Fistula of the withers and poll-evil

Contents

FISTULA OF THE WITHERS Page

The Poll 105

Preface

There are several reasons why a manual on this disease should be a part of the veterinary literature of the day, the chief one being that fistula of the withers is a very prevalent disease of horses and thus exacts a big toll from the horse industry. Another reason for bringing it especially to the attention of readers of veterinary literature is the deplorable fact that its treatment has never been standardized in the veterinary profession. Almost all long known and common complaints of domestic animals of a serious character are handled according to definite plans, differing only in minor details. The many conferences of our teachers of surgery in association work, and the interchange of ideas made possible by the splendid periodicals which all progressive veterinarians now read, as well as the profusion of all kinds of literature that reaches everyone, has fortunately created a standard of treatment for nearly all of the more important ailments of animals.

Not so, however, with fistula of the withers. Each seems to have his own plan of treatment and few, indeed, claim even a fair degree of

G PREFACE

success. Some are satisfied with caustics, others with lancing and irrigations, others with bacterins, while a few of the more daring prefer radical surgery that removes the causative elements. To these plans might also be added that of those who avoid fistula of the withers entirely, because of the discredit meddlesome intervention generally brings them.

In every rural community of the Middle West the empiric finds a fruitful field for exploitation in the many chronic, loathsome, halfcured fistulse of the withers found in the hands of owners willing to try anything after having given up in despair the various treatments that have failed.

If this book will do no more than to inspire the veterinary practitioner to approach this ailment in a matter of fact manner and to handle it according to the common laws of modern surgical procedure; and if it will discourage a continuance of the half-hearted and always unsatisfactory methods in vogue, the effort will not have been lost. The Author.

Introduction

The disease known universally among American veterinarians as fistula of the withers is described at much greater length in the following pages than has ever been done before in veterinary literature. Most of the authors of surgical subjects have dismissed this affliction with a few words, referring to it only incidentally as an occasional complication of harness galls or other forms of trauma about the crest of the neck and withers, but always without dignifying it as an entity worthy of special notice. Its frequent origin in the bursa? on the thoracic spines of the region and its development independent of any apparent injury have only recently attracted attention. In fact, there are many who still entertain the opinion that it is but a complication of a contusion inflicted by the collar, by rolling upon hard ground, by striking against a low stable beam, by rubbing against branches of trees while at the. pasture, or by bites from other horses. Without ever having been able to attribute any given typical fistula of the withers to a given traumatism, the theory of traumatic origin has been indifferently accepted as ample explanation of its cause. Thus years have been wasted in attacking the disease from without, giving only casual attention to the "interior" of the withers where it actually originates.

We do not insist that the names "fistulous withers" or "fistula of the withers" are even good appellatives for the disease we are about to describe. On the contrary, a name less specially pathologic in its meaning would seem more appropriate, since fistula is but a phase of the entity as a whole. The name, inappropriate as it is, we retain because among our American readers it has been consecrated by so many years of usage that a change would lead to no better understanding of our exposition or argument. We retain the name, therefore, with the full knowledge that it is appropriate only for the latter stages of the disease and that the fistulae are but insignificant parts of the total pathogeny.

Poll-evil, which we argue is but the same condition attacking the atlantal bursa, has, on the contrary, been more extensively described by writers throughout the history of modern veterinary science, and although it had been referred to always as a complication of a traumatism in the earlier days, it was the first of these two diseases to be recognized as a bursitis. It has been designated as inflammation of the bursa of the ligamentum nucha? and by some writers as inflammation of the ligament itself. No one has thus far been able to prove its definite cause. Like fistula of the withers, apparently for want of an explanation based on demonstrable facts, it has always been attributed to bruisings of the poll.

