MILITARY MEDICAL MANUALS

General Editor:

SIR ALFRED KEOGH, G.C.B., M.D., F.R.C.P.

ARTIFICIAL LIMBS

ARTIFICIAL LIMBS

BY

TRANSLATED AND EDITED BY

R. C. ELMSLIE, M.S., F.R.C.S.

Major R.A.M.C.(T.F.)
Orthopædic Surgeon to St. Bartholomew's Hospital, Surgeon to
Queen Mary's Hospital, Roehampton

WITH 208 ILLUSTRATIONS

UNIVERSITY OF LONDON PRESS, Ltd.

18 WARWICK SQUARE, LONDON, E.C. 4.

PARIS: MASSON ET CIE

120 BOULEVARD SAINT-GERMAIN

1918

GENERAL INTRODUCTION

The infinite variety of injuries which any war presents to the surgeon gives to military surgery a special interest and importance. The special interest and importance, in a surgical sense, of the great European War lies not so much in the fact that examples of every form of gross lesion of organs and limbs have been seen, for if we read the older writers we find little in the moderns that is new in this respect, but is to be found in the enormous mass of clinical material which has been presented to us and in the production of evidence sufficient to eliminate sources of error in determining important conclusions. For the first time also in any campaign the labours of the surgeon and the physician have had the aid of the bacteriologist, the pathologist, the physiologist and indeed of every form of scientific assistance in the solution of their respective problems. The clinician entered upon the great war armed with all the resources which the advances of fifty years had made available. If the surgical problems of modern war can be said not to differ sensibly from the campaigns of the past, the form in which they have been presented is certainly as different as are the methods of their solution. The achievements in the field of discovery of the chemist, the physicist and the biologist have given the military surgeon an advantage in diagnosis and treatment which was denied to his predecessors, and we are able to measure the effects of these advantages when we come to appraise the results which have been attained.

But although we may admit the general truth of these statements it would be wrong to assume that modern scientific knowledge was, on the outbreak of the war, immediately useful to those to whom the wounded were to be confided. Fixed principles existed in all the sciences auxiliary to the work of the surgeon, but our scientific resources were not immediately available at the outset of the great campaign; scientific work bearing on wound problems had not been arranged in a manner adapted to the requirements, indeed the requirements were not fully foreseen; the workers in the various fields were isolated, or isolated themselves pursuing new researches rather than concentrating their powerful forces upon the one great quest.

However brilliant the triumphs of surgery may be, and that they have been of surpassing splendour no one will be found to deny, experiences of the war have already produced a mass of facts sufficient to suggest the complete remodelling of our methods of education and research.

The series of manuals, which it is my pleasant duty to introduce to English readers, consists of translations of the principal volumes of the "Horizon" Collection which has been appropriately named after the uniform of the French soldier.

The authors, who are well-known specialists in the subjects which they represent, have given a concise but eminently readable account of the recent acquisitions to the medicine and surgery of war which had hitherto been disseminated in periodical literature.

No higher praise can be given to the Editors than to say that the clearness of exposition characteristic of the French original has not been lost in the rendering into English.

MEDICAL SERIES

The medical volumes which have been translated for this series may be divided into two main groups, the first dealing with certain epidemic diseases including syphilis, which are most liable to attack soldiers, and the second with various aspects of the neurology of war. The last word on Typhoid Fever, hitherto "the greatest scourge of armies in time of war," as it has been truly called, will be found in the monograph by MM. Vincent and Muratet which contains a full account of recent progress in bacteriology and epidemiology as well as the clinical features of typhoid and paratyphoid fevers. The writers combat a belief in the comparatively harmless nature of paratyphoid and state that in the present war hæmorrhage and perforation have been as frequent in paratyphoid as in typhoid fever. In their chapter on diagnosis they show that the serum test is of no value in the case of those who have undergone anti-typhoid or anti-paratyphoid vaccination and that precise information can be gained by blood cultures only. The relative advantages of a restricted and liberal diet are discussed in the chapter on treatment, which also contains a description of serum-therapy and vaccine-therapy and the general management of the patient.

Considerable space is devoted to the important question of the carrier of infection. A special chapter is devoted to the prophylaxis of typhoid fever in the army. The work concludes with a chapter on preventive inoculation in which its value is conclusively proved by the statistics of all countries in which it has been employed.

MM. Vincent and Muratet have also contributed to the series a work on Dysentery, Cholera and Typhus which will be of special interest to those whose duties take them to the Eastern Mediterranean or Mesopotamia. The carrier problem in relation to dysentery and cholera is fully discussed, and special stress is laid on the epidemiological importance of mild or abortive cases of these two diseases.

In their monograph on The Abnormal Forms of Tetanus, MM. Courtois-Suffit and Giroux treat of those varieties of the disease in which the spasm is confined to a limited group of muscles, e. g. those of the head, or one or more limbs, or of the abdomino-thoracic muscles. The constitutional symptoms are less severe than in the generalised form of the disease, and the prognosis is more favourable.

The volume by Dr. G. Thilbierge on Syphilis in the Army is intended as a vade-mecum for medical officers in the army.

Turning now to works of neurological interest we have two volumes dealing with lesions of the peripheral nerves by Mme. Atanassio Benisty, who has been for several years assistant to Professor Pierre Marie at La Salpêtrière. The first volume contains an account of the anatomy and physiology of the peripheral nerves, together with the symptomatology of their lesions. The second volume is devoted to the prognosis and treatment of nerve lesions.

The monograph of MM. Babinski and Froment on Hysteria or Pithiatism and Nervous Disorders of a Reflex Character next claims attention. In the first part the old conception of hysteria, especially as it was built up by Charcot, is set forth, and is followed by a description of the modern conception of hysteria due to Babinski, who has suggested the substitution of the term "Pithiatism," i. e. a state curable by persuasion, for the old name hysteria. The second part deals with nervous disorders of a reflex character, consisting of contractures or paralysis following traumatism, which are frequently found in the neurology of war, and a variety of minor symptoms, such as muscular atrophy, exaggeration of the tendon reflexes, vasomotor, thermal and secretory changes, etc. An important section discusses the future of such men, especially as regards their disposal by medical boards.

An instructive companion volume to the above is to be found in the monograph of MM. Roussy and Lhermitte, which embodies a description of the psychoneuroses met with in war, starting with elementary motor disorders and concluding with the most complex represented by pure psychoses.

