Wearable motion-based platform for functional spine health assessment.

INTRODUCTION: Low back pain is a significant burden to society and the lack of reliable outcome measures, combined with a prevailing inability to quantify the biopsychosocial elements implicated in the disease, impedes clinical decision-making and distorts treatment efficacy. This paper aims to validate the utility of a biopsychosocial spine platform to provide standardized wearable sensor-derived functional motion assessments to assess spine function and differentiate between healthy controls and patients. Secondarily, we explored the correlation between these motion features and subjective biopsychosocial measures. METHODS: An observational study was conducted on healthy controls (n=50) and patients with low back pain (n=50) to validate platform utility. The platform was used to conduct functional assessments along with patient-reported outcome assessments to holistically document cohort differences. Our primary outcomes were motion features; and our secondary outcomes were biopsychosocial measures (pain, function, etc). RESULTS: Our results demonstrated statistically significant differences in motion features between healthy and patient cohorts across anatomical planes. Importantly, we found velocity and acceleration in the axial plane showed the largest difference, with healthy controls having 49.7% and 55.7% higher values, respectively, than patients. In addition, we found significant correlations between motion features and biopsychosocial measures for pain, physical function and social role only. CONCLUSIONS: Our study validated the use of wearable sensor-derived functional motion metrics in differentiating healthy controls and patients. Collectively, this technology has the potential to facilitate holistic biopsychosocial evaluations to enhance spine care and improve patient outcomes. TRIAL REGISTRATION NUMBER: NCT05776771.

Cognitive dissonance increases spine loading in the neck and low back.

Cognitive dissonance refers to a state where two psychologically inconsistent thoughts, behaviours, or attitudes are held at the same time. The objective of this study was to explore the potential role of cognitive dissonance in biomechanical loading in the low back and neck. Seventeen participants underwent a laboratory experiment involving a precision lowering task. To establish a cognitive dissonance state (CDS), study participants were provided negative feedback on their performance running counter to a pre-established expectation that their performance was excellent. Dependent measures of interest were spinal loads in the cervical and lumbar spines, calculated via two electromyography-driven models. The CDS was associated with increases to peak spinal loads in the neck (11.1%, p < .05) and low back (2.2%, p < .05). A greater CDS magnitude was also associated with a greater spinal loading increase. Therefore, cognitive dissonance may represent a risk factor for low back/neck pain that has not been previously identified.Practitioner summary: Upon establishing a cognitive dissonance state in a group of participants, spinal loading in the cervical and lumbar spines were increased proportional to the magnitude of the cognitive dissonance reported. Therefore, cognitive dissonance may represent a risk factor for low back and neck pain that has not been previously identified.

The Back Pain Consortium (BACPAC) Research Program: Structure, Research Priorities, and Methods.

In 2019, the National Health Interview survey found that nearly 59% of adults reported pain some, most, or every day in the past 3 months, with 39% reporting back pain, making back pain the most prevalent source of pain, and a significant issue among adults. Often, identifying a direct, treatable cause for back pain is challenging, especially as it is often attributed to complex, multifaceted issues involving biological, psychological, and social components. Due to the difficulty in treating the true cause of chronic low back pain (cLBP), an over-reliance on opioid pain medications among cLBP patients has developed, which is associated with increased prevalence of opioid use disorder and increased risk of death. To combat the rise of opioid-related deaths, the National Institutes of Health (NIH) initiated the Helping to End Addiction Long-TermSM (HEAL) initiative, whose goal is to address the causes and treatment of opioid use disorder while also seeking to better understand, diagnose, and treat chronic pain. The NIH Back Pain Consortium (BACPAC) Research Program, a network of 14 funded entities, was launched as a part of the HEAL initiative to help address limitations surrounding the diagnosis and treatment of cLBP. This paper provides an overview of the BACPAC research program's goals and overall structure, and describes the harmonization efforts across the consortium, define its research agenda, and develop a collaborative project which utilizes the strengths of the network. The purpose of this paper is to serve as a blueprint for other consortia tasked with the advancement of pain related science.

