Elbow flexion-extension

Elbow and knee joints Bend from the fully straightened position Flexion (extension") ... 

Forearm and hand posture. Extreme elbow flexion or extension, extreme forearm pronation or supination, and extreme wrist flexion or extension should be avoided. The hand should be in line with the forearm (no ulnar/radial deviation of the wrist). 

The bony structures of the elbow are the distal end of the humerus and the proximal ends of the radius and ulna. The elbow joint complex allows two degrees of freedom in motion flexion/extension and pronation/supination. The elbow joint complex is three separate synovial articulations. The humeral-ulnar joint is the articulation between the trochlea of the distal radius and the trochlear fossa of the proximal ulna. The humero-radial joint is formed by the articulation between the capitulum of the distal humerus and the head of the radius. The proximal radioulnar joint is formed by the head of the radius and the radial notch of the proximal ulna. 

A combination of glenohumeral flexion and shoulder abduction is the primary body-control motion used to affect terminal device opening and closing or elbow flexion and extension. Typically, a total excursion of 10 cm (4 in) and upward of 222 N (50 Ibf) of force are possible using these motions. Elbow lock control is affected by a complex shoulder motion which involves downward rotation of the scapula combined with simultaneous abduction and slight extension of the shoulder... 

The primary sources of control for body-powered devices are biomechanical in nature. Movement, or force, from a body joint or multiple joints is used to change position, or develop a force/ pressure that can be transduced by a harness and Bowden cable and/or mechanical switches. Typically, inputs such as chin and head force/movement, glenohumeral flexion/extension or abduction/ adduction, biscapular and scapular abduction, shoulder elevation and depression, chest expansion, and elbow or wrist movements are used. However, direct force/motion from muscle(s) has also been used by way of surgical procedures such as muscle tunnel cinepiasty (Sauerbruch, 1916) and the Krukenberg cinepiasty (Krukenberg, 1917). 

For prosthetic arms to be more than just position controllers for portable vices, multifunctional mechanisms that have the ability to have multiple degrees of freedom controlled simultaneously (in parallel) in a subconscious manner need to be developed. Current commercially available multifunctional controllers are generally sequential in nature and take the form of two site, three state multifunctional controllers. Motion Control, Inc., in the ProControl hand-wrist controller, uses rapid cocontraction of the forearm extensors and flexors to switch control between hand opening and closing to wrist rotation. Otto Bock uses a similar control strategy in its wrist-hand controller. Motion Control, Inc., in its elbow controller, uses dwell time (parking) to switch from elbow flexion and extension to hand opening and closure and cocontraction of biceps and triceps to switch control from the hand back to elbow. 

To prevent impingement, the lower end of the humerus has two fossae, one at the front and one at the back. This gives the human elbow a range of 0 -142° of flexion extension with 5 of further passive flexion. About 9 of abduction and adduction exist in the ulno-humeral joint. This range of movement is essential to complete the full arc of pronation and supination. 

The motions observed in the elbow joint are flexion, extension, and rotation (supination and pronation). Flexion and extension are the only motions that involve the true elbow joint, the ulna with the humerus. The elbow joint has the composite motions of elbow flexion, with forearm supination, and elbow extension, with forearm pronation. Therefore, the superior radioulnar joint and its motions complicate, and are part of, elbow joint motion. 

The bone structures about the elbow joint include the proximal ends of the ulna and radius and the distal end of the humerus (Fig. 8.1). The radial head articulates with the humeral capitellum in a pivotal mode and the ulna with the humeral trochlea in a hinge mode. The proximal radio-ulnar articulation is composed of the radial head which revolves within the sigmoid (radial) notch of the ulna allowing pronation-supination movements. These articulations cooperate during complex joint movements allowing a wide degree of flexion, extension and axial... 

The elbow is one of the most stable joints of the body. In normal states, elbow joint motion ranges approximately from 0° to 150° of flexion and from 75° in pronation to 85° in supination. Elbow extension is limited by contact of the olecranon in the posterior humeral fossa, and tightening of the anterior band of the medial collateral ligament, of the joint capsule and of flexor muscles. On the other hand, the bulk of anterior muscles of the arm, the tension of the triceps and the contact of the coronoid process in the anterior humeral fossa limit elbow flexion. Pronation and supination movements are primarily limited by passive muscle constraints rather than ligaments. 

Fig. 8.64a,b. Snapping triceps syndrome. Schematic drawings of the posterior aspect of the elbow in a extension and b 90° flexion demonstrate the ulnar nerve (arrows) as it passes through the cubital tunnel and a prominent medial head (mh) of the triceps muscle (tin). Note the absence of the Osborne retinaculum when compared with Fig. 8.7c. With elbow flexion, the medial edge of the triceps (arrowheads) and the ulnar nerve move anterior to the tip of the epicondyle. T, distal triceps tendon /c , flexor carpi ulnaris...

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