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Anatomic variation of the iliacus and psoas major muscles
Abstract
Routine dissection has identified a previously unrecorded unilateral variation of the iliacus and psoas muscles in a 91-year-old female cadaver. A variant iliacus muscle belly originated from the superior lateral aspect of the iliac fossa and after traversing the iliac fossa in a nearly horizontal plane, inserted into the psoas major muscle forming a blended iliacus-psoas muscle. The femoral nerve coursed laterally behind the muscle variant to the superior edge of the blended iliacus-psoas. The femoral nerve then coursed over the anterior aspect of the muscle variant and continued inferiorly in a typical course toward the inguinal ring. The current findings and clinical significance are discussed.
... 1,2,14,15 Some studies have reported cases of variant muscle slips of the psoas and iliacus may split the FN causing a potential risk for nerve entrapment. 12,21,33,34 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 FN. 4,22,23 Vazquez et al. reported variations of iliacus and psoas piercing the FN, piercing of the FN by a muscular slip, or a muscular slip/sheet covering the FN as it lay on the iliacus (7.9%). ...
... It was detached from its origin confirming it had no attachment to the iliolumbar ligament. 21,24,33 The muscular slip was then followed distally until it blended into other iliacus and psoas fibers to incorporate into the iliopsoas which inserted on the femur. The FN was found to be formed from the posterior division of the L2-L4 ventral nerve roots and was fully formed prior to being pierced by the accessory slip of the iliacus. ...
... Some authors mentioned that this splitting was accompanied by an abnormal course of the FN, which passed between the two layers. 8,30,33 Both in the sheet muscle and the slip pattern, the compression onto the FN may change depending on the density of the muscular bundles. In our opinion, the FN was located under dense muscle mass such as the sheet muscle pattern because slip muscle pattern was exposed to muscle compression lesser. ...
Compression of the femoral nerve (FN) to the iliac fossa has been reported as a consequence of several pathologies as well as due to the aberrant muscles. The purpose of this research was to investigate the patterns of the accessory muscles of iliopsoas muscles and the relationship of the FN in fifty semi pelvis. Accessory muscular slips from iliacus and psoas, piercing or covering the FN, were found in 19 specimens (7.9%). Based on the macroscopic structure, the muscle was categorized into two types. Pattern 1 as the more frequent variation, was sheet muscular type covering the FN (17 specimens, 89.5%). Pattern 2, the less frequent variation was found on a muscular slip covering the FN (2 specimens, 10.5%). Iliac and psoas muscles and their variants on both types were defined. Appraising the relation between the muscle and the nerves, each disposition of the patterns may be a potential risk for nerve entrapment. The knowledge about the possible variations of the iliopsoas muscle complex and the FN may also give surgeons confidence during pelvic surgery. Recognition of these variations in normal anatomy may be useful to the clinicians when treating patients with refractory leg pain.
... The femoral nerve, derived from the second to fourth lumbar dorsal divisions, is one of the terminal branches of the lumbar plexus [1]. Multiple studies have reported variant slips of the psoas and iliacus muscles which may split the femoral nerve causing a potential risk for nerve entrapment [2][3][4][5][6][7][8][9]. In a large study of 121 cadavers, Vazquez et al. reported variations of iliacus and psoas muscles piercing the femoral nerve, piercing of the femoral nerve by a muscular slip, or a muscular slip/sheet covering the femoral nerve as it lay on the iliacus in 19 specimens (7.9%) [3]. ...
... The sciatic and femoral nerves represent the two largest peripheral collections of lumbar and sacral nerve roots [1]. There have been other cadaveric reports of variance in sciatic and femoral nerve as well as piriformis and iliopsoas complex muscle anatomy similar to what is described in this case [2][3][4][5][6][7][8][9]12,15]. However, to the authors' knowledge, these variants have yet to be reported in one single specimen, and thus the potential clinical significance of these sole variants may be enhanced when possessed together. ...
... For the diagnosis of lower lumbar nerve root impingement, straight leg raise testing is 69% sensitive and 84% specific [18]. Reproduction of radicular leg pain in both sciatic and femoral nerve distributions with nerve traction testing is a common sign of lumbar disc herniations [16][17][18], and variations in both the course of the sciatic and femoral nerves as well as the surrounding musculature may affect the results of these nerve traction tests [2,4]. ...
To present a group of anatomical findings that may have clinical significance.
This study is an anatomical case report of combined lumbo-pelvic peripheral nerve and muscular variants.
