THE ANATOMY OF INGUINAL HERNIA The Substance of an Arris and Gale Lecture Delivered at The Royal College of Surgeons of England by H. F. Lunn, B.Sc., M.B., F.R.C.S. Formerly Sir Halley Stewart Research Fellow, Royal College of Surgeons of England " No disease of the human body belonging to the province of the surgeon requires in its treatment a greater combination of accurate anatomical knowledge with surgical skill than Hernia in all its varieties." (Astley Cooper, 1827.) THERE NEED BE no lack to-day of surgical skill. The increased scope of surgical practice and the development of anrsthesia have provided every surgeon with the opportunity to attain a high standard of technical ability. Pressure of clinical work has, however, prevented a parallel advance along the other path which Astley Cooper regarded as essential-that of accurate anatomical knowledge. We must admit that there has been no significant advance in the under- standing of the structure of the human inguinal region during the past century. The operations of Bassini (1890), Gallie (1924) and others are all based upon the traditional conception of the anatomy of this region, handed down from the time of Falloppius (1561). Views held by many centuries of experienced observers cannot be lightly dismissed, but we do well to retain them only if they survive repeated examination in the light of modern knowledge. Perhaps in no other region are conflicting views more strongly held and contested. To one surgeon the transversalis fascia is all-important, to another it does not exist as a constant layer. Some believe that the cremaster is redundant, others that it is an essential part of the inguinal mechanism. In some clinics the patients walk on the day following operation, in others they remain in bed three weeks. One surgeon attends closely to the superficial inguinal ring and the external oblique aponeurosis, another concentrates on the deep ring. In the same issue of the British Medical Journal (August 11th, 1945) is an article deploring the relapse rate after the Bassini operation, and another claiming that this operation gives consistently the best results. In the midst of such confusion there has been evidence in recent years of an attack against the complacency which has been hampering progress. Sir Heneage Ogilvie (1937) has repeatedly stimulated original thought by reasoned criticism of traditional ideas. Harold Edwards (1943) has 285 22-2 H. F. LUNN abstracted and reviewed the mass of literature concerning inguinal hernia and its repair, and has steered a middle course through the extreme views given above. Lytle (1945) has made a useful contribution by laying emphasis on the internal abdominal ring. His description of the trans- versalis fascia does not, however, agree with the findings of Douglas (1730) and has not been widely accepted. Anson and McVay (1937, 1940) have presented a conception of the anatomy of the groin which conflicts in several respects with current descriptions, yet which is in accord with the results of the comparative approach. The inguinal canal has been studied in animals by John Hunter (1786) and by Berry Hart (1910) in relation to the descent of the testicle. Sir Arthur Keith (1923) considered the inguinal canal from a comparative point of view in relation to hernia, but he and subsequent workers (e.g., Miller, 1947) tended to restrict their studies to a comparison between man and the other primates. There is need therefore of a study of the inguinal canal in a wide series of animals, with the application of the conclusions to the problem of hernia. The following pages record the findings that have resulted from an attempt to meet this need through the approach John Hunter would have used. The Terminology of Hernia The changing language in which we have to think, to learn, and to teach, is a feature of most of the arts and sciences to-day. Structures acquire an undeserved importance when tradition honours them with a high-sounding name. There is an attack to-day upon eponyms both in anatomy and surgery. The student and the clinician alike resist dictatorship and have chosen to retain certain well-tried eponymous terms. Ligamentum inguinale is often the inguinal ligament, but more often Poupart's. Gimbernat's ligament may also be called the lacunar ligament, but rarely the more recent " pectineal part of the inguinal ligament." Thus the confusion continues. A time of change is also a time for discrimination, for retaining the use- ful and for discarding what has ceased to be effective. Should all epony- mous terms be discarded ? If the alternative is a heavily sounding Latin word or a discursive phrase, some names should indeed be spared. We are in danger of forgetting the great pioneers in anatomy and surgery when we extract all their names from our books and teaching. Hesselbach (1806) stressed the inferior epigastric artery as a landmark, but the remainder of his triangle serves no further purpose. His ligament (interfoveolar ligament, Gray, 1946) is described as a thickening in the transversalis fascia, but is best considered, together with that of Henle, as a part of the conjoined tendon (Douglas, 1890). It will not be easy to separate Gimbernat from his ligament in clinical teaching. The " pectineal part of the inguinal ligament" is too long a 286 THE ANATOMY OF INGUINAL HERNIA phrase to survive in these days of speed and brevity of expression. The alternative to the eponym is the lacunar ligament (B.N.A.), a pleasant descriptive term that still appears in Gray (1946). Colles, on the other hand, is immortalised by his fascia and does not need his reflected inguinal ligament, a structure that is found by Anson and McVay (1937) to be a rarity. The name of Nuck (1691) will probably remain attached to the processus vaginalis of the female. Few would contend the use of Sir Astley Cooper's name for his ligament of the pubis. Sir Astley did not in actual fact give the first description of this ligament, as Gimbernat (1793) had anticipated him. It was Sir Astley Cooper, however, who applied his ligament to the surgery of this area and who thus merits a place among those whose names are retained in our nomenclature. The pectineal line of the pubis is overburdened with the attachment of the pectineus, the pectineal fascia and the pectineal part of the inguinal ligament. The addition of a pectineal ligament (B.N.A. revised) will surely increase the confusion. The ligament of Cooper, if retained, would draw attention to these fibres of importance to the surgeon and to the memory of the one who contributed more to the understanding of this region than all the generations which have followed. There have also been changes in the non-eponymous terms in current use. The entry to and exit from the inguinal canal are no longer abdominal rings. Now they are inguinal rings, deep and superficial (B.N.A. revised), although the older terms, abdominal and subcutaneous inguinal rings (B.N.A.) are also employed. The tendons of the internal oblique and the transversus abdominis become fused near their attachment to the pubis and are now termed the conjoint tendon. This is better than the falx inguinalis aponeurotica of the B.N.A., but I must express a gramma- tical preference for the old conjoined tendon. The classification of inguinal hernia is far from satisfactory. Maclise (1853) and Sir Heneage Ogilvie (1937) have drawn attention to the contradictions created by the terms direct and indirect. An indirect or oblique hernia may stretch the medial edge of the deep inguinal ring so that it emerges almost directly behind the superficial ring. The funicular type of direct hernia may enter the inguinal canal via a defect in the conjoined tendon and pass obliquely along the cord towards the scrotum (Ogilvie, 1937). A congenital or infantile type of hernia may first appear in adult life and the former kind may be acquired. Should such confusing terms be retained for longer than the hundred years which have already passed since Maclise suggested relating hernie to the inferior epigastric artery ? This artery is accepted as the surgeon's landmark in the diagnosis of hernia. The neck of the sac is either lateral or medial to this vessel. Hernia could therefore be classified as congenital or acquired medial hernix, and congenital or acquired lateral hernie, depending on opinion as to their aetiology. 287 H. F. LUNN A Note on'the Attiology of Herniia The elastic tissue forms membranes in the walls of hollow organs upon which a changing pressure acts from within, as in the largest arteries, in some parts of the heart, in the trachea and bronchi." (Maximov and Bloom, 1942.) The abdomen can be included amongst the hollow organs upon which a changing pressure acts from within. By experiments on skin and arteries, John Hunter demonstrated the presence of elastic tissue before histology and chemistry had revealed the nature of the substances concerned. If such tissue is present in the skin and subcutaneous layers of the abdomen, we would expect to find it also in the fascial and muscular layers beneath. The abdomen as a whole enlarges in ascites and pregnancy, the enlarge- ment including a stretching of the rectus sheath and linea alba. Yet after tapping of the ascites and after delivery, these structures return to their normal length if not overstretched. Thus it would not be surprising to find that the abdomen, subject to changing pressures as is an artery, had a similar structure in its walls. Routine histological examination reveals that a deep as well as a superficial elastic layer supports the anterior abdominal wall, particularly in the region of the conjoined tendon.