Validity of flexicurve and motion capture for measurements of thoracic kyphosis vs standing radiographic measurements

Physiological and Anthropometric Factors Associated With Spine Loading Estimates From Imaging-Based Subject-Specific Musculoskeletal Models

Background

Subject-specific musculoskeletal models may be used to estimate spine loads that cannot be measured in vivo. Model generation methods may use detailed measurements extracted from medical imaging, but it may be possible to create accurate models without these measurements. We aimed to determine which physiological and anthropometric factors are associated with spine loading and should be accounted for in model creation.

Methods

We created models of 440 subjects from the Framingham Heart Study Multi-detector CT Study, extracting muscle morphology and spine profile information from CT scans of the trunk. Five lifting activities were simulated, and compressive and shear loading estimates were produced. We performed principal component analysis on the loading data from three locations in the spine, as well as univariate correlations between predictor variables and each principal component (PC). We identified multivariate predictive regression models for each PC and individual loading estimate.

Results

A single PC explained 90% of the variability in compressive loading, while four PCs were identified that explained 10%-37% individually, 86% in total, of the variability in shear loading. Univariate analysis showed that body weight, BMI, lean mass, and waist circumference were most associated with the compression PC and first shear PC. Multivariate regression modeling showed predictor variables predicted 94% of the variability in the compression PC, but only 54% in the first shear PC, with body weight having the highest contribution. Additional shear PCs were less predictable. Level- and activity-specific compressive loading was predicted using a limited set of physiological and anthropometric factors.

Conclusions

This work identifies easily measured characteristics, particularly weight and height, along with sex, associated with subject-specific loading estimates. It suggests that compressive loading, or models to evaluate compressive loading, may be based on a limited set of anthropometric attributes. Shear loading appears more complex and may require additional information not captured in the set of factors we examined.

The effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading during squat and stoop lifts

Back support exosuits aim to reduce tissue demands and thereby risk of injury and pain. However, biomechanical analyses of soft active exosuit designs have been limited. The objective of this study was to evaluate the effect of a soft active back support exosuit on trunk motion and thoracolumbar spine loading in participants performing stoop and squat lifts of 6 and 10 kg crates, using participant-specific musculoskeletal models. The exosuit did not change overall trunk motion but affected lumbo-pelvic motion slightly, and reduced peak compressive and shear vertebral loads at some levels, although shear increased slightly at others. This study indicates that soft active exosuits have limited kinematic effects during lifting, and can reduce spinal loading depending on the vertebral level. These results support the hypothesis that a soft exosuit can assist without limiting trunk movement or negatively impacting skeletal loading and have implications for future design and ergonomic intervention efforts.

The association of hamstring tightness with lumbar lordosis and trunk flexibility in healthy individuals: gender analysis

Objectives: The purpose of this study was to investigate if there is a relation between hamstring tightness and lumbar lordosis as well as trunk flexibility based on gender differences and to analyze the differences in hamstring tightness, lumber lordosis and trunk flexibility in healthy adults. Methods: One hundred young healthy adults were recruited and distributed into 2 equal groups according to gender: group A (female group) and group B (male group). Hamstring tightness (HT) was measured by Active Knee Extension (AKE) test and Straight Leg Raise (SLR) test, the angle of lumbar lordosis was measured with a flexible ruler from standing position and trunk flexion flexibility (TFF) was measured by Fingertip-to-Floor Test. Results: There was a significant correlation between TFF and both measures of HT (SLR, p = 0.001; AKE, p = 0.001) in females. While, there was a non-significant correlation in males (SLR, p = 0.900; AKE, p = 0.717). Moreover, there was a non-significant correlation between lumbar lordosis and HT measures in both groups as (p > 0.05). Furthermore, there were significant differences between males and females in hamstring flexibility, TFF and lumbar lordosis as (p < 0.05). Conclusion: Gender differences in the relationship between hamstring tightness and trunk flexion flexibility are significant. However, there was no significant difference between males and females in the relationship between hamstring tightness and lumbar lordosis.

Does stretching of anterior structures alone, or in combination with strengthening of posterior structures, decrease hyperkyphosis and improve posture in adults? A Systematic Review and Meta-analysis

Kyphosis can lead to back pain, poor posture, and increased falls risk. This systematic review aimed to synthesize research on stretching alone, or in combination with strengthening, as a management for hyperkyphosis in the adult population (≥18 years old). An electronic database search was conducted from February to March 2022. The author and an independent reviewer screened titles and abstracts for inclusion criteria - those whose intervention involved stretching alone or with strengthening exercises. The author appraised and extracted data from included articles and performed a meta-analysis where appropriate. The database and citation search yielded 327 articles, 18 of which met inclusion criteria. One study included performed stretching as a standalone intervention; the remainder used a combination of stretching and strengthening. The meta-analysis (n=3, with 5 exercise groups) found a statistically significant difference (MD = -6.97 (95% CI -9.84, -4.10), p<0.00001) in post-intervention measures of hyperkyphosis favouring the exercise group. The narrative review of studies agrees with this finding, demonstrating statistically significant improvement in hyperkyphosis following various exercise programs. This review suggests that stretching and strengthening exercises improve hyperkyphosis in the short and long term. Low-quality evidence supports stretching as a standalone intervention. Further, more robust research is required to recommend procedures and determine if stretching alone is effective for treating hyperkyphosis in adults.