While we do not entirely eliminate traumatism as the cause of some cases of poll-evil and some attacks of fistula of the withers, it has been our experience that when injuries are the cause, the wound or bruise is always apparent and the disease advances into the depths of the region by gradual stages from the initial focus deeper and deeper until the interior is finally attacked by the encroaching pyogenic process. In ordinary cases of both of these afflictions, the initial focus is always central, far down in the depths of the body where external violence can have but little influence. From this central location the disease as gradually advances in the outward direction in the ordinary case, as it does inward in the exceptional cases due to trauma. We have, therefore, no choice than that of describing both poll-evil and fistula of the withers as having two distinct causes, one a wound or bruise at the very surface, and the other, and commonest, as yet unknown.

The prevalence of fistula of the withers and poll-evil we have found to be much greater in some localities than others. In some districts it is actually an equine scourge, while in others it is a rare occurrence. In southern California, for example, veterinarians seldom if ever see a typical fistula of the withers or poll-evil, while in central Illinois it is a veritable horse plague. In a recent conversation with an old horse breeder in the latter location the information was elicited that fistula was once as rare there as in California. Asked if he had any theory to advance as to the cause he seemed inclined to attribute most cases to influenza, and colt distemper, claiming that before these diseases became prevalent from the interchange of horses from shipping centers there were no cases of fistula of the withers. The rarity of shipping fever (influenza) in California, seems to add logic to these observations.

But no matter what the cause may eventually prove to be, the veterinary practitioner is today confronted with a serious disease of horses that he must endeavor to control and handle to the better satisfaction of horse breeders and the public. To fall short of meeting this requirement is one more adverse reflection on our ability to meet the demands of our growing live stock industry. To study, to experiment with, to strive to curb, and to analyze this affliction from every angle is therefore a worthy enterprise. It is at least a problem of the rural districts of the Middle West that is neither well handled, nor, so far as we can perceive, intelligently studied.

The loss in horses in Illinois from fistula? alone reaches into the thousands. The loss to veterinarians from their helplessness in handling the cases and the discredit this state of helplessness brings to the veterinary profession are matters to be thoughtfully considered.

The fact that the treatment of poll-evil is no longer an unsolved problem in veterinary surgery, and that this treatment, now standard for more than ten years, has proved as nearly universally successful as any surgical departure can prove, and the further fact that this ailment differs from fistula of the withers only in matters governed by the location, should, it seems to us, have spurred veterinarians to resort to similar measures for handling both. The fact that the latter is located in a more complex region and requires an operation of greater magnitude is, we believe, the only reason why no advance has been made in its treatment.

Better surgery from every angle by which good surgery is judged (anesthesia, restraint, asepsis, hemostasis and wound treatment)

will, we believe, eventually solve the problem of fistula of the withers in the same way that the much simpler operation has solved that of poll-evil.

The region of the anatomy called the withers has no well defined limits. The word "withers," therefore, while academic in hippology, is not usually found indexed in text books on anatomy. It is described as to shape in the study of types, but seldom as regards to its component parts, except in surgical anatomy — a branch of veterinary science that is as yet ill-developed. The horse judge studies the profile of the withers very carefully because the general appearance of any given horse depends a great deal upon its shape, its size and the measurements of its dimensions. The surgeon studies not only its shape and dimensions, but its constituent parts as well and their complex and disadvantageous arrangement from the surgical point of view.

It is important to note that the withers may be high, low, narrow, broad, steep, sloping, long or short, and that any two or three of these characteristics combine to determine the various types of withers of different individuals. Graphic writers in describing equine types often use such terms as sharp withers, low withers, high withers, long withers, thick withers, muscular withers, effaced withers, prominent withers, each of which, in addition to being descriptive in the study of profile, is equally suggestive in the study of etiology of affections of these parts and their surgical treatment. Each one of these characteristics contributes to a different etiologic factor as well as a different surgical problem.

