreflective markers showed fair to excellent between-session reliability to measure thoracic kyphosis, lumbar lordosis, and pelvic tilt (ICC = 0.82, 0.63, and 0.54, respectively). Thoracic and lumbar segments showed highest reliabilities in total axial rotation (ICC = 0.78) and flexion-extension (ICC = 0.77–0.79) ROM, respectively. Pelvic segment showed highest ICC values in flexion (ICC = 0.78) and total axial rotation (ICC = 0.81) trials. Furthermore, it was estimated that four or fewer repeated trials would provide good reliability for key ROM outcomes, including lumbar flexion, thoracic and lumbar lateral bending, and thoracic axial rotation. This demonstration of reliability is a necessary precursor to quantifying spine kinematics in clinical studies, including assessing changes due to clinical treatment or disease progression.     

Contact pressure in the facet joint during sagittal bending of the cadaveric cervical spine

The facet joint contributes to the normal biomechanical function of the spine by transmitting loads and limiting motions via articular contact. However, little is known about the contact pressure response for this joint. Such information can provide a quantitative measure of the facet joint's local environment. The objective of this study was to measure facet pressure during physiologic bending in the cervical spine, using a joint capsule-sparing technique. Flexion and extension bending moments were applied to six human cadaveric cervical spines. Global motions (C2-T1) were defined using infra-red cameras to track markers on each vertebra. Contact pressure in the C5-C6 facet was also measured using a tip-mounted pressure transducer inserted into the joint space through a hole in the postero-inferior region of the C5 lateral mass. Facet contact pressure increased by 67.6 ± 26.9 kPa under a 2.4 Nm extension moment and decreased by 10.3 ± 9.7 kPa under a 2.7 Nm flexion moment. The mean rotation of the overall cervical specimen motion segments was 9.6 ± 0.8° and was 1.6 ± 0.7° for the C5-C6 joint, respectively, for extension. The change in pressure during extension was linearly related to both the change in moment (51.4 ± 42.6 kPa/Nm) and the change in C5-C6 angle (18.0 ± 108.9 kPa/deg). Contact pressure in the inferior region of the cervical facet joint increases during extension as the articular surfaces come in contact, and decreases in flexion as the joint opens, similar to reports in the lumbar spine despite the difference in facet orientation in those spinal regions. Joint contact pressure is linearly related to both sagittal moment and spinal rotation. Cartilage degeneration and the presence of meniscoids may account for the variation in the pressure profiles measured during physiologic sagittal bending. This study shows that cervical facet contact pressure can be directly measured with minimal disruption to the joint and is the first to provide local pressure values for the cervical joint in a cadaveric model.     

Accuracy of an optical active-marker system to track the relative motion of rigid bodies

The measurement of relative motion between two moving bones is commonly accomplished for in vitro studies by attaching to each bone a series of either passive or active markers in a fixed orientation to create a rigid body (RB). This work determined the accuracy of motion between two RBs using an Optotrak optical motion capture system with active infrared LEDs. The stationary noise in the system was quantified by recording the apparent change in position with the RBs stationary and found to be 0.04 degrees and 0.03 mm. Incremental 10 degrees rotations and 10-mm translations were made using a more precise tool than the Optotrak. Increasing camera distance decreased the precision or increased the range of values observed for a set motion and increased the error in rotation or bias between the measured and actual rotation. The relative positions of the RBs with respect to the camera-viewing plane had a minimal effect on the kinematics and, therefore, for a given distance in the volume less than or close to the precalibrated camera distance, any motion was similarly reliable. For a typical operating set-up, a 10 degrees rotation showed a bias of 0.05 degrees and a 95% repeatability limit of 0.67 degrees. A 10-mm translation showed a bias of 0.03 mm and a 95% repeatability limit of 0.29 mm. To achieve a high level of accuracy it is important to keep the distance between the cameras and the markers near the distance the cameras are focused to during calibration.     

