What are the optimal disc height changes for successful indirect decompression with OLIF? Analysis of pre- and postoperative parameter changes up to 1 year

What are the optimal disc height changes for successful indirect decompression with OLIF? 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Analysis of pre- and postoperative parameter changes up to 1 year Yoonjoong Hwang, Jihun Park, Jae-Young Hong, Jiwon Park, Jaewan Soh, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4929751/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract Study design : Retrospective study. Objective : To evaluate the associated factors for successful indirect decompression by assessing the changes in disc height and spinal canal width. Methods : This study included 63 patients and 104 involved surgical levels. The efficacy of OLIF for lumbar spinal stenosis on spinal canal and foramen before and after surgery was analyzed up to 1 year. Radiologic parameters were anterior disc height (ADH), posterior disc height (PDH), lumbar lordotic angle (LL), segmental lordotic angle (SL), foraminal height (FH), cross-sectional area (CSA) of the spinal canal, cross-sectional foraminal area (CSF), and subsidence (SD). Results : Comparing pre- and postoperative values, the mean CSA and CSF were significantly increased (p < 0.001). FH increased from 15.23 ± 3.48 mm to 18.78 ± 2.93 mm and was stable for up to 1 year (p < 0.0001). The VAS leg and ODI scores significantly improved after surgery (P < 0.05). Changes of immediate postoperative and 1-year FH were significantly related to 1 year ADH, PDH, and VAS leg changes (P < 0.05). The group showing 1-year FH improvement (positive(+) group) demonstrated significantly larger immediate postoperative ADH and PDH changes compared with the FH negative(-) group (6.46 mm vs. 4.52 mm, p = 0.038; 3.59 vs. 2.40, P < 0.001, respectively). The CSF positive(+) group also showed significantly higher immediate postoperative ADH and PDH changes (6.24 mm vs. 4.55 mm, p = 0.043; 3.00 vs. 1.57, P = 0.010, respectively). Conclusions OLIF provided satisfactory indirect decompression up to 1 year. Considering the increase of foraminal height, we recommend more than 3.0 mm of immediate postoperative PDH increase, avoiding over-distraction of disc space. Health sciences/Rheumatology/Musculoskeletal system Health sciences/Medical research/Outcomes research Figures Figure 1 Figure 2 Introduction Oblique lumbar interbody fusion (OLIF) is a minimally invasive surgical technique for lumbar spine diseases with minimal trauma and quick recovery compared with conventional posterior lumbar interbody fusion surgery. The key advantages of OLIF are indirect neural decompression of the spinal canal and prevention of iatrogenic dural tear or nerve root injury. [1–3] In OLIF surgery, insertion of a cage into the intervertebral disc space can restore disc height and indirectly distract the posterior element of the vertebral column, providing expansion of the spinal canal and foramen. In addition, several studies have reported permanent regression of the thickened ligamentum flavum after surgery. [4–8] Park et al. reported that intraoperatively modifiable factors of improvement of anterior disc height (ADH), posterior disc height (PDH), and restoration of segmental lordosis (SL) are related to distraction of posterior vertebral elements.[9] However, target or optimal changes of modifiable parameters for successful indirect decompression have not been analyzed. Changes of disc height is closely related to foraminal height and symptom improvement; however, over-distraction of disc space may induce subsidence and failure of indirect decompression. The purpose of this study was to evaluate the preoperative and postoperative changes of parameters to determine the optimal values to achieve successful indirect decompression for up to 1 year. Methods Subjects We included 63 patients who underwent OLIF by a single surgeon between 2018 and 2022 was evaluated. We included patients who were diagnosed with lumbar stenosis, underwent less than two-level surgery, and underwent indirect decompression. We excluded the patients who underwent open decompression at the same level. All surgeries were performed with oblique lateral approach, followed by percutaneous posterior pedicle screw fixations. This study was approved by the Institutional Review Board of Korea University Ansan Hospital (IRB No. 2022AS0307). Informed consent was exempted by Institutional Review Board. All methods were performed in accordance with the relevant guidelines and regulations. Radiological and clinical parameters Plain radiographs and CT were evaluated pre- and postoperatively up to 1 year. In addition, pre- and postoperative (1 week) MRI was performed for all patients. We defined ADH as the distance between the superior and the inferior endplate at the anterior vertebral edge. PDH was calculated as the length between the superior to the inferior endplate at the posterior vertebral edge. LL was the angle between the upper endplates of L1 and upper part of S1 vertebrae. FH was the length from the lower pedicle border of the upper level vertebra to the superior border of the lower level. We defined SL as the angle between the superior endplate of the upper and the inferior endplate of the lower vertebrae. Subsidence was defined as a greater than 2mm height decrease from immediately postoperative to 1-year postoperative radiographs. The CSA of the spinal canal and the CSF of the left and right intervertebral foramen was measured on T2 axial and sagittal MRI (Fig. 1 ). Clinical parameters including pre- and postoperative visual analogue score (VAS) and Oswestry Disability Index (ODI) were evaluated up to 1 year. Statistical analysis Radiographic measurements were performed by two orthopedic spine surgeons (first and second authors). Preoperative and postoperative parameters were compared using a paired t-test. The relationships of parameters were analyzed using the Pearson’s correlation coefficient. To determine significant disc height changes compared with postoperative foraminal height increase, ROC analysis was applied. All statistical analyses were performed using SAS software (version 9.3; SAS Institute, Cary, NC, USA). Results Table 1 summarizes the basic information of the 63 patients included in the study. The mean age of the 21 males and 42 females was 69.52 ± 7.92 years. Among the 104 surgical levels, 46.15% (n = 48) involved L3–4. Among the 63 patients, 18 underwent one-level OLIF surgery and 45 underwent two-level OLIF surgery. Table 1 Characteristics of the study group Demographics Age 69.52 ± 7.92 M:F = 21:42 Disease type Deg.stenosis* 44 (63.5%) ASD** 9 (14.29%) Deg.Listhesis*** 10 (15.87%) Fusion levels (N = 104) L2–3 23 (22.12%) L3–4 48 (46.15%) L4–5 33 (31.73%) Fused segments 1 level 18 (28.57%) 2 level 45 (71.43%) Complication Subsidence + 19 (18.27%) Transient sensory change 6 (9.52%) Pneumonia 1 (1.59%) Deg.stenosis: Degenerative stenosis ASD: Adjacent segment disease Deg.listhesis: Degenerative spondylolisthesis + Subsidence: Greater than 2 mm height decrease Pre- and postoperative changes up to 1 year The results showed that OLIF combined with percutaneous pedicle screw fixation effectively restored disc height and increased the cross-sectional area of the spinal canal (Table 2 ). FH increased from 15.23 ± 3.48 mm to 18.78 ± 2.93 mm and was stable up to 1 year (p < 0.0001). ADH and PDH also significantly increased and were stable up to 1 year (p < 0.0001). Comparing pre- and postoperative MRI values, mean CSA increased from 71.61 ± 47.48 mm 2 to 92.81 ± 58.64 mm 2 and mean left CSF increased from 46.57 ± 14.75 mm 2 to 70.27 ± 19.46 mm 2 (p < 0.05). The leg VAS and ODI scores significantly improved after surgery, and the improvement was preserved up to 1 year (P < 0.05). Table 2 Mean postoperative changes up to 1 year Before surgery After surgery At 1 year P Plain radiographs LL (°) 25.62 ± 16.76 29.38 ± 13.35 28.54 ± 10.67 < 0.001 SL (°) 7.10 ± 9.51 9.08 ± 8.04 8.73 ± 7.00 < 0.001 ADH (mm) 7.77 ± 3.77 13.37 ± 3.38 11.47 ± 2.52 < 0.001 PDH (mm) 4.61 ± 1.80 7.68 ± 2.04 6.67 ± 2.00 < 0.001 FH (mm) 15.23 ± 3.48 18.78 ± 2.93 17.40 ± 2.50 < 0.001 MRI measurement CSA (mm 2 ) 71.61 ± 47.48 92.81 ± 58.64 < 0.001 CSF Lt (mm 2 ) 46.57 ± 14.75 70.27 ± 19.46 < 0.001 CSF Rt (mm 2 ) 36.69 ± 13.77 57.37 ± 17.74 < 0.001 Clinical scores VAS leg 7.47 ± 1.62 4.22 ± 2.36 4.67 ± 1.16 0.020 ODI 25.32 ± 9.16 21.42 ± 10.38 17.3 ± 8.08 < 0.001 LL: Lumbar lordosis SL: Sacral slope ADH: Anterior disc height PDH: Posterior disc height FH: Foraminal height CSA: Cross-sectional area of the thecal sac CSF: Cross-sectional foraminal area