Objective To study the effect of different rod curvature on the postoperative stability and stress of thoracolumbar junction fracture using the finite element simulation.Methods (1) Thoracolumbar finite element model of T11 to L1 from three-dimensional CT data of a 30-year-old healthy male volunteer was established,including the assignment of cortical bone,cancellous bone,disc,ligaments and facet joints.On this basis,the T12fracture model was also established.T11 to L1 bilateral pedicle screw fixation was loaded,and the rod connection was divided into straight rod group and pre-bended rod group (lordotic 15°-25°) according to angle of the rod.A 400 N stress was loaded on the top of the upper endplate of T11 to simulate the upper part body gravity,while applying a 10 N · m torque to generate flexion and extension,lateral flexion and rotation.Stress distribution of different methods of pre-bending for thoracolumbar fractures after reduction was compared.(2) A retrospective cohort analysis was made on 56 cases of thoracolumbar fractures surgically treated from July 2012 to July 2016,including 31 cases in straight rod group and 25 cases in pre-bended rod group.Two groups were compared in angle between adjacent level before operation,after operation and at final follow-up.Results (1) In flexion,extension,lateral bending and rotation,both rod bending methods effectively controlled the thoracolumbar junction displacement.The peak stress of connecting rod (151,315,369,377 MPa respectively) in pre-bended rod group was lower than that in straight rod group (110,239,281,189 MPa respectively) (P ＜ 0.05),and straight rod group appeared relatively obvious stress concentration.(2) Mean follow-up time was 21.4 months (range,4-33 months).Preoperative kyphosis angle was (21.7 ± 7.4)°in straight rod group and (20.3 ± 6.8)° in pre-bended rod group (P ＞ 0.05).Postoperative lordosis angle in straight rod group was (3.3 ± 1.2) °versus (8.3 ± 2.8) ° in pre-bended rod group (P ＜ 0.05).At the final follow-up,the lordosis angle in straight rod group was reduced by (8.7 ± 2.3) ° versus (3.9 ± 1.7)°in pre-bended rod group (P ＜0.05).Implant failure was seen in 3 cases in straight rod group,but there was no implant failure in pre-bended rod group.Conclusion Pre-bended (lordotic 15°-25°) and pre-loaded rods used in internal fixation of thoracolumbar fractures may reduce the stress of rods,decrease the incidence of implant failure and facilitate the recovery of spine stability.

Objective To compare the feasibility and efficacy of intervertebral wedge osteotomy and pedicle subtraction osteotomy (PSO),vertebral column resection (VCR),Smith-Petersen osteotomy (SPO) for the treatment of severe kyphosis and scoliosis.Methods The data of 38 cases of severe kyphosis and kyphoscoliosis were retrospectively analyzed from January 2010 to February 2016,including 22 males and 16 females.According to the osteotomy mode,PSO,SPO,VCR and intervertebral disc wedge osteotomy were used to collect the average number of fixed phases,volume of bleeding,length of stay,length of hospital stay,improvement of main cobb angle,improvement of ODI score,and Frankel classification to evaluate the efficacy.Results There were no significant differences in the overall operative time between the four groups.The average number of fixation in 18 patients with SPO was (9.4±3.9) segments,the blood loss was (3 000±410) ml,the average Cobb angle was improved by 55.3％± 9.5％,the average postoperative hospitalization was (14.6±4.9) days,the improvement rate of ODI was 42.1％±7.4％,all the patients were improved to Frankel E;The average number of fixation in 5 patients with PSO was (7.6± 1.5) segments,the blood loss was (4 360± 1 161) ml,the average Cobb angle was improved by 58.9％ ± 15.1％,the average postoperative hospitalization was (18.2±7.0) days,the improvement rate of ODI was 41.3％±9.6％.One Frankel C patient was improved to Frankel D,others remained to be Frankel E as the same as pre-operation;The average number of fixation in 4 patients with VCR was (6.2±2.6) segments,the blood loss was (3 750+ 1 848) ml,the average Cobb angle was improved by 83.9％± 10.9％,the average postoperative hospitalization was (21±7.2) days,the improvement rate of ODI was 39.6％± 18.1％.Three Frankel D patients were improved to Frankel E and one Frankel C patient was improved to Frankel D;The average number of fixation in 11 patients with IWO was (7.1 ± 2.7) segments,the blood loss was (2855±1046) ml,the average Cobb angle was improved by 59.6％±22.05％,the average postoperative hospitalization was (13.5±2.7) days,the improvement rate of ODI was 51.3％±8.3％.One Frankel C patient was improved to Frankel D,eight Frankel D patients were improved to Frankel E,other patients remained to be Frankel E;The mean follow-up time was 25.2 months in 11 patients underwent intervertebral wedge osteotomy.All the patients had successful spinal fusion and no failure of internal fixation.Conclusion Intervertebral wedge osteotomy for the treatment of scoliosis and kyphosis could reduce surgical injury to obtain good biomechanics and surgical result.

