Biomechanical Study And Three-dimensional Finite Element Analysis On The Effect Of PEEK Rods System On The Intradiscal Pressure Of Adjacent Segments

ObjectiveTo analyze the effects of PEEK(polyethererketone)rods pedicle screw system on the intradiscal pressure of adjacent segments by biomechanical experiments and three-dimensional finite element modeling.MethodsTen lumbar spine(L3–L6)specimens from ten fresh sheep cadavers(8–10 weeks of age)were used.Each specimen was treated with different fixation methods in turn.According to the different process modes,each specimen was divided into the following 5 experimental groups: no instrumentation(INTACT group);titanium rod with single segment fusion(TS group);PEEK rod with single segment fusion(PS group);PEEK rod with double segments hybridization group(PD group);titanium rod with double segments fusion group(TD group).Using MTS(Multi-degree of spine movement simulation test system),each specimen was subjected to such movements as flexion,extension,left and right bending,left and right torsion.The axial pressure is 50 N.Outcome measures included intradiscal pressure(IDP)during those movements.ResultThe intradiscal pressure of the adjacent segment in PS group and TS group were higher than that of the Intact group(P=0.00).The intradiscal pressure of the adjacent segment in TS group was higher than that of the PS group.The intradiscal pressure of the transition segment in PD group was lower than that of the adjacent segent in TS group.The intradiscal pressure of the adjacent segment in TD group was higher than that of the PD group.Under the given load and torque,L3/4 intervertebral pressure in titanium rod fixation with L4/5 fusion was normally increased in flexion,extension,lateral bending and axial rotation compared with the normal condition.But the results were reversed after the hybrid surgery by PEEK rods.ConclusionCompared with rigid fixation system,the use of PEEK rods pedicle screw system will significantly reduce the intradiscal pressure of the adjacent intervertebral segment,and will lay the theoretical foundation for reducing the incidence of adjacent segment degeneration the further study on clinical treatment.