MRI evaluation of lumbar spine flexion and extension in asymptomatic individuals

Assessing the Preservation of Lumbar Lordotic Curvature in Everyday Sitting Conditions Assessed with an Inertial Measurement System

Background/Objectives: Lumbar lordotic curvature (LLC), closely associated with low back pain (LBP) when decreased, is infrequently assessed in clinical settings due to the spatiotemporal limitations of radiographic methods. To overcome these constraints, this study used an inertial measurement system to compare the magnitude and maintenance of LLC across various sitting conditions, categorized into three aspects: verbal instructions, chair type, and desk task types. Methods: Twenty-nine healthy participants were instructed to sit for 3 min with two wireless sensors placed on the 12th thoracic vertebra and the 2nd sacral vertebra. The lumbar lordotic angle (LLA) was measured using relative angles for the mediolateral axis and comparisons were made within each sitting category. Results: The maintenance of LLA (LLAdev) was significantly smaller when participants were instructed to sit upright (-3.7 ± 3.9°) compared to that of their habitual sitting posture (-1.2 ± 2.4°) (p = 0.001), while the magnitude of LLA (LLAavg) was significantly larger with an upright sitting posture (p = 0.001). LLAdev was significantly larger when using an office chair (-0.4 ± 1.1°) than when using a stool (-3.2 ± 7.1°) (p = 0.033), and LLAavg was also significantly larger with the office chair (p < 0.001). Among the desk tasks, LLAavg was largest during keyboard tasks (p < 0.001), followed by mouse and writing tasks; LLAdev showed a similar trend without statistical significance (keyboard, -1.2 ± 3.0°; mouse, -1.8 ± 2.2°; writing, -2.9 ± 3.1°) (p = 0.067). Conclusions: Our findings suggest that strategies including the use of an office chair and preference for computer work may help preserve LLC, whereas in the case of cueing, repetition may be necessary.

Long-term effects of lumbar flexion versus extension exercises for chronic axial low back pain: a randomized controlled trial

This study aimed to compare the long-term effects of flexion- and extension-based lumbar exercises on chronic axial low back pain (LBP). This was a 1-year follow-up of a prospective, assessor-blind, randomized controlled trial. Patients with axial LBP (intensity ≥ 5/10) for > 6 months allocated to the flexion or extension exercise group. Patients underwent four sessions of a supervised treatment program and were required to perform their assigned exercises daily at home. Clinical outcomes were obtained at baseline, 1, 3, 6 months, and 1-year. A total of 56 patients (age, 54.3 years) were included, with 27 and 29 in the flexion and extension groups, respectively. Baseline pain and functional scales were similar between both groups. The mean (± standard deviation) baseline average back pain was 6.00 ± 1.00 and 5.83 ± 1.20 in the flexion and extension groups, respectively. At 1-year, the average pain was 3.78 ± 1.40 and 2.26 ± 2.62 (mean between-group difference, 1.52; 95% confidence interval 0.56-2.47; p = 0.002), favoring extension exercise. The extension group tended to have more improvements in current pain, least pain, and pain interference than the flexion group at 1-year. However, there was no group difference in worst pain and functional scales. In this controlled trial involving patients with chronic axial LBP, extension-based lumbar exercise was more effective in reducing pain than flexion-based exercises at 1-year, advocating lumbar extension movement pattern as a component for therapeutic exercise for chronic LBP.Clinical Trial Registration No.: NCT02938689 (Registered on www.clinicaltrial.gov ; first registration date was 19/10/2016).

A novel tool to quantify in vivo lumbar spine kinematics and 3D intervertebral disc strains using clinical MRI

Medical imaging modalities that calculate tissue morphology alone cannot provide direct information regarding the mechanical behaviour of load-bearing musculoskeletal organs. Accurate in vivo measurement of spine kinematics and intervertebral disc (IVD) strains can provide important information regarding the mechanical behaviour of the spine, help to investigate the effects of injuries on the mechanics of the spine, and assess the effectiveness of treatments. Additionally, strains can serve as a functional biomechanical marker for detecting normal and pathologic tissues. We hypothesised that combining digital volume correlation (DVC) with 3T clinical MRI can provide direct information regarding the mechanics of the spine. Here, we have developed a novel non-invasive tool for in vivo displacement and strain measurement within the human lumbar spine and we used this tool to calculate lumbar kinematics and IVD strains in six healthy subjects during lumbar extension. The proposed tool enabled spine kinematics and IVD strains to be measured with errors that did not exceed 0.17 mm and 0.5%, respectively. The findings of the kinematics study identified that during extension the lumbar spine of healthy subjects experiences total 3D translations ranging from 1 mm to 4.5 mm for different vertebral levels. The findings of strain analysis identified that the average of the maximum tensile, compressive, and shear strains for different lumbar levels during extension ranged from 3.5% to 7.2%. This tool can provide base-line data that can be used to describe the mechanical environment of healthy lumbar spine, which can help clinicians manage preventative treatments, define patient-specific treatments, and to monitor the effectiveness of surgical and non-surgical interventions.