Biomechanical Phenotyping of Chronic Low Back Pain: Protocol for BACPAC.

OBJECTIVE: Biomechanics represents the common final output through which all biopsychosocial constructs of back pain must pass, making it a rich target for phenotyping. To exploit this feature, several sites within the NIH Back Pain Consortium (BACPAC) have developed biomechanics measurement and phenotyping tools. The overall aims of this article were to: 1) provide a narrative review of biomechanics as a phenotyping tool; 2) describe the diverse array of tools and outcome measures that exist within BACPAC; and 3) highlight how leveraging these technologies with the other data collected within BACPAC could elucidate the relationship between biomechanics and other metrics used to characterize low back pain (LBP). METHODS: The narrative review highlights how biomechanical outcomes can discriminate between those with and without LBP, as well as among levels of severity of LBP. It also addresses how biomechanical outcomes track with functional improvements in LBP. Additionally, we present the clinical use case for biomechanical outcome measures that can be met via emerging technologies. RESULTS: To answer the need for measuring biomechanical performance, our "Results" section describes the spectrum of technologies that have been developed and are being used within BACPAC. CONCLUSION AND FUTURE DIRECTIONS: The outcome measures collected by these technologies will be an integral part of longitudinal and cross-sectional studies conducted in BACPAC. Linking these measures with other biopsychosocial data collected within BACPAC increases our potential to use biomechanics as a tool for understanding the mechanisms of LBP, phenotyping unique LBP subgroups, and matching these individuals with an appropriate treatment paradigm.

Feasibility, safety, and efficacy of circumferential spine stereotactic body radiotherapy.

Background: With advances in systemic therapy translating to improved survival in metastatic malignancies, spine metastases have become an increasingly common source of morbidity. Achieving durable local control (LC) for patients with circumferential epidural disease can be particularly challenging. Circumferential stereotactic body radiotherapy (SBRT) may offer improved LC for circumferential vertebral and/or epidural metastatic spinal disease, but prospective (and retrospective) data are extremely limited. We sought to evaluate the feasibility, toxicity, and cancer control outcomes with this novel approach to circumferential spinal disease. Methods: We retrospectively identified all circumferential SBRT courses delivered between 2013 and 2019 at a tertiary care institution for post-operative or intact spine metastases. Radiotherapy was delivered to 14-27.5 Gy in one to five fractions. Feasibility was assessed by determining the proportion of plans for which ≥95% planning target volume (PTV) was coverable by ≥95% prescription dose. The primary endpoint was 1-year LC. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity were assessed. Detailed dosimetric data were collected. Results: Fifty-eight patients receiving 64 circumferential SBRT courses were identified (median age 61, KPS ≥70, 57% men). With a median follow-up of 15 months, the 12-month local control was 85% (eight events). Five and three recurrences were in the epidural space and bone, respectively. On multivariate analysis, increased PTV and uncontrolled systemic disease were significantly associated with an increased likelihood of LF; ≥95% PTV was covered by ≥95% prescription dose in 94% of the cases. The rate of new or progressive vertebral compression fracture was 8%. There were no myelitis events or any grade 3+ acute or late toxicities. Conclusions: For patients with circumferential disease, circumferential spine SBRT is feasible and may offer excellent LC without significant toxicity. A prospective evaluation of this approach is warranted.

Computational lumbar spine models: A literature review.

BACKGROUND: Computational spine models of various types have been employed to understand spine function, assess the risk that different activities pose to the spine, and evaluate techniques to prevent injury. The areas in which these models are applied has expanded greatly, potentially beyond the appropriate scope of each, given their capabilities. A comprehensive understanding of the components of these models provides insight into their current capabilities and limitations. METHODS: The objective of this review was to provide a critical assessment of the different characteristics of model elements employed across the spectrum of lumbar spine modeling and in newer combined methodologies to help better evaluate existing studies and delineate areas for future research and refinement. FINDINGS: A total of 155 studies met selection criteria and were included in this review. Most current studies use either highly detailed Finite Element models or simpler Musculoskeletal models driven with in vivo data. Many models feature significant geometric or loading simplifications that limit their realism and validity. Frequently, studies only create a single model and thus can't account for the impact of subject variability. The lack of model representation for certain subject cohorts leaves significant gaps in spine knowledge. Combining features from both types of modeling could result in more accurate and predictive models. INTERPRETATION: Development of integrated models combining elements from different model types in a framework that enables the evaluation of larger populations of subjects could address existing voids and enable more realistic representation of the biomechanics of the lumbar spine.

