Chapter X: Some General Principles in the Re-Education of the Disabled 145 (3)

1. _The Concavity of the Armlet._--At the elbow joint the pinching of the anterior soft parts on flexion is liable to take place in just the same way as occurs at the back of the knee in amputations through the leg. To avoid this it is necessary--

(1) That the axis of the joint should lie in a prolongation of a line passing through the epicondyle and the epitrochlea.

(2) That the armlet and the forearm socket should be cut away in front in crescent-shaped concavities.

The depth of these concavities is estimated when the limb is fitted. Both the arm and the forearm may be cut away freely without any resulting inconvenience, provided that the stump is long; but if the stump is short and includes only the upper third of the forearm, it is impossible to cut away the forearm socket sufficiently without depriving the stump of a proper hold in the socket, so that movements are not transmitted to the forearm lever with their proper force. Consequently the socket for the forearm must be cut away very little, and must be carried up to the level of the fold of the elbow when the joint is flexed. The flesh in front of the elbow will not be pinched if, the forearm being fitted very accurately, the muscles of the upper arm are allowed free play, by cutting away the front of the armlet to half its height, but in this case an indirect attachment to the shoulder is essential.[12]

[12] Another difficulty in fitting a short forearm stump arises from the fact that the antero-posterior diameter of the forearm immediately below the elbow increases considerably when the joint is flexed, because of the contraction of the muscles arising from the condyles. If the forearm socket is made to fit closely when the elbow is extended it will be too small when the joint is flexed and will prevent full flexion. If it was made to fit with the elbow flexed, there is risk of the stump slipping out of the socket when the joint is extended. (Ed.)

FIG. 132.--Bad apparatus for amputation in the upper third of
the forearm. The front of the arm piece is insufficiently cut away.]

FIG. 133.--Good apparatus. The arm piece is well cut away,
consequently the flesh does not bulge out.]

2. _Construction of the Joint._--In most cases this is a simple articulation between the steels of the arm and the forearm pieces by two hinge joints.

FIG. 135.

FIG. 134.--Limb for amputation through the lower third of the
forearm, with elbow joint of strong leather.

FIG. 135.--Details of the joint.]

The objection to this is that the movements of pronation and supination, if these are present in the stump, are abolished.

(_a_) _Long Stump._--When the stump is long (amputation in the lower quarter) the following may be used: The steels of the forearm socket are attached to the armlet, which is not furnished with steels, by two straight strips of hard leather jointed at each end with rivets to the corresponding piece of the limb. This allows a certain amount of torsion so that pronation and supination are to some extent possible. It is necessary to add an indirect attachment to the shoulder. Not only must the armlet, not being closely moulded over the condyles, be even when new laced so tightly as to be unbearable, but in addition the inevitable loss of shape of the unsupported leather will in every case soon interfere with proper support direct from the armlet (Figs. 134 and 135).

This method is, moreover, scarcely applicable to patients who will have to carry out heavy work.

(_b_) _Short Stump._--The stump of an amputation in the upper third of the forearm is too short to be securely held in the forearm bucket. There is consequently a loss of power in the movements communicated, particularly in flexion, the arm of the lever being too short; in addition, the elbow joint in these cases is often a little stiff, so that flexion beyond a right angle is impossible (Figs. 136 to 138).

The chief functional difficulty depends upon the fact that, with the elbow at a right angle, the anterior surface of the forearm stump is too short to support a weight; for example, a basket held by the handle. The stump escapes partly from the bucket when the forearm extends. It is therefore well in such cases to fix the elbow at a right angle by means of a ratchet identical with that used in the artificial arm for amputation above the elbow (Fig. 138).

3. THE ARTIFICIAL HAND AND APPLIANCES

At the extremity of their forearm almost all patients wish in the first place to wear something that is shaped like a hand. Many people--and even many medical men--consider that this "artificial hand" is really useful. In actual fact, by means of fairly simple contrivances, it can be used to enable the patient to eat, to write, to put on and take off his hat, but it is out of the question for it to do real work. For that an appliance, a tool in fact, adapted for use and not for appearance is necessary.

The limb, therefore, will, as a rule, end in a hand, but for workmen this hand will be capable of being unscrewed and replaced easily by one or more appliances.

Attempts have been made to construct so called universal hands and forceps which will serve for any sort of work, but up to the present none of these inventions have given satisfaction. And the practical solution of the problem in the present state of affairs consists in devising a special appliance for a particular trade, studying carefully the movements necessary in this trade.

A workman who in the course of his occupation carries out a number of different movements may thus have several appliances, which he selects as he requires them. For example, a locksmith must be able to hammer, to file, and to drill holes in succession.

We will describe first the hand properly so called, then the appliances. The former is suitable for clerks, and it is for them that the various improved patterns that we shall describe are made. The latter are suitable for manual workers to whom should be given a hand in which the mechanism is reduced to a spring thumb grip and one or more special appliances.

These appliances will almost always be constructed to carry out the movements made by the left hand in the course of the work, because the first step in the re-education of a patient who has lost the right hand should always consist in training the remaining left hand to carry out the work hitherto entrusted to the missing right hand.

