Objective: To compare the incidence of adjacent segment degeneration (ASDeg) and clinical outcomes of minimally invasive versus traditional transforaminal lumbar interbody fusion (TLIF) in the treatment of L _4,5 single-segment lumbar spinal stenosis (LSS) and explore the risk factors of ASDeg. Methods: All of 115 patients with LSS who were treated by the same group of doctors from 2009 to 2013, with a minimum follow-up of 5 years. Thirty-eight patients underwent minimally invasive trans-foraminal lumbar interbody fusion (MIS-TLIF) and 77 patients underwent traditional TLIF. Standing radiographs at the preopera-tive period and the final follow-up were assessed. Radiological parameters included lumbar lordosis (LL), fused segment angle (FSA), disc height (DH) and range of motion (ROM). Babu classification was used to identify facet joint violation (FJV) in patients at 5-year follow-up. Clinical outcomes were assessed according to visual analog scale (VAS) score, Japanese Orthopaedic Associa-tion (JOA) score and Oswestry Disability Index (ODI). Student's t-test, Chi-square test, and non-parametric test were used as the main statistical methods. Results: The mean age of MIS-TLIF group was 58.2±8.8 years, and that of TLIF group was 54.7±11.2 years, and there was no significant difference between the two groups. The mean follow-up time was 64.5±3.8 months in the MIS-TLIF group and 63.9±3.3 months in the TLIF group, and there was no significant difference between the two groups. There were 17 cases of degenerative spondylolisthesis in MIS-TLIF group (44.7%) and 35 cases of degenerative spondylolisthesis in TLIF group (45.5%), and there was no significant difference between the two groups. There was no significant difference in DH and ROM of L_3,4, L_4,5, L₅S₁ between the two groups before operation. There was no significant difference in VAS, JOA and ODI scores between the two groups before operation. The VAS, JOA and ODI scores were significantly improved at the last follow-up compared with those before operation. After 5-year follow-up, 56 cases (48.7%) had ASDeg. The incidence of ASDeg was 31.6% in MIS-TLIF group and 57.1% in TLIF group, and there was statistical differences between the two groups (χ²=6.656, P <0.01). Among them, 32 cases only had upper segment ASDeg (6 cases in MIS-TLIF group, 26 cases in TLIF group), 19 cases only had lower segment ASDeg (6 cases in MIS-TLIF group, 13 cases in TLIF group), and 5 cases had both upper and lower ASDeg (5 cases in the TLIF group). The DH of adjacent segments decreased after operation, but the loss of DH in MIS-TLIF group was smaller than that in TLIF group, including L_3,4 segments (-4.9%±6.4% vs-8.7%±7.2%, t=-2.761, P <0.01), L5S1 segment (-4.7%±9.8% vs-10.5%±11.7%, t=-2.623, P <0.01). The ROM of adjacent segments increased in both groups, but the increase of ROM in MIS-TLIF group was smaller than that in TLIF group, including L _3,4 segments (1.1°±1.8° vs 2.3°±2.5°, t=-3.122, P <0.01), L₅S₁ segment (0.9°± 1.9 ° vs 1.8°±1.9 °, t=-2.353, P <0.01). The incidence of FJV was 54.2% in patients with ASDeg in MIS-TLIF group and 47.7% in patients with ASDeg in TLIF group. Chi-square analysis showed that FJV was related to ASDeg in both groups (χ²=3.869, P < 0.05). Conclusion Both of the two surgical methods have good clinical effects on L _4,5 single-segment LSS. The incidence of AS-Deg after MIS-TLIF is lower than that of TLIF. FJV is a risk factor for ASDeg.

Objective:To investigate CT classification of diffuse idiopathic skeletal hyperostosis (DISH), and to analyze the correlation between the position of ossification in the anterolateral spine and the sagittal configuration of the spine.Methods:The medical records of 109 patients (70 male and 39 female) who underwent whole spine computerized tomography (CT) from October 2018 to October 2020 were retrospectively analyzed. The average age was 68.4±6.9 years old, ranging from 60 to 88 years old. High resolution CT volume rendering technique images were used to assess the degree of anterolateral spinal ossification in each vertebral space, and a CT grading system was established. Sagittal parameters such as thoracic kyphosis (TK), lumbar lordosis(LL), cervical lordosis (CL), sacral slope (SS), and thoracolumbar junction angle (TLJ) of the patients were measured. The sagittal morphology of the spine was divided into four types using the modified Abelin-Genevois (AG) sagittal classification. In AG type 1 patients, the kyphotic vertex was located in the middle of the thoracic spine (T 4-T 11). In AG type 2 patients, there was no significant kyphotic vertex. In AG type 3 patients, the kyphotic vertex was located in the thoracolumbar segment (T 12-L 2). In AG type 4 patients, the kyphotic vertex was located in the upper thoracic segment (T 1-T 3). Inter-observer and intra-observer reliability were calculated by intra-group correlation coefficient ( ICC). Statistical analysis was conducted to investigate the correlation between different AG types and ossification location and severity. Results:The new DISH grading system classifies the severity of anterolateral spinal ossification in each intervertebral space into grades 0 to 3 with an intra-observer ICC value of 0.871 and inter-observer ICC value of 0.874. Combined with Resnick's DISH diagnostic criteria, 97 patients (89.0%) in this study had four consecutive intervertebral spaces with ossification grade 1 or above. For these patients, in T 4-T 11, the standardized ossification grade of AG type 1 was 1.24±0.69, greater than that of AG type 2 (0.84±0.71) and AG type 3 (1.00±0.70), and the differences were statistically significant ( F=23.101, P<0.001). In T 12-L 2, the standardized ossification grade of AG type 3 was 1.44±0.87, which was higher than AG type 1 (1.06±0.84) and AG type 2 (0.72±0.63), the differences were statistically significant ( F=14.008, P<0.001). In this study, no patients with kyphosis apex in the cervicothoracic region (AG type4) were found. In T 1-T 3, there was no statistical difference between the three groups ( F=0.303, P=0.738); in the whole thoracic and lumbar spine (T 1-L 5), there was statistically significant difference in the total ossification grade ( F=14.374, P<0.001), there was no statistical difference between AG type 1 and AG type 3 ( P=0.254), both of which were higher than AG type 2 ( P<0.001). Conclusion:The new DISH ossification grading system proposed in this study has high credibility, which can be used in DISH's study. This study confirmed that the region where the apex of kyphosis is located is prone to anterolateral ossification of the spine.