Part 13

FIG. 84.

FIG. 85.

FIG. 86.]

This method of using rubber cylinders is the simplest. Another method, good but more delicate, is shown in figures 87 and 88. In the leg below the calf are two cross pieces of wood; the lower placed transversely supports the upper which is antero-posterior and so increases its resistance to the cords which are attached to it.

The shape of these pieces of wood can be seen in the figures and require no further explanation. The bolt of the ankle joint is the same as in the foot last described. To the antero-posterior cross piece are attached two cords, which pass through the foot and are attached beneath it, one under the heel, and the other about the level of the midtarsal joint. The posterior cord is inelastic and stops dorsiflexion of the foot. The anterior has a section of elastic in it; it prevents the dropping of the foot whilst the limb is being swung. A small pad of rubber placed in front beneath the anterior part of the leg piece allows, by its compression, the partial correction of the equinus when the sole is pressed flat on the ground.

Some appliances allow the foot a little lateral mobility, by rotation around an antero-posterior axis, so that it may adapt itself to irregularities of the ground. We here illustrate the "Duplex foot," which is very ingenious but which has the defect that after a time the mechanism grates. The ankle attachment is carried out in the same way as in the limbs last described (in this particular limb it is attached by cords), but the foot piece is divided as in a sub-astragaloid amputation; the lower surface of the astragaloid piece bears a median antero-posterior projection, tapering posteriorly and enlarged into a knob anteriorly, this lies in a corresponding groove in the heel piece; alongside this are two rubber cushions which are alternately compressed and relaxed as the foot inclines to one or other side.

Combined mechanism for knee and ankle joints.

This very ingenious combination, which, however, necessitates a rather complex mechanism, was devised by Palmer in 1850. It is carried out in the limb made by Frees, the mechanism of which will be seen to resemble that of the articulated foot shown on page 54 in figures 87 and 88.

Above the axis of the knee joint and at right angles to it is a wooden cross piece, to which are attached three cords, two behind the joint, one in front; these cords emerge from the thigh piece through an opening in its lower end (Figs. 90 to 92).

The posterior of these cords, made of hemp, ends inside the upper third of the leg. It limits the extension of the knee, exactly as described in the Marks leg.

The other two cords extend down to the foot, which is attached in a manner very similar to that shown on page 54, but with a single rubber cylinder behind, and with the instep cut obliquely so that when the joint is in the resting position of equinus there is an opening in front amounting to an angle of 15° to 20°. The posterior cord, of hemp, is attached in the heel; the anterior, made of catgut with an indiarubber section, enters the foot obliquely and is fixed a little in front of the middle of the sole.

When the knee flexes, the wooden cross piece tilts, its posterior end becoming lower, its anterior higher (Figs. 91 and 92), the elastic of the anterior cord is tightened, thus raising the front of the foot, whilst at the same time the heel cord is relaxed. Thus the mechanism which produces extension of the knee acts at the same time upon the foot; when the knee is straight the foot is plantar flexed to 20°, when the knee flexes the foot comes to a right angle. Thus the foot becomes dorsiflexed at the same time as the knee flexes, as in ordinary walking.

If the action in walking is watched, it will be seen that as the limb is swung forward, the toe is raised so as to clear the ground.

The mechanism of this artificial leg resembles that of the "tendon leg," which was in such common use in England before the present war that it is often called the English pattern.--(ED.)

FIG. 91.

FIG. 92.--(FIGS. 90 to 92. Foot and Knee of Frees.)]

In the sitting position the anterior cord is not relaxed, there is no dead point, so that the knee always tends to extend. This is somewhat inconvenient.

Conversion of the articulated peg leg into the leg with free knee movement and vice versâ.

Whatever advantage it may be thought to possess, in our opinion the artificial leg with free knee joint is only suitable for sedentary occupations; it is not suitable for manual labourers and particularly for agricultural labourers who are obliged to get about on rough ground. Hence it is not uncommon for a patient who has been provided with an American leg to come and ask for a peg leg. In figures 93 to 95 it will be seen that it is a simple matter to transform the limb into an articulated peg. It is only necessary to attach the stirrup-shaped fork of the peg to the thigh piece by the knee bolt, and to add the double lock. To this peg may be added, if desired, the show calf and foot described on page 32. The full artificial leg can be rebuilt whenever it is wished.

On the other hand, an articulated wooden peg leg, such as we have described under the name of the Federation leg, can be easily adapted for walking with a free knee. It is only necessary to unlock the knee joint and to add the artificial muscle or accumulator of elastic shown in figure 98. This supplies the extending force, the value of which we have shown on page 36. We consider that this appliance is excellent and we know patients who almost always walk upon the peg, but who sometimes use a free knee for short walks. The conversion is simple and requires no special care. Under these conditions the fixed foot is almost always used; there is nothing to prevent the fitting of an articulated foot, but we have already seen that there is no great difference in walking between the old-fashioned fixed foot of the Marks leg and the more or less complicated articulated feet of more recent design.

FIG. 97.

FIG. 98.]

II. Limbs without bearing upon the Ischium

For amputations through the condyles of the femur, and similar amputations (disarticulation of the knee and very short stumps below the knee).

Certain orthopædists do not know how to fit an artificial limb to an amputation through the condyles of the femur; they come therefore to the conclusion that this is a bad operation, and ought to be replaced by an amputation above the condyles.

The two objections raised to this amputation are:--

1. That it is impossible to fit a wooden bucket because the bone at the lower end of the stump is larger than it is at a higher level.

2. That it does not leave enough room to fit an artificial knee joint at the right level.