Ossification and Fusion of the Vertebral Ring Apophysis as an Important Part of Spinal Maturation

In scoliosis, most of the deformity is in the disc and occurs during the period of rapid growth. The ring apophyses form the insertion of the disc into the vertebral body, they then ossify and fuse to the vertebrae during that same crucial period. Although this must have important implications for the mechanical properties of the spine, relatively little is known of how this process takes place. This study describes the maturation pattern of the ring apophyses in the thoracic and lumbar spine during normal growth. High-resolution CT scans of the spine for indications not related to this study were included. Ossification and fusion of each ring apophysis from T1 to the sacrum was classified on midsagittal and midcoronal images (4 points per ring) by two observers. The ring apophysis maturation (RAM) was compared between different ages, sexes, and spinal levels. The RAM strongly correlated with age (R = 0.892, p < 0.001). Maturation differed in different regions of the spine and between sexes. High thoracic and low lumbar levels fused earlier in both groups, but, around the peak of the growth spurt, in girls the mid-thoracic levels were less mature than in boys, which may have implications for the development of scoliosis.

Imaging features of the aging spine

Among many degenerative abnormalities commonly found in spine imaging, not all are associated with the patient's symptoms. We aimed to assess features of the standard, asymptomatic aging process of the spine. In this narrative review, we emphasize studies that describe imaging features of the spine in asymptomatic populations of different age groups. Degeneration of the intervertebral discs, bulging, and facet joint arthropathy have been documented in almost 90% of asymptomatic patients over 60 years of age. After the age of 40 years, nearly all patients have anterior and lateral vertebral osteophytes, whereas posterior osteophytes are found in a minority of them. There is a gradual increase in vertebral bone marrow fat composition with age with the acceleration of this process in women after menopause. The prevalence of these findings is common in asymptomatic populations and varies depending on the patient's age. It is essential to differentiate likely natural and age-related findings from pathological abnormalities to make an accurate diagnosis.

The acute response of the nucleus pulposus of the cervical intervertebral disc to three supine postures in an asymptomatic population

BACKGROUND

The dynamic disc model refers to the ability of a spinal disc's position to be manipulated by body postures and movements. Research on lumbar discs has indicated movement of the anterior and posterior disc that correlates with posture of the spine. The aim of this study was to assess whether, despite its structural differences, the cervical disc responds to flexed and extended postures in a similar fashion to the lumbar disc.

METHOD

A repeated measures study. Twenty five asymptomatic participants (age: 33.7 ± 9.1 years) volunteered. Scans were performed in supine using an Esaote 0.2T magnetic resonance imaging scanner. Participants lay with their cervical spine initially placed in neutral, followed by flexion and finally extension. The position of the posterior disc nucleus pulposus at C5-6 and C6-7 was measured against a vertical line connecting the posterior vertebral bodies above and below each disc.

RESULTS

Changes in cervical spine position were associated with significant changes in posterior disc nucleus pulposus position at both C5-6 and C6-7 (p < 0.01 for both). Post hoc testing showed a significant difference in posterior disc nucleus pulposus position at C5-6 between flexion and extension (p = 0.02). There was similarly a significant change at C6-7 between neutral and flexion (p = 0.001), and between flexion and extension (p = 0.02).

CONCLUSIONS

These results indicate that the cervical posterior nucleus pulposus is affected by spinal loading, consistent with the concept of the dynamic disc model.

Reliability and validity of lumbar disc height quantification methods using magnetic resonance images

Disc height has been a focus of research on disc degeneration and low back pain (LBP). However, choosing an appropriate method to quantify disc height remains controversial. The aim of the present study was to determine the reliability and construct validity of disc height quantification methods. Repeated semi-automatic measurements of L4-5 and L5-S1 discs were obtained from 43 T2-weighted mid-sagittal 3T magnetic resonance (MR) images of 22 subjects with LBP (43±13 years), blinded to prior measurements. Heights were calculated with area-based methods (using 60%, 80% and 100% of the disc width), and point-based methods (Hurxthal's, Dabbs' and combining the two). Intra-class correlation coefficients (ICC) and standard error of measurement (SEM) were estimated. Construct validity was assessed using correlation coefficients. Intra-rater ICC(3,1) of the area-based disc height measurements ranged from 0.84 to 0.99 with an inter-rater ICC(2,1) of 0.99. Measurements with point-based methods had lower intra- and inter-rater reliability ranging between 0.76 and 0.96 and between 0.84 and 0.98, respectively. Inter-rater SEM varied between 0.2 and 0.3 mm for area-based methods and between 0.3 and 0.7 mm for point-based methods. Excluding Dabbs', high correlations (r>0.9) were observed between methods. Area-based height measurements using partial disc width demonstrated excellent reliability and construct validity and outperformed point-based methods.

