| Objective:The anatomica parameters were measured through the digital reconstruction of scaphoid,trapezium and trapezoid.based on the results of measurements and statistics,We designed two new type of internal fixation and fusion devices- NiTi Shape Memory Alloy STT Arthrodesis Concentrator NT-STTAC.We conducted the biomechanics analysis between HNT-STTAC and NT-STTAC used the finite element analysis software and compared the mechanical stability of the two devices, hoped to make a good choice for clinical application.Methods:1. Select the samples aged 20-40 years, height 150-180cm Weight 45-80kg, 40 healthy volunteers after X film determined the wrist of no disease, men and women were 20 respectively, both two wrists joints were scaned by 64-slice spiral CT,The CT scan data were saved in DICOM format on the discs,then the discs were loaded into computer of the rapid prototyping laboratory,2.used the three-dimensional reconstruction software MIMICS (10.01 version, the Belgian producted)to reconstructed the wrist bones solid model.3. used the visualization function of MIMICS software to separat the scaphoid,trapezium and trapezoid, Measured the anatomica parameters used MIMICS measurement's tools directly.Then we compared the data about gender, left and right wrist bones by SPSS 16.0 and calculated the means and standard deviation, the height and weight measurement's results were carried on with Person correlation analysis.4.We designed the sketches of the NiTi Shape Memory Alloy STT Arthrodesis Concentrator based on anatomic parameters by CAD, then designed the three-dimensional map by UG, saved for the IGS format to prepare for finite element analysis.5. The three-dimensional map of the two fusions were loaded into the finite element analysis software ANSYS (11.0, U.S. producted), the materials mechanical properties were given to build the three-dimensional finite element model. fixed the NT-STTAC two remote arms and did axial tensile and axial compression load 20,40,60,80,100N from the proximal arm to the two remote arms, then we get the stress distribution of the two NT-STTAC, calculated of the force results of all nodes, drawn the stiffness curve to compare the mechanical stability differences between the two fusions 6.From august 2006 to may 2011, we treated rotatory subluxation of the scaphoid and KienbOck disease of 10 patients used NT-STTAC,and followed up to evaluate the efficacy of NT-STTAC.Results:1. scaphoid,trapezium and trapezoid have constant bone signs.Length of the scaphoid(26.58±2.72)mm,Width of the scaphoid (13.99±1.72) mm,Depth of the scaphoid(12.97±1.92),Length of the trapezium(16.30±1.35),Width of the trapezium (14.29±1.47),Depth of the trapezium (10.36±0.53),Length of the trapezoid(11.62±1.25),Width of the trapezoid (11.82±1.84),Depth of the trapezoid (15.03±1.20) mm,Depth of the trapezium is the shortst。Length between the scaphoid and trapezium(37.80±1.75) mm,Length between the scaphoid and trapezoid(32.04±2.40) mm, Length between the trapezium and trapezoid(30.42±1.95) mm。2. We compared the measurement data of left and right hand, P>0.05, the same person have no significant difference between the left and right hand. The Comparison of left and right wrist between men and women:the measured values were significantly different, P<0.01, all data on height and weight were carried Correlation analysis:The measurements have significant correlation in height but moderately correlated in weight.3. To the mechanical performance, mechanical stability of the two fusions are similar, the overall observation:the mechanical stability of solid fusion slightly stronger than he hollow-type fusion.4. The 10 patients were followed up for 6 months to 2 years (mean 12 months), all of rotatory subluxation of scaphoid and KienbOck disease were recovered,and pain relief, activity increased. Conclusion:(1) The measurement standards did in accord with the scaphoid,trapezium and trapezoid bone marks can quantitative the irregular carpal bones.(2)When we do the arthrodesis based on measurement data, we can avoid to damage the adjacent joints, reduce the complications and improve the STT fusion rate.(3) the measurement data provided the key parameters for the design of the NiTi Shape Memory Alloy STT Arthrodesis Concentrator.(4) The designe of NT-STTAC comply with the carpal bone morphology and anatomy, and the fixed strength after surgery without need external fixation and can do early functional exercise. Biomechanical stability can meet the cure need for STT.(5)NT-STTAC is the effective treatment of rotatory subluxation of the scaphoid and KienbOck diseases.
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