The Design,biomechanical Eveluation And Clinical Application Of A Kind Of Short Reduction-fixation(HOIST Device)for Lumbar Spondylolisthesis.

Spondylolisthesis is a main reason for back pain occurred very popularly in clinic. Although they still didn't draw a conclusion on the treatment of spondylolisthesis, the majority of scholars proposed the reduction--pedicle screw fixation--back intervertebral fusion method. This study aimed to intruduce and evaluate a new kind of pedicle fixation system. Three parts are comprised in this paper. The design principle, structure and installing methods were recommended in the first part. HOIST divice is composed of the hauling screw, open angle screw(upholding screw),blocker,angle connective bar and blocking ring.The dign principle or behavior of this device is to draw Out and reduce the slippage segment by means of taking lower adjacent vertebrae as the lever fulcrum. It may be an simple and efficient devices for spondylolisthesis. In the second part of this study, the biomechanical tests of lumbar spondylolisthesis fixed with HOIST device were evaluated, including the stability of both injuried and adjacent segments, and the pull-out strength of screw. (1) The stability of injuried segment.Objective: In order to evaluate the stability of injuried segment. Methods: Each of seven adult cadaver specimens of lumbarsacral segments (L2-S2) was analyzed in four states: Intact (A); Spondylolisthesis (B); Fixed with HOIST device (C); Fixed with DICK system (D). A kind of nondestructive test was performed with the ~pina1 three dimensions analysis system for them. Results: The range of movement (ROM) of spondylolisthesis (B) state was significantly g eater than that of intact state (A) and two fixation (C and D)states (?0.05); The difference between C and D is not significant at the 0)5 level; The ROMs of state C and D were significantly limited t ian that of state A in extension, flexion and left rotation. Conclusion: The effect of spinal stability fixed with HOIST is as strong as that of DICK device. (2) The instantaneous stability of the adjacent segment of fixed lumbar. Objective: To get the knowledge of the stability of the adjacent segment. Methods: Each of seven adult cadaver specimens of lumbarsacral segments (L2-S2) was analyzed in five states: Intact(A); LA spondylolisthesis (B); L45 fixed with HOIST device (C); L45 fixed with DICK system(D); L34. L45 fixed with DICK system (E). A nondestructive test was performed on L5S1 segment with the spinal three dimensions analysis system too. Results: There was no significant difference betreen them except the result of flexion movement, in which the ROM of state E showed a significantly greater than that of state A or B (P<0.05). Conclusion: Although it was thought that the ROM of adjacent segment would be different from that of pre-operation, the post-operative change instantly of the stability of the adjacent segment was not significant. The ROM of longer fixed lumbar instantly was greater than the others, especially in flexion movement. (3) A study on the pull-out strength of pedicle screws in relative with the size of the screw and the bone mineral density. Objective: To evaluate the pull-out strength of pedicle screws. Methods: 88 fresh vertebral pedicles were obtained from 4 adult cadaver specimens(T2 Li). The diameter and BMD of each pedicle were measured. The relative diameter (screw pedicle) we prepared is range from 45% to 85% mm. According to the relative diameter (screw! pedicle) (A) and BMD(B), the tests were classified into 9 groups (...