The effect of hand position on perceived finger orientation in left- and right-handers

The Influence of Hand Dominance in Wrist Fracture Post-Operative Functional Evaluation

Sensorimotor testing is used to measure outcomes in surgery, to document results of treatment and rehabilitation, and to compare results between surgeons, therapists, and institutions. When performing sensorimotor testing, failure to address dominant side differences may cause a bias in evaluation of outcomes. This study evaluated the effect of hand dominance on outcomes testing performed on patients following surgery for distal radius fractures (DRF). We hypothesized that the injured dominant hand will perform differently than the injured non-dominant hand. This is a retrospective study of patients following DRF treated surgically and evaluated in therapy. The patients were evaluated at fixed intervals: initially, at 6 weeks, and at 3 months post-surgery. Testing included grip strength, monofilaments, static and moving 2-point discrimination, Moberg testing, and stereognosis. Sixty patients included 46 (76.6%) females. Age averaged 62.1 (standard deviation: 16.9) years, and 54 were right-handed (90%). There were differences between dominant and non-dominant hand injury in 2 of 9 tests of sensibility for each time period, including little finger monofilament and Moberg testing initially, and moving 2-point discrimination in the little finger, monofilament testing of the thumb at 3 months. Both groups improved between initial and 3-month evaluation without differences in amount of improvement. Despite some significant differences in the applied tests between dominant and non-dominant injured hands, our results do not support correction for hand-dominance when using the described examinations in evaluating outcomes following DRF surgery.

The signing body: extensive sign language practice shapes the size of hands and face

The representation of the metrics of the hands is distorted, but is susceptible to malleability due to expert dexterity (magicians) and long-term tool use (baseball players). However, it remains unclear whether modulation leads to a stable representation of the hand that is adopted in every circumstance, or whether the modulation is closely linked to the spatial context where the expertise occurs. To this aim, a group of 10 experienced Sign Language (SL) interpreters were recruited to study the selective influence of expertise and space localisation in the metric representation of hands. Experiment 1 explored differences in hands’ size representation between the SL interpreters and 10 age-matched controls in near-reaching (Condition 1) and far-reaching space (Condition 2), using the localisation task. SL interpreters presented reduced hand size in near-reaching condition, with characteristic underestimation of finger lengths, and reduced overestimation of hands and wrists widths in comparison with controls. This difference was lost in far-reaching space, confirming the effect of expertise on hand representations is closely linked to the spatial context where an action is performed. As SL interpreters are also experts in the use of their face with communication purposes, the effects of expertise in the metrics of the face were also studied (Experiment 2). SL interpreters were more accurate than controls, with overall reduction of width overestimation. Overall, expertise modifies the representation of relevant body parts in a specific and context-dependent manner. Hence, different representations of the same body part can coexist simultaneously.

Force distribution of a cylindrical grip differs between dominant and nondominant hand in healthy subjects

INTRODUCTION

Grip strength and load distribution of the hand are important parameters for evaluating hand function. The purpose of this study was to analyze and compare grip force and load distribution of dominant and nondominant hands in right-handed healthy subjects.

METHODS

Gripping measurements were performed on 40 healthy right-handed subjects using a cylindrical gripping device. Two different cylinders with circumferences of 150 mm (small cylinder) and 200 mm (large cylinder), respectively, were used for the measurements. Subjects were assigned to either the small or the large cylinder with respect to their hand size. Maximum and mean force applied during three intervals of gripping as well as the percent contribution of each digit, thenar, and hypothenar in relation to the total load applied were acquired. Values of dominant and nondominant hands were compared.

RESULTS

Percent contribution of mean grip strength differed for the thumb (p = 0.007), ring finger (p < 0.001), little finger (p = 0.047), and palm (p < 0.001). Comparing the dominant and nondominant side, the dominant hand showed a lower contribution of the thumb, ring finger, and little finger, but a higher contribution of the palm. When analyzing maximum grip, percent contribution of the small fingers was equal between dominant and nondominant side (p = 0.1). Differences between dominant and nondominant thumb, ring finger, and palm persisted (p = 0.007, p = 0.001, p = 0.005, respectively). No differences could be shown for the index finger, middle finger, thenar, and hypothenar when analyzing both mean and maximum force.

DISCUSSION AND CONCLUSION

Percent contribution of the thumb and the fingers to total grip strength differed between dominant and nondominant hands with a change in distribution when assessing maximum grip force. In right-handed subjects, thumb and ring finger have important roles during gripping.