Abstract
The present study investigated the effects of grip on changes in the median nerve cross-sectional area (MNCSA) and median nerve diameter in the radial-ulnar direction (D1) and dorsal-palmar direction (D2) at three wrist angles. Twenty-nine healthy participants (19 men [mean age, 24.2 ± 1.6 years]; 10 women [mean age, 24.0 ± 1.6 years]) were recruited. The median nerve was examined at the proximal carpal tunnel region in three grip conditions, namely finger relaxation, unclenched fist, and clenched fist. Ultrasound examinations were performed in the neutral wrist position (0°), at 30°wrist flexion, and at 30°wrist extension for both wrists. The grip condition and wrist angle showed significant main effects (p < 0.01) on the changes in the MNCSA, D1, and D2. Furthermore, significant interactions (p < 0.01) were found between the grip condition and wrist angle for the MNCSA, D1, and D2. In the neutral wrist position (0°), significant reductions in the MNCSA, D1, and D2 were observed when finger relaxation changed to unclenched fist and clenched fist conditions. Clenched fist condition caused the highest deformations in the median nerve measurements (MNCSA, approximately −25%; D1, −13%; D2, −12%). The MNCSA was significantly lower at 30°wrist flexion and 30°wrist extension than in the neutral wrist position (0°) at unclenched fist and clenched fist conditions. Notably, clenched fist condition at 30°wrist flexion showed the highest reduction of the MNCSA (−29%). In addition, 30°wrist flexion resulted in a lower D1 at clenched fist condition. In contrast, 30°wrist extension resulted in a lower D2 at both unclenched fist and clenched fist conditions. Our results suggest that unclenched fist and clenched fist conditions cause reductions in the MNCSA, D1, and D2. More importantly, unclenched fist and clenched fist conditions at 30°wrist flexion and 30°wrist extension can lead to further deformation of the median nerve.
Highlights
Carpal tunnel syndrome (CTS) is one of the most common peripheral neuropathies associated with socioeconomic burden (Palmer, Harris & Coggon, 2007) and the quality of life of CTS patients has been shown to be affected by the clinical symptoms of CTS (Atroshi et al, 1999)
The median nerve cross-sectional area (MNCSA) significantly reduced as finger relaxation changed to unclenched fist and clenched fist conditions at all three wrist angles (Fig. 3A)
We found a significant reduction in the MNCSA as the fingers changed from finger relaxation to unclenched fist condition (Fig. 3A), which may have resulted from mechanical stress arising from the radial-ulnar displacement of the finger flexor tendons within the carpal tunnel (Van Doesburg et al, 2010)
Summary
Carpal tunnel syndrome (CTS) is one of the most common peripheral neuropathies associated with socioeconomic burden (Palmer, Harris & Coggon, 2007) and the quality of life of CTS patients has been shown to be affected by the clinical symptoms of CTS (Atroshi et al, 1999). The non-neutral wrist posture has been shown to be associated with an overall high risk of CTS (You, Smith & Rempel, 2014). Wrist flexion and extension movements cause three-dimensional displacement of the median nerve and finger flexor tendons, namely proximal-distal, radial-ulnar, and dorsal-palmar displacements (Canuto et al, 2006; Wang et al, 2014; Yoshii et al, 2008; Yoshii et al, 2013). In response to the contact pressure arising from finger flexor tendon displacement, the median nerve deforms in order to adapt to the biomechanical stress (Wang et al, 2014). Deformations of the cross-sectional area and diameter of the median nerve have been reported with changes in wrist posture and finger movement via ultrasound studies (Loh, Nakashima & Muraki, 2015; Loh & Muraki, 2015; Wang et al, 2014; Yoshii et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
