| The spine fixation system has been improved very quickly in these years. But there is much trouble about it, such as the screw becomes flexible and break in the early, or fake arthrosis was found in later. All of these troubles need revision to conquer. There are many scholars have tried to solve the problems by many ways. Such as adding the length or diameter of the screw; betterment the screw thread. Some scholars put things, such as spongy bone, molar bone mad. PMMA, PPF, CPC, HA and so on, in the nail road when revising.There are some literatures said that the mean that add the length of screw is useful to enhance the pull-out strength in revision, but many doctor suggested that the depth of the screw in the vertebral body not over the 80% of the length from the entrance of screw to the front edge of vertebral body in the first time, at the same time the difference of the strength cause by the depth, from 80% to 100%, of the screw in the vprtebral is no significant in statistics, and there is the dangerous the screw damage the blood vessel or nerve if it is too long. That way add the diameter of the screw is also useful in revision, but you must add the diameter over 2mm, and it is dangerous that damage the vertebral arch is higher with adding the diameter, and it also damage the nerve rood if the vertebral arch fracture. There are many reports about improvement on the screw thread and have the significant in the statistics, such as GSS, but all of these have not the significant difference in use. the method putting the bone is useless to enhance the pull-out strength. Using the PMMA to revise, the pull-out strength was enhancedsignificant in statistics, the strength could to be enhanced as same as before revision if not adding press, the strength could to be enhanced as twice as before revision if adding press. But the way has some disadvantage: the PMMA can not be absorbed by the body; Cause the bone putrescence for release the heat when solidifying; release the toxin in the body; damage the nerve root if the PMMA enter the vertebral canal; be get rid of is very difficulty if the PMMA not at it is place. All the disadvantages limit the PMMA is used in revision. But it is the most useful way to revise. The PPF CPC and HA also can enhance the pull-out strength in revision, but them not so good as the PMMA, and can not avoid damage the nerve root. So there are many scholars still researching the revision and hoping improvement.The transpedicular balloon kyphoplasty came from the vertebroplasty has developed very well in recently years. But the technique usual was used to treatment aged osteoporotic spinal compress fracture. There is a cavity with bone wall in the vertebral body after the balloon was inflated in the vertebral, the bone cement solidify in the cavity, so let the dangerous that the cement leakage down smartly, and also avoid the bone cement damage the nerve rood. We know that the balloon also can be inflated in the normal vertebral body. We did not found the report that the balloon was used in revision. We use the ESS (Expansion spine system) screw devised by ourselves to do a biomechanical to compare the ESS with others screws. We also use the balloon to make a cavity and fill the cavity with PMMA, screw the CD- II to revise.Objective To measure and compare the insertion torque and pull-out strength of ESS with CD- II ,TRSH and GSS. We also measured the insertion torque and pull-out strength of the revision with PMMA to evaluate the new method.Method 40 lumber vertebrae came from 8 fresh normal male cadavers and were assigned into 4 groups randomly. 20 pedicles per group. Measured the bone mineral density at the first. CD- II (6.0mm,45mm)were inserted as control in both pedicle of every vertebral body. Control pull-out test of the screw was performed. For each pedicle pair of the ABC groups, salvage of one of the CD- II (6.0mm,45mm) screw site performed use a ESS(7.0mm,45mm),and salvage of another CD- II (6.0mm,45mm) screwsite with CD- II (7.0mm,45mm) in group A, TRSH (7.0mm,45mm)in group B, which pedicle received which of the screw tested was made at random. The maximum axial pull-out strength and the torque was recorded. We also measure the insertion torque and pull-out strength of the group D after screw the CD- II (6.0mm,45mm), we inject the PMMA in the cavity which was made with the balloon, and screwed the CD-II (6.0mm,45mm), we measured the insertion torque and pull-out strength again and recorded them.Results The maximum pull-out strength of ESS in the ABC groups was larger than the contrast screws and the difference was significant in statistics (P<0.05). but there was no significant different in statistics of the insertion torque strength. The maximum pull-out strength of the D group was larger than the CD-II (6.0mm,45mm) and the current no adding press method and the different was significant(P<0.05), the maximum pull-out strength also larger than the adding press method but the different no significant(P>0.05). the insertion torque strength smaller than the CD- II (6.0mm,45mm) and there was significant different in statistics.Conclusions ESS screws offer better anchoring in revision surgery than the currently used screws do. The new mean not only offer better revision than current ways, but also avoid damage nerve rood. |
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