Objective:To explore the difference and clinical significance of paraspinal muscle degeneration between single-segment degenerative lumbar spondylolisthesis and degenerative lumbar spinal stenosis.Methods:From January 2014 to October 2020, a retrospective analysis of 30 patientswere diagnosed with L 4,5 degenerative lumbar spondylolisthesis, aged 61.63±8.42 years old (range 44 to 82 years old), body mass index 24.07±3.17 kg/m 2 and 30 patientswere diagnosed with L 4,5 degenerative lumbar spinal stenosis, aged 59.67±12.89 years old (range 31 to 80 years old), body mass index 25.29±3.48kg/m 2, both of them went on surgery in department of spine surgery, shengjing hospital, China Medical University.30 healthy people were selected from outpatient physical examination in the control group, aged 58.33±7.36 years old (range 52 to 83 years old), body mass index 25.72±2.58 kg/m 2. These three groups were all male. Select all patients with L 3,4, L 4,5 and L 5S 1 disc level axial MRI images, and use the deep learning automatic segmentation measurement system developed by our hospital and Shenyang Institute of Automation Chinese Academy of Sciences to measure multifidus muscle cross sectional area (MMCSA), erector spinae cross sectional area (ESCSA), multifidus muscle fatty infiltration rate (MMFIR) and erector spinae fatty infiltration rate (ESFIR). One-way ANOVA was used to test the imaging parameters of multifidus and erector spinae of the three groups, and LSD- t test was used to compare the imaging parameters in each segment of paraspinal muscles. Results:The gender of three groups were male, there was no significant difference in age ( H=5.303, P>0.05), and there was no significant difference in body mass index ( F=2.267, P>0.05). Multifidus muscle cross-sectional area in L 3,4: degenerative lumbar spondylolisthesis groupincreased 189.11 mm 2 compared with degenerative lumbar spinal stenosis group ( P=0.010). Multifidus muscle cross-sectional area in L 4,5: compared with healthy people group, degenerative lumbar spondylolisthesis group decreased 205.52 mm 2 ( P=0.002), while degenerative lumbar spinal stenosis group decreased 184.14 mm 2 ( P=0.006). Multifidus muscle cross-sectional area in L 5S 1: compared with degenerative lumbar spinal stenosis group, degenerative lumbar spondylolisthesis group decreased 174.93 mm 2 ( P=0.018); compared with healthy people group, degenerative lumbar spondylolisthesis group decreased 406.06 mm 2 ( P<0.001), while degenerative lumbar spinal stenosis group decreased 231.13 mm 2 ( P=0.002). Erector spinae cross sectional area in L 4,5: compared with healthy people group, degenerative lumbar spinal stenosis group decreased 398.70 mm 2 ( P=0.006). Erector spinae cross sectional area in L 5S 1: compared with degenerative lumbar spinal stenosis group, degenerative lumbar spondylolisthesis group decreased 500.02 mm 2 ( P<0.001); compared with healthy people group, degenerative lumbar spinal stenosis group decreased 455.37 mm 2 ( P<0.001). Compared with healthy group, the multifidus muscle fatty infiltration rate of degenerative lumbar spondylolisthesis group in L 3,4 increased 4.96% ( P=0.001). Compared with degenerative lumbar spinal stenosis group, the erector spinae fatty infiltration rate of degenerative lumbar spondylolisthesis group in L 5S 1 decreased 5.41% ( P=0.004). Compared with healthy group, the erector spinae fatty infiltration rate of degenerative lumbarspinal stenosis group in L 5S 1 increased 5.02% ( P=0.008) . Conclusion:Paraspinal muscle cross sectional area of each segment in degenerative lumbar spondylolisthesis group and degenerative lumbar spinal stenosis group decreased in different degrees. In degenerative lumbar spondylolisthesis group, the degree of multifidus muscle fat infiltration was more significant, while indegenerative lumbar spinal stenosis group,the degree of erector spinal fat infiltration was higher.

Objective:To investigate the safety and effectiveness of anterior-curved rod and precompressive reduction and fixation from posterior approach for unstable burst fractures in thoracolumbar junction.Methods:From July 2017 to December 2019, according to the classification standard of AO Spine-Spine Trauma Classification System of 2019, 33 patients with type A3 thoracolumbar junction fractures with kyphosis angle > 20° and Asia Grade E were treated with anterior-curved rod and precompressive reduction and fixation from posterior approach. All the patients had single vertebral fractures. Three groups of screws were used to fix the injured vertebrae and the upper and lower vertebrae adjacent to the injured vertebrae, and the injured vertebrae were reduced. No bone graftor fusion was performed during the operation. The main outcome measures were the height of middle column of the injured vertebrae, the invaded cross-area of the injured vertebral canal, the encroachment rate of the injured vertebral canal, the Cobb angle of kyphosis, and visual analogue scale (VAS) and Oswestry disability index (ODI) before and after operation and at the last follow-up. All these data were analyzed statistically by t-test. Results:The operation was successfully performed in all 33 patients. 198 pedicle screws were implanted. The accuracy ofthe screws by CT evaluation was 98.8%. The average operation time was 89.8±20.4 min, and the average intraoperative blood loss was 170±53.7 ml. The height of the middle column was improved from 17.32±2.02 mm preoperatively to 21.41±3.68 mm postoperatively, and the invaded cross-area of the injured vertebral canal was improved from 101.3 ± 21.67mm2 before operation to 68.5±18.2 mm 2 after operation. The encroachment rate of the injured vertebral canal was improved from 47.66% ± 19.83% before operation to 19.61%±5.75% after operation; Cobb angle of kyphosis was improved from 26.33°±5.68° before operation to 3.13°±1.25° after operation; VAS score was improved from 6.42±1.25 before operation to 1.85±0.71 after operation, and 1.69±1.21 at the last follow-up; ODI was improved from 43.03%±3.46% before operation to 21.88%±4.22% after operation and 6.33%±2.31% at the last follow-up. There were statistically significant differences in the observative indexes after operation and at the last follow-up compared with those before the operation (P < 0.05). Conclusion:The technique of anterior-curved rod and precompressive reduction and fixation from posterior approach can safely and effectively reduce both the invading bone mass within the injured vertebral canal and the kyphosis angle.