Dynamic motion study of the whole lumbar spine by videofluoroscopy

The Variability of Lumbar Sequential Motion Patterns: Observational Study

BACKGROUND

Physiological motion of the lumbar spine is a topic of interest for musculoskeletal health care professionals since abnormal motion is believed to be related to lumbar complaints. Many researchers have described ranges of motion for the lumbar spine, but only few have mentioned specific motion patterns of each individual segment during flexion and extension, mostly comprising the sequence of segmental initiation in sagittal rotation. However, an adequate definition of physiological motion is still lacking. For the lower cervical spine, a consistent pattern of segmental contributions in a flexion-extension movement in young healthy individuals was described, resulting in a definition of physiological motion of the cervical spine.

OBJECTIVE

This study aimed to define the lumbar spines' physiological motion pattern by determining the sequence of segmental contribution in sagittal rotation of each vertebra during maximum flexion and extension in healthy male participants.

METHODS

Cinematographic recordings were performed twice in 11 healthy male participants, aged 18-25 years, without a history of spine problems, with a 2-week interval (time point T1 and T2). Image recognition software was used to identify specific patterns in the sequence of segmental contributions per individual by plotting segmental rotation of each individual segment against the cumulative rotation of segments L1 to S1. Intraindividual variability was determined by testing T1 against T2. Intraclass correlation coefficients were tested by reevaluation of 30 intervertebral sequences by a second researcher.

RESULTS

No consistent pattern was found when studying the graphs of the cinematographic recordings during flexion. A much more consistent pattern was found during extension, especially in the last phase. It consisted of a peak in rotation in L3L4, followed by a peak in L2L3, and finally, in L1L2. This pattern was present in 71% (15/21) of all recordings; 64% (7/11) of the participants had a consistent pattern at both time points. Sequence of segmental contribution was less consistent in the lumbar spine than the cervical spine, possibly caused by differences in facet orientation, intervertebral discs, overprojection of the pelvis, and muscle recruitment.

CONCLUSIONS

In 64% (7/11) of the recordings, a consistent motion pattern was found in the upper lumbar spine during the last phase of extension in asymptomatic young male participants. Physiological motion of the lumbar spine is a broad concept, influenced by multiple factors, which cannot be captured in a firm definition yet.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03737227; https://clinicaltrials.gov/ct2/show/NCT03737227.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.2196/14741.

The reliability of video fluoroscopy, ultrasound imaging, magnetic resonance imaging and radiography for measurements of lumbar spine segmental range of motion in-vivo: A review

BACKGROUND

Lower back pain (LBP) is a principal cause of disability worldwide and is associated with a variety of spinal conditions. Individuals presenting with LBP may display changes in spinal motion. Despite this, the ability to measure lumbar segmental range of motion (ROM) non-invasively remains a challenge.

OBJECTIVE

To review the reliability of four non-invasive modalities: Video Fluoroscopy (VF), Ultrasound imaging (US), Magnetic Resonance Imaging (MRI) and Radiography used for measuring segmental ROM in the lumbar spine in-vivo.

METHODS

The methodological quality of seventeen eligible studies, identified through a systematic literature search, were appraised.

RESULTS

The intra-rater reliability for VF is excellent in recumbent and upright positions but errors are larger for intra-rater repeated movements and inter-rater reliability shows larger variation. Excellent results for intra- and inter-rater reliability are seen in US studies and there is good reliability within- and between-day. There is a large degree of heterogeneity in MRI and radiography methodologies but reliable results are seen.

CONCLUSIONS

Excellent reliability is seen across all modalities. However, VF and radiography are limited by radiation exposure and MRI is expensive. US offers a non-invasive, risk free method but further research must determine whether it yields truly consistent measurements.

A Reference Database of Standardised Continuous Lumbar Intervertebral Motion Analysis for Conducting Patient-Specific Comparisons

Lumbar instability has long been thought of as the failure of lumbar vertebrae to maintain their normal patterns of displacement. However, it is unknown what these patterns consist of. Research using quantitative fluoroscopy (QF) has shown that continuous lumbar intervertebral patterns of rotational displacement can be reliably measured during standing flexion and return motion using standardised protocols and can be used to assess patients with suspected lumbar spine motion disorders. However, normative values are needed to make individualised comparisons. One hundred and thirty-one healthy asymptomatic participants were recruited and performed guided flexion and return motion by following the rotating arm of an upright motion frame. Fluoroscopic image acquisition at 15fps was performed and individual intervertebral levels from L2-3 to L5-S1 were tracked and analysed during separate outward flexion and return phases. Results were presented as proportional intervertebral motion representing these phases using continuous means and 95%CIs, followed by verification of the differences between levels using Statistical Parametric Mapping (SPM). A secondary analysis of 8 control participants matched to 8 patients with chronic, non-specific low back pain (CNSLBP) was performed for comparison. One hundred and twenty-seven asymptomatic participants’ data were analysed. Their ages ranged from 18 to 70 years (mean 38.6) with mean body mass index 23.8 kg/m² 48.8% were female. Both the flexion and return phases for each level evidenced continuous change in mean proportional motion share, with narrow confidence intervals, highly significant differences and discrete motion paths between levels as confirmed by SPM. Patients in the secondary analysis evidenced significantly less L5-S1 motion than controls (p < 0.05). A reference database of spinal displacement patterns during lumbar (L2-S1) intersegmental flexion and return motion using a standardised motion protocol using fluoroscopy is presented. Spinal displacement patterns in asymptomatic individuals were found to be distinctive and consistent for each intervertebral level, and to continuously change during bending and return. This database may be used to allow continuous intervertebral kinematics to drive dynamic models of joint and muscular forces as well as reference values against which to make patient-specific comparisons in suspected cases of lumbar spine motion disorders.

Lumbar Intervertebral Kinematics During an Unstable Sitting Task and Its Association With Standing-Induced Low Back Pain

People developing transient low back pain during standing have altered control of their spine and hips during standing tasks, but the transfer of these responses to other tasks has not been assessed. This study used video fluoroscopy to assess lumbar spine intervertebral kinematics of people who do and do not develop standing-induced low back pain during a seated chair-tilting task. A total of 9 females and 8 males were categorized as pain developers (5 females and 3 males) or nonpain developers (4 females and 5 males) using a 2-hour standing exposure; pain developers reported transient low back pain and nonpain developers did not. Participants were imaged with sagittal plane fluoroscopy at 25 Hz while cyclically tilting their pelvises anteriorly and posteriorly on an unstable chair. Intervertebral angles, relative contributions, and anterior-posterior translations were measured for the L3/L4, L4/L5, and L5/S1 joints and compared between sexes, pain groups, joints, and tilting directions. Female pain developers experienced more extension in their L5/S1 joints in both tilting directions compared with female nonpain developers, a finding not present in males. The specificity in intervertebral kinematics to sex-pain group combinations suggests that these subgroups of pain developers and nonpain developers may implement different control strategies.

A subject-specific method to measure dynamic spinal alignment in adult spinal deformity

BACKGROUND CONTEXT

Two-dimensional static radiography currently forms the golden standard in spinal alignment measurement in adult spinal deformity (ASD). However, these static measurements offer no information on dynamic spinal behavior. To fully understand the functionality and compensation strategies of ASD patients, tools to assess dynamic spinal alignment are needed.

PURPOSE

Therefore, the aim of this study was to introduce, validate and assess the reliability of a new kinematic model to measure dynamic spinal parameters in ASD based on a polynomial function, taking into account the subject-specific anatomy.

STUDY DESIGN

Validation and reliability study OUTCOME MEASURES: Radiographic parameters, spinal kinematics and range of motion (ROM), Scoliosis Research Society Outcome Questionnaire (SRS-22), Core Outcome Measures Index (COMI).

METHODS

Spinal alignment of 23 ASD patients and 18 controls was measured using both x-rays and motion capture. Marker positions were corrected to the underlying anatomy and a polynomial function was fitted through these corrected marker positions. By comparing the polynomial method to x-ray measurements concurrent validity was assessed. Test-retest, inter- and intrarater reliability during standing and sit-to-stand (STS) were assessed on a subsample of eight ASD patients and eight controls.