A.--THE ARTIFICIAL HAND.

The hand, which is screwed into the end of the forearm socket in such a way that it is in semipronation when the arm hangs vertical, is nearly always made of wood, but occasionally of aluminium.[13]

[13] Hands are nearly always made of lime wood, which has the advantage of lightness, but the fingers are fragile and easily break. Instead of using hornbeam, which is hard but heavy, as the fragility only affects the fingers, some makers have overcome this difficulty by reinforcing the fingers by what they call a "philippeau."

The finger is divided throughout its whole length by a mortise 1·5 millimetres in width, in which are glued two layers of veneering wood (mahogany, rosewood, etc., extremely hard woods, or else a layer of hornbeam).

It may be a simple show hand without any joint. This pattern is no longer used. It may be jointed in one or in several fingers. We shall first consider certain principles of construction which we can explain by describing the chief mechanisms used.

_Simple Spring Grip Thumb._--The simplest and most useful articulation is that of the thumb, which when at rest is kept by means of a spring in the flexed position, with the grip against the index finger which is partly flexed (as are also the other fingers).

In many cases the patient is content with this simple mechanism. He opens the spring with the other hand and allows it to close on the object he wishes to grip (Figs. 139-145).

The thumb turns on the axle D upon a piece which fits by a tapered
extremity C into a hollow cut out in the thenar eminence. The base of
the thumb is rounded. The spring AB flexes the thumb.]

The model shown on page 98 is more mobile than this, in which the
thumb turns on the axis AB, and is fitted directly into the thenar
eminence. But in this type it will be seen that the spring CD which
keeps the thumb flexed, reaches right up to the wrist, and is
therefore longer and more powerful. The thumb is much stronger, and
this is the mechanism usually adopted. It has the inconvenience that
it requires a deep excavation of the thenar eminence, encroaching
upon the root of the index finger, so that it is impossible to
mount the thumb in this way when it is desired to fit a movable
metacarpo-phalangeal joint to the index finger, either with a spring
(Fig. 155) or without (Fig. 148).]

_The Automatic Thumb._--Active opening movement can be produced by the mechanism shown in figure 146. A cord fixed behind the scapula of the opposite side by a ring which passes over the clavicle and under the axilla, extends down the posterior surface of the arm and forearm pieces, running in pulleys which keep it in place. If the patient bends the elbow and at the same time brings the arm and both shoulders forward, rounding his back, the cord is tightened and pulls the thumb into the position of abduction and extension.

This narrow grip, between the tips of the thumb and index finger only, is not always convenient. A commercial traveller or a foreman could not easily hold with it the order book, in which he has to write. But if the thumb, held by a powerful spring, is parallel to the palm of the hand and grips against the other fingers, which are stretched out and not semiflexed, the grip will be strong and convenient, especially if a mechanism is introduced between the forearm and the hand, allowing the latter to be rotated at will into any position (Fig. 148).

As in the preceding case the thumb may have either a simple grip or an automatic grip opened voluntarily by a cord from the shoulder.

The following is a very interesting method which allows a fork or pen to be held, the automatic thumb being used. The fingers are half flexed, the index being separated from the middle finger, so that the handle of a pen can be inserted between them. The grip of the thumb is not against the tip of the index finger but against the outer side of the last phalanx of the middle finger, against which in consequence the handle of the object held will be pressed (Fig. 147).

FIG. 146--Appliance with automatic thumb. The cord is fixed
to a loop which passes round the sound shoulder. Abduction and forward
movement of the shoulder and flexion of the elbow open the thumb.]

FIG. 147.--Hand with space between the index and middle
fingers, wide enough to take the handle of a fork, which is held by
pressure of the thumb against the side of the middle finger.]

The extended fingers are better placed for gripping than the partially flexed fingers, although the latter are convenient to the patient in certain ways. Ball and socket joints are inserted at the interphalangeal joints. (Details are shown in figures 152 to 154.) These are so stiff that they maintain the position in which they are placed passively, as do the joints of an artist's lay figure.

FIG. 149.--The usual pattern of hand. The grip is too small.]

FIG. 151.--The middle finger being longer than the index, the
latter does not reach the surface of the table and the ball cannot be
picked up.]

If the fingers are rigid and in semiflexion it is possible to articulate all the metacarpo-phalangeal joints, fitting them with a spring, which keeps them flexed, and arranging for active extension as already described for the thumb. All that is necessary is to terminate the cord by five separate strings instead of one. In certain special cases this arrangement may be useful (Figs. 155 to 157). It seems to us useless to render the interphalangeal joints automatic.

As to the attempt which Beaufort appears to have made to give movement to the wrist also, we do not believe that any practical result has as yet been attained.

For the relative length of the fingers and the utility of a nail on the thumb and on the index finger see figures 150 and 151.

