The Development of the Wrist and Hand

Abstract

Chondrification of wrist and hand progresses in a proximodistal direction. At stage 17, when the embryo measures approximately 12 mm, radius and ulna start to chondrify; both bones are widely separated. Subsequently, both styloid processes chondrify; they are well visible at stage 19. Also at this stage, elements of the carpus chondrify, starting with the capitate and hamate. The lunate and pisiform are the last to chondrify. By 6 weeks (Fig. 10.2) when the embryo measures approximately 18–20 mm, all bones but the distal phalanges can be identified. Of special interest is the formation of the os centrale situated between the scaphoid and capitate (Fig. 10.3). It is well seen toward the end of the embryonic period. During the fetal period it will fuse with the scaphoid. Before the fetal period starts, that is to say, at the end of the embryonic period, all elements of the hand have shapes, arrangement, and relationships we are used to seeing in adults (Figs. 10.4 and 10.7). At that time, sesamoids start to chondrify.