Long-term Outcome Of Thoracolumbar Burst Fractures After Posterior Instrumentation And Transpedicular Intracorporeal Grafting

Thoracolumbar burst fracture with spinal cord injury is a kind of common clinical spinal trauma. Its treatment is always focused by the spine surgeons because of possibly permanent neurological injury. Through decades efforts, with the developing of new techniques and concepts, the treatment for spinal fractures have been developed quickly. But there are still much controversy and hot issues to be clarified. Short segment fixation can give spine more stability, but it is difficult to prevent failure of internal fixation. Transpedicular intracorporeal grafting as a method of consolidating anterior and middle column of the injuried vertebral body can prevent early failure of fixation and late loss of correction, but it is controversial about the clinical effect. It is also controversial about the effect of spinal canal decompression to release bone block and recover nerve function. It is diffcult to balance nerve decompression and spinal stability. Short segment fixation is a good method to correct spinal deformity, but the correction can be lost after removal of the implants. To prevent the loss, we should study the cause of the loss and relevant factors. It is very meaningful if the spinal movement could be preserved after the removal of fixation instruments. This study is a long-term follow-up study retrospectively, to analyse these issues above-mentioned.Part one:Imaging and clinical evaluation of long-term outcome of surgical treatment for thoracolumbar burst fracturesObjective:To investigate retrospectively clinical results of treatment to thoracolumbar burst fractures with spinal canal decompression,transpedicular intracorporeal grafting and short-segment fixation. To clarify the outcome of transpedicular intracorporeal grafting and the effect to prevent early implant failure and late loss of correction.Methods:Forty-six patients who had undergone transpedicular intracorporeal grafting and short-segment fixation for thoracolumbar burst fractures were investigated retrospectively. The clinical outcome and complication were analysed. Clinical results were also evaluated by imaging observation. Eighteen patients who had underdone posterolateral bong grafting were compared through imaging data analysis.Results:Vertebral canal volume recovered to close to or bigger than normal canal after direct canal decompression with different methods. The decompressed canal remodeled totally for about one year. The grafted bone in vertebral body healed with the surrounding normal bone. The fusion process was typical creeping substitution. One patient who was Grade A (ASIA classification) preoperation recovered to Grade B. Other patients who were Grade B,C and D all recovered to some degree. There were significantly different in. sensomotor scores. There was no any cases whose implants were pullout or broken and whose neurological function was impaired irreversibly. The average Cobb angle changed from 21.29°preoperation to 4.54°postoperation with an average loss of 7.07°after implants removal. The average vertebral wedge angle changed from 27.16°preoperation to 7.02°postoperation with an average loss of 1.00°at final follow-up. The average ratio between anterior and posterior vertebral height changed from 53.30% preoperation to 92.32% postoperation with an average loss of 1.06% at final follow-up. Compared transpedicular intracorporeal grafting and posterolateral bone grafting, anterior was better than posterior in correction of vertebral wedge angle and ratio between anterior and posterior vertebral height. There was no correlation between the loss of Cobb angle and the degree of pain.Conclusions:1,Direct canal decompression with different method can preserve spinal cord residual function and improve recovery of neurological function of spinal cord incomplete injuries. 2,"Support" reduction by transpedicular intracorporeal grafting can recover vertebral wedge angle and height of anterior column, especial for the fracture of upper endplate. The grafted bone in vertebral body can heal with surrounding normal bone and increase local bone quantity and strength, so as to preserve height of anterior column, recover the morphology of fractured vertebral body and prevent early failure of implants.3,Transpedicular intracorporeal grafting can not stop the loss of correction after implant removal. Compared with posterolateral bone grafting, it improve injuried vertebral body morphology recovery early much better and reduce the late loss of correction after implant removal. We recommend double sides bone grafting to treat thoracolumbar fractures, so as to expand reduction area and increase grafting bone quantity.Part two:Analysis to related factors to the loss of Cobb angle and study to long-term outcome of spinal motion function.Objective:To analyse the correlation between the loss of Cobb angle and vertebral wedge angle,ratio between anterior and posterior vertebral height,upper and lower intervertebral angle and loss rate of them after implant removal. To investigate the preservation of the motion function of intervertebral space of the fixed segment after implant removal.Methods:According to the imaging data of Part One, multiple linear regression analysis was performed between Cobb angle,vertebral wedge angle ratio between anterior and posterior vertebral height,upper and lower intervertebral angle and loss rate of them after implant removal. Hyperextension and hyperflexion dynamic X-ray were performed to the 46 patients who had been underdone transpedicular intracorporeal grafting when the implants removal to investigate the spinal motion state.Results:The loss of upper and lower intervertebral angle was 81% of the loss of Cobb angle. Result of multiple linear regression analysis between loss of correction and indexes preoperation shows positive correlation between vertebral wedge angles preoperation and the loss of Cobb angles. Result of stepwise regression analysis between loss of correction and the loss rate of the indexes after implants removal shows positive correlation between the loss of Upper intervertebral angles and of Cobb angles. Upper and lower intervertebral space both preserved motion function after the implants removal. Average range of motion of flexion and extension of upper intervertebral angle was 2.2±1.1°, lower intervertebral angle 3.8±1.5°.Conclusions:1,The loss of Cobb angles in patients who were suffered thoracolumbar burst fracture mainly attribute to the loss of upper and lower intervertebral angles.2,There is positive correlation between the loss of correction and vertebral wedge angle preoperatiom,height of anterior column of vertebral body. In these factors for loss of Cobb angles, only the loss of upper intervertebral angles has positive correlation with the loss of Cobb angles.3,Transpedicular intracorporeal grafting without any kind of fusion could preserve motion function of the fixed segment, generally 50% range of the normal. So this technique could be as a kind of non-fusion technique. But it need further long-term clinical observation to clarify how much benefit the motion function preserved could bring to motion function and subjective feeling of the patients.