[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.) [Illustration: FIG. 132.--Bad apparatus for amputation in the upper third of the forearm. The front of the arm piece is insufficiently cut away.] [Illustration: 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. [Illustration: FIG. 134. 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). [Illustration: FIGS. 136 and 137.--Amputation through the forearm above the upper third. The elbow joint does not flex beyond the right angle.] [Illustration: FIG. 138.--Limb for amputation through the upper third of the forearm. (For a description of the ratchet see page 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).