Our present knowledge of the three-dimensional kinematic behavior of skeletal joints has been largely acquired with cadaveric models and use of invasive monitoring. In the wrist, the small size and complex motion of the carpal bones present a difficult challenge for implanted internal or external marker systems. This paper describes a technique for quantifying the three-dimensional kinematics of the wrist and carpal bones in vivo using noninvasive computed tomographic imaging. An error analysis employing a cadaveric specimen suggests that noninvasive carpal kinematics can be measured with an accuracy within 2 degrees of rotation and 1 mm of translation along a helical axis of motion. The in vivo application of this technique is illustrated with a single normal individual. Potential applications include the quantification of normal wrist motion, analysis of pathomechanics, and evaluation of surgical intervention. The technique is also applicable to other joints and imaging modalities.

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The use of registration techniques to determine motion transformations noninvasively has become more widespread with the increased availability of the necessary software. In this study, three surface registration techniques were used to generate carpal bone kinematic results from a single cadaveric wrist specimen. Surface contours were extracted from specimen computed tomography volume images of the forearm, carpal, and metacarpal bones in four arbitrary positions. Kinematic results from each of three registration techniques were compared with results derived from multiple spherical markers fixed to the specimen. Kinematic accuracy was found to depend on the registration method and bone size and shape. In general, rotation errors of the capitate and scaphoid were less than 0.5 deg for all three techniques. Rotation errors for the other bones were generally less than 2 deg, although error for the trapezoid was greater than 2 deg in one technique. Translation errors of the bones were generally less than 1 mm, although errors of the trapezoid and trapezium were greater than 1 mm for two techniques. Tradeoffs existed in each registration method between image processing time and overall kinematic accuracy. Markerless bone registration (MBR) can provide accurate measurements of carpal kinematics and can be used to study the noninvasive, three-dimensional in vivo kinematics of the wrist and other skeletal joints.