The Potential Relationship Between a Cognitive Dissonance State and Musculoskeletal Injury: A Systematic Review.

OBJECTIVE: The objective of this systematic review was to investigate the potential link between cognitive dissonance or its related constructs (emotional dissonance, emotional labor) and musculoskeletal disorders. BACKGROUND: The etiology of musculoskeletal disorders is complex, as pain arises from complex interactions among physical, social, and psychological stressors. It is possible that the psychological factor of cognitive dissonance may contribute to the etiology and/or maintenance of musculoskeletal disorders. METHOD: MEDLINE, APA PsycInfo, and CINAHL Plus databases were searched for studies investigating cognitive dissonance or its related constructs as exposure(s) of interest and outcomes related to physical health (including, but not limited to, musculoskeletal pain). Risk of bias was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS) tool. RESULTS: The literature search yielded 7 studies eligible for inclusion. None of the included studies investigated cognitive dissonance directly but instead investigated dissonance-related constructs of emotional dissonance and emotional labor, in which a mismatch between required and felt emotions might elicit a psychological response consistent with the cognitive dissonance state. Moderate effect sizes between dissonance-related constructs and musculoskeletal disorders were noted (OR 1.25-2.22). CONCLUSION: There is likely a relationship between the two factors studied. However, as the included studies were cross-sectional in nature, a causal relationship between cognitive dissonance-related constructs and musculoskeletal disorders cannot be inferred. Therefore, future study proposing and validating a causal pathway between these variables is warranted. APPLICATION: Cognitive dissonance and its related constructs may serve as risk factors for musculoskeletal disorders that have not been considered previously.

Quantitative dynamic wearable motion-based metric compared to patient-reported outcomes as indicators of functional recovery after lumbar fusion surgery.

BACKGROUND: Low back pain is a debilitating condition with poor patient outcomes despite the use of a wide variety of diagnostic and treatment modalities. A lack of objective metrics to support clinical decision-making may be a reason for these poor outcomes. This study aimed to compare patient recovery following lumbar fusion surgery using an objective motion-based metric (functional performance) and subjective patient-reported outcomes for pain, disability and kinesophobia. METHODS: A prospective observational study was conducted on 121 patients that received a lumbar fusion surgery. A wearable motion system was used to quantify three-dimensional multi-planar lumbar motion and benchmark each patient's lumbar function prior to surgery and post-operatively at follow-up time points for up to 2 years. Patient recovery profiles after surgery were evaluated using the acquired functional motion data and compared to patient-reported outcomes. FINDINGS: Our results found significant improvement after surgery in objective functional performance as well as patient-reported pain, disability, and kinesophobia. However, we found a delayed response in the objective metric, with meaningful improvement occurring only 6 months after fusion surgery. In contrast, we found significant improvement in all subjective scores as early as 6 weeks post-surgery. INTERPRETATION: Objective motion-based metric provides a unique perspective to assessing patient's functional recovery. While it is associated with dimensions of pain, disability and fear avoidance, it is also distinct and assesses a uniquely different dimension of functional health. This information can form the basis for the use of objective metrics to gauge patient recovery after lumbar fusion surgery.

Spine Stereotactic Body Radiotherapy to Three or More Contiguous Vertebral Levels.

