Spinal Palpation Error and Its Impact on Skin Marker-Based Spinal Alignment Measurement in Adult Spinal Deformity

Spinal alignment measurement in spinal deformity research has recently shifted from using mainly two-dimensional static radiography toward skin marker-based motion capture approaches, allowing three-dimensional (3D) assessments during dynamic conditions. The validity and accuracy of such skin marker-based methods is highly depending on correct marker placement. In this study we quantified, for the first time, the 3D spinal palpation error in adult spinal deformity (ASD) and compared it to the error in healthy spines. Secondly, the impact of incorrect marker placement on the accuracy of marker-based spinal alignment measurement was investigated. 3D, mediolateral and inferosuperior palpation errors for thoracolumbar and lumbar vertebral levels were measured on biplanar images by extracting 3D positions of skin-mounted markers and their corresponding anatomical landmarks in 20 ASD and 10 healthy control subjects. Relationships were investigated between palpation error and radiographic spinal alignment (lordosis and scoliosis), as well as body morphology [BMI and soft tissue (ST) thickness]. Marker-based spinal alignment was measured using a previously validated method, in which a polynomial is fit through the marker positions of a motion trial and which allows for radiograph-based marker position correction. To assess the impact of palpation error on spinal alignment measurement, the agreement was investigated between lordosis and scoliosis measured by a polynomial fit through, respectively, (1) the uncorrected marker positions, (2) the palpation error-corrected (optimal) marker positions, and (3) the anatomically corrected marker positions (toward the vertebral body), and their radiographic equivalents expressed as Cobb angles (ground truth), using Spearman correlations and root mean square errors (RMSE). The results of this study showed that, although overall accuracy of spinal level identification was similar across groups, mediolateral palpation was less accurate in the ASD group (ASDmean: 6.8 mm; Controlmean: 2.5 mm; p = 0.002). Significant correlations with palpation error indicated that determining factors for marker misplacement were spinal malalignment, in particular scoliotic deformity (r = 0.77; p < 0.001), in the ASD group and body morphology [i.e., increased BMI (rs = 0.78; p = 0.008) and ST thickness (rs = 0.66; p = 0.038)] in healthy spines. Improved spinal alignment measurements after palpation error correction, shows the need for radiograph-based marker correction methods, and therefore, should be considered when interpreting spinal kinematics

Spinal Palpation Error and Its Impact on Skin Marker-Based Spinal Alignment Measurement in Adult Spinal Deformity

Spinal alignment measurement in spinal deformity research has recently shifted from using mainly two-dimensional static radiography toward skin marker-based motion capture approaches, allowing three-dimensional (3D) assessments during dynamic conditions. The validity and accuracy of such skin marker-based methods is highly depending on correct marker placement. In this study we quantified, for the first time, the 3D spinal palpation error in adult spinal deformity (ASD) and compared it to the error in healthy spines. Secondly, the impact of incorrect marker placement on the accuracy of marker-based spinal alignment measurement was investigated. 3D, mediolateral and inferosuperior palpation errors for thoracolumbar and lumbar vertebral levels were measured on biplanar images by extracting 3D positions of skin-mounted markers and their corresponding anatomical landmarks in 20 ASD and 10 healthy control subjects. Relationships were investigated between palpation error and radiographic spinal alignment (lordosis and scoliosis), as well as body morphology [BMI and soft tissue (ST) thickness]. Marker-based spinal alignment was measured using a previously validated method, in which a polynomial is fit through the marker positions of a motion trial and which allows for radiograph-based marker position correction. To assess the impact of palpation error on spinal alignment measurement, the agreement was investigated between lordosis and scoliosis measured by a polynomial fit through, respectively, (1) the uncorrected marker positions, (2) the palpation error-corrected (optimal) marker positions, and (3) the anatomically corrected marker positions (toward the vertebral body), and their radiographic equivalents expressed as Cobb angles (ground truth), using Spearman correlations and root mean square errors (RMSE). The results of this study showed that, although overall accuracy of spinal level identification was similar across groups, mediolateral palpation was less accurate in the ASD group (ASDmean: 6.8 mm; Controlmean: 2.5 mm; p = 0.002). Significant correlations with palpation error indicated that determining factors for marker misplacement were spinal malalignment, in particular scoliotic deformity (r = 0.77; p < 0.001), in the ASD group and body morphology [i.e., increased BMI (rs = 0.78; p = 0.008) and ST thickness (rs = 0.66; p = 0.038)] in healthy spines. Improved spinal alignment measurements after palpation error correction, shows the need for radiograph-based marker correction methods, and therefore, should be considered when interpreting spinal kinematics

