ABSTRACT
BACKGROUND:Self-made Distraction Reduction Fixation System is characterized by Distraction Reduction Fixation functions,which can completely fuse to the design of steel plate,and by no need to provide many surgical instruments,by reduction of bleeding and trauma.OBJECTIVE:To test changes in the stiffness of porcine short spinal segments in integrity and following destabilizing and internal fixation of the Distraction Reduction Fixation System.DESIGN,TIME AND SETTING:The control observation experiment was performed at the Laboratory of Biodynamics,Institute of Onhopedics,General Hospital of Chinese PLA from December 2004 to December 2005.MATERIALS:Twelve fresh porcine lumbar spines(T11-S2 segments)were bought from a market.Upper and lower segments were crossed and inserted with Kirschner wire to make porcine spine samples of the L1-7 segments.METHODS:Stiffness of intact samples was recorded during forward-bending,backward-bending,lateral-bending and axial rotation.Intervertebral discs,facet ioints,anterior and posterior longitudinal ligaments were removed to loose the spine.Stifrness of each motion was measured.Stiffness tests were repeated again after internal fixation on short segments using Distraction Reduction Fixation System.MAIN OUTCOME MEASURES:Stiffness in the intact,unstable and internal fixed spines during each motion.RESULTS:The stiffness iu unstable porcine spine were significantly lower than those in intact porcine spine(P<0.05),but the stiffness after internal fixation was significantly higher than in unstable porcine spine(P<0.05).No significant difference was detected in stifiness during forward-bending,lateral-bending and axial rotation(P>0.05)except that it was significantly higher during backward.bending after internal fixation compared with the intaet spine(P<0.05).CONCLUSION:Biodynamics confirms that the stiffness in short-segment fixation porcine after using Distraction Reduction Fixation System is markedly increased than in unstable porcine spine,except during backward-bending,which is comparable with that in intact porcine spine.