SURGICAL SERIES

When the present war began, surgeons, under the influence of the immortal work of Lister, had for more than a quarter of a century concerned themselves almost exclusively with elaborations of technique designed to shorten the time occupied in or to improve the results obtained by the many complex operations that the genius of Lister had rendered possible. The good behaviour of the wound was taken for granted whenever it was made, as it nearly always was, through unbroken skin, and hence the study of the treatment of wounds had become largely restricted to the study of the aseptic variety. Septic wounds were rarely seen, and antiseptic surgery had been almost forgotten. Very few of those who were called upon to treat the wounded in the early autumn of 1914 were familiar with the treatment of grossly septic compound fractures and wounded joints, and none had any wide experience. To these men the conditions of the wounds came as a sinister and disheartening revelation. They were suddenly confronted with a state of affairs, as far as the physical conditions in the wounds were concerned, for which it was necessary to go back a hundred years or more to find a parallel.

Hence the early period of the war was one of earnest search after the correct principles that should be applied to the removal of the unusual difficulties with which surgeons and physicians were faced. It was necessary to discover where and why the treatment that sufficed for affections among the civil population failed when it was applied to military casualties, and then to originate adequate measures for the relief of the latter. For many reasons this was a slow and laborious process, in spite of the multitude of workers and the wealth of scientific resources at their disposal. The ruthlessness of war must necessarily hamper the work of the medical scientist in almost every direction except in that of providing him with an abundance of material upon which to work. It limits the opportunity for deliberate critical observation and comparison that is so essential to the formation of an accurate estimation of values; it often compels work to be done under such high pressure and such unfavourable conditions that it becomes of little value for educative purposes. In all the armies, and on all the fronts, the pressure caused by the unprecedented number of casualties has necessitated rapid evacuation from the front along lines of communication, often of enormous length, and this means the transfer of cases through many hands, with its consequent division of responsibility, loss of continuity of treatment, and absence of prolonged observation by any one individual.

In addition to all this, it must be remembered that in this war the early conditions at the front were so uncertain that it was impossible to establish there the completely equipped scientific institutions for the treatment of the wounded that are now available under more assured circumstances, and that progress was thereby much hampered until definitive treatment could be undertaken at the early stage that is now possible.

But order has been steadily evolved out of chaos and many things are now being done at the front that would have been deemed impossible not many months ago. As general principles of treatment are established it is found practicable to give effect to them to their full logical extent, and though there are still many obscure points to be elucidated and many methods in use that still call for improvements, it is now safe to say that the position of the art of military medicine and surgery stands upon a sound foundation, and that its future may be regarded with confidence and sanguine expectation.

The views of great authorities who derive their knowledge from extensive first-hand practical experience gained in the field, cannot fail to serve as a most valuable asset to the less experienced, and must do much to enable them to derive the utmost value from the experience which will, in time, be theirs. The series covers the whole field of war surgery and medicine, and its predominating note is the exhaustive, practical and up-to-date manner in which it is handled. It is marked throughout not only by a wealth of detail, but by clearness of view and logical sequence of thought. Its study will convince the reader that, great as have been the advances in all departments in the services during this war, the progress made in the medical branch may fairly challenge comparison with that in any other, and that not the least among the services rendered by our great Ally, France, to the common cause is this brilliant contribution to our professional knowledge.

A glance at the list of surgical works in the series will show how completely the ground has been covered. Appropriately enough, the series opens with the volume on The Treatment of Infected Wounds, by A. Carrel and G. Dehelly. This is a direct product of the war which, in the opinion of many, bids fair to become epoch-making in the treatment of septic wounds. It is peculiar to the war and derived directly from it, and the work upon which it is based is as fine an example of correlated work on the part of the chemist, the bacteriologist and the clinician as could well be wished for. This volume will show many for the first time what a precise and scientific method the "Carrel treatment" really is.

The two volumes by Prof. Leriche on Fractures contain the practical application of the views of the great Lyons school of surgeons with regard to the treatment of injuries of bones and joints. Supported as they are by an appeal to an abundant clinical experience, they cannot fail to interest English surgeons, and to prove of the greatest value. It is only necessary to say the Wounds of the Abdomen are dealt with by Dr. Abadie, Wounds of the Vessels by Prof. Sencert, Wounds of the Skull and Brain by MM. Chatelin and De Martel, and Localisation and Extraction of Projectiles by Prof. Ombredanné and R. Ledoux-Lebard, to prove that the subjects have been allotted to very able and experienced exponents.

Alfred Keogh.

PREFACE

No attempt is made in this little book to describe all the artificial limbs and appliances that have been invented. Before the war these were very numerous, since then their number has become countless, and not a day passes without the appearance of some new model of greater or less ingenuity.

But all these special inventions, the utility of which we should not think of denying, are only of real practical value if the makers have followed out certain general principles in their manufacture. In the following pages we have attempted to indicate what these principles are.

Our experience has been gained in connection with the Fédération des Mutilés, where hundreds of disabled men have been examined and fitted, and where we have always tried to give to each that appliance which is best suited to his work.

For this indeed is the vital principle, and great disappointments will result if, for æsthetic reasons, every patient is given the same appliance, whether it be the leg known as the American leg or an elaborate artificial arm. More often than might be believed accurate imitation of the external form of the natural limb is incompatible with good functional use. This is particularly so in the upper limb.

Perhaps the readers of these pages will gain a clear understanding of these principles; and we shall have attained our object if by enabling them to understand certain typical appliances we make it possible for them to devise others which are at the same time strong, shapely and practical.

Throughout the volume it will be found that we express a preference for the construction of artificial limbs for the lower limb out of wood, the method adopted by the Americans. This procedure, because strength and durability are so necessary, seems to us to constitute a very real advance; these considerations are, however, of much less importance in the case of the upper limb. It is a matter for regret that the French official instructions have not compelled our manufacturers to adopt this technique, too often the latter are inclined to keep to their old routine, but they can be induced to alter it, as we have proved by our success at the Fédération des Mutilés.

There is nothing revolutionary in such a suggestion. It has been adopted by the Belgian Government in the fitting centres which they have established; this is also the case with the English authorities, who, we understand, have even attracted from America special fitters for this work. We should have thought that we, in France, might have developed our national supply of artificial limbs in the same direction.

INTRODUCTION TO THE ENGLISH EDITION

The details of the manufacture of artificial limbs naturally differ greatly in different countries. So much so that at first sight it might appear useless to introduce into England and America the account given in this work of the methods adopted in France. But, as the authors state in their preface, the principles remain the same whatever the details of the methods used. In the lower limb the essentials to be studied are the points upon which weight can be taken, the "Bearing Points," the proper method of fitting the stump, the principles of securing stability and the mechanism of the knee and ankle joints. These remain unalterable whatever be the material used and whatever be the details of manufacture.

