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Jennifer A. Nichols, Michael S. Bednar, Robert M. Havey, and Wendy M. Murray

At the wrist, kinematic coupling (the relationship between flexion-extension and radial-ulnar deviation) facilitates function. Although the midcarpal joint is critical for kinematic coupling, many surgeries, such as 4-corner fusion (4CF) and scaphoidexcision 4-corner fusion (SE4CF), modify the midcarpal joint. This study examines how 4CF and SE4CF influence kinematic coupling by quantifying wrist axes of rotation. Wrist axes of rotation were quantified in 8 cadaveric specimens using an optimization algorithm, which fit a 2-revolute joint model to experimental data. In each specimen, data measuring the motion of the third metacarpal relative to the radius was collected for 3 conditions (nonimpaired, 4CF, SE4CF). The calculated axes of rotation were compared using spherical statistics. The angle between the axes of rotation was used to assess coupling, as the nonimpaired wrist has skew axes (ie, angle between axes approximately 60°). Following 4CF and SE4CF, the axes are closer to orthogonal than those of the nonimpaired wrist. The mean angle (±95% confidence interval) between the axes was 92.6° ± 25.2° and 99.8° ± 22.0° for 4CF and SE4CF, respectively. The axes of rotation defined in this study can be used to define joint models, which will facilitate more accurate computational and experimental studies of these procedures.

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Howard J. Hillstrom, Rohit Garg, Andrew Kraszewski, Mark Lenhoff, Timothy Carter, Sherry I. Backus, Aviva Wolff, Grigory Syrkin, Richard Cheng, and Scott W. Wolfe

The purpose of this study was to develop a three-dimensional (3D) motion analysis based anatomical wrist joint coordinate system for measurement of in-vivo wrist kinematics. The convergent validity and reliability of the 3D motion analysis implementation was quantified and compared with manual and electrogoniometry techniques on 10 cadaveric specimens. Fluoroscopic measurements were used as the reference. The 3D motion analysis measurements (mean absolute difference [MAD] = 3.6°) were significantly less different (P < .005) than manual goniometry (MAD = 5.7°) but not (P = .066, power = 0.45) electrogoniometry (MAD = 5.0°) compared with fluoroscopy. The intraclass correlation coefficient (ICC[2,1]) was highest for 3D motion analysis compared with manual and electrogoniometry, suggesting better reliability for this technique. To demonstrate the utility of this new wrist joint coordinate system, normative data from 10 healthy subjects was obtained while throwing a dart.

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Jennifer Di Domizio, Jeremy P.M. Mogk, and Peter J. Keir

Wrist splints are commonly prescribed to limit wrist motion and provide support at night and during inactive periods but are often used in the workplace. In theory, splinting the wrist should reduce wrist extensor muscle activity by stabilizing the joint and reducing the need for co-contraction to maintain posture. Ten healthy volunteers underwent a series of 24 10-s gripping trials with surface electromyography on 6 forearm muscles. Trials were randomized between splinted and nonsplinted conditions with three wrist postures (30° flexion, neutral, and 30° extension) and four grip efforts. Custom-made Plexiglas splints were taped to the dorsum of the hand and wrist. It was found that when simply holding the dynamometer, use of a splint led to a small (<1% MVE) but significant reduction in activity for all flexor muscles and extensor carpi radialis (all activity <4% maximum). At maximal grip, extensor muscle activity was significantly increased with the splints by 7.9–23.9% MVE. These data indicate that splinting at low-to-moderate grip forces may act to support the wrist against external loading, but appears counterproductive when exerting maximal forces. Wrist bracing should be limited to periods of no to light activity and avoided during tasks that require heavy efforts.

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Matthew B.A. McCullough, Brian D. Adams, and Nicole M. Grosland

Third-generation total wrist arthroplasty devices have provided joint stability, relief from pain and increased wrist motion for patients suffering from severe arthritis. While reports of clinical follow-up appointments describe improved wrist function, the improvement in overall upper extremity function and patient perception remains a question. Therefore, the purpose of this study was to assess the upper extremity function in patients that received the Universal 2 total implant system. Eight patients participated in the complete protocol, which included testing activities of daily living as well as surveys to assess patient perception. The findings of the current study suggest that although patients exhibit motion that exceeds the needed amount, many still have a perceived disability.

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Niranjan Chakrabhavi and Varadhan SKM

to the fingers around the wrist joint. Therefore, it is possible that the mechanical configuration of the wrist could play a causal role in finger interdependence. One way to induce a change in mechanical configuration is by changing the wrist posture. It has been shown that the wrist flexion alters

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Barıs Seven, Gamze Cobanoglu, Deran Oskay, and Nevin Atalay-Guzel

proprioception sense can provide better function and decrease the risk and incidence of injuries. 2 If the deficit of proprioception sense is noticed beforehand, possible injuries can be avoided thanks to proprioceptive exercise program. 3 The evaluation of the wrist strength and proprioception gives clinicians

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Susan Park, Lindsay P. Toth, Paul R. Hibbing, Cary M. Springer, Andrew S. Kaplan, Mckenzie D. Feyerabend, Scott E. Crouter, and David R. Bassett

ambulatory PA ( Bassett, Toth, LaMunion, & Crouter, 2017 ). Historically, hip-worn monitors have been used to assess steps per day ( Iwane et al., 2000 ; Swartz et al., 2003 ; Yamanouchi et al., 1995 ). However, wrist-worn monitors have become increasingly popular among consumers and researchers ( Evenson

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Sarah G. Sanders, Elizabeth Yakes Jimenez, Natalie H. Cole, Alena Kuhlemeier, Grace L. McCauley, M. Lee Van Horn, and Alberta S. Kong

US children using waist-worn accelerometers, 8% of adolescents ages 12–15 years engaged in 60 minutes or more of MVPA on at least 5 of 7 days. 5 More recently, PA researchers have begun reporting data from accelerometers worn on the wrist. In 2011, National Health and Nutrition Examination Survey

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Joshua Twaites, Richard Everson, Joss Langford, and Melvyn Hillsdon

training data, that can predict the activity type performed based on the acceleration data ( Staudenmayer et al., 2009 ; Bao & Intille, 2004 ). The earliest examples of using machine learning to classify activity via acceleration used networks of accelerometers placed around the body (wrists, ankles

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Marcin Straczkiewicz, Nancy W. Glynn, Vadim Zipunnikov, and Jaroslaw Harezlak

Wearable accelerometers are increasingly used in large free-living epidemiological studies for quantification of physical activity and sedentary behavior (SB). This is particularly true for the wrist-worn sensors. Compared with other frequently used body locations, like the thigh or waist, the