|Year : 2015 | Volume
| Issue : 3 | Page : 285-287
Unilateral accessory Sartorius muscle: A case report on its functional and clinical implications
Jyothsna Patil, Naveen Kumar, Ravindra S Swamy, Anitha Guru, KG Mohandas Rao, Ashwini P Aithal
Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), Manipal University, Manipal, Karnataka, India
|Date of Web Publication||2-Sep-2015|
Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), Manipal University, Manipal - 576 104, Karnataka
Sartorius is a long strap muscle that originates from the anterior superior iliac spine and inserts on the upper medial surface of the tibia. It crosses the anterior thigh obliquely, and its medial edge forms the lateral boundary of the femoral triangle. Since it crosses two joints of the lower limb, it is also known as a bi-articulate muscle. It confers its action on both hip joint and knee joint. Its variations are extremely rare and seldom reported. We report here an exceptional variant accessory Sartorius muscle (SM) originating from the inguinal ligament, and joining the main SM eventually at the level of the junction between upper one-third and lower two-third of the thigh. In the present case, we discuss the clinical and functional implications of this exceptional case of accessory SM.
العضلة الخياطية الثانوية أحادية الجانب - تقرير عن الوظيفة والعلاقة الطبية
العضلة الخياطية هي عضلة شريطية تبدأ من الشوكة الأمامية العلوية الحرقفية لتدخل في السطح العلوي لعظم الساق الأعظم ، وتمرّ من أمام الفخذ بانحراف , وتشكّل حافتها الوسطى الحد الجانبي من مثلث الفخذ، وبما أنها تمرّ بمفصلين من الطرف الأسفل فإنها تعرف بالعضلة ثتائية المفصل وتستمدّ حركنها من مفصل الفخذ والركبة ؛ إلاّ أن اختلاف العضلة الخياطية نادر وقليل التسجيل . وقد سجلت الدراسة اختلافا استثنائيا للعضلة الخياطية وهو وجود عضلة ثانوية تنحدر من الرباط الأربي للفخذ وترافق العضلة الخياطية للفخذ عند التقاء الثلث العلوي من الفخذ مع ثلثي الجزء السفلي من الفخذ. وفي الحالة المقدمة ناقشت الدراسة العلاقة الطبية والوظيفية لهذه الحالة الاستثنائية من العضلة الخياطية.
Keywords: Accessory muscle, sarcoma, Sartorius, variation
|How to cite this article:|
Patil J, Kumar N, Swamy RS, Guru A, Mohandas Rao K G, Aithal AP. Unilateral accessory Sartorius muscle: A case report on its functional and clinical implications. Saudi J Sports Med 2015;15:285-7
|How to cite this URL:|
Patil J, Kumar N, Swamy RS, Guru A, Mohandas Rao K G, Aithal AP. Unilateral accessory Sartorius muscle: A case report on its functional and clinical implications. Saudi J Sports Med [serial online] 2015 [cited 2019 Jul 19];15:285-7. Available from: http://www.sjosm.org/text.asp?2015/15/3/285/164317
| Introduction|| |
Sartorius is the longest muscle in the body. It arises with a single tendinous origin from anterior superior iliac spine (ASIS) and the notch immediately below it. It crosses the thigh obliquely and descends vertically to the medial side of the knee forming a flattened tendon and expands into a broad aponeurosis distally to gain attachment onto the medial surface of tibia, anterior to gracilis and semitendinosus insertions.  Variations of Sartorius are exceptionally rare and to the best of our knowledge, not many cases of its variations are reported in the literature. Uncommon variations of Sartorius one might occasionally encounter are its absence or doubled Sartorius. When it is doubled, its extra head is usually attached to a pectineal line or femoral sheath. 
In the thigh, Sartorius is pierced by intermediate femoral cutaneous nerve and infra-patellar branch of the saphenous nerve. Its motor nerve supply is provided by the anterior division of the femoral nerve.  Sartorius is a biarticulate muscle as it crosses two joints; hip joint and knee joints of lower limb. On hip joint its action is to flex, adduct and to rotate the hip joint laterally. On knee joint, it flexes and medially rotates the knee in semi-flexed position.  We report here a rare case of accessory Sartorius muscle (SM) that arose from the inguinal ligament (IL) and which then fused with the main SM.
