Biomechanical Test And Clinical Application Of The TSF For Thoracolumbar Fracture And Lumbar Spondylolisthesis

With the understanding of the spinal injury and its biomechanics , the pedicle screw technique has been going ahead rapidly, the appearance of varial pedicle reduction-fixation system raises the treatment result for spinal injury. The internal fixation device, such as Roy-camille, Steffee, APF, RF, SF , Dick and so on, promotes the development of spinal surgery. Meanwhile, the shortcoming of those pedicle short segment fixation is obvious, analysising the pathological mechanism of spinal injury and spondylolisthesis, we design a new internal device-TSF for unstable thoracolumbar fractures and lumbar spondylolisthesis , which is a simple convenient and effective instrumentation.1. Characteristics of TSFWe improve the design of pedicular screw ,rod and its connection . The cephalad part of rod entering the u-shaped hole of pedicular screw and pull-in screw are long ring-shaped and is connected with hole at the end of the rod by tapered nut. Thus it also can resist rotation, the tighting of nut of u-shaped screw may produce axial distaction or compression force , and can be used for all thoracolumbar spinal fracture . There is a reduction hole at the middle of the rod , it can also be used for lumbar spondlylolithesis by a pulling pedicular screw.2. Biomechanical Test of TSFEight spinal specimens were prepared. After the model of fracture and spodylolisthesis was established, we conduct biomechanical test onspecimens instrumented with Steffee, Dick , SF and record the result step by step.The results show : (1) the strength ,stiffiiess and stability of TSF are significantly better than the control group (P<0.01) . (2) The strength of spinal and stiffness were equal to SF. (3) The ultimate load was superior to conventional instrumentations .The TSF provides a rigid biomechanical fixation in thoracolumbar fracture and lumbar spondylolisthesis. 3. Clinical application of TSFBy now, 41 cases treated with TSF are followed up, including thoracolumbar fractures in 33 patients and spondylolisthesis in 8 patients. We measure the anterior and posterior vertebral body heights before and after operation in roentgenogramphy. The results show : After operation , there are 38 (90.91%) cases whose vertebral body heights come to normal levels ,there are 35 cases (84.85%) whose deformity is corrected. Thus, the TSF fixation has rigid , satisfied reduction . It is easier to be operated and has no complication of screw breakage , loosening , pullout etc.