ANATOMICAL AND CLINICAL INSIGHT OF VARIANT MORPHOLOGIES OF PSOAS MINOR S Gandhi et al MUSCLE: A CASE REPORT

ANATOMICAL AND CLINICAL INSIGHT OF VARIANT MORPHOLOGIES OF PSOAS MINOR MUSCLE: A CASE REPORT

IJCRR S. Gandhi1 , N. Gupta2, A. Thakur1, A. Anshu1, V. Mehta1, R.K. Suri1 , G. Rath1 Vol 05 issue 14

Section: Healthcare 1 Category: Case Report Vardhaman Mahavir Medical College and Safdarjang Hospital, New Delhi, India 2 Received on: 10/06/13 All India Institute of Medical Sciences, New Delhi, India Revised on: 24/06/13 E-mail of Corresponding Author: [email protected] Accepted on: 19/07/13

ABSTRACT Psoas minor is long, slender and functionally weak muscles that assist psoas major in flexing the trunk and spinal column. Psoas minor at its origin lies just in front of the psoas major muscle has small belly and long tendon like plantaris and palmaris longus muscle. Psoas minor receives its nerve supply from the ventral rami of L1 spinal nerves, which after piercing through the psoas major muscle enter into the muscular belly. In the present case, psoas minor muscle was found bilaterally in a 60 years old male formalin fixed cadaver. Bilaterally, the muscle depicted absence of fusion with adjacent psoas major and was found to exist independently. The distal insertion of the muscle was variable when compare to the contralateral peer. Moreover, in contrast to the muscular portion, the tendinous portion was remarkably lengthier. As the muscle is closely related to important neurovascular structures of retroperitoneum, it may compress them during its involvement in psoas minor syndrome and psoas abscess; yielding myriads of clinical signs and symptoms. The incidence and morphometric parameters of this inconsistent muscle are highly variable and had been frequently correlated with ethnic and racial characteristics. The current report reveals a case of bilateral existence of psoas minor and disparity in its morphometric attributes on either side. Against this background, analysis of deviation in structural architecture and its distribution in population has been attempted. To consolidate the scattered pieces of information about variability in different parameters of this muscle and reemphasize its significant role in radiographic and surgical procedures, a review of literature is constructed to appraise the medical persons working in related fields. Keywords: Psoas major, Psoas minor, Psoas minor syndrome, variations

INTRODUCTION classified as an inconsistent muscle 5 and is often The Psoas minor muscle is a constituent of the absent 3. It is considered the muscle with highest posterior abdominal wall and lies ventral to the percentage of unilateral or bilateral agenesis, psoas major muscle. When present, it usually considered ranging from 40% to 66% in different originates from the lateral sides of the body of the populations2,5. In case of its existence, the thin twelfth thoracic vertebra (T12), first lumbar tendon of this muscle can rarely arise from an vertebra (L1), and the intervening intervertebral expansion of the medial border of the psoas disc. The short muscular part is continuous with a major muscle5. thin tendon, which is inserted into the iliopubic Morphometric and morphological descriptions on eminence, pectineal line of the pubis and laterally the psoas minor muscle are scarce, discrete and in the iliac fascia1,2. The psoas minor muscle have unorganized in the literature and do not provide been found to flex the lumbar spine and tilts it any conclusive anatomical information about the sideways when contracting unilaterally3, apart muscle. The aim of the present study is to reveal from providing stabilization to the hip joint 4. It is the anatomy of the psoas minor muscle, ascertain