Lumbar spine angles and intervertebral disc characteristics with end-range positions in three planes of motion in healthy people using upright MRI

Understanding changes in lumbar spine (LS) angles and intervertebral disc (IVD) behavior in end-range positions in healthy subjects can provide a basis for developing more specific LS models and comparing people with spine pathology. The purposes of this study are to quantify 3D LS angles and changes in IVD characteristics with end-range positions in 3 planes of motion using upright MRI in healthy people, and to determine which intervertebral segments contribute most in each plane of movement. Thirteen people (average age = 24.4 years, range 18-51 years; 9 females; BMI = 22.4 ± 1.8 kg/m²) with no history of low back pain were scanned in an upright MRI in standing, sitting flexion, sitting axial rotation (left, right), prone on elbows, prone extension, and standing lateral bending (left, right). Global and local intervertebral LS angles were measured. Anterior-posterior length of the IVD and location of the nucleus pulposus was measured. For the sagittal plane, lower LS segments contribute most to change in position, and the location of the nucleus pulposus migrated from a more posterior position in sitting flexion to a more anterior position in end-range extension. For lateral bending, the upper LS contributes most to end-range positions. Small degrees of intervertebral rotation (1-2°) across all levels were observed for axial plane positions. There were no systematic changes in IVD characteristics for axial or coronal plane positions.

Increased lumbar spinal column laxity due to low-angle, low-load cyclic flexion may predispose to acute injury

Lumbar spinal column laxity contributes to instability, increasing the risk of low back injury and pain. Until the laxity increase due to the cyclic loads of daily living can be quantified, the associated injury risk cannot be predicted clinically. This work cyclically loaded 5-vertebra lumbar motion segments (7 skeletally-mature cervine specimens, 5 osteoporotic human cadaver specimens) for 20 000 cycles of low-load low-angle (15°) flexion. The normalized neutral zone lengths and slopes of the load-displacement hysteresis loops showed a similar increase in spinal column laxity across species. The intervertebral kinematics also changes with cyclic loading. Differences in the location and magnitude of surface strain on the vertebral bodies (0.34% ± 0.11% in the cervine specimens, and 3.13% ± 1.69% in the human cadaver specimens) are consistent with expected fracture modes in these populations. Together, these results provide biomechanical evidence of spinal column damage during high-cycle low-load low-angle loading.

The segment-dependent changes in lumbar intervertebral space height during flexion-extension motion

Objectives

Many studies have investigated the kinematics of the lumbar spine and the morphological features of the lumbar discs. However, the segment-dependent immediate changes of the lumbar intervertebral space height during flexion-extension motion are still unclear. This study examined the changes of intervertebral space height during flexion-extension motion of lumbar specimens.

Methods

First, we validated the accuracy and repeatability of a custom-made mechanical loading equipment set-up. Eight lumbar specimens underwent CT scanning in flexion, neural, and extension positions by using the equipment set-up. The changes in the disc height and distance between adjacent two pedicle screw entry points (DASEP) of the posterior approach at different lumbar levels (L3/4, L4/5 and L5/S1) were examined on three-dimensional lumbar models, which were reconstructed from the CT images.

Results

All the vertebral motion segments (L3/4, L4/5 and L5/S1) had greater changes in disc height and DASEP from neutral to flexion than from neutral to extension. The change in anterior disc height gradually increased from upper to lower levels, from neutral to flexion. The changes in anterior and posterior disc heights were similar at the L4/5 level from neutral to extension, but the changes in anterior disc height were significantly greater than those in posterior disc height at the L3/4 and L5/S1 levels, from neutral to extension.

Conclusions

The lumbar motion segment showed level-specific changes in disc height and DASEP. The data may be helpful in understanding the physiologic dynamic characteristics of the lumbar spine and in optimising the parameters of lumbar surgical instruments.

Cite this article: M. Fu, Q. Ye, C. Jiang, L. Qian, D. Xu, Y. Wang, P. Sun, J. Ouyang. The segment-dependent changes in lumbar intervertebral space height during flexion-extension motion. Bone Joint Res 2017;6:245–252. DOI: 10.1302/2046-3758.64.BJR-2016-0245.R1.

Effects of Cervical Extension on Deformation of Intervertebral Disk and Migration of Nucleus Pulposus

BACKGROUND

We theorized that active cervical extension should influence the position of the nucleus pulposus (NP) within the intervertebral disk (IVD) in the sagittal plane. Although several studies on the lumbar IVD have been conducted, there are no quantitative data for in vivo positional changes of the NP in the cervical IVD.

OBJECTIVE

To evaluate the influence and mechanism of cervical extension on the deformation and migration of IVD and NP in the sagittal plane and understand underlying mechanisms of the extension maneuver.

DESIGN

Asymptomatic subjects underwent magnetic resonance imaging while supine with their cervical spines in neutral and extended positions.

SETTING

Academic medical center.

PARTICIPANTS

Ten young, healthy male participants (age range 19-30 years; mean 22.4 ± 1.64 years).

METHODS

T2-weighted sagittal images from C3-C4 to C6-C7 of subjects in both neutral and extension positions were analyzed.

MAIN OUTCOME MEASUREMENTS

Deformation of IVD and positional change of NP were quantified and compared between neutral and extension positions. Intersegmental angles between vertebrae, horizontal positions of anterior and posterior IVD and NP margins, IVD outer and inner heights, and sagittal morphology of NP were quantified and compared between the neutral and extension positions. Correlations between the measured parameters and segmental extension angle were also investigated.

RESULTS

Anterior and posterior IVD margins moved posteriorly with respect to the vertebral body in extension. Both NP margins remained unchanged relative to the vertebral body but moved anteriorly with respect to the IVD. IVD outer and inner heights in the anterior region increased in extension, and morphological changes of the NP were less noticeable when compared with its relative migration within the IVD. Most of the intradiskal changes were linearly correlated with the segmental extension angle.

