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Hands and Handles
Published in Stephen Pheasant, Christine M. Haslegrave, Bodyspace, 2018
Stephen Pheasant, Christine M. Haslegrave
Standard anatomical terms that are used to describe the position and movements of the forearm, wrist and hand are illustrated in Figure 6.2. The movements of flexion, extension and radial and ulnar deviation occur at the wrist joint complex, that is, at the ‘true’ wrist (radiocarpal) joint and at the various articulations which are present between the eight small bones of the wrist (intercarpal joints). Ulnar deviation is sometimes also known as ‘adduction’ of the wrist and radial deviation as ‘abduction’, but the terms are confusing and are best avoided. (Extension is also sometimes called dorsiflexion, with flexion then termed palmar flexion.)
Development of a 3D scan posture-correction procedure to facilitate the direct-digital splinting approach
Published in Virtual and Physical Prototyping, 2019
Ilja Asanovic, Huw Millward, Alan Lewis
To create a control system (internal skeleton) for the hand segment articulation on initial scans, a rigging process was developed. The rigging process starts from manual determination of the wrist joint location. Since the wrist contains eight carpal bones and numerous intercarpal joints, and acts as a ‘spacer’ between forearm and hand (Neumann and Grosz 2016), to determine bounds of the wrist (distal forearm and proximal hand locations), target scans in extended hand posture were analysed along with initial scans. At first, target scans were split up approximately in the middle of the wrist into two resultant hand and forearm segments. Generated segments were re-aligned to the corresponding initial scans in Artec Studio 11 Professional software by indicating bumps on the forearm and hand locations. Then, aligned segments with corresponding initial scans were analysed in geometry inspection software INSPECTplus v5.55 with surface comparison tools. Initial scans were assigned as a nominal geometry and aligned forearm and hand segments were set as an actual geometry. After surface comparison procedure, analysed geometry with deviation texture maps were imported into the modelling software Rhinoceros 3D. Generated deviation texture information on actual models made it possible to visually determine and trace the region of the wrist joint on initial scans mesh geometry. As a result, two polylines for every initial scan were generated to mark the bounds of the wrist joint. To an internal skeleton for hand segment posture correction, two surface planes were fitted through extracted control points of generated polylines. Finally, the manual rigging process was accomplished by creating two additional surface planes which indicate proximal forearm and distal hand locations on the initial scans geometry. The overall process of wrist joint bounds determination and planar surface fitting is shown in Figure 4.