In England it has for a long time been understood that every sailor or soldier who has lost a limb has the right to expect that he will be supplied with a good artificial substitute. And, further, it has been taken for granted that this will, in the case of the lower limb, be a full artificial leg and not a peg leg. Therefore the standard pattern has in England been a full limb, and the peg has only been supplied as a temporary appliance, and as an alternative appliance to be used when the other limb requires alteration or repair. For this reason the possibilities of the peg leg, except in its simplest form, have perhaps been neglected in this country, and a study of the French methods of making these peg legs, particularly the convertible peg leg, is well worth while.

The introduction of American artificial legs into this country has not been so revolutionary in its results as it is apparently in France, for we have been accustomed for many years to make the bucket out of a single piece of willow. The alterations in our methods introduced recently from America are essentially the following—

1. The use of a sling which passing over the shoulders is attached to the leg below the knee in such a way as to act as a mechanism for extending the knee.

2. The manufacture of the leg portion out of a single piece of wood.

3. The abolition of the old tendon action for the ankle joint (which resembled the mechanism described on [page 57]) and its replacement by the ankle with movement limited by indiarubber buffers.

4. Covering the wooden part of the limb with a layer of raw hide or parchment, which certainly adds to the strength.

The sole remaining problem in the design of artificial legs appears to be the invention of a knee mechanism which will lock in any degree of flexion when a strain is put upon it, so that the wearer does not necessarily fall when his weight comes upon the limb with the knee flexed. A recent invention, still on its trial, seems to indicate that this problem is not incapable of solution.

In artificial arms the differences between the French and English patterns are greater than in artificial legs. But here again the principles remain the same. In England, also, we have worker's arms and show arms, but the latter tend to be more elaborate than the French patterns, mechanical movements being more developed. For this reason this pattern is usually called, in England, the mechanical arm. Instead of the single cord, looped round the opposite shoulder, and used to open the spring thumb (see [p. 101]), at least three such cords are used, actuated (1) by rounding the back; (2) by expanding the upper part of the chest, and (3) by raising or lowering the shoulder on the side of the amputation. These may be used for various purposes, of which the chief are (1) flexing the artificial elbow; (2) working the elbow lock, and (3) actuating the thumb, fingers or appliances used instead of the hand. The chief other differences in the methods adopted in England are—

1. A smaller enclosure of the shoulder region for purposes of suspension, the limb being held on by a harness of straps. We, in fact, value mobility of the shoulder, and gain it at the expense of stability.

2. The use of various alternative patterns of elbow locks.

3. The appliances used instead of the hand are very different in pattern, although the principles for their construction remain as described here by the authors.

Much ingenuity has been expended on the design of mechanical artificial hands, with results which are satisfactory so far as they go, but which require much further development before the hand can possibly replace even a few of the appliances which can be substituted for it. For this reason it should be made an invariable rule that the artificial hand, however ingenious and however apparently perfect it may be, should be detachable, so that it may be replaced by other appliances.

R. C. E.

CONTENTS

ARTIFICIAL LIMBS

CHAPTER I

GENERAL CONSTRUCTION OF AN ARTIFICIAL LIMB

A prosthetic apparatus for any amputation is composed of two parts:

1. The artificial limb.

2. The attachment of this limb to the trunk.

The artificial limb itself is divided into two parts:

1. A conical socket.

2. A part which replaces the missing limb and is in fact a terminal functional appliance.

Two conditions must be considered, whether or not there remains attached to the trunk a segment of the limb capable of being fitted into the base of the artificial limb, to which it gives support, and to which, in addition, it can communicate movement. Accordingly the artificial limb differs essentially for:

1. Disarticulation of the shoulder and of the hip.

2. Amputation of the arm and of the thigh.

In the first case we attach to the trunk an instrument which is entirely passive.

In the second we attempt to turn to account the active movements of the stump.

These various parts do not lend themselves to a general description applicable at once to the upper and lower limbs. Not only are the modes of attachment and the functional artificial limb quite different, but the bucket does not serve the same purposes.

The position of the scar.—The stump, which fits the bucket exactly, transmits to it two kinds of force:

1. The force of vertical pressure.

2. Lateral force corresponding to the angular movements of the joint above.

The lateral force is transmitted by the whole of one surface of the stump to the corresponding lateral surface of the bucket: by the anterior and posterior surfaces only in the case of hinge joints such as the elbow and the knee: by all surfaces in the case of joints with movements of circumduction such as the shoulder and the hip.

Vertical pressure exercised upwards or downwards may cause the limb to press upon the bucket at two points: (1) on the summit of the cone, i.e. on the extremity of the stump; (2) on the base of the cone, i.e. on the bony prominences around the last remaining joint. The adjustment is never sufficiently accurate for the relief due to the fitting of the stump in the bucket to be of much importance.

We should take it as a general rule that a scar cannot stand pressure or friction; and that in consequence, when we amputate under favourable conditions, we should arrange to place the scar in such a position that from our knowledge of the suitable prosthetic apparatus these two evils will be avoided. It should be added, however, that after perfect primary union, the narrow and mobile scar is very tolerant, but it must also be remembered—especially as will be seen in the lower limb—that this condition is rarely realised in war surgery.

The length of the stump is often estimated by reference to that of the other limb; amputation at the upper, middle, or lower third of the thigh, of the leg, of the arm, or of the forearm. This is convenient, starting from a certain minimum length, but there is an absolute minimum length below which the stump has insufficient leverage and tends moreover to escape from the bucket.

Temporary and permanent apparatus.—For the irregular amputations of war surgery which have suppurated, more often than for those of civil practice, it is generally advisable, particularly in the lower limb, to use a temporary apparatus, of fairly good fit, for several weeks or even months before the permanent apparatus of more precise fit. The stump has to soften and shrink gradually; only when this has occurred can we make an accurately fitting bucket, by means of a cast if necessary.

Materials for making the bucket.—The first method of construction is that of leather reinforced with metal; a sheath strengthened with metal supports, is laced around the stump; the supports further give attachment, if there is room, to the artificial joints. This is an excellent principle, either for stumps which are still likely to diminish in size, or for the upper limb where exact fit is of secondary importance.