RESULTS

The results showed good to excellent correlations (r>0.75) between almost all x-ray and anatomy-corrected polynomial parameters. Anatomy correction consistently led to better correlations than no correction. Intraclass correlation coefficients for the polynomial method were good to excellent (>0.75) between sessions and between and within raters and comparable or even better than radiographic measurements. Also, during STS reliability was excellent. Fair to moderate correlations were found between spinal ROM during STS and quality of life, measured with SRS-22 and COMI.

CONCLUSIONS

The results of this study indicate the polynomial method, with subject-specific anatomy correction, can measure spinal alignment in a valid and reliable way using motion capture in both healthy and deformed spines. This method makes it possible to extend evaluation in ASD from mainly static, by means of x-ray measurements, to dynamic and functional assessments.

CLINICAL SIGNIFICANCE

Eventually, this newly obtained dynamic spinal alignment information might lead to new insights in clinical decision-making and new treatment strategies, based and oriented on dynamic parameters and functionality.

Lumbar Intervertebral Motion Analysis During Flexion and Extension Cinematographic Recordings in Healthy Male Participants: Protocol

Background

Physiological motion of the lumbar spine is a subject of interest for musculoskeletal health care professionals, as abnormal motion is believed to be related to lumbar conditions and complaints. Many researchers have described ranges of motion for the lumbar spine, but only a few have mentioned specific motion patterns of each individual segment during flexion and extension. These motion patterns mostly comprise the sequence of segmental initiation in sagittal rotation. However, an adequate definition of physiological motion of the lumbar spine is still lacking. The reason for this is the reporting of different ranges of motion and sequences of segmental initiation in previous studies. Furthermore, due to insufficient fields of view, none of these papers have reported on maximum flexion and extension motion patterns of L1 to S1. In the lower cervical spine, a consistent pattern of segmental contributions was recently described. In order to understand physiological motion of the lumbar spine, it is necessary to systematically study motion patterns, including the sequence of segmental contribution, of vertebrae L1 to S1 in healthy individuals during maximum flexion and extension.

Objective

This study aims to define the lumbar spines’ physiological motion pattern of vertebrae L1, L2, L3, L4, L5, and S1 by determining the sequence of segmental contribution and the sequence of segmental initiation of motion in sagittal rotation of each vertebra during maximum flexion and extension. The secondary endpoint will be exploring the possibility of analyzing the intervertebral horizontal and vertical translation of each vertebra during maximum flexion and extension.

Methods

Cinematographic recordings will be performed on 11 healthy male participants, aged 18-25 years, without a history of spine problems. Cinematographic flexion and extension recordings will be made at two time points with a minimum 2-week interval in between.

Results

The study has been approved by the local institutional medical ethical committee (Medical Research Ethics Committee of Zuyderland and Zuyd University of Applied Sciences) on September 24, 2018. Inclusion of participants will be completed in 2020.

Conclusions

If successful, these physiological motion patterns can be compared with motion patterns of patients with lumbar conditions before or after surgery. Ultimately, researchers may be able to determine differences in biomechanics that can potentially be linked to physical complaints like low back pain.

Trial Registration

ClinicalTrials.gov NCT03737227; https://clinicaltrials.gov/ct2/show/NCT03737227

International Registered Report Identifier (IRRID)

DERR1-10.2196/14741

Discriminating spatiotemporal movement strategies during spine flexion-extension in healthy individuals

BACKGROUND CONTEXT

The spine is an anatomically complex system with numerous degrees of freedom. Due to this anatomical complexity, it is likely that multiple motor control options exist to complete a given task.

PURPOSE

To identify if distinct spine spatiotemporal movement strategies are utilized in a homogenous sample of young healthy participants.

STUDY DESIGN

Kinematic data were captured from a single cohort of male participants (N=51) during a simple, self-controlled spine flexion-extension task.

METHODS

Thoracic and lumbar flexion-extension data were analyzed to extract the continuous relative phase between each spine subsection. Continuous relative phase data were evaluated using a principal component analysis to identify major sources of variation in spine movement coordination. Unsupervised machine learning (k-means clustering) was used to identify distinct clusters present within the healthy participants sampled. Once distinguished, intersegmental spine kinematics were compared amongst clusters.

RESULTS

The findings of the current work suggest that there are distinct timing strategies that are utilized, within the participants sampled, to control spine flexion-extension movement. These strategies differentiate the sequencing of intersegmental movement and are not discriminable on the basis of simple participant demographic characteristics (ie, age, height, and body mass index), total movement time or range of motion.

CONCLUSIONS

Spatiotemporal spine flexion-extension patterns are not uniform across a population of young healthy individuals.

CLINICAL SIGNIFICANCE

Future work needs to identify whether the motor patterns characterized with this work are driven by distinct neuromuscular activation patterns, and if each given pattern has a varied risk for low back injury.

Are Stability and Instability Relevant Concepts for Back Pain?

Individuals with back pain are often diagnosed with spine instability, even though it is unclear whether the spine is susceptible to unstable behavior. The spine is a complex system with many elements that cannot be directly observed, which makes the study of spine function and direct assessment of spine instability difficult. What is known is that trunk muscle activation is adjusted to meet stability demands, which highlights that the central nervous system closely monitors threats to spine stability. The spine appears to be protected by neural coupling and mechanical coupling that prevent erroneous motor control from producing segmental instability; however, this neural and mechanical coupling could be problematic in an injured spine. Finally, instability traditionally contemplated from a mechanical and control perspective could potentially be applied to study processes involved in pain sensitization, and possibly back pain that is iatrogenic in nature. This commentary argues for a more contemporary and broadened view of stability that integrates interdisciplinary knowledge in order to capture the complexity of back pain. J Orthop Sports Phys Ther 2019;49(6):415-424. Epub 25 Apr 2019. doi:10.2519/jospt.2019.8144.

Distinguishing between typical and atypical motion patterns amongst healthy individuals during a constrained spine flexion task

Despite 'abnormal' motion being considered a risk factor for low back injury, the current understanding of 'normal' spine motion is limited. Identifying normal motion within an individual is complicated by the considerable variation in movement patterns amongst healthy individuals. Therefore, the purpose of this study was to characterize sources of variation in spine motion among a sample of healthy participants. The second objective of this study was to develop a multivariate model capable of predicting an expected movement pattern for an individual. The kinematic shape of the lower thoracic and lumbar spine was recorded during a constrained dynamic trunk flexion movement; as this is not a normal everyday movement task, movements are considered 'typical' and 'atypical' for this task rather than 'normal' and 'abnormal'. Variations in neutral standing posture accounted for 85% of the variation in spine motion throughout the task. Differences in total spine range of flexion and a regional re-weighting of range of motion between lower thoracic and lumbar regions explained a further 9% of the variance among individuals. The analysis also highlighted a difference in temporal sequencing of motion between lower thoracic and lumbar regions which explained 2% of the total movement variation. These identified sources of variation were used to select independent variables for a multivariate linear model capable of predicting an individuals' expected movement pattern. This was done as a proof-of-concept to demonstrate how the error between predicted and observed motion patterns could be used to differentiate between 'typical' and 'atypical' movement strategies.

Uneven intervertebral motion sharing is related to disc degeneration and is greater in patients with chronic, non-specific low back pain: an in vivo, cross-sectional cohort comparison of intervertebral dynamics using quantitative fluoroscopy

PURPOSE

Evidence of intervertebral mechanical markers in chronic, non-specific low back pain (CNSLBP) is lacking. This research used dynamic fluoroscopic studies to compare intervertebral angular motion sharing inequality and variability (MSI and MSV) during continuous lumbar motion in CNSLBP patients and controls. Passive recumbent and active standing protocols were used and the relationships of these variables to age and disc degeneration were assessed.

METHODS

Twenty patients with CNSLBP and 20 matched controls received quantitative fluoroscopic lumbar spine examinations using a standardised protocol for data collection and image analysis. Composite disc degeneration (CDD) scores comprising the sum of Kellgren and Lawrence grades from L2-S1 were obtained. Indices of intervertebral motion sharing inequality (MSI) and variability (MSV) were derived and expressed in units of proportion of lumbar range of motion from outward and return motion sequences during lying (passive) and standing (active) lumbar bending and compared between patients and controls. Relationships between MSI, MSV, age and CDD were assessed by linear correlation.

