Table of contents

AN ACCESSORY GLUTEAL MUSCLE

Fatoß Belgin YILDIRIM, Ph.D., Sevgi DEMÜR, Ph.D., Muzaffer SÜNDEL, Ph.D., Olcay …ZKAN, Ph.D.

Akdeniz University, Faculty of Medicine, Department of Anatomy, Antalya, Turkey
Gazi Medical Journal 1999; 10 : 45-47

SUMMARY
During the dissection of the gluteal region of a 60-year-old male, bilateral accessory gluteal muscles were revealed. These muscles were found to have different shapes on the right and left gluteal regions. The one on the left, which had a rectangular shape, began from the sacrotuberous ligament and the lateral part of the sacrum, and joined the iliotibial tract. The one on the right began from the medial part of the sacrotuberous ligament as a single band, split into two parts and ended at the iliotibial tract as a single band once again. These anomalies in this region should be borne in mind during the operations.

INTRODUCTION
The gluteal region is the roughly quadrilateral area of soft parts corresponding to the prominence of the buttocks. It is bounded above by the iliac crest which separates the region from the posterolateral abdominal wall, below by the deep horizontal furrow of the transverse gluteal fold, medially by the lateral margin of the sacrum and coccyx, and laterally by the tensor fasciae latae muscle. It is clinically important to know the boundaries of the gluteal region. Some people consider the buttock to be only the prominence formed by the gluteus maximus. The gluteal muscles consist of the large glutei ( maximus, medius and minimus), which are mainly extensors and abductors of the thigh at the hip joint. The smaller muscles, which are lateral rotators of the joint, are situated more deeply; they include pirifomis, obturators internus and externus, the superior and inferior gemelli, and quadratus femoris (these actions are, however, modified by the initial position of the thigh) (1-6).
Abnormal fullness of the buttocks occurs with pathological conditions such as subgluteal abscess, tumor, ischiogluteal bursitis, dislocation of the head of the femur, fractures of acetabulum, coxae vara and coxae valga (2, 7).

CASE REPORT
A 60-year-old male cadaver was dissected for educational purposes. During the procedure, an accessory gluteal muscle was found in each gluteal region. The left accessory gluteal muscle began from the sacrotuberous ligament and dorsolateral aspect of the sacrum, extended caudally, dorsally and medially in a rectangular shape crossing quadratus femoris muscle, and joined the iliotibial tract. The lower fibers of the muscle covered the proximal parts of the biceps femoris muscle, semitendinosus muscle and semimembranosus muscle. Between this accessory muscle and quadratus femoris muscle lay the sciatic nerve. The width of the accessory muscle was 4.81 cm at the beginning, 5.80 cm in the middle and 9.92 cm at the junction site to the iliotibial tract . The muscle measured 0.90 cm in thickness and 15.54 cm in length (Fig. 1, 2). 
The right accessory gluteal muscle arose from the lower fibers of the gluteus maximus muscle, medial to the sacrotuberous ligament as a single bundle, and extended caudally and laterally close to the point of insertion as two different bundles. The muscle crossed the sacrotuberous ligament, sciatic nerve and quadratus femoris muscle, and joined the lower fibers of gluteus maximus muscle as a single bundle once again . The length of the single bundle at origin was 1.38 cm and that at insertion was 2.08 cm. The dimensions of the double bundles were 14.04x1.45x0.47 cm and 14.09x1.51x0.43 cm (Fig. 3, 4). 

DISCUSSION
In anatomic studies involving the gluteal region, it has been reported that gluteus medius muscle and piriformis muscle may be joined, gluteus minimus muscle may be split into anterior and posterior parts and gemellus superior muscle may send fibers to piriformis muscle (1, 2). Other studies indicated that quadratus femoris muscle might be absent in 1-2 % of cadavers, be joined to gemellus inferior muscle, or adductor magnus muscle might have deep and superficial layers at the insertion site (2) . Similarly, piriformis muscle might be absent and there might be variations in origin and insertion sites of some muscles and their relation with regional nerves of this region (2, 8).
In addition to the well-known constant muscles, there are many accessory muscles in the human body. In the literature, we could not find any study in which bilateral accessory gluteal muscles were mentioned. We believe that the possibility of the presence of these muscles should be kept in mind in operations and CT and MRI interpretations involving this region. 

Correspondence to : Dr. Fatoß Belgin YILDIRIM
Akdeniz †niversitesi Tİp FakŸltesi
Anatomi Anabilim Dalİ
07070 - ANTALYA - TURKEY
Phone : 242 227 44 85
e-mail : fatos@hipokrat.med.akdeniz.edu.tr

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