VAS: Visual analogue scale ODI: Oswestry disability index Relationships between parameters Table 3 summarizes the relationships between parameters. Immediate postoperative CSA and CSF changes significantly correlated with 1 year PDH changes (r = 0.221, p = 0.040; and r = 0.162, p = 0.016, respectively). Changes of immediate postoperative and 1 year FH were significantly related to 1 year ADH and PDH changes (P < 0.05). We found a significant relationship between FH changes immediately postoperative and at 1 year with 1-year VAS leg changes (r = 0.151, p = 0.043; and r = 0.096, p = 0.045, respectively). Table 3 Correlation analysis of parameters ADH changes PDH changes Leg VAS changes (1 year) CSA changes 0.129 (p = 0.202) 0.221 ( p = 0.040 ) 0.091 (p = 0.474) CSF Lt changes 0.109 (p = 0.280) 0.162 ( p = 0.016 ) 0.065 (p = 0.609) CSF Rt changes 0.061 (p = 0.615) 0.303 ( p = 0.011 ) 0.022 (p = 0.863) FH changes 0.245 ( p = 0.012 ) 0.291 ( p = 0.003 ) 0.151 ( p = 0.043 ) FH changes (1 year) 0.273 ( p = 0.010 ) 0.269 ( p = 0.011 ) 0.096 ( p = 0.045 ) ADH: Anterior disc height PDH: Posterior disc height CSA: Cross-sectional area of the thecal sac, CSF: Cross-sectional foraminal area VAS: Visual analogue scale FH: Foraminal height Optimal height changes for successful indirect decompression Table 4 shows the comparison of the ADH and PDH changes according to degree of indirect decompression up to 1 year. We performed ROC analysis to determine cut off values of parameters that indicate degree of indirect decompression. Immediate postoperative ADH and PDH changes were reliable predictors of indirect decompression according to ROC analysis (AUC = 0.654; 0.684, respectively). The 1-year FH improvement positive(+) group, defined as those with greater than 2.21 mm of height increase compared with preoperative value, showed significantly higher ADH and PDH changes (6.46 mm vs. 4.52 mm, p = 0.038; 3.59 vs. 2.40, P < 0.001, respectively). Patients were divided according to CSF values into positive(+) and negative(-) groups (cut-off, 20.12 mm 2 ); significant differences of immediate postoperative ADH and PDH changes were observed (6.24 mm vs. 4.55 mm, p = 0.043; 3.00 vs. 1.57, P = 0.010, respectively). However, the CSA positive(+) and negative(-) groups (cut-off 21.02 mm 2 ) did not show significant differences of parameters (P > 0.05). The 1-year subsidence positive(+) group (> 2 mm) showed significant differences in immediate PDH increase (4.77 vs. 2.56, P < 0.001, respectively). Figure 2 shows pre- and postoperative radiographs of a patient in the 1-year FH positive(+) group. Table 4 Comparison of parameters between groups ADH increase (mm) PDH increase (mm) Leg VAS change FH1 year(+) 6.46 ± 6.17 3.59 ± 1.71 4.12 ± 1.71 FH1 year(-) 4.52 ± 3.60 2.40 ± 1.49 2.56 ± 0.71 p p = 0.038 p < 0.001 p < 0.001 CSF(+) 6.24 ± 6.13 3.00 ± 1.63 3.65 ± 1.71 CSF(-) 4.55 ± 2.22 1.57 ± 1.60 2.12 ± 1.71 p p = 0.043 p = 0.010 p = 0.103 CSA(+) 6.26 ± 6.67 3.39 ± 1.44 3.64 ± 1.71 CSA(-) 5.46 ± 3.25 3.21 ± 2.02 3.19 ± 1.71 p p = 0.374 p = 0.584 p = 0.234 Subsidence(+) 5.91 ± 2.93 4.77 ± 1.54 2.14 ± 1.99 Subsidence(-) 5.50 ± 3.14 2.56 ± 1.42 3.96 ± 2.34 p p = 0.553 p < 0.001 p = 0.011 ADH increase: Immediate postoperative anterior disc height increase PDH increase: Immediate postoperative posterior disc height increase CSA: Cross-sectional area of the thecal sac CSF: Cross-sectional foraminal area VAS: Visual analogue scale FH1 year(+): Greater than 2.21 mm of change in foraminal height group CSF(+): Greater than 20.12 mm 2 of change in CSF group CSA(+): Greater than 21.02 mm 2 of change in CSA group Subsidence(+): Greater than 2.00 mm of change in subsidence group Discussion OLIF surgery is believed to be efficacious for treatment of mechanical low back pain resulting from disc degeneration, segmental instability, or degenerative scoliosis. OLIF surgery is also considered for leg pain with neurogenic claudication accompanied by mild spinal canal stenosis.( 10 ) Previous studies on OLIF have primarily included single retrospective analysis of oblique lumbar interbody fusion (OLIF) treatment for lumbar spinal stenosis (LSS), comparative studies between OLIF and other surgical methods, and diagnostic analysis through CT or MRI measurements of the dura mater.( 11 – 14 ) In this study, values of the parameters at 1 year after the operation demonstrated varying degrees of increase or decrease compared with the immediate postoperative values, but all were significantly different from baseline. VAS for leg pain improved within 1 week following OLIF surgery, and this was preserved up to 1 year. In addition, with the radiologic improvement of CSA and CSF as well the immediate improvement of radicular symptoms, we suggest that OLIF surgery may offer an advantage in the treatment of radicular pain as well as neurogenic claudication due to spinal canal stenosis. By removing the intervertebral disc in the surgical segment and performing bone grafting and fusion in that segment, followed by implanting an appropriately sized cage to fully restore the intervertebral space in the surgical area, the displaced facet joint is indirectly returned to its normal anatomical position, increasing the foraminal and spinal canal spaces. However, additional direct decompression of bony stenosis and severe ligamentum flavum thickening was needed in some cases. A recent retrospective review of 45 patients (101 levels) reported that bony stenosis at the lateral recess is a predictor of failure of indirect decompression. Although indirect decompression using OLIF can stretch the soft tissue elements that compress the neural element, there may be a limitation of indirect decompression in relieving bony stenosis.( 15 ) However, symptoms can be resolved with a small amount of canal or foramen expansion with indirect decompression, as we reported in our study; thus, most cases including those with a severe degree of canal and foramen stenosis are good candidates for OLIF surgery ( 16 , 17 ). The success of indirect decompression through OLIF surgery depends on many factors. Previous studies on indirect decompression of OLIF reported significant increases in CSA, CSF, and FH postoperatively, which is consistent with the results of the current study ( 18 – 24 ). In OLIF surgery, a large cage can distract the interbody disc space as well as the posterior vertebral element, including the facet joint, restoring the disc and foraminal heights. Even though regression of the ligamentum flavum has been reported to have a significant role in CSA expansion over long-term follow-up, our results indicate that indirect decompression can also be successfully accomplished immediately with significant improvement in spatial radiological parameters. We found significant increments in ADH, PDH, FH, CSA, and CSF in immediate postoperative radiographs, and these were preserved up to 1 year. This result indicates that OLIF is sufficient to provide good mid-term radiological outcomes in patients with degenerative lumbar stenosis. In addition, the improvement of PDH correlated with improvement of CSF and FH. Immediate postoperative CSA and CSF changes were also significantly correlated with 1 year PDH change (r = 0.221, p = 0.040; and r = 0.162, p = 0.016, respectively). Changes of immediate postoperative and 1 year FH were significantly related to 1 year ADH and PDH changes, indicating an effect of indirect decompression on subsidence. Based on these findings, we conclude that sufficient indirect decompression after OLIF surgery can be accomplished in patients with intervertebral disc space narrowing, which can be fully opened and restored by insertion of a large cage. Adversely, direct decompression may be needed for young patients with preserved disc height and severe central canal stenosis. The indications of OLIF are important and significantly affect the success of indirect decompression. To achieve successful indirect decompression, it is important to restore posterior disc height while avoiding over-distraction, which may induce postoperative subsidence.( 9 ) In our study, the 1-year FH improvement positive(+) group showed significantly higher immediate postoperative PDH changes (3.59 vs. 2.40, P < 0.001). The CSF positive(+) group also showed significantly higher immediate postoperative ADH and PDH changes (6.24 mm vs. 4.55 mm, p = 0.043; 3.00 vs. 1.57, P = 0.010, respectively). Considering the improvement of foraminal height and symptoms, better outcome was expected with a greater than 3.0–3.6 mm immediate postoperative PDH increase; an increase less than 1.6–2.4 mm implies a worse outcome. Zeng et al. reported a retrospective analysis of 235 cases of perioperative complications after OLIF. Among these, 22 cases of endplate damage showed a probability of 9.36% and 18 cases of cage subsidence and displacement was a probability of 7.66%, resulting in a combined probability of 17.02%.