RESULTS

MSI was significantly greater in the patients throughout the intervertebral motion sequences of recumbent flexion (0.29 vs. 0.22, p = 0.02) and when flexion, extension, left and right motion were combined to give a composite measure (1.40 vs. 0.92, p = 0.04). MSI correlated substantially with age (R = 0.85, p = 0.004) and CDD (R = 0.70, p = 0.03) in lying passive investigations in patients and not in controls. There were also substantial correlations between MSV and age (R = 0.77, p = 0.01) and CDD (R = 0.85, p = 0.004) in standing flexion in patients and not in controls.

CONCLUSION

Greater inequality and variability of motion sharing was found in patients with CNSLBP than in controls, confirming previous studies and suggesting a biomechanical marker for the disorder at intervertebral level. The relationship between disc degeneration and MSI was augmented in patients, but not in controls during passive motion and similarly for MSV during active motion, suggesting links between in vivo disc mechanics and pain generation.

Multi-segmental thoracic spine kinematics measured dynamically in the young and elderly during flexion

In contrast to the cervical and lumbar region, the normal kinematics of the thoracic spine have not been thoroughly investigated. The aim of this study was to characterize normal multi-segmental continuous motion of the whole thoracolumbar spine, during a flexion maneuver, in young and elderly subjects. Forty-two healthy volunteers were analyzed: 21 young (age=27.00±3.96) and 21 elderly (age=70.1±3.85). Spinal motion was recorded with a motion-capture system and analyzed using a 3rd order polynomial function to approximate spinal curvature throughout the motion sequence. The average motion profiles of the two age groups were characterized. Flexion timing of the thoracic region of the spine, as compared to the lumbar spine and hips, was found to be different in the two age groups (p=0.011): a delayed/sequential motion type was observed in most of the young, whereas mostly a simultaneous motion pattern was observed in the elderly subjects. A similar trend was observed in flexion of the lower thoracic segments (p=0.017). Differences between age groups were also found for regional and segmental displacements and velocities. The reported characterization of the thoracic spine kinematics may in the future support identification of abnormal movement or be used to improve biomechanical models of the spine.

Effect of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A Dynamic In Vitro Validation Study

Spine intersegmental motion parameters and the resultant regional patterns may be useful for biomechanical classification of low back pain (LBP) as well as assessing the appropriate intervention strategy. Because of its availability and reasonable cost, two-dimensional (2D) fluoroscopy has great potential as a diagnostic and evaluative tool. However, the technique of quantifying intervertebral motion in the lumbar spine must be validated, and the sensitivity assessed. The purpose of this investigation was to (1) compare synchronous fluoroscopic and optoelectronic measures of intervertebral rotations during dynamic flexion-extension movements in vitro and (2) assess the effect of C-arm rotation to simulate off-axis patient alignment on intervertebral kinematics measures. Six cadaveric lumbar-sacrum specimens were dissected, and active marker optoelectronic sensors were rigidly attached to the bodies of L2-S1. Fluoroscopic sequences and optoelectronic kinematic data (0.15-mm linear, 0.17-0.20 deg rotational, accuracy) were obtained simultaneously. After images were obtained in a true sagittal plane, the image receptor was rotated in 5 deg increments (posterior oblique angulations) from 5 deg to 15 deg. Quantitative motion analysis (qma) software was used to determine the intersegmental rotations from the fluoroscopic images. The mean absolute rotation differences between optoelectronic values and dynamic fluoroscopic values were less than 0.5 deg for all the motion segments at each off-axis fluoroscopic rotation and were not significantly different (P > 0.05) for any of the off-axis rotations of the fluoroscope. Small misalignments of the lumbar spine relative to the fluoroscope did not introduce measurement variation in relative segmental rotations greater than that observed when the spine and fluoroscope were perpendicular to each other, suggesting that fluoroscopic measures of relative segmental rotation during flexion-extension are likely robust, even when patient alignment is not perfect.

Measurement of lumbar spine intervertebral motion in the sagittal plane using videofluoroscopy

BACKGROUND

Static radiographic techniques are unable to capture the wealth of kinematic information available from lumbar spine sagittal plane motion.

OBJECTIVE

Demonstration of a viable non-invasive technique for acquiring and quantifying intervertebral motion of the lumbar spine in the sagittal plane.

METHODS

Videofluoroscopic footage of sagittal plane lumbar spine flexion-extension in seven symptomatic volunteers (mean age = 48 yrs) and one asymptomatic volunteer (age = 54 yrs) was recorded. Vertebral bodies were digitised using customised software employing a novel vertebral digitisation scheme that was minimally affected by out-of-plane motion.

RESULTS

Measurement errors in intervertebral rotation (± 1°) and intervertebral displacement (± 0.5 mm) compare favourably with the work of others. Some subjects presenting with an identical condition (disc prolapse) exhibited a similar column vertebral flexion-extension relative to S1 (L3: max. 5.9°, min. 5.6°), while in others (degenerative disc disease) there was paradoxically a significant variation in this measurement (L3: max. 28.1°, min. 0.7°).

CONCLUSIONS

By means of a novel vertebral digitisation scheme and customised digitisation/analysis software, sagittal plane intervertebral motion data of the lumbar spine data has been successfully extracted from videofluoroscopic image sequences. Whilst the intervertebral motion signatures of subjects in this study differed significantly, the available sample size precluded the inference of any clinical trends.

Relationships between Paraspinal Muscle Activity and Lumbar Inter-Vertebral Range of Motion

Control of the lumbar spine requires contributions from both the active and passive sub-systems. Identifying interactions between these systems may provide insight into the mechanisms of low back pain. However, as a first step it is important to investigate what is normal. The purpose of this study was to explore the relationships between the lumbar inter-vertebral range of motion and paraspinal muscle activity during weight-bearing flexion in healthy controls using quantitative fluoroscopy (QF) and surface electromyography (sEMG). Contemporaneous lumbar sEMG and QF motion sequences were recorded during controlled active flexion of 60° using electrodes placed over Longissimus thoracis pars thoracis (TES), Longissimus thoracis pars lumborum (LES), and Multifidus (LMU). Normalised root mean square (RMS) sEMG amplitude data were averaged over five epochs, and the change in amplitude between epochs was calculated. The sEMG ratios of LMU/LES LMU/TES and LES/TES were also determined. QF was used to measure the maximum inter-vertebral range of motion from L2-S1, and correlation coefficients were calculated between sEMG amplitude variables and these measurements. Intra- and inter-session sEMG amplitude repeatability was also assessed for all three paraspinal muscles. The sEMG amplitude measurements were highly repeatable, and sEMG amplitude changes correlated significantly with L4-5 and L5-S1 IV-RoMmax (r = -0.47 to 0.59). The sEMG amplitude ratio of LES/TES also correlated with L4-L5 IV-RoMmax (r = -0.53). The relationships found may be important when considering rehabilitation for low back pain.

Kinematic analysis of diseased and adjacent segments in degenerative lumbar spondylolisthesis

BACKGROUND CONTEXT

Degenerative spondylolisthesis is a common pathologic condition that leads to lumbar instability and significant clinical symptoms. The effect of this pathology on adjacent lumbar motion segments, however, has not yet been studied.

PURPOSE

To characterize the motion characteristics of lumbar degenerative spondylolisthesis at both the diseased and adjacent levels in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinetic magnetic resonance imaging (kMRI).

STUDY DESIGN

Retrospective study of patient kMRIs.

PATIENT SAMPLE

One-hundred twelve patient MRIs with low-grade, single-level lumbar spondylolisthesis were included.

OUTCOME MEASURES

Angular and translational motion.

METHODS

This study compared 112 patients diagnosed with low-grade (Grade 1 or 2), single-level lumbar degenerative spondylolisthesis at L3-L4, L4-L5, or L5-S1 with 296 control patients without spondylolisthesis. Angular and translational motion were measured using patient kMRIs. The level of slip was graded according to the Meyerding classification system, and disc degeneration was classified according to the Pfirrmann system. Instability was defined as translational motion greater than 4 mm.

RESULTS

Lumbar hypomobility was often present regardless of the level of degenerative spondylolisthesis. A slip at L3-L4 resulted in the largest decrease in lumbar range of motion. Instability at the diseased level was most common at L3-L4 (36%), followed by L5-S1 (31%) and L4-L5 (30%). Instability at the adjacent segments was most frequent at L4-L5 (49%), followed by L5-S1 (34%) and L3-L4 (23%). Patients with stable spondylolisthesis generally had decreased angular motion at all lumbar levels. Translational motion at the diseased level was consistently increased. Disc degeneration was significantly greater at the level of slip for the L3-L4 and L4-L5 spondylolisthesis groups and equal to the control group in the L5-S1 group. There was no significant difference in disc degeneration at adjacent segments in L3-L4 and L4-L5 degenerative spondylolisthesis patients, but there was a significant decrease with an L5-S1 slip.

