CLINICAL ANATOMY OF THE PREPUBIC TENDON INTHE DOG AND A COMPARISON WITH THE CAT

INTRODUCTION

n The objectives of this paper are to show in the most

detailed manner the composition of the prepubic

tendon in the dog, its relationships with the

neighboring structures and clinical correlations for

diagnosis and surgical treatment of any pathological

condition.

n This is not a comprehensive review. The paper

focused on clinically important details not mentioned

before. A review based on selected references is

suggested prior to surgery.

n The prepubic tendon is a dense mass of collagenous

tissue which serves as the attachment for the ventral

abdominal muscles on the cranial border of pubis (the

pecten of pubis).

n The prepubic tendon is a complex of tendons, mainly

of musculi pectinei and musculi recti abdominis

attached to rami craniales ossium pubis ¹,

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Cercetãri Experimentale & Medico-Chirurgicale

Anul XIV · Nr.2-3/2007 · Pag. 81-85 C e r c e t a r ie x p e r i m e n ta le &

m edico-chirurgicale

)

SUMMARY:Several authors were interested in the structure of the prepubic tendon in the dog in the lastcentury. No similar structure was found in the cat. The descriptive anatomy of the prepubictendon was either superficially or not correlated at all of to the clinical aspects of theveterinary medical profession. The implication of this structure in the pathology of the areais of high importance, considering that the physical examination and the surgical techniques should be correctly applied not only on to the prepubic tendon, but also to the neighboringstructures, such as the superficial inguinal ring and the inguinal canal with its content.

Key Words: prepubic tendon, superficial inguinal ring, dog, cat

ANATOMIA CLINICÃ A TENDONULUI PREPUBIAN LA CÂINE ÎN COMPARAÞIE CUPISICA

REZUMAT: Câþiva autori au fost interesaþi de structura tendonului prepubian la câine în secolul trecut.La pisicã nu a fost gasitã o structurã similarã. Anatomia descriptivã a tendonului prepubian a fost tratatã fie superficial, fie nu a fost corelatã cu aspectele clinice ale profesiunii medicalveterinare. Implicazþia acestei structuri în patologia ariei anatomice este de o mareimportanþã, þinând cont de faptul ca examenul fizic ºi tehnicile chirurgicale trebue sa fieaplicate corect nu numai asupra tendonului prepubian, dar de asemenea ºi asuprastructurilor vecine, ca de exemplu inelul inguinal superficial ºi canalul inguinal cu conþinutulsau.

Gheorghe M.Constantinescu1,Menolly R. Beittenmiller2,F. A. Mann3

Ileana A.Constantinescu4

Received for publication: 25.04.2007

Revised: 11.08.2007

1- DVM, PhD, mult. Drhc, Professor, Dept. of Biomedical Sciences, College of Veterinary Medicine, University of Missouri,2- Senior Student, College of Veterinary Medicine, University of Missouri3-DVM, MS, Diplomate ACVS, Diplomate ACVECC, Professor, Dept. of Veterinary Medicine and Surgery, College ofVeterinary Medicine, University of Missouri4 - DVM, MS, Clinical Assistant Professor, Dept. of Biomedical Sciences, University of Missouri

Correspondence to: Gheorghe M.Constantinescu ,Dept. of Biomedical Sciences, College of Veterinary Medicine, Universityof Missouri, 1600 E. Rollins, Columbia, MO 65211-5120 USA, e-mail: ConstantinescuG@missouri.edu

n The prepubic tendon, which has also been called

“cranial pubic ligament” similar to the “superior

pubic ligament” in humans ² serves as a point of

attachment for the ventral abdominal musculature

onto the pelvis. In this capacity the prepubic tendon

aids in the action of the abdominal press which

makes possible the acts of expiration, urination,

defecation, and parturition ³.

n This structure has been described numerous times in

the dog, but a homologous structure is not present in

the cat 4.

n It is imperative to have a thorough knowledge of the

prepubic tendon and the neighboring structures to

diagnose correctly any pathological condition and to

use the appropriate surgical technique for repair.

