Available online 6 February 2023, 152068

Only 10% of subjects were found to have a classical description of the anatomical pattern of the abductor pollicis longus muscle tendon.

Accessory tendons to the abductor pollicis longus are frequently inserted into the abductor pollicis brevis muscle or the trapezium bone.

The presence of supernumerary tendons and their insertion into other wrist structures may affect not only the normal anatomy of the first extensor corridor, but also affect the biomechanics of the trapeziometacarpal joint.

Image techniques should consider this anatomical variation.

Some surgical techniques could benefit from the presence of these supernumerary tendons of the abductor pollicis longus muscle.

The anatomical literature describes the abductor pollicis longus as a muscle with a single tendon inserting on the base of the first metacarpal bone, but investigations have shown that it often exhibits morphological variations. However, methodological approaches used to describe these variations have not been useful in a clinical context. Therefore, the purpose of this investigation was to study and relate such anatomical variations in a clinical context.

Thirty upper limbs from the body donation program were dissected using standard procedures to identify the number of abductor pollicis longus (APL) tendons, their position, site of insertion, length, width and thickness. The presence or absence of the extensor pollicis brevis muscle was also noted. Inter and intra-observer reliability was analysed.

A total number of 71 tendons from the APL muscle were found in the thirty limbs. The most frequent distribution pattern was a main tendon inserted on the base of the first metacarpal and an accessory tendon inserted into the abductor pollicis brevis muscle. These tendons could divide into various tendinous slips that could insert in different locations. Also, clustering algorithms and classical statistical tests showed tendons inserting on the first metacarpal were longer than tendons not inserting on the first metacarpal (p = 0.03), while medial tendons and tendons from an APL muscle with supernumerary tendons were narrower (p<0.001). The absence of the extensor pollicis brevis muscle was not related to the presence of supernumerary APL tendons.

Radiological and surgical implications of these results are important when examining this region of the hand and wrist. The pathophysiology and treatment of de Quervain’s tenosynovitis, trapeziometacarpal arthritis and trapeziometacarpal subluxation or laxity could be influenced by the results of our findings.

abductor pollicis longus

abductor pollicis brevis muscle

extensor pollicis longus muscle

extensor pollicis brevis muscle

trapeziometacarpal joint

first metacarpal bone

abductor pollicis longus

clinical anatomy

wrist

hand

thumb

surgery

tendon

tenosynovitis

© 2023 The Author(s). Published by Elsevier GmbH.