| Case Report|| |
During routine human cadaveric dissection for the medical undergraduate students of preclinical year, we observed an accessory muscular slip for the SM, lying medial to the main SM [Figure 1]. This muscular slip was about 6.5 cm in length and was tendinous in origin. It took origin from the IL of the left side of an elderly male cadaver aged about 60 years. The main SM had its normal origin and course as described in standard textbooks of anatomy with the normal distal attachment as well. The accessory slip descended downward and medially along the medial side of the main SM and joined with the later at the level of junction between upper one-third and lower two-third of the thigh and blended with it at its medial border. The great saphenous vein was accompanying this muscular slip medially. The femoral nerve was lying deep to the accessory Sartorius slip [Figure 2]. This variant accessory slip was found unilaterally.
|Figure 1: Dissection of anterior compartment of the thigh showing accessory slip (AS) for Sartorius muscle (SM) arising from inguinal ligament (IL). GSV: Great saphenous vein, AL: Adductor longus, RF: Rectus femoris, VM: Vastus medialis and VL: Vastus lateralis muscle|
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|Figure 2: Closer view of accessory slip (AS) of Sartorius muscle (SM) from the inguinal ligament (IL) and its distal attachment with the main SM. GSV: Great saphenous vein, FN: Femoral nerve, CN: Cutaneous branch of the femoral nerve, AL: Adductor longus, RF: Rectus femoris muscle|
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| Discussion|| |
The SM is a slender strap muscle in the anterior compartment of the thigh, forming the lateral boundary of femoral triangle and roof of the adductor (sub-sartorial) canal. When it contracts bilaterally, the lower limbs are brought into the position of a tailor, upon which the Latin name (for tailor) was derived from this muscle.  Reports on variant forms of Sartorius are very rare in the available anatomical literature. However, Macalister, from his report in 1871, on observation of muscular anomalies has quoted some of its rare variations. These involve its morphological variations such as doubled Sartorius either with the separate insertion or united to each other before insertion, distal splitting of the muscle (Sartorius bicaudatus), Sartorius with two heads (biceps Sartorius), which are very rare of its variant forms. The author has also mentioned some of its anomalous insertion patterns as it may end in fascia lata, insertion by central tendon, inserting into the medial side of the capsule of the knee, etc. 
In rare circumstances, the Sartorius may be partially divided distally or it may be completely divided into two parts longitudinally. In later cases, an accessory part may be inserted into fascia lata, into patellar ligament or to the tendon of its twin. Accessory heads of its origin is a rare variation of the SM and occasionally may arise slightly below the normal origin from ASIS, close to pubic symphysis or from the IL. 
Garbelotti et al., reported a variation of Sartorius with its double origin, from a usual site of ASIS and the accessory head from iliopectineal eminence.  The Distal bifurcation of Sartorius, also known as Sartorius bicaudatus has been reported by Melling and Zweymuller in 1996. 
Garbelloti et al., also mentioned from the earlier reported cases and opined that, these variations of Sartorius believed to be an atrophied remnant of a pelvic bundle that is usually seen in lower mammals.  Hence, the rare variation of the Sartorius as we report here gain importance in the involution of the muscle in adapting to human function in addition to its functional and clinical significance.
Anatomically, SM is likely to be protected from microscopic invasion of soft tissue tumor due to its anatomical protection by the fascial layers. Nevertheless, gross tumors could penetrate the inter-muscular fascial septa and fascia lata, thus could endanger the muscle. Therefore, clinically it has been suggested that, Sartorius need not to be included in radiotherapy clinical target volume for anterior compartment soft tissue sarcomas if the preoperative magnetic resonance imaging confirms there is no abnormality. 
Functionally, strengthening of SM is possible by exercises involving its movements, which in turn increase hip flexor strength. This is especially important for athletes, as strong hip flexors allow for a more powerful forward movement of the legs and upward movement of the knees.
In the present case, the additional tendinous slip for the SM was quite remarkable, and its pattern of attachment to the main Sartorius might interfere with its normal action by pulling it diagonally. Clinically prior knowledge of this type of variation of Sartorius becomes essential for the surgeons during procedures at the level of inguino-femoral region.
| References|| |
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Bergman RA, Thomson SA, Afifi AK, Saadeh FA. Compendium of Anatomic Variation. In: Muscles of Lower Extremity. Baltimore: Urban and Schwarzenber; 1988. p. 22-4.
Garbelotti JS, Rodrigues CF, Nobeschi L, Seiji F, Olave E. Anatomical variation of the Sartorius muscle. Rev Chil Anat 1999;17:95-7.
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[Figure 1], [Figure 2]