MATERIAL AND METHODS

Two fresh and eight embalmed dogs, three fresh and

seven embalmed cats were used in this study. The fresh

specimens were provided from a Humane Society,

whereas the embalmed specimens were first used by the

students in the dissection room, and were provided either

by different companies or embalmed in our Anatomy

Laboratory. In this case the embalming fluid had the

following formula:

1200 ml Formaldehyde

400 ml Propylene or Ethylene glycol

1000 ml Phenol

add water to 20 liters

RESULTS

According to our findings, Fig. 1 shows the superficial

level of structures beneath the skin and the

subcutaneous connective tissue. The right external and

internal abdominal oblique muscles were reflected from

the linea alba to expose the rectus abdominis muscle.

The superficial inguinal ring, the femoral lamina, the

femoral triangle and the corresponding vessels are

shown. We should first mention that at the very cranial

border of the pubic bones a poorly developed cranial

pubic ligament connects the symmetrical pecten of pubic

bones; in some cases this ligament was not present.

According to our findings, the transversus abdominis

muscle did not attach to the prepubic tendon. Its caudal

border, called “Linea arcuata” ended cranial to the pecten

of pubis. The point of attachment of the prepubic tendon

and of the aforementioned muscles on the pubis was not

the median ventral pubic tubercle. Only the medial part of

muscular fibers of the rectus abdominis muscle attached

to the ventral pubic tubercle (Fig. 2). The largest lateral

part of the rectus abdominis muscle, and the

aponeuroses of the two abdominal oblique muscles

attached to the pecten of pubis (see Fig. 2). The lateral

part of the rectus abdominis muscle was provided with

an elliptically shaped aponeurosis overlapping muscle

fibers (see Fig. 2). The aponeurosis sent fibers that

passed over and under the prepubic tendon (see Fig. 2).

The two crura of the superficial inguinal ring (from the

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external abdominal oblique muscle) were strong and

attached to the prepubic tendon and the pectineus

muscle (the medial crus to the tendon, while the lateral

crus to the muscle fibers of the pectineus) (see Fig. 2).

The prepubic tendon has been shown to extend from

the pecten to the iliopubic eminence on either side, but

little cross-over of fibers was noted in dogs. The structure

of the prepubic tendon in the dog is most similar to that

seen in ungulates; however, one significant difference

noted in the dog is the incorporation of the iliopubic

cartilage which was found to be intercalated in the

pectineus tendon 5 .

In the cat, the abdominal and pectineus muscles had

separate attachments to the pubis and thus, a prepubic

tendon does not exist. However, based on our findings

the two crura of the superficial inguinal ring were as

strong as to firmly attach on the cranial border of pubis on

both sides of the insertion of the pectineus muscle on the

iliopubic eminence (Fig. 3). We noticed three-four strong

attachments of the aponeurosis of the external

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abdominal oblique muscle on the medial aspect of the

thigh: the most lateral attachment is the continuation of

the lateral crus of the superficial inguinal ring, whereas

the other attachments originate from the medial crus of

the ring and the aponeurosis of the muscle itself ( Fig. 3).

The aponeurosis of the external abdominal oblique

muscle sent in addition a strong attachment to the tendon

of the pectineus muscle (Fig. 4).

COMMENTS AND CLINICALCORRELATES

Developmentally, the prepubic tendon is stronger in

species with a heavy abdominal mass and proportional

with the volume of the abdominal viscera, such as the

ruminants and the horses. In carnivores this structure is

less developed. The aponeurotic attachments of the

ventral abdominal muscles pull the prepubic tendon

ventro-cranially, in an angle that varies with the species

and the weight of the abdominal mass. In humans,

vertical posture changed the angle and the relationship of

the attachment of the ventral abdominal muscles. Thus,

there is no prepubic tendon in humans, but a superior

pubic ligament. The latter is attached to the superior

border of the pubic bones and joins the symmetrical

pecten of pubic bones overlapping the interpubic disc. In

addition, in humans the pubic attachment of the rectus

abdominis muscles is doubled ventrally by a dependence

of the aponeuroses of the external abdominal oblique

muscles, and dorsally by an enlargement of linea alba

called “adminiculum lineae albae” 6.