Between-Day Reliability of the Gait Characteristics and Their Changes During the 6-Minute Walking Test in People With Multiple Sclerosis

Background: Gait characteristics and their changes during the 6-minute walking test (6MWT) in people with multiple sclerosis (pwMS) have been described in the literature, which one may refer to as walking fatigability in the body function level of the International Classification of Functioning, Disability, and Health. However, whether these metrics are reliable is unknown. Objective: To investigate the between-day reliability of the gait characteristics and their changes in pwMS and healthy controls (HCs). Methods: Forty-nine pwMS (EDSS 4.82 ± 1.22 and 54.7 ± 9.36 years) and 23 HCs (50.6 ± 6.1 years) performed the 6MWT, as fast as possible but safely while wearing Inertial Measurement Units. Gait characteristics were measured in the pace, rhythm, variability, asymmetry, kinematics, coordination, and postural control domains and were obtained in intervals of 1 minute during the 6MWT. In addition, gait characteristics change in the last minute compared with the first minute were calculated for all gait variables using a fatigability index (ie, distance walking index). The intraclass correlation coefficient (ICC), Bland-Altman Plots, and Standard error of measurement were applied to investigate reliability. Results: Reliability of gait characteristics, minute-by-minute, and for their changes (ie, using the fatigability index) ranged from poor to excellent (pwMS: ICC 0.46-0.96; HC: ICC 0.09-0.97 and pwMS: ICC 0-0.72; HC: ICC 0-0.77, respectively). Conclusion: Besides coordination, at least 1 variable of each gait domain showed an ICC of moderate or good reliability for gait characteristics changes in both pwMS and HC. These metrics can be incorporated into future clinical trials and research on walking fatigability.Clinical Trial Registration: NCT05412043

Observation of the radiative decay mode of the free neutron

The theory of quantum electrodynamics (QED) predicts that beta decay of the neutron into a proton, electron and antineutrino should be accompanied by a continuous spectrum of soft photons. While this inner bremsstrahlung branch has been previously measured in nuclear beta and electron capture decay, it has never been observed in free neutron decay. Recently, the photon energy spectrum and branching ratio for neutron radiative decay have been calculated using two approaches: a standard QED framework(1-3) and heavy baryon chiral perturbation theory(4) (an effective theory of hadrons based on the symmetries of quantum chromodynamics). The QED calculation treats the nucleons as point-like, whereas the latter approach includes the effect of nucleon structure in a systematic way. Here we observe the radiative decay mode of free neutrons, measuring photons in coincidence with both the emitted electron and proton. We determined a branching ratio of (3.13 +/- 0.34) x 10(-3) (68 per cent level of confidence) in the energy region between 15 and 340 keV, where the uncertainty is dominated by systematic effects. The value is consistent with the predictions of both theoretical approaches; the characteristic energy spectrum of the radiated photons, which differs from the uncorrelated background spectrum, is also consistent with the calculated spectrum. This result may provide opportunities for more detailed investigations of the weak interaction processes involved in neutron beta decay.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62639/1/nature05390.pd

Reliability of the balance evaluation systems test and trunk control measurement scale in adult spinal deformity.

ObjectiveTo test the reliability of the Balance Evaluation Systems Test (BESTest) and Trunk Control Measurement Scale (TCMS) between sessions and raters in the adult spinal deformity (ASD) population.Summary of background dataUp to now evaluation in ASD was mainly based on static radiographic parameters. Recently literature showed that dynamic balance was a better predictor of health-related quality of life than radiographic parameters, stressing the importance of balance assessment. However, to the best of our knowledge, reliability of balance assessment tools has not yet been investigated in the ASD population.MethodsTwenty ASD patients participated in this study. Ten patients were included in the test-retest study, including repeated measurements. Ten patients were measured once, simultaneously but independently by three raters. Each participant performed two balance scales, namely the BESTest and the TCMS. Statistical analysis consisted of intra class correlations (ICC) on scale- and subscale level, and kappa scores on item-level. Cronbach's alpha on total scores, standard errors of measurement (SEM), smallest detectable differences and percentages of agreement were also calculated. Bland-altman plots were created to investigate systematic bias.ResultsICC scores between sessions and raters for TCMS (0.76 and 0.88) and BESTest (0.90 and 0.94) total scores were good to excellent. SEM's between sessions and raters were also low for total scores on TCMS (1.66 and 2.35) and BESTest (2.99 and 2.32). However, on subscale- and item-level reliability decreased and ceiling effects were observed. No systematic bias was observed between sessions and raters.ConclusionBESTest and TCMS showed to be reliable tools to measure balance in ASD on scale-level. However, on subscale- and item-level reliability decreased and ceiling effects were observed. Therefore, the question arises if there is need for an ASD-specific balance scale

