South African Medical JournalSuid...Afrikaanse Tydskrif vir GeneeskundeP.O. Box 643, Cape Town Posbus 643, Kaapstad

Cape Town, 22 January 1955Weekly 2s. 6d. Vol. 29 No. 4

OBTURATOR HERNIA

R. SINGER, P. M. LEARY AND N. G. HOFMEYR

Department of Anatomy, University of Cape Town

Kaapstad, 22 Januarie 1955Weekliks 2s. 6d.

Obturator hernia is the commonest of the rare ab­dominal and pelvic herniae which clinically form agroup occurring -in less than 1% of all abdomino­pelvic herniae.1 First described by De Ronsil in 1724,it has at various times also been called subpubic hernia,thyroidal hernia and hernia through the foramen ovale.By 1907, 200 cases had been reported in the literature,and by 1947 just over 400 cases were on record. Apreoperative diagnosis was rarely made until recentyears and the operative mortality is variously given as'more than 30%' 2 and 'approximately 75%'.1

MATERIAL

Our attention was drawn to thiS condition duringroutine cadaveric dissection of the pelvis in the AnatomyDepartment, and a subsequent survey was made of theavailable dissected specimens. A total of 44 cadavericspecimens were examined, of European, Cape Colouredand South Mrican Negro (Bantu) origin.

RESULTS AND DISCUSSION

Incidence: It is usually stated of clinical cases that mostof the patients are over 60 years of age, though obtu­rator hernia has been recorded even in a child of 12years. 3 . The sex ratio in 400 cases is a preponderanceof 6 : 1 in females, the difference being attributed topregnancy and the larger obturator foramina in thefemale. In addition, it is obvious that in repeatedpregnancies the parietal peritoneum becomes 'stretched'with subsequent increased relaxation.

In our small series, 14 cadavers were females and 30were males. Obturator 'herniae' were found in 9 fe­males (64 %) and 7 males (23 %), a total incidencetherefore of 16 out of 44 specimens (36 %). In all in­stances the herniation was bilateral.

This very high incidence cannot be directly comparedwith clinical impressions of the frequency of the con­dition, for these 'herniae' are really protrusions of

aggregated subperitoneal fat covered by extraperitonealloose connective tissue, which constitute 'pilot tags' ofa pre-hernial condition (Fig. I). However, Anson etaf:4 found no case of serious hernia into the obturatorcanal in 360 body-halves (i.e. 180 cadavers) and only6 instances (3 %) of preperitoneal protrusion.

It is difficult to account for this marked discrepancyin these incidences, and an investigation will now beundertaken to determine whether there are any markedstructural variations in the size, shape and angulationof the obturator foramen and canal in the variousracial groups studied and in the cadavers examined.

The age-range of the specimens examined and ex­hibiting herniation was:

Males: 63-77 years (average 70 years)Females: 34-92 years (average 69 years).

Previous investigators have remarked that the con­dition usually presented in emaciated individuals, butwe found as many cadavers with a fair amount of fatin the tissues as those without fat, and those withoutfat were 'thin' or 'not fat' rather than 'emaciated' or'wasted'.

It is not possible to trace in which o( the specimenssymptoms had been present, which may have referredto the presence of hernjation, but none of the 'pilottags' had true sacs containing intestines, fallopiantubes or ovaries, and none were strangulated.

ANATOMY (NORMAL AND IN HERNI.....TIO )

ormally the obturator (or thyroid) foramen liesbelow and medial to the acetabulum. Its longer axisis directed downwards and outwards and is rather morevertical in the male than in the female-a feature whichwe believe also contributes to the greater female inci­dence. Its margins are sharp for the attachment of thefibrous obturator membrane, which closes the openingexcept opposite the obturator groove superiorly whereit converts the groove into a canal. The obturator

73

74 S.A. MEDICAL JOURNAL 22 January 1955

IN FERIOR EPIGASTRICARTERY

(WITH PUBIC BRANCH)

Fig. 1. Dissection of a pelvis exhibiting an obturator 'hernia', with diagrammatic representation of major features.

CANALNERVE

OBTURATOR ARTE.RYVEIN

Fig. 2. Dissection indicating an enlarged internal orifice of the obturator canal, out of which a 'pilot tag' has been pulled,with diagrammatic representation.

22 Januarie 1955 S.A. TYDSKRIF VIR GENEESKUNDE 75

nerve (lying supero-lateral) and artery enter this fibro­osseous canal above the attachment of the parietallayer of pelvic fascia (obturator fascia) to the obturatormembrane (Fig. 2). The obturator canal is about 3 cm.in length and just capable of admitting the tip of theli ttle finger.

