Formative mechanism of intracanal fracture fragments in thoracolumbar burst fractures： a finite element study

Background Thoracolumbar burst fracture is a common clinical injury, and the fracture mechanism is still controversial. The aim of this research was to study the formation of intracanal fracture fragments in thoracolumbar burst fractures and to provide information for the prevention of thoracolumbar bursts fractures and reduction of damage to the nervous system. Methods A nonlinear three-dimensional finite element model of T11-L3 segments was established, and the injury processes of thoracolumbar bursts were simulated. The intact finite element model and the finite element model after the superior articular were impacted by 100 J of energy in different directions. The distribution and variation of stress in the superior posterior region of the L1 vertebral body were analyzed. Abaqus 6.9 explicit dynamic solver was used as finite element software in calculations. Results A three-dimensional nonlinear finite element model of the thoracolumbar spine was created. In the intact model, stress was concentrated in the superior posterior region of the L1 vertebral body. The stress peak was a maximum for the extension impact load and a minimum for the flexion impact load. The stress peak and contact force in the facet joint had close correlation with time. The stress peak disappeared after excision of the superior articular process. Conclusions The three-dimensional nonlinear finite element model was suitable for dynamic analysis. The contact force in the facet joint, which can be transferred to the superior posterior vertebral body, may explain the spinal canal fragment in thoracolumbar burst fractures.

Early posterior spinal canal decompression and circumferential reconstruction of rotationally unstable thoracolumbar burst fractures with neurological deficit

Background Among the various treatments of neurologically involved unstable thoracolumbar burst fractures,the combination of anterior and posterior instrumentation provides the most stable reconstruction.However,the use of both approaches on a trauma patient may increase the morbidity.This study is a retrospective matched cohort study to evaluate the advantages of a single stage posterior approach for spinal canal decompression in combination with circumferential reconstruction by comparing the clinical and radiographic results.Methods From March 2005 to September 2009,patients with matched type spinal fracture,ages at surgery,and involved levels in our institute underwent either a single stage posterior approach （group one,n=12） or traditional combined approach （group two,n=14） for spinal canal decompression and circumferential reconstruction were reviewed.Pre-and post-operative X-ray films were reviewed and changes in Cobb angle of thoracolumbar spine were documented.Intra-operative,post-operative,and general complications were registered.Results The mean follow-up was （27.7±9.6） months （range,14 to 56 months） in group one and （29.2±7.4） months （range,20 to 60 months） in group two （P 〉0.05）.The mean operation time was 214 minutes （range,186-327 minutes） in group one and 284 minutes （range,219-423 minutes） in group two （P 〈0.05）.The average volume of intraoperative blood loss was 1856 ml （range,1250-3480 ml） in group one and 2453 ml （range,1600-3680 ml） in group two （P 〈0.05）.There was no statistical difference between the groups one and two in average vertebral body height loss at the injured level and the average Cobb angle in sagittal plane before and immediately after surgery.Postoperatively,there was an epidural hematoma in one patient in group one and two patients in group two.Bony union after stabilization was obtained in all patients,without loosening or breakage of screws.Loss of correction （5°） was seen in 1 patient in group one at the 6th month owing to the subsidence of the Titanium mesh cages into the vertebra.In group two,totally four patients suffered respiratory-related complication,including pneumonia in two,severe atelectasis in one and pleural effusions in one.Importantly,there were no intraoperative or postoperative deaths in any group.All patients with incomplete neurologic deficits improved at least 1 Frankel grade.Conclusion Single-stage posterior vertebra resection in combination with circumferential reconstruction is a new option to manage severe thoracolumbar burst fractures.

Biomechanical effects of pedicle screw adjustments on the thoracolumbar burst fractures

Background Posterior pedicle screw device is widely used in treatment of thoracolumbar burst fractures. As the clinical operation is not based upon quantitative data of adjustments, the results are not optimal. At present, no study has assessed the associations between the device adjustments and the restoration of stiffness. We investigated the biomechanical effects that adjustments of a pedicle screw device had on the burst fracture, and explored an optimal adjustment. Methods Burst fractures were produced at L1 vertebra in 24 fresh calf spines （T12-L3）. The specimens were divided into four groups at random. Pedicle screw devices were attached to T13 and L2. Four device adjustments, consisting of distraction and extension, were applied. Adjustment 1 was pure 6~ extension, adjustment 2 was pure 5 mm distraction, adjustment 3 was 6~ extension followed by 5 mm distraction, and adjustment 4 was 5 mm distraction followed by 6~ extension. The effect of each adjustment on the stiffness restoration, anatomical reduction, and neural decompression for the burst fractures was analyzed and evaluated. Results Pure extension （Group 1） produced the closest segment height and the least restoration of the canal to the intact. Pure distraction （Group 2） restored stiffness most, but with only 60% stiffness of the intact value, and lost the segmental angle most to the intact. The combination of extension-distraction （Group 3 and Group 4） produced the maximum reduction of the anatomy and restoration of the canal in the burst fracture, and the least stiffness restoration. The sequence of extension and distraction did not affect stiffness restoration, anatomical reduction, and neural decompression. Conclusions The device adjustments affected stiffness restoration, anatomical reduction, and neural decompression. The combined extension-distraction adjustment may be the most suitable considering the anatomical reduction and neural decompression, but the stiffness decreased the most; it should be considered to reconstruct L1 vertebra.

