Description of spine motion during gait in normal adolescents and young adults

Gait changes 2 years after posterior spinal fusion in adolescent idiopathic scoliosis patients

INTRODUCTION

Adolescent Idiopathic Scoliosis (AIS) patients were previously demonstrated to walk with gait abnormalities preoperatively. Our objective was to compare preoperative to 2-year follow-up results using gait analysis in AIS patients undergoing posterior spinal fusion (PSF).

MATERIAL AND METHODS

This is a retrospective single-center study. Patients with right thoracic curve, aged under 18 were included. They underwent low-dose biplanar radiographs preoperatively and at least 2 years after PSF. The day before surgery and at 2-year follow-up, quantitative gait analysis (QGA) was performed. Several gait parameters were recorded, such as sagittal and coronal thoracic and lumbar angles, dynamic CVA (dyn-CVA), dynamic SVA (dyn-SVA) and acromio-pelvis angle (APA). Motion of spine junctions were recorded (inflexion, flexion/extension and torsion).

RESULTS

49 patients were included (15.1 yo, 29.7 months FU). Main curve correction rate was 62.3 % ( ± 6.9). PSF led to a decrease in coronal thoracic and lumbar angles (13.2 vs -6° and -8.5 vs 0.9, p < 0.001, respectively). There was a significant decrease in Dyn-SVA (4.1 vs 3 cm, p < 0.001). Lumbo-sacral junction was significantly more in extension after spinal fusion (10.1 vs 14.4°, p < 0.001). APA changed from torsion toward the left to neutral position (-7.2 vs 0.0°, p < 0.001) with a significant decrease in range of motion (12.2 vs 9.6, p < 0.001). Increased lumbo-sacral extension was correlated to the number of levels fused (R=0.3740, p = 0.016). There was a positive correlation between LIV and the decrease of lumbo-sacral inflexion towards the right (R=-0.5036, p = 0.001).

DISCUSSION

Our study reveals that PSF led to several changes in gait pattern of AIS patients, including complete correction of torsional abnormalities, mainly influenced by Cobb angle correction. We found that more distal LIV led to a decrease of lumbo-sacral inflexion motion, but the consequences of such changes in the long run remain unclear, especially on the onset of disc degeneration.

Effects of step width and gait speed on the variability of mediolateral control in the head and trunk during gait

Step width is a parameter that determines the size of the base of support (BOS) during gait. Further, it is related to the control of center of mass (COM) and trunk movements and gait speed. The current study aimed to validate the effect of conditioning using combined step width (narrow and wide) and gait speed (normal [4.5 km/h] and slow [2.2 km/h]) on the segmental control of the head, thorax, and pelvis with respect to the BOS. The behavior of the head, thorax, and pelvis of 17 healthy adult participants were measured during treadmill walking using a three-dimensional motion analysis system. If the step width was narrow, the whole body segment with a high contribution to COM under narrow BOS conditions was more likely to have a high variability. However, the mediolateral direction behavior was small. On the contrary, if the step width was wide, the whole body segment with a high contribution to COM under wide BOS conditions was more likely to have a low variability. Nevertheless, the mediolateral direction behavior was large. Regarding the intersegmental association, particularly if the step width was narrow and the gait speed was normal, the head showed highly controlled movements with minimal displacement and increased fine-tuning. The thorax displayed significant importance in maintaining trunk stability, operating within a larger range of mediolateral displacement compared to the head and pelvis, under three conditions, except if the step width was narrow and the gait speed was normal. The study underscores the significant impact of both step width and gait speed on the control and stability of high-mass body segments during gait. It suggests that narrow step widths necessitate advanced control strategies, while wide step widths promote simpler, compensatory mechanisms, especially relevant in clinical contexts.

Pelvic Kinematics during Gait Following Long-Segment Spinal Fusion Due to Adult Spinal Deformity: An Analysis Using a Smartphone-Based Inertial Measurement Unit

Introduction

Gait changes could occur after thoracic to pelvic long-segment corrective fusion surgery, a common procedure for adult spinal deformity (ASD), potentially affecting the occurrence and progression of postoperative hip osteoarthritis. We aimed to clarify postoperative pelvic kinematics in patients with ASD by performing gait analysis using a system based on a smartphone-integrated inertial measurement unit (IMU).

Methods

A total of 21 consecutive outpatients (73.6±4.6 years old, 2 men, 19 women) were enrolled. All had undergone long-segment fusion from the thoracic spine to the pelvis for ASD more than 1 year previously and could walk unassisted. A control group comprised 20 healthy volunteers. The IMU was fixed on the sacrum, and data were collected when subjects walked forward on a flat indoor floor. Acceleration in three axial directions and angular velocity around the three axes were recorded simultaneously during gait, and data were cut out for each gait cycle. Of 1043 features obtained, the top 20 features with the smallest p-value in a statistical comparison were selected. These features, plus gender and age, were classified using gradient boosting machine learning based on the decision tree algorithm. The classification accuracy and relative importance of the feature items were calculated.

Results

The accuracy rate for gait classification between groups was 96.7% and the F1-score was 0.968. The factor that contributed most to the classification of gait in both groups was "y-angular,_change_quantiles,_f_agg="var",_isabs=True,_qh=0.6,_ql=0.2," which means the variance of the change of the absolute value in the pelvic rotation angular velocity in the horizontal plane in the range of 20%-60% of the gait cycle. Its relative importance was 0.351, which was smaller in the group with fusion.

Conclusions

Patients with ASD following long-segment fusion from the thoracic spine to the pelvis apparently have a gait style characterized by suppressed pelvic rotation in the horizontal plane.