Background: With survival improving in many metastatic malignancies, spine metastases have increasingly become a source of significant morbidity; achieving durable local control (LC) is critical. Stereotactic body radiotherapy (SBRT) may offer improved LC and/or symptom palliation. However, due to setup concerns, SBRT is infrequently offered to patients with ≥3 contiguous involved levels. Because data are limited, we sought to evaluate the feasibility, toxicity, and cancer control outcomes of spine SBRT delivered to ≥3 contiguous levels. Methods: We retrospectively identified all SBRT courses delivered between 2013 and 2019 at a tertiary care institution for postoperative or intact spine metastases. Radiotherapy was delivered to 14-35 Gy in 1-5 fractions. Patients were stratified by whether they received SBRT to 1-2 or ≥3 contiguous levels. The primary endpoint was 1-year LC and was compared between groups. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity was assessed. In-depth dosimetric data were collected. Results: Overall, 165 patients with 194 SBRT courses were identified [54% were men, median age was 61 years, 93% had Karnofsky Performance Status (KPS) ≥70, and median follow-up was 15 months]. One hundred thirteen patients (68%) received treatment to 1-2 and 52 to 3-7 (32%) levels. The 1-year LC was 88% (89% for 1-2 levels vs. 84% for ≥3 levels, p = 0.747). On multivariate analysis, uncontrolled systemic disease was associated with inferior LC for patients with ≥3 treated levels. No other demographic, disease, treatment, or dosimetric variables achieved significance. Rates of new/progressive fracture were equivalent (8% vs. 9.5%, p = 0.839). There were no radiation-induced myelopathy or grade 3+ acute or late toxicities in either group. Coverage of ≥95% of the planning target volume with ≥95% prescription dose was similar between groups (96% 1-2 levels vs. 89% ≥3 levels, p = 0.078). Conclusions: For patients with ≥3 contiguous involved levels, spine SBRT is feasible and may offer excellent LC without significant toxicity. Prospective evaluation is warranted.

Motion sickness decreases low back function and changes gene expression in military aircrew.

BACKGROUND: Motion sickness and low back disorders are prevalent and debilitating conditions that affect the health, performance, and operational effectiveness of military aircrews. This study explored the effects of a motion sickness stimulus on biomechanical and genetic factors that could potentially be involved in the causal pathways for both disorders. METHODS: Subjects recruited from a military population were exposed to either a mild (n = 12) or aggressive (n = 16) motion sickness stimulus in a Neuro-Otologic Test Center. The independent variable of interest was the motion sickness stimulus exposure (before vs. after), though differences between mild and aggressive stimuli were also assessed. Dependent measures for the study included motion sickness exposure duration, biomechanical variables (postural stability, gait function, low back function, lumbar spine loading), and gene expression. FINDINGS: Seven of twelve subjects experiencing the mild motion sickness stimulus endured the full 30 min in the NOTC, whereas subjects lasted an average of 13.2 (SD 5.0) minutes in the NOTC with the aggressive motion sickness stimulus. Mild motion sickness exposure led to a significant decrease in the postural stability measure of sway area, though the aggressive motion sickness exposure led to a statistically significant increase in sway area. Both stimuli led to decreases in low back function, though the decrease was only statistically significant for the mild protocol. Both stimuli also led to significant changes in gene expression. INTERPRETATION: Motion sickness may alter standing balance, decrease low back function, and lead to changes in the expression of genes with roles in osteogenesis, myogenesis, development of brain lymphatics, inflammation, neuropathic pain, and more. These results may provide preliminary evidence for a link between motion sickness and low back disorders.

Toward an artificial intelligence-assisted framework for reconstructing the digital twin of vertebra and predicting its fracture response.

This article presents an effort toward building an artificial intelligence (AI) assisted framework, coined ReconGAN, for creating a realistic digital twin of the human vertebra and predicting the risk of vertebral fracture (VF). ReconGAN consists of a deep convolutional generative adversarial network (DCGAN), image-processing steps, and finite element (FE) based shape optimization to reconstruct the vertebra model. This DCGAN model is trained using a set of quantitative micro-computed tomography (micro-QCT) images of the trabecular bone obtained from cadaveric samples. The quality of synthetic trabecular models generated using DCGAN are verified by comparing a set of its statistical microstructural descriptors with those of the imaging data. The synthesized trabecular microstructure is then infused into the vertebra cortical shell extracted from the patient's diagnostic CT scans using an FE-based shape optimization approach to achieve a smooth transition between trabecular to cortical regions. The final geometrical model of the vertebra is converted into a high-fidelity FE model to simulate the VF response using a continuum damage model under compression and flexion loading conditions. A feasibility study is presented to demonstrate the applicability of digital twins generated using this AI-assisted framework to predict the risk of VF in a cancer patient with spinal metastasis.

