Chapter X: Some General Principles in the Re-Education of the Disabled 145 (1)

INDEX 159

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.

FIG. 1.

FIG. 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 well-made 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_.

FIG. 5.

FIG. 6.

FIG. 7.

FIG. 8.

FIG. 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).

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.

FIG. 13.

FIG. 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).

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.

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).

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. 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.

FIG. 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. 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.

_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.

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.

_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.

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.

These methods may be termed _knee extending mechanisms_. They assist the passive action of the weight of the leg.

In fact the recurrence of extension is brought about by a pendulum movement of the leg, which, at first oblique downwards and backwards, swings into a downward and forward obliquity. But this movement is slow (the pendulum which marks one second is one metre long) and incomplete. The patient can make it complete with a little instruction, by extending the thigh slightly as soon as the foot touches the ground.

This may be sufficient if the stump is long; the leverage is good, and while the hip is being flexed a swing can be given to the thigh piece which accentuates the pendulum movement of the leg.

But with a short stump some special mechanism is essential to make sure that extension will be complete, otherwise the patient will be obliged to walk with short and calculated steps, to wait whilst the pendulum action produces extension of his knee and allows him to put weight upon his foot.

C. _Mechanism for starting extension of the knee during the time the leg is swinging._--There are two methods which are generally combined:

1. Elastic traction by an artificial muscle.

2. The extending sling.

1. _Artificial muscle._--The action of an artificial muscle made of elastic (noiseless) or of a coiled steel spring, is easily understood.

(a) The simplest method (that which is commonly used for infantile paralysis affecting the quadriceps) consists in fixing an elastic band divided into two slips, one on either side of the patella between the front of the thigh and of the leg, about the middle of each. (This is represented in figure 98 in our convertable leg.)

(b) When the apparatus includes the regular artificial knee the makers generally place this mechanism in the interior of the thigh and leg pieces, using methods which are often very ingenious. Of these we illustrate some on pages 40 onwards, with an explanatory description.

In describing these mechanisms, which may be called intra-condylar, it is necessary to speak at the same time of the _stop to limit extension_ because, as will be seen, it is combined with the extending spring.

We have already said that rigidity in extension when the limb is vertical is essential, but whilst it is necessary for extension to be _complete_ at this moment it is also necessary to prevent the knee being forced into the _hyperextended position_, as this would quickly strain the joint and render the limb useless.

This limitation of extension can be effected quite easily by the tension of a popliteal cord (see page 41. The knee in Marks leg), or by carrying the anterior border of the leg piece upwards in front of the thigh piece so that it impinges against the latter.

This method is not very good because it is noisy.

Moreover, the repeated impact against the leg piece may split the wood, so that if this method is adopted the stop must be reinforced by a binding of several layers of parchment.

We will first describe a mechanism the association of which with the extending sling will be seen on page 48.

α. _To limit extension of the knee_ all that is necessary is to prolong the antero-posterior diameter of the knee bolt (which turns with the leg) by a horizontal wing, which engages with a corresponding notch in the femoral condyle. We show here (Figs. 50 and 51) a rather more complicated but still simple mechanism which is interesting because it can be combined with the action of the extending sling (see page 48).

It consists of a piece of metal curved on the flat, ending above in a cylinder through which the knee bolt passes, continued below into a cylindrical tail piece, which fits into a ring which is fixed inside the top of the calf. During flexion this plate moves in a median posterior window in the femoral condyle, becoming oblique at the same time as the tail piece sinks into the ring; during extension the tail piece rises in the ring and the interior flat surface engages against a corresponding groove in the femoral condyle (covered with leather to secure silence).

β. In the Marks knee an internal system of cords and springs serves at the same time both to limit extension and to produce an elastic extending force. It is a system which is fairly simple and much used.

1. _Limitation of extension_ is secured by a U-shaped cord, the extremities of which are fixed to a wooden cross piece (T), fixed in the thigh piece three centimetres above the axis of the joint. The cords leave the thigh through two lateral openings in the back of the thigh piece, and the loop passes through a ring halfway down the calf.

2. _The extending force_ consists in a coiled steel spring the mechanism of which is combined with that of this cord. The lower half of the spring is enclosed in a copper tube lined with chamois leather to secure silence; its upper half or rather more is coiled around a wooden pin, which terminates above in a head which is cup shaped: it will be seen (Fig. 57) that if pressure is made on this head the spring is shortened and under compression.

This spring is fixed below (by means of a tenon which allows antero-posterior movement) upon a bracket in the calf which is continuous with the ring through which passes the check cord. The cup-shaped upper end is in contact with a ball which projects from the upper surface of the thigh piece between the two openings for the check cord (Fig. 53). It will be seen that when the knee is flexed the spring, the head of which lies below the axis of the joint, will be compressed at the same time as the check cord is relaxed so that there is an elastic recoil tending to reproduce extension. The ball which rests on the top of the spring is fixed in such a manner as to be in the same horizontal plane as the axis of the knee: that is to say, it is in the same vertical plane as this axis when the knee is flexed to a right angle (Fig. 52). Therefore in this position the spring has no tendency to produce either extension or flexion, that is to say the mechanism is now at dead point, and when the patient is sitting flexion to the right angle is maintained without any effort.

FIG. 52.

FIG. 53.

FIGS. 54 to 57.

FIGS. 52 and 53.--O, knee bolt. T, cross piece of wood,
situated in the extended position above the knee bolt, in the flexed
position behind it. C, bracket fixed halfway up the interior of the
calf.