For buckets accurately fitted on a cast we employ:

Blocked leather, which loses shape and ought to be abandoned for artificial limbs for the lower extremity.[1]

[1] This we have attained at the Fédération des Mutilés, having forced the makers to abandon their routine. It seems to us therefore that the same result might be attained for the appliances furnished by the State, which are still made of leather.

Celluloid is the material of choice, but it has the defect of requiring the hand of an artist; commercial attempts on a large scale have so far yielded mediocre results.

Metal (zinc, sheet steel, aluminium), the defect of which is that the apparatus, particularly for the lower limb, is noisy. This is also an inconvenience in the metal joints of lateral steels of leather appliances and of the spiral springs in certain wooden apparatus, for this reason indiarubber is more often relied on for springs and accumulators.

Wood, for many years used for the commoner types of limbs for the lower extremity, is now, as the result of American influence, utilised for the making of apparatus hitherto termed "de luxe," but to-day serviceable, thanks to this technique.[2]

[2] Working in wood, to hollow out of a log of wood a bucket which fits the stump accurately, is no novelty. Some sixty years ago two Frenchman, Bailly, then Xavier, succeeded in such construction. But these appliances, like the common, cheap unshaped peg leg, split easily and were only made strong when the Americans conceived the idea of covering the outer surface with a layer of raw hide: strong, and therefore practical, for though we may resign ourselves to the frequent renewal of a peg leg at 25 francs, it is another matter with an appliance costing 300 to 400 francs. (Prices in peace time.)

(In England the standard patterns of artificial legs have for many years been made out of wood.—Ed.)

The adjustment to the stump is very exact; the contact with the surface where there is friction is soft and comfortable without padding; the appliance is light, strong and silent. The best woods appear to be English willow and lime. The bucket should not present any flaw or knot, this can be seen on the inner uncovered surface.

But we must emphasise the general fact that standardisation is impossible when the bucket is made of wood. For the other parts it is possible but not for the bucket, which must be made specially for each patient, hollows being made for each bony point, which must be marked out and felt for with the fingers. A plaster cast would appear more exact: but by this means we do not mark out the bony points. Good results cannot be obtained, if, as certain people have tried, linear measurements are sent to a workshop whence an apparatus is forthwith despatched to a patient whom the maker has never seen.

CHAPTER II

GENERAL PRINCIPLES OF FITTING FOR THE LOWER LIMB

Whether we are dealing with an amputation of the leg or an amputation of the thigh, the principle function of the artificial limb is to support the weight of the body. The bucket must therefore give support to this weight. Three bearing points are thus possible: at the base, upon the surface and upon the end of the stump.

1. Bearing upon the base.—The principal bearing is that which is taken by fitting the upper edge of the bucket under the bony prominences situated around the last joint preserved, i.e. the tuberosity of the ischium for the thigh, the head of the tibia for the leg.

2. Bearing upon the surface of the stump.—Certain makers attribute to this an importance which we believe to be imaginary, but which leads them to erroneous conclusions.

It is evident that if a conical stump which is jointless and which transmits the weight is fitted exactly, point downwards, into a conical bucket, supported below by a vertical pillar, the weight is transmitted by the friction of the part enclosed against the bucket, without any pressure upon the free end. Whence it may be concluded that, as the end of the stump should not serve as a bearing point, we should prefer a terminal scar to lateral scars which might be rendered painful or even ulcerated by friction against the bucket.

But experience shows us that if the pressure of the bucket at this point is harmful to the lateral scars, it is not less so for most terminal scars.

The stump in its bucket is in fact a bone, furnished with soft parts upon which we cannot exert vertical pressure, without squeezing them back towards the base of the stump, thus exerting an upward tension of the terminal soft parts over the end of the bone. This is bound to occur unless there is a considerable length of soft parts beyond the end of the bone, that is unless more bone has been sacrificed than was necessary. In this way we get all the disadvantages of an end bearing without its advantages.

3. Direct end bearing.—This is only the principal bearing in certain special stumps which we shall indicate in due course; in some of these it is the sole bearing. In the case of apparatus for the usual amputations, above the epiphyseal enlargements, it is never more than a complementary or accessory bearing, although a very useful one.

To take pressure upon the end of the stump it is only necessary to stretch across the bucket at the right height a piece of material covered with felt. If the apparatus is made of leather, the support is taken upon a circular band of metal fixed to the lateral steels.

In order that direct pressure upon the stump may be possible, two conditions are indispensable: that there is no terminal scar; and that the extremity of the bone is well covered with a thick and nonadherent flap. Actually walking directly on the stump does not involve simply support by pressure, but also inevitable friction, of greater or less importance, caused by the backward and forward movement. This is only realised under the most perfect conditions if the skin is adapted by its structure to this movement. This is the case with the sole of the foot: where the epidermis and dermis are thick and the subcutaneous areolar tissue and deep fascia, continuous with it, enclose little cavities filled with globules of fat; these form a cushion, like little globules of liquid gliding over each other. The skin of the point and of the posterior surface of the heel is less suitable anatomically than that of the sole: it is, however, good, and it is for this reason that after amputation above the malleoli, it is possible to walk directly upon the cut surface of the tibia.

Nevertheless skin which is not prepared in this way by its normal structure can adapt itself to pressure and friction, provided that it is padded by a thick muscular layer, sheathed whenever possible with fibrous tissue. A skin which is not so lined, especially in fair and stout people, with thin and delicate skin, ulcerates easily as the result of friction or even of simple pressure, and bursæ and callosities form. See what happens to the skin on the dorsum and outer side of the foot in the case of talipes equino varus. The muscles of the flap will not remain over the bone in the condition of muscular tissue, they become fibrous—but they are useful because:

1. They interpose a fibrous layer of greater or less thickness between the bone and the skin, so that the latter remains movable over the end of the bone and is not directly compressed;

2. They adhere to the cut section of the bone forming a tendinous insertion, which renders their action on the bony lever more powerful.

A flap bears weight badly when the muscles have retracted around the bone, over which there is then nothing but skin. It is the same when the flap is stretched tightly across the end of the bone, the soft parts must remain soft and free.

Among the hundreds of cases of amputation of the leg or thigh that have passed before us in being fitted at the Fédération des Mutilés, there were many in which the presence of a terminal scar rendered the fitting of an apparatus difficult; we have never found this the case with a lateral scar; we have never seen the latter ulcerate rapidly as the result of pressure or friction in a properly made wooden bucket. So that it cannot be admitted that the proper covering of a stump is ever a matter of secondary importance.