A digital twin for simulating the vertebroplasty procedure and its impact on mechanical stability of vertebra in cancer patients.

We present the application of ReconGAN, introduced in a previous study, for simulating the vertebroplasty (VP) operation and its impact on the fracture response of a vertebral body. ReconGAN consists of a Deep Convolutional Generative Adversarial Network (DCGAN) and a finite element based shape optimization algorithm to virtually reconstruct the trabecular bone microstructure. The VP procedure involves injecting shear-thinning liquid bone cement through a needle in the trabecular region to reinforce a diseased or fractured vertebra. To simulate this treatment modality, computational fluid dynamics (CFD) is employed to predict the morphology of the injected cement within the bone microstructure. A power-law equation is utilized to characterize the non-Newtonian shear-thinning behavior of the polymethyl methacrylate (PMMA) bone cement during injection simulations. The CFD model is coupled with the level-set method to simulate the motion of the interface separating bone cement and bone marrow. After predicting the cement morphology, a data co-registration algorithm is employed to transform the CFD model to a high-fidelity continuum damage mechanics (CDM) finite element model of the augmented vertebra for predicting the fracture response. A feasibility study is presented to demonstrate the ability of this CFD-CDM framework to investigate the effect of VP on the mechanical integrity of the vertebral body in a cancer patient with a lytic metastatic tumor.

Differences in lumbar spine measures as a function of MRI posture in low back pain patients and its clinical implications.

STUDY DESIGN: Observational Study. OBJECTIVE: The primary objective was to determine if there were differences in spine structure measures between experimental postures and standard supine posture MRIs. METHODS: Thirty-four low back pain patients were included. MRI was taken in 6 experimental postures. The dependent measures includes sagittal view anterior (ADH), middle and posterior disc heights, thecal sac width, left/right foraminal height (FH). In the axial view: disc width, left and right foraminal height. Measures were done L3/L4, L4/L5 and L5/S1. Each subject served as their own control. Spine measurements in the experimental posture were compared to the same measures in the standard supine posture. RESULTS: 94% inter-observer reliability was seen. In the sagittal and axial view, 55 of the 108 and 11 of the 18 measures were significantly different. In sagittal view: a) ADH was significantly smaller in the sitting flexed posture by 2.50 mm ± 0.63 compared to the supine posture; b) ADH in sitting neutral posture was significantly smaller than the standard posture by 1.97 mm ± 0.86; c) sitting flexed posture showed that bilateral FH measures were significantly different; d) Bilateral FH was larger in the sitting neutral posture compared to the standard supine posture by 0.87 mm ± 0.17. CONCLUSIONS: This research quantifies the differences in spine structure measures that occur in various experimental postures. The additional information gathered from an upright MRI may correlate with symptoms leading to an accurate diagnosis and assist in future spine research.

A physiological and biomechanical investigation of three passive upper-extremity exoskeletons during simulated overhead work.

