Objective:To propose a monosegment thoracic and lumbar fracture dislocation (mTLFD) classification, and to evaluate its reliability and clinical application.Methods:All of 298 cases of thoracic and lumbar fracture dislocation who received surgical management in our hospital from January 2014 to December 2019 were retrospectively analyzed. 123 cases were included in the study according to inclusion and exclusion criteria. mTLFD classification was proposed based on the imaging characteristics: type I (intervertebral disc injury mainly) and type II (vertebral burst fracture mainly). The type II was classified based on distribution of injury segment: type IIa (T 11 and above) and Ttype IIb (below T 11). Six spinal surgeons (3 residents, 3 associate chief physicians) were selected to classify the 123 cases according to preoperative imaging data, and to perform reliability test of each type. The repeatability and reliability of the classification were evaluated by ICC index. Different management strategies were performedf or each type: type I was managed with posterior decompression interbody fusion and internal fixation; type IIa underwent posterior decompression and fixation, subtotal vertebral resection and fusion was performed if bony compromise was still present through intra-operative exploration. Type IIb underwent posterior decompression, posterolateral fusion and internal fixation on the first stage, while anterior subtotal vertebral resection and reconstruction was performed on the second stage if the bony compromise was still present based on post-operative CT examination. The American Spinal Injury Association (ASIA) grading of all patients was recorded, and the visual analogue scale (VAS), Oswetry disability Iindex (ODI) and local Cobb angle of each type was compared between pre-operation and final follow-up. Results:The average follow-up time of all patients was 10.4±1.8 months. The average repeatability and reliability ICC index of mTLFD of 3 residents and 3 deputy chief physicians were 0.926 and 0.964, respectively, and 0.746 and 0.907, respectively. The reliability ICC index of type I, type IIa and type IIb was 0.918, 0.947 and 0.962, respectively, and the repeatability ICC index was 0.930, 0.940 and 0.966, respectively. The neurological function recovery was obtained in 56 patients. The preoperative VAS of type I, type IIa and type IIb were 8.5±1.0, 8.4±1.0 and 8.3±0.9, and 2.0±1.1, 1.8±1.0 and 1.8±0.9 at the final follow-up (all P<0.001). The ODI of type I, type IIa and type IIb were 97.0%±2.1%, 97.1%±1.9% and 97.3%±2.1% before surgery, and 29.5%±6.8%, 27.0%±6.0% and 29.0%±6.7% at the final follow-up (all P<0.001). The local Cobb angles of type I, type IIa and type IIb were 20.9°±7.1°, 29.0°±9.1° and 26.4°±6.9° before surgery, and 12.5°±5.4°, 18.0°±9.1° and 13.1°±5.1° at the final follow-up (all P<0.001). Conclusion:The mTLFD classification proposed in this study has strong repeatability and reliability, and management strategy of each type have achieved satisfactory clinical efficacy, indicating that the classification has certain significance for management of thoracic and lumbar spine fracture dislocation.

Objective To reduce the risk of cervical spinal cord injury,the most medial point of the cervical intervertebral disc that the posterior percutaneous endoscopic sheath could reach was evaluated.And that could help to determine the indication of posterior percutaneous endoscopic cervical discectomy for cervical intervertebral disc herniation.Methods Cervical MRI images for 50 randomly selected patients,21 males and 29 females with ages from 20 to 60(average 33.5± 10.03 years),were analysed.All 50 patients underwent MRI examination at our institution between January 2014 and December 2017.As 50％ of the zygapophyseal joint was preserved,on the cross-section T2-weighted MRI images,when the sheath just touched the spinal cord,the intersection point of the medial wall of sheath and cervical spinal cord (Point L) was the most medial point of the posterior percutaneous endoscopy could get.The distance between Point L and the line through and tangent to the most lateral point of cervical disc border was the length of the line section DL.The distance between the middle sagittal line of the cervical disc and the line through and tangent to the most lateral point of cervical disc border was the length of the line section D.D1/D was the most medial distance ratio of the posterior percutaneous endoscopic cervical discectomy when 50％ of the lateral zygapophyseal joint was preserved.In the same way,D'1/D was the most medial distance ratio of the posterior percutaneous endoscopic cervical discectomy when 75％ of the lateral zygapophyseal joint was preserved.Results When 50％ of the lateral zygapophyseal joint was preserved,the upper limit of 95％ confidence intervals of the most medial distance ratio that the posterior percutaneous endoscopy could get were 78％,76％,81％,93％ in C3,4,C4,5,C5,6,C6,7 respectively.This meant that the most medial distance the posterior percutaneous endoscopy could get were the 78％,76％,81％,0.93％ of the length of the line section D in C3,4,C4,5,C5,6,C6,7 respectively.The most medial distance the posterior percutaneous endoscopy could get in C5,6 or C6,7 was longer than that in C3,4,C4,5.Conclusion When 50％ of the lateral zygapophyseal joint was preserved,the upper limit of the most medial distance ratio that the posterior percutaneous endoscopy should get were 78％,76％,81％,93％ in C3,4,C4,5,C5,6,C6,7 respectively.This meant that the most medial distance the posterior percutaneous endoscopy could get were the 78％,76％,81％,93％ of the length of line section D in C3,4,C4,5,C5,6,C6,7 respectively.If the resected disc was beyond this range,the cervical spinal cord should be in the risk of being injured.