Most motion capture measurements suffer from soft-tissue artifacts (STA). Especially affected are rotations about the long axis of a limb segment, such as humeral internal-external rotation (HIER) and forearm pronation-supination (FPS). Unfortunately, most existing methods to compensate for STA were designed for optoelectronic motion capture systems. We present and evaluate a STA compensation method that 1) compensates for STA in HIER and/or FPS, 2) is developed specifically for electromagnetic motion capture systems, and 3) does not require additional calibration or data. To compensate for STA, calculation of HIER angles rely on forearm orientation, and calculation of FPS angles rely on hand orientation. To test this approach, we recorded whole-arm movement data from eight subjects and compared their joint angle trajectories calculated according to progressive levels of STA compensation. Compensated HIER and FPS angles were significantly larger than uncompensated angles. Although the effect of STA compensation on other joint angles (besides HIER and FPS) was usually modest, significant effects were seen in certain DOF under some conditions. Overall, the method functioned as intended during most of the range of motion of the upper limb, but it becomes unstable in extreme elbow extension and extreme wrist flexion-extension. Specifically, this method is not recommended for movements within 20° of full elbow extension, full wrist flexion, or full wrist extension. Since this method does not require additional calibration of data, it can be applied retroactively to data collected without the intent to compensate for STA.

Electromagnetic (EM) motion tracking systems are suitable for many research and clinical applications, including in vivo measurements of whole-arm movements. Unfortunately, the methodology for in vivo measurements of whole-arm movements using EM sensors is not well described in the literature, making it difficult to perform new measurements and all but impossible to make meaningful comparisons between studies. The recommendations of the International Society of Biomechanics (ISB) have provided a great service, but by necessity they do not provide clear guidance or standardization on all required steps. The goal of this paper was to provide a comprehensive methodology for using EM sensors to measure whole-arm movements in vivo. We selected methodological details from past studies that were compatible with the ISB recommendations and suitable for measuring whole-arm movements using EM sensors, filling in gaps with recommendations from our own past experiments. The presented methodology includes recommendations for defining coordinate systems (CSs) and joint angles, placing sensors, performing sensor-to-body calibration, calculating rotation matrices from sensor data, and extracting unique joint angles from rotation matrices. We present this process, including all equations, for both the right and left upper limbs, models with nine or seven degrees-of-freedom (DOF), and two different calibration methods. Providing a detailed methodology for the entire process in one location promotes replicability of studies by allowing researchers to clearly define their experimental methods. It is hoped that this paper will simplify new investigations of whole-arm movement using EM sensors and facilitate comparison between studies.

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INTRODUCTION:With increasing numbers of advanced maternal age (AMA) gravidas, labor characteristics specific to this population are important to understand. The objective of this study was to examine patterns in cervical ripening times and vaginal delivery rates for patients with AMA.METHODS:This was an IRB-approved retrospective cohort study conducted at a single academic center. Data were collected by retrospective chart review of deliveries from 2020 to 2021. We included nulliparous patients aged 18 or older with singleton pregnancies, pre-pregnancy body mass index of 18.5 or greater, and gestational age of 37.0 or greater. Patients with pregestational diabetes and lethal fetal anomalies were excluded.RESULTS:One thousand twenty-two patients met inclusion and exclusion criteria, 17.7% of whom were AMA. Lower gestational age and less Hispanic ethnicity were noted in the AMA group. Among AMA patients, there was an increase in cervical ripening time as compared to patients aged older than 35 with an average difference of 3.14 hours (CI 1.26–5.01, P=.001). Compared to participants younger than 35, those that are AMA were 36% less likely to have a vaginal delivery (CI 0.46–0.89, P=.008). Median cervical ripening time to vaginal delivery was 15.0 hours for non-AMA and 19.9 hours for AMA patients. At any point of cervical dilation, AMA patients had a 28% less chance to have a vaginal delivery than non-AMA (P<.001).CONCLUSION:Patients who were AMA experienced increased cervical ripening times and decreased rates of vaginal deliveries compared to patients younger than 35. Knowing labor characteristics specific to the AMA population is important for counseling and clinical decision-making.

AMA patients. At any point of cervical dilation, AMA patients had a 28% less chance to have a vaginal delivery than non-AMA (P,.001).CONCLUSION: Patients who were AMA experienced increased cervical ripening times and decreased rates of vaginal deliveries compared to patients younger than 35. Knowing labor characteristics specific to the AMA population is important for counseling and clinical decision-making.