_Shape of the Hand._

In the usual pattern (Figs. 149 and 151) the fingers are semiflexed and the thumb grips against the index finger, which is shorter than the middle finger as in the natural hand. If it is desired to pick up a ball, for example (Fig. 151), it will be seen that the middle finger projects and gets in the way. For this reason it is advisable that the index finger be longer than the middle, and in addition it is useful to furnish the thumb and index finger with a little projection representing the nail (Fig. 150).

In figure 148 will be seen an arrangement which allows the thumb to grip not by the tip, but by the whole length of its palmar surface (to hold, for example, a notebook). The fingers of this hand have ball and socket joints constructed in the way shown in figures 152 to 154. The joints keep passively the position in which they are placed. The attachment of the ball of the joint on an intermediate tenon is similar to that of the thumb shown on page 98. The articulation of the index finger prevents the sufficient excavation of the thenar eminence for the insertion of the Beaufort thumb with its powerful spring. The wrist rotates upon a bayonet joint.

The fingers shown in figures 155 to 157 are joined together into a single piece, which articulates with the metacarpal part of the hand upon a transverse axis.

They are held in a position of flexion at the metacarpo-phalangeal joints by four palmar springs and they are opened away from the thumb by the action of a cord which bifurcates from the thumb cord on the back of the hand. The pull of this cord is exerted upon the upper angle of a triangle from the lower border of which four cords pass on to the back of the phalanges. Figure 156 shows detail of a finger. We know that attempts have been made to isolate by surgical means the masses of the extensor and flexor muscles in the end of the stump, making from them little prominences, perforated with a tunnel which is lined with skin. The cords pass through the tunnels, and in this way are worked voluntarily. We are not sure that this is practicable.

In figure 155 are seen the cavity in which the finger portion works
and the axis upon which movement takes place, also the four palmar
springs. In figure 157 the arrangement of the cords. In figure 158 the
attachment of the spring to the finger. This pattern, which we have
designed and which is not patented, seems to us to be simpler than
those in which the interphalangeal joints are also articulated and are
automatic. It gives a more accurate grip between the tips of the thumb
and index finger.]

_The Brunet Grip._--The Brunet grip is described here because of its resemblance to the automatic thumb, both being worked on the same principles.

Below the leather forearm piece, which laces up, the lateral steels
are continuous with each other in the form of an arch, to which the
grip is riveted.

The latter consists of a strong semicircular piece of metal facing
downwards, ending in a pair of wide and thick jaws, like those of a
locksmith's pliers. When the apparatus is at rest, these are kept in
contact by the pressure of two powerful fixed springs, attached to the
semicircle on the forearm above and to the jaws below. The external
and dorsal spring is attached to the tip of its jaw, the internal and
palmar (the side on which the manipulating cord is attached) to the
base of it.

The pliers are opened in the following way:--

Inside the semicircle to which the jaws are attached, lies a cylinder
with its ends cut obliquely; this rotates about a transverse axis,
and when at rest lies with its longer side upward. To the palmar edge
of the shorter side is attached a transverse eccentric, to which is
hooked a cord actuated as described in figure 146. When this is drawn
upward the cylinder rotates so that the wider side comes between
the jaws of the pliers and opens them; when the cord is relaxed the
springs turn the cylinder back again find the jaws close. Figures 158
and 159 show the appliance at rest and with the jaws open.

This appliance is patented and is made in one piece. We demonstrate in
figure 160 that it would be very easy to make the pliers detachable
from the forearm, with a screw connection, just as is done in the
various other appliances which will be described.]

The grip of the automatic thumb always lacks power, for two reasons. There is no room in the thenar eminence to fit a powerful spring and the grip has always a very narrow hold.

The Brunet grip is an actual pair of pliers, shaped like these and furnished with a powerful spring. It is opened by a cord like that of the automatic thumb. Figures 158 to 160 explain the mechanism. It is an excellent appliance with which the wearer can carry out the majority of the actions of everyday life. It has, however, the disadvantage that it is not shaped like a hand--a point to which patients attach much importance--and, moreover, it is a part of a patented appliance, for which an interchangeable hand is not manufactured. So that in order to have in addition an artificial hand, which is capable of being removed and replaced by one or more of the appliances which will be described later, it would be necessary for the patient to possess two complete artificial limbs, and changing from one to the other would evidently be inconvenient.

We generally prescribe this appliance for patients who have lost both arms, for one side and as a supplementary appliance.

There are other similar models into details of which it is unnecessary to enter. Those in which the grip is opened by movements of pronation and supination are obviously only suitable for certain rare cases (very long stumps, with free movement).

B.--APPLIANCES FOR USE IN PLACE OF THE HAND.

The general principle is to fit to the end of the forearm piece an attachment which can be screwed on or unscrewed at will and which carries an appliance which is adapted to the various more or less specialised movements of the patient's trade.

Naturally the results thus attained must always be imperfect; but however little perseverance and ingenuity he may possess, the patient finds that he is able to educate the remaining arm, even when it is the left, to replace the amputated one in a way that is often remarkable. It is to this education that attention must be specially directed in the workshops for the re-education of the maimed.