Boundaries

The withers, although having ill-defined limits, may be said, for surgical study, to extend from the crest of the neck anteriorly, to a point posteriorly, where the dorsal spines descend to the level of the back. The second dorsal spine may be selected as the uniform anterior limit, but posteriorly no line can be drawn, because some withers end abruptly toward the level of the back, while others slope gradually to a more distant posterior point between the eighth and twelfth spines. The highest point is almost universally at the fifth spine. The second dorsal spine may, therefore, be said to represent the anterior boundary, the fifth spine the summit and any point between the eighth and twelfth dorsal spines the posterior boundary. In the downward direction, the withers may be said to descend to the bodies of the vertebra? mesially and to the distal border of the scapular cartilage, (cartilage of prolongation) laterally. With these boundaries as a point of departure, each structure comprising the withers might be studied per se, but from the surgical point of view its study en masse is of first importance.

Component Parts

The withers are composed of skin, fascia, muscles, ligaments, cartilage, bones, blood vessels, lymphatics and nerves. These are combined in a very complex and exceedingly disadvantageous manner, since in situ they form a pyramid whose base is loosely arranged while the summit is, dense. The summit of the withers, under the skin, is composed of hard ligamentous structures fixed firmly to the underlying bones. From this point, the layers of which the region is constituted separate from each other in the downward direction, permitting thereby a ready filtration of pus into constantly deeper and more inaccessible fortresses, and constituting a favorable field for the fruitful development and undisturbed sojourn of inflammatory processes of a chronic character. The base of the pyramid is bounded laterally and ventrally by bones (the scapulae and bodies of the dorsal vertebra?) while anteriorly and posteriorly its component structures extend without change of arrangement into the neck and back. Thus pus within the withers after filtering downward finds its only exit by traveling first in either of these two directions, and ultimately to the surface of the body at points remote from the seat of development. It is this complex arrangement that affords the impregnable intrenchment of pathological products and that is responsible for the refractory character, the extreme seriousness and the unvarying chronicity of the disease known as fistula of the withers.

The Skin

The skin covering the withers possesses nothing unusual except the thickness of the subcutem along the median line anteriorly where the heavy connective tissue of the mane begins. Posterior to the summit of the withers the skin is of normal thickness, but is separable only with difficulty from the aponeurosis of the fleshy panniculus whose fixed attachment is at the level of the fourth or fifth spine. Very often, however, the skin is the seat of scars supervening harness and collar injuries which fuse it into the underlying ligaments, fascia or muscles as the location mav determine.

•J

Panniculus Carnosis (Cutaneous Muscle)

This muscular structure is a prominent feature of the withers in that its chief attachment is to the summit. Along the region of the withers its fibers, unlike those of any other part of the body, are vertical, extending downward to the proximal border of the scapular cartilage, where they find another fixed attachment. It is fused with and in fact may be regarded a part of the superficial fascia. As a structure to incise for invasions into the withers it may be so considered. Beneath the superficial fascia is another aponeurotic layer whose fibers are so arranged as to cross those of the trapezius beneath at right angles. This layer is of no special surgical importance. It is found only in a careful dissection of the region and is in no way influential in guiding pathological processes nor in shaping surgical procedure.

The Trapezius

The trapezius, excluding the fascia just mentioned, is the third layer of the withers and is really the first of the anatomical structures that must be reckoned with in the study of fistula. It is a triangular membranous muscle with its base upward running along the withers where its aponeurosis is attached to the supraspinous ligament along the withers and to the ligamentum nuchas in the cervical region, extending in all from the axis to the tenth dorsal vertebra. This triangular sheet-like structure is bisected vertically with a central aponeurosis that is attached ventrally to the tuber spinse of the scapula. The anterior part is the trapezius cervicalis and the posterior the trapezius thoracalis.

The Roof of the Withers

Together with the skin, the fascia and the panniculus carnosis, the trapezius muscles may be regarded as the "roof of the withers. 33

It is under this roof that typical fistula? of the withers develop and beneath which the atypical (traumatic) fistula? burrow in directions of resistance less than that afforded by its dense, aponeurotic character.

