Quantitative Study Of Indirect Reduction Of Thoracolumbar Burst Fractures By Longitudinal Distraction Under Three-dimensional Monitoring During O-arm Machine Surgery

Objective:To analyze and measure the related parameters of the protruding bone fragment with the spinal canal and the vertebral body In the three-dimensional monitoring of the O-arm machine and investigate the possibility and influencing factors of indirect reduction performed by the longitudinal distraction of the posterior longitudinal ligament,thus providing a reference for our surgical plan.Methods:We retrospectively analyzed 35 cases of thoracolumbar burst fractures who underwent three-dimensional monitoring of the O-arm machine in our hospital from January 2015 to December 2017.There were 24 patients with nerve injury and 11 patients not.Through the preoperative CT three-dimensional reconstruction,the position of the protruding bone fragment after burst fracture was determined,the height and width of the posterior block,the mid-sagittal canal diameter of the injured spinal canal and the local sagittal Cobb angle were measured.Besides,we calculated the compression ratio of the mid-sagittal diameter of the vertebral canal and the compression ratio of the cross-sectional area of the spinal canal.By means of posture reduction and longitudinal distraction of the posterior longitudinal ligament,the degree of bone reduction was evaluated by intraoperative O-arm machine,while taking the reduction more than 50% of the fracture block as the standard of satisfactory reduction,the patients were divided into satisfactory reduction group and unsatisfactory group,and the unsatisfactory group was treated with intraoperative laminectomy and decompression by direct reduction.The relative data of the two groups were compared and analyzed to investigate the possibility and influencing factors of indirect reduction.Results:In the comparison between the satisfactory group and the unsatisfactory group,there were significant difference in the height of the posterior bony block(10.31 ± 2.35)mm,the width(10.64 ± 2.42)mm in the satisfactory group,and the height of the posterior bony block(14.17 ± 1.15)mm,the width(19.01 ±2.63)mm in the unsatisfactory group(P<0.05).There were significant difference in the mid-sagittal canal diameter of the injured spinal canal(10.75 ± 1.11)mm in the satisfactory group and(7.40 ± 1.71)mm in the unsatisfactory group(P<0.05).The compression ratio of the mid-sagittal canal diameter of the injured spinal canal and the compression ratio of the cross-sectional area of the spinal canal were calculated in both groups.The compression ratio of the mid-sagittal canal diameter of the injured spinal canal was calculated(37.98% ±5.75%)and the compression ratio of the cross-sectional area of the spinal canal(27.10% ± 7.62%)in the satisfactory group,and the compression ratio of the mid-sagittal canal diameter(55.54%±11.22%),the compression ratio of the cross-sectional area of the spinal canal(45.51%±7.30%)in the unsatisfactory group were statistically significant(P<0.05).There was no significant difference in the local sagittal Cobb angle(P>0.05)between two groups.There was no evidence of bone turnover in the satisfactory group.In the unsatisfied group,2 cases of bone turnover were found.The average operative time and intraoperative blood loss in the satisfactory group were(105 ± 5)min and(140 ± 5)ml,respectively,whereas those in the unsatisfactory group were(155 ± 7)min and(360 ± 6)ml.The difference was statistically significant(P<0.05).Compared with the preoperative recovery of neurological function in both groups,the vast majority of ASIA grades were improved by at least one grade,and neurological function improved significantly.Comparing the two groups before and after reduction,the height and width of the posterior block,the mid-sagittal canal diameter of the injured spinal canal,the local sagittal Cobb angle,the compression ratio of the mid-sagittal diameter of the vertebral canal and the compression ratio of the cross-sectional area of the spinal canal were significantly improved postoperatively(P<0.05).Conclusion:The indirect reduction of the thoracolumbar burst fracture through the posterior longitudinal ligamentotaxis depends on the integrity and continuity of the posterior longitudinal ligament.The posterior longitudinal ligament rupture and the posterior bone fragment reverse can not achieve the purpose of repositioning the protruding bone fragment by indirect reduction.In thoracolumbar burst fractures,the height and width of the posterior bone,the presence or absence of inversion of the posterior bone,the mid-sagittal canal diameter of the injured vertebral canal,the compression ratio of the mid-sagittal canal diameter of the injured vertebral canal,and the compression ratio of the cross-sectional area of the spinal canal are significantly important factors affecting the indirect reduction of the protruding bone.A satisfactory indirect reduction can be obtained when the compression ratio of the mid-sagittal canal and the cross-sectional area of the spinal canal are less than 45%(37.98% ± 5.75% and 27.10% ± 7.62% in this group respectively),while the compression ratio of the mid-sagittal canal and the cross-sectional area of the spinal canal are more than 45%,or when there is a simultaneous bone turnover(55.54% ± 11.22% and 45.51% ± 7.30% in this group respectively),then indirect reduction is difficult to achieve satisfactory results,and it often needs laminectomy and decompression by direct reduction.This conclusion can provide guidance for surgeons to formulate reasonable surgical plans before surgery.The three-dimensional monitoring of the O-arm machine can determine the reduction of the protruding bone fragment.Through the intraoperative three-dimensional reconstruction,the specific location of the fracture block and the effect of reduction can be definitely obtained.