CONCLUSIONS

There were a similar percentage of patients in each degenerative spondylolisthesis group with lumbar instability. Angular motion decreased at the diseased level with L3-L4 and L5-S1 spondylolisthesis, but increased with L4-L5 spondylolisthesis. Translational motion, however, increased at the diseased level in all three groups. There was compensatory hypermobility at adjacent levels in patients with unstable spondylolisthesis at L3-L4 and L4-L5, but not at L5-S1.

Lumbar degenerative spondylolisthesis is not always unstable: clinicobiomechanical evidence

STUDY DESIGN

A clinicobiomechanical study.

OBJECTIVE

To clarify the clinicobiomechanical characteristics of a segment with lumbar degenerative spondylolisthesis (LDS) using an original intraoperative measurement system.

SUMMARY OF BACKGROUND DATA

Although radiographical evaluation of LDS is extensively performed, the diagnosis of segmental instability remains controversial. The intraoperative measurement system used in this study is the first clinically available system that performs cyclic flexion-extension displacement of the segment with all ligamentous structures intact and can determine both the stiffness (N/mm) and neutral zone (NZ, [mm/N]).

METHODS

Forty-eight patients with LDS (males/females = 19/29, 68.5 yr; group D) were compared with 48 patients with lumbar spinal stenosis without LDS (males/females = 33/15, 64.8 yr, group N) in terms of symptoms, radiological, and biomechanical results. Instability was defined as a segment with NZ more than 2 mm. Symptoms (36-Item Short Form Health Survey), radiographical findings (radiographs, magnetic resonance images, computed tomographic scans), stiffness, NZ, and frequency of instability were also compared. Risk factors for instability were analyzed by multivariate logistic regression with a forward stepwise procedure.

RESULTS

None of the physical function categories or radiological findings of 36-Item Short Form Health Survey and low back pain (visual analogue scale) differed significantly between the groups. Although NZ was significantly greater in group D (1.97) than in group N (1.73) (P < 0.05), the frequency of instability did not differ significantly between groups. Facet opening (odds ratio, 11.0; P < 0.01) and facet type (odds ratio, 6.0; P < 0.05) were significant risk factors for instability.

CONCLUSION

Neither the symptoms nor the frequency of instability differed significantly between groups. The radiological findings of spondylolisthesis did not indicate instability, but facet opening and sagittally oriented facets were indicative of instability. The results of this study demonstrated that LDS is not always unstable in the measurement setting, suggesting that the instability of LDS can stabilize spontaneously during the natural course.

LEVEL OF EVIDENCE

N/A.

Quantification of continuous in vivo flexion-extension kinematics and intervertebral strains

PURPOSE

Healthy subjects performed lumbar flexion and were assessed by video fluoroscopy to measure the in vivo kinematics of the lower lumbar motion segments.

METHODS

Fifteen healthy subjects (8 male, 7 female, 28 ± 10 years) performed lumbar flexion and extension back to neutral while their vertebrae were imaged. The sagittal plane vertebral margins of L3-S1 were identified. Lumbar angle, segmental margin strains, axial displacements, anterior-posterior (A-P) translations, and segmental rotations over the course of flexion were measured.

RESULTS

L4-L5 had the largest posterior margin Green strain (65%). Each segment displayed more axial displacement than A-P translation. Peak vertebral angulation occurred at approximately 75% of peak flexion during the extension phase.

CONCLUSION

L4-L5 exhibited the largest anterior and posterior margin strains (29 and 65%, respectively). Strains in the disc during in vivo lumbar flexion are due to both angular rotation and linear translation.

Capturing Three-Dimensional In Vivo Lumbar Intervertebral Joint Kinematics Using Dynamic Stereo-X-Ray Imaging

Availability of accurate three-dimensional (3D) kinematics of lumbar vertebrae is necessary to understand normal and pathological biomechanics of the lumbar spine. Due to the technical challenges of imaging the lumbar spine motion in vivo, it has been difficult to obtain comprehensive, 3D lumbar kinematics during dynamic functional tasks. The present study demonstrates a recently developed technique to acquire true 3D lumbar vertebral kinematics, in vivo, during a functional load-lifting task. The technique uses a high-speed dynamic stereo-radiography (DSX) system coupled with a volumetric model-based bone tracking procedure. Eight asymptomatic male participants performed weight-lifting tasks, while dynamic X-ray images of their lumbar spines were acquired at 30 fps. A custom-designed radiation attenuator reduced the radiation white-out effect and enhanced the image quality. High resolution CT scans of participants' lumbar spines were obtained to create 3D bone models, which were used to track the X-ray images via a volumetric bone tracking procedure. Continuous 3D intervertebral kinematics from the second lumbar vertebra (L2) to the sacrum (S1) were derived. Results revealed motions occurring simultaneously in all the segments. Differences in contributions to overall lumbar motion from individual segments, particularly L2–L3, L3–L4, and L4–L5, were not statistically significant. However, a reduced contribution from the L5–S1 segment was observed. Segmental extension was nominally linear in the middle range (20%–80%) of motion during the lifting task, but exhibited nonlinear behavior at the beginning and end of the motion. L5–S1 extension exhibited the greatest nonlinearity and variability across participants. Substantial AP translations occurred in all segments (5.0 ± 0.3 mm) and exhibited more scatter and deviation from a nominally linear path compared to segmental extension. Maximum out-of-plane rotations (<1.91 deg) and translations (<0.94 mm) were small compared to the dominant motion in the sagittal plane. The demonstrated success in capturing continuous 3D in vivo lumbar intervertebral kinematics during functional tasks affords the possibility to create a baseline data set for evaluating the lumbar spinal function. The technique can be used to address the gaps in knowledge of lumbar kinematics, to improve the accuracy of the kinematic input into biomechanical models, and to support development of new disk replacement designs more closely replicating the natural lumbar biomechanics.

Pedicle screw-based posterior dynamic stabilization: literature review

Posterior dynamic stabilization (PDS) indicates motion preservation devices that are aimed for surgical treatment of activity related mechanical low back pain. A large number of such devices have been introduced during the last 2 decades, without biomechanical design rationale, or clinical evidence of efficacy to address back pain. Implant failure is the commonest complication, which has resulted in withdrawal of some of the PDS devices from the market. In this paper the authors presented the current understanding of clinical instability of lumbar motions segment, proposed a classification, and described the clinical experience of the pedicle screw-based posterior dynamic stabilization devices.

In vivo studies on flexion and extension of the lumbar spine after stabilisation with a non-fusion pedicle screw system

OBJECTIVE: The aim was to determine in vivo whether pre-operative mobility of the lumbar spine (overall and segmental) is retained after surgical intervention. METHODS: Functional imaging of the lumbar spine was performed in flexion and extension, using a lateral projection under standardised conditions. This allowed assessment of the overall mobility, mobility of the instrumented mobile segments and the disc height of the adjacent cranial segment (intervertebral space; IVS) before and after surgical intervention. Images were evaluated independently by a radiologist and an orthopaedic surgeon. A comparative analysis of preoperative and postoperative functional images was carried out with the aid of a computer and appropriate software (ACES) for further assessment of the extent to which the range of movement was retained. The Oswestry Disability Index (ODI, quality of life assessment) and the visual analogue scale (VAS, pain assessment) were used as clinical criteria and compared pre-and postoperatively. The mean follow-up (FU) intervals were 13.5 days (FU 1) and 19 months (FU 2). RESULTS: Radiological results showed that the overall mobility of the lumbar spine (L1 to S1) decreased on average by one third of the flexion/extension range, from 25.0º preoperatively to 17.6º postoperatively. The segmental mobility of the monosegmental stabilisation decreased on average from 3.7º to 2.3º. The caudal segments of the bisegmental dynamic stabilisation retained their preoperative movement range of 2.6º, with a postoperative range of 2.4º. The IVS did not change. The ODI improved postoperatively from 59 (preoperative) to 39/41 (FU1/FU2) points, while the VAS (during movement) improved from 7.6 (pre-op) to 4.4/4.5 (FU1/FU2). Computer-assisted analysis showed that small and functionally insignificant micro-motion of 0.4º (error 0.12%) remained in the stabilised and unfused mobile segment. CONCLUSION: Comparison of preoperative and postoperative measurements showed that overall mobility and segmental micro-motion were retained after non-fusion stabilisation of the lumbar spine with monosegmental and bisegmental instrumentation. The adjacent cranial segment (IVS) did not collapse. Activity levels (ODI) and pain symptoms (VAS) of the patients showed significant improvement at follow-up, comparable to that reported in the literature for conventional rigid spinal fusions.