University anatomy laboratory.
One cadaveric specimen.
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.
Piercing of the femoral nerve by an accessory iliacus muscle combined with wide variations in sciatic nerve and piriformis muscle presentations may have clinical significance.
Combined femoral and sciatic nerve variants should be considered when treatment for a lumbar disc herniation is refractory to care despite positive orthopedic testing.
... They participate in hip and lumbar spine flexion, and aid in the stabilization of the lumbar spine and sacroiliac joint (SIJ) [13,20,22]. Of these muscles, the psoas minor appears to be the most variable between populations [5,14,22,24]; however, the iliacus and psoas major also manifest certain variability [1,3,9,19,20,25,27]. ...
Background:
While many structures within the human body demonstrate anatomical variations, this is not typically the case for the iliopsoas muscle complex. However, the present paper describes a case of an anomalous psoas major composed of four different muscular heads in a 78-year-old male cadaver.
Materials and methods:
During a routine dissection of the right posterior abdominal wall, an unusual psoas major was observed, measured and photographed.
Results:
The psoas major was found to possess four muscular heads, otherwise the anatomy of the wall was normal.
Conclusions:
The presence of so many heads could interfere with the functions of the psoas major muscle. Therefore this anatomical variation merits further study.
... Fabrizio [18] D Additional, aberrant slips of higher origin, which can also include extremely rare psoas quartus and also rare psoas tertius. ...
BACKGROUND: The muscles present in the pelvic girdle compartment demonstrate clinically significant anatomical variation regarding both their site of attachment and additions, such as accessory heads, muscles, or tendinous slips. Many of those variations might be considered potential traps during ultrasound examination, which may result in misdiagnosis. The aim of this study was to raise awareness of such a possibility. MATERIALS AND METHODS: A comprehensive search for morphological variations was performed in PubMed and NIH. Relevant papers were listed, and citation tracking was accomplished. RESULTS: Although several anatomical variations of pelvic girdle muscles have been presented, few studies have examined their relevance in ultrasound imaging. CONCLUSIONS: The morphological variability of the pelvic girdle muscles does not vary from such incidence in other regions of the human body; however, further ultrasound studies are needed of the numerous morphological variants that can be found in this region.
... The anomalous muscle was identified as a double-headed AIM. [8,13,26]; type C, with complete fusion of IM and psoas major with typical course of FN [9]; type D, with highly originated muscular slips that include extremely rare reports of psoas tertius and psoas quartus [5,11,27]; type E, with an iliacus minor -a muscle arising from the anterior inferior iliac spine of the ilium and inserting onto the anterior trochanteric line, and the ilio-capularis, with a similar originanterior trochanteric line and insertion onto the ilio-femoral ligament [2,29]; type F, with deep and superficial layers of IM [10,16]; type G, with large muscular slips of iliacus [21]; ...
BACKGROUND: Numerous accessory muscles are present in the human body, many of which are clinically significant. We present a case of an anomalous accessory iliacus composed of 2 heads, whose occurrence and anatomical location indicate a high probability of causing femoral nerve compression. MATERIALS AND METHODS: During a routine dissection of the posterior abdominal wall of a 78-year-old cadaver, a double-headed accessory muscle was noted, measured, and photographed. RESULTS: In addition to the normal anatomy of dissected structures from the posterior abdominal wall, an accessory iliacus muscle composed of superficial and deep heads was identified. In addition, the inferior roots of the divided femoral nerve located between the heads was found to follow an unusual course. CONCLUSIONS: It is important to be aware of morphological variability around structures such as the double-headed accessory iliacus muscle presented in this study, due to their association with neurovascular bundles and hip joints. The reported atypical morphology is not widely known in the literature but might be of great clinical significance; therefore, knowledge of such variability might be regarded in order to diagnose properly and introduce accurate treatment.
... Jorge Magaña Reyes, 1 Luis Gerardo Domínguez Gasca, 2 Luis Gerardo Domínguez Carrillo 3 Masculino de 42 años con dos meses de sintomatología caracterizada por dolor (7/9 en la EVA) localizado en la región glútea izquierda, irradiado a la cara posterolateral del muslo ipsilateral hasta la cabeza del peroné, acompañado de parestesias en la misma área; el dolor se exacerbaba con ejercicio y manejo de automóvil; no presentaba lumbalgia. La molestia inició inmediatamente después de la realización de ejercicio (doble elevación de las extremidades pélvicas con rodillas en extensión, en posición supina). ...
