Iliac Region

ILIAC REGION (regio iliaca), having the form of a wide, flat depression and therefore often called the iliac fossa, represents part of the posterior wall of the abdomen. Its upper and upper-outer boundary is formed by the iliac crest (crista ossis ilii), its lower-anterior boundary is the anterior edge of the bone and the ligaments originating from it, its inner boundary is the articulation with the sacrum, and its lower-inner boundary is the linea innominata, which at the same time forms the upper boundary of the lateral wall of the pelvis. The skeleton of the region consists of the wing and partly the body of the ilium bone, which form a wide, flat fossa, from the bottom and edges of which a series of muscles of the posterior abdominal wall originate and attach (mm. obliquus abdominis internus, externus and transversus abdominis). Properly belonging to the iliac region are the m. iliacus and m. psoas major (see Human Muscles). Both of these muscles are covered by a dense fascial plate (fascia iliaca), which originates from the edges of the iliac fossa and the corresponding vertebrae and forms for them, together with the bone, a dense sheath. Near the Poupart's ligament, it disappears in its medial parts, while in the lateral parts, fusing along the way with Poupart's ligament, it passes together with the muscles to the thigh. In the region of the eminentia ilio-pectinea, this fascia is stretched between the pubic bone and the mentioned ligament and, in the form of the lig. ilio-pectineum, divides the space under Poupart's ligament into two parts: the lateral (lacuna musculorum), through which the m. ilio-psoas and n. cruralis pass, and the medial (lacuna vasorum), through which the vessels pass (see Femoral Canal). In addition to the m. psoas major, some people have an inconstant thin muscle with a long tendon—the m. psoas minor (see Human Muscles). On the surface of the m. iliaci and the m. psoatis majoris, in the fatty tissue under the fascia iliaca, several small blood vessels pass horizontally (a. lumbalis XV and the ramus iliacus of a. ilio-lumbalis) and obliquely and vertically a series of nerves, which are branches of the lumbar plexus (plexus lumbalis), located inside the m. psoas major. At the upper-outer angle of the iliac fossa lies the n. ilio-inguinalis—an inconstant nerve that often fuses with the n. ilio-hypogastricus (the latter passes outside the region); it originates from L_x and appears from behind the outer edge of the m. psoatis majoris; following the curvature of the iliac fossa, it reaches the iliac crest and near the spina ilii anterior superior pierces the m. transversus abdominis; then, lying among the muscles of the abdominal wall, it passes through the inguinal canal to the skin. The n. cruralis is a powerful trunk that, emerging from behind the outer edge of the m. psoatis majoris, lies in the groove between it and the m. iliacus, and together with them passes through the lacuna musculorum to the thigh, where it divides into motor and sensory branches. Somewhat lower and parallel to it is located the n. cutaneus femoris lateralis. On the anterior surface of the m. psoatis majoris, piercing it, passes the n. genito-femoralis (see Human Nerves). Over the fascia iliaca, which covers the described muscles, vessels and nerves and attaches to the iliac crest and linea arcuata, passes a layer of loose retroperitoneal fatty tissue, which without sharp boundaries passes into the retroperitoneal tissue of the lumbar region and pelvis, and in women continues into the tissue of the broad ligaments of the uterus. In the retroperitoneal tissue are located the a. and v. iliaca externa with branches, a. and v. spermatica interna (in women a. and v. ovarica), the ureter, and a chain of lymph glands. The a. iliaca externa represents a branch of the a. iliaca communis and in most cases originates at the level of the sacroiliac joint; from here it descends along the inner edge of the m. psoatis majoris, separated from it by the iliac fascia, and goes to Poupart's ligament, near which it gives off two branches: one running along the iliac crest—the a. circumflexa ilium profunda, and the second, directed upward along the anterior wall of the abdomen—the a. epigastrica inferior. It emerges onto the thigh through the lacuna vasorum. The vein of the same name lies in relation to the artery within the pelvis on the right side—behind it, and on the left—behind and inward, and under Poupart's ligament—medial to it. The chain of lymph glands (nodi lymphatici iliacae) is located in front of and to the sides of the vessels and extends upward, passing into the aortic group; into it flow the sources of the inguinal (vasa lymphatica inguinalia) and hypogastric (vasa lymphatica hypogastrica) lymph vessels. In front of the vascular bundle crosses the ureter, and somewhat above it—the vasa spermatica. The latter, arising from the aorta and inferior vena cava (in relation to the veins this must be understood in a descriptive sense), and sometimes, especially the left ones—from the renal arteries, descend from above and inward downward and outward, and along the surface of the m. psoatis majoris go to the internal inguinal ring, and in women—to the base of the broad ligament of the uterus, from where they go to the sex glands. The ureter is directed from above and outward, and crossing the lumbar and iliac regions, forms a crossover with them; then it bends at the level of the sacroiliac joint over the iliac vessels and goes into the pelvis. When the peritoneum is detached, the ureter most often moves away with it. The next layer of the iliac region is the peritoneum (peritonaeum), covering the parts of the large intestine covered by it. In the right iliac region is located the caecum and the beginning of the colon ascendens, in the left—the colon descendens and the flexura sigmoidea. Initially, the caecum is fixed in the right hypochondrium and only later descends downward. If the process of descent is delayed or