Motion characteristics of the vertebral segments with lumbar degenerative spondylolisthesis in elderly patients

OBJECTIVE

Although some studies have reported on the kinematics of the lumbar segments with degenerative spondylolisthesis (DS), few data have been reported on the in vivo 6 degree-of-freedom kinematics of different anatomical structures of the diseased levels under physiological loading conditions. This research is to study the in vivo motion characteristics of the lumbar vertebral segments with L4 DS during weight-bearing activities.

METHODS

Nine asymptomatic volunteers (mean age 54.4) and 9 patients with L4 DS (mean age 73.4) were included. Vertebral kinematics was obtained using a combined MRI/CT and dual fluoroscopic imaging technique. During functional postures (supine, standing upright, flexion, and extension), disc heights, vertebral motion patterns and instability were compared between the two groups.

RESULTS

Although anterior disc heights were smaller in the DS group than in the normal group, the differences were only significant at standing upright. Posterior disc heights were significantly smaller in DS group than in the normal group under all postures. Different vertebral motion patterns were observed in the DS group, especially in the left-right and cranial-caudal directions during flexion and extension of the body. However, the range of motions of the both groups were much less than the reported criteria of lumbar spinal instability.

CONCLUSION

The study showed that lumbar vertebra with DS has disordered motion patterns. DS did not necessary result in vertebral instability. A restabilization process may have occurred and surgical treatment should be planned accordingly.

Validity and reliability of skin markers for measurement of intersegmental mobility at L2-3 and L3-4 during lateral bending in healthy individuals: a fluoroscopy study

It is clinically important to assess kinematic parameters of lumbar spine movement to increase our understanding of lumbar mobility impairments in patients with low back pain. This is the first step for restoration of motor function. The use of non-invasive surface markers has currently attracted the interests of many researchers but scientific utilization of this technique for clinical research requires validity and reliability studies. The aim of the present study was to examine whether skin markers can be used to measure lumbar motions during lateral bending. Twelve healthy individuals were lying in prone position on the video fluoroscopy table and skin markers were attached over their spinous processes. Fluoroscopy images were taken in two positions of neutral and right lateral bending (RLB). The correlation of the L2-3 and L3-4 angles and lumbar curvature between markers and vertebrae measurements in the neutral and RLB positions was determined by Pearson Correlation Coefficient. The Intraclass correlation coefficient (ICC) was used to measure inter-examiner reliability of measurement in five participants. The results showed high reliability (ranging from 0.94 to 0.99) for angular measurements at L2-3 and L3-4 and lumbar curvature and also significant correlation between angular measurement derived from markers and vertebrae at L2-3 (r = 0.7, p = 0.015), L3-4 and lumbar curvature (r = 0.91 p = 0.001). The results showed that motions of skin markers follow the motions of the assigned underlying lumbar vertebrae. Therefore, skin markers can be confidently used for estimation of lumbar movements during lateral bending.

Kinetic magnetic resonance imaging analysis of lumbar segmental mobility in patients without significant spondylosis

PURPOSE

The purpose of this study was to examine lumbar segmental mobility using kinetic magnetic resonance imaging (MRI) in patients with minimal lumbar spondylosis.

METHODS

Mid-sagittal images of patients who underwent weight-bearing, multi-position kinetic MRI for symptomatic low back pain or radiculopathy were reviewed. Only patients with a Pfirrmann grade of I or II, indicating minimal disc disease, in all lumbar discs from L1-2 to L5-S1 were included for further analysis. Translational and angular motion was measured at each motion segment.

RESULTS

The mean translational motion of the lumbar spine at each level was 1.38 mm at L1-L2, 1.41 mm at L2-L3, 1.14 mm at L3-L4, 1.10 mm at L4-L5 and 1.01 mm at L5-S1. Translational motion at L1-L2 and L2-L3 was significantly greater than L3-4, L4-L5 and L5-S1 levels (P < 0.007). The mean angular motion at each level was 7.34° at L1-L2, 8.56° at L2-L3, 8.34° at L3-L4, 8.87° at L4-L5, and 5.87° at L5-S1. The L5-S1 segment had significantly less angular motion when compared to all other levels (P < 0.006). The mean percentage contribution of each level to the total angular mobility of the lumbar spine was highest at L2-L3 (22.45 %) and least at L5/S1 (14.71 %) (P < 0.001).

CONCLUSION

In the current study, we evaluated lumbar segmental mobility in patients without significant degenerative disc disease and found that translational motion was greatest in the proximal lumbar levels whereas angular motion was similar in the mid-lumbar levels but decreased at L1-L2 and L5-S1.

Measurement of intervertebral motion using quantitative fluoroscopy: report of an international forum and proposal for use in the assessment of degenerative disc disease in the lumbar spine

Quantitative fluoroscopy (QF) is an emerging technology for measuring intervertebral motion patterns to investigate problem back pain and degenerative disc disease. This International Forum was a networking event of three research groups (UK, US, Hong Kong), over three days in San Francisco in August 2009. Its aim was to reach a consensus on how best to record, analyse, and communicate QF information for research and clinical purposes. The Forum recommended that images should be acquired during regular trunk motion that is controlled for velocity and range, in order to minimise externally imposed variability as well as to correlate intervertebral motion with trunk motion. This should be done in both the recumbent passive and weight bearing active patient configurations. The main recommended outputs from QF were the true ranges of intervertebral rotation and translation, neutral zone laxity and the consistency of shape of the motion patterns. The main clinical research priority should initially be to investigate the possibility of mechanical subgroups of patients with chronic, nonspecific low back pain by comparing their intervertebral motion patterns with those of matched healthy controls.

VALIDATION OF THE USE OF A SKIN-MOUNTED DEVICE TO MEASURE OUT-OF-PLANE ROTATIONS OF THE SPINE FOR A ROWING ACTIVITY

Objective: To assess the accuracy of a skin-mounted device to measure lumbar spinal rotations in rowers.

Methods: Nine subjects were each imaged in 12 extremes of lateral flexion and rotation in an open MR scanner, and the movement between external MR markers fixed to the skin, and the underlying vertebral bodies was quantified.

Results: The average error in measuring the changes in the lateral flexion and rotation between the MR markers and the underlying vertebral bodies was ±5.0° (95% CI 3.5–6.4°, S.E. 0.7°) for lateral flexion and 4.4° (95% CI 3.2–5.6°, S.E 0.6°) for lateral rotation (nine subjects).

Conclusions: This study has demonstrated the accuracy of using an externally mounted device to measure out-of-plane rotations for the extremes of motion achieved during a rowing activity, allowing this system to be used to quantify deviations in rowing technique. The method could be applied to other repetitive activities of the spine.

Kinematic analysis of the lumbar spine by digital videofluoroscopy in 18 asymptomatic subjects and 9 patients with herniated nucleus pulposus

OBJECTIVES

The purpose of this study was to use digital videofluoroscopy to identify motion patterns of the lumbar spine during coronal movement in asymptomatic (normal) subjects and patients with herniated nucleus pulposus (HNP).

METHODS

Videofluoroscopic lumbar coronal motion was recorded in 18 asymptomatic volunteers and 9 patients with HNP. Measurements were made while patients bent laterally and rotated toward the right and left from a sitting position and then returned to their original position. Direction and degree of extension in the coronal plane at each motion segment and sacral descent were measured. Through the motion analysis software, the coupled pattern with lateral bending and rotation was analyzed in the asymptomatic subjects and patients with HNP.

RESULTS

Lateral flexion movement was coupled with contralateral extension and ipsilateral sacral descent but with a different rotation pattern. Rotation movement was coupled with ipsilateral extension, ipsilateral sacral descent, and ipsilateral spinous process rotation. Patients with HNP and asymptomatic subjects had similar coupled patterns but differences in amount of motion.

