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Designing for Upper Torso and Arm Anatomy
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
At its distal end, the humerus articulates with both bones of the forearm—the radius and ulna—at the elbow. The ulna is the longer of the two forearm bones. In contrast to the shoulder joint, the elbow joint is complex in structure (it has three synovial joints which share a single joint capsule), but simpler in function. The three joints are the humeroulnar (between the humerus and ulna), the humeroradial (between the humerus and radius), and the proximal radioulnar (between the radius and ulna) joints (refer to Figure 4.21). Because of the shape of the humeroulnar joint surfaces, when the arm is in the anatomic position (elbow extended and palm facing forward) the forearm is angled away from the body; in other words, it does not lie in a straight line with the upper arm. Seen in Figure 4.17, this lateral deviation is called the carrying angle (Jenkins, 2002, p. 117). Carrying angle is a medical term referring to how the forearm is positioned relative to the arm, not how a product is carried. The carrying angle is usually greater than 15 degrees in women, but only 10 to 15 degrees in men (Moore et al., 2011, p. 483). The angle between the arm and forearm is smaller when the arm is in a more natural gesture with the palm facing the body (Jenkins, 2002).
Hands and Handles
Published in Stephen Pheasant, Christine M. Haslegrave, Bodyspace, 2018
Stephen Pheasant, Christine M. Haslegrave
The forearm has two long bones — the radius and ulna — which run from the elbow to the wrist and articulate with each other at their top and bottom ends. When the hand is in its palm up or supine position, these two bones are parallel. (The radius is on the thumb side; the ulna is on the little finger side.) As the hand is turned into the palm down or prone position, the lower end of the radius rotates about the axis of the ulna and the shafts of the two bones cross — a movement which can be felt when lightly holding your arm just above the wrist. Note then that the movements of pronation and supination occur at the two articulations between the radius and ulna rather than at the wrist as such. In practice, however, the natural hand movements we use in everyday life often entail actions of pronation and supination in combination with movements occurring at the wrist.
Pain mapping and health-related conditions in relation to forearm crutch usage: A cross-sectional study
Published in Assistive Technology, 2020
Danielle Brasil-Barros-da-Silva, Emerson Fachin-Martins
According to scientific evidence, we can suppose that users of forearm crutches commonly report discomfort and undesirable outcomes. Among problems reported, we have found ulnar nerve compression, articular wrist, elbow, and shoulder overloads, and fractures of the ulna and radius (Fischer et al., 2014; Rogers et al., 2016). Our objective was to explore whether permanent or temporary usage of forearm crutches could be associated with some of the selected features of health-related states by domains of human functioning. We hypothesized that health-related conditions and pain might differ according to permanent or temporary usage of forearm crutches.