Effects of standing on lumbar spine alignment and intervertebral disc geometry in young, healthy individuals determined by positional magnetic resonance imaging

Upright versus recumbent lumbar spine MRI: Do findings differ systematically, and which correlates better with pain? A systematic review

BACKGROUND CONTEXT

Recumbent MRI is the most widely used image modality in people with low back pain (LBP), however, it has been proposed that upright (standing) MRI has advantages over recumbent MRI because of its ability to assess the effects of being weight-bearing. It has been suggested that this produces systematic differences in MRI parameters and differences in the correlation between MRI parameters and pain or disability in patients thus, potentially adding clinically helpful information.

PURPOSE

This paper aims to review and summarize the available empirical evidence for or against these two hypotheses.

STUDY DESIGN/SETTING

Systematic review of the literature (PROSPERO ID: CRD42017048318). Studies should be based on paired observations of MRI findings in the upright and recumbent positions. Studies needed a minimum of 15 participants.

PATIENT/PARTICIPANT SAMPLE

People aged 18 or older with or without low back pain ± radiculopathy OUTCOME MEASURES: All continuous, ordinal, and dichotomous parameters based on MRI images. All measures of pain or disability.

METHODS

Studies assessing MRI parameters both in upright and recumbent positions on the same individuals measured on continuous, ordinal, or dichotomous scales were included. For each parameter, the expected direction of the difference between recumbent and upright position was specified as an increase, no change, or decrease. Information on the observed distribution of individual differences was extracted from included studies and subjected to meta-analyses if sufficient data was available. Observed differences were then compared with the prespecified expectations. Studies were also screened for information on correlations between patients' pain and/or disability and MRI parameters or differences between patient subgroups defined by patients' pain and/or disability.

RESULTS

19 studies were identified, including 5.082 participants with LBP (16 studies) and 166 participants without low back pain (5 studies). Twenty-five MRI parameters were measured on a continuous scale, ten parameters were assessed on an ordinal scale, and 15 parameters were reported as dichotomous data. The observed differences between recumbent and upright MRI were mostly consistent with the prespecified expectations. Correlations between patients' pain or disability level and MRI parameters were reported in only one study, and three studies reported comparisons of MRI parameters across subgroups of patients defined by pain or disability characteristics. Higher correlations or larger effect sizes when using the upright position were observed in most results reported.

CONCLUSION

For most MRI parameters, the direction of the observed difference between assessment in recumbent and upright positions aligned with the pre-specified expectation implied by the weight-bearing position. This confirms the existence of a systematic difference between the two positions. Performing an MRI upright instead of recumbent position may increase the correlation with pain, but final evidence for this property is still missing. The clinical significance of upright MRI is still unclear, and there is a need to directly investigate the impact of MRI findings on clinical decision-making and patient outcomes.

Impact of posture and axial loading on lumbar intervertebral disc dimensions investigated by transabdominal ultrasound

PURPOSE

To use transabdominal ultrasound (US) to investigate the impact of posture and axial loading on the lumbar intervertebral disc (IVD) dimensions in healthy adults.

METHOD

For this single-center, prospective cross-sectional study 54 healthy volunteers (mean age 23.76 ± 3, 26 men) underwent transabdominal US. Lumbar IVD dimensions (height, length, width) at the levels L3/4 and L4/5 were assessed in three test conditions: supine, standing, and standing position with additional axial load of 50 % body weight (standing+50%). Success rates for the longitudinal and transverse US acquisitions and IVD dimension measurements were determined. IVD dimensions were compared across test conditions using two-way repeated measures analysis of variance and post-hoc pairwise t-tests with Bonferroni correction.

RESULTS

The success rate for longitudinal and transverse US acquisition was 100 %. The overall success rate for IVD dimension measurement was 96.4 %, it was highest for IVD height (99.2 %) and lowest for IVD length (93.3 %). IVD height at L4/5 decreased significantly from the supine to standing position (p < 0.05) and from the supine to standing+50% position (p < 0.01). IVD width at L3/4 increased significantly from the supine to standing+50% position (p < 0.05). No significant differences were found for IVD length.

CONCLUSIONS

Transabdominal US is a feasible tool to investigate IVD dimensions at L3/4 and L4/5 in different postures and with axial loading. Posture and axial loading significantly influence IVD height and width, but not length.