Rhomboideus Thoracalis

The rhomboideus thoracalis extends from the spinous processes of the second, third, fourth, fifth, sixth and seventh dorsal verte • brae in a downward and outward direction to the mesial face of the scapular cartilage. It constitutes a thick, heavy curtain forming a "second or inner roof of the withers." Compared with the structures of a building, it might be said to be a curtain, sagging slightly in the middle, that extends from the comb of the roof to a point on the wall just beneath the plate beam. It is very loosely attached to the mesial face of the trapezius laterally and to the longissimus dorsi ventrally and spinalis dorsi mesially and ventrally. Secondary abscesses of fistulas of the withers said to be located "under the scapula" are in reality located under this muscle, resting upon the longissimus dorsi but without any obstacle against the filtration of pus further down than under the upper part of the serratus dorsi. Pus seldom goes to a lower level because the latter muscle is attached firmly to the costal surface and above to the mesial face of the scapula, forming a space having a firm floor but without anterior and posterior walls.

Rhomboideus Cervicalis

The rhomboideus cervicalis is the forward elongation of the thoracalis, extending toward the head along the ligamentum nucha? as far forward as the axis. Its insertion is the anterior part of the mesial face of the cartilage of prolongation. Its surgical importance lies in the fact that its ventral margin just in front of the scapula affords a point of invasion into the seat of a typical fistula ( Fig. 2 ) . It is also so closely related to the ligamentum nucha? that it seldom escapes attack from the morbid process, and when heedlessly sacrificed in resecting the ligamentum nucha? a pronounced deformation of the crest of the neck (ewe-neck) results. It may be said to reinforce the "roof of the withers" anteriorly.

Other Structures Important Surgically

The splenitis and the serratus cervicis are related to, in fact occupy, the anterior part of the withers. They lie immediately below the rhomboideus cervicalis and beneath the trapezius cervicalis. Their upper margins are related to the former. Just in front of the cartilage of prolongation they are very loosely attached to the rhomboideus and thus afford the portal for surgical invasion above referred to. They are thick, tuberous curtain-like muscles forming the bulk of the crest of the neck and on account of their thickness prevent facile direct invasion to the bottom of pus cavities which are usually located below this margin at the level of the second dorsal spine. These two thick muscles, in short, form the lower part of the lateral walls of the pus cavity in fistula of the withers. The treatment of fistula of the withers would be a lesser problem if the pus cavity could be drained over the dorsal margin of these muscles instead of through them.

The longissimus dorsi. The longissimus dorsi at the withers occupies the space between the rhomboideus and the complexus and spinatus. These three muscles may be said for descriptive purposes to fill in the angular space formed by the ribs and vertebral spines.

Structures of Lesser Surgical Importance

The complexus anteriorly and the spinalis dorsi posteriorly have no especial surgical significance, except that the former lies closely attached both to the lamellar and the funicular portions of the ligamentum nuchas and the latter to the spines of the vertebra and are therefore implicated in disease processes, and besides being just two more structures to form channels for the burrowing of pus they in no way govern the course of surgical operations. In fact pus cavities that have formed beneath these muscles are inaccessible and disease of the structures between them (bones posteriorly and the lamellar portion of the ligamentum nuchas anteriorly) usually constitutes an incurable condition.

Viewed as a Whole

The muscles of the withers viewed with the purpose of standardizing surgical procedure against fistula may be compared to an irregularly-shaped covered trough containing a longitudinal partition. Anteriorly the trough is walled by the splenius and the serratus cervicis, posteriorly by the serratus thoracis and the scapular cartilage. Its floor is formed by the longissimus dorsi and its roof by the trapezius and rhomboideus. The central partition is constituted of the dorsal spines, spinalis dorsi posteriorly and the lamellar portion of the ligamentum nuchas covered with the complexus anteriorly. The bottom of the trough which must be reached for effectual drainage can be penetrated only with difficulty and the risk of inviting complications in structures not previously implicated. Furthermore, these muscles being in constant use in locomotion, respiratory acts and movements of the neck, tend to encourage the burrowing of pus into still more inaccessible recesses.