CONCLUSIONS

Digital videofluoroscopy showed coupled patterns during the lateral bending and rotation movements.

Segmental lumbar rotation in patients with discogenic low back pain during functional weight-bearing activities

BACKGROUND

Little information is available on vertebral motion in patients with discogenic low back pain under physiological conditions. We previously validated a combined dual fluoroscopic and magnetic resonance imaging system to investigate in vivo lumbar kinematics. The purpose of the present study was to characterize mechanical dysfunction among patients with confirmed discogenic low back pain, relative to asymptomatic controls without degenerative disc disease, by quantifying abnormal vertebral motion.

METHODS

Ten subjects were recruited for the present study. All patients had discogenic low back pain confirmed clinically and radiographically at L4-L5 and L5-S1. Motions were reproduced with use of the combined imaging technique during flexion-extension, left-to-right bending, and left-to-right twisting movements. From local coordinate systems at the end plates, relative motions of the cephalad vertebrae with respect to caudad vertebrae were calculated at each of the segments from L2 to S1. Range of motion of the primary rotations and coupled translations and rotations were determined.

RESULTS

During all three movements, the greatest range of motion was observed at L3-L4. L3-L4 had significantly greater motion than L2-L3 with left-right bending and left-right twisting movements (p < 0.05). The least motion occurred at L5-S1 for all movements; the motion at this level was significantly smaller than that at L3-L4 (p < 0.05). Range of motion during left-right bending and left-right twisting at L3-L4 was significantly larger in the degenerative disc disease group than in the normal group. The range of motion at L4-L5 was significantly larger in the degenerative group than in the normal group during flexion; however, the ranges of motion in both groups were similar during left-to-right bending and left-to-right twisting.

CONCLUSIONS

The greatest range of motion in patients with discogenic back pain was observed at L3-L4; this motion was greater than that in normal subjects, suggesting that superior adjacent levels developed segmental hypermobility prior to undergoing fusion. L5-S1 had the least motion, suggesting that segmental hypomobility ensues at this level in patients with discogenic low back pain.

Video fluoroscopic analysis of the effects of three commonly-prescribed off-the-shelf orthoses on vertebral motion

STUDY DESIGN

Fluoroscopic assessment of the effects of commercially available spinal orthotics on lumbar vertebral motion as subjects performed flexion and extension maneuvers.

OBJECTIVE

To quantitate the effects of 3 commonly available, off-the-shelf, soft, and semirigid spinal orthoses on lumbar spinal motion.

SUMMARY OF BACKGROUND DATA

Commercially available soft and semirigid orthoses are widely prescribed for patients with low back pain and, at times, following surgery. Despite this use, surprisingly little is known about the magnitude of their effects on lumbar vertebral motion.

METHODS

Ten subjects (6 men and 4 women) with an average age of 27.0 +/- 5.3 years, underwent videofluoroscopic imaging as they performed a full flexion/extension cycle. Assessments, during which the subjects were unbraced or wearing either a soft lumbrosacral orthosis (LSO), a semirigid LSO, or a semirigid thoracolumbrosacral orthosis (TLSO) were performed in random order. Images were obtained at a rate of 3.75 Hz and digitally processed to determine the sagittal rotation of the L3-L5 vertebral bodies.

RESULTS

Each of the braces produced a statistically significant reduction in overall lumbar motion during the flexion maneuver (P = 0.007) but none had a detectable effect during extension. Relative effectiveness varied by vertebral level. At the L3-L4 level, only the TLSO had a statistically significant effect on intervertebral flexion movement (32%, P = 0.003). At the L4-L5 level all the orthoses were effective (and statistically indistinguishable) in their ability to reduce intervertebral flexion movements ranging from 48% for the semirigid TLSO to about 15% to 20% for the 2 LSOs. No effects were noted for any of the orthoses at the L5-S1 level.

CONCLUSION

Commercially available soft and semirigid orthotics can have significant effects on lumbar vertebral body motion at the L3-L4 and L4-L5 levels.

Kinematic analysis of dynamic lumbar motion in patients with lumbar segmental instability using digital videofluoroscopy

The study design is a prospective, case-control. The aim of this study was to develop a reliable measurement technique for the assessment of lumbar spine kinematics using digital video fluoroscopy in a group of patients with low back pain (LBP) and a control group. Lumbar segmental instability (LSI) is one subgroup of nonspecific LBP the diagnosis of which has not been clarified. The diagnosis of LSI has traditionally relied on the use of lateral functional (flexion-extension) radiographs but use of this method has proven unsatisfactory.Fifteen patients with chronic low back pain suspected to have LSI and 15 matched healthy subjects were recruited. Pulsed digital videofluoroscopy was used to investigate kinematics of lumbar motion segments during flexion and extension movements in vivo. Intersegmental linear translation and angular displacement, and pathway of instantaneous center of rotation (PICR) were calculated for each lumbar motion segment. Movement pattern of lumbar spine between two groups and during the full sagittal plane range of motion were analyzed using ANOVA with repeated measures design. Intersegmental linear translation was significantly higher in patients during both flexion and extension movements at L5-S1 segment (p < 0.05). Arc length of PICR was significantly higher in patients for L1-L2 and L5-S1 motion segments during extension movement (p < 0.05). This study determined some kinematic differences between two groups during the full range of lumbar spine. Devices, such as digital videofluoroscopy can assist in identifying better criteria for diagnosis of LSI in otherwise nonspecific low back pain patients in hope of providing more specific treatment.

Midlumbar lateral flexion stability measured in healthy volunteers by in vivo fluoroscopy

STUDY DESIGN

Prospective fluoroscopic and electromyographic study of coronal plane lumbar spine motion in healthy male volunteers.

OBJECTIVES

Assess the intervertebral motion profiles in healthy volunteers for symmetry, regularity, and neutral zone laxity during passive recumbent lateral bending motion.

SUMMARY OF BACKGROUND DATA

Previous continuous in vivo motion studies of the lumbar spine have mainly been limited to active, weight-bearing, flexion-extension (sagittal plane) motion. No data are available for passive lateral bending or to indicate the motion profiles when muscle activity is minimized.

METHODS

Thirty asymptomatic male volunteers underwent video-fluoroscopy of their lumbar spines during passive, recumbent lumbar lateral bending through 80 degrees using a motor-driven motion table. Approximately 120 consecutive images of segments L2-L5 were captured, and the position of each vertebra was tracked throughout the sequence using automated frame-to-frame registration. Reference intervals for intervertebral motion parameters were calculated. Surface electromyography recordings of erector spinae were obtained in a similar group of volunteers using the same protocol without fluoroscopy to determine to what extent the motion was completely passive.

RESULTS

Correlations between intervertebral and lumbar motion were always positive in controls and asymmetry was less than 55% of intervertebral range. The upper reference interval for the slope of intervertebral rotation in the first 10 degrees of trunk motion did not exceed 0.46 for any level. Muscle electrical activity during the motion was very low. Examples from patient studies showed markedly different results.

CONCLUSION

These results suggest that reference limits from asymptomatic data for coronal plane passive recumbent intervertebral motion may be a useful resource for investigating the relationship between symptoms of chronic (nonspecific) low back pain and biomechanics and in the clinical assessment of patients and interventions that target the passive holding elements of the spine. Data pooling from multiple studies would be necessary to establish a complete database.

Evidence of a pelvis-driven flexion pattern: are the joints of the lower lumbar spine fully flexed in seated postures?

BACKGROUND

Seated postures are achieved with a moderate amount of lumbo-sacral flexion and sustained lumbo-sacral spine flexion has been associated with detrimental effects to the tissues surrounding a spinal joint. The purpose of this study was to determine if the lower intervertebral joints of the lumbo-sacral spine approach their end ranges of motion in seated postures.

METHODS

Static sagittal digital X-ray images of the lumbo-sacral region from L3 to the top of the sacrum were obtained in five standing and seated postures from 27 participants. Vertebral body bony landmarks were manually digitized and intervertebral joint angles were calculated for the three lower lumbo-sacral joints.

FINDINGS

In upright sitting, the L5/S1 intervertebral joint was flexed to more than 60% of its total range of motion. Each of the lower three intervertebral joints approached their total flexion angles in the slouched sitting posture. These observations were the same regardless of gender. The results support the idea that lumbo-sacral flexion is driven by rotation of the pelvis and lower intervertebral joints in seated postures.

