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Anatomy

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ANATOMY. On examination of the abdomen, we are at once reminded of the striking difference between it and other great visceral cavities, owing to the lack of bone in its walls. The outline of the anterior wall constitutes an oval, whose long axis is vertical, protected superiorly at the sides and back by the false ribs. Posteriorly, it is divided into two sym metrical halves by the lumbar portion of the spinal column, whose transverse processes afford strong points for the attach ment of muscles which occupy the otherwise unprotected space between the ribs and the iliac crests. Superiorly, the broad expansions of the ilia, completed behind by the promontory of the sacrum, support a. portion of the abdominal viscera. The remainder of the support is afforded by the parts which enter into the composition of the abdominal parietes. The abdominal wall presents a hexagonal-shaped figure bounded above and laterally by the costal cartilages of the six lower ribs, behind by the transverse processes of the lumbar vertebra, and below by the iliac and pubic crests, united by Poupart's ligament. This is the accessible area, the locality in which incisions are made through contractile walls always active, and maintain ing such a uniform degree of pressure on the contained organs that displacements and alterations of position are of rare oc currence, excepting when they occur through some preter natural opening.

The different layers are entitled to consideration.

The skin is a common habitat for pyogenic organisms. This should be remembered, and the most painstaking care exercised in the disinfection of the field of operation. The growth and activity of these organisms is greatest where the hair is most abundant and the sweat-glands are most numerous, as around the umbilicus, the mons veneris, and, in very corpu lent persons, the deep transverse grooves, one of which crosses and conceals the navel, while the other is located immediately above the fat of the pubes.

The superficial fascia consists of two layers,—the outer. in many individuals, attains a considerable thickness, espe cially in the lower abdomen, the situation of the classical inci sion for operations on the uterus and its appendages, the blad der, and the appendix vermiformis.

The rule is to provide plenty of room by making a long skin incision and carrying it through both layers of the super ficial fascia, thus enabling the operator to deal with the essen tial elements, the muscles, aponeuroses, and nerves. A long skin incision does not influence the mortality, nor does it in crease the liability to hernia.

Muscles and Aponeuroses. The great strength of the abdominal parietes is due to the thickness and the arrangement of the muscular lamella and their aponeurotic expansions. In the anterior and lateral walls we find on each side five muscles, of which three are vertical, two in front, the rectus and pyra midalis, and one posterior, the quadratus lumborum ; while between these two vertical planes there is a quadrilateral space filled in by three muscular layers, the external oblique, internal oblique, and transversalis, whose fibres cross one another in a more or less oblique direction. This arrangement of the muscular fibres serves to keep the organs in their normal posi tion with reference to each other, and the contraction of these fibres causes approximation of the muscular elements and movable bony boundaries, thus offering the greatest degree of opposition to the demands of intra-abdominal pressure.

The fleshy fibres of the external oblique descend with varying obliquity ; the upper fibres terminating in aponeuroses opposite a curved line which extends outward from the promi nence of the ninth costal cartilage to the front of the iliac crest, while the lower fibres pass almost vertically from the lower ribs to the anterior part of the crest of the ilium. The aponeu rosis or tendinous expansion of this muscle attains considerable thickness towards the lower part of the abdomen, where great strength is requisite to sustain the viscera.

The fleshy fibres of the internal oblique also diverge ; the upper fibres extending obliquely inward and terminating op posite the outer border of the rectus, where they become aponeurotic and ensheathe the upper three-fourths of that muscle. The two layers unite in the middle line and blend with the fibres of the aponeurosis of the corresponding muscle of the opposite side.

The fleshy fibres of the transversalis end above and be low, nearer the outer border of the rectus than do the central fibres of the muscle, which are more or less scattering. From a practical stand-point, they may be regarded as a portion of the internal oblique, and may also serve as a useful guide to avoid the division of the abdominal intercostal nerves.

The rectus muscle arises from the crest of the os pubis and is enclosed by the aponeurosis of the lateral abdominal muscles for its upper three-fourths. In its lower fourth the aponeurosis passes in front, while the transversalis fascia alone separates it posteriorly from the subperitoneal areolar tissue and peritoneum. As it ascends to the chest, it leaves a space of increasing width where the component fibres of the aponeuroses blend to form the strong tendinous band called the linea alba.