Consequently we should consider, as a matter of principle, the circular method of amputating only as a last resort, and we ought to arrange the section of the soft parts so as to cover the end of bone as adequately as possible, and to bring the scars to one side.

We realise that in practice war surgery often necessitates deviations from the ideal. We often find ourselves in a dilemma—either the stump must be good but too short; or, being long, must be poor or even bad.

In the special case of the thigh, circular amputation in the lower third when it is carried out through healthy tissue and has not suppurated can be trimmed and sutured in such a way as to give an excellent scar, which is transverse and slightly posterior. In this situation after these routine amputations, a linear scar which is supple and has healed by first intention, separated from the bone by a good cushion of muscular and fibrous tissue, causes little embarrassment, whatever its position; at the end of a few months it stands pressure and friction without harm. But we are considering war surgery and consequently we are often called upon to fit stumps in which the cicatrix is large, hard, and more or less irregular, in which the bone has suppurated and in which the neighbouring soft parts are indurated and scarred. These stumps are not, however, the results of the work of the worst surgeon.

Amputating through infected parts, resigning himself to healing by granulation and subsequent trimming by operation, he must take time and trouble to attain in the end a result which is good functionally, although at first sight unsightly. But it is this surgeon who is on the right road, rather than he who sends us good stumps which have not suppurated, because he has amputated through the thigh for a wound of the middle of the leg, or through the leg for a wound of the foot or even of the front of the foot.

It is clear, that for the stump effectually to play its part of a lever in its bucket, a certain definite length is necessary; and we ought to do everything possible to secure a length of at least 15 to 20 centimetres in a thigh stump, or 10 to 12 centimetres in a leg stump. But when this length is secured, there is no great functional difference between, for example, an amputation of the leg in the lower third or in the lower quarter, particularly if the fitter understands how to utilise direct end bearing. The knowledge of this is of capital importance to the surgeon called upon to carry out secondary operations upon imperfect stumps, in determining whether it is possible to put an immediate stop to suppuration by drastic shortening, or whether he must preserve length and lose time by curretting the foci of inflammation in the bone.

CHAPTER III

ARTIFICIAL LIMBS FOR AMPUTATIONS THROUGH THE THIGH

There are two entirely different modes of fitting:

I. For amputations above the condyles, in which weight must always be borne upon the tuberosity of the ischium through the top of the bucket.

II. For amputations through the condyles (or for disarticulation of the knee) in which a direct end bearing may suffice.

I. Apparatus with Bearing upon the Ischium

(Amputation above the condyles.)

In the construction of an artificial limb for amputation through the thigh two entirely different principles may be used, according as it is desired to make the patient walk upon a rigid shaft, that is to say upon a peg, or upon an artificial leg proper, in which the knee bends in walking (known as the American leg).

But whichever principle is adopted, whatever material is chosen, wood or leather, and however exact the fit in the bucket may be, certain common rules govern:—

1. The shape of the top of the bucket by which it is fitted to the top of the thigh and its bearing upon the ischium.

2. The attachment of the limb to the trunk.

To begin with we shall consider these two questions, and then temporary and permanent apparatus, the peg leg and the full artificial limb, will be described.

I. The Shape of the Top of the Bucket

The tuberosity of the ischium is the sole bony point which can prevent the ascent of the limb when weight is applied. This tuberosity is situated in the posterior part of the perineum ([Fig. 1]), the anterior part of which is unable to stand pressure. It is necessary, therefore, to clear this part by cutting down the inner border in its anterior part, forming a perineal concavity, which rises posteriorly against the ischium ([Fig. 3]).

It is essential that the ischium should not be able to slip inside the bucket, otherwise the inner border will come in contact with the perineum: therefore the diameter of the bucket must be less than that of the limb, so that the ischium may rest upon its upper edge.

If the bucket is too large, the patient abducts the stump, so as to lower the inner border and prevent pressure on the perineum; he carries the leg away from the side as he walks, and this is both unsightly and fatiguing.

When an apparatus is completed, it is very easy to ascertain the site of the pressure on the ischium. The limb being put on, the ischium is fixed between the thumb and first finger, and it can then be ascertained whether it rests on the edge of the bucket or lies within it. This can be determined more exactly, if whilst the fingers which mark the position of the ischium are kept within the bucket, the patient is told to raise his stump.

If the bucket is sufficiently narrow, it may be circular without the excavation for the perineum ([Fig. 2]). But this shape is unsatisfactory for another reason, because it results in a tendency for the limb to rotate inwards.

At the moment when the artificial limb is coming in contact with the ground as it takes a step, the pelvis is oblique (the iliac spine of the sound side lying posterior to that of the amputated side). The sound limb as it executes its step is carried forwards, and the pelvis which was oblique in one direction now becomes oblique in the opposite direction. This movement is transmitted to the femur in the stump, so that the artificial limb turns inwards relatively to the stump. With each step this rotation becomes little by little more perceptible, and after a time the patient is obliged to correct it by turning the artificial limb with his hand.

If, on the other hand, the front of the upper border of the bucket slopes downwards and inwards at an angle of about 45 degrees, when as a result of its weight the bucket turns inwards as the limb is swung, the base of the stump will come against a higher part of bucket; but when the pressure of the weight of the body returns, the stump, being forced into the bucket, will descend again along this slope, that is to say a passive external rotation of the artificial limb will be brought about, correcting at every step the tendency to internal rotation.

Figs. 1 and 2

Fig. 3

In the upright position the rami of the pubis and ischium, between which stretches the perineum, slope downwards and backwards at an angle of about 45° with the horizontal. The tuberosity of the ischium bounds the perineum posteriorly, and is its lowest point. The rami of the pubis and ischium, corresponding to the genito-crural fold, mark the boundary between the thigh and the perineum. These bones are unable to stand the pressure of an artificial limb.

If the top of the bucket is narrower than the circumference of the top of the limb, measured below the ischium, it may be circular and still give support to the ischium, which will not slip into it. If the ischium does slip into the bucket, the result will be that it no longer serves as the support, the pressure coming instead upon the rami of the pubis and ischium and upon the perineum.

The constriction thus exerted upon the top of the stump may easily become insupportable. The correct solution of the problem is to cut down the upper border of the bucket opposite the perineum, letting it rise again posteriorly beneath the tuberosity of the ischium, and gain a good support there.

The same slope may be given to both edges of the bucket ([Fig. 5]). This obliquity in the posterior part serves no useful purpose: it is better on the contrary to lower the posterior border combining this semioblique fitting with a rise beneath the ischium and a depression under the perineum ([Fig. 6]).

