Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: I
Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed
The psoas and iliacus muscles are occasionally completely independent muscles.
The psoas may be divided longitudinally into fascicles. An accessory slip has been described lateral to the muscle and separated from it by the femoral nerve. Iliacus may be pierced by the femoral nerve.
Mori reports that the psoas major arose from the first lumbar vertebra in 98.6 % of his 152 sides (76 cadavers), and from the second lumbar on two sides, 1.3%. In no instance did the muscle arise from thoracic vertebrae.
Macalister published the following:
In regard to iliacus, Macalister reported the following:
Iliacus minor or iliocapsularis (third head of iliacus), a small detached portion of iliacus, is frequently present. It arises from the anterior inferior spine of the iliac bone and inserts onto the lower part of the intertrochanteric line of the femur, or into the iliofemoral ligament. It is usually separated from iliacus by arising either direclty from the margin, or from its outer surface. Its insertion is always above the main iliacus tendon.
A slip from iliacus may run medial to the psoas muscle.
Syn.: m. Iliacopsoas (Haller), Flexor Femoris (Theile), Psoas-Iliaque (Cruveilheir), Psoas Magnus (Macalister).
Psoas Major Accessorius.
from Saadeh and Bergman
Anson, B.J., Ed. (1966) Morris' Human Anatomy,12th ed., The Blakiston Division, McGraw-Hill Book Company, New York.
Bonin, G. von. (1930) Bau und Variationen des Iliopsoas. Anat. Anz. 69:476-485.
Clarkson, R.D. and H. Rainy. (1889) Unusual arrangement of the psoas muscle. J. Anat. Physiol. 23:504-506.
Macalister, A. (1875) Observations on muscular anomalies in the human anatomy. Third series with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.
Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40: 195-300.
Saadeh, F.A. and R.A. Bergman. (1985) An aberrant psoas major muscle fascicle. Anat. Anz. 160:367-368.
Schaefer, E.A., Symington, J., and T.H. Bryce., Eds. (1923) Quain's Anatomy, 11th ed., Longmans Green and Co., London.
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