Inguinofemoral Area Inguinal Canal Anatomy of the Inguinal Canal in Infants and Children There are readily apparent differences between the inguinal canals of infants and adults. In infants, the canal is short (1 to 1.5 cm), and the internal and external rings are nearly superimposed upon one another. Scarpa's fascia is so well developed that the surgeon may mistake it for the aponeurosis of the external oblique muscle, resulting in treating a superficial ectopic testicle as an inguinal cryptorchidism. There also may be a layer of fat between the fascia and the aponeurosis. We remind surgeons of the statement of White that the external oblique fascia has not been reached as long as fat is encountered. In a newborn with an indirect inguinal hernia, there is nothing wrong with the posterior wall of the inguinal canal. Removal of the sac, therefore, is the only justifiable procedure. However, it is extremely difficult to estimate the weakness of the newborn's posterior inguinal wall by palpation. If a defect is suspected, a few interrupted permanent sutures might be used to perform the repair. Adult Anatomy of the Inguinal Canal The inguinal canal in the adult is an oblique rift in the lower part of the anterior abdominal wall. It measures approximately 4 cm in length. It is located 2 to 4 cm above the inguinal ligament, between the opening of the external (superficial) and internal (deep) inguinal rings. The boundaries of the inguinal canal are as follows: Anterior: The anterior boundary is the aponeurosis of the external oblique muscle and, more laterally, the internal oblique muscle. Remember, there are no external oblique muscle fibers in the inguinal area, only aponeurotic fibers. Posterior: In about ¾ of subjects, the posterior wall (floor) is formed laterally by the aponeurosis of the transversus abdominis muscle and the transversalis fascia; in the remainder, the posterior wall is transversalis fascia only. Medially the posterior wall is reinforced by the internal oblique aponeurosis. Superior: The roof of the canal is formed by the arched fibers of the lower edge (roof) of the internal oblique muscle and by the transversus abdominis muscle and aponeurosis. Inferior: The wall of the canal is formed by the inguinal ligament (Poupart's) and the lacunar ligament (Gimbernat's). The boundaries of the rings are as follows: External ring (Fig. 1-1): There is a triangular opening of the aponeurosis of the external oblique, the base being part of the pubic crest with the margins formed by two crura, superior (medial) and inferior (lateral). The superior crura is formed by the aponeurosis of the external oblique itself; the inferior crura is formed by the inguinal ligament. To be more specific, the medial crus is attached to the lateral border of the rectus sheath and to the tendon of the rectus abdominis muscle in a very peculiar pathway. The lateral crus is attached to the pubic tubercle. Fig(1-1)Highly diagrammatic representation of the external inguinal ring. (Modified from Skandalakis JE, Skandalakis LJ, Colborn GL, Androulakis J, McClusky DA III, Skandalakis PN. The surgical anatomy of the hernial rings. In: Baker RJ, Fischer JE (eds). Mastery of Surgery (4th ed). Philadelphia: Lippincott Williams & Wilkins, 2001; with permission.) Internal ring (Fig. 1-2): The boundaries of this ring, which is an inverted "V" -or "U"- shaped normal defect in the transversalis fascia, are not so simple. The arms of the ∧, anterior and posterior, are a special thickening of the transversalis fascia, forming a sling. The inferior border is formed by another thickening of the transversalis fascia — the iliopubic tract— which is not always very aponeurotic. The internal inguinal ring is an opening of the transversalis fascia corresponding to the middle of the inguinal ligament (see section on sphincteric action under the physiology of the inguinal canal). Fig(1-2)Surgical anatomy of the internal inguinal ring. (Modified from Skandalakis JE, Skandalakis LJ, Colborn GL, Androulakis J, McClusky DA III, Skandalakis PN. The surgical anatomy of the hernial rings. In: Baker RJ, Fischer JE (eds). Mastery of Surgery (4th ed). Philadelphia: Lippincott Williams & Wilkins, 2001; with permission.) The inguinal canal contains, in males, the spermatic cord, or in females, the round ligament of the uterus. The anterior wall of the inguinal canal is formed by the aponeurosis of the external oblique muscle and by participation of the internal oblique muscle more laterally. As a point of reference, the internal oblique muscle in the inguinal area is muscular, not aponeurotic. The superior wall ("roof") of the inguinal canal is formed by the arching lower borders of the internal oblique and transversus abdominis muscles and their aponeuroses. The inferior wall of the inguinal canal is formed by the inguinal ligament and the lacunar ligament. The posterior wall is formed primarily by fusion of the aponeurosis of the transversus abdominis muscle and the transversalis fascia in three-fourths of subjects and