CONCLUSIONS

Cervical extension induces anterior migration of the NP away from the posterior disk margin and may have a clinical effect on diskogenic neck pain resulting from internal disk disruption.

LEVEL OF EVIDENCE

Not applicable.

MRI Findings of Disc Degeneration are More Prevalent in Adults with Low Back Pain than in Asymptomatic Controls: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

Imaging features of spine degeneration are common in symptomatic and asymptomatic individuals. We compared the prevalence of MR imaging features of lumbar spine degeneration in adults 50 years of age and younger with and without self-reported low back pain.

MATERIALS AND METHODS

We performed a meta-analysis of studies reporting the prevalence of degenerative lumbar spine MR imaging findings in asymptomatic and symptomatic adults 50 years of age or younger. Symptomatic individuals had axial low back pain with or without radicular symptoms. Two reviewers evaluated each article for the following outcomes: disc bulge, disc degeneration, disc extrusion, disc protrusion, annular fissures, Modic 1 changes, any Modic changes, central canal stenosis, spondylolisthesis, and spondylolysis. The meta-analysis was performed by using a random-effects model.

RESULTS

An initial search yielded 280 unique studies. Fourteen (5.0%) met the inclusion criteria (3097 individuals; 1193, 38.6%, asymptomatic; 1904, 61.4%, symptomatic). Imaging findings with a higher prevalence in symptomatic individuals 50 years of age or younger included disc bulge (OR, 7.54; 95% CI, 1.28-44.56; P = .03), spondylolysis (OR, 5.06; 95% CI, 1.65-15.53; P < .01), disc extrusion (OR, 4.38; 95% CI, 1.98-9.68; P < .01), Modic 1 changes (OR, 4.01; 95% CI, 1.10-14.55; P = .04), disc protrusion (OR, 2.65; 95% CI, 1.52-4.62; P < .01), and disc degeneration (OR, 2.24; 95% CI, 1.21-4.15, P = .01). Imaging findings not associated with low back pain included any Modic change (OR, 1.62; 95% CI, 0.48-5.41, P = .43), central canal stenosis (OR, 20.58; 95% CI, 0.05-798.77; P = .32), high-intensity zone (OR = 2.10; 95% CI, 0.73-6.02; P = .17), annular fissures (OR = 1.79; 95% CI, 0.97-3.31; P = .06), and spondylolisthesis (OR = 1.59; 95% CI, 0.78-3.24; P = .20).

CONCLUSIONS

Meta-analysis demonstrates that MR imaging evidence of disc bulge, degeneration, extrusion, protrusion, Modic 1 changes, and spondylolysis are more prevalent in adults 50 years of age or younger with back pain compared with asymptomatic individuals.

Comparable effect of simulated side bending and side gliding positions on the direction and magnitude of lumbar disc hydration shift: in vivo MRI mechanistic study

OBJECTIVES

To investigate the direction and magnitude of mechanical influence to the lumbar disc in side bending and side gliding positions by considering shift of disc hydration.

METHODS

Twenty asymptomatic subjects completed this study. Direction of the hydration shift (θ), magnitude of the shift, and segmental lateral flexion and rotation angles from L1/L2 to L5/S1 during left side bend and side glide in lying were measured by magnetic resonance imaging (MRI) and compared using paired t-tests.

RESULTS

A significant difference (P<0.001) was detected in the segmental lateral flexion angle at L1/L2 between the side bending position (mean [SD], 5.1° [2.2°] left lateral flexion) and the side gliding position (mean [SD], 2.1° [2.7°] left lateral flexion). However, there was neither significant difference (P>0.05) in the lateral flexion angle at other segments nor rotation angles at each segment between the two lumbar positions. There was also no significant difference (P>0.05) in the θ value and magnitude of the hydration shift between the two lumbar positions. The disc hydration generally shifted to the right in the left side bending and side gliding positions at all disc levels.

DISCUSSION

This is the first study to investigate mechanical influence to each lumbar disc in the side gliding position using the shift of disc hydration on axial MRI. The comparability in the direction and magnitude of the hydration shift in the side bending and side gliding positions indicates that the maneuver of side gliding can produce comparable ipsilateral mechanical influence to each lumbar disc in comparison to side bending.

In vivo morphological features of human lumbar discs

Recent biomechanics studies have revealed distinct kinematic behavior of different lumbar segments. The mechanisms behind these segment-specific biomechanical features are unknown. This study investigated the in vivo geometric characteristics of human lumbar intervertebral discs. Magnetic resonance images of the lumbar spine of 41 young Chinese individuals were acquired. Disc geometry in the sagittal plane was measured for each subject, including the dimensions of the discs, nucleus pulposus (NP), and annulus fibrosus (AF). Segmental lordosis was also measured using the Cobb method.In general, the disc length increased from upper to lower lumbar levels, except that the L4/5 and L5/S1 discs had similar lengths. The L4/5 NP had a height of 8.6±1.3 mm, which was significantly higher than all other levels (P<0.05). The L5/S1 NP had a length of 21.6±3.1 mm, which was significantly longer than all other levels (P<0.05). At L4/5, the NP occupied 64.0% of the disc length, which was significantly less than the NP of the L5/S1 segment (72.4%) (P<0.05). The anterior AF occupied 20.5% of the L4/5 disc length, which was significantly greater than that of the posterior AF (15.6%) (P<0.05). At the L5/S1 segment, the anterior and posterior AFs were similar in length (14.1% and 13.6% of the disc, respectively). The height to length (H/L) ratio of the L4/5 NP was 0.45±0.06, which was significantly greater than all other segments (P<0.05). There was no correlation between the NP H/L ratio and lordosis. Although the lengths of the lower lumbar discs were similar, the geometry of the AF and NP showed segment-dependent properties. These data may provide insight into the understanding of segment-specific biomechanics in the lower lumbar spine. The data could also provide baseline knowledge for the development of segment-specific surgical treatments of lumbar diseases.

