New Approch for Elbow Prosthesis Technology

Elbow is a bone joint having a single axis and performing two movements: flexion and extension. Because this axis, passing through trochlea and humerus, is not perfectly transversal, but oriented from outside to inside, forward to backward and from up to low, during the two movements the forearm and the arm form an opened angle. Consequently, the complex movement guided around this axis supposes particular shapes for the articulated bones in elbow and to design and realize prosthesis in case of important damage becomes a long and difficult procedure. More, the dimensions of prosthesis depend on anthropomorphic sizes of every patient. For these reasons, in the present paper, we propose an approach much more rapid and more cheap – rapid prototyping (RP). The proposed technology is thermal injection, which is a part of RP technology. It allows executing rapidly solid 3D models by CAD and, after that the prototype is done in short time, in accord with needed dimensions and with a very good quality. The specific device is technically simple, needs less material and more rapid. 1. ELEMENTS OF ARM’S BIOMECHANICS The human arm contains bones, joints, muscles, nerves, and blood vessels. Many of these muscles are used for everyday tasks. The humerus is the (upper) arm bone. It joins with the scapula above at the shoulder joint (or glenohumeral joint) and with the ulna and radius below at the elbow joint. The upper arm bone is not easily broken. It is built to handle pressure of up to 13361 N (300 lbs). The elbow joint (figure 1) is actually three separate joints; the ulnohumeral joint, the radiohumeral joint and the superior radioulnar joint. A single joint capsule encloses all three joints. Figure 1. Elbow joint. Figure 2. Carrying angle of elbow.