An accessory iliacus muscle: a case report.
ABSTRACT We present a case of an anomalous accessory iliacus muscle in the iliac fossa which gets originated from the iliac crest and inserting along with iliopsoas, and appear to compress the L4 root of femoral nerve. During the routine dissection of a male cadaver aged 58 years, we found an accessory iliacus muscle. The L2 and L3 nerve roots joined the L4 root distal to the accessory iliacus muscle. The L4 root of the femoral nerve supplied accessory iliacus muscle. Accessory iliacus muscle might cause tension on the femoral nerve resulting in referred pain to the hip and knee joints and to the lumbar dermatome L4. The clinical significance of this variant muscle and its importance in the femoral nerve entrapment has been discussed.
[show abstract] [hide abstract]
ABSTRACT: Entrapment neuropathies of the sciatic and femoral nerves arising from anatomical variations in the piriformis muscle and iliopsoas muscle complex should be considered in the differential for the disc patient that is refractory to care. Well-documented anatomical variations in the piriformis and iliopsoas complex muscles as well as sciatic and femoral nerves exist with an estimated prevalence of 16.9% and 7.9% respectively. These variants have the potential to produce neural irritation and simulate lumbar radiculopathy (Figures 1, 2). The clinical significance of a combined peripheral nerve and muscular variant may not be immediately obvious in the patient with suspected disc involvement; however, consideration should be given to the presence of a pelvic entrapment neuropathy. Normative electrophysiologic data of lumbar paraspinal muscles combined with enhanced signal intensity of the sciatic or femoral nerve using T2-weighted neurography would suggest that suspected radicular pain secondary to a lumbar disc herniation is in fact attributable to peripheral nerve irritation (Figures 3, 4). References: 1. Smoll NR. Variations of the piriformis and sciatic nerve with clinical consequence: A review. Clin Anat. 2010;23(1);8-17. 2. Vazquez MT, Murillo J, Maranillo E, Parkin IG, Sanudo J. Femoral Nerve Entrapment: A New Insight. Clin Anat. 2007;20;175-179. 3. Busis NA. Femoral and obturator neuropathies. Neurol Clin 1999;17(3);633–653. 4. Petchprapa CN, Rosenberg ZS, Sconfienza LM, Cavalcanti CF, Vieira RL, Zember JS. MR imaging of entrapment neuropathies of the lower extremity. Part 1. Radiographics 2010;30(4);983-1000.SpineLine. 12/2012; 13(6):32.
Article: Co-presentation of unilateral femoral and bilateral sciatic nerve variants in one cadaver: A case report with clinical implications. Chiropractic & Manual Therapies[show abstract] [hide abstract]
ABSTRACT: Objective To present a group of anatomical findings that may have clinical significance. Design This study is an anatomical case report of combined lumbo-pelvic peripheral nerve and muscular variants. Setting University anatomy laboratory. Participants One cadaveric specimen. Methods During routine cadaveric dissection for a graduate teaching program, unilateral femoral and bilateral sciatic nerve variants were observed in relation to the iliacus and piriformis muscle, respectively. Further dissection of both the femoral nerve and accessory slip of iliacus muscle was performed to fully expose their anatomy.Chiropractic & Manual Therapies. 10/2012; 2012 Oct 29;20(1):34(20):34.
Romanian Journal of Morphology and Embryology 2008, 49(3):407–409
C CA AS SE E R RE EP PO OR RT T
An accessory iliacus muscle:
a case report
SUJATHA D’COSTA, LAKSHMI A. RAMANATHAN,
SAMPATH MADHYASTHA, S. R. NAYAK,
LATHA V. PRABHU, RAJALAKSHMI RAI,
VASUDHA V. SARALAYA, PRAKASH
Department of Anatomy, Centre for Basic Sciences,
Kasturba Medical College, Bejai, Mangalore, Karnataka, India
We present a case of an anomalous accessory iliacus muscle in the iliac fossa which gets originated from the iliac crest and inserting
along with iliopsoas, and appear to compress the L4 root of femoral nerve. During the routine dissection of a male cadaver aged 58 years,
we found an accessory iliacus muscle. The L2 and L3 nerve roots joined the L4 root distal to the accessory iliacus muscle. The L4 root of
the femoral nerve supplied accessory iliacus muscle. Accessory iliacus muscle might cause tension on the femoral nerve resulting in
referred pain to the hip and knee joints and to the lumbar dermatome L4. The clinical significance of this variant muscle and its importance
in the femoral nerve entrapment has been discussed.
Keywords: accessory iliacus, femoral nerve entrapment, muscular variations, iliopsoas muscle.