... Jorge Magaña Reyes, 1 Luis Gerardo Domínguez Gasca, 2 Luis Gerardo Domínguez Carrillo 3 Masculino de 42 años con dos meses de sintomatología caracterizada por dolor (7/9 en la EVA) localizado en la región glútea izquierda, irradiado a la cara posterolateral del muslo ipsilateral hasta la cabeza del peroné, acompañado de parestesias en la misma área; el dolor se exacerbaba con ejercicio y manejo de automóvil; no presentaba lumbalgia. La molestia inició inmediatamente después de la realización de ejercicio (doble elevación de las extremidades pélvicas con rodillas en extensión, en posición supina). ...
Masculino de 42 años con dos meses de sintomatología caracterizada por dolor (7/9 en la EVA) localizado en la región glútea izquierda, irradiado a la cara postero-lateral del muslo ipsilateral hasta la cabeza del peroné, acompañado de parestesias en la misma área; el dolor se exacerbaba con ejercicio y manejo de automóvil; no presentaba lumbalgia. La molestia inició inmediatamente después de la realización de ejercicio (doble elevación de las extremidades pélvicas con rodillas en extensión, en posición supina). A la exploración: postura y marcha normales; examen clínico muscular normal excepto para el glúteo medio y bíceps crural izquierdos en 4/5; hipoestesia en la cara posterolateral del muslo; el resto, normal; reflejos osteotendinosos, pulsos arteriales y lle-nado capilar normales. Fue manejado con AINE por dos meses, sin cambio en la sintomatología; fue enviado a rehabilitación, con diagnóstico presuntivo de síndrome facetario con datos de irritación radicular L5 incompleta. Se solicitó una resonancia magnética, donde se encontró músculo psoas accesorio izquierdo (Figuras 1 y 2) respon-sable de la sintomatología por compresión extraforaminal de la raíz L5 izquierda; fue sometido a un programa de rehabilitación (16 sesiones) con ejercicios de Williams y estiramiento de los flexores de cadera. Fue dado de alta asintomático. Figura 1. Imagen de resonancia magnética en secuencia coronal, ponderada en T1, a nivel del conducto medular a la altura de L4-L5, donde se identifi có en situación paraespinal izquierda una imagen isointensa al músculo, de morfología triangular (fl echa), justo sobre el trayecto de las raíces emergentes, correspondiendo a músculo psoas accesorio. Figura 2. Imagen de resonancia magnética en secuencia axial ponderada en T1, que muestra obliteración de la señal de la grasa posterior al psoas lumbar izquierdo por músculo psoas accesorio (fl echa); compárese con el lado contralateral. www.medigraphic.org.mx
... The femoral nerve then coursed over the anterior aspect of the muscle variant and continued inferiorly in a typical course toward the inguinal ring Philip A. Fabrizio. [32] Lateral femoral cutaneous nerve (LFCN) is a sensory nerve that originates from the posterior division of L2 and L3 joining to form the nerve. It runs diagonally from the lumbar vertebral foramen medial to the iliac crest under the fascia of iliacus muscle and emerges between the anterior superior iliac spine (ASIS) and lateral attachment of the inguinal ligament, and then runs superficially and pierces the fascia lata 10 cm inferior to the inguinal ligament to supply the skin over the anterolateral aspect of the thigh. ...
The aim was to restore the function and form of both arches with a proper occlusal relationship and eruption of tooth in the cleft area.
Eleven patients were selected irrespective of sex and socio-economic status and whose age was within the mixed dentition period. Iliac crest is grafted in cleft area and subsequently evaluated for graft success using study models, and periapical and occlusal radiographs.
At the time of evaluation teeth were erupted in the area and good alveolar bone levels were present. Premaxilla becomes immobile with a good arch form and arch continuity. There are no major complications in terms of pain, infection, paraesthesia, hematoma formation at donor site without difficulty in walking. There is no complication in terms of pain, infection, exposure of graft, rejection of graft, and wound dehiscence at the recipient site.
It is evident that secondary alveolar grafting during the mixed dentition period is more beneficial for patients at the donor site as well as the recipient site.
Long-term follow-up is required to achieve maximum advantage of secondary alveolar grafting; the age of the patient should be within the mixed dentition period, irrespective of sex, socio-economic status. It may be unilateral or bilateral.
