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

Aberrant intervertebral motion in patients with treatment‑resistant nonspecific low back pain: a retrospective cohort study and control comparison

Purpose Intervertebral kinematic assessments have been used to investigate mechanical causes when back pain is resistant to treatment, and recent studies have identified intervertebral motion markers that discriminate patients from controls. However, such patients are a heterogeneous group, some of whom have structural disruption, but the effects of this on intervertebral kinematics are unknown.Methods Thirty-seven patients with treatment-resistant back pain referred for quantitative fluoroscopy were matched to an equal number of pain-free controls for age and sex. All received passive recumbent flexion assessments for intervertebral motion sharing inequality (MSI), variability (MSV), laxity and translation. Comparisons were made between patient sub-groups, between patients and controls and against normative levels from a separate group of controls.Results Eleven patients had had surgical or interventional procedures, and ten had spondylolisthesis or pars defects. Sixteen had no disruption. Patients had significantly higher median MSI values (0.30) than controls (0.27, p = 0.010), but not MSV (patients 0.08 vs controls 0.08, p = 0.791). Patients who received invasive procedures had higher median MSI values (0.37) than those with bony defects (0.30, p = 0.018) or no disruption (0.28, p = 0.0007). Laxity and translation above reference limits were not more prevalent in patients.Conclusion Patients with treatment-resistant nonspecific back pain have greater MSI values than controls, especially if the former have received spinal surgery. However, excessive laxity, translation and MSV are not more prevalent in these patients. Thus, MSI should be investigated as a pain mechanism and for its possible value as a prognostic factor and/or target for treatment in larger patient populations

Dynamic interactions between lumbar intervertebral motion segments during forward bending and return

Continuous dynamic multi-segmental studies of lumbar motion have added depth to our understanding of the biomechanics of back pain, but few have attempted to continuously measure the proportions of motion accepted by individual levels. This study attempted to compare the motion contributions of adjacent lumbar levels during an active weight bearing flexion and return protocol in chronic, non-specific low back pain (CNSLBP) patients and controls using quantitative fluoroscopy (QF). Eight CNSLBP patients received QF during guided standing lumbar flexion. Dynamic motion sharing of segments from L2 to S1 were calculated and analysed for interactions between levels. Eight asymptomatic controls were then matched to the 8 patients for age and sex and their motion sharing patterns compared. Share of intersegmental motion was found to be consistently highest at L2-L3 and L3- L4 and lowest at L5-S1 throughout the motion in both groups, with the exception of maximum flexion where L4-L5 received the greatest share. Change in motion sharing occurred throughout the flexion and return motion paths in both participant groups but tended to vary more at L4-L5 in patients (p<0.05). In patients, L5-S1 provided less angular range (p<0.05) and contributed less at maximum bend (p<0.05), while L3-L4, on average over the bending sequence, provided a greater share of motion (p<0.05). Intervertebral motion sharing inequality is therefore a normal feature during lumbar flexion. However, in patients, inequality was more pronounced, and variability of motion share at some levels increased. These effects may result from differences in muscular contraction or in the mechanical properties of the disc

A reference database of standardised continuous lumbar intervertebral motion analysis for conducting patient-specific comparisons.

