Moore Colin W, Rice Charles L
School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, Canada.
Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada.
J Anat. 2017 Dec;231(6):939-946. doi: 10.1111/joa.12675. Epub 2017 Aug 8.
The palmaris brevis (PB) is a small cutaneous hand muscle that has been described as the most mysterious muscle from a functional and developmental perspective [Kaplan () Kaplan's Functional and Surgical Anatomy of the Hand]. Functionally, the PB is considered to deepen the hollow of the palm and to protect the neurovasculature of the ulnar canal. Although the function of the PB has been inferred from cadaveric observations, the electromyographic (EMG) activity of this muscle has not been explored systematically during specific movements of the hand. The purpose of this study was to record PB intramuscular EMG activity during dynamic grasping tasks, and to quantify the change in PB muscle length (M ) and thickness (M ) incurred during maximal contraction using ultrasound imaging. Intramuscular EMG was recorded from the PB in the dominant hands of 12 healthy participants (11 males, one female; age: 27 ± 4 years) during maximal abduction, flexion and opposition of the 5th digit, and two grasping tasks. Abduction of the 5th digit yielded the greatest EMG activity in most individuals (seven out of 11), and produced significantly less PB EMG activity when compared with grasping a cylindrical-shaped object (P = 0.003) but not a spherical-shaped object (P = 0.130). During maximal abduction of the 5th digit, PB M decreased in both the left (28 ± 11%; P = 0.002) and right (32 ± 5%; P = 0.002) hands. Similarly, a concomitant increase in PB M was observed in the left (68 ± 30%; P = 0.002) and right (85 ± 44%; P = 0.002) hands during the same contraction. These EMG results indicate that the PB is voluntarily activated during prehensile and non-prehensile movements of the hand with significant changes in muscle architecture. The study supports the preservation of the PB in surgical procedures based on its proposed protective role as a muscular barrier to the neurovasculature within the ulnar canal.
掌短肌（PB）是手部一块较小的皮肌，从功能和发育角度来看，它被描述为最神秘的肌肉[卡普兰（）《卡普兰手部功能与外科解剖学》]。在功能方面，掌短肌被认为可加深手掌凹陷并保护尺管的神经血管。尽管掌短肌的功能已从尸体观察中推断出来，但在手部特定运动过程中，该肌肉的肌电图（EMG）活动尚未得到系统研究。本研究的目的是记录动态抓握任务期间掌短肌的肌内EMG活动，并使用超声成像量化最大收缩时掌短肌长度（M）和厚度（M）的变化。在12名健康参与者（11名男性，1名女性；年龄：27±4岁）优势手的掌短肌中记录肌内EMG，记录过程包括小指最大外展、屈曲和对掌，以及两项抓握任务。在大多数个体（11人中的7人）中，小指外展产生的EMG活动最大，与抓握圆柱形物体相比，掌短肌的EMG活动明显减少（P = 0.003），但与抓握球形物体相比则无明显差异（P = 0.130）。在小指最大外展期间，左手（28±11%；P = 0.002）和右手（32±5%；P = 0.002）的掌短肌M均减小。同样，在相同收缩过程中，左手（68±30%；P = 0.002）和右手（85±44%；P = 0.002）的掌短肌M均出现相应增加。这些EMG结果表明，在手部的抓握和非抓握运动过程中，掌短肌会被自主激活，且肌肉结构会发生显著变化。该研究支持在外科手术中保留掌短肌，基于其作为尺管内神经血管肌肉屏障的保护作用。
