Cooper David W., Burns Bracken
East Tennessee State University
East Tennessee State University (ETSU)
The palmaris longus is a small, fusiform-shaped muscle located on the anterior forearm of the human upper extremity. This muscle belongs to the superficial forearm flexor group, with a most common proximal attachment at the medial epicondyle of the humerus via the common forearm flexor tendon and a most common distal attachment into the connective tissue fibers of the palmar aponeurosis and the flexor retinaculum, a ligamentous structure forming the roof of the carpal tunnel and containing the median nerve and digital flexor tendons. The palmaris longus can be morphologically quite variable but most commonly has a tendinous proximal attachment, a mid-length, spindle-shaped muscle belly, and a long and thin tendinous distal portion. The majority of fibers in the palmaris longus tendon pass superficially to the flexor retinaculum, the tendon broadens into a flattened collection of fibers, and the fibers interweave with the palmar aponeurosis. The functional contribution of the palmaris longus appears to be minimal, but it has clinical significance due to its frequent intraoperative harvest for many surgical procedures, often involving tendon repair in the upper extremity. The thin distal tendinous portion, superficial location, and lack of functional significance make the muscle easily accessible and ideal for intraoperative harvest for tendon reconstruction and other surgical procedures. The palmaris longus muscle is commonly present but may be absent in a small percentage of the population, ranging from 2.5% to 26% of individuals, depending on the studied population. The palmaris longus tendon is located near the anatomical center of the anterior wrist, medial to the tendon of flexor carpi radialis, and lateral to the tendon of flexor carpi ulnaris. The muscle’s presence can be assessed clinically by several physical exam maneuvers, with the Schaeffer test being the most commonly used. To perform the Schaeffer test, ask the patient to touch the pads of the thumb and little finger together while flexing the wrist, and if present, the tendon of palmaris longus should protrude anteriorly at the wrist joint. Congenital absence of the muscle is common but has not demonstrated decreased grip strength or any other functional deficit.
掌长肌是一块小的、梭形肌肉，位于人类上肢的前臂前部。这块肌肉属于前臂浅屈肌群，其最常见的近端附着点是通过前臂屈肌总腱附着于肱骨内上髁，最常见的远端附着点是进入掌腱膜和屈肌支持带的结缔组织纤维，屈肌支持带是一种韧带结构，形成腕管的顶部，包含正中神经和指屈肌腱。掌长肌在形态上差异很大，但最常见的是近端有腱性附着，中间为纺锤形肌腹，远端为细长的腱性部分。掌长肌腱的大部分纤维从屈肌支持带表面通过，肌腱变宽成为扁平的纤维束，纤维与掌腱膜交织。掌长肌的功能贡献似乎很小，但由于在许多外科手术中经常在术中取用它，通常涉及上肢的肌腱修复，因此具有临床意义。其远端细的腱性部分、表浅的位置以及缺乏功能意义，使得该肌肉易于获取，是术中用于肌腱重建和其他外科手术的理想选择。掌长肌通常存在，但在一小部分人群中可能缺失，根据所研究的人群不同，缺失率在2.5%至26%之间。掌长肌腱位于腕前部的解剖中心附近，桡侧腕屈肌腱的内侧，尺侧腕屈肌腱的外侧。该肌肉的存在可以通过几种体格检查手法进行临床评估，其中谢弗试验是最常用的。进行谢弗试验时，让患者在屈腕时将拇指和小指的指尖触碰在一起，如果存在掌长肌，其肌腱应在腕关节前方突出。该肌肉先天性缺失很常见，但尚未证明会导致握力下降或任何其他功能缺陷。
