| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 91 === External fixators have been widely used for distal radial fractures. The purposes of this study were to analyze the adjustable ranges for wrist external fixators, including Orthofix, Trauma-Fix and a new external fixator designed in National Taiwan University Hospital. The external fixator was assumed to be fixed to two cylinders. The relative motion between these two cylinders, which represent the adjustable range of motion was analyzed by kinematic equations. Each link and joint of the external fixator was described by a 4×4 homogenous transformation matrix. The kinematic equations were established by concatenating these homogenous transformation matrices. Z-X-Z representation was used to describe the sequence of the motion of the components. The contribution for each design parameter of external fixator was thus investigated by the Taguchi method. In addition, strength and stability of Trauma-fix and the new external fixators were tested by the biomechanical experiment.
The present study showed that the adjustable range of motion could be increased as follows: 1. increasing the range of motion of the ball joints; 2. increasing the length of the central body; 3. putting the telescoping joint between the ball joints; 4. increasing the length of the telescoping joint; 5. putting the position of the pins lined up with the axis of the ball joints. During surgery, the surgeons had better keep the elongation length of the telescoping joint as close to a critical level as possible. Beyond and below this level may decrease the range of adjustability. Furthermore, decreasing the pin length and keep the fracture at the middle of the external fixator may also increase the adjustable range of motion. The results of the kinematic studies could be verified by trigonometric models and computer simulation. The mechanical studies showed that the new external fixator had equivalent fixation stability with the Trauma-Fix in bending tests. However, the torsional stability of the new external fixator was much stronger than that of the Trauma-Fix. The stability of the new external fixator could be maintained by set screws.
The results of this study can help the engineer in designing a new external fixator and orthopedic surgeons handle the fixators during operation.
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