Reliability of the balance evaluation systems test and trunk control measurement scale in adult spinal deformity

OBJECTIVE: To test the reliability of the Balance Evaluation Systems Test (BESTest) and Trunk Control Measurement Scale (TCMS) between sessions and raters in the adult spinal deformity (ASD) population. SUMMARY OF BACKGROUND DATA: Up to now evaluation in ASD was mainly based on static radiographic parameters. Recently literature showed that dynamic balance was a better predictor of health-related quality of life than radiographic parameters, stressing the importance of balance assessment. However, to the best of our knowledge, reliability of balance assessment tools has not yet been investigated in the ASD population. METHODS: Twenty ASD patients participated in this study. Ten patients were included in the test-retest study, including repeated measurements. Ten patients were measured once, simultaneously but independently by three raters. Each participant performed two balance scales, namely the BESTest and the TCMS. Statistical analysis consisted of intra class correlations (ICC) on scale- and subscale level, and kappa scores on item-level. Cronbach's alpha on total scores, standard errors of measurement (SEM), smallest detectable differences and percentages of agreement were also calculated. Bland-altman plots were created to investigate systematic bias. RESULTS: ICC scores between sessions and raters for TCMS (0.76 and 0.88) and BESTest (0.90 and 0.94) total scores were good to excellent. SEM's between sessions and raters were also low for total scores on TCMS (1.66 and 2.35) and BESTest (2.99 and 2.32). However, on subscale- and item-level reliability decreased and ceiling effects were observed. No systematic bias was observed between sessions and raters. CONCLUSION: BESTest and TCMS showed to be reliable tools to measure balance in ASD on scale-level. However, on subscale- and item-level reliability decreased and ceiling effects were observed. Therefore, the question arises if there is need for an ASD-specific balance scale.status: publishe

Personalized musculoskeletal modeling of spinal deformities based on stereoradiographic images for biomechanical analysis of motion

1. INTRODUCTION Adult Spinal Deformity (ASD) is present in 68% of the population older than 60 years [1]. Surgical treatment aims at stabilizing the deformed spine which, apart from preventing curve progression, also aims at achieving a balanced spinal posture and reducing back pain. Although, surgery is associated with more positive outcome compared to non-surgical treatment, up to 70% of ASD patients suffer from post-operative complications [2]. This high complication rate is expected to be closely linked to a conceptual lacuna in the clinical evaluation process, and specifically in the lack of knowledge about how ASD impacts the locomotor system [3]. Since most pain and complaints for ASD patients arise during dynamic activities of daily living, the use of static medical image-based assessment approaches alone fails to describe the functional ability during these activities. Therefore the insights into the impact of the deformity itself as well as its treatment are severely limited. Musculoskeletal modeling and simulation has clear potential to fill this knowledge gap. Through these techniques, the functional ability of spine patients can be assessed in terms of muscle and contact forces during motion. Unfortunately however, applying multi-body simulation in ASD is currently not possible, as most available musculoskeletal models (MSMs) do not allow to include the effect of spinal deformities on musculoskeletal geometry. Therefore, the aim of this research project is to develop a software platform for radiograph-based subject-specific modeling of the spine. 2. MATERIALS AND METHODS Using the state-of-the-art generic model of Bruno et al. [4] as a basis, the modeling platform allows for custom-made, manual routines to adjust the size and pose of the included bone models, based on biplanar x-ray images (fig. 1), acquired using the EOS Imaging system (EOS Imaging, France), which is considered as ground truth. The modeling platform further allows the identification of reflective markers and the definition of their position relative to the underlying bony segments and has fully functional import and export links to the OpenSim simulation platform (SimTK, Stanford, fig. 2). Following ethical approval and informed consent We applied the workflow to a subject with ASD (49y, male, 71kg), obtaining a subjectspecific model. Furthermore we applied the standard approach of marker-based scaling of the generic model (fig. 3). This subject underwent 3D motion analysis using a motion capture system (Vicon Nexus, Oxford, UK). Next, both models were compared statically and dynamically through MSM simulations. 3. RESULTS AND DISCUSSION Using the developed modeling platform, the need for subject-specific MSMs is confirmed as the currently available generic musculoskeletal model failed to accurately represent spinal deformity using the standard approach of marker-based scaling (fig. 3 vs. fig. 4). Furthermore, the potential of image-based marker personalization was demonstrated as a means of correcting palpation errors. Finally, the estimated vertebral compressive loading and muscle activations using dynamic simulations of spine motion were found to be very sensitive to the vertebral alignment in the MSM used.status: publishe