stopped, the caecum at the moment of birth may occupy a higher position than usual, sometimes outside the limits of the region under consideration. Similarly, with further growth, the caecum can change its position (Shevkunenko! Lisitsyn), and further descent occurs along a line drawn from the top of the XI rib to the symphysis ossium pubis. Only at 25 years of age does the position of the caecum correspond to McBurney's point, i.e., the midpoint of the distance between the spina ilii ant. sup. and the navel. In younger age, the caecum lies above it, in older age—below it, and in senile age, the root of the caecum can descend to the boundaries of the pelvis. The colon descendens usually ends at the upper boundary of the iliac fossa, but sometimes, especially with senile downward displacement of the root of the mesentery of the sigmoid colon, a more significant segment of it may also be located there. Under the name of the ileo-cecal region, in clinical practice, the lower-right-outer part of the abdominal cavity is distinguished, in which the caecum, the vermiform appendix, and the terminal parts of the small intestine are located, and where numerous pathological processes occur and are localized. The typical form of injury to the iliac region is the so-called isolated fracture of the processes or wing of the ilium, which most often occurs as a result of direct violence acting from front to back or from the side. The lines of fracture or cracks may go in the longitudinal, transverse, or oblique directions, usually accompanied by slight displacement. The course and prognosis depend mainly on associated injuries of pelvic organs, and their absence is a favorable symptom. Gunshot fractures of the iliac fossa are usually accompanied by injury to the organs of the abdominal cavity and pelvis, which determines the severity of the injury and outcomes. With favorable course, they are sometimes complicated by osteomyelitis of the edges of the fracture, giving abscesses with sequestra on the outer or inner surface of the bone. With timely recognition of osteomyelitis, trepanation of the bone by an incision in the gluteal region is recommended in order to provide wide access for pus. Spontaneous osteomyelitis occurs rarely and, according to Przhevalsky's data, constitutes less than ¹/₃% of the total number of osteomyelitides of other bones; it proceeds violently, often with complications from pelvic organs. Treatment is surgical: either by the method described above or by opening the abscess of the iliac fossa by an extraperitoneal incision. Among tumors are found osteomas, chondromas, sarcomas with their varieties and echinococcal cysts (according to Bauer, out of 243 cases of bone echinococcosis, 72 had pelvic involvement). In their growth, they often infiltrate and compress the branches of the lumbar and sacral plexuses, causing constant severe pain. Depending on the location and course of the tumor, either its radical removal together with part of the pelvis (extensive resection of the iliac wing), or removal of half of the pelvis together with the lower limb (exarticulatio inter-ilio-abdominalis) is performed, or one is limited to X-ray and radiotherapy, adding additional surgical interventions for pain in the form of cordotomy (transection of the anterolateral pain-conducting bundle in the spinal cord).

/ Among inflammatory processes of soft tissues, special importance belongs to so-called psoitis (see Psoit). Suppurative processes in the connective tissue of the I. R. (phlegmons and abscesses) spread differently depending on their location: those beginning under the fascia iliaca spread along the course of the muscle to the thigh; those beginning above the fascia, in the retroperitoneal connective tissue, usually stop at the Poupart's ligament and only occasionally descend along the course of large vessels to the inner surface of the thigh. Tumors of soft tissues of the I. R. are most often secondary, i.e., they represent a spread of the process from neighboring organs—bones and the large intestine. When the cecum is affected by actinomycosis, a dense, woody, slightly painful infiltrate soon spreads to the soft tissues, infiltrating the I. R., compressing, and then growing into the nerves and vessels. Treatment should be as radical as possible and should not be delayed until the third stage of the disease, when pus-forming microbes appear and inflammatory phenomena join. The operation consists in excision of the affected portion of the intestine together with the soft tissues. - Opening of abscesses after psoitis or retroperitoneal phlegmon is performed by an incision in the region of Poupart's ligament, on the thigh, in the lumbar region, and sometimes on the perineum, depending on where the pus has spread. - The typical incision for exposing the I. R., including for ligation of the iliac vessels and exposure of the corresponding portion of the ureter, is the extraperitoneal incision developed by Pirogov—sectio lumbo-ilio-inguinalis. The incision is made from the apex of the angle between the XII rib and the edge of the m. sacro-lumbalis in the direction of a point located two transverse fingers above the spina ili ant. sup., and then parallel to Poupart's ligament in the direction of the tuberculum pubicum. In most cases, it is sufficient to limit oneself to part of this incision, making it in that portion where it is needed according to the conditions of the disease. The upper part of the incision serves to expose the kidney, while the middle and lower parts serve to expose the I. R. After incision of the skin and subcutaneous tissue, the m. obliquus abdominis externus, internus, and transversus abdominis are successively incised; the fascia transversalis is carefully opened along a finger or grooved probe, and the entire peritoneal sac is dissected medially and upward. If this dissection is performed following the course of the retroperitoneal connective tissue, it is easily accomplished and the I. R. is exposed over a large extent.