1. _Knife and Fork._--The first necessity is to be able to eat, and by certain very simple devices a fork, spoon or knife may be fixed to a wooden hand, whether the thumb be mobile or not.

As a general rule if the patient has one arm intact, he uses the sound hand only for this purpose, but when both forearms have been lost an appliance is indispensable.

We have already described how in the hand with an automatic thumb, room can be left between the index and middle fingers for the handle of a spoon or fork. A direct grip can also be obtained with the hand shown in figure 147.

The hand with five automatic digits (p. 105) is usually arranged in such a way that it is possible to hold a tumbler for drinking; but a patient with an amputation of one hand drinks with the other, and one who has lost both hands can drink with a straw.

These appliances have replaced that in which the knife or fork is attached to a block of wood which can be fitted into the palm of the hand when required. It is inconvenient to be obliged to carry these special implements about.

Raynal's fork-rest has the advantage over the last mentioned that it fits any fork. Figure 161 shows very clearly its construction and the way in which it is used. The small special attachment, which is screwed in place, is not cumbersome and can quite well be carried in the pocket; it is, however, even more convenient to have an appliance which is capable of gripping the fork directly like those described previously.

2. _Appliances for Workmen._--All the appliances that are attached to the arms in place of the artificial hand for performing various kinds of work are elaborated from two simple forms: the hook and the ring (for catching hold and carrying a parcel, for holding a handle, etc.). A glance at figure 162 will show the nature of these and the way in which they are used. But it will also be understood that if the simple ring and hook are useful for equally simple purposes they are altogether insufficient for skilled labourers whose work entails a certain special adroitness, e.g. joiners, locksmiths, agricultural labourers, etc.

Many makers have realised this and have devised very ingenious implements, some of which we reproduce, though we are obliged to limit ourselves to certain types, for they can be varied in countless ways according to the needs of particular cases. The same workman, as we have already said, may have several appliances which he uses in turn as he needs them in the course of his work.

These appliances are constructed in two ways; some are fixed to the end of the forearm and are immobile, some are attached by means of a joint or joints and are capable of rotation in various directions.

(_a_) _Fixed Appliances._--We illustrate here an appliance derived from the simple hook, the _vine-dresser's claw_, devised some time ago by Gripouilleau; branches of varying size can be held while the other hand saws them or cuts them with the pruning shears (Figs. 163 and 164).

This appliance of Gripouilleau, with a series of hooks, forms the basis of almost all the "pincer hands" constructed by M. Boureau and characterised by--

(1) The closure of the upper hook which is thus transformed into a ring, the two appliances being combined in one;

(2) The spring fixed to the straight side of the hook providing the grip necessary for holding articles. If the free end of the spring is turned up like the pointed toe of a mediæval shoe a sufficiently large opening is left between it and the straight edge of the hook to enable an object which is fixed mechanically or held by the other hand to be pushed into and gripped by the spring.

The simplest type of this mechanism is the _postman's hand_ (Figs. 165 and 166).

The left hand of the postman who sorts letters has for its work to keep in the proper order the envelopes which are arranged in little packets; the right hand has only to push the letter into place between a flat spring, fixed to the wrist, and the back of the hook. If two or three springs are supplied the postman can arrange two or three packets of letters at the same time. He can also bind the packet with string.

The _vine-dresser's hand_ is provided with this spring to hold small flat objects, but the second spring is wavy in outline, so that semilunar spaces are left between it and the first. Into these branches slip when the spring is pressed against them, and they are thus held more firmly, whilst being sawn or pruned, than by the twisting action of the old pattern hook of Gripouilleau (Figs. 167 and 168).

This thrust to seize the branch is somewhat rough, and is only possible in holding hard wood which there is no fear of bruising. For more delicate shoots (grafting vines indoors, preparation of cuttings), a grip is necessary which can be opened before seizing hold of the object. This is accomplished by prolonging the spring towards the forearm as a handle, pressure upon which against the chest (when standing), or against the knee (when sitting), opens the grip, in which the graft, for example, is then placed in the opening of the correct size.

_The packer's hand_ is very ingenious (Fig. 169). It has the hook pierced by an eye enabling a thread to be passed through a basket as with a curved needle. The jaws of the pincers are smooth at the tips, but further back they have a series of graduated notches in which tacks of different sizes can be held whilst they are driven in with the hammer. But of course a workman can only work quickly if he can hold a number of tacks of the same size in the palm of his hand, placing one under the hammer, relaxing his hold of it after the first gentle blow has fixed it, and getting the next ready while he drives it home.

_The plumber's hand_ (Fig. 170) is made in the shape of a pair of gas pliers, and ends in cutting edges with which wires can be cut. With them a bolt can be held whilst the other hand screws on the nut.

_The leather-cutter's hand_ (Figs. 171 and 172) should be able to hold the skin which the other hand cuts: it consists of a plate with a rough surface fixed to a ball and socket joint which allows it to turn in any direction, so that the other hand can follow the line to be cut which is often sinuous. This appliance may also be used to hold a drawing paper, a rule for cutting cardboard, or sheets of paper for binding.