Introducing dynamic balance assessment in Adult Spinal Deformity

Introduction: Adult spinal deformity (ASD) comprises a wide range of three-dimensional spinal malalignments causing pain and disability. In current clinical practice, spinal alignment, quantified through static, two-dimensional imaging-based measurements, has often been incorrectly defined as ‘spinal balance’. However, this does not take dynamic properties of the spine into account. Hence, the question raises if more dynamic evaluation tools are required for ASD assessment. Dynamic balance assessment tools are frequently applied in neurologic pathologies, in which balance is known to be challenged. Since these tools have not yet been introduced in ASD, the aim of this study was to select appropriate balance scales for ASD, and compare balance between ASD and control subjects. Research question: Can existing balance scores identify impaired balance in ASD subjects compared to controls? Methods: First, a review of literature on balance assessment tools was performed. Based on critical appraisal of parameters (clinical applicability, (time) cost, safety, ceiling effects and balance subscales) and discussions with experts, the most clinically relevant scales for application in ASD were selected and applied in a pilot cohort of 10 ASD and 10 controls by one single rater. Mann–Whitney U test with Bonferroni correction was used to analyze balance scores. Pain was assessed by means of the VAS-scale before, during and after measurement, and analyzed by using a repeated measures ANOVA. Results: The review highlighted nine balance scales: Berg Balance Scale, Trunk Impairment Scale, Trunk Control Measure- ment Scale (TCMS), Physical Performance Test, modified Physical Performance Test, Fullerton Advanced Balance Scale, Balance Evaluations System Test (BESTest), Mini-BESTest and Brief- BESTest. Based on the above parameters, TCMS and BESTest were found to be the most appropriate. The ASD group scored worse on both TCMS and BESTest (Table 1). VAS-scores of ASD subjects were significantly increased after ("VASTCMS+BEST: 1.6 1.28; p = 0.03) but not during ("VASTCMS: 0.95 1.24 p = 0.105; "VASBEST: 0.65 1.24; p = 0.1) assessment. Discussion: Lower scores of ASD subjects on both tests indicate that adults with spinal deformity have impaired balance and that TCMS and BESTest are able to discriminate between ASD and healthy subjects. The subscale scores revealed that balance is mainly challenged in more dynamic items, emphasizing the need for dynamic over the currently standard static testing. Probably patients cannot fully compensate for their spinal deformity in more dynamic conditions. This confirms recent findings stating that during walking, ASD patients lose their compensation of pelvic retroversion [1]. VAS scores tend to indicate the need for taking patient feasibility and pain into account in future application of balance scales. Nevertheless, this pilot study highlights the potential impact of dynamic balance assessment on clinical decision making in ASD.status: publishe

The next step in routine creation of subject-specific models: A hybrid radiograph-based musculoskeletal model.

status: Published onlin

Development and validation of a modeling workflow for the generation of image-based, subject-specific thoracolumbar models of spinal deformity

Quantitative dynamic evaluation of spino-pelvic motion in subjects with spinal deformity using optical motion analysis is currently lacking. The aim of this study was to develop and validate subject-specific, thoracolumbar spine multi-body skeletal models for evaluating spino-pelvic kinematics in a spinal deformity population. A new workflow for creating subject-specific spino-pelvic models in a weight-bearing position through computed tomography (CT) and biplanar radiography is described. As part of a two-step validation process the creation of such a model was first validated against a ground truth CT reconstruction of a plastinated cadaver. Secondly, biplanar radiographic images of one healthy and 12 adult spinal deformity subjects were obtained in two standing positions: upright and bent. Two subject-specific models for each of these subjects were then created to represent both standing positions. The result of inverse kinematics solutions, simulating the specific bending motion using the upright models, are compared with the models created in bent position, quantifying the marker-based spino-pelvic tracking accuracy. The workflow created spinal deformity models with mean accuracies between 0.71-1.95 mm and 1.25-2.27° for vertebral positions and orientations, respectively. In addition, the mean marker-based spino-pelvic tracking accuracies were between 0.9-1.8 mm and 2.9-5.6° for vertebral positions and rotations, respectively. This study presented the first validated biplanar radiography-based method to generate subject-specific spino-pelvic, rigid body models that allows the inclusion of subject-specific bone geometries, the personalization of the 3D weight-bearing spinal alignment with accuracy comparable to clinically used software for 3D reconstruction, and the localization of external markers in spinal deformity subjects. This work will allow new concepts of dynamic functionality evaluation of patients with spinal deformity.status: publishe