In our series the length of hernia or 'pilot tag' variedfrom 0· 5 to 2· 5 cm. (average 1· 5 cm.), and on its inneraspect the peritoneum was ~y ad~erent ~nd in­va!Iinated in such a way as to gIVe the unpresslOn thata true sac was beginning to form. These hernial tagswere all fairly firmly fixed in the obturator canal andin all but one case were found medial to the nerve andvessels (Fig. 2). In the one specimen, the tag was infer<?­lateral to the nerve and vessels. The anastomoS1Sbetween the pubic branches of the obturator andinferior epigastric arteries was on the medial aspect ofthe 'neck' of the hernia (Fig. 1). Aird 2 states thatsometimes the fasciculi of the obturator nerve may bespread over the surface of the sac or the sac may emergebetween the anterior and posterior branches of thenerve.

If the hernia is progressive it emerges above theobturator externus muscle and comes to lie deep topectineus. If it extends no further it cannot be palpated.Beyond this, however, it may be located betwee.n thepectineus and adductor muscles in the femoral tnangleand may be mistaken for a femoral hernia.

Picque and Poirier 5 classified obturator herniae into3 varieties:

1. In the obturator canal. The sac of the herniapasses thro1!gh the canal and emerges under cover ofpectineus muscle. This is the commonest type.

2. Between the middle and superior fasciculi of theobturator externus muscle. The course of the sac inthis type is along the route taken by the inferior branchesof the obturator nerve and artery, the fundus of the sacpassing between the superior and middle fasciculi ofthe obturator externus muscle.

3. Between the external and internal obturatormembranes. This is the rarest form of hernia, the sacpassing downwards and forwards between the internaland external (superficial) obturator membranes. Thesuperficial part of the obturator membrane consistsof a transverse band attached laterally to the transverseligament of the acetabulum and lateral border of obtu­rator foramen, and medially to the ramus of the pubis.The sac cannot be freed here unless this superficialpart of the obturator membrane is ex.cised. . .

At operation the sac usually contams small mtest~ne

(rarely large intestine), faIlopian tubes or ovanes.Strangulation is a common complication and waspresent in the majority of reported ·cases. A Richter'shernia is not unusual in this situation, producing thesigns of only partial strangulation.

SIG 's AND SYMPTOMS

Strangulation of a hernia which is presenting deep tothe pectineus muscle will produce a vague mass on themedial side of the thigh. The patient keeps the thighflexed so as to relax the pectineus, and attempts to

produce extension will cause severe pain. Adductionof the hip joint is also resisted because this movementtends to squeeze the hernial sac against the obturatorexternus muscle.

Pressure on the obturator nerve may be referredalong the geniculate branch of the posterior divisionof the nerve to the postero-medial aspect of the knee,and/or pain may be referred to the antero-medialaspect of the thigh via the cutaneous branch of theanterior division of the obturator nerve, which ends inthe subsartorial plexus.

In the absence of strangulation, the HOlVship-Rom­berg syndrome is characteristic of obturator hernia,namely, a tingling or burning sensation or pain alongthe antero-medial aspect of the thigh and around theknee joint aggravated by straining or coughing, but notby movements of the hip joint. Digital vaginal orrectal examination may confirm suspicions of an obtu­rator hernia. A surgeon should consider such a diag­nosis in elderly females with vague abdominal painsassociated with intermittent pain in the thigh muscles.Von Zwalenburg 6 stated that he successfully operatedon an emaciated female· of 76 years, who had beencomplaining for 26 years of recurrent colicky painsIow down in the abdomen and radiating to the thighs.He found a mass of fat adhering to the fundus of thehernial sac.

An accurate pre-operative diagnosis was made inless than 20% of the reported cases and obturatorhernia has been mistaken for femoral hernia, adenitis,psoas abscess, varicose veins, phlebitis and hip jointdisease.

SUMMARY

Obturator 'pilot tags' or 'herniae' were detected bi­laterally in 16 of 44 cadavers examined. The ratio offemale to male was 3 : I and the average age for thecondition was 69 years in females and 70 years inmales. These figures are compared with those pre­viously reported.

The normal anatomy of the obturator canal and itsrelationships is described, and the relationship of thevarious types of obturator herniae to these structuresis indicated.

The aetiology and symptomatology of obturatorherniae are also dealt with. Clinical presentation ofthe condition is very rare.

Thanks are due to Mr. G. McManus, the Department of Surgery,University of Cape Town, for the photographs.

REFERENCES

I. Christopher, F. (1947): A Textbook ofSurgery, 4th cd. revised.Philadelphia: W. B. Saunders Co.

2. Aird, 1. (1949): A Comparison in Surgical Studies, p. 543Edinburgh: E. & S. Livingstone Ltd.

3. Wakeley, C. P. G. (1939): Brit. J. Surg., 26, 515.4. Anson, B. J., McCormack, L. J. and Cleveland, H. L (1950)

Surg. Gynec. Obstet., 90, 31.5. Picque, Land Poirier, P. (1891): Rev. Chir., 11,956 (quoted

by Wakeley 3).6. Von Zwalenburg, C. (1913): Surg. Gynec. Obstet., 16,422.