The external border is convex, to compensate for the lack of muscular substance between its outer border and the meni ally concave lateral muscles. This insufficiency is due to the separation of the tendinous expansion of the internal oblique to enclose the rectus, and is known as the linea semilunaris.

The transversalis fascia is a dense aponeurotic membrane, thicker below than above, to compensate for a deficiency of muscular and tendinous supports. This condensed tissue forms the posterior sheath of the rectus along its lower fourth, where strength is especially required. It is always a useful guide in opening the abdomen, as beneath it rests the extraperitoneal tissue, which is the only structure that separates it from the parietal peritoneum,—a membrane best identified by noting the separate layers that have been cut through. If this practice be adopted, adherent peritoneum need not confuse the operator.

Nerves. The abdominal muscles, either whole or in part, are helpless, and therefore useless without their nerve supply. One cannot reflect on the structure of the abdominal wall with out admiring the great precision with which the nerves are supplied to these muscles. They are supplied with branches running in the connective tissue which bind together the bun dles of muscular fibres, and these, finally, end so that every muscle fibre is supplied with one or more nerve fibres.

The anterior continuations of the abdominal intercostal nerves take their course, from the anterior end of the inter costal spaces between the internal oblique and transversalis muscles, to the sheath of the rectus which they perforate, and, after supplying that muscle, terminate in cutaneous branches near the linea alba. These nerves end independently, and do not anastomose with the nerves of the opposite side, nor, in all probability, with the nerves of the same side.

The nerve supply of the abdominal muscles is derived from the seventh to the twelfth intercostal inclusive, together with the ilio-inguinal and iliohypogastric.

For surgical purposes, I wish to separate these nerves into three distinct groups, according to their course and the areas of the abdominal parietes supplied by them. The seventh and eighth pursue an obliquely ascending transverse course and are distributed to the upper third of the abdominal wall. The ninth and tenth pass transversely inward to the middle third of the abdomen. The eleventh and twelfth inter costals, iliohypogastric and ilio-inguinal nerves, descend in an obliquely transverse direction to supply the lower third of the abdomen.

If the nerve be severed, that portion of the muscle distal to the seat of division is deprived of its power of contractility ; its blood supply is diminished, it wastes, weakens, and, in response to the demands of intra-abdominal pressure, all the overlying structures stretch, and hernia will inevitably result. Close suturing and accurate apposition of like structures will not prevent it ; the recumbent position for a longer period of time than the customary three weeks does not lessen the lia bility, nor is any external appliance effective.

Intact, innervated muscular fibre is the only safeguard against hernia.

In view of these facts, therefore, confirmed by clinical experience, the first rule should be to make the abdominal in cision parallel, or nearly parallel, with the direction of the motor nerves and of the most important muscular fibres sup plied by these nerves.

In the consideration of the incision, the following im portant points must be taken up : (I) The length is largely dependent upon the thickness of the superficial fascia ; it must be sufficient to allow free access to the muscles whose functional integrity is essential to success.

(2) The length must be relatively greater when muscular fibres are to be separated instead of divided.

(3) It must vary with the pathological condition for which the operation is performed.

(4) An opening of sufficient size must be secured for thorough exploration and to obtain the requisite degree of pre cision and rapidity in manipulation.

(5) A long incision through the skin and superficial fascia does not predispose to hernia.

(6) It lessens the mortality by providing ample space for the protection of surrounding viscera.

(7) It lessens shock by diminishing the time required for the operation, and also the duration of the anaesthesia.

Therefore the rule should be : Let the incision be long enough to provide every facility for thorough work through muscular fibres and nerves which have been separated rather than divided.

Guided by the principles above enunciated, I will now consider the incisions which I have found most useful.