Introduction: To understand spinal disorders in terms of their biomechanical effects on symptoms and evaluate treatment effects, biomechanical variables must be repeatable over an acceptable follow-up period in a symptomatically stable population. In previous work using quantitative fluoroscopy (QF), where both the motion task (lumbar flexion) and the analysis were highly standardised, some intervertebral motion sharing characteristics in the lumbar spine were found to be significantly different in NSLBP patients and asymptomatic controls (1). Control measurements were also stable over 6 weeks, making measures suitable for use in outcome and prognostic studies (2). Previous studies have found it advantageous to study the outward and return paths of lumbar flexion separately in order to appreciate the differences in dynamic loading models during bending and lifting tasks (3). Against such normative data, individual patient studies using the same protocols can be compared. The aim of this study was to establish a database of reference values for key dynamic lumbar motion variables during controlled outward and return bending using standardised QF recording and analysis protocols. These could serve as reference information for both the construction of mathematical models and for comparison with patient-specific kinematics. Methods: Low dose continuous fluoroscopic image sequences, recorded at 15 fps, were acquired from 131 asymptomatic participants during active, weight-bearing lumbar flexion and return motion. This used a bending protocol guided by an upright motion frame (Fig 1). This standardised the bending range and velocity and minimized accessory movements. Continuous intervertebral rotations in the sagittal plane were extracted for each level (L2-S1) in each frame and transformed into contributions proportional to the total L2-S1 angle. Mean and ± 95% confidence intervals across all participants were calculated for each 1% increment of L2–S1 motion. Data were separated to distinguish the flexion and return-to-neutral portions of the bending task. Statistically significant differences between each level’s contribution to motion were detected by the absence of overlap in the ±CI95 bands and checked using statistical parametric mapping. Results: Full data sets were extracted from 127 participants, (48.8% female, mean age 38.6 years, range: 21-70). The proportion of the motion performed by each level at full flexion was similar to previous studies (4). However, there were significant differences in the contributions to bending during motion, both between and within levels, which change as participants progress through the tasks (Figures 2a and b). Across the study population, each intervertebral level also had its own characteristic motion signature, with significant differences (p<0.05) between each level’s contribution. These were sustained throughout the motion. In the individual back pain patient example (Fig 2c), L2-3 initially accepted a higher proportion of the outward motion than that of the controls (Fig 2a), and considerably less at L4-5, although both showed return to near-normal sharing levels by completion of the bend. On the return motion (Fig 2d), it is L4-5 that initially accepts a higher proportion in this patient, and L3-4 considerably less, although by the time the upright position has been reached and all but L4-5’s share of the motion resemble the normative values (Fig 2b). Figure 1. Upright motion controller Figure 2. Proportional contributions to motion from L2-S1 with 95% CIs in 127 healthy controls in a) flexion, b) return and comparison with a patient with chronic, non-specific low back pain c) and d). Controls (n=127) Outward Return Figure 2a Figure 2b Patient (n=1) Figure 2c Figure 2d Discussion: In the controls (Fig 2a and b), despite differences in gender, BMI, age, anatomy, co-ordination and strength, all levels exhibited consistent motion contributions. This was attributed to the use of the guided motion apparatus (Fig 1) making the database also suitable for comparison with both cross-sectional and longitudinal data from individuals and with groups of patients with low back pain in research and clinical studies. The patient (Fig 2c), exhibits much more initial flexion at L3-4 than the controls during forward bending, while L4-5’s motion is initially paradoxical. On return, L4-5 initially accepts much more of the motion and L2-3 much less (Fig 2d). These differences are likely to be related to a combination of loading, motor control and tissue material characteristics. They may also be suitable for modelling dynamic segmental loading in clinical and occupational settings. References 1. Breen A, et al. Eur Spine J. 27:145-153, 2017 2. Breen A, et al. Eur Spine J. 28:450–460 2019. 3. Aiyangar A, et al. J Biomech. 48:3709-3715, 2015. 4. Widmer, J., et al. A of Biomed. Eng., 47:1491-1522, 2019

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

Accuracy and repeatability of quantitative fluoroscopy for the measurement of sagittal plane translation and finite centre of rotation in the lumbar spine

Quantitative fluoroscopy (QF) was developed to measure intervertebral mechanics in vivo and has been found to have high repeatability and accuracy for the measurement of intervertebral rotations. However, sagittal plane translation and finite centre of rotation (FCR) are potential measures of stability but have not yet been fully validated for current QF. This study investigated the repeatability and accuracy of QF for measuring these variables. Repeatability was assessed from L2-S1 in 20 human volunteers. Accuracy was investigated using 10 consecutive measurements from each of two pairs of linked and instrumented dry human vertebrae as reference; one which tilted without translation and one which translated without tilt. The results found intra- and inter-observer repeatability for translation to be 1.1mm or less (SEM) with fair to substantial reliability (ICC 0.533-0.998). Intra-observer repeatability of FCR location for inter-vertebral rotations of 5o and above ranged from 1.5mm to 1.8mm (SEM) with moderate to substantial reliability (ICC 0.626-0.988). Inter-observer repeatability for FCR ranged from 1.2mm to 5.7mm, also with moderate to substantial reliability (ICC 0.621-0.878). Reliability was substantial (ICC>0.81) for 10/16 measures for translation and 5/8 for FCR location. Accuracy for translation was 0.1mm (fixed centre) and 2.2mm (moveable centre), with an FCR error of 0.3mm(x) and 0.4mm(y) (fixed centre). This technology was found to have a high level of accuracy and with a few exceptions, moderate to substantial repeatability for the measurement of translation and FCR from fluoroscopic motion sequences

A quantitative fluoroscopic study of the relationship between lumbar inter-vertebral and residual limb/socket kinematics in the coronal plane in adult male unilateral amputees. (Exploring the spine and lower limb kinematics of trans-tibial amputees).

