Z. Aslı Aktan İkiz, Hülya Üçerler

The rectus abdominis muscle is well known to be segmented by tendinous intersections into a certain number of serially arranged compartments. The tendinous intersections are present only on the anterior aspect and fused with anterior sheat of the muscle. Since the rectus abdominis is used as a graft, there are lots of studies in the literature about the rectus abdominis muscle and its intersections. In the dissection of a 64-year-old man at the Department of Anatomy of Ege University Medicine Faculty, an anatomical form of the rectus abdominis muscle not described in the available literature was encountered. Both rectus muscles, right and left, were symmetrical but there were not any tendinous intersections on them. The total length of the muscle was 30 cm for both sides. The width at the umbilical level was 5.7 cm on the right side and 5.4 cm on the left side. The thickness of the muscle at the umbilical level was 0.5 cm for both sides. This previously unreported variation is very interesting for clinical approaches since the transverse rectus abdominis flap is an important reconstructive tool, particularly in reconstruction of the breast following mastectomy.

The rectus abdominis muscle is well known to be segmented by tendinous intersections into a certain number of serially arranged compartments.[1,2,3,4] The tendinous intersections are present only on the anterior aspect and fused with anterior sheat of the muscle.2 Since the rectus abdominis is used as a graft muscle, there are lots of studies in the literature about the rectus abdominis muscle and its intersections. The transverse rectus abdominis musculocutaneous (TRAM) flap has been developed and improved since its first description by Hartrampf et al. and Gandolfo in 1982.[5] For this reason, anatomic variations of the rectus abdominis muscle may be interesting for surgical approaches especially in breast reconstruction.

In the dissection of a 64-year-old man at the Department of Anatomy of Ege University Medicine Faculty in Izmir, an anatomical form of the rectus abdominis muscle not described in the available literature was encountered. This cadaver had no trace of scars and no adhesions or signs of trauma or operation. Both rectus muscles, right and left, were symmetric but there were not any tendinous intersections on them (Figure 1). The total length of the muscle was 30 cm for both sides. The width at the umbilical level was 5.7 cm on the right side and 5.4 cm on the left side. The thickness of the muscle at the umbilical level was 0.5 cm for both sides.

After this examination, the abdominal cavity was opened. The tendinous intersections were not observed on the posterior surface of the muscle also as usual. The courses of the intercostal nerves and blood vessels were normal. The origo and insertio of the muscle were expectedly also.

This previously unreported case is very interesting for clinical approaches since the area of the rectus abdominis muscle is a frequent site of medical interventions of various kinds. The transverse rectus abdominis flap is an important reconstructive tool, particularly in reconstruction of the breast following mastectomy.[4,5,6] Beside this, the pedicled rectus abdominis muscle flap is used in the treatment of complicated stress urinary incontinence.[7] The other usages of the muscle are in reconstruction of chronic fascial palsy[2] and fecal abdominal stomas.[8] Parrett et al. used the rectus abdominis musculocutaneous (RAM) flap as a treatment of lymphedema.[9] The rectus abdominis muscle is advantageous in that[1] it is supplied by long nerves and long and large vessels,[10] distance of contraction are appropriate,[4] the tendinous intersections are suitable for anchoring sutures and[11] it is flat and consists of segments with appropriate lengths.[2] Since the rectus abdominis muscle is used as flap especially in plastic surgery, its anatomic variations have great importance for clinicians.

The anatomic variations of the rectus abdominis muscles in the available literature are related to their insertions, the composition of the human rectus sheath and number and character of the tendinous intersections.[1,11] The absence of the tendinous intersections described herein our cadaver was not reported before.

Drever reported a 39-year-old woman with Poland syndrome had total absence of external oblique muscle and hypoplasia of the rectus abdominis muscle on the left side. In place of the external oblique muscle, a thin-fascia like tissue continued around her flank with no evidence of muscle fibers. Also, the ipsilateral rectus abdominis muscle was close to half the width of that on the opposite side.[12]

Gryzybiak observed a tendinous portion of the rectus abdominis muscle. There were three tendinous intersections of the left rectus muscle in that case: the superior one was entire, irregular and oblique from the side toward the linea alba. Two incomplete intersections were visible only on the lateral side.[1]

Three to four tendinous intersections are identified in each rectus abdominis muscle normally. Whetzel et al. studied the vascular anatomy of the tendinous intersections of the rectus abdominis muscle. The rectus abdominis muscle and intersections have been divided into separate numbered zones in that study. Zones 1, 3, 5 and 7 are muscle zones. Zones 2, 4 and 6 are the superior, middle and inferior tendinous intersections.[2,4] They found lots of perforators for each tendinous intersections. The tendinous intersections in zones 4 and 6 had significantly greater perforator density than any muscle segment.[4] Because of this reason, the tendinous intersections are important regions in approach to abdominal surgery.

