The Wrist Joint - Computational Biomechanics of the Wrist Joint - page 9

Fig. 1.6 Images of three-dimensional reconstructed wrist motions in radial deviation (a), neutral
(c and i), ulnar deviation (e), extension (g) and flexion (k)[ 35 ]
further supported by several kinematic studies investigating similar wrist kine-
matics [ 32 , 33 ].
Motion of the wrist joint can be divided into three groups: flexion-extension,
radial-ulnar deviation and forearm pronation-supination. A combination of these
motions, namely circumduction, were found to have reduction of 17 % for flex-
ion-extension and of 11 % for radial-ulnar deviation than for planar motion [ 33 ].
The wrist motions were found to have unique ranges. For flexion and extension,
the normal range was 65-80 o of flexion and 55-75 o of extension [ 28 ]. A study on
40 subjects (20 for each gender; age ranged from 20 to 60 years) has revealed an
average maximum ranges of wrist motion of 59 o extension to 79 o flexion (138 o arc
of motion). Generally, due to slight palmar tilt of the distal radius surface, the
flexion normally exceeds extension by an average of 10 o . An approximation has
been made in conjunction with the contribution of proximal and distal carpal rows
to the total arc of flexion and extension [ 28 ]. During flexion, 40 % occurs at the
radiocarpal joint while the remaining 60 % occurs at the midcarpal joint. The same
percentage occurred during extension, however the locations of occurrences were
switched: 40 % at the midcarpal and 60 % at the radiocarpal joint. Previous
studies have determined that movement between the capitate and third metacarpal
was small, thus it has been suggested that these two bones in relative with the
radius to be the axis in determining movements of the wrist joint [ 32 , 34 ].
Motions at the coronal plane involved out of plane movements. During radial
deviation, the scaphoid flexed with rotation of its distal pole towards palmar due to
the intruded styloid process of the distal radius. All the proximal carpal bones are