( 25 ) Similarly, Abe et al. found that the most common perioperative complication in their retrospective study of 155 OLIF cases was endplate fracture/subsidence, with a probability of 18.7%.( 26 ) Similarly, the present study observed 18% of cases to have significant subsidence (> 2 mm), with a significantly higher immediate PDH increase (4.77 vs. 2.56, P < 0.001). This indicates the importance of subsidence consideration in OLIF surgery, for which symptoms can be resolved with a small amount of canal or foramen expansion without over-distraction of the disc space. In addition, cages positioned in the middle of the inferior vertebral body had a greater effect on improvement of FH.( 9 ) Therefore, the factors that significantly affect the improvement of CSF and FH are posterior disc height restoration and a more posterior location of the cage. These results support our hypothesis that the effect of indirect decompression through OLIF surgery might occur through distraction of the middle and posterior vertebral column. These results provide a strong rationale to place the cage in the middle or posteriorly to increase the amount of posterior disc height restoration and the amount of facet distraction for better outcomes after OLIF surgery. Our study has some limitations. First, this is a small retrospective study that included patients with a wide range of ages. This makes it difficult to accurately reflect the radiologic outcome with respect of the degree of degenerative change. Additionally, the small sample size may limit the reliability of the results. Furthermore, the follow-up observation was limited to 1 year, and longer-term tracking could offer more compelling evidence. Even though we found significant improvement in CSA, CSF, and foraminal height postoperatively, we did not evaluate 1 year postoperative MRI findings, which are as significant as other radiologic outcomes. Further research is required to clarify the minimal clinically important difference in each radiologic parameter for both successful radiological and clinical outcomes following OLIF surgery. Conclusions OLIF provided satisfactory indirect decompression with significant improvement of radiological parameters and symptoms up to 1 year. To achieve successful indirect decompression, restoration of PDH is important, considering improvement of foraminal height and symptoms. Thus, we recommend more than 3.0 mm of PDH increase, avoiding over-distraction, for successful indirect decompression. Declarations Funding Disclosures: No funds were received in support of this work. Author Contribution JYH, YJH and JHP wrote the main manuscript.JHP, JWS, JWP designed the study.DHS supervised the main manuscript. Acknowledgement The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. Data Availability The datasets used and/or analysed during the current study available from the corresponding author on reasonable request. References Mehren, C., Mayer, H. M., Zandanell, C., Siepe, C. J. & Korge, A. The Oblique Anterolateral Approach to the Lumbar Spine Provides Access to the Lumbar Spine With Few Early Complications. Clin. Orthop. Relat. Res. 474 (9), 2020–2027 (2016). Park, J. et al. Minimally Invasive Spine Surgery: Techniques, Technologies, and Indications. Asian Spine J. 14 (5), 694–701 (2020). Mobbs, R. J., Phan, K., Malham, G., Seex, K. & Rao, P. J. Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF. J. Spine Surg. 1 (1), 2–18 (2015). Shimizu, T., Fujibayashi, S., Otsuki, B., Murata, K. & Matsuda, S. Indirect decompression with lateral interbody fusion for severe degenerative lumbar spinal stenosis: minimum 1-year MRI follow-up. J. Neurosurg. Spine ;1–8. (2020). Limthongkul, W. et al. Indirect Decompression Effect to Central Canal and Ligamentum Flavum After Extreme Lateral Lumbar Interbody Fusion and Oblique Lumbar Interbody Fusion. Spine (Phila Pa. 1976) . 45 (17), E1077–E84 (2020). Shimizu, T., Fujibayashi, S., Otsuki, B., Murata, K. & Matsuda, S. Indirect decompression via oblique lateral interbody fusion for severe degenerative lumbar spinal stenosis: a comparative study with direct decompression transforaminal/posterior lumbar interbody fusion. Spine J. 21 (6), 963–971 (2021). Ohtori, S. et al. Change of Lumbar Ligamentum Flavum after Indirect Decompression Using Anterior Lumbar Interbody Fusion. Asian Spine J. 11 (1), 105–112 (2017). Mahatthanatrakul, A., Kim, H. S., Lin, G. X. & Kim, J. S. Decreasing thickness and remodeling of ligamentum flavum after oblique lumbar interbody fusion. Neuroradiology . 62 (8), 971–978 (2020). Park, J., Park, S. M., Han, S., Jeon, Y. & Hong, J. Y. Factors affecting successful immediate indirect decompression in oblique lateral interbody fusion in lumbar spinal stenosis patients. N Am. Spine Soc. J. ; 16 . (2023). Li, R., Li, X., Zhou, H. & Jiang, W. Development and application of oblique lumbar interbody fusion. Orthop. Surg. 12 (2), 355–365 (2020). Li, H. M., Zhang, R. J. & Shen, C. L. Differences in radiographic and clinical outcomes of oblique lateral interbody fusion and lateral lumbar interbody fusion for degenerative lumbar disease: a meta-analysis. BMC Musculoskelet. Disord . 20 (1), 582 (2019). Hung, S. F. et al. Comparison of outcomes between indirect decompression of oblique lumbar interbody fusion and MIS-TLIF in one single-level lumbar spondylosis. Sci. Rep. 11 (1), 12783 (2021). Zhu, H. F. et al. Comparison of oblique lateral interbody fusion (OLIF) and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for treatment of lumbar degeneration disease: a prospective cohort study. Spine . 47 (6), E233–E242 (2022). Lin, G. X. et al. Clinical and radiologic outcomes of direct versus indirect decompression with lumbar interbody fusion: a matched-pair comparison analysis. World Neurosurg. 119 , e898–909 (2018). Wang, T. Y. et al. Bony Lateral Recess Stenosis and Other Radiographic Predictors of Failed Indirect Decompression via Extreme Lateral Interbody Fusion: Multi-Institutional Analysis of 101 Consecutive Spinal Levels. World Neurosurg. 106 , 819–826 (2017). Gajjar, S., Jhala, A. & Mistry, M. Effectiveness of indirect decompression in severe degenerative lumbar central canal stenosis by oblique lumbar interbody fusion. J. Minim. Invasive Spine Surg. Tech. 6 (2), 131–140 (2021). Tseng, S. C. et al. Indirect decompression via oblique lumbar interbody fusion is sufficient for treatment of lumbar foraminal stenosis. Front. Surg. 9 , 911514 (2022). Lin, G. X., Rui, G., Sharma, S., Mahatthanatrakul, A. & Kim, J. S. The correlation of intraoperative distraction of intervertebral disc with the postoperative canal and foramen expansion following oblique lumbar interbody fusion. Eur. Spine J. 30 (1), 151–163 (2021). Kepler, C. K. et al. Factors influencing segmental lumbar lordosis after lateral transpsoas interbody fusion. Orthop. Surg. 4 (2), 71–75 (2012). Park, S. J. et al. The Ideal Cage Position for Achieving Both Indirect Neural Decompression and Segmental Angle Restoration in Lateral Lumbar Interbody Fusion (LLIF). Clin. Spine Surg. 30 (6), E784–e90 (2017). Sato, J. et al. Radiographic evaluation of indirect decompression of mini-open anterior retroperitoneal lumbar interbody fusion: oblique lateral interbody fusion for degenerated lumbar spondylolisthesis. Eur. Spine J. 26 (3), 671–678 (2017). Morita, D. et al. Dynamic changes in the crosssectional area of the dural sac and spinal cord in the thoracic spine. Eur. Spine J. 26 (1), 64–70 (2017). Zheng, B. et al. Radiographic analysis of neuroforaminal and central canal decompression following lateral lumbar interbody fusion. N Am. Spine Soc. J. ; 10 . (2022). Ko, S. Correlations between sedimentation sign, dural sac cross-sectional area, and clinical symptoms of degenerative lumbar spinal stenosis. Eur. Spine J. 27 (7), 1623–1628 (2018). Zeng, Z. Y. et al. Complications and prevention strategies of oblique lateral interbody fusion technique. Orthop. Surg. 10 (2), 98–106 (2018). Abe, K. et al. Perioperative complications in 155 patients who underwent oblique lateral interbody fusion surgery: perspectivesand indications from a retrospective multicenter survey. Spine . 42 (1), 55–62 (2017). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 01 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 31 Mar, 2025 Reviews received at journal 27 Mar, 2025 Reviewers agreed at journal 12 Mar, 2025 Reviews received at journal 07 Feb, 2025 Reviewers agreed at journal 23 Jan, 2025 Reviews received at journal 07 Dec, 2024 Reviewers agreed at journal 28 Nov, 2024 Reviewers invited by journal 28 Nov, 2024 Editor assigned by journal 27 Nov, 2024 Editor invited by journal 23 Aug, 2024 Submission checks completed at journal 22 Aug, 2024 First submitted to journal 17 Aug, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4929751","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":357489320,"identity":"c29b80cf-d0e6-4dbd-90a5-d863df597825","order_by":0,"name":"Yoonjoong Hwang","email":"","orcid":"","institution":"Korea University Ansan Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yoonjoong","middleName":"","lastName":"Hwang","suffix":""},{"id":357489321,"identity":"08205c3f-f5ab-4d1c-b6af-f97e4b5fe257","order_by":1,"name":"Jihun Park","email":"","orcid":"","institution":"Korea University Ansan Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jihun","middleName":"","lastName":"Park","suffix":""},{"id":357489322,"identity":"798c6785-0474-4965-a692-6c00e0c25dc4","order_by":2,"name":"Jae-Young Hong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0klEQVRIiWNgGAWjYLCCBAYGOQk4j4dILcYkagGCxBlEa+HnP/7swcMdNukz23sfPvjBYCfPwHP2AV4tkjNyzA0Sz6TlzuY5bmzYw5Bs2MDbboBXi8ENHjaJxLbDufMk0tgkeBiYExj42fA7zOD88WdALf/T5STS2H/+YagnQsuBBDOglgMJ0kBbmHkYDicw8Lbh1wLxS1uy4cyeY8zSMgbHDdt4juHXAgqxhz/b7OQljrcxfnxTUS3Pz5OGXwsQIDvdAJVLjJZRMApGwSgYBVgAAHtBOm2n3EIBAAAAAElFTkSuQmCC","orcid":"","institution":"Korea University Ansan Hospital","correspondingAuthor":true,"prefix":"","firstName":"Jae-Young","middleName":"","lastName":"Hong","suffix":""},{"id":357489323,"identity":"7ff12c6a-e723-41f3-9195-02e9f54a3c8d","order_by":3,"name":"Jiwon Park","email":"","orcid":"","institution":"Korea University Ansan Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jiwon","middleName":"","lastName":"Park","suffix":""},{"id":357489324,"identity":"b2c9ef9a-1786-4750-9947-4b527f940784","order_by":4,"name":"Jaewan Soh","email":"","orcid":"","institution":"Hanyang University Guri Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jaewan","middleName":"","lastName":"Soh","suffix":""},{"id":357489325,"identity":"d7539e75-7411-48f5-bdf8-5c6b660914b9","order_by":5,"name":"Dong Hun Suh","email":"","orcid":"","institution":"Korea University Ansan Hospital","correspondingAuthor":false,"prefix":"","firstName":"Dong","middleName":"Hun","lastName":"Suh","suffix":""}],"badges":[],"createdAt":"2024-08-17 12:18:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4929751/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4929751/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-05562-4","type":"published","date":"2025-07-01T15:58:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":66748885,"identity":"769ba6f8-3664-46e6-be1a-87f35c00cb9a","added_by":"auto","created_at":"2024-10-16 06:54:51","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1481773,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement of parameters\u003c/p\u003e\n\u003cp\u003e(a) Anterior disc height (ADH), posterior disc height (PDH), lumbar lordosis (LL), and segmental lordotic angle (SL) were evaluated on lateral radiographs.\u003c/p\u003e\n\u003cp\u003e(b) Cross-sectional area (CSA) of the thecal sac and CSA of the intervertebral foramen (CSF) were evaluated on T2-weighted sagittal MRI.\u003c/p\u003e","description":"","filename":"Fig1a2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4929751/v1/9f50ebd3b4130491d0638972.jpg"},{"id":66748886,"identity":"005f1c8d-ee41-47b0-8b5a-143cdca99904","added_by":"auto","created_at":"2024-10-16 06:54:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":4808774,"visible":true,"origin":"","legend":"\u003cp\u003ePre- and postoperative radiographs of an FH positive(+) patient.\u003c/p\u003e\n\u003cp\u003eMale 67-year-old patient with OLIF L3–4–5 who showed 4.19 mm and 3.93 of immediate postoperative PDH changes (a, b). One-year follow-up radiographs showed 3.32 mm and 4.46 of FH changes, respectively (c). Final FH changes were stable with union of graft and were associated with significant improvement of leg VAS (d).\u003c/p\u003e","description":"","filename":"Fig2abcd.png","url":"https://assets-eu.researchsquare.com/files/rs-4929751/v1/b3269dc269420f4d4d481970.png"},{"id":86180020,"identity":"f16a9156-506e-46b7-a189-aa1b1374e573","added_by":"auto","created_at":"2025-07-07 16:20:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6555761,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4929751/v1/51f470a4-9201-4c54-8930-1a86b697bd49.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eWhat are the optimal disc height changes for successful indirect decompression with OLIF? \u003c/p\u003e\n\u003cp\u003eAnalysis of pre- and postoperative parameter changes up to 1 year\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOblique lumbar interbody fusion (OLIF) is a minimally invasive surgical technique for lumbar spine diseases with minimal trauma and quick recovery compared with conventional posterior lumbar interbody fusion surgery. The key advantages of OLIF are indirect neural decompression of the spinal canal and prevention of iatrogenic dural tear or nerve root injury. [1\u0026ndash;3] In OLIF surgery, insertion of a cage into the intervertebral disc space can restore disc height and indirectly distract the posterior element of the vertebral column, providing expansion of the spinal canal and foramen. In addition, several studies have reported permanent regression of the thickened ligamentum flavum after surgery. [4\u0026ndash;8] Park et al. reported that intraoperatively modifiable factors of improvement of anterior disc height (ADH), posterior disc height (PDH), and restoration of segmental lordosis (SL) are related to distraction of posterior vertebral elements.[9] However, target or optimal changes of modifiable parameters for successful indirect decompression have not been analyzed. Changes of disc height is closely related to foraminal height and symptom improvement; however, over-distraction of disc space may induce subsidence and failure of indirect decompression. The purpose of this study was to evaluate the preoperative and postoperative changes of parameters to determine the optimal values to achieve successful indirect decompression for up to 1 year.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSubjects\u003c/h2\u003e \u003cp\u003eWe included 63 patients who underwent OLIF by a single surgeon between 2018 and 2022 was evaluated. We included patients who were diagnosed with lumbar stenosis, underwent less than two-level surgery, and underwent indirect decompression. We excluded the patients who underwent open decompression at the same level. All surgeries were performed with oblique lateral approach, followed by percutaneous posterior pedicle screw fixations. This study was approved by the Institutional Review Board of Korea University Ansan Hospital (IRB No. 2022AS0307). Informed consent was exempted by Institutional Review Board. All methods were performed in accordance with the relevant guidelines and regulations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eRadiological and clinical parameters\u003c/h2\u003e \u003cp\u003ePlain radiographs and CT were evaluated pre- and postoperatively up to 1 year. In addition, pre- and postoperative (1 week) MRI was performed for all patients. We defined ADH as the distance between the superior and the inferior endplate at the anterior vertebral edge. PDH was calculated as the length between the superior to the inferior endplate at the posterior vertebral edge. LL was the angle between the upper endplates of L1 and upper part of S1 vertebrae. FH was the length from the lower pedicle border of the upper level vertebra to the superior border of the lower level. We defined SL as the angle between the superior endplate of the upper and the inferior endplate of the lower vertebrae. Subsidence was defined as a greater than 2mm height decrease from immediately postoperative to 1-year postoperative radiographs. The CSA of the spinal canal and the CSF of the left and right intervertebral foramen was measured on T2 axial and sagittal MRI (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Clinical parameters including pre- and postoperative visual analogue score (VAS) and Oswestry Disability Index (ODI) were evaluated up to 1 year.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eRadiographic measurements were performed by two orthopedic spine surgeons (first and second authors). Preoperative and postoperative parameters were compared using a paired t-test. The relationships of parameters were analyzed using the Pearson\u0026rsquo;s correlation coefficient. To determine significant disc height changes compared with postoperative foraminal height increase, ROC analysis was applied. All statistical analyses were performed using SAS software (version 9.3; SAS Institute, Cary, NC, USA).