The examples that we have chosen amongst Boureau's appliances for craftsmen will, we believe, be sufficient to explain the principles of their construction. These consist in studying the movements which are normally carried out by the passive hand (usually the left hand, but the right in left-handed people) and to devise an appliance accordingly, the sound hand always becoming the active hand.

We could have described many more examples, but we shall only say a few words about the _mechanic's hand_, which is simply an adjustable spanner which can be automatically closed, terminating in toothed pliers to hold circular objects without the necessity for being screwed up. As a matter of fact, in all the work of a mechanic (sawing, filing, drilling, tightening screws, hammering, forging, and grinding) the left hand is only used for picking up and steadying the article to be manipulated. M. Boureau rightly considers that it is better to entrust this rôle to the artificial hand rather than to contrive to make the latter capable of sawing or of filing by means of the devices which we shall describe further on (p. 121 and following), ingenious and interesting though these may be.

From these appliances, adapted to certain particular grips, others have been devised for chair caning, soldering, and for enabling factory hands to work starting levers and brakes.

Thus each case must be studied separately and the workman furnished with one or several appliances according to his needs, making the necessary modifications from the existing patterns.

Several of these appliances are attached by a ball-and-socket joint like that described for the leather cutter: this is an intermediate form between the fixed appliance and the jointed appliances which will be described later.

Boureau recommends that the length of the forearm should be such that the artificial appliance reaches only as far as the level of the sound wrist. The work will then gain in precision. We believe that this principle holds good even for the true artificial hand, which should be made 3 to 4 centimetres shorter than the sound hand. But it must be realised that we shall be met with a difficulty, which we have already experienced. Comments are made upon the appearance of the arm and the wearer may sometimes be made to believe that this is due to faulty construction.

For certain special crafts the subject may be studied from another standpoint and an actual tool constructed which carries out the necessary actions like a machine worked by the forearm, so that in these special cases the artificial hand is the active hand.

At the Valentin Hauy Institute for the blind, where there has long been a brushmaking workshop, we have seen in use a very ingenious tool of this description with a combined action for carrying out the entire manipulation of the thread which fixed the little bundles of bristles into the holes perforating the back of the brush. Results are so good that a blind and maimed worker using this apparatus works more quickly than his comrades who have the use of both hands. It consists of a two-pronged claw surmounted by a small thimble-shaped projection and with a small hook, like a crochet hook projecting in front (Fig. 173). The hook first passes through one of the holes in the back of the brush, catches up the thread and draws it through the hole (Figs. 174 and 175). The thread is then looped around the thimble, whilst the sound hand binds the little bundle of bristles into a twist of the loop (Fig. 176), and finally the bundle is fixed into the hole, the claw being used to draw the brush towards the worker (Fig. 177).

(3) In place of an actual tool the detachable part may consist of a clamp on the principle of a ring into which the tool is inserted by the handle. The two principal methods are the screw and the American chuck. A glance at figures 178 and 179 will explain how the large handle of a tool intended for heavy work is controlled by means of a screw and rings.

At Rouen we have seen the disabled Belgians who had been re-educated wearing an ingenious T-shaped clamp by means of which the handle of a tool may be held either in the line of the axis of the forearm or at right angles to this. This method is specially useful for manipulating a file which is worked with one hand while the other, in this case the sound hand, presses upon the free end. Usually the filing is done backwards and forwards, working from base to tip of the file, but sometimes, specially for final polishing, the file is held with both hands and worked from side to side.

The American chuck consists of a pair of metal jaws fixed at their base into a cylinder and appearing somewhat like the petals of a long corolla. Another cylinder is screwed over the first to control the opening and shutting of the jaws. When this cylinder is unscrewed the jaws open and the handle of the tool can be inserted, when it is screwed up it closes the jaws and makes them grip the handle.

The pincers are composed of two jaws with vertical cylindrical grooves
(to fit upon a handle), joined above by a ring (Fig. 185) and coupled
by a spring C which keeps them apart. The pincers fit into a piece
B (Fig. 182) cut on the outer side with a screw thread (Figs. 182
and 183) upon which the piece A is screwed up or down (Figs. 180 and
181). When screwed towards the point of the pincers it presses on the
two jaws and closes them. When screwed in the opposite direction the
pincers open automatically.]

If the jaws open widely, the wooden handle of a tool can be held, but if the opening is small the unmounted tool must be fitted into them (Figs. 186 and 187). This method is specially useful for files, as it frequently happens that several files are required for the same piece of work and they can be changed rapidly.

It must, however, be insisted upon that the principle of giving a passive rôle to the artificial hand is to be preferred.

(_b_) _Appliances with Mobile Joints._--In the course of work the direction of the wrist is changing at every instant, flexion, extension, pronation, and supination occurring, sometimes in order to move around the object, sometimes in order to maintain a suitable position when the movements of the shoulder and elbow vary the direction of the forearm.

