| Objective To study the differences of biomechanical stability in the early tensile test and torsion test between cemented prosthesis and cementless prosthesis.To study the differences of biomechanical stability in the early tensile test and torsion test between sandblasted prosthesis manufactured by traditional preparation technology and trabecular bone prosthesis manufactured by three dimension printing technology.To contrast the ability of bone ingrowth and integration of bone in the interface between bone and prosthesis.And to further discuss the relation of trabecular bone prosthesis between the biomechanical stability and the ability of bone ingrowth and integration of bone in the interface between bone and prosthesis,which could provide theoretical basis for further clinical research.Methods We can develop three dimensional model of goat tibia based on the dicom data of CT,which adopt reverse engineering and rapid prototyping technology.And then we simulate a bone defect of the length with 2 cm in tibial backbone of goat.The diameter of backbone prosthesis of three types(cemented,sandblasted,trabecular bone)matches the medullary diameter of goat completely,which were prepared by Shandong WEGO Orthopedics Company.We carry out animal experiment of implanting surgery of tibial backbone prosthesis in vivo in the Orthopeadic Institute of Tianjin Hospital.The goats will be put to death in 8 and 12 weeks after operation respectively,with the purpose of observing new bone formation and bone ingrowth under the microscope.We also perform biomechanical testing including tensile test and torsion test for samples of three group different prosthesis.Results 1.General results: All experimental goats were lived postoperatively without infection,skin necrosis,prosthesis loosening or other complications occurred.The group of cemented prosthesis can bear load significantly earlier than sandblasted and trabecular bone prosthesis.2.Imaging observation: There is a large amount of new callus formation around prosthesis of cemented group and cementless group in 8 and 12 weeks after operation.The prosthesis of cemented group fully filled with cement between prosthesis and bone.The prosthesis of cementless group via close integration with bone,which shows no euphotic zone and decrease in bone density.3.Histological observations in interface:(1)Mineral apposition rate(MAR): MAR is(4.83±0.24)μm/d in 8 weeks after operation and(7.06±0.17)μm/d in 12 weeks after operation,whose MAR are both higher than the same period in the group of sandblasted prosthesis of(3.10±0.30)μ m/d in 8 weeks after operation and(4.90±0.35)μm/d in 12 weeks after operation respectively.And two prosthetic group of sandblasted and trabecular bone have statistically significant differences with the group and between groups(P < 0.05).(2)New bone formation rate(NBFR): NBFR in the porous structure of prosthesis of trabecular bone is 17.36% in 8 weeks after operation,which is much lower than the 35.40% in 12 weeks postoperatively.And the difference is statistically significant(P < 0.05).(3)Osseointegration rate(OR)between prosthesis-bone interface: OR in samples of prosthetic group of trabecular bone is 41.40% in 8 weeks postoperatively and 79.60% in 12 weeks postoperatively.OR in samples of prosthetic group of sandblasted is 37.60 % in 8 weeks postoperatively and 73.40% in 12 weeks postoperatively.OR in samples of prosthetic group of sandblasted is significantly lower than the same period in the samples of prosthetic group of trabecular bone,but the difference has no statistical significance between groups(P > 0.05).However,there is no statistically significant difference with the same group in different periods(P < 0.05).4.Biomechanical test:(1)Tensile test: Within the scope of the 500 N tensile load,the quantity of displacement for the same loading force: prosthetic group of cemented<prosthetic group of trabecular bone<prosthetic group of sandblasted.The differences have statistically significance among groups(P < 0.05).(2)Torsion test: Within the scope of the 2°torsion load,the torque of displacement for the same torsion angle: prosthetic group of cemented>prosthetic group of trabecular bone prosthetic>group of sandblasted.The differences have statistically significance among groups(P < 0.05).(3)Torsion destructive test: When the torsion destructive test fails,the specimens of three prosthetic groups(cemented,sandblasted,trabecular bone)achieve a maximum torque respectively:(30.42±0.40)N·m,(12.35±5.52)N·m and(15.65±1.94)N·m.And there is statistically significant between groups(P<0.05).When the torsion destructive test fails,the specimens of three prosthetic groups(cemented,sandblasted,trabecular bone)also achieve a biggest torsion angle respectively:(25.98-0.89)°,(10.47-5.69)° and(20.34-6.72)°.But the statistical result shows no significance between groups(P<0.05).Conclusion 1.The earlier stability of cemented prosthesis is obviously higher than that biological fixation prosthesis,which including sandblasted trabecular bone prosthesis.2.Trabecular bone prosthesis has better biomechanical stability than sandblasted prosthesis of same period,which reflects the stability for biological fixation prosthesis is dependent on not only tightly press-fitted system,but also ability of bone ingrowth and integration of bone in the interface between bone and prosthesis.3.The biomechanical stability of trabecular bone prosthesis has positive correlation with histomorphometry of bone. |
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