Finite Element Analysis And Clinical Study On The Effect Of Cross-link In The Treatment Of Thoracolumbar Fractures With Different Internal Fixation Methods

Background and ObjectivePosterior instrumentation is a common fixation method used to treat thoracolumbar burst fractures.However,the role of cross-link configuration in improving fixation stability in these fractures has not been established.Thoracolumbar fractures with neurological deficits is a common trauma and it usually undergoes surgical intervention.The traditional open surgery can achieve satisfied results,but the main disadvantage is approach-related complications.However,there is no study focused on the treatment of thoracolumbar fractures with neurological deficits by minimally invasive techniques through posterior approach.The purpose of this study is to evaluate the surgical results of minimally invasive posterior decompression combined with percutaneous pedicle screw fixation surgery(MIS)compared to traditional posterior open surgery(OS)for the treatment of thoracolumbar fractures with neurological deficits.Methods and ResultsA finite element model of T9-L3 was used to investigate the biomechanical behavior of short and long segmental spine pedicle screw fixation with cross-links to treat a T12 vertebra burst fracture.Three types of fixation with cross-link configurations with an applied moment of 10 n.m and 150 N axial force were evaluated.From December 2011 to June 2014,a total of fifty-six cases of thoracolumbar fractures with neurological deficits were included in MIS group and OS group.The patients in MIS group underwent minimally invasive posterior decompression combined with percutaneous pedicle screw fixation surgery,whereas the patients in OS group received traditional posterior open surgery.The long construct was stiffer than the short construct irrespective of whether the cross-links were used.The construct with cross-link was stiffer than the construct without cross-link at the same segment.However,increasing the cross-link in the same segment also adds the maximum stress value of the screw and rod.With the increase of the length of fixed segment,the stability of the device is also enhanced.MIS group was superior to the OS group in incision length,blood loss,postoperative drainage volume,hospitalization days,blood transfusion rate and analgesic use rate.Compared with the preoperative,the postoperative radiographic parameters were significantly improved within two groups.However,there were no differences in these data between two groups.The mean VAS and JOA scores of final follow-up in MIS group were superior than that in OS group.The majority of patients with Frankel grade were obtained at least one grade improvement at final follow-up.There was no statistical differences in the complication rate between the two groups.ConclusionThe cross-link can increased the stability of the internal fixation device,especially in the axial rotation.In clinic,for the existence of spinal instability of severe thoracolumbar burst fracture,the use of long segmental fixation to rebuild the stability of the spine was stronger than that of short segment fixation.Compared with OS group,the MIS group has achieved the same therapeutic effect.Meanwhile,minimally invasive surgery greatly reduced the approach-related caused by traditional surgical trauma to patients.However it is also faced with some shortages,such as the larger dose radiation exposure and the longer learning curve.