Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: A
Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed
The accessory abductor digiti minimi may also compress the deep palmer branch of the ulnar nerve. Compression of the ulnar nerve in Guyon's canal occurs when the muscle hypertrophies in the canal or with traumatic compression between the muscle and the pisohamate ligament. The muscle, artery, and ulnar nerve all lie in the narrow confines of the canal of Guyon, which is bounded by the pisiform and hamate bones. A small separate slip may extend from the pisiform bone to a metacarpal bone, forming the pisimetacarpeus muscle.
Pisiuncinatus (pisohamatus) is a small muscle occurring in 2-5% of hands. It extends from the pisiform bone to the hook of the hamate bone. A similar slip may extend from the pisiform bone to the flexor retinaculum.
Syn.: m. abductor digiti quinti.
Accessorius Abductor Digiti Quinti
Laboratory Specimen, University of Iowa
Accessorius Abductor Digiti Quinti
From Calori, 1868
Accessorius ad abductorem digiti minimi manus.
Note that the darkened muscle attached to the tendon of palmaris
longus enters the hypothenar muscle mass. The muscle inserts by a
long thin tendon onto the base of the fifth metacarpal on its medial
side. The muscle traverses the canal of Guyon where it may compress
the ulnar artery and ulnar nerve.
From Calori,1868.
Pisiuncinatus (Pisohamatus)
See B: a, tendon of flexor carpi ulnaris; b, abductor digiti minimi;
c, flexor digiti minimi; d, opponens digiti minimi; e, pisiuncinatus
(pisohamatum); alpha, os pisiform; beta, hamulus ossis hamati.
from Gruber, 1875, 1881.
References
Baumann, J.A. (1947) Valeur, variation, et équivalencies des
muscles extenseurs, interosseux, adducteurs et abducteurs de la main
et du pied chez l'homme. Acta Anat. 4:10-16.
Bucher, O. (1943) Über die Varietäten des M. abductor digiti quinti. Anat. Anz. 94: 317-324.
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.
Fahrer, M. and P.J. Millroy. (1981) Ulnar compression neuropathy due to an anomalous abductor digiti minimi - Clinical and anatomic study. J. Hand Surg. 6:266-268.
Gruber, W. (1875) Ein Musculus piso-hamatus beim Menschen. Arch. Anat. Physiol. Wissen. Med. 1875:202-203
Gruber, W. (1881) Über den Arcus tendineus piso-hamatus, und dessen Substituten, den Musculus piso-hamatus. Arch. Path. Anat. Physiol. Klin. Med. 86:19-25.
Gruber, W. (1888) Ein Musculus piso-metacarpeus. Arch. Path. Anat. Physiol. Klin. Med. 114:365-367.
Guyon, F. (1861) Note sur une disposition anatomique propre à la face antérieur cuter de la region du poignet et mon encore décrite. Bull. Soc. Anat. Paris 6:184-186.
Ikeda, A., Nagaoka, A. and M. Kimura. (1958) On the variation of the abductor digiti minimi and the palmaris longus. Hiroshima Daigaku Igakubu Kaibogaku Daiichi Koza Gyosekishu. 2:96-100. In Japanese.
Lahey, M.D. and P.L. Aulicino. (1986) Anomalous muscles associated with compression neuropathies. Orthopaedic Review 15(4) 199/19-28/208.
Lamb, D. (1970) Ulnar nerve compression lesions at the wrist and hand. Hand 2:17-18.
Lane, W.A. (1887) Abnormal muscles of the hand. J. Anat. Physiol. 21:673.
Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of muscular variations hitherto published. 25:1-134.
Schjelderup, H. (1964) Aberrant muscle in the hand causing ulnar nerve compression. J. Bone Joint Surg. (B) 46:361.
Stocquart, A. (1882) Quelques anomalies et varietiés anatomique observés sur le vivant et sur le cadaver. J. de Med., de Chir., et de Pharmacology 4:449-453.
Swanson, A.B., Biddulup, S.L., Baughman, F.A. and G. deGroot. (1972) Ulnar nerve compression due to an anomalous muscle in the canal of Guyon. Clin. Orthop. Rel. Res. 83:64-69.
Turner, M.S. and D.M. Caid. (1977) Anomalous muscles and ulnar nerve compression at the wrist. Hand 9:140-142.
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