Boyd et al. suggested that the transverse rectus abdominis flap would be more reliable if the skin paddle was based in the paraumbilical area because of the greater density of perforators in this region. The study of Whetzel et al. suggested that the perforators within the tendinous intersections were important to the blood supply of the anterior abdominal wall and to obtain optimal arterial supply, the design of TRAM flaps may be based on intersections location as well as paraumbilical location.[4] But of course in such a case of us, it would be better to prefer the paraumbilical region because of the absence of the tendinous intersections.

Up to the 17th week of the prenatal life, rectus abdominis muscles of human fetuses have no tendinous intersections. They appear as late as between the 17th and 20th week of the fetal life.[10] Since the tendinous intersections were found to appear as late as in the 17th week of the fetal life, mechanical factors in fetal life may have played a role for this variation during this period.

The tendinous intersections grow into the muscle from the anterior wall of the sheat.[10] For this reason we did not expect to see them on the posterior surface of the muscle or in the muscle as well, when it was noticed that our cadaver had no tendinous intersections on the anterior surface of the rectus abdominis muscle.

Brown and McGill examined the deformations of the abdominal wall connective tissues, with a special focus on both the internal oblique aponeurosis and tendinous intersections of the rectus abdominis. The tendinous intersections were thought to function, at least in part, to provide strength to the rectus abdominis muscle by giving it anchor points along its length.[13]

According to our opinion although we did not observe any hernia in our cadaver, the absence of the tendinous intersections may be a possible predisposing factor for abdominal wall herniation because this anomaly may have weakened the anterior abdominal wall.

1.  Grzybiak M. A case of tendinous portion of the rectus abdominis muscle in a syndrome of several developmental anomalies. Folia Morphol (Warsz) 1974; 33: 61-6.

2.  Hata Y, Yano K, Matsuka K, Ito O, Matsuda H, Hosokawa K. Treatment of chronic facial palsy by transplantation of the neurovascularized free rectus abdominis muscle. Plast Reconstr Surg 1990; 86: 1178-89.

3.  Hijikata T, Wakisaka H, Yohro T. Architectural design, fiber-type composition, and innervation of the rat rectus abdominis muscle. Anat Record 1992; 234: 500-12.

4.  Whetzel TP, Huang V. The vascular anatomy of the tendinous intersections of the rectus abdominis muscle. Plast Reconstr Surg 1996; 98: 83-9.

5.  Rossetto LA, Garcia EB, Abla LF, Neto MS, Ferreira LM. Quilting suture in the donor site of the transverse rectus abdominis musculocutaneous flap in breast reconstruction. Ann Plast Surg 2009; 62: 240-3.

6.  Rozen WM, Ashton MW, Murray AC, Taylor GI. Avoiding denervation of rectus abdominis in DIEP flap harvest: the importance of medial row perforators. Plast Reconstr Surg 2008; 122: 710-6.

7.  Wall LL, Phil D, Copas P, Galloway NTM. Use of a pedicled rectus abdominis muscle flap sling in the treatment of complicated stress urinary incontinence. Am J Obstet Gynecol 1996; 175: 1460-6.

8.  Bardoel J, Stadelmann WK, Tobin GR, et al. Use of the rectus abdominis muscle for abdominal stoma sphincter construction: an anatomical feasibility study. Plast Reconstr Surg 2000; 105: 589-95.

9.  Parrett BM, Sepic J, Pribaz JJ. The contralateral rectus abdominis musculocutaneous flap for treatment of lower extremity lymphedema. Ann Plast Surg 2009; 62: 75-9.

10.  Goscicka D, Murawski E. Tendinous intersections of the rectus abdominis muscle in human fetuses. Folia Morphol (Warsz) 1980; 34: 427-34.

11.  Monkhouse WS, Khalique A. Variations in the composition of the rectus sheath: a study of the anterior abdominal wall. J Anat 1986; 145: 61-6.

12.  Drever JM, Zavala J. Unilateral absence of the external oblique muscle with hypoplasia of the rectus abdominis muscle in a patient with Poland syndrome. Plast Reconstr Surg 2002; 110: 1802-3.

13.  Brown SH, McGill SM. An ultrasound investigation into the morphology of the human abdominal wall uncovers complex deformation patterns during contraction. Eur J Appl Physiol 2008; 104: 1021-3.