These conditions are easily carried out in a wellmade wooden bucket, represented in [figures 8 and 9], in which it may further be seen that from the front it is convex outwards; from the side, convex forwards ([Fig. 9]). This form, which is that of some good American appliances, ought to be generally used.

The curve outwards, by drawing away the soft parts from it, frees the region of the ischium and allows the tuberosity of the ischium to press upon the bucket ([Fig. 8]).

If the thigh piece is curved forwards, and particularly if the limb is built with a very slight flexion of the knee, the stump remains slightly flexed at the hip and the patient feels as if he is sitting in the apparatus.

When the thigh piece is straight, an uncomfortable pressure is produced by the edge of the bucket against the ischium. It may be added that extension of the hip is very often impaired, particularly in patients with a short stump: The extensor muscles being divided, the flexors cause contraction into a flexed position, the more so the shorter the stump is. If the thigh piece is straight, the short stump cannot follow the movement of extension necessary in walking; it slips out of the bucket if the anterior lip of the latter is too low.

The principles are the same for the leather bucket, known as the French pattern.

Figs. 4,5 and 6

Figs. 7,8 and 9

Figure 4 shows the circular bucket (almost always too large) of the poor man's peg leg, attached to the body by a belt which is fastened to a projection upwards from the outer side of the bucket. Figure 5 shows the oblique bucket, with symmetrical anterior and posterior borders. Figure 6 one with the anterior border oblique, the posterior border being cut away. Figure 7 shows the double obliquity, downwards and backwards, of the bucket. The convexities of the bucket and thigh piece, in the type which we consider to be the best, are shown in figure 8 (convexity outwards), and figure 9 (convexity forwards).

In this the thigh piece is strengthened by two lateral steels (to the lower end of which is fixed the leg piece) joined posteriorly by a semicircular cross piece on which the ischium should rest ([Fig. 13]).

Figs. 10 and 11

The usual form hitherto has been that shown in figure 10. The cross piece was horizontal and formed simply a posterior semicircle; the lateral steels were straight. Consequently in this pattern these steels form a cone, in which the soft parts are not compressed on the inner side, nor drawn outwards, as in the apparatus previously described. Further, as long as the stump is not shrunken, the ischium covered on its inner side by soft parts sinks into the bucket, and it is the perineum which becomes the point of pressure ([Fig. 11]). Made of leather, the perineal concavity soon loses its shape and really no longer exists. Finally the bucket is circular, with the faults inseparable from that shape ([Fig. 12]).

In cases where it is felt necessary to employ leather, all these faults are easily corrected, by giving the cross piece the shape which we have described for the wooden bucket, and by prolonging it forwards through two-thirds of the corresponding circumference, in the shape of an oblique bucket. (Dotted line in [Fig. 12].)

If it is not strengthened, an oblique border of leather gives way, and after a few months' use allows rotation. The leather which extends from the termination of the metal ascends very steeply towards the trochanter, whilst the posterior border of the bucket, which is horizontal, curves downwards on the inner side to form the perineal concavity.

Figs. 12,13 and 14

The ordinary leather bucket is mounted upon two lateral steels, which are joined by a posterior cross piece (Fig. 13). This framework is shown in [figure 10], and covered with leather in figure 12. If the lateral steels are straight and divergent, this has all the defects of the straight circular bucket. The concavity for the perineum, cut out of the leather, soon loses its shape. It is, however, easy to shape the cross piece as shown in figure 14, with a perineal concavity and the anterior border oblique, following the dotted line in figure 12. By doing this and curving the steel uprights appropriately, the correct form of the wooden bucket can be copied exactly in a leather and steel apparatus. Such a correct apparatus is shown in [figures 15 to 18].

In [figure 14] is seen the metal framework; in figures 15 and 16 that of the apparatus covered with leather; in figure 17 the support upon the ischium; and the possibility of making this appliance identical with the wooden bucket will be observed ([Fig. 18]).

Figs. 15 and 16

Figs. 17 and 18

II. Mode of Suspension

Suspension of the thigh piece is essential, and is all the more important when the stump is short and consequently more liable to slip out of the bucket. For this purpose support may be taken either from the waist, upon the prominence of the iliac crests, or from the shoulders by means of braces. In the case of a long stump (amputation below the middle of the thigh) only one of these methods is necessary, we shall describe the usual methods:

The waist belt (French system) for leather appliances.

Braces (American system) for appliances of wood.

If the stump is short a combination of the two methods is best.

Figs. 19 and 20.—Simple pelvic suspension, with details of the joint at the hip.

A. Suspension by means of a waist belt.—For the peg leg made of leather the best method consists in placing a pelvic plate, which is attached to the hip steel, below the iliac crest (Figs. 20 to 24). A belt attached to the extremities of this plate surrounds the pelvis and passes above the iliac crest on the other side. The thigh piece is attached to this support, on the outer side, by articulation of the outer femoral steel with the hip steel; on the inner side, by a perineal strap. Braces complete the method of suspension of the apparatus (Fig. 21).

Fig. 21.

The axis of the metal joint between the outer femoral steel and the lower end of the T piece should be directly above the great trochanter ([Fig. 20]).

The femoral steel often breaks in the neighbourhood of this joint ([Fig. 23]); we have got over this difficulty by adding immediately beneath it a joint which allows of abduction ([Fig. 19]). A perineal strap limits this movement.

Fig. 22.

Fig. 23.

Suspension from the pelvis.

A metal hip piece is fixed below the iliac crest and held in place by a belt which passes above the iliac crest of the opposite side ([Figs. 20 to 24]). This piece is attached to the thigh bucket by a joint shown in [figure 19] (see also [Fig. 22]), which allows both flexion and abduction of the hip, and which forms the suspension of the outer side of the limb. The inner border is suspended by means of a perineal strap, shown in [figures 21 and 22]. In figure 21 is shown how a suspending brace may be easily added. Figure 23 shows the action of a single hinge joint, allowing only flexion and extension at the hip joint. On [page 27] will be seen similar joints which, however, move on the pelvic attachment as well as on the thigh piece. The object of this is to prevent the pinching of the abdominal wall by the top of the thigh bucket when the patient sits. It is indispensable in short stumps. On [page 21] will be seen a joint which allows abduction of the hip, and thus relieves the strain upon the hinge joint; without it the latter is easily broken.