by only the transversalis fascia in the remaining one- fourth. From both anatomic and surgical standpoints, the posterior wall (floor) is the most important wall of the inguinal canal. Medially the posterior wall is reinforced by the internal oblique aponeurosis. Fig(1-3)Piriform fossa of Fruchaud, popularized by Madden. (Modified from Colborn GL, Skandalakis JE. Importance of the iliopubic, Cooper's and Gimbernat's ligaments. Probl Gen Surg 1995;12:35-40; with permission.) According to Madden JL 1999, the "piriform fossa" forms part of the posterior wall ("floor") of the inguinal canal. This region is a semi-ovoid space filled with fibrofatty tissue, located at the medial part of the floor. The piriform fossa is bounded as follows (Fig. 1-3): Superior: Iliopubic tract (which inserts into Cooper's ligament) Inferior: Shelving edge of inguinal ligament Lateral: Medial wall of femoral sheath Medial: Ligament of Gimbernat "Floor": Ligament of Gimbernat Wantz noted that Fruchaud did not characterize hernias by their clinical presentation; instead, Fruchaud believed that all hernias of the groin begin within the groin, in an area he named the myopectineal orifice. This area in the groin is bounded as follows: Superior: Arch of internal oblique muscle and transversus abdominis muscle Lateral: Iliopsoas muscle Medial: Lateral border of rectus muscle and its anterior lamina Inferior: Pubic pectin The inguinal ligament spans and divides this framework. The area is traversed by the spermatic cord and femoral vessels and is covered on its inner surface solely by the transversalis fascia. Spermatic Cord The spermatic cord is presented in depth in the chapter on the male genital system. We include here a brief review of the surgical anatomy of this important entity in the inguinal canal. The spermatic cord consists of a matrix of connective tissue continuous proximally with extraperitoneal connective tissue. It contains the ductus deferens, three arteries, three veins, the pampiniform plexus, and two nerves, concentrically invested by three layers of tissue. One other nerve, the ilioingual nerve, usually lies just lateral to the major layers of the cord within the inguinal canal. The elements of the spermatic cord relate to each other as follows: 1) anterior is the pampiniform plexus, and 2) posterior are the ductus deferens and the remnant of the processus vaginalis or hernia sac. These anatomic entities, as well as other contained structures, are covered by the spermatic fasciae. The spermatic cord, on the way to the scrotum, lies deep to the fasciae of Camper and Scarpa. The components of the cord are noted in Table 9-6. The key to remember is "three": three layers of fasciae, three arteries, three veins, three nerves, as well as multiple lymphatics and one duct. Table 9-6. the Spermatic Cord and Its Covering Three fasciae: External spermatic (from external oblique fascia) Cremasteric (from internal oblique muscle and fascia) Internal spermatic (from transversalis fascia) Three arteries: Testicular artery Cremasteric artery Deferential artery Three veins: Pampiniform plexus and testicular vein Cremasteric vein Deferential vein Three nerves: Genital branch of genitofemoral nerve Ilioinguinal nerve Sympathetic nerves (testicular plexus) Lymphatics Source: Skandalakis JE, Colborn GL, Pemberton LB, Skandalakis LJ, Gray SW. The surgical anatomy of the inguinal area — Part 2. Contemp Surg 38(2):28-38, 1991; with permission. Superficial Fascia The superficial fascia (Fig.1-5) is divided into a superficial fatty part (Camper's fascia) and a deep membranous part (Scarpa's fascia). The adipose layer continues downward and laterally into the thigh, gluteal region, and perineum and upward over the anterior abdominal wall and thoracic region. The membranous layer of Scarpa is continuous upward with the fatty layer in the pectoral region, forming the anterior boundary of the retromammary space. Inferiorly, it attaches to the fascia lata of the thigh below the inguinal crease. It is also attached superolaterally to the iliac crest. According to Brantigan,57 Scarpa's fascia does not adhere to the symphysis pubis. Fig(1-5)Superficial fascia (dartos): composed of Scarpa's fascia (membranous) and muscle, and Camper's fascia, which is fatty. Gallaudet's fascia is a continuation of Buck's fascia. The adipose layer and the membranous layer combine in the pubic region, losing much of the fatty content. Together, they form the fundiform ligament, a relatively loose fibrous structure that attaches to the base of the penis (or the clitoris). There, receiving input of smooth muscle fibers, the superficial fascia continues as the dartos tunic of the penis and scrotum (or as the clitoris), where it serves as a superficial fascial layer. In the perineum, the membranous layer is renamed Colles' fascia (Fig.1-5). It attaches laterally to the ischiopubic rami and posteriorly to the base of the urogenital diaphragm. In this way, a space called the superficial perineal cleft is limited posteriorly and laterally.