Effect Of Intervertebral Disc Injury On Clinical Outcomes After Posterior Surgery For AO Type B2 Thoracolumbar Fracture

Objective: To investigate the effect of intervertebral disc injury in AO type B2 thoracolumbar fracture on clinical outcomes after posterior fixation.Methods: 38 cases of AO type B2 thoracolumbar fracture which were treated with posterior fixation between October 2012 and June 2019,were retrospectively studied including the complication data of the patients.All patients underwent thoracolumbar anteroposterior and lateral radiographs,CT scan and MRI to determine the type of fracture and the severity of intervertebral disc injury before surgery.VAS score was used to assess the severity of the low back pain.ASIA scale was used to assess the neurologic function.Radiological measurement includes Cobb angle of the thoracolumbar fracture,local kyphosis of the fractured segment,anterior vertebral body height ratio of the fractured vertebral body.The degree of intervertebral disc injury was determined according to the classification of Sander et al.Statistical analysis was performed.Results: All patients were followed up for 30.2±20.1 months.There were 17 patients with disc injury.The mean preoperative Cobb angle was16.78°±9.08°,the mean postoperative Cobb angle was 5.76°±7.89°,however,the average Cobb angle at the last follow-up was 12.67°±12.79°.There was no significant difference in preoperative and postoperative Cobb angle,local kyphosis angle,and anterior vertebral body height between the intervertebral disc injury group and the non-intervertebral disc injury group.However,statistical differences were found(P<0.05)in mean preoperative and postoperative Cobb angle(18.59°±13.74°vs 8.16°±9.99°),the local kyphotic angle(11.88°±8.83°vs 6.55°±4.89°)and the anterior vertebral body height ratio(77.16%±18.07% vs 90.83%±9.26%).Implant failure occurred in 5 patients.The incidence of implant failure in the intervertebral disc injury group was significantly higher than that in the no intervertebral disc injury group(29.4% vs 0,p<0.05).Conclusion: Intervertebral disc injury is a common condition in AO type B2 thoracolumbar fracture,but it has often been overlooked.Disc injury at the fractured level increases the thoracolumbar instability,resulting in loss of kyphosis correction after posterior fixation,and even implant failure.For patients with AO B2 thoracolumbar fractures with intervertebral disc injury,interbody fusion is recommended to improve the efficacy of surgery and reduce the incidence of internal fixation failure.