B. Suspension by means of braces (American method).—The American method of suspension has the advantage of leaving the pelvis free; the patient does not feel the pull of the hip piece. Besides, when the belt is used, if the patient sits down, the buttock on the side of the stump is raised, to an extent corresponding to the thickness of the bucket, an obliquity of the pelvis, which is both uncomfortable and unsightly, being produced. The braces being relaxed in the sitting posture, the patient can avoid this inconvenience; for the stump may be slipped partly out of its bucket, the upper extremity of which is then beyond the level of the edge of the chair. This position is very comfortable, because it is normal, but the patient must replace his stump in the bucket whenever he stands up.

Figs. 24 and 25

Braces composed of straps passing over the shoulders and down the front, attached to the bucket by buckles. Posteriorly they are joined together by a cross strap between the scapulæ, and beyond this are continued in the form of elastic straps.

This form of suspension is essential for those artificial limbs with a free knee-joint, in which, as we shall see, the braces serve to extend the joint.

We illustrate here two methods of attaching the braces to the thigh piece, that which we use in the limb supplied by the Fédération (Figs. 24 and 25) and that which is used in the American limb of Marks (Figs. 26 and 27).

Fig. 26.—Braces which end below in looped thongs of leather.

Fig. 27.—These loops, held in to the thigh piece by passing beneath a loop of leather, pass over two pulleys about the middle of the inner and outer sides of the thigh piece respectively. The outer brace tends to abduct the limb if it is tightened.

C. Combined method of suspension.—If the stump is short the artificial limb must be attached both by a belt and by braces; the latter should be 5 to 6 centimetres wide.

Fig. 28.

Fig. 29.

Fig. 30.

Combined suspension for short stumps.

Fig. 28.—Complete appliance.

Fig. 29 and 30 show the value of a flexion pivot between the hip piece and the pelvic plate. If there is no such pivot, the T piece undoubtedly rotates upon the belt, but not to a sufficient extent to prevent the thigh piece in rising and pinching the abdominal wall (Fig. 29). If there is a double joint the hip piece becomes oblique, thrusting the thigh piece forward and allowing the patient to sit erect (Fig. 30).

In these cases also, to prevent the stump escaping from the bucket when the hip is flexed, the front of the thigh piece is carried as high as possible; but if the appliance is furnished with a metal T piece, such as has been described ([Fig. 29], see also [Fig. 23]), then this raised border prevents flexion of the hip by coming in contact with the abdominal wall when the patient sits down. This difficulty can be got over by making the top of the T piece movable; when the patient sits down the vertical piece of the T becomes oblique, the thigh piece comes forward, allows the stump to escape a little way and no longer presses against the abdominal wall ([Fig. 30]).

The belt may also be replaced by a leather corselet, having fixed to it the hip piece that we have just described.

The braces by themselves are a poor method of attachment for a short stump.

In the sitting position the stump easily escapes from the bucket.

When the patient is standing the stump remains abducted, whilst the apparatus, as the result of its own weight hangs vertically, in this swaying position the lower extremity of the stump presses against the outer side of the bucket, whilst the inner edge of the bucket cuts into the flesh at the top of the thigh.

III. Walking on a peg leg and similar appliances

The rigid peg and the jointed peg.—The peg leg is a rigid rod, ending in a slight enlargement, which transmits the weight of the body, resting by means of the ischium upon the top of the bucket, directly to the ground.

The erect position is thus very secure, and stability in walking is also very good throughout the time when the artificial limb bears the weight.

To raise the limb from the ground and carry it forwards, the patient uses at the same time both flexion of the stump at the hip and movements of the pelvis (elevation, then rotation inwards) varying to some extent with his proficiency and with the length of the stump.

The old-fashioned peg leg, called the "poor man's peg," consists of a bucket continued into a rigid peg. If the support beneath the ischium is well made according to the principles described above, it is an excellent temporary limb.[3] This bucket of common wood, which is not specially shaped to the stump, is very economical; its imperfect fit is an advantage in that the stump, which is still enlarged, cannot bear friction; as the stump assumes its true shape and diminishes in size, the bucket is packed. We would add that every patient, who is not rich enough to possess two complete artificial limbs should have in reserve an emergency peg leg, for occasions when the artificial limb requires repair.

[3] A number of temporary limbs have been designed, with buckets of lattice work or of plaster. The old-fashioned wooden peg, which is easily obtained, avoids all this additional work without any disadvantage.

As a permanent apparatus, with accurately fitted bucket, the rigid peg leg has two defects: it has not the appearance of a leg and foot, and when the patient is sitting the rigid peg is unsightly and inconvenient to him and to his neighbours. We have therefore designed and completed a jointed peg leg, the principle of which is as follows:

Below the thigh piece the peg is attached by a transverse joint, this joint being locked in the extended position when the patient is upright. The patient sets it free by manipulating the lock through the trousers, when he sits down; when he gets up again the locking in the extended position is automatic.

The fitting of this transverse joint may be carried out in two ways.

1. The upper end of the peg ends in a stirrup-shaped fork and the bolt passes through the two ends of this fork and through the lower end of the thigh piece ([Figs. 31 to 33]).

2. The lower extremity of the thigh piece has cut in it a central mortise into which fits a vertical plate, prolonged upwards from the middle of the leg piece. The bolt passes through this artificial tibial spine and through the two sides of the mortise in the thigh piece. If the hole in the tibial spine through which this bolt passes is square the hinge works securely ([Figs. 34 to 36]).

In this form the axle turns with the leg, in the first form this is also possible. But most often when the forked attachment is used it is fixed to a leather thigh piece, and each end of the fork is jointed independently to the corresponding end of the lateral steels of the thigh piece, without any complete transverse bolt. It is then the fork that revolves around these two joints.

Figs. 31 to 33.—Fixation of the stirrup of the leg (Fig. 31) by a transverse bolt (Fig. 33), the aperture for which in the thigh piece is seen in Fig. 32. Double lock (Fig. 32).

Figs. 34 to 36.—Attachment by mortise and tenon, with a bolt, square in section, passing through the knee. Single lock on the outer side.

If there is a complete transverse bolt, the joint can be securely locked by a single lock at one of its extremities (at the outer extremity) (Figs. 36 to 39).

If there are two lateral joints the single lock is insufficient, both joints must be fixed at once; unless this is done, that which is not fixed has a certain amount of play and is strained.

It is, however, simple, by means of a posterior semicircle, to joint the two locks and to work them together by a single movement ([Fig 32]).