Int J Cur Res Rev, July 2013/ Vol 05 (14) Page 106 ANATOMICAL AND CLINICAL INSIGHT OF VARIANT MORPHOLOGIES OF PSOAS MINOR S Gandhi et al MUSCLE: A CASE REPORT their origin and insertion points, analyze the death of the case was apparently unrelated to possible dependent relationship between the previously mentioned variant findings. fibers of the psoas minor and major muscles, neurovascular relations and determine the DISCUSSION proportional relationship between the tendinous The psoas minor muscle varies considerably in its and muscular parts of the psoas minor. We also morphology and morphometry. The possible aim at providing an insight into the clinico- variations in the morphology of psoas minor surgical importance of this variant muscle. muscle can be broadly discussed and reviewed by taking into account the following parameters. CASE REPORT Incidence of psoas minor- In majority, psoas During the course of routine cadaveric dissection minor muscle is deficient similar to commonly for undergraduate students of a 60 year old male absent muscles like pyramidalis, psoas parvus, cadaver, the posterior abdominal wall revealed peroneus tertius, palmaris longus, and plantaris6. the bilateral existence of well formed psoas minor In major studies, the incidence of existence of muscle taking origin from the lateral surfaces of psoas minor was found to exhibit a range of the body of T12 & LI vertebra and from findings such as 30% 6-9. The relative discrepancy intervening tendinous arch (fig. 1a & 1b). in frequencies is presumed to be correlated with Bilaterally the psoas minor muscles were getting the racial and ethnic differences in the population inserted onto the iliopubic eminence, the insertion 6,10. They are illustrated in table1 being tendinous on the left side (fig1b) and Gender bias- The higher occurrence of this tendinoaponeurotic that fuses with the iliac fascia muscle in females compared to males6 had been on the right side. On further exploration, the contradicted in other study, where the gender bias length of left sided psoas minor measured as 10.5 was found to be insignificant7. No scientific cm and 12 cm for the muscular and tendinous dictums regarding its probable correlation of its part respectively (fig 1b). The maximum width of incidence with any particular gender was later the muscle at muscular and tendinous part was established6. 2.50 cm and 0.90 cm in that order (1b). On the Variations in origin and insertion- Usually it right side, length of muscular belly and the finds its attachment on the first two lumbar variant tendinoaponeurotic part when compared vertebras and the intervening intervertebral disc to the left measured as 11 cm and 10.50 cm similar to present case. Infrequently it might (fig1a). The maximum widths of muscular, originate through two heads, which may tendinous and aponeurotic parts of the right sided segregate partially or completely prior to its distal psoas minor were 2.50 cm, 0.50 cm and 4.50 cm insertion on iliopubic eminence. Alternatively, its respectively (fig1a). The genitofemoral nerve, insertion may be erratically located at iliac fascia, which pierced the psoas major muscle, oriented inguinal ligament, neck of the femur or lesser itself along the medial border of psoas minor trochanter in unison with psoas major. The muscle bilaterally. tendinous insertion can bifurcate, leading to the On both sides, the tendons of muscle were found attachment of additional aberrant band on the positioned lateral to the external iliac artery. synchondrosis between the fifth lumbar vertebra Bilaterally, they received the nerve supply from and the sacrum, apart from its usual insertion at anterior division of L1 spinal nerve. No iliopectineal line 6. The muscle may merge with contracture, lump, tumor fixation or signs of the pelvic or iliac fascia, through which it injury were seen in the muscles. The cause of possibly gets attached to crural arch 6,11 which

Int J Cur Res Rev, July 2013/ Vol 05 (14) Page 107 ANATOMICAL AND CLINICAL INSIGHT OF VARIANT MORPHOLOGIES OF PSOAS MINOR S Gandhi et al MUSCLE: A CASE REPORT simulates the findings observed in right sided in psoas compartment syndrome 16. The psoas psoas minor in the current case. minor muscle being a retroperitoneal structure The duplication of psoas minor has also been lies in close proximity to important neurovascular seen in the past, where the first belly overlapped structures in the posterior abdominal wall. the other from before backwards6. Infrequently, Infections, hematoma and neoplasm localized in the ramifications of muscular fibers of psoas the retroperitoneal planes have propensity to major yielding psoas minor have been mentioned involve the adjacent psoas fascia and muscle 17. as source of unusual origin6. Moreover, as the cranial portion of psoas minor is Proportional extent of muscular and tendinous placed posterior to crural attachment of parts- Remarkably long tendons of psoas minor diaphragm, any pathological collection within the muscle have been accounted in the precedent confinement of fascia overlaying the muscle may history 5,12. Absolute tendinous replacement of gain access to endothoracic cavity. The this muscle is also reported in different studies comprehension of these muscular variations 6,13. However, the literature provides inconclusive allows insight into the pattern of localization and data on the proportional relationship between the spread of infection and malignancy in the extent of muscular and tendinous parts of the retroperitoneal region of the body18. The space psoas minor. occupying lesions situated in psoas muscles may Side difference- although the relative absence of impinge on the related nerves of lumbar plexus this muscle on the right side compared with the leading to motor or sensory neurological deficits left is mentioned6. The preferential presence on of lower limb 18. Psoas compartment block has either side remains statistically unresolved. been inferred as useful alternative in alleviation Probable functions of the muscle- Psoas minor, of postoperative pain following hip and knee if present, exerts minimal contribution in the surgeries; hence, the comprehension of flexion of lumbar spine14,15, yet it reinforces psoas morphological variations of psoas minor is major in maintaining lordotic lumbar curvature imperative for success of such techniques19. The through the sustained tone inherent in itself 15. variant muscle as observed in the current case Comparative anatomy- psoas minor has been should not be confused with the retroperitoneal found to be well developed in hopping animals lymphadenopathy. Since the originating head of like marsupials, macrocelides, jerboa etc 6. psoas minor lies in posterior relation of renal pelvis and neurovascular pedicles, it may CLINICAL IMPLICATIONS interfere with the operative field in percutaneous The psoas minor syndrome is attributed to nephrolithostomy. In aberrant lower spinal unusual high tone in psoas minor muscle and curvature correction surgeries, the role of tendon 15 where, the patient complaints of pain in lengthening of predominantly tendinous the lower quadrant of the abdomen. In addition, configuration of psoas minor must be considered. the pain was aggravated by palpation of the taut To address the lack of information in the tendon in lean individuals presenting with acute literature regarding psoas minor muscle’s abdomen 15. In this syndrome, there is the limited morphology, morphometry and its clinical extension, which impairs ambulation. Tenotomy implications, this case endeavor to provide is the only treatment of choice, which relieves the detailed information about the muscle in order to symptoms. This remarkable entity may simulate expand knowledge of its clinical anatomy. the pain of appendicitis or diverticulitis localized in iliac fossae 15. Psoas minor, functioning as an adjunct to psoas major, may be variably involved