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the basic information of the 63 patients included in the study. The mean age of the 21 males and 42 females was 69.52\u0026thinsp;\u0026plusmn;\u0026thinsp;7.92 years. Among the 104 surgical levels, 46.15% (n\u0026thinsp;=\u0026thinsp;48) involved L3\u0026ndash;4. Among the 63 patients, 18 underwent one-level OLIF surgery and 45 underwent two-level OLIF surgery.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of the study group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eDemographics\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69.52\u0026thinsp;\u0026plusmn;\u0026thinsp;7.92\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eM:F\u0026thinsp;=\u0026thinsp;21:42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDisease type\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDeg.stenosis*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44 (63.5%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eASD**\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9 (14.29%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDeg.Listhesis***\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (15.87%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFusion levels\u003c/b\u003e (N\u0026thinsp;=\u0026thinsp;104)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eL2\u0026ndash;3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23 (22.12%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eL3\u0026ndash;4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48 (46.15%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eL4\u0026ndash;5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33 (31.73%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFused segments\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1 level\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18 (28.57%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2 level\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45 (71.43%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eComplication\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSubsidence\u003c/b\u003e\u003csup\u003e\u003cb\u003e+\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19 (18.27%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTransient sensory change\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (9.52%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePneumonia\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (1.59%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eDeg.stenosis: Degenerative stenosis\u003c/p\u003e \u003cp\u003eASD: Adjacent segment disease\u003c/p\u003e \u003cp\u003eDeg.listhesis: Degenerative spondylolisthesis\u003c/p\u003e \u003cp\u003e\u003csup\u003e\u003cb\u003e+\u003c/b\u003e\u003c/sup\u003eSubsidence: Greater than 2 mm height decrease\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003ePre- and postoperative changes up to 1 year\u003c/h2\u003e \u003cp\u003eThe results showed that OLIF combined with percutaneous pedicle screw fixation effectively restored disc height and increased the cross-sectional area of the spinal canal (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). FH increased from 15.23\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48 mm to 18.78\u0026thinsp;\u0026plusmn;\u0026thinsp;2.93 mm and was stable up to 1 year (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). ADH and PDH also significantly increased and were stable up to 1 year (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Comparing pre- and postoperative MRI values, mean CSA increased from 71.61\u0026thinsp;\u0026plusmn;\u0026thinsp;47.48 mm\u003csup\u003e2\u003c/sup\u003e to 92.81\u0026thinsp;\u0026plusmn;\u0026thinsp;58.64 mm\u003csup\u003e2\u003c/sup\u003e and mean left CSF increased from 46.57\u0026thinsp;\u0026plusmn;\u0026thinsp;14.75 mm\u003csup\u003e2\u003c/sup\u003e to 70.27\u0026thinsp;\u0026plusmn;\u0026thinsp;19.46 mm\u003csup\u003e2\u003c/sup\u003e (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The leg VAS and ODI scores significantly improved after surgery, and the improvement was preserved up to 1 year (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMean postoperative changes up to 1 year\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBefore surgery\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAfter surgery\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAt 1 year\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003ePlain radiographs\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLL\u003c/b\u003e (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.62\u0026thinsp;\u0026plusmn;\u0026thinsp;16.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29.38\u0026thinsp;\u0026plusmn;\u0026thinsp;13.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28.54\u0026thinsp;\u0026plusmn;\u0026thinsp;10.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSL\u003c/b\u003e (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.10\u0026thinsp;\u0026plusmn;\u0026thinsp;9.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.08\u0026thinsp;\u0026plusmn;\u0026thinsp;8.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.73\u0026thinsp;\u0026plusmn;\u0026thinsp;7.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eADH\u003c/b\u003e (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.77\u0026thinsp;\u0026plusmn;\u0026thinsp;3.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.37\u0026thinsp;\u0026plusmn;\u0026thinsp;3.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.47\u0026thinsp;\u0026plusmn;\u0026thinsp;2.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePDH\u003c/b\u003e (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.61\u0026thinsp;\u0026plusmn;\u0026thinsp;1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.68\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.67\u0026thinsp;\u0026plusmn;\u0026thinsp;2.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFH\u003c/b\u003e (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.23\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e18.78\u0026thinsp;\u0026plusmn;\u0026thinsp;2.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.40\u0026thinsp;\u0026plusmn;\u0026thinsp;2.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMRI measurement\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSA\u003c/b\u003e (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e71.61\u0026thinsp;\u0026plusmn;\u0026thinsp;47.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e92.81\u0026thinsp;\u0026plusmn;\u0026thinsp;58.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF Lt\u003c/b\u003e (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46.57\u0026thinsp;\u0026plusmn;\u0026thinsp;14.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.27\u0026thinsp;\u0026plusmn;\u0026thinsp;19.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF Rt\u003c/b\u003e (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.69\u0026thinsp;\u0026plusmn;\u0026thinsp;13.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e57.37\u0026thinsp;\u0026plusmn;\u0026thinsp;17.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eClinical scores\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eVAS leg\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.47\u0026thinsp;\u0026plusmn;\u0026thinsp;1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.020\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eODI\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.32\u0026thinsp;\u0026plusmn;\u0026thinsp;9.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.42\u0026thinsp;\u0026plusmn;\u0026thinsp;10.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e17.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eLL: Lumbar lordosis\u003c/p\u003e \u003cp\u003eSL: Sacral slope\u003c/p\u003e \u003cp\u003eADH: Anterior disc height\u003c/p\u003e \u003cp\u003ePDH: Posterior disc height\u003c/p\u003e \u003cp\u003eFH: Foraminal height\u003c/p\u003e \u003cp\u003eCSA: Cross-sectional area of the thecal sac\u003c/p\u003e \u003cp\u003eCSF: Cross-sectional foraminal area\u003c/p\u003e \u003cp\u003eVAS: Visual analogue scale\u003c/p\u003e \u003cp\u003eODI: Oswestry disability index\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eRelationships between parameters\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes the relationships between parameters. Immediate postoperative CSA and CSF changes significantly correlated with 1 year PDH changes (r\u0026thinsp;=\u0026thinsp;0.221, p\u0026thinsp;=\u0026thinsp;0.040; and r\u0026thinsp;=\u0026thinsp;0.162, p\u0026thinsp;=\u0026thinsp;0.016, respectively). Changes of immediate postoperative and 1 year FH were significantly related to 1 year ADH and PDH changes (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). We found a significant relationship between FH changes immediately postoperative and at 1 year with 1-year VAS leg changes (r\u0026thinsp;=\u0026thinsp;0.151, p\u0026thinsp;=\u0026thinsp;0.043; and r\u0026thinsp;=\u0026thinsp;0.096, p\u0026thinsp;=\u0026thinsp;0.045, respectively).