The rectus abdominis and pyramidalis muscles belong to the anterior abdominal muscles. Variations in the morphology of rectus abdominis have been reported; these include higher-than-normal locations of its insertions, differing numbers of tendinous intersections within the muscle, variations in the rectus sheath formed by the aponeuroses of the three lateral abdominal muscles, and inconsistencies in the shape and height of the arcuate line. The external abdominal oblique muscle generally originates from the ribs and its aponeurosis forms the inguinal ligament and anterior layer of the sheath of rectus abdominis. The internal abdominal oblique muscle lies deep to the external abdominal oblique muscle. The posterior abdominal muscles are quadratus lumborum, psoas major, psoas minor, and iliacus. Few anatomical variations of quadratus lumborum have been reported. Psoas major and iliacus share the compound iliopsoas tendon, which inserts into the lesser trochanter of the femur.
Introduction
The main objective was to study the normal and abnormal lumbar plexus.
Material and methods
We analyzed 131 lumbar plexuses from 68 embalmed cadavers at the Cadaveric Surgical Training Center, Faculty of Medicine, Chiang Mai University in the period between April 2012 and June 2013. Morphometric measurements were taken.
Results
The lumbar plexus was located within psoas major muscle (100.0%). The iliohypogastric nerve originated from the ventral rami of L1 (96.5%) followed by the ilioinguinal nerve (90.1%). The genitofemoral nerves originated from the ventral rami of L1 and L2 (98.5%). The lateral femoral cutaneous nerves (LFCN) originated from the ventral rami of L2 and L3 (84.0%). The femoral and obturator nerves originated from ventral rami of L2–L3–L4 (100.0%). The distance between the origin of LFCN to L3 transverse process was at an average 1.96 ± 0.67 cm. The distance from nerve to L4 transverse process was above L3 and between L3 and L4 transverse process at an average 2.8 ± 1.63 cm. The distance between femoral nerve to L3 and L4 transverse process was inferior to L4 transverse process at an average of 5.13 ± 2.18 cm and 2.53 ± 2.26 cm, respectively. The distance between obturator nerve to L3 and L4 transverse process was found inferior to L4 transverse process at an average 5.42 ± 1.73 cm and 2.75 ± 1.75 cm, respectively.
Discussion
The knowledge of anatomical variations of LP may be important for administration of local anaesthetic agents and avoid any inadvertent injuries.
Psoas major is a muscle of the posterior abdominal wall. The name psoas comes from the Greek word psoa meaning the "loin region". Its linear origin is complex and includes the vertebral bodies and associated intervertebral discs from twelfth thoracic to fourth or fifth lumbar vertebrae and of the costal processes of all the lumbar vertebrae. Psoas major together with iliacus muscle inserts on the lesser trochanter of the femur. The degree of unification of the psoas and iliacus muscle can vary (m. iliopsoas), and rarely, its proximal attachments can show atypical anatomical variations. Moreover, composition of the psoas major muscle can differ regarding sex and race. Psoas major muscle is composed of all three muscle fibre types. Since it is dynamic as well as postural muscle it shows equal distribution of fast and slow muscle fibres. Regarding its dynamic function psoas major muscle is designated as the main flexor of the hip joint. Its rotational action as well as the actions of the abduction or adduction is minimal. In addition, psoas major muscle can produce ventral and lateral flexion of the vertebral column. Regarding its postural function psoas major muscle maintains lumbar lordosis and stabilizes lumbar spine, sacroiliac joint and hip joint during sitting as well as standing, walking or running.
Introduction
Variations in the iliopsoas muscle complex certainly have some clinical importance. Because these variations are usually associated with unusual femoral nerve formation, here we report a case of variation in the iliacus muscle combined with variation in the femoral nerve.
Case report
Variation in the iliacus muscle combined with variation in the femoral nerve was observed while performing a routine dissection of a 65-year-old male cadaver in the Department of Anatomy, SRM Medical College. The accessory iliacus muscle originated from iliac crest and inserted to the lesser trochanter of femur along with psoas major. This muscle variant was found to split the femoral nerve into medial and lateral slips.
Conclusion
The existence of this muscle variation along with nerve variation may increase the chances of nerve compression. Hence, detailed knowledge of these variations has immense importance in various pelvic and pelvifemoral surgeries.
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.
Disc herniations at the L1-L2 and L2-L3 levels are different from those at lower levels of the lumbar spine with regard to clinical characteristics and surgical outcome. Spinal canals are narrower than those of lower levels, which may compromise multiple spinal nerve roots or conus medullaris. The aim of this study was to evaluate the clinical features and surgical outcomes of upper lumbar disc herniations.