Alignment considerations in degenerative spinal conditions: A narrative review

Background

With an aging population, degenerative spinal diseases are contributing significantly to the healthcare's burden. Spinal alignment in the context of adult spinal deformities has become an important domain of research.

Methods

We conducted a narrative review of the latest considerations in spinal alignment within the context of degenerative spinal conditions, discussed current strategies for morphological assessment and finally identified potential areas for future research.

Results

This review reported that degenerative spinal conditions lead to a complex disruption of spinal alignment. It also highlighted the importance of spino-pelvic alignment with specific attention to compensatory mechanisms that occur in response to spinal deformities. Emerging technologies including Artificial Intelligence and epigenetics are showing promises in terms of patient care.

Conclusions

Understanding spinal alignment in degenerative conditions underscores the importance of dynamic and individualized assessments. Future research should integrate emerging technologies along with traditional clinical practices in order to optimize patient outcomes and minimize complications for patients suffering from degenerative spinal diseases.

Is spinopelvic compensation associated with unstable gait?: Analysis using whole spine X-rays and a two-point accelerometer during gait in healthy adults

BACKGROUND

Pelvic incidence (PI)-lumbar lordosis (LL) mismatch has a significant destabilizing effect on the center of gravity sway in the static standing position. However, the association between spinopelvic alignment and balance during gait in healthy volunteers is poorly understood.

RESEARCH QUESTION

The degree of PI-LL mismatch and trunk anterior tilt in the static standing posture influences dynamic balance during gait.

METHODS

In this study, 131 healthy volunteers were divided into two groups: harmonious group (PI - LL ≤ 10°; n = 91) and unharmonious group (PI - LL > 10°; n = 40). A two-point accelerometer system was used for gait analysis; accelerometers were attached to the pelvis and upper trunk to measure acceleration in the forward-backward, right-left, and vertical directions so that sagittal (front-back) deviation width, coronal (right-left) width, and vertical width and their ratios were calculated. Measurements were compared between the two groups, and correlations between alignment and accelerometer data were examined.

RESULTS

The harmonious group showed a negative correlation between pelvic sagittal width and PI - LL, pelvic tilt (PT), and sagittal vertical axis (SVA) (correlation coefficient ρ = -0.42, -0.38, and -0.4, respectively), and a positive correlation between sagittal ratio and PI - LL (ρ = 0.35). The unharmonious group showed a positive correlation between pelvic sagittal width and PI and PT (ρ = 0.43 and 0.33, respectively) and between sagittal ratio and SVA (ρ = 0.32). The unharmonious group showed a positive correlation between upper trunk sagittal width and PI - LL and PT (ρ = 0.38 and 0.36, respectively).

SIGNIFICANCE

The association between spinal alignment and gait parameters differs depending on the presence or absence of PI-LL mismatch. The degree of pelvic compensation and trunk anterior tilt during static standing were associated with unstable gait balance.

Enhancing biomechanical machine learning with limited data: generating realistic synthetic posture data using generative artificial intelligence

Objective: Biomechanical Machine Learning (ML) models, particularly deep-learning models, demonstrate the best performance when trained using extensive datasets. However, biomechanical data are frequently limited due to diverse challenges. Effective methods for augmenting data in developing ML models, specifically in the human posture domain, are scarce. Therefore, this study explored the feasibility of leveraging generative artificial intelligence (AI) to produce realistic synthetic posture data by utilizing three-dimensional posture data. Methods: Data were collected from 338 subjects through surface topography. A Variational Autoencoder (VAE) architecture was employed to generate and evaluate synthetic posture data, examining its distinguishability from real data by domain experts, ML classifiers, and Statistical Parametric Mapping (SPM). The benefits of incorporating augmented posture data into the learning process were exemplified by a deep autoencoder (AE) for automated feature representation. Results: Our findings highlight the challenge of differentiating synthetic data from real data for both experts and ML classifiers, underscoring the quality of synthetic data. This observation was also confirmed by SPM. By integrating synthetic data into AE training, the reconstruction error can be reduced compared to using only real data samples. Moreover, this study demonstrates the potential for reduced latent dimensions, while maintaining a reconstruction accuracy comparable to AEs trained exclusively on real data samples. Conclusion: This study emphasizes the prospects of harnessing generative AI to enhance ML tasks in the biomechanics domain.

Kinematic Evaluation of the Sagittal Posture during Walking in Healthy Subjects by 3D Motion Analysis Using DB-Total Protocol

Posture can be evaluated by clinical and instrumental methods. Three-dimensional motion analysis is the gold standard for the static and dynamic postural assessment. Conventional stereophotogrammetric protocols are used to assess the posture of pelvis, hip, knee, ankle, trunk (considered as a single segment) and rarely head and upper limbs during walking. A few studies also analyzed the multi-segmental trunk and whole-body kinematics. Aim of our study was to evaluate the sagittal spine and the whole-body during walking in healthy subjects by 3D motion analysis using a new marker set. Fourteen healthy subjects were assessed by 3D-Stereophotogrammetry using the DB-Total protocol. Excursion Range, Absolute Excursion Range, Average, intra-subject Coefficient of Variation (CV) and inter-subject Standard Deviation Average (SD Average) of eighteen new kinematic parameters related to sagittal spine and whole-body posture were calculated. The analysis of the DB-Total parameters showed a high intra-subject (CV < 50%) and a high inter-subject (SD Average < 1) repeatability for the most of them. Kinematic curves and new additional values were reported. The present study introduced new postural values characterizing the sagittal spinal and whole-body alignment of healthy subjects during walking. DB-Total parameters may be useful for understanding multi-segmental body biomechanics and as a benchmark for pathological patterns.