Effect of wrist posture on carpal tunnel pressure while typing

Department of Medicine, University of California, San Francisco, California, USA.
Journal of Orthopaedic Research (Impact Factor: 2.99). 09/2008; 26(9):1269-73. DOI: 10.1002/jor.20599
Source: PubMed


Long weekly hours of keyboard use may lead to or aggravate carpal tunnel syndrome. The effects of typing on fluid pressure in the carpal tunnel, a possible mediator of carpal tunnel syndrome, are unknown. Twenty healthy subjects participated in a laboratory study to investigate the effects of typing at different wrist postures on carpal tunnel pressure of the right hand. Changes in wrist flexion/extension angle (p = 0.01) and radial/ulnar deviation angle (p = 0.03) independently altered carpal tunnel pressure; wrist deviations in extension or radial deviation were associated with an increase in pressure. The activity of typing independently elevated carpal tunnel pressure (p = 0.001) relative to the static hand held in the same posture. This information can guide the design and use of keyboards and workstations in order to minimize carpal tunnel pressure while typing. The findings may also be useful to clinicians and ergonomists in the management of patients with carpal tunnel syndrome who use a keyboard.

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Available from: David Rempel
    • "Because the catheter was in place during the mouse tasks and because four different conditions were evaluated, we limited the duration of each mouse task to 5 min. We have no reasons to assume that the findings would have been different when evaluation periods would have been longer, especially since it has been reported that the initial increase in pressure with prolonged keyboard use changes only little over a 4 h period (Rempel et al., 2008). Considering the distinct configuration of the vertical mouse, the relativelyshort familiarisation period and task duration may have contributed to the polarisation in comfort rating for this condition. "
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    ABSTRACT: Non-neutral wrist positions and external pressure leading to increased carpal tunnel pressure during computer use have been associated with a heightened risk of carpal tunnel syndrome (CTS). This study investigated whether commonly used ergonomic devices reduce carpal tunnel pressure in patients with CTS. Carpal tunnel pressure was measured in twenty-one patients with CTS before, during and after a computer mouse task using a standard mouse, a vertical mouse, a gel mouse pad and a gliding palm support. Carpal tunnel pressure increased while operating a computer mouse. Although the vertical mouse significantly reduced ulnar deviation and the gel mouse pad and gliding palm support decreased wrist extension, none of the ergonomic devices reduced carpal tunnel pressure. The findings of this study do therefore not endorse a strong recommendation for or against any of the ergonomic devices commonly recommended for patients with CTS. Selection of ergonomic devices remains dependent on personal preference.
    No preview · Article · Mar 2015 · Applied Ergonomics
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    • "Biomechanically these non-neutral postures can increase internal loading on the muscles and joints. Rempel et al. (2008) reported that changes in wrist posture altered carpal tunnel pressure, which may contribute to the development or aggravation of carpal tunnel syndrome (Rempel et al., 1999, 2008). Specifically, wrist deviations in extension or radial deviation while typing are associated with an increase in pressure. "
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    ABSTRACT: Non-neutral wrist posture is a risk factor of the musculoskeletal disorders among computer users. This study aimed to assess internal loads on hand and forearm musculature while tapping in different wrist postures. Ten healthy subjects tapped on a key switch using their index finger in four wrist postures: straight, ulnar deviated, flexed and extended. Torque at the finger and wrist joints were calculated from measured joint postures and fingertip force. Muscle stresses of the six finger muscles and four wrist muscles that balanced the calculated joint torques were estimated using a musculoskeletal model and optimization algorithm minimizing the squared sum of muscle stress. Non-neutral wrist postures resulted in greater muscle stresses than the neutral (straight) wrist posture, and the stress in the extensor muscles were greater than the flexors in all conditions. Wrist extensors stress remained higher than 4.5 N/cm² and wrist flexor stress remained below 0.5 N/cm² during tapping. The sustained high motor unit recruitment of extensors suggests a greater risk than other muscles especially in flexed wrist posture. This study demonstrated from the perspective of internal tissue loading the importance of maintaining neutral wrist posture during keying activities.
    Full-text · Article · Apr 2013 · Applied ergonomics
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    • "The impact of wrist, forearm and finger position on carpal tunnel pressure and the impact of fingertip loading (e.g., pinch grip) have been well-documented for both healthy participants and patients with CTS (Seradge et al., 1995; Keir et al., 1998b). However, the impact of many functional tasks, such as typing (Rempel et al., 2008) and computer mouse operation (Keir et al., 1999), has only been investigated for healthy people. With respect to the effect of non-invasive treatment, only the effect of wearing a splint has been investigated. "
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    ABSTRACT: Elevated carpal tunnel pressure is an important pathomechanism in carpal tunnel syndrome (CTS). Several invasive methods have been described for direct measurement of carpal tunnel pressure, but all have two important limitations. The pressure gauge requires sterilisation between uses, which makes time-efficient data collection logistically cumbersome, and more importantly, the reliability of carpal tunnel pressure measurements has not been evaluated for any of the methods in use. This technical note describes a new method to measure carpal tunnel pressure using inexpensive, disposable pressure sensors and reports the within and between session reliability of the pressure recordings in five different wrist positions and during typing and computer mouse operation. Intraclass correlation coefficients (ICC[3,1]) were calculated for recordings within one session for healthy participants (n = 7) and patients with CTS (n = 5), and for recordings between two sessions for patients with CTS (n = 5). Overall, the reliability was high. With the exception of two coefficients, the reliability of the recordings at different wrist angles varied from 0.63 to 0.99. Reliability for typing and mouse operation ranged from 0.86 to 0.99. The new method described in this report is inexpensive and reliable, and data collection can be applied more efficiently as off-site sterilisation of equipment is not required. These advances are likely to promote future research into carpal tunnel pressure, such as investigation of the therapeutic mechanisms of various conservative treatment modalities that are believed to reduce elevated carpal tunnel pressure.
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