Monitoring Activity and Gait in Children (MAGIC) using digital health technologies.

BACKGROUND: Digital health technologies (DHTs) can collect gait and physical activity in adults, but limited studies have validated these in children. This study compared gait and physical activity metrics collected using DHTs to those collected by reference comparators during in-clinic sessions, to collect a normative accelerometry dataset, and to evaluate participants' comfort and their compliance in wearing the DHTs at-home. METHODS: The MAGIC (Monitoring Activity and Gait in Children) study was an analytical validation study which enrolled 40, generally healthy participants aged 3-17 years. Gait and physical activity were collected using DHTs in a clinical setting and continuously at-home. RESULTS: Overall good to excellent agreement was observed between gait metrics extracted with a gait algorithm from a lumbar-worn DHT compared to ground truth reference systems. Majority of participants either "agreed" or "strongly agreed" that wrist and lumbar DHTs were comfortable to wear at home, respectively, with 86% (wrist-worn DHT) and 68% (lumbar-worn DHT) wear-time compliance. Significant differences across age groups were observed in multiple gait and activity metrics obtained at home. CONCLUSIONS: Our findings suggest that gait and physical activity data can be collected from DHTs in pediatric populations with high reliability and wear compliance, in-clinic and in home environments. TRIAL REGISTRATION: ClinicalTrials.gov: NCT04823650 IMPACT: Digital health technologies (DHTs) have been used to collect gait and physical activity in adult populations, but limited studies have validated these metrics in children. The MAGIC study comprehensively validates the performance and feasibility of DHT-measured gait and physical activity in the pediatric population. Our findings suggest that reliable gait and physical activity data can be collected from DHTs in pediatric populations, with both high accuracy and wear compliance both in-clinic and in home environments. The identified across-age-group differences in gait and activity measurements highlighted their potential clinical value.

Movement compensation is driven by the deltoid and teres minor muscles following severe rotator cuff tear.

BACKGROUND: Rotator cuff tears are common in older adults, negatively affecting function. Previous simulation-based studies reported more posterior and superior oriented glenohumeral loading with increased cuff tear severity and task performance, although corresponding muscle compensation strategies are unclear. Our objective is to determine how shoulder muscle forces change with increased rotator cuff tear severity during functional task performance. METHODS: Eight musculoskeletal models of increasing tear severity were developed to represent no rotator cuff tear to massive three-tendon tears. Simulations were performed using each combination of model and kinematics for five functional tasks. Individual muscle forces were averaged for each task and tear severity, then normalized by the sum of the muscle forces across the shoulder. Forces were compared across tear severity and muscle. FINDINGS: For muscle force contribution, interactions between tear severity and muscle and a main effect of muscle were seen for all tasks (P < 0.0001). Middle deltoid increased force contribution by >10% in the greatest tear severity model compared to no cuff tear model for all tasks (all P < 0.0001). Teres minor contribution increased by 7.7%, 5.6%, and 11% in the greatest tear severity model compared to the no cuff tear model for forward reach, axilla wash, and upward reach 105° tasks, respectively (all P < 0.0001). INTERPRETATION: Functional tasks elicit compensatory responses from uninjured muscles following severe cuff tears, notably in middle deltoid and teres minor, leading to posterior-superior glenohumeral loading. The muscles are potential targets for strengthening to avoid injury from sustained increased muscle force.

Glenohumeral joint loading is impacted by rotator cuff tear severity during functional task performance.

BACKGROUND: Rotator cuff tear is a common musculoskeletal injury, negatively affecting shoulder function. Rotator cuff tear severity ranges from small to massive tears, but it is unclear how tear severity affects glenohumeral joint loading and how changes contribute to secondary injury. This study's objective was to determine how glenohumeral joint contact force changes with tear severity during functional task performance using computational models. METHODS: Eight models of increasing tear severity were developed, ranging from no rotator cuff tear to massive three-tendon tears. Simulations were performed using models representing increasing tear severity and kinematics for five functional tasks (n = 720 simulations). For each task, magnitude and orientation of peak resultant joint contact force for each tear severity was identified, then compared to the no rotator cuff tear model. FINDINGS: For all tasks, compared to the no rotator cuff tear model, joint contact force magnitude decreased 9.5% on average with infraspinatus involvement, then plateaued at 20.8% average decrease with subscapularis involvement. Projected orientation of peak joint contact force vector was located more superior in the glenoid with increased tear severity, with significant changes (p < 0.0003) for all tasks with infraspinatus involvement. INTERPRETATION: Decreased magnitude and superior orientation of joint contact force suggest fewer intact muscles contribute to force distribution across the joint, although more work is needed characterizing associated compensation strategies. All force vectors remained oriented within the glenoid rim for all tasks and models, suggesting the system prioritizes joint stability. This work identifies how joint contact force changes with rotator cuff tear severity.