The Palmaris Longus Muscle and its Relations With the Antebrachial Fascia and the Palmar Aponeurosis

The palmaris longus (PL) is a muscle of the forearm with a long distal tendon that is continuous with the palmar aponeurosis (PA). It is generally assumed that the muscle lies deep to the antebrachial fascia from origin to termination, but a detailed description is lacking. The relationship of the PL tendon with the antebrachial fascia was studied in 30 dissections. The PL was completely absent in six specimens (20%), whereas the PA was identified in all. Average length of the forearm was 25.5 cm (SD: 2.1 cm, range 22-29 cm), overall length of the PL muscle 26.9 cm (SD: 2.6 cm, range 22.5-31.5 cm), muscular belly 13.8 cm (SD: 3.4 cm, range 9.5-23 cm), tendon 13.1 cm (SD: 3.3 cm, range 8-15.5 cm). Proximally, the PL was situated deep to the antebrachial fascia, then in the lower third of the forearm its tendon perforated the antebrachial fascia (at 4.7 +/- 1.7 cm from the bistyloid line) moving to a suprafascial plane, inserting in the PA. The PA could be divided into two layers: the superficial one formed by longitudinal fibers and adherent to the skin, the deep one formed by transverse fibers continuous laterally with the deep fascia of the hand. The PL tendon was found to be in continuity only with the longitudinal fibers of the PA. Based on the anatomical findings, it may be suggested that the superficial part of the PA is situated in the subcutaneous planes of the palm, and that the muscle should be considered as a tensor of the superficial fascial system of the subcutaneous tissue.