Development of Kinematic Graphs of Median Nerve during Active Finger Motion: Implications of Smartphone Use

Abstract

BackgroundCertain hand activities cause deformation and displacement of the median nerve at the carpal tunnel due to the gliding motion of tendons surrounding it. As smartphone usage escalates, this raises the public’s concern whether hand activities while using smartphones can lead to median nerve problems.ObjectiveThe aims of this study were to 1) develop kinematic graphs and 2) investigate the associated deformation and rotational information of median nerve in the carpal tunnel during hand activities.MethodsDominant wrists of 30 young adults were examined with ultrasonography by placing a transducer transversely on their wrist crease. Ultrasound video clips were recorded when the subject performing 1) thumb opposition with the wrist in neutral position, 2) thumb opposition with the wrist in ulnar deviation and 3) pinch grip with the wrist in neutral position. Six still images that were separated by 0.2-second intervals were then captured from the ultrasound video for the determination of 1) cross-sectional area (CSA), 2) flattening ratio (FR), 3) rotational displacement (RD) and 4) translational displacement (TD) of median nerve in the carpal tunnel, and these collected information of deformation, rotational and displacement of median nerve were compared between 1) two successive time points during a single hand activity and 2) different hand motions at the same time point. Finally, kinematic graphs were constructed to demonstrate the mobility of median nerve during different hand activities.ResultsPerforming different hand activities during this study led to a gradual reduction in CSA of the median nerve, with thumb opposition together with the wrist in ulnar deviation causing the greatest extent of deformation of the median nerve. Thumb opposition with the wrist in ulnar deviation also led to the largest extent of TD when compared to the other two hand activities of this study. Kinematic graphs showed that the motion pathways of median nerve during different hand activities were complex.ConclusionWe observed that the median nerve in the carpal tunnel was rotated, deformed and displaced during the hand activities that people may be performed when using a smartphone, suggesting an increased risk of carpal tunnel syndrome (CTS). In addition, the kinematic graphs of median nerve developed in the present study provide new clues for further studies on the pathophysiology of CTS, and alerting smartphone users to establish proper postural habits when using handheld electronic devices.

Effects of electronic device overuse by university students in relation to clinical status and anatomical variations of the median nerve and transverse carpal ligament

“…Smartphones and tablet computers involve thumb or finger interactions with the screen. Although these activities are generally not physically rigorous, prolonged periods of repetitive motion could lead to excessive force being exerted on the median nerve, thereby compressing it . A recent study found that, on average, students use electronic devices over 3 h per day and report musculoskeletal complaints.…”

“…Although these activities are generally not physically rigorous, prolonged periods of repetitive motion could lead to excessive force being exerted on the median nerve, thereby compressing it. 2 A recent study found that, on average, students use electronic devices over 3 h per day 3 and report musculoskeletal complaints. In addition, use of electronic devices compels users to engage in extension/flexion and radial/ulnar deviation of the wrist.…”

Effect of Bilateral Versus Unilateral Use of Smartphone on Cross Sectional Area of Median Nerve

“…An ultrasound transducer was placed transversely at the level of carpal tunnel the ultrasound transducer was carefully held without applying any pressure on the participant's skin, and was maintained at an angle perpendicular to the median nerve. Median nerve CSA was determined by performing a boundary trace along the border between the hypoechoic inner median nerve and the hyperechoic outer epineurium [13] .…”

“…All participants were requested to sit on a chair facing the examiner with shoulder slightly abducted, the elbow of dominant hand flexed approximately at 90, forearm rested on the table in partially supinated (approximately 45º) to enable them to assume a posture generally applied when using a smartphone for text messaging. During the ultrasound examination, participants were instructed to move their thumb and keep other parts of the hand still when writing on smartphone [13,14] .…”

The effect of smartphone usage on the upper extremity performance among Saudi Youth, KSA

“…The current study findings are consistent with Inal et al 19 who found that Visual Analogue Scale (VAS) pain in movement was also found to be significantly higher in the high smartphone-user group than in the lower smartphone-user group. In 2006, Woo et al found that ulnar and radial deviations are negatively affected by the prolonged usage of smartphones 20 . They have reported that the gradual reduction in the cross sectional area of the median nerve, with thumb opposition together with the wrist in ulnar deviation, cause the greatest extent of deformation of the median nerve.…”