Anatomical variation of radial wrist extensor muscles: a study in cadavers

Abstract

Objective: The tendons of the extensor carpi radialis longus and brevis muscles are quite useful in tendon transfer, such as in correction of finger clawing and restoration of thumb opposition. Knowledge of additional radial wrist extensor muscle bellies with independent tendons is useful in the above-mentioned surgical procedures.

Methods: The skin, subcutaneous tissue, and antebrachial fascia of 48 (24 on the right side and 24 on left side) male upper limb forearms were dissected. The following aspects were then analyzed: (a) the presence of additional muscle bellies of radial wrist extensors, (b) the origin and insertion of the additional muscle, and (c) measurements of the muscle bellies and their tendons.

Results: Five out of 48 upper limbs (10.41%) had additional radial wrist extensors; this occurred in 3 out of 24 left upper limbs (12.5%) and 2 out of 24 right upper limbs (8.3%). In one of the right upper limbs, two additional muscles were found. The length and width of each additional muscle belly and its tendon ranged between 2 - 15 cm by 0.35 - 6.4 cm and 2.8 - 20.8 cm by 0.2 0.5 cm, respectively. The additional radial wrist extensor tendons in our study basically originated either from the extensor carpi radialis longus or brevis muscles and were inserted at the base of the 2nd or 3rd metacarpal bone.

Conclusion: The present study will inform surgeons about the different varieties of additional radial wrist extensors and the frequency of their occurrence.

Figure 1

Extensor compartment of the left forearm and hand region. AWE, additional wrist extensor; D, dorsal digital expansion for the index finger; ECRB, extensor carpi radialis brevis; Er, extensor retinaculum. The course of the additional muscle is shown by the downward facing arrows. The upward facing arrow indicates the tendon of extensor indicis muscle.

Figure 2

Extensor compartment of the left forearm and hand region. ARWE, additional radial wrist extensor; B2M, base of the second metacarpal bone; B3M, base of the third metacarpal bone; ECRL, extensor carpi radialis longus.

Figure 3a

Extensor compartment of the right forearm and hand region. TECRB into B3M, tendon of extensor carpi radialis brevis inserted into the base of the third metacarpal bone; TECRL into B2M, tendon of extensor carpi radialis longus inserted into the base of the second metacarpal bone. Note that the downward arrows indicate the course of the additional muscle.

Figure 3b

Superior-lateral view of the right forearm region. ARWE, additional radial wrist extensor. The downward arrows indicate its course, already shown in figure 3a. BR, brachioradialis. Note the additional muscles arising both from the BR (lateral) and ECRL (medial), joining to form a single muscle on its way to be inserted into the tendon of the ECRB.

Figure 4

Extensor compartment of the left forearm and hand region. TECRB into B2/3M, tendon of extensor carpi radialis brevis inserted into the base of the second and third metacarpal bones; TECRL into B2M, tendon of extensor carpi radialis longus inserted into the base of the second metacarpal bone. Note that the downward arrows indicate the course of the additional muscle. The muscle was inserted into the tendon of the ECRB.

Figure 5

Extensor compartment of the right forearm and hand region. TECRB into B3M, tendon of extensor carpi radialis brevis inserted into the base of the third metacarpal bone; TECRL into B2M, tendon of extensor carpi radialis longus inserted into the base of the second metacarpal bone. Note the downward arrows, which indicate the course of the additional muscle.