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrelation analysis of parameters\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eADH changes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePDH changes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeg VAS changes\u003c/p\u003e \u003cp\u003e(1 year)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSA changes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.129\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.202)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.221\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.040\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.091\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.474)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF Lt changes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.109\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.280)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.162\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.016\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.065\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.609)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF Rt changes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.061\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.615)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.303\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.011\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.022\u003c/p\u003e \u003cp\u003e(p\u0026thinsp;=\u0026thinsp;0.863)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFH changes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.245\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.012\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.291\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.003\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.151\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.043\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFH changes\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(1 year)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.273\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.010\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.269\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.011\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.096\u003c/p\u003e \u003cp\u003e(\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.045\u003c/b\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eADH: Anterior disc height\u003c/p\u003e \u003cp\u003ePDH: Posterior disc height\u003c/p\u003e \u003cp\u003eCSA: Cross-sectional area of the thecal sac,\u003c/p\u003e \u003cp\u003eCSF: Cross-sectional foraminal area\u003c/p\u003e \u003cp\u003eVAS: Visual analogue scale\u003c/p\u003e \u003cp\u003eFH: Foraminal height\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eOptimal height changes for successful indirect decompression\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the comparison of the ADH and PDH changes according to degree of indirect decompression up to 1 year. We performed ROC analysis to determine cut off values of parameters that indicate degree of indirect decompression. Immediate postoperative ADH and PDH changes were reliable predictors of indirect decompression according to ROC analysis (AUC\u0026thinsp;=\u0026thinsp;0.654; 0.684, respectively). The 1-year FH improvement positive(+) group, defined as those with greater than 2.21 mm of height increase compared with preoperative value, showed significantly higher ADH and PDH changes (6.46 mm vs. 4.52 mm, p\u0026thinsp;=\u0026thinsp;0.038; 3.59 vs. 2.40, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, respectively). Patients were divided according to CSF values into positive(+) and negative(-) groups (cut-off, 20.12 mm\u003csup\u003e2\u003c/sup\u003e); significant differences of immediate postoperative ADH and PDH changes were observed (6.24 mm vs. 4.55 mm, p\u0026thinsp;=\u0026thinsp;0.043; 3.00 vs. 1.57, P\u0026thinsp;=\u0026thinsp;0.010, respectively). However, the CSA positive(+) and negative(-) groups (cut-off 21.02 mm\u003csup\u003e2\u003c/sup\u003e) did not show significant differences of parameters (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The 1-year subsidence positive(+) group (\u0026gt;\u0026thinsp;2 mm) showed significant differences in immediate PDH increase (4.77 vs. 2.56, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, respectively). Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows pre- and postoperative radiographs of a patient in the 1-year FH positive(+) group.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of parameters between groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eADH increase (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePDH increase (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLeg VAS change\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFH1\u0026nbsp;year(+)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.46\u0026thinsp;\u0026plusmn;\u0026thinsp;6.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.12\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFH1\u0026nbsp;year(-)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.52\u0026thinsp;\u0026plusmn;\u0026thinsp;3.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.40\u0026thinsp;\u0026plusmn;\u0026thinsp;1.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.038\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF(+)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.24\u0026thinsp;\u0026plusmn;\u0026thinsp;6.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.65\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSF(-)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.55\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.57\u0026thinsp;\u0026plusmn;\u0026thinsp;1.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.12\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.043\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.010\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.103\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSA(+)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.26\u0026thinsp;\u0026plusmn;\u0026thinsp;6.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.39\u0026thinsp;\u0026plusmn;\u0026thinsp;1.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCSA(-)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.46\u0026thinsp;\u0026plusmn;\u0026thinsp;3.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.21\u0026thinsp;\u0026plusmn;\u0026thinsp;2.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.19\u0026thinsp;\u0026plusmn;\u0026thinsp;1.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.374\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.584\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.234\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSubsidence(+)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.91\u0026thinsp;\u0026plusmn;\u0026thinsp;2.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.77\u0026thinsp;\u0026plusmn;\u0026thinsp;1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.14\u0026thinsp;\u0026plusmn;\u0026thinsp;1.99\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSubsidence(-)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.50\u0026thinsp;\u0026plusmn;\u0026thinsp;3.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.56\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.96\u0026thinsp;\u0026plusmn;\u0026thinsp;2.