INTERPRETATION

This is the first study to quantitatively show that the lower lumbo-sacral joints approach their total range of motion in seated postures. While not directly measured, the findings suggest that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting.

Clinical application of a handy intraoperative measurement device for lumbar segmental instability

We describe the development of a new device that permits handy intraoperative measurement of lumbar segmental instability. The subjects comprised 80 patients with lumbar degenerative disease. Relationships between preoperative radiological assessments and extended distance as measured using our new device were investigated. Mean extended distance measured using the device was 3.7 +/- 1.9 mm. Correlation coefficients between angular motion and extended distance, and translational motion and extended distance were 0.76 and 0.66, respectively, revealing significant positive relationships between these values (p < 0.01 each). The correlation coefficient between the intervertebral endplate angle on the flexion film and extended distance was -0.78, showing a significant negative relationship (p < 0.01). In conclusion, the device for intraoperative measurement of lumbar segmental instability that we have developed appears to permit simple measurement of intervertebral instability and provides operators with valuable information for selecting operative methods of spinal fusion or instrumentation.

Biomechanical evaluation of segmental instability in degenerative lumbar spondylolisthesis

Here we investigated the biomechanical properties of spinal segments in patients with degenerative lumbar spondylolisthesis (DLS) using a novel intraoperative measurement system. The measurement system comprised spinous process holders, a motion generator, a load cell, an optical displacement transducer, and a computer. Cyclic displacement of the holders produced flexion-extension of the segment with all ligamentous structures intact. Stiffness, absorption energy (AE), and neutral zone (NZ) were determined from the load-deformation data. Forty-one patients with DLS (M/F = 15/26, mean age 68.6 years; Group D) were studied. Adjacent segments with normal discs in six patients (M/F = 3/3, mean age 35 years) were included as a control group (Group N). Flexion stiffness was significantly lower in Group D than in Group N. The NZ, however, was significantly greater in Group D than in Group N. Thus, compared to normal segments, spinal segments with DLS had a lower flexion stiffness and a higher NZ. NZs in Group D were, however, widely distributed compared to those in Group N that showed NZ <2 mm/N in all cases, suggesting that the segment with DLS is not always unstable and that the segments with NZ >2 mm/N can be considered as unstable.

A technique to measure three-dimensional in vivo rotation of fused and adjacent lumbar vertebrae

BACKGROUND CONTEXT

Previous attempts to measure vertebral motion in vivo have been either static measure, imprecise, two-dimensional, or overly invasive to be applied to serial studies.

PURPOSE

This study evaluated the efficacy of a unique high-speed biplane X-ray system for tracking lumbar vertebrae in vivo during dynamic motion. Additional goals were to determine parameters for future studies using this tool and to obtain preliminary data on the effects of lumbar fusion on vertebral kinematics.

STUDY DESIGN/SETTING

A high-speed biplane radiographic X-ray system was used to measure the three-dimensional (3D) relative rotation between fused and adjacent vertebrae in vivo during muscle driven movement. Subjects were tested 2, 3, and 6 months after fusion procedures to assess vertebral motion of fused and adjacent vertebrae.

PATIENT SAMPLE

Five subjects received lumbar fusion surgery.

OUTCOME MEASURES

Physiologic measures included 3D vertebral rotation of fused and adjacent vertebrae.

METHODS

Tantalum beads were implanted into lumbar vertebrae during fusion operations. Radiographic data was collected continuously at 50 frames per second during flexion-extension, lateral bending, and axial twist movements serially, at 2, 3, and 6 months after fusion surgery.

RESULTS

Implanted beads were tracked with an accuracy of 0.18 mm during dynamic motion. Vertebral rotation was not necessarily linearly related to trunk rotation, supporting the use of continuous data collection during movement; collecting only movement start and end points may not be sufficient. Some movements indicated fusion was complete, whereas others indicated incomplete fusion. This suggests patients be tested performing a variety of movements to test for complete fusion. The fusion site often acted as a pivot point for vertebral rotation, with vertebrae superior to the fusion rotating in the direction of the trunk and vertebrae inferior rotating opposite trunk rotation.

CONCLUSIONS

This technique is sufficiently accurate for in vivo serial studies of vertebral motion during muscle driven movements. A variety of movements should be performed to assess surgical results, and the data should be collected continuously through the entire range of motion, not just at the movement endpoints. However, care must be exercised in subject selection, in camera location, and in the placement of tracking beads in relation to implanted instrumentation.

Parametric characterization of spinal motions in osteoporotic vertebral fracture at level T12 with fluoroscopy

Vertebral fractures due to osteoporosis are a common skeletal disorder affecting the mobility of the patients, although little is known about the relationship between spinal kinematics and osteoporotic fracture. The purpose of this study was to characterize the motions of the thoracolumbar spine affected by osteoporotic vertebral fracture at level T12 and compare the results with those of non-fracture osteoporosis subjects. We examined the continuous segmental kinematics of the vertebrae, and describe the segmental motion of the spine when a fracture at T12 is present. Fluoroscopy sequences of the thoracolumbar spines during sagittal and lateral flexion were collected from 16 subjects with osteoporosis of their spine (6 with vertebral fractures at T12, 10 without a fracture). Vertebrae T10-L2 in each frame of the sequences were landmarked. Kinematic parameters were calculated based on the landmarks and motion graphs were constructed. Compared to the control subjects who did not have a fracture, fracture subjects had a more asymmetric lateral range of motion (RoM) and required a longer time to complete certain phases of the motion cycle which are parameterized as lateral flexion ratio and percentage of motion cycle, respectively. Prolonged deflection was more frequently found from the fracture group. Characterizing the motions of the fractured vertebra together with its neighboring vertebrae with these kinematic parameters is useful in quantifying the dysfunction and may be a valuable aid to tracking progress of treatment.

Evaluation of lumbar segmental instability in degenerative diseases by using a new intraoperative measurement system

Object

In vivo quantitative measurement of lumbar segmental stability has not been established. The authors developed a new measurement system to determine intraoperative lumbar stability. The objective of this study was to clarify the biomechanical properties of degenerative lumbar segments by using the new method.

Methods

Twenty-two patients with a degenerative symptomatic segment were studied and their measurements compared with those obtained in normal or asymptomatic degenerative segments (Normal group). The measurement system produces cyclic flexion–extension through spinous process holders by using a computer-controlled motion generator with all ligamentous structures intact. The following biomechanical parameters were determined: stiffness, absorption energy (AE), and neutral zone (NZ). Discs with degeneration were divided into 2 groups based on magnetic resonance imaging grading: degeneration without collapse (Collapse[−]) and degeneration with collapse (Collapse[+]). Biomechanical parameters were compared among the groups. Relationships among the biomechanical parameters and age, diagnosis, or radiographic parameters were analyzed.

Results

The mean stiffness value in the Normal group was significantly greater than that in Collapse(−) or Collapse(+) group. There was no significant difference in the average AE value among the Normal, Collapse(−), and Collapse(+) groups. The NZ in the Collapse(−) was significantly higher than in the Normal or Collapse(+) groups. Stiffness was negatively and NZ was positively correlated with age. Stiffness demonstrated a significant negative and NZ a significant positive relationship with disc height, however.

Conclusions

There were no significant differences in stiffness between spines in the Collapse(−) and Collapse(+) groups. The values of a more sensitive parameter, NZ, were higher in Collapse(−) than in Collapse(+) groups, demonstrating that degenerative segments with preserved disc height have a latent instability compared to segments with collapsed discs.

Stress in lumbar intervertebral discs during distraction: a cadaveric study

BACKGROUND CONTEXT

The intervertebral disc is a common source of low back pain (LBP). Prospective studies suggest that treatments that intermittently distract the disc might be beneficial for chronic LBP. Although the potential exists for distraction therapies to affect the disc biomechanically, their effect on intradiscal stress is debated.

PURPOSE

To determine if distraction alone, distraction combined with flexion, or distraction combined with extension can reduce nucleus pulposus pressure and posterior annulus compressive stress in cadaveric lumbar discs compared with simulated standing or lying.

STUDY DESIGN

Laboratory study using single cadaveric motion segments.