The consequence of this is that the worker learns to turn the piece of work around with his sound hand. To get over this difficulty passive joints are inserted at the wrist, which allow the appliance to move when it is pressed against the piece of work and to take up the direction which suits the inclination of the forearm.

FIGS. 192 to 194. 1. Tram driver's and chauffeur's bell. 2.
Method of use by a tram driver. 3. Management of a motor car lever.
Pressure at the extremity and traction.]

One of the simplest mechanisms--and one of the oldest, because it was designed by Gripouilleau--is that of the _agricultural labourer's ring_, intended to grip and manipulate the handle of a wheelbarrow or a plough. The ring is mounted on a transverse axis and moves in a horseshoe which in its turn revolves on a shank which is screwed into the forearm. The ring is provided with a screw, which may be tightened upon the handle if desired, but which is, however, rarely used (Figs. 188 to 190).

The _tram-driver's bell_, represented in figure 192, is devised on the same principle. It moves on a transverse axis, and in figures 193 and 194 its utility in managing levers in driving a tram or a motor car will be easily seen. The rotation of the horseshoe on the axis of the forearm is not required.

_The "cardan" joint_ also allows movement in every direction: it consists of two semicircles of metal, placed at right angles, each working around a transverse axis, these axes being united in the form of a cross. The construction and working will probably be understood without further explanation by a study of figures 195 to 198. The first two represent a system with a ball in the centre, which is well known commercially. The last two represent the simple universal joint generally used in orthopædic surgery. It is somewhat more cumbersome than the previous model.

The spade holder used at the agricultural centre at Limonest is mounted on a cardan (Fig. 199).

The joint can be fixed by a compression screw which is easily and quickly adjusted.

Where several tools are necessary each should be complete with its own universal joint.

Other methods of terminal passive articulations are--

(1) Ball joints which have already been described in connection with the fingers and which may be applied to the wrist.

(2) Bayonet joints which are only applicable to certain artificial hands which are not subjected to any great strain.

Figure 200 explains this mechanism as it is applied to the artificial hand represented in figure 148.

_CHAPTER VIII_

ARTIFICIAL LIMBS FOR AMPUTATION THROUGH THE ARM

In this chapter we shall deal only with amputation of the arm below the upper third, _i.e._ with cases in which the stump is long enough to transmit movements to the artificial limb. Amputation through the deltoid muscle must be considered in association with disarticulation of the shoulder.

Below the arm socket is attached an artificial limb which represents the elbow joint, forearm, and hand.

There are two types to be described:--

1. The artificial arm proper, which has the external shape of the natural limb.

2. The worker's arm, a terminal appliance in which outward appearance is not considered.

The considerations as to the arm socket and its attachment by a shoulder cap are the same for the two types of appliance.

_Attachment and Arm Socket._--The surface over the acromion and clavicle is the only point from which support can be given to an appliance for an amputation through the arm; the attachment is made by means of a shoulder cap.

The general shape of this shoulder cap and its attachment by means of a strap passed under the opposite axilla are similar to those described for appliances for amputation through the forearm.

The larger the shoulder cap the more it extends forwards over the anterior wall of the axilla, upwards over the supra clavicular fossa, and backwards over the scapula, the more secure will be the support. The appliance is heavy and has no support other than the axillary strap. The latter has a tendency to ride upwards against the axilla where it exerts a pressure which may be uncomfortable. This may be relieved by attaching a vertical strap which is buttoned to the trouser belt.

But although this extensive enclosure of the thoracic region may not hinder the movements of the stump forwards and backwards, it must obviously interfere with the movement of abduction. No doubt this movement is the less important of the two, but we ought to try to preserve it as far as possible.

In short stumps we must abandon it. But if the stump is long and consequently has no tendency to escape from the socket, even if this slips down a little, movement may be retained by two methods.

The first consists in separating the arm socket from a large shoulder cap, and inserting a joint between (see page 87); but the appliance is then heavy and cumbersome. Moreover, although abduction can thus be easily attained, thrusting and pulling movements require a light appliance, and finally it is impossible to secure rotation.

It is possible, on the other hand, by means of the other method, which consists in ending the shoulder cap at a line continued vertically upwards from the thoracic margin of the axilla. If the straps are strong and carefully adjusted the result is better than with the fitting over the scapula, so that this appliance is preferable. We here illustrate a method of fitting the straps which we consider a good one. From the posterior part of the ordinary axillary strap, a Y-shaped branch passes to the upper border of the shoulder cap above and in front of the clavicle, this makes up for the small extent of the enclosure of the shoulder.

For the worker's arm a considerable enclosure without any joint is essential, in order to secure stability.

The arm bucket, usually continuous with the shoulder cap, is made of leather strengthened with steels.

The artificial arm is often abducted from the trunk, which constitutes an inconvenience. This is sometimes due to a fault in the alignment, the arm piece not being at right angles to the shoulder cap. It is, however, more often due to the cylindrical shape given to the arm bucket which forces it away from the trunk. The inner side of the bucket should be flattened so that it may hang vertically close to the thorax.

The details of construction are different for the true artificial arm and the worker's arm.