The objective of this study was to evaluate three passive upper-extremity exoskeletons relative to a control condition. Twelve subjects performed an hour-long, simulated occupational task in a laboratory setting. Independent measures of exoskeleton, exertion height (overhead, head height), time, and their interactions were assessed. Dependent measures included changes in tissue oxygenation (ΔTSI) in the anterior deltoid and middle trapezius, peak resultant lumbar spine loading, and subjective discomfort in various body regions. A statistically significant reduction in ΔTSI between exoskeleton and control was only observed in one instance. Additionally, neither increases in spinal loading nor increases in subjective discomfort ratings were observed for any of the exoskeletons. Ultimately, the exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing to the subjects, denoted by low ΔTSI values across conditions. Results may vary for tasks requiring constant arm elevation or higher force demands. Practitioner summary This study quantified the benefits of upper-extremity exoskeletons using NIRS, complementary to prior studies using EMG. The exoskeletons offered little to no physiological benefit for the conditions tested. However, the experimental task was not highly fatiguing, and results may vary for an experimental task with greater demand on the shoulders. Abbreviations: WMSD: work-related musculoskeletal disorder; EMG: electromyography; NIRS: near-infrared spectroscopy; NIR: near-infrared; Hb: haemoglobin; Mb: myoglobin; TSI: tissue saturation index; ATT: adipose tissue thickness.

Neural and biomechanical tradeoffs associated with human-exoskeleton interactions.

Industrial passive low-back exoskeletons have gained recent attention as ergonomic interventions to manual handling tasks. This research utilized a two-armed experimental approach (single vs dual-task paradigms) to quantify neural and biomechanical tradeoffs associated with short-term human-exoskeleton interaction (HEI) during asymmetrical lifting in twelve healthy adults balanced by gender. A dynamic, electromyography-assisted spine model was employed that indicated statistical, but marginal, biomechanical benefits of the tested exoskeleton, which diminished with the introduction of the cognitive dual-task. Using Near Infrared Spectroscopy (fNIRS)-based brain connectivity analyses, we found that the tested exoskeleton imposed greater neurocognitive and motor adaptation efforts by engaging action monitoring and error processing brain networks. Collectively, these findings indicate that a wearer's biomechanical response to increased cognitive demands in the workplace may offset the mechanical advantages of exoskeletons. We also demonstrate the utility of ambulatory fNIRS to capture the neural cost of HEI without the need for elaborate dual-task manipulations.

Dynamic Joint Motions in Occupational Environments as Indicators of Potential Musculoskeletal Injury Risk.

The objective of this study was to test the feasibility of using a pair of wearable inertial measurement unit (IMU) sensors to accurately capture dynamic joint motion data during simulated occupational conditions. Eleven subjects (5 males and 6 females) performed repetitive neck, low-back, and shoulder motions simulating low- and high-difficulty occupational tasks in a laboratory setting. Kinematics for each of the 3 joints were measured via IMU sensors in addition to a "gold standard" passive marker optical motion capture system. The IMU accuracy was benchmarked relative to the optical motion capture system, and IMU sensitivity to low- and high-difficulty tasks was evaluated. The accuracy of the IMU sensors was found to be very good on average, but significant positional drift was observed in some trials. In addition, IMU measurements were shown to be sensitive to differences in task difficulty in all 3 joints (P < .05). These results demonstrate the feasibility for using wearable IMU sensors to capture kinematic exposures as potential indicators of occupational injury risk. Velocities and accelerations demonstrate the most potential for developing risk metrics since they are sensitive to task difficulty and less sensitive to drift than rotational position measurements.

Postoperative Stereotactic Body Radiotherapy for Spinal Metastasis and Predictors of Local Control.

BACKGROUND: Spine surgery is indicated for select patients with mechanical instability, pain, and/or malignant epidural spinal cord compression, with or without neurological compromise. Stereotactic body radiotherapy (SBRT) is an option for durable local control (LC) for metastatic spine disease. OBJECTIVE: To determine factors associated with LC and progression-free survival (PFS) for patients receiving postoperative stereotactic spine radiosurgery. METHODS: We analyzed consecutive patients from 2013 to 2019 treated with surgical intervention followed by SBRT. Surgical interventions included laminectomy and vertebrectomy. SBRT included patients treated with 1 to 5 fractions of radiosurgery. We analyzed LC, PFS, overall survival (OS), and toxicity. Univariate and multivariate analyses were performed. RESULTS: A total of 63 patients were treated with a median follow-up of 12.5 mo. Approximately 75% of patients underwent vertebrectomy and 25% underwent laminectomy. One-year cumulative incidence of local failure was 19%. LC was significantly improved for patients receiving radiosurgery ≤40 d from surgery compared to that for patients receiving radiosurgery ≥40 d from surgery, 94% vs 75%, respectively, at 1 yr (P = .03). Patients who received preoperative embolization had improved LC with 1-yr LC of 88% vs 76% for those who did not receive preoperative embolization (P = .037). Significant predictors for LC on multivariate analysis were time from surgery to radiosurgery, higher radiotherapy dose, and preoperative embolization. The 1-yr PFS and OS was 56% and 60%, respectively. CONCLUSION: Postoperative radiosurgery has excellent and durable LC for spine metastasis. An important consideration when planning postoperative radiosurgery is minimizing delay from surgery to radiosurgery. Preoperative embolization and higher radiotherapy dose were associated with improved LC warranting further study.