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CONCLUSION 11. Gardener E, Gray D, O’Rahilly R. In: The clinicians and academicians have often Gardener E, Gray D, O’Rahilly R, editors. overlooked the role of psoas minor owing to its Anat. Parede Abdom. Posterior. 4a ed. Rio relative scarcity of anatomicosurgical di Janeiro: Guanabara Kougan; 1988. p. 356. comprehension. The review of psoas minor and 12. Lee J, Sagel S, Stanley R. Comput. Body its crucial disposition in the retroperitoneum Tomogr. Mri Correl. New York: Raven; would serve to appraise and guide the 1989. p. 756–60. interventional procedures and differential 13. Testut L, Latarjet A. Músculos del abdomen: diagnosis of relevant simulating clinical región posterior o lumboiliaca. Tratado de conditions. anatomía humana. 9th ed. Barcelona: Salvat; 1976. REFERENCES 14. Pellegrino F, Tangelson C, Galiano L, 1. O’Rahilly R. Anatomia de Gardener. 5th ed. Trevisan L, Sánchez G, Puricelli F. Criterios Mexico: Nuvea Editorial Americana; 1986. de homologación entre las cinturas escapular 2. Williams P, Warwick R. Anatomy the y pélvica y sus estructuras asociadas; Grays. 37th ed. Edinburgh: Churchill Homologation criterion between the Livingstone; 1992. scapular and pelvic waists and their 3. Gray H. Anatomia. 29th ed. Rio di Janeiro: associated structures. Rev Chil Anat. Guanabara Kougan; 1977. 1998;16(1):75–82. 4. Moore K, Dally K. Anatomia orienteda para 15. Travell J, Simons D. Myofascial Pain and a clinica. 5th ed. Rio di Janeiro: Guanabara Dysfunction: The Trigger Point Manual; Kougan; 2007. Vol. 2., The Lower Extremities. 2nd ed. 5. Tellez V, Acuna L. Consideraciones Philadelphia: Lippincott Williams and Anatomicas de los Musculos Inconstantes. Wilkins; 1998. Med Unab; 1998. 16. Klammer A. [Fascia compartment syndrome 6. Kraychete DC, Rocha APC, Castro PACR of the iliac-psoas compartment]. Z. Für de. Psoas muscle abscess after epidural Orthop. Ihre Grenzgeb. 1983 analgesia: case report. Rev. Bras. Jun;121(3):298–304. Anestesiol. 2007 Apr;57(2):195–8. 17. A Al-Zamil JTC. Psoas muscle hematoma-- 7. Donovan PJ, Zerhouni EA, Siegelman SS. an acute compartment syndrome. Report of CT of the psoas compartment of the a case. Vasa Z. Für Gefässkrankheiten J. retroperitoneum. Semin. Roentgenol. 1981 Vasc. Dis. 1988;17(2):141–3. Oct;16(4):241–50. 18. Dyke JAV, Holley HC, Anderson SD. 8. Snell R. membro inferior. In: Snell P, editor. Review of Iliopsoas anatomy and pathology. Anat. Clin. Para Estud. Med. 5th ed. Rio de Radiographics. 1987 Jan 1;7(1):53–84. janeiro; 1999. 19. Touray ST, de Leeuw MA, Zuurmond 9. Bergman R, Afifi K, Miyauchi R. Illustrated WWA, Perez RSGM. Psoas compartment Encyclopedia of Human Anatomic block for lower extremity surgery: a meta- Variation, Virtual Hospital, University of analysis. Br. J. Anaesth. 2008 Yowa, 2002, Yowa City, Yowa, USA, Dec;101(6):750–60. www.vh.org. 10. Mori M. Statistics on the musculature of Japanese. Folia Anat. Jap. 1964;195–300.

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TABLE-1 Incidence of presence of Psoas minor in different population and ethnic groups S.No. Researchers Population and Incidence ethnic group 1. Bergman RA et al (6) Asians 51.1% Whites 43% Negroes 33.4% 2. Mori et al (10) Japanese 46.4% 3. Gruber et al (cited by 10) Russians 52% 4. Schwalbe et al (cited by 10) Alsatians 43% 5. Thomson et al (cited by 10) English 41% Scotsmen 37% Irish 34% 6. Loth et al (cited by 10) Negroes 47.6% 7. Nakano et al(cited by 10) Chinese 48.1%

Figure 1a: DC-diaphragmatic crura, MAL-medial arcuate ligament, K(refl.)-kidney reflected, Pm(m,t,a)- muscular belly, tendinous part, aponeurotic part of Psoas Minor, PM- Psoas Major, LCNT- lateral cutaneous nerve of thigh, I- iliacus, EIA- external iliac artery. Figure 1b: DC-diaphragmatic crura, K(refl.)-kidney reflected, Pm(m,t)- muscular belly, tendinous part of Psoas Minor, GF-genitofemoral nerve, LCNT- lateral cutaneous nerve of thigh, EIA- external iliac artery.

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