Importance of nonlinear and multivariable flexibility coefficients in the prediction of human cervical spine motion

The flexibility matrix currently forms the basis for multibody dynamics models of cervical spine motion. While studies have aimed to determine cervical motion segment behavior, their accuracy and utility have been limited by both experimental and analytical assumptions. Flexibility terms have been primarily represented as constants despite the spine's nonlinear stiffening response. Also, nondiagonal terms, describing coupled motions, of the matrices are often omitted. Currently, no study validates the flexibility approach for predicting vertebral motions; nor have the effects of matrix approximations and simplifications been quantified. Therefore, the purpose of this study is to quantify flexibility relationships for cervical motion segments, examine the importance of nonlinear components of the flexibility matrix, and determine the extent to which multivariable relationships may alter motion prediction. To that end, using unembalmed human cervical spine motion segments, a full battery of flexibility tests were performed for a neutral orientation and also following an axial pretorque. Primary and coupled matrix components were described using linear and piecewise nonlinear incremental constants. A third matrix approach utilized multivariable incremental relationships. Measured motions were predicted using structural flexibility methods and evaluated using RMS error between predicted and measured responses. A full set of flexibility relationships describe primary and coupled motions for C3-C4 and C5-C6. A flexibility matrix using piecewise incremental responses offers improved predictions over one using linear methods (p<0.01). However, no significant improvement is obtained using nonlinear terms represented by a multivariable functional approach (p<0.2). Based on these findings, it is suggested that a multivariable approach for flexibility is more demanding experimentally and analytically while not offering improved motion prediction.     

The effect of follower load on the intersegmental coupled motion characteristics of the human thoracic spine: An in vitro study using entire rib cage specimens

The mechanical coupling behaviour of the thoracic spine is still not fully understood. For the validation of numerical models of the thoracic spine, however, the coupled motions within the single spinal segments are of importance to achieve high model accuracy. In the present study, eight fresh frozen human thoracic spinal specimens (C7-L1, mean age 54 ± 6 years) including the intact rib cage were loaded with pure bending moments of 5 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) with and without a follower load of 400 N. During loading, the relative motions of each vertebra were monitored. Follower load decreased the overall ROM (T1-T12) significantly (p < 0.01) in all primary motion directions (extension: −46%, left LB: −72%, right LB: −72%, left AR: −26%, right AR: −26%) except flexion (−36%). Substantial coupled motion was found in lateral bending with ipsilateral axial rotation, which increased after a follower load was applied, leading to a dominant axial rotation during primary lateral bending, while all other coupled motions in the different motion directions were reduced under follower load. On the monosegmental level, the follower load especially reduced the ROM of the upper thoracic spine from T1-T2 to T4-T5 in all motion directions and the ROM of the lower thoracic spine from T9-T10 to T11-T12 in primary lateral bending. The facet joints, intervertebral disc morphologies, and the sagittal curvature presumably affect the thoracic spinal coupled motions depending on axial compressive preloading. Using these results, the validation of numerical models can be performed more accurately.     

A new method for motion capture of the scapula using an optoelectronic tracking device: a feasibility study

Optoelectronic tracking systems are rarely used in 3D studies examining shoulder movements including the scapula. Among the reasons is the important slippage of skin markers with respect to scapula. Methods using electromagnetic tracking devices are validated and frequently applied. Thus, the aim of this study was to develop a new method for in vivo optoelectronic scapular capture dealing with the accepted accuracy issues of validated methods.

Eleven arm positions in three anatomical planes were examined using five subjects in static mode. The method was based on local optimisation, and recalculation procedures were made using a set of five scapular surface markers.

The scapular rotations derived from the recalculation-based method yielded RMS errors comparable with the frequently used electromagnetic scapular methods (RMS up to 12.6° for 150° arm elevation). The results indicate that the present method can be used under careful considerations for 3D kinematical studies examining different shoulder movements.     