Systematic literature review of imaging features of spinal degeneration in asymptomatic populations

BACKGROUND AND PURPOSE

Degenerative changes are commonly found in spine imaging but often occur in pain-free individuals as well as those with back pain. We sought to estimate the prevalence, by age, of common degenerative spine conditions by performing a systematic review studying the prevalence of spine degeneration on imaging in asymptomatic individuals.

MATERIALS AND METHODS

We performed a systematic review of articles reporting the prevalence of imaging findings (CT or MR imaging) in asymptomatic individuals from published English literature through April 2014. Two reviewers evaluated each manuscript. We selected age groupings by decade (20, 30, 40, 50, 60, 70, 80 years), determining age-specific prevalence estimates. For each imaging finding, we fit a generalized linear mixed-effects model for the age-specific prevalence estimate clustering in the study, adjusting for the midpoint of the reported age interval.

RESULTS

Thirty-three articles reporting imaging findings for 3110 asymptomatic individuals met our study inclusion criteria. The prevalence of disk degeneration in asymptomatic individuals increased from 37% of 20-year-old individuals to 96% of 80-year-old individuals. Disk bulge prevalence increased from 30% of those 20 years of age to 84% of those 80 years of age. Disk protrusion prevalence increased from 29% of those 20 years of age to 43% of those 80 years of age. The prevalence of annular fissure increased from 19% of those 20 years of age to 29% of those 80 years of age.

CONCLUSIONS

Imaging findings of spine degeneration are present in high proportions of asymptomatic individuals, increasing with age. Many imaging-based degenerative features are likely part of normal aging and unassociated with pain. These imaging findings must be interpreted in the context of the patient's clinical condition.

Nucleus pulposus deformation in response to rotation at L1-2 and L4-5

BACKGROUND

Spinal rotation couples with lateral flexion as a composite movement. Few data report the in vivo mechanical deformation of the nucleus pulposus following sustained rotation. MRI provides a non-invasive method of examining nucleus pulposus deformation by mapping the hydration signal distribution within the intervertebral disc.

METHODS

T1 weighted coronal and sagittal lumbar images and T2 weighted axial images at L1-2 and L4-5 were obtained from 10 asymptomatic subjects (mean age 29, range: 24-34 years) in sustained flexed and extended positions plus combined positions of left rotation with flexion and extension. Nucleus pulposus deformation was tracked by mapping the change in hydration profiles from coronal and sagittal pixel measurements.

FINDINGS

An average sagittal change in position of 44° (SD 14.5°) from flexion to extension was recorded between L1 and S1 (range: 18°- 60°) resulting in a mean anterior nucleus pulposus deformation of 16% of disc hydration profile (range: 3.5%-19%) in 19/20 discs. When rotation was combined with either flexion or extension, mean coronal deformation was 4.8% (SD-5.1%; range: 0.4%-15%). Lateral nucleus pulposus deformation direction varied in rotation (44% deformed left and 56% deformed right). Intersegmental lateral flexion direction more strongly predicted nucleus pulposus deformation direction with 75% deforming contralaterally.

INTERPRETATION

Nucleus pulposus deformation direction in young subjects was more predictable following sagittal position change than in rotation combined with flexion or extension. Deformation magnitude was reduced in rotated positions. Intersegmental lateral flexion was a stronger predictor of nucleus pulposus deformation direction.

Ionizing radiation exposure and the development of intervertebral disc degeneration--no case to answer

In the following perspective article, Mellor and Breen provide a counterpoint to a previous perspective on the potential link between ionizing radiation exposure and intervertebral disc degeneration in humans [1]. The previous perspective asked, is this link a myth or reality? It suggested the potential for such a link. Mellor and Breen offer a drastically alternate view, in essence, that the question itself is flawed. To support their perspective, they explain the different units of radiation measurement and their conversion to risk in humans and how this impacts the previous perspective. They explain the variable sensitivity of different body tissues to radiation and highlight that neither human research nor any of the multiple international regulatory agencies have ever suggested that the intervertebral disc is sensitive to radiation. Finally, they claim that it is impossible to predict with any certainty the effects of low-level radiation on the intervertebral discs.