Incision No. i begins about two fingers' breadth below the xiphoid appendix, gives ready access to the stomach, and through it most of the operations on this viscus may be done. The distance from the bony margins is sufficient to permit ample mobility to meet the requirements of a movable stom ach,—a feature well marked under conditions which demand operation. Provision of operating space is one of the leading requisites, and, in order to secure this, it may be necessary to incise one or both of the recti muscles transversely. This will give the freest possible access in pylorectomy with the minimum injury to the motor nerves. The additional trans verse scar, which is not unlike the line transversx in structure, does not interfere with the contracture of the muscle. The vertical incision over the rectus with separation of the muscu lar fibres, which has been recommended so highly, is a failure, but is not so disastrous in its results as is a vertical incision along the outer border of the rectus : in the former, that por tion of the muscle internal to the line of separation is deprived of its motor-nerve supply; in the latter, we deliberately cut off the motor supply of that portion of the muscle which cor responds to the area of distribution of the divided nerves.

Incision No. 2 is made to the left of the rectus muscle parallel to and a little below the costal arch. It is directly op posite the stomach, and gives access to the vicinity of the car diac orifice in the operation of gastrostomy. The incision cor responds with the direction of the fibres of the internal oblique, and permits separation of these fibres in their normal oblique arrangement together with their motor nerves, thus providing a muscular sphincteric action around the base of the diverticu lum of the stomach or the future esophagus, thereby prevent ing the escape of food. Howse and others recommend that the parietal incision pass vertically through the fibres of the rectus muscle in order to obtain a sphincter-like action (In cision No. 8). From what has been said before it is readily seen that such a vertical incision through the muscle must divide the terminal branches of the intercostal nerves, and that consequently the portion of the muscle distal to the divided nerves must undergo paralysis, and cannot enter into the sphincteric action desired,—a provision more desirable than the liability of ventral weakening. The much employed ver tical incision in the line of the linea semilunaris has nothing to recommend, but much to condemn it.

Incision No. 3 is from four to six inches in length, and is three fingers' breadth below the costal margin, the centre of which corresponds to the apex of the tenth costal cartilage. This incision permits the separation of the fibres of the internal oblique together with the upper abdominal intercostal nerves, both of which can be separated after division of the external oblique, thereby giving easy access to the gall-bladder. The exigencies of operations in this region at times demand a large opening for inspection of deep underlying structures, and under these conditions it may be necessary to make a vertical incision along the linea semilunaris.

Incision No. 4, as recommended by McBurney, is de servedly popular owing to the care it takes in avoiding muscu lar fibres and their contained motor nerves, and consequently the prevention of post-operative hernia. Most surgeons agree that fewer cases of hernia follow operations in which this di vision is made than any other operation on the appendix. Originally, this incision was intended for non-suppurative cases in which drainage was not required, but the success which has followed the application of the principles involved in making it has caused its almost universal employment in ap pendicitis, including those cases with abscess formation and those in which drainage is required. The method is almost ideal in the class of cases for which it was recommended by the originator, and those who have attempted to adopt it in every case should not argue against its usefulness.

Incision No. 5. The difficulties I experienced in reaching the appendix through the McBurney incision in acute suppura tive cases caused me to devise another method of approach in a more dependent part. This incision overlies the outer border of the cxcum and leads directly to the appendix. It is slightly curved outward and downward, crossing an imaginary line drawn between the anterior superior iliac spines. The centre of this curve is from an inch to an inch and a half to the inner side of the right superior iliac spine. The skin and superficial fascia are incised for about two inches. This freely exposes the aponeurosis of the external oblique, which is sepa rated by means of the dry dissector, or the handle of a scalpel, in a direction parallel to its fibres, and well retracted. This brings into view the transversely arranged fibres of the internal oblique and transversalis muscles and the twelfth abdominal, iliohypogastric, and possibly the ilio-inguinal nerves, all of which are retracted in order to reach the transversalis fascia, which, together with the peritoneum, is divided transversely. The advantages to be gained by this incision are : ( ) It provides easy access to the diseased area.

(2) It enables the operator accurately and securely to pro tect the peritoneal cavity from infection.

(3) It lessens the liability of breaking down the inner limiting wall of adhesions.

(4) It affords a better opportunity to open the abscess cavity from the outer side.

