| Background:Instrumented posterior spinal fusion is frequently used as a surgical treatment for spinal fractures. Transpedicular, short segment fixation became popular after the introduction of the transpedicular screws by Roy-Camille et al.The open posterior short segmental instrumentation can rectify the malformation and restore the stability of the spine. But it had additional surgical risks, such as elevated intraoperative blood loss and , more damages to the paraspinal musculatures, chronic back pain, prolonged hospital stay, the increased incidence of complication.With the development of minimally invasive spinal syrgery(MISS) in recent years, especially the combination of percutenous pedicle screw fixation and the computer assist surgery(CAS) have benn widely apply in the treatment of spinal fractures.The percutaneous pedicle screw fixation permits a safe application while preserving soft tissues without relevant blood loss and persisting sequelae, such as muscular denervation, atrophy, and pain.Traditional short-segment pedicle screw fixation involves pedicle screw placement only at the levels immediately adjacent to the fractured vertebra. While this procedure is popular, several researchers have reported unacceptably high failure rates with this technique.There were so many researchers suggest that the placement of pedicle screws into the fractured vertebra generates a segmental construct,which demonstrated improved biomechanical stability outcomes compared with a nonsegmental construct. The use of intermediate screws provides the advantage of a stiffer construct and therefore a lower probability for screw breakage, rod breakage and loss of reduction.We can also draw the conclution from our experience of using the technique. There was no literature about the clinical outcome of Sextant percutaneous pedicle screw fixation with 6 pedicles used in the treatment of thoracolumbar fractures.The purpose of this study was to evaluate the feasibility, safety and efficacy of the Sextant percutaneous pedicle screw fixation with 6 pedicles in the treatment of thoracolumbar fractures and the biomechanic of percutaneous pedicle screw fixation.Methods:1. Seventy-four consecutive non-randomized patients with type A thoracolumbar fractures,which had been stabilized posteriorly between December 2006 to September 2009, were examined retrospectively more than 9 months after surgery. 44 patients had been treated with conventionally open pedicle screw fixation(OPSF) in which 22 patients with and 22 patients without the fixation of the fractured vertebra, 29 patients had been treated with minimally invasive with Sextant percutaneous pedicle screw fixation (SPPSF) in which 17 patients with and 12 patients without the fixation of the fractured vertebra.As methods of evaluation, the incision size(IS), the amount of intraoperative blood loss(IBL), postoperative drainage(PD), surgical time(ST), postoperative hospital stay(PHS), blood transfusion(BT), tne situation of the pedicle screws in follow-up,the complications and the radiological assessment of the sagittal Cobb`s angle(SCA), vertebral body angle(VBA), anterior vertebral hight(AVH) and posterior vertebral hight(PVH) were made use of.2. Twelve fresh calf were divided randomly into OPSF group and SPPSF group, each were then fixed with 4 pedicles and 6 pedicles successively(with the fixation of fractured vertebra or not), each were made to compare the stability of transpedicular fixation with 4 or 6 pedicles by its axial compression, bending, rotation and axial extraction force.Results:1. There were significant differences in the incision size,surgical blood loss,surgical draining loss,surgical time,hospital stay postoperation, blood transfusion, the proportion of antalgic supplemented between OPSF group and SPPSF group(P<0.05).2. Each group compared to itself between preoperation and postoperation,the SCA, VBA, AVH and PVH were all significantly different(P<0.05).The OPSF group with 6 pedicles were significant differences in the AVH and PVH than the other three groups(P<0.05).In over 9 months follow-up, the two subgroups in OPSF group were no significant differences in the correction loss of the AVH(P>0.05).The SPPSF group with 4 pedicles was significant differences in the correction loss of the AVH than the other three groups (P<0.05). The OPSF group with 6 pedicles were significant differences in the VBA than the OPSF and SPPSF with 4 pedicles.3. The complication between OPSF and SPPSF were significant difference(P<0.05). The occurrence of screw breakage and screw loosening in SPPSF group with 4 pedicles were significant difference than the other three groups(P<0.05).4. All the four kind ways for transpedicular fixation can restore the stability of ingured thoracolumbar vertebra in axial compression, bending, rotation and axial extraction. Either OPSF or SPPSF group, there were statistical difference of spine stability capacity was found between 6 pedicle screws and 4 pedicle screws fixation.5. Take the intact model as the contral, the relative stability of the two subgroups in OPSF and the SPPSF with 6 pedicles is bigger, but the SPPSF with 4 pedicles is smaller.6. The ROMs and stiffness between OPSF with 4 pedicles and SPPSF with 4 pedicles were significant difference(P<0.05),the difference were not significant between OPSF with 6 pedicles and SPPSF with 6 pedicles.Conclusion: This result suggests the percutaneous pedicle screw fixation through the pedicle of fractured vertebra using Sextant system is a good minimally-invasive surgical therapeutic choice for patients with thoracolumbar fractures without neurodeficiency,but the Sextant percutaneous pedicle screw fixation group with 4 pedicles has a little insufficience in resuming the anterior height of the fractured vertebra compared with the open pedicle screw fixation group and the Sextant percutaneous pedicle screw fixation group with 6 pedicles. |
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