Biomechanical study of a new lumbar dynamic internal fixation system / 中华创伤杂志

ABSTRACT

Objective To investigate effect of a new lumbar dynamic internal fixation system(DIFS)on the stability and intradiscal pressure of lumbar segment.Methods Eight fresh calf lumbar specimens were collected to build test models,which were loaded with pure moments of 8 N·m in flexion/extension,lateral bending,and rotation planes.The test states included intactness,destabilization,dynamic fixation,semi-rigid fixation,and solid fixation.The data were collected from the third loading cycle to determine range of motion and neutral zone of corresponding segments,and the intradiscal pressure.Results Destabilization significantly increased segmental range of motion and neutral zone in three motion planes without obvious influence on intradiscal pressure.The three fixation systems were all able to stabilize and load destabilizing segments.DIFS restored the range of motion of unstable segment to 77％,60％,61％ and 70％ of the intact level in anterior flexion,posterior extension,lateral bending and rotation planes.Meanwhile,DIFS bore 45％,29％ and 40％ of tbe intradiscal load in lateral bending,rotation and flexion directions,but 100％ of the intradiscal load in back extension.The stability and intradiscal pressure of adjacent segments were not affected by the test states.Conclusion DIFS can effectively restore range of motion of unstable segments and share appropriate intradiscal load in most directions.