Influence of dehydration degree on biomechanics of allogeneic bone nails / 中国组织工程研究

ABSTRACT

BACKGROUND:With increasing freeze-drying time,the water content of allogeneic bone reduces along with the bone mechanical strength.The suitable dehydration degree that maintains mechanical strength of allogeneic bone and allows long-term preservation at room temperature remains controversial.OBJECTIVE:To detect the mechanical properties of bovine bone nail following different degrees of dehydration using the three-point bending mechanics tests.DESIGN,TIME AND SETTING:Biomechanical analysis,comparative observation.The experiment was performed at the Mechanical Laboratory of Southern Medical University between May 2007 and May 2008.MATERIALSBone nails,50 mm length and 3 mm diameter,made from healthy adult bovine femoral cortical bone were divided into control and freeze-drying groups (8,12,24 hours,respectively) with 20 samples in each group.METHODS:The water content of bone nails with or without freeze-drying was measured by SH10A Moisture Quick Determination Meter.Three-point bending mechanics tests were performed using MTS 858 Mini Bionix.The parameters included load range 0-2000 N,resolution 0.01 N,cross beam replacement resolution 0.001 mm,span 50 mm and loading speed (cross beam replacement speed) 2 mm/min.MAIN OUTCOME MEASURES:Water content,maximal load and elasticity load.RESULTS:The water content of control group was 7%-9%,and following freeze-drying for 8 hours,the water content was 5.5%-6%,which met the standard of freeze-drying bone;Compared with control group,the maximal load and elasticity load reduced respectively 0.004% and 0.000 8% (P＞0.05).Following freeze-drying for 12 and 24 hours,the water content was 3.5%-4% and 1%-1.5%;the maximal load reduced 21% and 37% and the elasticity load reduced 22.5% and 39% compared with control group (P＜0.05).CONCLUSION:Freeze-drying for 8 hours is the best time of dehydration.The mechanical load and elastic modulus reduce with increasing freeze-drying time.