In domestic mammals the prepubic tendon is a strong

fibrous structure attached to the cranial border of the

pubic bones, between the symmetrical iliopubic

eminences. In comparison to humans the prepubic

tendon of domestic mammals allows the attachment of

linea alba and the tendons of some ventral abdominal

muscles to the pubis.

The prepubic tendon is defined by one author, not

specifically for the dog, as “a strong squared fibrous

blade attached to the cranial border of the pubic bones,

from one iliopubic eminence to the other. As a complex

structure, it extends directly the linea alba and the

tendons of recti abdominis muscles, and receives part of

the aponeurotic fibers of the symmetrical abdominal

oblique and transverse abdominal muscles. Besides, it

maintains connections, important in ungulates, with the

origin of some muscles of the thigh, such as the

pectineus and gracilis” 6. If we elim i nate “im por tant in

ungulates” and “gracilis”, the def i ni tion may by ap plied to

the dog.

Specifically for the dog the prepubic tendon is defined

by another author as “a strong collagenous mass

composed primarily of the tendons of the paired rectus

abdominis muscles and the tendons of origin of the paired

pectineus muscles. It is firmly attached to the median

ventral pubic tubercle” 3.

Our dissections showed that only the medial part of

muscular fibers of the rectus abdominis muscle attaches

to the ventral pubic tubercle and the largest lateral part of

the rectus abdominis muscle, and the aponeuroses of the

two abdominal oblique muscles attach to the pecten of

pubis.

“An iliopubic cartilage is intercalated in the prepubic

tendon at the junction between the symmetrical

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pectineus tendon and the external abdominal oblique

tendons at the caudal angle of the superficial inguinal

ring” 5.

Our dissections showed that the iliopubic cartilage is

located between the caudal commissure of the

superficial inguinal ring and the muscular, not the

tendinous part of the pectineus muscle, which should be

given a different consideration in surgery.

In the cat the strong attachments of the two crura of

the superficial inguinal ring on the cranial border of the

pubis on each side and together with the tendon of the

pectineus muscle seems to be as strong as the prepubic

tendon of the dog.

A prepubic tendon is considered not to be present in

any species in which the pectineus and adductor longus

muscles are separate including humans, primates,

rabbits and some rodents 5. This is not true, because in

some dogs the adductor longus is a muscle totally

separated from the pectineus 3.

Based on our anatomical findings and the nature of the

prepubic hernia in dogs and cats 7,8 precise

reconstruction of this anatomy after traumatic injury is

unlikely. However, reattachment of the anatomical

musculature with suture, usually through holes drilled

into the pubis, results in repair of the hernia with high

success 7. Apparently, healing with scar tissue is

sufficient to mimic the function of the prepubic tendon

and related anatomy.

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REFERENCES

1. Schaller O. et al, 1992: Illustrated Veterinary Anatomical Nomenclature, Enke, Stuttgart2. Feneis H., Dauber W., 2000: Pocket Atlas of Human Anatomy Based on the International Nomenclature, 4th ed., Thieme,

Stuttgart, New York3. Evans H.E., 1993: Miller’s Anatomy of the Dog, 3rd ed., Saunders 4. Budras K.-D.: Leistenband, Leistenkanal und M. cremaster externus der Katze. Anat. Anz. 1967, 121:148-1655. Habel R.E., Budras K.-D.: Anatomy of the prepubic tendon in the horse, cow, sheep, goat, and dog. Am J Vet Res 1992, 53, 11,

2183-21956. Barone R., 2000: Anatomie comparée des mammifères domestiques tome 2 Arthrologie et Myologie, Vigot, Paris7. Mann FA, Tangner CH, Boothe HW, Weber WJ : Cranial pubic ligament rupture in dogs and cats. J Am Anima Hosp Assoc

1986, 22, 519-5248. Friend EJ, White RAS: Rupture of the cranial pubic tendon in the cat. J Small Anim Pract. 2002, 43, 522-525