Introduction Much of lower back pain (LBP) is thought to be mechanical in origin and lower limb amputees have an increased prevalence. There is also evidence that a large proportion of them also have altered spinal posture and it is commonly thought that the movement between the vertebrae (kinematics) may be affected. The current study was designed to explore the kinematics of the lumbar spine segments in trans-tibial amputees and compare it to a similar population with intact lower limbs using quantitative fluoroscopy (QF). The study also investigated possible relationships between lumbar spine stability and the motion between the prosthetic socket and residual limb. It is hoped that these investigations will improve understanding of the importance of limb-socket fit to the functional integrity of the lumbar spine in lower limb amputees Methods A literature review and three preliminary QF studies were carried out; one to the determine the best plane of motion and orientation of participants during QF imaging of the spine, a second to inform the optimal imaging protocol for the limb-socket interface and the third to validate a QF measurement of inter-vertebral stability. This phase determined the measurement parameters and investigative protocols. Given the complexity of the technique, 12 male below knee amputees and 12 healthy male controls of similar age and body mass index were recruited and received passive recumbent coronal QF imaging of their lumbar spines. This was followed immediately by anterior-posterior QF imaging of their limb-socket interfaces during three different forms of simulated gait. Differences between amputee and control spine kinematics and relationships between limb-socket motion and inter-vertebral kinematics in amputees were investigated. Results Passive recumbent coronal plane QF appears to be a valid method for measuring inter-vertebral stability. Although there were no systematic differences between the magnitude of inter-vertebral kinematics variables of amputees and controls, there was a trend towards greater variability in both inter-vertebral range and symmetry of motion in amputees and a significantly higher proportion of correlations in attainment rate between levels among amputees than controls (2-sided p <0.04). There was also a substantial, statistically significant inverse linear relationship between passive inter-vertebral motion symmetry and limb-socket telescoping in amputees. Conclusions This thesis provides evidence that the kinematics of the lumbar spine may be affected by lower limb amputation – particularly in respect of socket fit. The importance of consistency and symmetry of restraint by the intrinsic spinal holding elements in trans-tibial amputees has been highlighted. An indication of a relationship between limb socket telescoping and spine kinematics was identified, suggesting the need for replication of this part of the study in a larger amputee population. The variables of interest and the basis for this have been identified. Finally, inter-vertebral motion pattern variation has been associated with chronic low back pain in the literature. It was discovered that there was more interdependence in passive inter-vertebral motion between and across levels in below knee amputees than controls in terms of laxity, but not range of motion. The apparent relationship between this and socket fit in amputees suggests a possible mechanism and diagnostic subgroup in this population

Estimation of in vivo inter-vertebral loading during motion using fluoroscopic and magnetic resonance image informed finite element models

Finite element (FE) models driven by medical image data can be used to estimate subject-specific spinal biomechanics. This study aimed to combine magnetic resonance (MR) imaging and quantitative fluoroscopy (QF) in subject-specific FE models of upright standing, flexion and extension. Supine MR images of the lumbar spine were acquired from healthy participants using a 0.5 T MR scanner. Nine 3D quasi-static linear FE models of L3 to L5 were created with an elastic nucleus and orthotropic annulus. QF data was acquired from the same participants who performed trunk flexion to 60o and trunk extension to 20o. The displacements and rotations of the vertebrae were calculated and applied to the FE model. Stresses were averaged across the nucleus region and transformed to the disc co-ordinate system (S1 = mediolateral, S2 = anteroposterior, S3 = axial). In upright standing S3 was predicted to be -0.7 ± 0.6 MPa (L3L4) and -0.6 ± 0.5 MPa (L4L5). S3 increased to -2.0 ± 1.3 MPa (L3L4) and -1.2 ± 0.6 MPa (L4L5) in full flexion and to -1.1 ± 0.8 MPa (L3L4) and -0.7 ± 0.5 MPa (L4L5) in full extension. S1 and S2 followed similar patterns; shear was small apart from S23. Disc stresses correlated to disc orientation and wedging. The results demonstrate that MR and QF data can be combined in a participant-specific FE model to investigate spinal biomechanics in vivo and that predicted stresses are within ranges reported in the literature