A. Attachment to the Elbow.—The simplest method of attachment is that in which pressure is exerted upon the condyles of the humerus ([Fig. 124]). A leather armlet laced in front is furnished with two lateral steels, curved in above the condyles and articulated at the level of the centre of rotation of the elbow joint with two similar steels in the forearm piece (the socket).
Fig. 123.—The three regions used as points of support, the shoulder, the elbow and the wrist.
Fig. 124.—Suspension from the elbow. The side steels of the arm piece are curved in to fit upon the supra-condylar ridges of the humerus. A good method of suspension for long stumps, when the appliance is not to be used for heavy work. It should be supplemented in other cases by direct suspension from the shoulder.
This direct method of attachment is sufficient for a low amputation, in cases where the patient does not do hard work. But if the stump is short and if the patient has to carry fairly heavy weights the appliance is only prevented from slipping by a considerable constriction of the arm, which results in a serious interference with muscular action.
B. Attachment to the Shoulder.—For this reason it is usually advisable to supplement this by an indirect attachment to the acromion and clavicle by means of a shoulder cap.
Fig. 125.
The firmest and strongest pattern consists of a piece of blocked leather, moulded to the shoulder, including the pectoral, supra-clavicular and scapular regions. This is kept in place by a strap which passes under the opposite axilla. It is cut away on the outer side of the acromion, the anterior and posterior borders being continued downwards on either side of the deltoid as two tapering straps to which the armlet is attached. In this way full liberty of movement is allowed to the shoulder (Fig. 125).