Examining the complexity of human RNA polymerase complexes using HaloTag technology coupled to label free quantitative proteomics

Efficient determination of protein interactions and cellular localization remains a challenge in higher order eukaryotes and creates a need for robust technologies for functional proteomics studies. To address this, the HaloTag technology was developed for highly efficient and rapid isolation of intracellular complexes and correlative in vivo cellular imaging. Here we demonstrate the strength of this technology by simultaneous capture of human eukaryotic RNA polymerases (RNAP) I, II, and III using a shared subunit, POLR2H, fused to the HaloTag. Affinity purifications showed successful isolation, as determined using quantitative proteomics, of all RNAP core subunits, even at expression levels near endogenous. Transient known RNAP II interacting partners were identified as well as three previously uncharacterized interactors. These interactions were validated and further functionally characterized using cellular imaging. The multiple capabilities of the HaloTag technology demonstrate the ability to efficiently isolate highly challenging multiprotein complexes, discover new interactions, and characterize cellular localization.     

Investigation of whiplash injuries in the upper cervical spine using a detailed neck model

Whiplash injuries continue to have significant societal cost; however, the mechanism and location of whiplash injury is still under investigation. Recently, the upper cervical spine ligaments, particularly the alar ligament, have been identified as a potential whiplash injury location. In this study, a detailed and validated explicit finite element model of a 50th percentile male cervical spine in a seated posture was used to investigate upper cervical spine response and the potential for whiplash injury resulting from vehicle crash scenarios. This model was previously validated at the segment and whole spine levels for both kinematics and soft tissue strains in frontal and rear impact scenarios. The model predicted increasing upper cervical spine ligament strain with increasing impact severity. Considering all upper cervical spine ligaments, the distractions in the apical and alar ligaments were the largest relative to their failure strains, in agreement with the clinical findings. The model predicted the potential for injury to the apical ligament for 15.2 g frontal or 11.7 g rear impacts, and to the alar ligament for a 20.7 g frontal or 14.4 g rear impact based on the ligament distractions. Future studies should consider the effect of initial occupant position on ligament distraction.     

Genetic characterization of an isolated alpine population using seroprotein markers: Vallouise (Briançonnais)

The aim of the “Dauphiné Project” is to reconstruct, with a wide perspective and multidisciplinary approach, the anthropological history of some mountain populations in both the French and the Italian parts of the Ancient Dauphiné. Within the “Dauphiné Project”, the present study is an analysis of seroproteins conducted on blood samples of subjects living in Vallouise, small mountain community (Briançonnais); they are male and female adults from families native to the zones for at least two generations. In particular, the third component of complement (C3), the group specific component (Gc) and properdin B factor (Bf) were considered, these being very important markers in human genetics research. The data for these systems are the first results of the biological study of populations of the Western Alps. They add to our otherwise scantly knowledge about the distribution of these polymorphisms in the populations under study. The results were compared with those in the literature on European populations, particularly of the Mediterranean area, in order to identify origins and microevolutionary processes, as well as biotransformations related to environmental adaptation.     

The intercostal to phrenic nerve transfer: an effective means of reanimating the diaphragm in patients with high cervical spine injury

Nerve transfers have been well described for the treatment of congenital and traumatic injuries in the brachial plexus and extremities. This series is the first to describe nerve transfers to reanimate the diaphragm in patients confined to long-term positive pressure ventilation because of high cervical spine injury. Patients who have sustained injury to the spinal cord at the C3 to C5 level suffer axonal loss in the phrenic nerve. They can neither propagate a nerve stimulus nor respond to implanted diaphragmatic pacing devices (electrophrenic respiration). Ten nerve transfers were performed in six patients who met these conditions. The procedures used end-to-end anastomoses from the fourth intercostal to the phrenic nerve approximately 5 cm above the diaphragm. A phrenic nerve pacemaker was implanted as part of the procedure and was placed distal to the anastomosis. Each week, the pacemaker was activated to test for diaphragmatic response. Once diaphragm movement was documented, diaphragmatic pacing was instituted. Eight of the 10 transfers have had more than 3 months to allow for axonal regeneration. Of these, all eight achieved successful diaphragmatic pacing (100 percent). The average interval from surgery to diaphragm response to electrical stimulation was 9 months. All patients were able to tolerate diaphragmatic pacing as an alternative to positive pressure ventilation, as judged by end tidal CO2 values, tidal volumes, and patient comfort. Intercostal to phrenic nerve transfer with diaphragmatic pacing is a viable means of liberating patients with high cervical spine injury from long-term mechanical ventilation.     

