Median nerve travel and deformation in the transverse carpal tunnel increases with chuck grip force and deviated wrist position

Abstract

Background We assessed median nerve travel and deformation concurrently to better understand the influence of occupational risk factors on carpal tunnel dynamics, including forceful chuck gripping and deviated wrist positions. Methods Fourteen healthy right-hand dominant participants performed a chuck grip in 6 experimental conditions: two relative force levels (10% and 40% of maximum voluntary effort); three wrist positions (15° radial deviation, 0° neutral, 30° ulnar deviation). Chuck grip forces were measured with a load cell while the transverse cross-section of the carpal tunnel was imaged via ultrasound at the distal wrist crease. Images of the median nerve were analyzed in ImageJ to assess cross-sectional area, circularity, width, and height as well as travel in the anterior-posterior and medial-lateral axes. Results We found a main effect of deviated wrist position on both anterior-posterior and medial-lateral travel, with the greatest nerve travel occurring in 30° ulnar deviation. There was also a significant interaction between chuck grip force and deviated wrist position on cross-sectional area. Specifically, the area decreased with 40% vs. 10% chuck grip force when the wrist was in 30° ulnar deviation; however, there were no changes in 0° neutral and 15° radial deviation. Discussion Overall, we demonstrated that forceful chuck gripping in deviated wrist positions influenced carpal tunnel dynamics, resulting in both migratory and morphological changes to the median nerve. These changes may, in turn, increase local strain and stress with adjacent structures in the carpal tunnel. Future studies mapping contact stress between structures may further elucidate injury development of work-related carpal tunnel syndrome.

Relative motion between the flexor digitorum superficialis tendon and subsynovial connective tissue is time dependent

“…However, the data for one participant was omitted due to equipment failure; therefore, the analyzed data set in this paper includes 11 participants. A survey was administered to screen for health conditions that influence tendon gliding in the carpal tunnel as exclusion criteria 23,24,27,34 . Participant characteristics were also documented, 35 which are reported in Table 1.…”

“…A survey was administered to screen for health conditions that influence tendon gliding in the carpal tunnel as exclusion criteria. 23,24,27,34 Participant characteristics were also documented, 35 which are reported in Table 1.…”

Time‐varying changes in median nerve deformation and position in response to quantified pinch and grip forces

“…For each MVF, maximal force was computed as a ±50 ms window centered on peak force, and an average of all three MVFs was calculated for each hand force exertion task. 25…”

“…20 Studies have assessed MN deformation during pinching and gripping tasks in healthy participants to further elucidate nerve mechanics in response to forceful efforts. [22][23][24][25][26][27] These studies included tasks where pinch and/or grip forces were either measured with a handheld dynamometer 22,25 or not directly quantified. 23,24,26,27 Loh et al 23 investigated MN deformation in three wrist postures (30°flexion, 0°neutral, 30°extension) with the fingers relaxed and while forming both an unclenched and clenched fist.…”

“…22 While studies have quantified the relationships between forceful efforts and MN deformation, researchers have utilized a framework where a single image was extracted to represent each forceful effort as the participant sustained an isometric target force. [22][23][24][25][26][27]…”