Thus we find the musculature of primal importance in any study of fistula of the withers. It bounds initial abscess cavities in places difficult of access for drainage, they move upon each other and favor the distribution of purulent products into new fields, where secondary abscesses are formed, and it exhibits a remarkable trend toward fibrosis under the influence of the chronic inflammation of adjacent parts.

The Ligaments

The ligaments implicated in fistula of the withers are the ligamentum nuchas and the supraspinous ligament, each of which is but a continuation of the other; the dorsoscapular ; and the interspinous ligaments, which curtain off the spaces between the spinous processes.

The ligamentum nucha? is a strong, powerful apparatus composed of yellow elastic tissue and divided into two distinct parts: the funicular portion and the lamellar portion. The former which is of especial importance in fistula of the withers and poll-evil, extends from the occipital bone anteriorly to the summit of the withers posteriorly where it becomes white fibrous tissue and is continued over the spines of the sacrum as the posterior part of the supraspinous ligament. It is composed of two lateral halves each of which is heavy and flattened at the withers but gradually becoming round and somewhat smaller toward the occipital crest to which it is attached to the occipital protuberance. Two bursa? are found associated with this structure — one at the atlas and the other in the dorsal region. The atlantal bursa is the seat of poll-evil while the dorsal or supraspinous bursa is the location of typical fistula of the withers. The atlantal lies between the ligament and the dorsal surface of the atlas. The dorsal bursa is usually over the third dorsal spine but sometimes extends backward as far as the crest, that is, over the fourth and the fifth spines, and often as far forward as the second. It is at the level of the second dorsal spine where the causative center of most of the cases of fistula of the withers that we have examined carefully, were located.

An important point to remember about the funicular portion of the ligamentum nucha? is its wide expansion posteriorly. Approaching the crest of the withers it extends in the outward and downward direction five to six inches, partly enveloping the rhomboideus and trapezius. This expanded portion is often the cause of recurrence of fistula after the main portion has been removed.

It is surmounted along its course by the "pad of the mane" a structure composed of elastic fibers interspersed with adipose tissue. It is most abundant in the middle of the cervical region and is best developed in stallions of the draft breeds.

The funicular portion is a sheet-like partition dividing the superior cervical muscles into halves. It is composed of two layers attached loosely to one another by areolar tissue, and each layer is composed of two parts, anterior and posterior. The anterior part is thick and strong, attached to the funicular portion above and to the cervical spinous proc-

Fig. 1 — Ligamentum Nuche of Horse. Note particularly the relation of the funicular portion of the ligamentum nuche to the atlas and to the spines of the thoracic vertebrae. Also the arrangement of the lamellar portion. (After Sisson.)

esses below. The posterior part is attached to the second and third dorsal spines and extends in the form of several digitations forward and downward where its brush-like fibers reach the spines of the fifth and sixth cervical segments. The fibers of the ligament are more spare than in the anterior part and sometimes do not even reach the sixth vertebra. Between the anterior and the posterior parts is a space of considerable dimensions which especially in horses of good flesh contains a mass of fatty tissue. This opening is at the level of the extremity of the second dorsal spinous process and is the seat of typical fistula of the withers. It is the space where the sacculation of fistula begins.

The supraspinous ligament is a structure composed of white fibrous tissue and extends along the dorsal region to the sacrum. It is the continuation of the ligamentum nucha? posteriorly. A careful dissection of this structure fails to show that it begins as an independent structure, as its fibers although they change in structure from yellow elastic to white fibrous tissue, are simply continuations of each other. From the surgical standpoint the supraspinous ligament and the ligamentum nuchas must be regarded as a single apparatus which changes in the character of its tissue at the crest of the withers. Over the crest it is a very thick, dense structure and along its whole course backward it is attached firmly to the summits of the spines.

The interspinous ligaments are thin membranous structures connecting the spines to one another and completely filling in the space between them from the bodies to the supraspinous ligament above, and thus completing a perfect partition between the two halves of the withers

The dorso-scapular ligament is a reflection of the superficial fascia. It is a thick aponeurosis attached dorsally to the crest of the withers and passing outward and downward under the rhomboideus to the scapula and giving off layers which pass between the underlying muscles — the longissimus and spinalis. At the crest it is really the aponeurotic origin of both the rhomboideus thoracalis and the splenius.