Geodesic Logistic Analysis of Lumbar Spine Intervertebral Disc Shapes in Supine and Standing Positions

Non-specific lower back pain (LBP) is a world-wide public health problem that affects people of all ages. Despite the high prevalence of non-specific LBP and the associated economic burdens, the pathoanatomical mechanisms for the development and course of the condition remain unclear. While intervertebral disc degeneration (IDD) is associated with LBP, there is overlapping occurrence of IDD in symptomatic and asymptomatic individuals, suggesting that degeneration alone cannot identify LBP populations. Previous work has been done trying to relate linear measurements of compression obtained from Magnetic Resonance Imaging (MRI) to pain unsuccessfully. To bridge this gap, we propose to use advanced non-Euclidean statistical shape analysis methods to develop biomarkers that can help identify symptomatic and asymptomatic adults who might be susceptible to standing-induced LBP. We scanned 4 male and 7 female participants who exhibited lower back pain after prolonged standing using an Open Upright MRI. Supine and standing MRIs were obtained for each participant. Patients reported their pain intensity every fifteen minutes within a period of 2 h. Using our proposed geodesic logistic regression, we related the structure of their lower spine to pain and computed a regression model that can delineate lower spine structures using reported pain intensities. These results indicate the feasibility of identifying individuals who may suffer from lower back pain solely based on their spinal anatomy. Our proposed spinal shape analysis methodology have the potential to provide powerful information to the clinicians so they can make better treatment decisions.

Changes in intervertebral sagittal alignment of the cervical spine from supine to upright

Cervical sagittal alignment is a critical component of successful surgical outcomes. Unrecognized differences in intervertebral alignment between supine and upright positions may affect clinical outcomes; however, these differences have not been quantified. Sixty-four patients scheduled to undergo one or two-level cervical arthrodesis for symptomatic pathology from C4-C5 to C6-C7, and forty-seven controls were recruited. Upright sagittal alignment was obtained through biplane radiographic imaging and measured using a validated process with accuracy better than 1° in rotation. Supine alignment was obtained from computed tomography scans. Coordinate systems used to measure supine and upright alignment were identical. Distances between adjacent bony endplates were measured to calculate disc height in each position. For both patients and controls, the C1-C2, C2-C3, and C3-C4 motion segments were in more lordosis when upright as compared with supine (all p < 0.001). However, the C4-C5, C5-C6, and C6-C7 motion segments were in less lordosis when upright as compared with supine (all p ≤ 0.004). There was an interaction between group and position at the C1-C2 (p = 0.002) and C2-C3 (p = 0.001) motion segments, with the controls demonstrating a greater increase in lordosis at both motion segments when moving from supine to upright. The results indicate that cervical motion segment alignment changes between supine and upright positioning, those changes differ among motion segments, and cervical pathology affects the magnitude of these changes. Clinical Significance: Surgeons should be mindful of the differences in alignment between supine and upright imaging and the implications they may have on clinical outcomes.

Lumbar intervertebral disc diurnal deformations and T2 and T1rho relaxation times vary by spinal level and disc region

PURPOSE

Magnetic resonance imaging (MRI) is routinely used to evaluate spine pathology; however, standard imaging findings weakly correlate to low back pain. Abnormal disc mechanical function is implicated as a cause of back pain but is not assessed using standard clinical MRI. Our objective was to utilize our established MRI protocol for measuring disc function to quantify disc mechanical function in a healthy cohort.

METHODS

We recruited young, asymptomatic volunteers (6 male/6 female; age 18-30 years; BMI < 30) and used MRI to determine how diurnal deformations in disc height, volume, and perimeter were affected by spinal level, disc region, MRI biomarkers of disc health (T2, T1rho), and Pfirrmann grade.

RESULTS

Lumbar discs deformed by a mean of -6.1% (95% CI: -7.6%, -4.7%) to -8.0% (CI: -10.6%, -5.4%) in height and -5.4% (CI: -7.6%, -3.3%) to -8.5% (CI: -11.0%, -6.0%) in volume from AM to PM across spinal levels. Regional deformations were more uniform in cranial lumbar levels and concentrated posteriorly in the caudal levels, reaching a maximum of 13.1% at L5-S1 (CI:-16.1%, -10.2%). T2 and T1rho relaxation times were greatest in the nucleus and varied circumferentially within the annulus. T2 relaxation times were greatest at the most cranial spinal levels and decreased caudally. In this young healthy cohort, we identified a weak association between nucleus T2 and the diurnal change in the perimeter.