We retrospectively reviewed the clinical features of 41 patients who had undergone surgery for single disc herniations at the L1-L2 and L2-3 levels from 1998 to 2007. The affected levels were L1-L2 in 14 patients and L2-L3 in 27 patients. Presenting symptoms and signs, patient characteristics, radiologic findings, operative methods, and surgical outcomes were investigated.
The mean age of patients with upper lumbar disc was 55.5 years (ranged 31 to 78). The mean follow-up period was 16.6 months. Most patients complained of back and buttock pain (38 patients, 92%), and radiating pain in areas such as the anterior or anterolateral aspect of the thigh (32 patients, 78%). Weakness of lower extremities was observed in 16 patients (39%) and sensory disturbance was presented in 19 patients (46%). Only 6 patients (14%) had undergone previous lumbar disc surgery. Discectomy was performed using three methods : unilateral laminectomy in 27 cases, bilateral laminectomy in 3 cases, and the transdural approach in 11 cases, which were performed through total laminectomy in 10 cases and unilateral laminectomy in 1 case. With regard to surgical outcomes, preoperative symptoms improved significantly in 33 patients (80.5%), partially in 7 patients (17%), and were aggravated in 1 patient (2.5%).
Clinical features of disc herniations at the L1-L2 and L2-L3 levels were variable, and localized sensory change or pain was rarely demonstrated. In most cases, the discectomy was performed successfully by conventional posterior laminectomy. On the other hand, in large central broad based disc herniation, when the neural elements are severely compromised, the posterior transdural approach could be an alternative.
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.
In bilateral dissections of 68 cadavers, four examples were found unilaterally of variant slips of iliacus and psoas major muscles. In three of them the femoral nerve was pierced by the variant slip. One of these variants was a previously undocumented accessory slip of iliacus, originating from the iliolumbar ligament, passing inferiorly anterior to iliacus, and traversing the femoral nerve; its tendon split to be attached proximally to the lesser trochanter of the femur and distally to an unknown insertion. Such anomalies might cause tension on the femoral nerve resulting in referred pain to the hip and knee joints and to the lumbar dermatomes L2,3 and 4.
Primary malignant tumors of the iliopsoas compartment are rare entities that have been infrequently reported. We present our experience of iliopsoas malignancy to better characterize and define the natural history of this condition.
Primary iliopsoas tumors occurring from January 1990 were identified from the Royal Marsden Hospital's (RMH) Sarcoma Unit prospective database.
Nineteen malignant tumors (11 limited to the psoas muscle only, 1 involving only the iliacus muscle and 7 involving both the iliacus and psoas) of the iliopsoas compartment were evaluated and treated at the RMH during this period. Leiomyosarcoma (n = 5) and liposarcoma (n = 3) were the most frequent histologic types. There were 3 G1, 5 G2, 10 G3 tumors and grade could not be assessed in 1 patient. There were 17 T2 tumors and size was not available in 2 patients. Surgery was done in 14 patients (negative microscopic margins-7, positive microscopic margins-3, and positive gross margins-3 and the margin of excision was not known in 1 patient). Five of 14 surgically treated patients had local recurrence and 6 of 19 patients developed metastases. Ten patients died of their disease at a median follow-up of 12 months. The estimated 2 and 5 year survival rates were 44 and 23%, respectively.
Tumors in this location have a poor prognosis due to the lack of early diagnosis, large size at presentation, multiple attachments of the psoas muscle, and being relatively surgically inaccessible.
Inspite of the detailed description of the iliopsoas muscle complex, interesting variations of its main parts--the psoas major and the iliacus muscles can still be encountered. These variations may clarify some aspects of the embryological development of the iliopsoas and have certain clinical importance because of the frequent co-existence with an unusual femoral nerve by its formation and course. We present in our report a case of bilateral variations of the psoas major and the iliacus muscles combined with variations of the left and the right femoral nerves, which were found during the anatomical dissection of a female human cadaver. The most remarkable finding was noted on the left side, where an undescribed variant muscle accessory iliopsoas, was observed. It was the only finding of such a muscle among 108 human cadavers examined over a period of 22 years. The accessory iliopsoas was formed by the connection of two accessory muscles--accessory psoas major and accessory iliacus. The clinical significance of the described variant muscles and their importance as an additional factor in the femoral neuropathy are also a matter of discussion in our report.
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