1. ARTIFICIAL ARM

The arm and forearm pieces are both made of leather. There is no object in making them to lace, the stump is enclosed in a socket in which it need not fit very tightly, because, as we shall explain, this appliance is unsuitable for heavy work.

These two parts are strengthened with steels, which are articulated by hinge joints at the level of the elbow. We have to study--

1. The position of the steels and the direction of the axis of the joint.

2. The lock to fix the elbow joint in a flexed position.

1. _Position of the Steels._--The stump can transmit to the arm socket the various movements grouped under the name of circumduction, but its hold does not enable it to transmit rotation.

It is therefore undesirable--although usual--to attach the steels on the arm and forearm to the inner and outer sides of the limb. If this is done, as rotation is impossible, flexion of the forearm at the elbow can only be carried out in the sagittal plane. But this movement is only exceptionally required; the elbow being flexed to the right angle and fixed in this position by a ratchet the limb forms a hook upon which an object may be hung, provided that the forearm lies transversely in contact with the abdomen and not antero-posteriorly. Flexion should therefore be in a plane which is almost the frontal plane (20° or 30° in front of this), and not in the sagittal plane. As there is no active rotation of the arm therefore the steels must be almost in the sagittal plane (the anterior a little external, the posterior a little internal).

In certain carefully constructed appliances the arm bucket is cut transversely above the elbow and between the two parts a bayonet joint is fixed where the arm can be rotated by the sound hand, so that the direction of the elbow movement can be altered.

2. _Ratchet to fix the Elbow Joint in the Flexed Position._--When at rest the forearm should hang vertically. But the hand can only be used when the elbow is flexed to an obtuse angle or a right angle, the latter position being more often used. Therefore when the patient has bent the joint to the required angle with his sound hand, he must be able to fix it in this position.

This fixation is effected by means of a ratchet attached to the outer side of the elbow, which can be locked or unlocked at will.

This ratchet consists of a flat metal plate with a prolongation upwards shaped like the handle of a fork. The end of this prolongation is attached to the arm steel by a pin joint about 3 centimetres above the axis of the elbow joint. The plate is pierced by a rectangular opening, one border of which is notched; it lies against the forearm steel, a catch projecting from which fits into the opening, this catch, situated 6 centimetres below the axis of the elbow, is of the same diameter as the notches with which it engages. The higher the notch with which engagement takes place the more nearly flexion approaches the right angle.

The width of the opening in the plate is twice the size of the catch, so that the joint works freely when the catch glides on the smooth edge and becomes fixed as soon as the catch engages in the notched border.

It is only necessary to arrange a lock, manipulated through the sleeve, to bring the smooth or the notched border in contact with the catch.

Suppose that the handle of the ratchet is prolonged behind the point at which it is hinged to the arm steel as a little lever furnished with a button, and that an elastic cord or spring is stretched from this button to a point on the postero-external border of the forearm, then if the lever points upwards and the notches are on the upper edge of the ratchet (as is the case in figure 205), the elastic, pulling the lever forwards, will press the ratchet down and make the notches engage with the catch on the forearm, if, on the other hand, the lever points downwards the elastic traction will release the notches. The reverse occurs if the notches are on the lower edge.

It is then only necessary to arrange a mechanism by means of which this little lever can turn, with a stop which arrests it above at the vertical position, below at a point 45° beyond the horizontal.

A simple mechanism of this sort is shown in figures 206 and 207. The joint surfaces of the ratchet and of the little lever each bear a shoulder, the former in front, the latter behind, extending over such a proportion of their circumference as will make them act as stops in the desired positions above and below.

A lock is thus provided which can be manipulated with the other hand.

In the particular pattern illustrated, traction is made by an elastic cord fixed to the centre of the back of the wrist and ending above in a leather strap pierced with holes which fix on the button of the lever. This arrangement allows of the adjustment necessitated by the gradual stretching of an elastic which is subjected to continuous tension.

A steel spring of this length (the whole length of the forearm) would be too heavy if it were sufficiently powerful. If it is desired to use this method the two ends of a powerful spring should be fixed, one to the button on the lever, the other to the catch on the forearm with which the ratchet engages.

The spring should always be in tension. As the distance between the joint on the arm and any point on the forearm increases as the elbow extends, it is better for the ratchet, with notches on its upper edge, to be engaged when the button points upwards and free when it points downwards. In the opposite arrangement, which is often used, the tension is considerable without being useful when the forearm is vertical, and the mechanism soon wears out.

3. _Hand and Other Appliances._--The hand attached to the end of the forearm has a spring thumb which may be passive or automatic. In the latter case, if the stump is long enough to allow considerable movements of the arm, the cord works in the way described on page 87, for amputation of the forearm. If the stump is short, traction must be exerted by movement of the shoulders, rounding the back.

The hand with a mobile wrist is never used with these amputations except in certain expensive appliances, in which in addition the four fingers may be articulated, as described on page 101. For the ordinary limb these delicate mechanisms are devoid of practical utility.