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ep\u0026thinsp;=\u0026thinsp;0.553\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003ep\u0026thinsp;=\u0026thinsp;0.011\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eADH increase: Immediate postoperative anterior disc height increase\u003c/p\u003e \u003cp\u003ePDH increase: Immediate postoperative posterior disc height increase\u003c/p\u003e \u003cp\u003eCSA: Cross-sectional area of the thecal sac\u003c/p\u003e \u003cp\u003eCSF: Cross-sectional foraminal area\u003c/p\u003e \u003cp\u003eVAS: Visual analogue scale\u003c/p\u003e \u003cp\u003eFH1\u0026nbsp;year(+): Greater than 2.21 mm of change in foraminal height group\u003c/p\u003e \u003cp\u003eCSF(+): Greater than 20.12 mm\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e of change in CSF group\u003c/p\u003e \u003cp\u003eCSA(+): Greater than 21.02 mm\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e of change in CSA group\u003c/p\u003e \u003cp\u003eSubsidence(+): Greater than 2.00 mm of change in subsidence group\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eOLIF surgery is believed to be efficacious for treatment of mechanical low back pain resulting from disc degeneration, segmental instability, or degenerative scoliosis. OLIF surgery is also considered for leg pain with neurogenic claudication accompanied by mild spinal canal stenosis.(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) Previous studies on OLIF have primarily included single retrospective analysis of oblique lumbar interbody fusion (OLIF) treatment for lumbar spinal stenosis (LSS), comparative studies between OLIF and other surgical methods, and diagnostic analysis through CT or MRI measurements of the dura mater.(\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) In this study, values of the parameters at 1 year after the operation demonstrated varying degrees of increase or decrease compared with the immediate postoperative values, but all were significantly different from baseline. VAS for leg pain improved within 1 week following OLIF surgery, and this was preserved up to 1 year. In addition, with the radiologic improvement of CSA and CSF as well the immediate improvement of radicular symptoms, we suggest that OLIF surgery may offer an advantage in the treatment of radicular pain as well as neurogenic claudication due to spinal canal stenosis. By removing the intervertebral disc in the surgical segment and performing bone grafting and fusion in that segment, followed by implanting an appropriately sized cage to fully restore the intervertebral space in the surgical area, the displaced facet joint is indirectly returned to its normal anatomical position, increasing the foraminal and spinal canal spaces. However, additional direct decompression of bony stenosis and severe ligamentum flavum thickening was needed in some cases. A recent retrospective review of 45 patients (101 levels) reported that bony stenosis at the lateral recess is a predictor of failure of indirect decompression. Although indirect decompression using OLIF can stretch the soft tissue elements that compress the neural element, there may be a limitation of indirect decompression in relieving bony stenosis.(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) However, symptoms can be resolved with a small amount of canal or foramen expansion with indirect decompression, as we reported in our study; thus, most cases including those with a severe degree of canal and foramen stenosis are good candidates for OLIF surgery (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe success of indirect decompression through OLIF surgery depends on many factors. Previous studies on indirect decompression of OLIF reported significant increases in CSA, CSF, and FH postoperatively, which is consistent with the results of the current study (\u003cspan additionalcitationids=\"CR19 CR20 CR21 CR22 CR23\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). In OLIF surgery, a large cage can distract the interbody disc space as well as the posterior vertebral element, including the facet joint, restoring the disc and foraminal heights. Even though regression of the ligamentum flavum has been reported to have a significant role in CSA expansion over long-term follow-up, our results indicate that indirect decompression can also be successfully accomplished immediately with significant improvement in spatial radiological parameters. We found significant increments in ADH, PDH, FH, CSA, and CSF in immediate postoperative radiographs, and these were preserved up to 1 year. This result indicates that OLIF is sufficient to provide good mid-term radiological outcomes in patients with degenerative lumbar stenosis. In addition, the improvement of PDH correlated with improvement of CSF and FH. Immediate postoperative CSA and CSF changes were also significantly correlated with 1 year PDH change (r\u0026thinsp;=\u0026thinsp;0.221, p\u0026thinsp;=\u0026thinsp;0.040; and r\u0026thinsp;=\u0026thinsp;0.162, p\u0026thinsp;=\u0026thinsp;0.016, respectively). Changes of immediate postoperative and 1 year FH were significantly related to 1 year ADH and PDH changes, indicating an effect of indirect decompression on subsidence. Based on these findings, we conclude that sufficient indirect decompression after OLIF surgery can be accomplished in patients with intervertebral disc space narrowing, which can be fully opened and restored by insertion of a large cage. Adversely, direct decompression may be needed for young patients with preserved disc height and severe central canal stenosis. The indications of OLIF are important and significantly affect the success of indirect decompression.\u003c/p\u003e \u003cp\u003eTo achieve successful indirect decompression, it is important to restore posterior disc height while avoiding over-distraction, which may induce postoperative subsidence.(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e) In our study, the 1-year FH improvement positive(+) group showed significantly higher immediate postoperative PDH changes (3.59 vs. 2.40, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The CSF positive(+) group also showed significantly higher immediate postoperative ADH and PDH changes (6.24 mm vs. 4.55 mm, p\u0026thinsp;=\u0026thinsp;0.043; 3.00 vs. 1.57, P\u0026thinsp;=\u0026thinsp;0.010, respectively). Considering the improvement of foraminal height and symptoms, better outcome was expected with a greater than 3.0\u0026ndash;3.6 mm immediate postoperative PDH increase; an increase less than 1.6\u0026ndash;2.4 mm implies a worse outcome. Zeng et al. reported a retrospective analysis of 235 cases of perioperative complications after OLIF. Among these, 22 cases of endplate damage showed a probability of 9.36% and 18 cases of cage subsidence and displacement was a probability of 7.66%, resulting in a combined probability of 17.02%.(\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e) Similarly, Abe et al. found that the most common perioperative complication in their retrospective study of 155 OLIF cases was endplate fracture/subsidence, with a probability of 18.7%.(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) Similarly, the present study observed 18% of cases to have significant subsidence (\u0026gt;\u0026thinsp;2 mm), with a significantly higher immediate PDH increase (4.77 vs. 2.56, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). This indicates the importance of subsidence consideration in OLIF surgery, for which symptoms can be resolved with a small amount of canal or foramen expansion without over-distraction of the disc space. In addition, cages positioned in the middle of the inferior vertebral body had a greater effect on improvement of FH.(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e) Therefore, the factors that significantly affect the improvement of CSF and FH are posterior disc height restoration and a more posterior location of the cage. These results support our hypothesis that the effect of indirect decompression through OLIF surgery might occur through distraction of the middle and posterior vertebral column. These results provide a strong rationale to place the cage in the middle or posteriorly to increase the amount of posterior disc height restoration and the amount of facet distraction for better outcomes after OLIF surgery.\u003c/p\u003e \u003cp\u003eOur study has some limitations. First, this is a small retrospective study that included patients with a wide range of ages. This makes it difficult to accurately reflect the radiologic outcome with respect of the degree of degenerative change. Additionally, the small sample size may limit the reliability of the results. Furthermore, the follow-up observation was limited to 1 year, and longer-term tracking could offer more compelling evidence. Even though we found significant improvement in CSA, CSF, and foraminal height postoperatively, we did not evaluate 1 year postoperative MRI findings, which are as significant as other radiologic outcomes. Further research is required to clarify the minimal clinically important difference in each radiologic parameter for both successful radiological and clinical outcomes following OLIF surgery.