Brachioradialis (Sömmerring)
Brachioradialis is often united with brachialis at its origin, and its origin may extend proximally as far as the insertion of deltoideus, with which it may be connected. It may also be joined to extensor carpi radialis longus and abductor pollicis longus.
The muscle may be divided, with the second belly attached distally to the radius (near the tuberosity), or even the ulna. In about 7% of cases, the tendon is split into two or three slips, occasionally allowing the radial nerve to pass through and by doing so becomes a potential entrapment site for the nerve. A tendinous slip may also join the fascia of the forearm. The insertion may ascend on the lateral face of the radius or may be extended distally to the navicular, trapezium, or base of the third metacarpal bone.
Brachioradialis may be joined to the supinator.
An accessory brachioradialis termed supinator longus accessorius (Lauth) or brachioradialis brevis minor (Gruber) arises adjacent to brachioradialis, inserts on the radial tuberosity, and acts as a true supinator. It may also join the supinator, the tendon of pronator teres, or the ulna. Brachioradialis may send tendinous slips to the biceps tendon thereby becoming an accessory to biceps brachii.
Brachioradialis may be doubled or absent.
Syn.: m. supinator longus (Henle), Langer Ruckwartswender, Armspeichenmuskel.
References
Baur, R. (1971) Innervation des M. brachioradialis aus dem N. musculocutaneous als seltene Varietät. Anat. Anz. 128:108-110.
Calori, L. (1866) Intorno ad alcune varieta incontrate nella muscolatura degli arti superiori annotazioni anatomische. Mem. Accad. Sci. d. Istituto di Bologna. S.2 VI: 157-174.
Calori, L. (1867) Di alcuni nuovi muscoli sopannumerarii degli arti. Mem. Accad. Sci. d. Istituto di Bologna. S.2, VI: 137-147.
Calori, L. (1868) Delle anomalie più importanti di ossa, vasi, nervi, e muscoli occorse nell'ultimo biennio facendo anatomia del corpo umano. Mem. R. Accad. Sci. Istituto di Bologna S. 2, 8:417-482.
Gruber, W. (1867) Uber die varietaten des musculus brachioradialis. Bull. Acad. Imp. Sci. St. Petersbourg. 12:527-528.
Gruber, W. (1887) Auftreten des Musculus radialis externus accessorius als Musculus supinator longus II. s. accessorius. Arch. Path. Anat. Physiol. Klin. Med. 107:478-480.
Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.
Kaneef, A. (1964) Sehr seltene Kombination von Muskelvarietäten der radialen und dorsal Muskelgruppen eines menschlichen Vorderarmes Anat. Anz. 125: 425-429.
Lauth, E.A. (1830) Varietes dans la distribution des muscles de l'homme. Mem. de la Soc. d'Histoire Naturelle de Strasbourg T.1 1830.
Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25: 1-134.
Magnanon, -. (1874) Anomalie du long supinateur. Lyon Med. 15:500.
Nishida, K. (1941) Ueber den Bau des M. brachioradialis und seiner Anstazsehne. Arbeite aus der med. Fakultät Okayama 6:492-498.
Reid, R.W. and S. Taylor. (1879) Anatomical variations. Reports. St. Thomas's Hospital 9:47.
Shetty P and Sirasanagandla S.R. and Dsouza MR. (2014) Possible Entrapment of Sensory Branch of Radial Nerve by Split Brachioradialis Tendon: An Anatomical Variation. International Journal of Health Sciences and Research 4(6): 204-207.
Spinner, R.J. and M. Spinner. (1996) Superficial radial nerve compression at the elbow due to an accessory brachioradialis muscle: A case report. The Journal of Hand Surgery (Am) 21(3): 369-372.