The iliacus is a triangular sheet of muscle, which
arises from the superior two-thirds of the concavity of
the iliac fossa, the inner lip of the iliac crest, the ventral
sacro-iliac and iliolumbar ligaments, and the upper
surface of the lateral part of the sacrum. In front, it
reaches as far as the anterior superior and anterior
inferior iliac spine and receives few fibers from the
upper part of the capsule of the hip joint. Most of its
fibers converge into the lateral side of the tendon of the
psoas major, and the muscles then insert together into
the lesser trochanter, but some fibers are attached
directly to the femur for about 2.5 cm. below and in
front of the lesser trochanter. The anterior branches of
the femoral nerve (anterior branches of L2–3) innervate
this muscle .
The femoral nerve arises from the dorsal branches of
the second to fourth lumbar ventral rami. It descends
through the psoas major, emerging low on its lateral
border and then passes between the psoas and iliacus,
deep to the iliac fascia; passing behind the inguinal
ligament. In the abdomen, the nerve supplies the iliacus
muscle through its small branches .
The iliac fascia covers psoas and iliacus muscle
from their origin to the insertion. In addition, the
iliopsoas muscle complex gets inserted into the lesser
trochanter of femur. There are many reports on
interesting variations of the main part of this complex –
the psoas major and iliacus muscle and the compression
of largest nerve of the lumbar plexus the femoral nerve.
The posterior division of the ventral rami of L2, L3, L4,
and occasionally by L1 and/or L5 roots forms the
femoral nerve. It descends in a groove between psoas
and iliacus, deep to the iliac fascia, to pass under the
inguinal ligament and enter the thigh, where it gives
terminal branches . Several reports have described
variant muscular slips or sheets forming longitudinal
fascicles or wide bands associated with psoas and
iliacus, but most of them are not related to the femoral
The iliopsoas tendon or muscle may be split by the
femoral nerve [10–13]. Occasionally, a slip of the
iliacus, called iliacus minor or the iliocapsularis, arises
from the anterior inferior iliac spine and inserts either
into the trochanteric line of the femur or into the
iliofemoral ligament .
In this case, we report an anomalous accessory
iliacus muscle in a position likely to compress the L4
root of femoral nerve.
? Material and methods
During the routine dissection of the posterior
abdominal wall of a 58-year-old male cadaver,
we observed a variation of femoral nerve formation
with an accessory iliacus muscle on the left side.
The accessory iliacus muscle originated from the
middle third of inner lip of iliac crest and was covered
by a separate fascia, which was distinguishable from the
iliacus fascia and the muscle. When traced distally the
muscle inserted along with iliopsoas complex at the
lesser trochanter (Figure 1).
The L2 and L3 roots of femoral nerve joined the L4
root distal to the accessory iliacus muscle. The L2 and
Sujatha D’Costa et al.
L3 roots were joined in the substance of psoas major
muscle. The latter passed superficial to the accessory
muscle and joined the L4 root to form the main trunk of
Figure 1– AI, accessory iliacus; BAI, branch to
accessory iliacus; IM, iliacus muscle;
PM, psoas major
The course of the femoral nerve was normal distal to
the inguinal ligament. The accessory muscle was
innervated by L4 root of the femoral nerve proximal to
Many interesting and relatively rare variations,
concerning the psoas major and the iliacus muscle have
been described in the literature .
Cases of iliacus splitting into a deep and a
superficial layer have been noted. Some authors
mentioned that this splitting was accompanied by an
abnormal course of the femoral nerve, which passed
between the two layers [16, 17].
The description of a split iliacus might also be found
in the articles about the femoral nerve with an abnormal
course . However, other authors reported this
splitting without any additional information about the
femoral nerve .
Spratt JD et al. (1996) and Vázquez MT et al.
(2007) [18, 19] also have reported accessory iliopsoas
muscle with splitting of femoral nerve.
Muscular variations, such as those mentioned
above, most probably do not cause any considerable
disturbance in the lower
The accessory muscles may be seen as interesting
findings in patients during laparotomy and enrich the
possibilities in the differential diagnosis on CT imaging
of the iliopsoas compartment . Mainly because of
the frequent co-existence with an unusual course and
formation (splitting) of the femoral nerve, these
muscular variations are of a great importance to clinical
In the cases of femoral nerve paralysis of femoral
nerve, neuropathy caused by iliac hematoma after
anticoagulant treatment [21–25] or trauma [26–28] or
vessel catheterization  the existence of some variant
muscles, which may increase the nerve compression,
must be born in mind.
A variant muscular slip, belonging to the psoas
major or the iliacus muscle, or even an accessory
muscle described in this case report may cause tension
of the femoral nerve and therefore should be suspected
in patients with referred pain to the hip and knee joints
and to the lumbar dermatomes .
Accessory iliacus muscle described in the present
case report might cause tension on the femoral nerve
resulting in referred pain to the hip and knee joints and
to the lumbar dermatome L4.
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Sujatha D’Costa, Senior Grade Lecturer, MSc, Department of Anatomy, Centre for Basic Sciences, Kasturba
Medical College, Bejai, Mangalore–575004, Karnataka, India; Phone +91 824 2211746, Fax +91 824 2421283,
Received: April 1st, 2008
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Accepted: May 8th, 2008