(5) It favors drainage.

(6) It has not been followed, in the author's experience, by either appendicular fistula or post-operative hernia.

The urgent necessities of the case may require division of the muscular fibres, but the experienced operator, conscious of his ability to deal with whatever he may find within, will seek to establish, step by step, a living innervated muscular barrier against ventral hernia, the most important sequel to surgery of the appendix.

Want of space embarrasses the operator, and should not be tolerated, because at any time during the progress of the operation he can enlarge the opening along anatomical lines to a sufficient extent to approach accurately any abscess cavity in the iliac fossa, or to make any other manipulation that may be required in the exposure and removal of the appendix.

Incision No. 9 in the linea semilunaris tends to draw the wound apart by reason of muscular action on the outer side and inaction due to paralysis of a portion of the rectus on the inner side. Incision through the fibres of the rectus is not quite so unfavorable in its results as regards hernia, yet it divides the motor nerve. It is applicable only in non-suppura tive cases, as it cramps the opening, and as enlargement by incision or separation in either direction leads away from the seat of the disease.

Incision in the median line offers no advantages, and should be abandoned except in cases of ruptured abscess and diffusion of pus in the free peritoneal cavity, and then washing can be best carried out and drainage established.

Incision No. 6 divides the united aponeurosis of the rectus muscle, together with one or both of its sheaths, owing to the practical absence of linea alba below the umbilicus. This is a fortunate provision, inasmuch as hernia would take place more often were it not that the parallel muscular fibres are directly involved in the healing process, thereby adding strength to a situation where all the resistance possible must be offered against intra-abdominal pressure.

This incision is employed more often than any other, and I wish to insist on a strictly accurate median incision, avoiding the separation of muscular fibres and nerves. A shorter in cision through fascia enables the surgeon to carry out both exploration and treatment to the best advantage, and yet favors him with parallel muscular fibres to facilitate approximation.

Incision No. 7 is recommended by Kelly through the um bilical ring, where the abdominal wall is thinnest, from absence of fat and muscular tissue between the skin and peritoneum. In the very corpulent it lessens the danger of suppuration during convalescence and of hernia thereafter. Should it be carried above the umbilicus, care should be taken to incline it towards the left in order to avoid the suspensory ligament of the liver.

Appropriate to the subject, and in keeping with the prin ciples enunciated, I wish to consider briefly the treatment of ventral hernia. From the foregoing, you will observe that I regard this condition as a stretching not only of the scar tissue, but of all the tissues of the abdominal wall at the site of its occurrence. In the median line the covering of the hernia is stretched cicatrix, skin, superficial fascia, aponeurosis, and peritoneum, together with more or less separation of the recti muscles. If it occurs in the extra-median portion of the parietes, the coverings are stretched cicatrix, together with all the other tissues in the vicinity of the scar.

Ventral hernia takes place through tissues deficient in or devoid of innervation. Restoration by substituting another cicatrix through fascial tissues is useless. To remedy this breach, it is necessary to excise the redundant and atrophic tis sues, bringing into the wound area as much muscular fibre as possible. It is not always necessary to enter the peritoneal cavity.

Analysis of the histological structure of the cicatrix shows that it is made up of fibrous tissue throughout its depth; there fore we should make every effort to increase the bond of union by bringing into the wound area as much tissue as possible for approximation. This can be better done by the use of a modified mass suture which in no way interferes with the accurate apposition of like structures.

In closing the abdominal wound, I first unite the peri toneum by a continuous suture of fine catgut ; I then employ a well-curved, stout, Hagedorn needle armed with silkworm gut. The needle enters the skin about a quarter of an inch from the edge of the incision, passes into and through the superficial fascia, including muscular tissue and associated fibrous struc tures, picks up the subperitoneal areolar tissue and peritoneum near the border of the wound. The needle is again introduced on the opposite side, passing through like structures in reverse order. After all the sutures are in place and hxmostasis ac complished, the wound is raised by means of the sutures in the hands of an assistant, while the operator removes the protecting gauze and ties the sutures.

incision, fibres, nerves, muscular, abdominal, muscle and muscles