The importance of these ligaments in fistula of the withers lies in the fact that they are implicated in the disease more commonly than the other component parts. Lying adjacent to the initial seat of the inflammatory process, and being but poorly nourished structures, they fall an easy prey to microbic products, becoming riddled with necrotic areas and thus preventing cicatrization of contiguous abscess cavities. In poll-evil it is the anterior part of the funicular portion of the ligamentum nuchas that prevents healing, while in fistula of the withers it is the posterior end or its ligamentous continuation — the supraspinous ligament — that is implicated.

Cartilages of the Withers

The cartilaginous tissue included among the component parts of the withers is found in the scapular cartilage (cartilage of prolongation) and in the semi-cartilaginous summits of the dorsal spines.

The scapular cartilage which is attached to the vertebral border of the scapula is a wide expanse of hyaline cartilage about two inches wide extending from the cervical to the dorsal angle. It is thick at the attachment to the bone but becomes thin toward its vertebral border which presents an evenly rounded profile. Its mesial relations are the rhomboideus and the serratus ventralis and its lateral the trapezius and the attachment of the panniculus carnosis. To these muscles it is intimately related, being in fact imbedded in them. It forms the lateral wall of many of the secondary abscesses of fistula and its cervical angle and sometimes its vertebral border becomes implicated in the disease. By becoming divested of its muscular attachments and perichondrium it plays the role of a foreign body and thus perpetuates secondary fistulous tracts, which, on account of the movement to and fro are very slow to cicatrize, even after the necrotic parts have been extirpated.

Cartilage is found on the spinous processes of the third, fourth, fifth, sixth and seventh spines, but is most abundant on the fifth and sixth. To this cartilage is fused the fibers of the supraspinous ligament. When the ligament detaches from disease the cartilaginous ends lie bare and being soft often induce surgeons to indulge in reckless curetting when no such procedure is indicated. Protruding like stumps into the bottom of the abscess cavity and being slow to separate from the viable bone beneath, these cartilaginous summits are exceedingly instrumental in delaying cicatrization and a prolific source of recurrences.

Bones

The bones of the withers are the spinous processes of the dorsal vertebrae from the second to the point posteriorly where they reach the level of the back. They incline backward. They are thin at the anterior border, thick posteriorly and expanded dorsally to receive the attachment of the supraspinous ligament.

They increase in length from the first to the crest (the fifth) and then gradually diminish to the twelfth. Those immediately over the crest exhibit the cartilaginous ends above mentioned. The increase in length is not symmetrical, the second being almost twice as long as the first.

They are connected to one another by the interspinous ligaments which complete an impervious partition between the two lateral halves of the withers. Laterally they are covered with the spinalis and longissimus dorsi muscles.

The spinous processes rank high in importance in the study of fistula of the withers. The initial pathological process of typical fistula? is usually seated on the second and third segments. The cyst which constitutes the first pathological change is attached to them and when opened often exposes their cartilaginous summits. In traumatic fistulae originating from superficial wounds, these processes often become the seat of a stubborn osteitis that descends into the cancellated tissue, sometimes as far down as the bodies of the vertebra?, creating very chronic if not always incurable conditions.

The student of surgical anatomy should remember their length at the different points, their cartilaginous summits, their backward direction, their connecting media and the contiguous musculature.

Blood Vessels

The withers receives its blood supply chiefly from two sources: the dorsal and the deep cervical arteries. Both are direct radicals of the brachial arteries, or more correctly speaking, the left one arises from the left brachial artery and the right one from that part of the same vessel on the right side while it still bears the name brachiocephalic artery. The origin of both is within the thorax. The dorsal enters the region of the withers through the second intercostal space and the deep cervical, through the first. Both of them leave the thorax near the bodies of the vertebra?. Their extra-thoracic distribution alone interests us, in surgery of the withers.