OUTCOME MEASURES

Strain gauge measures of nucleus pulposus pressure and compressive stress in the anterior and posterior annulus fibrosus.

METHODS

Intradiscal stress profilometry was performed on 15 motion segments during 5 simulated conditions: standing, lying, and 3 distracted conditions. Disc degeneration was graded by inspection from 1 (normal) to 4 (severe degeneration).

RESULTS

All distraction conditions markedly reduced nucleus pressure compared with either simulated standing or lying. There was no difference between distraction with flexion and distraction with extension in regard to posterior annulus compressive stress. Discs with little or no degeneration appeared to distribute compressive stress differently than those with moderate or severe degeneration.

CONCLUSIONS

Distraction appears to predictably reduce nucleus pulposus pressure. The effect of distraction therapy on the distribution of compressive stress may be dependent in part on the health of the disc.

The feasibility of a video-based motion analysis system in measuring the segmental movements between upper and lower cervical spine

The evaluation of the range of motion (ROM) and static posture in the cervical spine are important in physical examination. Despite offering dynamic assessment without radiation, the video-based motion analysis system has not yet been applied to measure the cervical segmental movements. The purposes of this study were to develop a neck model to differentiate the movements and posture between upper and lower cervical spine, and to examine the reliability of measuring cervical motion with surface markers and the aid of videofluoroscopy. Sixteen healthy adult subjects (eight males and eight females) participated in this study. Ten surface markers were used to estimate the discrepancies in cervical vertebral angles compared with corresponding bony landmarks throughout the ROM. The average intraclass correlation coefficients (ICCs) of the paired vertebral angles between surface markers and bony landmarks ranged from 0.844 to 0.975 and the mean absolute difference (MAD) averaged 2.96 degrees. Our results indicate high consistency between surface markers and bony landmarks throughout the cervical movements. The mean upper (C0-C2) and lower (C2-C7) cervical joint angles in the neutral position were 18.59+/-4.33 degrees and 23.98+/-6.15 degrees, respectively. Furthermore, the reliability of the digitizing procedure within raters (ICC=0.850-0.999; MAD=0.58-2.42 degrees) and between raters (ICC=0.759-0.988; MAD=0.59-2.66 degrees) suggests that the neck motion analysis model is a feasible method for investigating static neck posture or dynamic motion between upper and lower cervical spine.

The quantitative measurements of the intervertebral angulation and translation during cervical flexion and extension

The insufficient exploration of intervertebral translation during flexion and extension prevents the further understanding of the cervical biomechanics and treating the cervical related dysfunction. The objective of this study was to quantitatively measure the continuous intervertebral translation of healthy cervical spine during flexion and extension by videofluoroscopic technique. A total of 1,120 image sequences were analyzed for 56 healthy adult subjects by a precise image protocol during cervical flexion and extension. O: ur results showed there were no statistical angular differences among five spinal levels in either flexion or extension, except for the comparison between C2/3 (13.5 degrees) and C4/5 (22.6 degrees) angles. During cervical flexion, the smallest anterior translations were 0.7 mm at C2/3 level, followed by 0.9 mm at C6/7, 1.0 mm at C3/4, 1.1 mm at C5/6, and the largest 1.2 mm at C4/5 levels. The significantly greater translations were measured in the posterior direction at C3/4 (1.1 mm, P = 0.037), C4/5 (1.3 mm, P = 0.039), and C5/6 (1.2 mm, P = 0.005) levels than in the anterior one. The relatively fluctuant and small average posterior translation fashion at C6/7 level (0.4 mm) possibly originated from the variations in the direction of translation during cervical extension among subjects. Normalization with respect to the widths of individual vertebrae showed the total translation percentages relative to the adjacent vertebrae were 9.5, 13.7, 16.6, 15.0, and 8.6% for C2/3 to C6/7 levels, respectively, and appeared to be within the clinical-accepted ranges of translation in cervical spine. The intervertebral translations of cervical spine during flexion and extension movements were first described in quality and quantity based on the validated radiographic protocol. This analysis of the continuous intervertebral translations may be further employed to diagnose translation abnormalities like hypomobility or hypermobility and to monitor the treatment effect on cervical spines.

Fluoroscopic video to identify aberrant lumbar motion

STUDY DESIGN

A prospective, case-control design.

OBJECTIVES

To develop a kinematic model that characterizes frequently observed movement patterns in patients with low back pain (LBP).

SUMMARY OF BACKGROUND DATA

Understanding arthrokinematics of lumbar motion in those with LBP may provide further understanding of this condition.

METHODS

Digital fluoroscopic video (DFV) was used to quantify the magnitude and rate of attainment of sagittal plane intersegmental angular and linear displacement from 20 individuals with LBP and 20 healthy control subjects during lumbar flexion and extension. Three fellowship-trained spine surgeons subsequently qualitatively analyzed the DFVs to determine normality of movement. Final classification was based on agreement between their symptom and motion status (11 with LBP and aberrant motion and 14 healthy controls without aberrant motion). Independent t tests, receiver operator characteristic curves, and accuracy statistics were calculated to determine the most parsimonious set of kinematic variables able to distinguish patients with LBP.

RESULTS

Eight kinematic variables had a positive likelihood ratio > or = 2.5 and entered the model. Six of the variables described a disruption in the rate of attainment of angular or linear displacement during midrange postures. When 4 or more of these variables were present, the positive likelihood ratio was 14.0 (confidence interval 3.2-78.5), resulting in accurately identifying 96% of participants.

CONCLUSIONS

DFV was useful for discriminating between individuals with and without LBP based on kinematic parameters. Disruptions in how the motion occurred during midrange motions were more diagnostic for LBP than range of motion variables. Cross validation of the model is required.

Arthrokinematics in a subgroup of patients likely to benefit from a lumbar stabilization exercise program

BACKGROUND AND PURPOSE

A clinical prediction rule (CPR) has been reported to identify patients with low back pain who are likely to benefit from stabilization exercises. The aim of this study was to characterize the spinal motion, using digital fluoroscopic video, of a subgroup of subjects with low back pain.

SUBJECTS

Twenty subjects who were positive on the CPR were compared with 20 control subjects who were healthy.

METHODS

The magnitude and timing of lumbar sagittal-plane intersegmental angular and linear displacement were assessed. Receiver operating characteristic curves and accuracy statistics were used to develop a kinematic model.

RESULTS

A 10-variable model was developed that could distinguish group membership. Seven of these variables described a disruption in timing of angular or linear displacement during mid-range movements. None of the variables suggested hypermobility.

DISCUSSION AND CONCLUSION

The findings suggest that individuals with mid-range aberrant motion without signs of hypermobility are likely to benefit from these exercises. The developed model describes altered kinematics of this subgroup of subjects and helps to provide construct validity for the developed CPR.

Evaluation of lumbar spine motion with dynamic X-ray--a reliability analysis

STUDY DESIGN

Radiologic evaluation of lumbar range of motion (ROM) with dynamic radiograph.

OBJECTIVES

To calculate 95% confidence intervals (CIs) for the measurement error accompanying different methods, different observers, and different levels of training when measuring sagittal plane segmental ROM in lumbar spine. In addition, to compare the 95% CI with frequently common statistical methods of reliability analysis.

SUMMARY OF BACKGROUND DATA

Dynamic radiographs are commonly used for ROM calculation of the lumbar spine. Yet, the reliability of different measurement methods still remains unclear.

METHODS

In 24 patients, levels L4-L5 and L5-S1 were measured with the Cobb and superimposition methods on flexion-extension radiographs. There were 2 experienced and 1 inexperienced observer that performed the measurements. The 95% CIs were compared with the corresponding Pearson correlation coefficient and P value (t test).

RESULTS

The 95% CI of the superimposition method was +/-4.0 degrees for the experienced and +/-4.7 degrees for the inexperienced observer. The corresponding values for the Cobb method was +/-4.2 degrees for the experienced and +/-6.8 degrees for the inexperienced observer. The 95% CI for the measurement error became even worse when different methods or observers were compared, whereas a method constancy revealed superior reliability than observer constancy in experienced observers.

CONCLUSIONS

For lumbar ROM measurement with dynamic radiograph, the superimposition method seems to be more reliable than the Cobb method. Study protocols dealing with ROM measurement have to calculate the 95% CI of the measurement method used because clinically valid conclusions can only be drawn with respect to these intervals.