Anatomical Variations and Clinical Significance of the Palmaris Longus Muscle

The palmaris longus is a slender, superficial flexor of the wrist distinguished by exceptional variability in presence, morphology and insertion. Phylogenetically regarded as a vestigial muscle, it may be wholly absent in up to a quarter of individuals, with reported rates ranging from below 2% to over 50% among different populations. Variations include agenesis, reversal of muscle belly, accessory slips, duplication and multiple insertion patterns into the palmar aponeurosis or adjacent tendons. Its tendon often crosses or lies in close proximity to the median nerve, a relationship of paramount importance in carpal tunnel and reconstructive procedures. Clinically, the palmaris longus tendon is prized for grafting in ligament, tendon and ligament reconstructions, owing to its adequate length and minimal functional deficit when harvested. Functional studies consistently demonstrate negligible loss of grip strength or proprioceptive accuracy in the general population, though subtle roles in fine motor tasks have been examined in specialised cohorts. Identification methods include clinical tests such as Schaeffer’s and Mishra’s manoeuvres, and imaging modalities like ultrasound and magnetic resonance. A comprehensive understanding of its anatomical diversity informs safe surgical planning, anthropological research and biomechanical modelling worldwide.

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Anatomical Variations and Clinical Significance of the Palmaris Longus Muscle publication trend

The graph below shows the total number of articles in anatomical variations and clinical significance of the palmaris longus muscle across all publications each year (not limited to Nature Index journals).

Technical terms

Agenesis: Congenital absence of a structure, in this context the palmaris longus muscle.

Proprioception: The sensory perception of limb position and movement, critical for coordinated motor control.

Tendon graft: A surgical procedure in which a tendon segment is harvested and used to repair or replace damaged ligaments or tendons.

Median nerve: The major nerve supplying the forearm and hand, vulnerable to compression where the palmaris longus tendon may lie.

Palmar aponeurosis: A sheet of fibrous tissue in the palm that serves as the primary insertion site for the palmaris longus tendon.

References

1. Musculus Palmaris Longus: Influence on Playing Capability of Keyboard Musicians – Preliminary Report. Frontiers in Psychology (2018).
2. Frequency of Agenesis Palmaris Longus through Clinical Examination - An East African Study. PLOS ONE (2011).
3. Anatomical variations of the palmaris longus muscle including its relation to the median nerve – a proposal for a new classification. BMC Musculoskeletal Disorders (2017).
4. Ultrasonograpic Assessment of Relationship Between the Palmaris Longus Tendon and the Flexor Retinacular Ligament and the Palmar Aponeurosis of the Hand. Electronic Journal of General Medicine (2010).
5. Palmaris Longus Muscle’s Prevalence in Different Nations and Interesting Anatomical Variations: Review of the Literature. Journal of Clinical Medicine Research (2015).
6. Effects of the Presence Rate of the Palmaris Longus Tendon on Wrist Proprioception and Grip Strength. Cureus (2023).