CONCLUSIONS

Spinal level is a key factor in determining regional disc deformations. Interestingly, deformations were concentrated in the posterior regions of caudal discs where disc herniation is most prevalent.

Axial loading during supine MRI for improved assessment of lumbar spine: comparison with standing MRI

BACKGROUND

There are no studies comparing the morphologic changes of lumbar spines between supine axial-loaded and 90° standing magnetic resonance imaging (MRI) examinations of patients with spinal stenosis.

PURPOSE

To determine whether axial-loaded MRI using a compression device demonstrated similar morphology of intervertebral disc, dural sac, and spinal curvature as those detected by 90° standing MRI in individuals with suspected spinal stenosis.

MATERIAL AND METHODS

A total of 54 individuals suspected of having spinal stenosis underwent both axial-loaded and standing MRI studies. The outcome measures included seven radiologic parameters of the lumbar spine: measures of the intervertebral disc (i.e. cross-sectional area [DA], disc height [DH], and anteroposterior distance [DAP]), dural sac (cross-sectional area [DCSA]), spinal curvature (i.e. lumbar lordosis [LL] and L1-L3-L5 angle [LA]), and total lumbar spine height (LH).

RESULTS

For agreement between the two methods, intraclass correlation coefficient (ICC) ≥ 0.8 was found for all seven radiologic parameters. Supine axial-loaded MRI underestimated LL but remained correlated (ICC = 0.83) with standing MRI. Minor differences between the two methods (≤5.0%) were observed in DA, DCSA, DAP, LA, and LH, while a major difference was observed in LL (8.1%).

CONCLUSION

Using a compression device with the conventional supine MRI to simulate weight-bearing on the lumbar spine generated MRI morphology, which was strongly correlated with those from a standing MRI.

In vivo relationships between lumbar facet joint and intervertebral disc composition and diurnal deformation

BACKGROUND

Spinal motion is facilitated by a "three joint complex", two facet joints and one intervertebral disc at each spinal level. Both the intervertebral discs and facet joints are subject to natural age-related degeneration, and while these processes may be linked it is not clear how. As instability in the disc could underlie facet arthritis, we evaluated the hypothesis that the discs and facet joints are mechanically coupled.

METHODS

We recruited young, asymptomatic volunteers (n = 10; age: mean 25, range 21-30 years; BMI: mean 23.1, range 19.1-29.0 kg/m²) and applied magnetic resonance imaging (MRI) and three-dimensional (3D) modeling to measure facet and disc composition (MRI T1rho relaxation time) and facet and disc function (diurnal changes in facet space width, disc height) in the lumbar spine.

FINDINGS

We found that facet space width was positively associated with facet T1rho relaxation time (fluid content) and negatively associated with disc T1rho, and that facets adjacent to degenerated discs were significantly thicker and had significantly higher T1rho. Furthermore, the diurnal change in wedge angle was positively associated the diurnal change in facet space width, while disc degeneration, the diurnal change in disc height, and facet T1rho were not.

INTERPRETATION

These data demonstrate an interdependence between disc and facet health, but not between disc and facet mechanical function. Furthermore, the weak relationship between facet cartilage composition and in vivo function suggests that other factors, like spinal curvature, determine in vivo spine mechanics. Future work in symptomatic or aged populations are warranted to confirm these findings.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Please be upstanding - A narrative review of evidence comparing upright to supine lumbar spine MRI

OBJECTIVES

The objective of the review was to examine the evidence comparing upright to supine MRI of the lumbar spine.

KEY FINDINGS

A literature search identified 14 articles comparing data where subjects had been scanned in both supine and upright positions on the same scanner. Lumbar spine anatomy is dynamic and therefore subject to morphological changes when transitioning from the supine to the upright position. There is strong evidence to suggest structural changes in spinal morphology due to radiographic positioning, and that upright positioning is better for evaluating spondylolisthesis.

CONCLUSION

It has been demonstrated that the scanning position is important in the outcome of the MRI examination of the lumbar spine. With this in mind, it would be beneficial for guidance to be written and adopted to improve the consistency and quality of scanning.

IMPLICATIONS FOR PRACTICE

As upright MRI occupies a niche in the scanning sector, many professionals are unaware of its capabilities. This article aims to increase awareness of the use of upright MRI in evaluating the lumbar spine.