Intervertebral disc changes after 1 h of running: a study on athletes

The lumbar spines of 25 long-distance runners were examined using an upright magnetic resonance imaging scanner. All volunteer runners were scanned before and after running for 1 h. Scanning was performed with the runners seated upright (neutral), leaning forwards (flexion) and leaning backwards (extension). All measured discs showed a reduction in disc height after 1 h of running. A significant reduction in disc height was observed in all three body positions (neutral, flexion and extension) after 1 h of running. The results showed that, in flexion, extension and neutral positions, intervertebral discs undergo significant strain after 1 h of running. The lowest disc-height reduction was found at the L5 - S1 space in the neutral position; the same space had the highest percentage of disc degeneration.

Vertebral bodies or discs: which contributes more to human-like lumbar lordosis?

BACKGROUND

The attainment of upright posture, with its requisite lumbar lordosis, was a major turning point in human evolution. Nonhuman primates have small lordosis angles, whereas the human spine exhibits distinct lumbar lordosis (30 degrees -80 degrees ). We assume the lumbar spine of the pronograde ancestors of modern humans was like those of extant nonhuman primates, but which spinal components changed in the transition from small lordosis angles to large ones is not fully understood.

QUESTIONS/PURPOSES

We wished to determine the relative contribution of vertebral bodies and intervertebral discs to lordosis angles in extant primates and humans.

METHODS

We measured the lordosis, intervertebral disc, and vertebral body angles of 100 modern humans (orthograde primates) and 56 macaques (pronograde primates) on lateral radiographs of the lumbar spine (humans-standing, macaques-side-lying).

RESULTS

The humans exhibited larger lordosis angles (51 degrees ) and vertebral body wedging (5 degrees ) than did the macaques (15 degrees and -25 degrees , respectively). The differences in wedging of the intervertebral discs, however, were much less pronounced (46 degrees versus 40 degrees ).

CONCLUSIONS

These observations suggest the transition from pronograde to orthograde posture (ie, the lordosis angle) resulted mainly from an increase in vertebral body wedging and only in small part from the increase in wedging of the intervertebral discs.

Nucleus pulposus deformation in response to lumbar spine lateral flexion: an in vivo MRI investigation

Whilst there are numerous studies examining aspects of sagittal plane motion in the lumbar spine, few consider coronal plane range of motion and there are no in vivo reports of nucleus pulposus (NP) displacement in lateral flexion. This study quantified in vivo NP deformation in response to side flexion in healthy volunteers. Concomitant lateral flexion and axial rotation range were also examined to evaluate the direction and extent of NP deformation. Axial T2- and coronal T1-weighted magnetic resonance images (MRI) were obtained from 21 subjects (mean age, 24.8 years) from L1 to S1 in the neutral and left laterally flexed position. Images were evaluated for intersegmental ranges of lateral flexion and axial rotation. A novel methodology derived linear pixel samples across the width of the disc from T2 images, from which the magnitude and direction of displacement of the NP was determined. This profiling technique represented the relative hydration pattern within the disc. The NP was displaced away from the direction of lateral flexion in 95/105 discs (p < 0.001). The extent of NP displacement was associated strongly with lateral flexion at L2-3 (p < 0.01). The greatest range of lateral flexion occurred at L2-3, L3-4 and L4-5. Small intersegmental ranges of axial rotation occurred at all levels, but were not associated with NP displacement. The direction of NP deformation was highly predictable in laterally flexed healthy lumbar spines; however, the magnitude of displacement was not consistent with the degree of intersegmental lateral flexion or rotation.

Radiographic parameters of segmental instability in lumbar spine using kinetic MRI

OBJECTIVE

To investigate the effectiveness of radiographic parameters on segmental instability in the lumbar spine using Kinetic magnetic resonance imaging (MRI).

METHODS

Segmental motion, defined as excessive (more than 3 mm) translational motion from flexion to extension, was investigated in 309 subjects (927 segments) using Kinetic MRI. Radiographic parameters which can help indicate segmental instability include disc degeneration (DD), facet joint osteoarthritis (FJO), and ligament flavum hypertrophy (LFH). These three radiographic parameters were simultaneously evaluated, and the combinations corresponding to significant segmental instability at each level were determined.

RESULTS

The overall incidence of segmental instability was 10.5% at L3-L4, 16.5% at L4-L5, and 7.3% at L5-S1. DD and LFH at L3-L4 and FJO and LFH at L4-L5 were individually associated with segmental instability (p<0.05). At L4-L5, the following combinations had a higher incidence of segmental instability (p<0.05) when compared to other segments : (1) Grade IV DD with grade 3 FJO, (2) Grade 2 or 3 FJO with the presence of LFH, and (3) Grade IV DD with the presence of LFH. At L5-S1, the group with Grade III disc and Grade 3 FJO had a higher incidence of segmental instability than the group with Grade I or II DD and Grade 1 FJO.

CONCLUSION

This study showed that the presences of either Grade IV DD or grade 3 FJO with LFH at L4-L5 were good indicators for segmental instability. Therefore, using these parameters simultaneously in patients with segmental instability would be useful for determining candidacy for surgical treatment.

Architectural analysis and intraoperative measurements demonstrate the unique design of the multifidus muscle for lumbar spine stability

BACKGROUND

Muscular instability is an important risk factor for lumbar spine injury and chronic low-back pain. Although the lumbar multifidus muscle is considered an important paraspinal muscle, its design features are not completely understood. The purpose of the present study was to determine the architectural properties, in vivo sarcomere length operating range, and passive mechanical properties of the human multifidus muscle. We hypothesized that its architecture would be characterized by short fibers and a large physiological cross-sectional area and that it would operate over a relatively wide range of sarcomere lengths but would have very stiff passive material properties.