Reliability of the Smartphone Application Inclinometer and Flexicurve in Measuring Thoracic Kyphosis

INTRODUCTION

This study examined the inter- and intra-rater reliability of the smartphone inclinometer app (SPI) and flexicurve (FC) for assessing the kyphotic angle in individuals with thoracic kyphosis (TK).

METHODS

This study was conducted with 60 subjects (35 males, 25 females) aged 18 to 25 who presented to Kalyon Medical Center, Gaziantep, Turkey, between December 2021 and March 2022. The subjects were evaluated by two independent assessors using FC and SPI to measure the TK angle. The intraclass correlation coefficient (ICC) was analysed at a 95% confidence interval. The level of agreement between the methods was checked using Bland-Altman analysis.

RESULTS

Inter- and intra-rater measurements were strongly correlated (ICC 0.945 and 0.964, respectively). On the Bland-Altman plots, the FC showed poor agreement with the SPI app (mean difference, 19.81° ± 2.8°). The mean kyphotic angles were 45.15 ± 6.07° and 25.34 ± 4.96°, respectively, as measured by the SPI and FC.

CONCLUSION

This study demonstrated good intra- and inter-rater reliability of the SPI app and FC for the measurement of the spinal curvature (TK) angle in the sagittal plane. A weak agreement was discerned between the SPI and FC methods.

Walking Biomechanics and Spine Loading in Patients With Symptomatic Lumbar Spinal Stenosis

Symptomatic lumbar spinal stenosis is a leading cause of pain and mobility limitation in older adults. It is clinically believed that patients with lumbar spinal stenosis adopt a flexed trunk posture or bend forward and alter their gait pattern to improve tolerance for walking. However, a biomechanical assessment of spine posture and motion during walking is broadly lacking in these patients. The purpose of this study was to evaluate lumbar spine and pelvic sagittal angles and lumbar spine compressive loads in standing and walking and to determine the effect of pain and neurogenic claudication symptoms in patients with symptomatic lumbar spinal stenosis. Seven participants with symptomatic lumbar spinal stenosis, aged 44–82, underwent a 3D opto-electronic motion analysis during standing and walking trials in asymptomatic and symptomatic states. Passive reflective marker clusters (four markers each) were attached to participants at T1, L1, and S2 levels of the spine, with additional reflective markers at other spinal levels, as well as the head, pelvis, and extremities. Whole-body motion data was collected during standing and walking trials in asymptomatic and symptomatic states. The results showed that the spine was slightly flexed during walking, but this was not affected by symptoms. Pelvic tilt was not different when symptoms were present, but suggests a possible effect of more forward tilt in both standing (p = 0.052) and walking (p = 0.075). Lumbar spine loading during symptomatic walking was increased by an average of 7% over asymptomatic walking (p = 0.001). Our results did not show increased spine flexion (adopting a trunk-flexed posture) and only indicate a trend for a small forward shift of the pelvis during both symptomatic walking and standing. This suggests that provocation of symptoms in these patients does not markedly affect their normal gait kinematics. The finding of increased spine loading with provocation of symptoms supports our hypothesis that spine loading plays a role in limiting walking function in patients with lumbar spinal stenosis, but additional work is needed to understand the biomechanical cause of this increase.

Between-session reliability of subject-specific musculoskeletal models of the spine derived from optoelectronic motion capture data

This study evaluated the between-session reliability of creating subject-specific musculoskeletal models with optoelectronic motion capture data, and using them to estimate spine loading. Nineteen healthy participants aged 24-74 years underwent the same set of measurements on two separate occasions. Retroreflective markers were placed on anatomical regions, including C7, T1, T4, T5, T8, T9, T12 and L1 spinous processes, pelvis, upper and lower limbs, and head. We created full-body musculoskeletal models with detailed thoracolumbar spines, and scaled these to create subject-specific models for each individual and each session. Models were scaled from distances between markers, and spine curvature was adjusted according to marker-estimated measurements. Using these models, we estimated vertebral compressive loading for five different standardized postures: neutral standing, 45˚ trunk flexion, 15˚ trunk extension, 20˚ lateral bend to the right, and 45˚ axial rotation to the right. Intraclass correlation coefficients (ICCs) and standard error of measurement were calculated as measures of between-session reliability and measurement error, respectively. Spine curvature measures showed excellent reliability (ICC = 0.79-0.91) and body scaling segments showed fair to excellent reliability (ICC = 0.46-0.95). We found that musculoskeletal models showed mostly excellent between-session reliability to estimate spine loading, with 91% of ICC values > 0.75 for all activities. This information is a necessary precursor for using motion capture data to estimate spine loading from subject-specific musculoskeletal models, and suggests that marker data will deliver reproducible subject-specific models and estimates of spine loading.