For æsthetic reasons the wooden leg piece may be made in the shape of a leg and foot. But if the principle of the peg leg has been adopted, for an agricultural labourer for example, on account of its stability, it is better to use an appliance in which a "show leg" is fitted around the simple peg on days when appearance is more important than work (Figs. 37 to 45). The limb is thus rendered lighter, for the false calf consists of a simple layer of felt and it is very easy to replace the enlarged lower end of the peg by a foot.

Figs. 37 to 40.—Attachment by a mortise, and show foot.

We show later two models of this sort, one with an American thigh piece of wood and a single lock upon a transverse axle, the other with a leather thigh piece and a double lock. The first (Figs. 37 to 40) is shown with an attachment by braces, and the second (Figs. 41 to 47) with an attachment by means of a waist belt; we have already explained when these two must be combined.

Figs. 41 to 47

Leather and steel peg leg, with show foot.

Figures 41 to 47 (leather appliance) should be compared with [figures 37 to 40] (wooden appliance) which complete them in certain points. It is unnecessary to refer further to the method of fitting the bucket to the suspension, or to the method of attaching and locking the knee.

The peg—attached above by a stirrup or by a mortise, it does not matter which—ends below in a rectangular tenon which fits into a corresponding excavation in the upper surface of the terminal piece, whether peg or foot (Figs. 38 and 44). A transverse bolt, square in section, with a head at one end and a thread at the other, fixes these two parts together. By taking out this bolt the peg can be replaced by the foot or vice versâ.

If the attachment of the foot is made in the heel, a fixed foot is used (Figs. 43 and 45), but it is easy, by making the attachment higher, to use a foot with movable ankle joint (Fig. 40).

The attachment of the show calf piece around the peg is shown in figures 43 and 45.

Most often the wooden thigh piece is to be preferred; the limb is lighter and may last four or five years instead of about two years.

We may add that leather loses its shape and the bucket becomes enlarged, producing inconveniences already described on [page 18].

But leather—indespensable for certain stumps which cannot stand a wooden bucket—has the advantage that it can be employed as a temporary fitting. During the first weeks, sometimes even for the first months, the shrinking of the stump can be accommodated by lacing up the bucket, and, when shrinkage is complete, the leg part of this first apparatus can be attached to a wooden bucket which the improved condition of the stump now renders possible.

This form is a little more expensive (80 frs.) than "the poor man's leg," but I believe a great deal more comfortable. It may be added, that it is easy when the foot is fitted at the end of the apparatus to render flexion of the knee free and to attain the "American walk," of which we shall speak later. All that is necessary is to attach in front an artificial muscle of indiarubber, reaching from the thigh to the leg and an extending sling like that in the American limbs (see [page 47]).

This appliance which we call the "Fédération Leg," because we designed it at the Fédération des Mutilés, has already been imitated without its origin being acknowledged.

IV. Walking with free flexion of the knee

A. Design.—The oldest type, which will suffice for studying the general conditions of stability, is that of Marks, with a fixed foot shaped out of the same piece of wood as the leg: the ankle joint—several types of which we shall describe later—does not affect the question of stability.

The appliance is made entirely of wood; it is strong and light.

Nothing need be added to the description already given of the fitting and method of attachment of the thigh piece, which ends below in a curved "condyle,"[4] which fits into the top of the leg piece. It is transfixed by a metal bolt, from each end of which a metal plate descends and is riveted into a corresponding groove in the leg.[5] This forms the axle which rotates in the thigh piece when the knee flexes or extends. Flexion of the knee is free. Extension is stopped just short of the straight line (see [p. 16]).

[4] The bucket and the condylar portion are made of two separate pieces of wood.

[5] The hole through which the bolt passes being cut in soft wood (willow or lime), must be strengthened by a cylinder of metal, of leather, or of harder wood (beech or service tree) in which the axle revolves.

Fig. 48.—Marks leg with fixed foot.

Fig. 49.—Construction of the foot.

The foot is in equinus at an angle of 25° to 30° so that the heel is 2 or 3 centimetres from the ground (the usual height of the heel of a boot). The piece of wood which forms the instep and which is continuous with the leg stops at a point corresponding to the middle of the metatarsus, and is only half the thickness of the foot. The rest of the foot is shaped of indiarubber stuck on to the instep piece; the wood and rubber being enclosed in a sheath of leather.

The foot should also point slightly outwards, as in the normal standing position.

To ascertain whether the limb is built so as to ensure equilibrium, a thread is stretched against its side so as to pass through the axes of the knee and ankle joints, if this cuts the ischial bearing point at its centre the equilibrium of the patient is assured. Equilibrium will be better still if the cord lies entirely behind the ischial bearing point, leaving in front of it the greater part of the thigh piece. The best method of ascertaining if the foot is properly mounted is to hold the limb in front of one by the thigh piece, with the knee bent at a right angle; it can then be seen whether the foot turns outwards at the correct angle.

It is not necessary to say anything more about the shape of the thigh piece ([page 17]).

The metal bolt which transfixes the knee must not allow any play; the hole through which it passes must be lined with hard wood or leather.

The indiarubber sole should be reinforced with several layers of canvas incorporated in the rubber, as the latter if not so reinforced perishes and cracks.

The appliance must further be examined after it is applied. The level of the iliac spines must be compared: the spine on the side of the amputation should be 2 cm. below that of the sound side.

Examine the position of the point of the foot. Make the patient sit down, see if the knees are on the same horizontal plane; if the sound knee is the higher the leg piece is too short. The foot being fixed in the equinus position the patient must wear boots while the examination is being carried out.

B. Mechanism of walking.—In walking, a step being taken with the artificial leg, the toe of the foot is the last to leave the ground, the heel being raised and the knee straight. The limb is swung forward and raised by flexion of the hip: active flexion of the knee is impossible, but passive flexion occurs, owing to the weight of the leg piece, as the thigh is raised.

At this moment the leg piece is vertical, forming an angle with the thigh, from this position it must pass into one in which it is oblique forwards and downwards, in a straight line with the thigh, so that the knee may be fully extended when weight is again borne by the limb as the foot meets the ground. If at this moment the knee is flexed the limb will double up under the weight of the body.

The first contact of the limb with the ground should be at the heel with, as we have already said, the knee extended. Afterwards as the limb, which at first points obliquely forward and downwards, passes into the vertical position in which it must be at the period when it bears the whole of the weight, this complete extension becomes locked and transforms the limb into a rigid column.

This is brought about as explained on [page 48] by mounting the foot in equinus, and we must here describe the methods by which the commencement of the movement of extension may be communicated to the leg so that the heel may be the first part of the foot to touch the ground.