Mode of median nerve irritation under different wrist forcing postures observed by ultrasonography and foot pressure measurement system

Abstract

Objective: To analyze the influence of simulation mouse use motion under different wrist forcing postures on median nerve, tendons and ligaments in the carpal tunnel. Methods: From June to November in 2017, a total of 49 healthy volunteers [aged from 18 to 27 years, 24 males (48 cases of hands) and 25 females (50 cases of hands)] were selected in the Institute of Digitized Medicine and First Affiliated Hospital of Wenzhou Medical University.Three hand postures of the volunteers were simultaneously and continuously measured by using LOGIQ E9 ultrasonic diagnostic apparatus and Zebris foot pressure distribution measurement system.Seventeen parameters of nerves, tendons and ligaments in carpal tunnel were observed under natural (0 N), and two forced (25 and 50 N) states.Double factor variance analysis was performed with generalized estimating equation (GEE). Results: With increasing pressure (0, 25 and 50 N) of hand postures, the distance between median nerve and transverse carpal ligament were all less than 0.2 cm.The differences in both the distance between median nerve and flexor pollicis longus under the hand pressure changes or under the hand posture changes and the top angle of a triangle composed of median nerve, flexor pollicis longus and flexor digitorum superficialis group under the hand pressure changes or under the hand posture changes were all significant under the GEE analysis (all P<0.01). There were no significant changes in all other structural parameters in the carpal tunnel with the increasing of hand pressure (all P>0.05). Conclusions: The influence of the transverse carpal ligament to the median nerve belongs to the mechanism of pressure-induced irritation damage.The influence of flexor pollicis longus to median nerve belongs to the mechanism of tension-induced irritation damage.The influence of flexor digitorum superficialis to median nerve belongs to the mechanism of mixed shear irritation damage.