METHODS

The lumbar spines of eight cadaver specimens were excised en bloc from T12 to the sacrum. Multifidus muscles were isolated from each vertebral level, permitting the architectural measurements of mass, sarcomere length, normalized fiber length, physiological cross-sectional area, and fiber length-to-muscle length ratio. To determine the sarcomere length operating range of the muscle, sarcomere lengths were measured from intraoperative biopsy specimens that were obtained with the spine in the flexed and extended positions. The material properties of single muscle fibers were obtained from passive stress-strain tests of excised biopsy specimens.

RESULTS

The average muscle mass (and standard error) was 146 +/- 8.7 g, and the average sarcomere length was 2.27 +/- 0.06 microm, yielding an average normalized fiber length of 5.66 +/- 0.65 cm, an average physiological cross-sectional area of 23.9 +/- 3.0 cm(2), and an average fiber length-to-muscle length ratio of 0.21 +/- 0.03. Intraoperative sarcomere length measurements revealed that the muscle operates from 1.98 +/- 0.15 microm in extension to 2.70 +/- 0.11 microm in flexion. Passive mechanical data suggested that the material properties of the muscle are comparable with those of muscles of the arm or leg.

CONCLUSIONS

The architectural design (a high cross-sectional area and a low fiber length-to-muscle length ratio) demonstrates that the multifidus muscle is uniquely designed as a stabilizer to produce large forces. Furthermore, multifidus sarcomeres are positioned on the ascending portion of the length-tension curve, allowing the muscle to become stronger as the spine assumes a forward-leaning posture.

The response of the nucleus pulposus of the lumbar intervertebral discs to functionally loaded positions

STUDY DESIGN

Asymptomatic volunteers underwent magnetic resonance imaging to investigate how different positions affect lumbar intervertebral discs.

OBJECTIVE

To quantify sagittal migration of the lumbar nucleus pulposus in 6 functional positions.

SUMMARY OF BACKGROUND DATA

Previous studies of the intervertebral disc response in the sagittal plane were limited to imaging of recumbent positions. Developments of upright magnetic resonance imaging permit investigation of functional weight-bearing positions.

METHODS

T2-weighted sagittal scans of the L1-L2 to L5-S1 discs were taken of 11 volunteers in standing, sitting (upright, flexed, and in extension), supine, and prone extension. Sagittal migration of the nucleus pulposus was measured (mm) as distance from anterior disc boundary to peak pixel intensity. Lumbar lordosis (Cobb angle) was measured in each position.

RESULTS

Fifteen comparisons between positions showed significant positional effects (14 at L4-L5, L5-S1, the most mobile segments). Prone extension and supine lying induced significantly less posterior migration than sitting. Flexed and upright sitting, significantly more than standing at L4-L5, as did flexed sitting compared with extended.

CONCLUSION

These results support for the first time the validity of clinical assumptions about disc behavior in functional positions: sitting postures may increase risk of posterior derangement, and prone and supine may be therapeutic for symptoms caused by posterior disc displacement.

Positional MRI changes in supine versus sitting postures in patients with degenerative lumbar spine

INTRODUCTION

Back pain is associated with a degree of alteration in the alignment and movement of the lumbar spine. The purpose of this study is to investigate how the degree of lumbar segmental degeneration affects sagittal changes in the lumbar spine as it shifts from the supine to the sitting (load-bearing) posture.

MATERIALS AND METHODS

Thirty patients with chronic low back pain were enrolled (14 male and 16 female patients); mean age 44.5 years. Their lumbar spines were initially investigated by conventional supine magnetic resonance imaging (MRI) followed later by positional MRI in the seated posture. Of the 150 discs studied, 87 were classified as healthy grade 1, 16 as grade 2, 34 as grade 3, and 13 as grade 4.

RESULTS

As the lumbar spine was loaded from the supine to the sitting position, the end-plate angles were decreased significantly as the degeneration was increased. There were also significant changes in the anterior and middle disc heights between the supine and the sitting postures irrespective of the degree of degeneration. The overall lumbar lordosis did not significantly change between the two postures.

CONCLUSIONS

We have found that the changes in the segmental motion were related to the degree of degeneration. With positional MRI, we were able to demonstrate changes in healthy and degenerative discs in the weight-bearing position. More similar studies are needed to understand the complex kinematics of the lumbar spine.

The effect of lumbar flexion and extension on disc contour abnormality measured quantitatively on magnetic resonance imaging

STUDY DESIGN

Experimental study with subjects as their own control.

OBJECTIVE

To determine if lumbar disc contour abnormality dimensions, measured quantitatively, differ in flexed, neutral or extended positions.

SUMMARY OF BACKGROUND DATA

MRIs obtained lying supine are used to determine the degree of lumbar disc contour abnormality (bulging or herniation). Variations in positioning are suspected to influence this assessment.

