Objective. The purposes of the present study were to investigate the feasibility of using a skin sensor to represent the first and third metacarpal bone, to verify that there was no significant relative motion between the skin of the third metacarpal bone and trapezium bony segment and to measure thumb metacarpal motion with respect to the hand (third metacarpal). Design. Eight hands from fresh-frozen human cadavers were disarticulated 4 cm proximal to the wrist joint and used in this experiment. Background. Recently, magnetic-tracking systems have been developed for the measurement of joint kinematics. Based on the concept of the three-dimensional space within which the thumb metacarpal bone can move, the current study proposes a 3D method for evaluating the relationship between the skin and bony segment. Methods. An electromagnetic tracking system was used to provide quantitative measurement and evaluation of the relationship between the skin and bony segment while moving the trapeziometacarpal joint. Results. The adjusted coefficient of multiple determination, Ra2, values of the kinematic waveforms between the sensors were larger than 0.84. The angular differences and displacements of the center of sensors between the skin and bony sensors were less than 4.9° and 2.8 mm. Conclusion. These data revealed that the similarities of the two sensors throughout the motion cycle were high. The differences between the two sensors were also within the clinically allowable range of ±5°. Therefore, it is feasible to collect motions of the first metacarpal by attaching the skin sensors at the metacarpal head to measure the bony segment.
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