Design and validation of an unconstrained loading system to measure the envelope of motion in the rabbit knee joint

An unconstrained loading system was developed to measure the passive envelope of joint motion in an animal model commonly used to study ligament healing and joint arthritis. The design of the five-degree-of-freedom system allowed for unconstrained knee joint loading throughout flexion with repeated removal and reapplication of the device to a specimen. Seven New Zealand White rabbit knees were subjected to varus, valgus, internal and external loads, and the resulting envelopes of motion were recorded using an electromagnetic tracking device. Intra-specimen reproducibility was excellent when measured in one specimen, with maximal rotational differences of 0.6 and 0.3 deg between the fourth and fifth testing cycles for the varus (VR) and valgus (VL) envelopes, respectively. Similarly, the maximal internal (INT) and external (EXT) envelope differences were 0.5 and 0.4 deg, respectively, between the fourth and fifth cycles. Good inter-animal envelope reproducibility was also observed with consistent motion pathways for each loading condition. A maximal VR-VL laxity of 17.9 +/- 2.3 deg was recorded at 95 deg flexion for the seven knees tested. The maximal INT-EXT laxity of 75.2 +/- 4.8 deg occurred at 50 deg flexion. Studies on measurement reproducibility of re-applying individual testing components demonstrated a maximal error of 1.2 +/- 0.7 deg. Serial removal and re-application (test-retest) of the complete measuring system to one cadaveric knee demonstrated maximal envelope differences of less than 0.7 deg for VR-VL rotation and 2.1 deg for INT-EXT rotation. Our results demonstrate that the measuring system is reproducible and capable of accurate evaluation of knee joint motion. Baseline in vitro data were generated on normal joint kinematics for future in-vivo studies with this system, evaluating ligament healing and disease progression in arthritis models.     

Examining the phylogeny of the Australasian Lymnaeidae (Heterobranchia: Pulmonata: Gastropoda) using mitochondrial, nuclear and morphological markers

We examined the species groups relationships of the freshwater snail genus Austropeplea using mitochondrial, nuclear and morphological markers in addition to traditional methods of shell shape analysis. Based primarily on the results of a combined molecular and morphological analysis, samples of the nominal species A. tomentosa form distinct lineages. The New Zealand populations of A. tomentosa are a very distinct lineage from any of the Australian populations attributed to A. tomentosa. Furthermore, within the Australian group, three lineages, south Australia, Tasmania and eastern Australia, appear to have undergone recent and/or rapid speciation events. Samples assigned to A. lessoni were resolved as two distinct lineages, representing the eastern and northern Australian populations. Kutikina hispida was resolved within the Australian A. tomentosa clade. Molecular results for A. viridis suggests that it is also composed of at least two distinct lineages that could be treated as species. Incongruence observed between the single mitochondrial, nuclear and morphological topologies highlight the importance of using a number of different datasets in the delimitation of species-group taxa.     

Development and characterization of 24 microsatellite markers in Primula tosaensis,an endangered primrose,using MiSeq

Primula tosaensis (Primulaceae) is an endangered primrose endemic to Japan. In this study, 24 novel microsatellite markers were developed using Illumina MiSeq sequencing to facilitate conservation of this endangered species. The genetic diversity and polymorphisms of these novel markers were measured in 32 individuals from a wild P. tosaensis population. The number of alleles and expected heterozygosities ranged from 2 to 5 (mean = 2.8) and from 0.119 to 0.724 (mean = 0.395), respectively. All loci were in Hardy–Weinberg equilibrium. The markers developed in this study will provide a powerful and practical tool for investigating the population structure and genetic diversity of P. tosaensis.     

