Wrist kinematics after radiolunate arthrodesis

Analysis of carpal kinematics after radiolunate and radioscapholunate arthrodesis shows good preservation of midcarpal joint congruity and motion. However, no biomechanical data exist on carpal kinematics after radiolunate arthrodesis in the wrist. Purpose of this study was to examine the individual motion of scaphoid, capitate and triquetrum after simulated radiolunate arthrodesis.

Radiolunate arthrodesis was simulated in three fresh human cadaver wrists by means of Kirschner wires. Individual motion of the scaphoid, triquetrum and capitate relative to the radius was measured for extension/flexion and radial-ulnar deviation before and after arthrodesis. Photostereogrammetric measurement was carried out and the helical axis concept of motion was employed.

Global wrist motion, corresponding to capitate motion, was found to be reduced 33-50 % for extension/flexion and 25-43 % for radial-ulnar deviation. Relative motion of the scaphoid for extension/flexion was found to be reduced 20 % more and for radial-ulnar deviation 10 % more than that of the capitate. Relative motion of the triquetrum for extension/flexion was found to be reduced 30 % more and for radial-ulnar deviation 20 % more than that of the capitate. The pattern of motion of the capitate hardly changed, and that of the scaphoid, only slightly. The triquetrum lost its rotational pattern of motion and gave way to tilting movements instead. The physiological function of the scaphoid between distal radius and distal carpal row was preserved.

The presented data conform with the good clinical results obtained after radiolunate arthrodesis in the rheumatoid wrist and furthermore, encourage its use in the posttraumatic wrist.