Background:Reports on the efficacy of modifications to the thread design of pedicle screws are scarce.The aim of the study was to investigate initial and early fixation of pedicle screws with a plasma-sprayed titanium...Background:Reports on the efficacy of modifications to the thread design of pedicle screws are scarce.The aim of the study was to investigate initial and early fixation of pedicle screws with a plasma-sprayed titanium coating and dual pitch in the pedicle region(dual pitch titanium-coated pedicle screw[DPTCPS])in a polyetheretherketone(PEEK)rod semi-rigid fixation system.Methods:Fifty-four sheep spine specimens and 64 sheep were used to investigate initial(“0-week”controls)and early(postoperative 6 months)fixation,respectively.Sheep were divided into dual pitch pedicle screw(DPPS),standard pitch pedicle screw(SPPS),DPTCPS,and standard pitch titanium-coated pedicle screw(SPTCPS)groups.Specimens/sheep were instrumented with four screws and two rods.Biomechanical evaluations were performed,and histology at the implant-bone interface was investigated.Results:At 0-week,mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS(557.0±25.2 vs.459.1±19.1 N,t=3.61,P<0.05;622.6±25.2 vs.459.1±19.1 N,t=3.43,P<0.05).On toggle-testing,the DPTCPS was significantly more resistant than the SPPS and SPTCPS(343.4±16.5 vs.237.5±12.9 N,t=3.52,P<0.05;343.4±16.5 vs.289.9±12.8 N,t=3.12,P<0.05;124.7±13.5 vs.41.9±4.3 cycles,t=2.18,P<0.05;124.7±13.5 vs.79.5±11.8 cycles,t=2.76,P<0.05).On cyclic loading,maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS(1.8±0.13 vs.3.76±0.19 mm,t=2.29,P<0.05;1.8±0.13 vs.2.46±10.20 mm,t=2.69,P<0.05).At post-operative 6 months,mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS(908.4±33.6 vs.646.5±59.4 N,t=3.34,P<0.05;925.9±53.9 vs.646.5±59.4 N,t=3.37,P<0.05).On toggle-testing,the DPTCPS was significantly more resistant than the SPPS and SPTCPS(496.9±17.9 vs.370.3±16.4 N,t=2.86,P<0.05;496.9±17.9 vs.414.1±12.8 N,t=2.74,P<0.05;249.1±11.0 vs.149.9±11.1 cycles,t=2.54,P<0.05;249.1±11.0 vs.199.8±7.2 cycles,t=2.61,P<0.05).On cyclic loading,maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS(0.96±0.11 vs.2.39±0.14 mm,t=2.57,P<0.05;0.96±0.11 vs.1.82±0.12 mm,t=2.73,P<0.05).Resistance to toggle testing(370.3±16.4 vs.414.1±12.8 N,t=3.29,P<0.05;149.9±11.1 vs.199.8±7.2 cycles,t=2.97,P<0.05)was significantly lower and maximum displacement in cyclic loading(2.39±0.14 vs.1.82±0.12 mm;t=3.06,P<0.05)was significantly higher for the SPTCPS than the DPTCPS.Bone-to-implant contact was significantly increased for the DPTCPS compared to the SPPS(58.3%±7.0%vs.36.5%±4.4%,t=2.74,P<0.05);there was no inflammatory reaction or degradation of coated particles.Conclusion:DPTCPSs might have stronger initial and early fixation in a PEEK rod semi-rigid fixation system.展开更多
文摘Background:Reports on the efficacy of modifications to the thread design of pedicle screws are scarce.The aim of the study was to investigate initial and early fixation of pedicle screws with a plasma-sprayed titanium coating and dual pitch in the pedicle region(dual pitch titanium-coated pedicle screw[DPTCPS])in a polyetheretherketone(PEEK)rod semi-rigid fixation system.Methods:Fifty-four sheep spine specimens and 64 sheep were used to investigate initial(“0-week”controls)and early(postoperative 6 months)fixation,respectively.Sheep were divided into dual pitch pedicle screw(DPPS),standard pitch pedicle screw(SPPS),DPTCPS,and standard pitch titanium-coated pedicle screw(SPTCPS)groups.Specimens/sheep were instrumented with four screws and two rods.Biomechanical evaluations were performed,and histology at the implant-bone interface was investigated.Results:At 0-week,mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS(557.0±25.2 vs.459.1±19.1 N,t=3.61,P<0.05;622.6±25.2 vs.459.1±19.1 N,t=3.43,P<0.05).On toggle-testing,the DPTCPS was significantly more resistant than the SPPS and SPTCPS(343.4±16.5 vs.237.5±12.9 N,t=3.52,P<0.05;343.4±16.5 vs.289.9±12.8 N,t=3.12,P<0.05;124.7±13.5 vs.41.9±4.3 cycles,t=2.18,P<0.05;124.7±13.5 vs.79.5±11.8 cycles,t=2.76,P<0.05).On cyclic loading,maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS(1.8±0.13 vs.3.76±0.19 mm,t=2.29,P<0.05;1.8±0.13 vs.2.46±10.20 mm,t=2.69,P<0.05).At post-operative 6 months,mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS(908.4±33.6 vs.646.5±59.4 N,t=3.34,P<0.05;925.9±53.9 vs.646.5±59.4 N,t=3.37,P<0.05).On toggle-testing,the DPTCPS was significantly more resistant than the SPPS and SPTCPS(496.9±17.9 vs.370.3±16.4 N,t=2.86,P<0.05;496.9±17.9 vs.414.1±12.8 N,t=2.74,P<0.05;249.1±11.0 vs.149.9±11.1 cycles,t=2.54,P<0.05;249.1±11.0 vs.199.8±7.2 cycles,t=2.61,P<0.05).On cyclic loading,maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS(0.96±0.11 vs.2.39±0.14 mm,t=2.57,P<0.05;0.96±0.11 vs.1.82±0.12 mm,t=2.73,P<0.05).Resistance to toggle testing(370.3±16.4 vs.414.1±12.8 N,t=3.29,P<0.05;149.9±11.1 vs.199.8±7.2 cycles,t=2.97,P<0.05)was significantly lower and maximum displacement in cyclic loading(2.39±0.14 vs.1.82±0.12 mm;t=3.06,P<0.05)was significantly higher for the SPTCPS than the DPTCPS.Bone-to-implant contact was significantly increased for the DPTCPS compared to the SPPS(58.3%±7.0%vs.36.5%±4.4%,t=2.74,P<0.05);there was no inflammatory reaction or degradation of coated particles.Conclusion:DPTCPSs might have stronger initial and early fixation in a PEEK rod semi-rigid fixation system.