It is easy to replace the hand with interchangeable appliances, but when the patient has to do hard work this is not a satisfactory method.

The arm with the ratchet at the elbow is in fact suitable for use by a clerk. But it is not either strong enough or simple enough for manual labour. In our opinion the functional and practical value of an artificial arm, particularly for amputation above the elbow, is often exaggerated, however it does exist, especially in many branches of agricultural work. For the latter the slightness of the lateral steels--and especially of the joints at the elbow--makes the appliance insufficiently strong. The necessary delicacy of the ratchet and its manipulation through the sleeve by the sound hand are additional disadvantages.

2. WORKER'S ARM

If our object is to fit to an arm stump an appliance which will be at the same time strong and flexible, capable of carrying out rough and even vigorous work, we must abandon the attempt to imitate the natural shape of the arm.

The movements and strength of the stump must be transmitted to the object held by means of a rigid rod at the extremity of which the appliance for gripping is fixed. It is possible to fix around this rod a show arm with a hand and a passive spring thumb for wearing on special occasions, in exactly the same way as we fit the show leg round the peg. Figures 208 and 210 will show at a glance how this is done.

But, as far as our present experience goes, this is only an accessory added for æsthetic reasons. The true worker's arm consists of a strong metal rod fixed to the arm socket in a way that we must now study.

1. _The Arm Socket._--We have already said that this must be continued into a shoulder cap of considerable extent, which may be perforated in the region of the point of the shoulder in order to render the appliance lighter. Abduction at the shoulder is thus sacrificed.

The arm socket is made of leather, open down the front and laced. By being laced it fits the stump more securely. It is strengthened by two steels which may be fixed in the frontal plane because, as we shall see, a passive rotation at the elbow joint is possible.

These steels are directly continuous below with a hemispherical steel cap, which is pierced in the axis of the limb by a hole into which is bolted the connecting piece to which the rod which represents the forearm is attached.

2. _Articulation at the Elbow._--The forearm consists of simple metal tube, attached beneath the arm socket by methods which depend upon the following principles.

The worker's arm consists of a metal rod which swings backwards and
forwards at the elbow and also rotates upon the arm socket. To the
end of this rod an appliance can be screwed (a ring and hook are here
shown). Around the worker's arm a show arm with a hand (Fig. 209) can
be fixed. They are shown in place in Figure 210.]

The only movements that the stump can transmit to the arm socket are forward and backward movements hinging about the shoulder, and abduction. The first of these movements is the only really useful one for the workman. The downward pressure exerted by active extension of the elbow no longer exists; in order to press upon an object the sound hand must be used, for it is not practicable to make use of the weight of the body thrown forward for this purpose.

In backward and forward movements--considering, for example, the use of the file--the angle at the elbow opens when the arm is thrust forward and closes when it is pulled backwards. These passive movements of the joint must not be impeded in any way, that is to say, the forearm must swing freely below the arm upon a transverse axis and it must also be able to rotate freely around a vertical axis.

These movements are secured in the ploughman's hand which was designed sixty years ago by Gripouilleau and in which the joint which we have shown as a method of attaching the mobile ring to the wrist is utilised. The forearm rod attached by a strong transverse pin swings freely in a little stirrup-shaped cap, which itself rotates around a bolt by which it is firmly fixed into the metal or wooden hemisphere which terminates the arm socket.[14]

[14] Wood, which was used by Gripouilleau, has been given up.

It is clear that this complete liberty of action has its disadvantages; the elbow joint can never be made to assume a fixed position against any passive resistance; moreover, in actual practice the useful range of either of these movements is small. For this reason attempts have been made to devise methods by which they can be limited in the various worker's arms which have been designed since the beginning of the war. In all these arms the mechanism of the elbow joint is derived from that of the ploughman's arm of Gripouilleau. Unfortunately none of these mechanisms in which a pressure screw is used for fixation possess any strength. At first sight, in a new appliance they appear attractive and work well, but it is well known to all mechanics that the thread of a screw which is in constant use quickly wears and then it is impossible to tighten it.

At the extremity of an artificial arm, whether it be an arm of natural shape or a worker's arm simplified to the form of a jointed rod, any of the appliances already described for forearm amputations can be screwed on as required.

It is by the use of these appliances that Gripouilleau's old ploughman's arm, which ended in an interchangeable hook and ring, has been improved.

Apart from their actual economic value, results have been obtained by use of these terminal appliances, in many different skilled trades, which are of the greatest possible interest.

For reasons that we have indicated in describing the attachment of the elbow, the various attempts that have been made to give to the wrist a mobility that is under control have not so far led to the invention of an appliance that is both strong and durable. For this reason we consider that until something new is designed it is better to make the terminal appliance a fixed one.

_CHAPTER IX_

ARTIFICIAL LIMBS FOR DISARTICULATION THROUGH THE SHOULDER JOINT AND
AMPUTATION THROUGH THE DELTOID MUSCLE

So far as function is concerned these operations are identical; a short arm stump is incapable of transmitting movements to the socket of the artificial limb.