An electromyography-assisted biomechanical cervical spine model: Model development and validation.

BACKGROUND: In spite of the prevalence of occupational neck disorders as a result of work force fluctuating from industry to sedentary office work, most cervical spine computational models are not capable of simulating occupational and daily living activities whereas majority of cervical spine models specialized to simulate crash and impact scenarios. Therefore, estimating spine tissue loads accurately to quantify the risk of neck disorders in occupational environments within those models is not possible due to the lack of muscle models, dynamic simulation and passive spine structures. METHODS: In this effort the structure, logic, and validation process of an electromyography-assisted cervical biomechanical model that is capable of estimating neck loading under three-dimensional complex motions is described. The developed model was designed to simulate complex dynamic motions similar to work place exposure. Curved muscle geometry, personalized muscle force parameters, and separate passive and (electromyography-driven) active muscle force components are implemented in this model. FINDINGS: Calibration algorithms were able to reverse-engineer personalized muscle properties to calculate active and passive muscle forces of each individual. INTERPRETATION: This electromyography-assisted cervical spine model with curved muscle model is capable to accurately predict spinal tissue loads during isometric and dynamic head and neck activities. Personalized active and passive muscle force algorithms will help to more robustly investigate person-specific muscle forces and spinal tissue loads.

Comparison of push/pull force estimates using a single-axis gauge versus a three-dimensional hand transducer.

This study investigated the effects of using a single-axis force gauge for push/pull force measurement on kinetic/kinematic measures associated with the exertion and assessed agreement between forces recorded from two technologies (single-axis gauge, three-dimensional hand transducer) and various test conditions via intraclass correlations. Independent measures included exertion type (push, pull, turn), test condition (natural/cart alone, using force gauge at fast/slow/self-selected paces), and cart weight (light, heavy). Dependent measures included mean angles of force application, peak forces recorded from both technologies, and cart velocity. Excellent agreement was observed between technologies (ICC = 0.998). Likewise, peak forces using the single-axis gauge at the fast pace agreed best with the natural test condition (ICC = 0.631). Forces should be measured using a faster initial acceleration and sustained velocity than is prescribed by the current standard if they are to accurately approximate forces relative to existing push/pull guidelines. Future work should also develop recommendations for measuring turning forces.

Psychosocial Factors and Low Back Pain Outcomes in a Pooled Analysis of Low Back Pain Studies.

OBJECTIVE: Assessment of possible relationships between work-related psychosocial measures and self-reported low back pain (LBP) outcomes in a large pooled dataset of 1929 participants from 82 facilities in the United States. METHODS: Pooled data from three prospective cohort studies were used to calculate odds ratios (OR) and 95% confidence intervals (95% CI) for relationships between psychosocial factors and the LBP outcomes. Personal and occupational confounders were controlled for in adjusted Logistic regression models. RESULTS: Supervisor support and job satisfaction were significantly (P < 0.05) related to all three LBP outcomes. Other psychosocial factors were significantly (P < 0.05) associated with at least one of the LBP outcomes. Adjusted ORs ranged from approximately 1.50 to 3.50 for most associations. CONCLUSIONS: There is a significant relationship between work-related psychosocial measures and LBP outcomes.