METHODS

Lumbar MR images for 26 male volunteers (24-74 years of age), with or without low back pain, were obtained with the subjects lying in neutral, maximal flexion, and maximal extension positions allowable within a conventional 1.5T MR scanner. Quantitative measures of anterior and posterior disc contour abnormality were obtained for each position.

RESULTS

Statistically significant differences in disc angles were obtained between positions (2-5 degrees) for all levels. Posterior contour abnormality was significantly smaller in flexion and extension than in the neutral position (9.5%-30.1%). Posterior contour abnormality in extension was similar or smaller than in flexion. Anterior contour abnormality was significantly smaller in extension than flexion and smaller in the neutral position than flexion.

CONCLUSION

Spine position should be standardized when assessing disc contour abnormality with MRI. The largest measured disc contour abnormalities when lying supine in a standard MR scanner are observed in the neutral position, as opposed to flexion or extension.

Effects of X-STOP device on sagittal lumbar spine kinematics in spinal stenosis

The X-Stop device is designed to distract the posterior elements of the stenotic segment and place it in flexion to treat neurogenic claudication. Previous biomechanical studies on X Stop have been done in vitro on cadavers looking at disc pressures and segmental range of movements. The objective of this study is to understand the sagittal kinematics in vivo of the lumbar spine at the instrumented and adjacent levels. Twenty-six patients with lumbar spine stenosis underwent 1 or 2 level X-Stop procedure. All had pre- and postoperative positional magnetic resonance imaging (MRI) in standing, supine, and sitting in flexion and extension. Measurements of disc heights, endplate angles, segmental and lumbar range of movement were performed after placement of X Stop at the stenosed level in patients with lumbar spinal stenosis. No significant changes were seen in disc heights, segmental and total lumbar spine movements postoperatively. The X-Stop device does not affect the sagittal kinematics of the lumbar spine in vivo.

Mechanical Diagnosis and Therapy approach to assessment and treatment of derangement of the sacro-iliac joint

This case report describes the clinical reasoning and management of the sacroiliac joint, utilising the McKenzie Method of Mechanical Diagnosis and Therapy (MDT). A patient with a 2 year history of buttock and thigh pain demonstrates a directional preference for repeated anterior SIJ rotation. The MDT approach is discussed and is an ideal method for emphasising the patients involvement in managing their own back problem.

An MRI investigation of intervertebral disc deformation in response to torsion

BACKGROUND

The nucleus pulposus deforms towards an area of least compression in response to offset loading, however, there is a lack of data reporting the deformation patterns of nuclear material in rotated positions of the lumbar spine. Our purpose was to assess a novel methodology using MRI to track nuclear deformation in response to flexion and extension positions, and the combined positions of flexion with left rotation and extension with left rotation, at L1-2 and L4-5.

METHODS

Three asymptomatic female subjects, mean age 27 years, underwent T2 weighted MRI sequences in flexed, extended, and left rotated positions combined with flexion and extension. A pixel profile technique was employed to determine direction and magnitude of nuclear deformation.

RESULTS

In 5 of 6 discs examined, deformation of the nucleus occurred anteriorly in extension and posteriorly in flexion. Left rotation resulted in migration of nuclear material to the right in 9 of 12 discs. Of the three discs that demonstrated a right nuclear migration, two occurred at L4-5 and one at L1-2.

INTERPRETATION

This methodology demonstrated that nucleus pulposus deformation can be measured reliably in various positions achieved within the confines of the MRI. The consistent migration of nuclear material following sagittal plane movement and the less consistent response to rotation positions suggest other asymmetrical loading on the intervertebral disc may accompany rotation.

The flexion-extension profile of lumbar spine in 100 healthy volunteers

STUDY DESIGN

Dynamic lumbar flexion-extension motions were assessed by an electrogoniometer and a videofluoroscopy unit simultaneously.

OBJECTIVES

The aims of this study were to assess the motion profile of lumbar spine in different genders and age groups and to assess their differences. SUMMARY OF BACKGROUNDS DATA: The dynamic lumbar flexion-extension motions analysis method has been developed and validated. However, data profile of the spinal motions of healthy volunteers has not been established. METHODS.: A total of 100 healthy volunteers, including 50 men and 50 women, were recruited. They were then divided into four equal groups, following their age ranges of 21 to 30 years, 31 to 40 years, 41 to 50 years, and 51 years and older. Lumbar flexion-extension motion was assessed with an electrogoniometer and videofluoroscopy simultaneously. Radiologic images of the lumbar spine were captured during flexion-extension in 10 degrees intervals. Intervertebral flexion-extension (IVFE) of each vertebral level was calculated. The spinal motion of different genders was compared segment by segment with independent t test. The spinal motion of different age groups was compared with one-way analysis of variance.

RESULTS

A linear-liked pattern of the IVFE curves was observed in different genders and age groups. No statistically significant difference in the pattern of motion was found between genders. However, statistically significant difference in the slope of IVFE curves was found at all lumbar levels in subjects whose age was 51 years or older (P < 0.05).

CONCLUSIONS

Assessment of motion profile was found to be helpful for the identification of spinal disorders in clinical practice. Because of the normal variation of spinal motion of subjects in different age ranges, interpretation of spinal motion disorders should be careful. Although the sample size in this study was limited, the database generated might be useful to assist the diagnosis of spinal "instability" in the future.