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.