Soft tissue artefacts of skin markers on the lower limb during cycling: Effects of joint angles and pedal resistance

Soft tissue artefacts (STA) are a major error source in skin marker-based measurement of human movement, and are difficult to eliminate non-invasively. The current study quantified in vivo the STA of skin markers on the thigh and shank during cycling, and studied the effects of knee angles and pedal resistance by using integrated 3D fluoroscopy and stereophotogrammetry. Fifteen young healthy adults performed stationary cycling with and without pedal resistance, while the marker data were measured using a motion capture system, and the motions of the femur and tibia/fibula were recorded using a bi-plane fluoroscopy-to-CT registration method. The STAs with respect to crank and knee angles over the pedaling cycle, as well as the within-cycle variations, were obtained and compared between resistance conditions. The thigh markers showed greater STA than the shank ones, the latter varying linearly with adjacent joint angles, the former non-linearly with greater within-cycle variability. Both STA magnitudes and within-cycle variability were significantly affected by pedal resistance (p < 0.05). The STAs appeared to be composed of one component providing the stable and consistent STA patterns and another causing their variations. Mid-segment markers experienced smaller STA ranges than those closer to a joint, but tended to have greater variations primarily associated with pedal resistance and muscle contractions. The current data will be helpful for a better choice of marker positions for data collection, and for developing methods to compensate for both stable and variation components of the STA.     

In-vivo measurement of dynamic joint motion using high speed biplane radiography and CT: application to canine ACL deficiency

Dynamic assessment of three-dimensional (3D) skeletal kinematics is essential for understanding normal joint function as well as the effects of injury or disease. This paper presents a novel technique for measuring in-vivo skeletal kinematics that combines data collected from high-speed biplane radiography and static computed tomography (CT). The goals of the present study were to demonstrate that highly precise measurements can be obtained during dynamic movement studies employing high frame-rate biplane video-radiography, to develop a method for expressing joint kinematics in an anatomically relevant coordinate system and to demonstrate the application of this technique by calculating canine tibio-femoral kinematics during dynamic motion. The method consists of four components: the generation and acquisition of high frame rate biplane radiographs, identification and 3D tracking of implanted bone markers, CT-based coordinate system determination, and kinematic analysis routines for determining joint motion in anatomically based coordinates. Results from dynamic tracking of markers inserted in a phantom object showed the system bias was insignificant (-0.02 mm). The average precision in tracking implanted markers in-vivo was 0.064 mm for the distance between markers and 0.31 degree for the angles between markers. Across-trial standard deviations for tibio-femoral translations were similar for all three motion directions, averaging 0.14 mm (range 0.08 to 0.20 mm). Variability in tibio-femoral rotations was more dependent on rotation axis, with across-trial standard deviations averaging 1.71 degrees for flexion/extension, 0.90 degree for internal/external rotation, and 0.40 degree for varus/valgus rotation. Advantages of this technique over traditional motion analysis methods include the elimination of skin motion artifacts, improved tracking precision and the ability to present results in a consistent anatomical reference frame.     

Cervical spine motion in the sagittal plane (I) range of motion of actually performed movements, an X-ray cinematographic study

A fast method has been developed to determine the position of the outlines of bony structures on X-ray photographs of the cervical spine movements in the sagittal plane (105 mm spot film camera; 4 frames per second; about 10 seconds per complete anteflexion-retroflexion or vice versa). This method corrects for incongruity of the vertebral contours on consecutive frames due to motion in another than the sagittal plane. It also automatically corrects erroneously marked points. This method has been used to determine segmental range of motion (SROM) and total range of motion of the head with respect to the seventh cervical vertebra (TROM). It is shown that SROM may be larger when frames of intermediate instead of extreme positions of the film are considered. In ten test persons without cervical complaints the interindividual variability of SROM turned out to be comparable to the ones found with older methods. Intraindividual variability of SROM and TROM was determined by registration at three different measuring sessions (0, 2 and 10 weeks). This intraindividual variability is high, especially in the cranial and caudal parts of the cervical spine. It is concluded that SROM and TROM are unsuitable to be used as a parameter of cervical spine mobility.