Experimental And Clinical Studies Of Fusion In Lumbosacral Spine

Lumbosacral spinal fusion is one of the common surgical procedures for low-back pain. Symptoms can be relieved by elimination of motion in the degenerative and br unstable spinal motion segments by fusion. However, Fusion can cause degeneration in the adjacent segments, and lumbar lordosis angles can be decreased at last, Fusion cause recurrent symptoms. So, in this paper. A retrospective study about spondylolsthesis treated by posterolateral fusion was conducted. Expecting to find some shortcomings of this treatment. The degenerative mechanism in the adjacent segments after fusion was researched by 3D-finite element analysis. In order to alleviate and/or postpone the effect of fusion to the adjacent segments. We design allograft cortical fusion cage (ACFC), and biomechanical properties of ACFC were tested. And we use it in the clinical practice. It was the first time that we offer interbody vertebral fusion with preseving endplate. The effect of different processed methods on biomechanical character and osteoinductive of allograft was also investigated. Part I. Long-term effects of lumbar spondylolisthesis treated with Iumbosacral posterolateral spinal fusion. Objective To investigate the long-term effects and influence factors of posterolateral fusion for spondylolisthesis. Methods From 1990 to 1996,35 patients with lumbar spondylolisthesis were followed up after underwent reducing and fixing with steffee system and posterolateral fusion. The contents followed up included: (1) Evaluating the long-term effect of the operation with JOA score.(2) Measuring the lumbosacral anteroposterior and lateral x-ray films in pre-operation, post-operation and the following-up course, mostly observing the fusion state, the intervertebral height in fusion segments and its upper and lower segment, and the changes of lumbar cobb?s angle.Results: 35 patients were followed up, the mean follow-up period was 6.7 years (range,4 to 10 year) The excellent and good rate of operation was 77.4%, 31 patients showed V bony fusion, The fusion rate was 91 .4%.4 patients had not fusion,2 patients without symptoms, another two with pseudarthrodesis. lumbar cobb?s angle decreased from 41.720 pro-operation to 39.23 0 post- operation. and it was 37,370 in the last. Intervertebral height in fusion segments and adjacent segments was decreased.Conclusion (1): posterolateral fusion and lumbar lordosis changing can accelerate degeneration in the adjacent segments. (2): Posterolateral fusion can not effectively curbed motion of the vertebral in the fusion segment. The vertebra tending to continuous slip, thus. The anterior and medial column should be repaired when lumbar spordylolisthesis was treated. Part II Three-dimensional finite element analysis of lumbar fusion. Objective Effects of three various fusion ways on fusion segments and adjacent segments were studied. The degenerative mechanism of lumbar fusion was investigated. Methods: The three-dimensional mechanical model of the intact lumbar spine was developed with 3-D finite element method. The stresses on the fusion segments and adjacent segments with three different types of spinal fusion (posterior, bilateral- lateral and interbody fusion) and various interbody implants, and preserving endplate were analysed by MSC/PATRAN software, and the stress was compared with that of the intact lumbar spine. Results: The stresses of the adjacent segme...