Titanium mesh fusion device in the treatment of thoracolumbar burst fracture

Thoracolumbar burst fracture, a common condition in clinic, often leads to severe spinal instability and neurologic deficit. In most cases, the compression that caused by backward protrusion of the fracture fragments to the spinal cord, makes complete decompression difficult through a posterior approach. Here, we reviewed the clinical records of 22 patients with thoracolumbar burst fracture treated by anterior corpectomy, decompression of the spinal cord, and implantation of titanium mesh cage.

KumaFix fixation for thoracolumbar burst fractures： a prospective study on selective consecutive patients

Background Short-segment U-shaped pedicle screw fixation has been widely used to treat thoracolumbar burst fracture.Some studies have reported the disadvantages of traditional U-shaped pedicle screw,which included a relatively high rate of adjacent segment degeneration and screw failure,including screw pullout and breakage.The purpose of this study was to assess the efficacy of open reduction and fixation using KumaFix fixation system in treatment of thoracolumbar burst fractures.Methods From June 2011 to June 2012,45 consecutive patients with thoracolumbar burst fractures were enrolled.They were randomly assigned to treatment with KumaFix （the treatment group,n=23） or traditional U-shaped pedicle screw （the control group,n=22）.The patients were followed up postoperatively and were assessed with regard to radiologic and clinical outcomes.Radiologic outcomes were assessed mainly on the basis of Cobb angle and vertebral wedge angle.Clinical outcomes were evaluated mainly with use of Visual Analog Scale （VAS） for pain and the Oswestry Disability Index （ODI） Questionnaire.Results All patients were followed up from 9 to 22 months.There were no significant differences between the two groups with regard to preoperative indices.The operation time in the treatment group was significantly lower than that in the control group.Preoperative Cobb angles and vertebral wedge angles in two groups were significantly decreased after surgery,and these have been well maintained at the last follow-up with mild correction losses.The results of clinical outcome showed lower VAS and ODI scores in two groups compared with those preoperative,and the treatment group had greater improvement on the ODI compared with the control group at the last follow-up.Conclusions Compared with traditional U-shaped pedicle screw,KumaFix fixation system can achieve gradual,controlled reduction,provide enough space for bone implantation,and avoid acceleration of adjacent segment degeneration.It is an effective and reliable technique to treat thoracolumbar burst fractures.

Biocompatibility of polyetheretherketone for the treatment of orbital bone defects

AIM: To investigate the biocompatibility and therapeutic effects of polyetheretherketone(PEEK) on recovery of a rabbit orbital defect.METHODS: Totally 16 New Zealand rabbits were used to establish an orbital bone defect model and then randomly divided into two groups. PEEK was implanted in the experimental group. The control group was blank, and no substance was implanted. The model rabbits were sacrificed at 4 and 8 wk, and examined by general observations, histology, electron microscopy, Western blotting, and realtime polymerase chain reaction.RESULTS: No infection or rejection occurred after PEEK implantation, and biocompatibility was good. The relative expression of vascular endothelial growth factor(VEGF) protein in the experimental group was significantly higher than that in the control group postoperatively(P<0.05). Bone defect repair in the experimental group was significantly better than that in the control group in the same period and some osteogenesis was observed.CONCLUSION: PEEK has good biocompatibility and efficacy for the treatment of orbital bone defects in a rabbit model.

Lumbar Artery Pseudo-Aneurysm after Spinal Trauma and Transpedicular Fixation: A Case Report

Introduction: A case of lumbar artery pseudo-aneurysm after surgery for lumbar vertebra burst fracture is presented. Only two cases secondary to spinal trauma and revealed after surgery have been described in the literature. A review of literature was conducted and a possible relationship with burst fracture or reduction maneuvers was discussed. Case Presentation: Here, we report a post traumatic lumbar burst facture with incomplete motor deficit of lower limbs after a fall. Surgical reduction and stabilization via posterior approach were performed. Post-operatively, a hemorrhage through surgical wound had been noticed. Pseudo-aneurysm of the lumbar artery at L3 level was diagnosed and embolisation was performed. Conclusion: This is a rare case of pseudo-aneurysm occurring in the setting of surgical stabilisation after a trauma. It was revealed by a hemorrhage discovered as a late complication. We should be aware of such potential complication as a delayed post surgery event in order to adapt the care.