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eOLIF provided satisfactory indirect decompression with significant improvement of radiological parameters and symptoms up to 1 year. To achieve successful indirect decompression, restoration of PDH is important, considering improvement of foraminal height and symptoms. Thus, we recommend more than 3.0 mm of PDH increase, avoiding over-distraction, for successful indirect decompression.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eDisclosures: No funds were received in support of this work.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJYH, YJH and JHP wrote the main manuscript.JHP, JWS, JWP designed the study.DHS supervised the main manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\n\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMehren, C., Mayer, H. M., Zandanell, C., Siepe, C. J. \u0026amp; Korge, A. The Oblique Anterolateral Approach to the Lumbar Spine Provides Access to the Lumbar Spine With Few Early Complications. \u003cem\u003eClin. Orthop. Relat. Res.\u003c/em\u003e \u003cb\u003e474\u003c/b\u003e (9), 2020\u0026ndash;2027 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark, J. et al. Minimally Invasive Spine Surgery: Techniques, Technologies, and Indications. \u003cem\u003eAsian Spine J.\u003c/em\u003e \u003cb\u003e14\u003c/b\u003e (5), 694\u0026ndash;701 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMobbs, R. J., Phan, K., Malham, G., Seex, K. \u0026amp; Rao, P. J. Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF. \u003cem\u003eJ. Spine Surg.\u003c/em\u003e \u003cb\u003e1\u003c/b\u003e (1), 2\u0026ndash;18 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShimizu, T., Fujibayashi, S., Otsuki, B., Murata, K. \u0026amp; Matsuda, S. Indirect decompression with lateral interbody fusion for severe degenerative lumbar spinal stenosis: minimum 1-year MRI follow-up. \u003cem\u003eJ. Neurosurg. Spine\u003c/em\u003e ;1\u0026ndash;8. (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLimthongkul, W. et al. Indirect Decompression Effect to Central Canal and Ligamentum Flavum After Extreme Lateral Lumbar Interbody Fusion and Oblique Lumbar Interbody Fusion. \u003cem\u003eSpine (Phila Pa. 1976)\u003c/em\u003e. \u003cb\u003e45\u003c/b\u003e (17), E1077\u0026ndash;E84 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShimizu, T., Fujibayashi, S., Otsuki, B., Murata, K. \u0026amp; Matsuda, S. Indirect decompression via oblique lateral interbody fusion for severe degenerative lumbar spinal stenosis: a comparative study with direct decompression transforaminal/posterior lumbar interbody fusion. \u003cem\u003eSpine J.\u003c/em\u003e \u003cb\u003e21\u003c/b\u003e (6), 963\u0026ndash;971 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOhtori, S. et al. Change of Lumbar Ligamentum Flavum after Indirect Decompression Using Anterior Lumbar Interbody Fusion. \u003cem\u003eAsian Spine J.\u003c/em\u003e \u003cb\u003e11\u003c/b\u003e (1), 105\u0026ndash;112 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMahatthanatrakul, A., Kim, H. S., Lin, G. X. \u0026amp; Kim, J. S. Decreasing thickness and remodeling of ligamentum flavum after oblique lumbar interbody fusion. \u003cem\u003eNeuroradiology\u003c/em\u003e. \u003cb\u003e62\u003c/b\u003e (8), 971\u0026ndash;978 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark, J., Park, S. M., Han, S., Jeon, Y. \u0026amp; Hong, J. Y. Factors affecting successful immediate indirect decompression in oblique lateral interbody fusion in lumbar spinal stenosis patients. \u003cem\u003eN Am. Spine Soc. J.\u003c/em\u003e ;\u003cb\u003e16\u003c/b\u003e. (2023).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, R., Li, X., Zhou, H. \u0026amp; Jiang, W. Development and application of oblique lumbar interbody fusion. \u003cem\u003eOrthop. Surg.\u003c/em\u003e \u003cb\u003e12\u003c/b\u003e (2), 355\u0026ndash;365 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi, H. M., Zhang, R. J. \u0026amp; Shen, C. L. Differences in radiographic and clinical outcomes of oblique lateral interbody fusion and lateral lumbar interbody fusion for degenerative lumbar disease: a meta-analysis. \u003cem\u003eBMC Musculoskelet. Disord\u003c/em\u003e. \u003cb\u003e20\u003c/b\u003e (1), 582 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHung, S. F. et al. Comparison of outcomes between indirect decompression of oblique lumbar interbody fusion and MIS-TLIF in one single-level lumbar spondylosis. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cb\u003e11\u003c/b\u003e (1), 12783 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu, H. F. et al. Comparison of oblique lateral interbody fusion (OLIF) and minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for treatment of lumbar degeneration disease: a prospective cohort study. \u003cem\u003eSpine\u003c/em\u003e. \u003cb\u003e47\u003c/b\u003e (6), E233\u0026ndash;E242 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin, G. X. et al. Clinical and radiologic outcomes of direct versus indirect decompression with lumbar interbody fusion: a matched-pair comparison analysis. \u003cem\u003eWorld Neurosurg.\u003c/em\u003e \u003cb\u003e119\u003c/b\u003e, e898\u0026ndash;909 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang, T. Y. et al. Bony Lateral Recess Stenosis and Other Radiographic Predictors of Failed Indirect Decompression via Extreme Lateral Interbody Fusion: Multi-Institutional Analysis of 101 Consecutive Spinal Levels. \u003cem\u003eWorld Neurosurg.\u003c/em\u003e \u003cb\u003e106\u003c/b\u003e, 819\u0026ndash;826 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGajjar, S., Jhala, A. \u0026amp; Mistry, M. Effectiveness of indirect decompression in severe degenerative lumbar central canal stenosis by oblique lumbar interbody fusion. \u003cem\u003eJ. Minim. Invasive Spine Surg. Tech.\u003c/em\u003e \u003cb\u003e6\u003c/b\u003e (2), 131\u0026ndash;140 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTseng, S. C. et al. Indirect decompression via oblique lumbar interbody fusion is sufficient for treatment of lumbar foraminal stenosis. \u003cem\u003eFront. Surg.\u003c/em\u003e \u003cb\u003e9\u003c/b\u003e, 911514 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin, G. X., Rui, G., Sharma, S., Mahatthanatrakul, A. \u0026amp; Kim, J. S. The correlation of intraoperative distraction of intervertebral disc with the postoperative canal and foramen expansion following oblique lumbar interbody fusion. \u003cem\u003eEur. Spine J.\u003c/em\u003e \u003cb\u003e30\u003c/b\u003e (1), 151\u0026ndash;163 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKepler, C. K. et al. Factors influencing segmental lumbar lordosis after lateral transpsoas interbody fusion. \u003cem\u003eOrthop. Surg.\u003c/em\u003e \u003cb\u003e4\u003c/b\u003e (2), 71\u0026ndash;75 (2012).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePark, S. J. et al. The Ideal Cage Position for Achieving Both Indirect Neural Decompression and Segmental Angle Restoration in Lateral Lumbar Interbody Fusion (LLIF). \u003cem\u003eClin. Spine Surg.\u003c/em\u003e \u003cb\u003e30\u003c/b\u003e (6), E784\u0026ndash;e90 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSato, J. et al. Radiographic evaluation of indirect decompression of mini-open anterior retroperitoneal lumbar interbody fusion: oblique lateral interbody fusion for degenerated lumbar spondylolisthesis. \u003cem\u003eEur. Spine J.\u003c/em\u003e \u003cb\u003e26\u003c/b\u003e (3), 671\u0026ndash;678 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMorita, D. et al. Dynamic changes in the crosssectional area of the dural sac and spinal cord in the thoracic spine. \u003cem\u003eEur. Spine J.\u003c/em\u003e \u003cb\u003e26\u003c/b\u003e (1), 64\u0026ndash;70 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZheng, B. et al. Radiographic analysis of neuroforaminal and central canal decompression following lateral lumbar interbody fusion. \u003cem\u003eN Am. Spine Soc. J.\u003c/em\u003e ;\u003cb\u003e10\u003c/b\u003e. (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKo, S. Correlations between sedimentation sign, dural sac cross-sectional area, and clinical symptoms of degenerative lumbar spinal stenosis. \u003cem\u003eEur. Spine J.\u003c/em\u003e \u003cb\u003e27\u003c/b\u003e (7), 1623\u0026ndash;1628 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng, Z. Y. et al. Complications and prevention strategies of oblique lateral interbody fusion technique. \u003cem\u003eOrthop. Surg.\u003c/em\u003e \u003cb\u003e10\u003c/b\u003e (2), 98\u0026ndash;106 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbe, K. et al. Perioperative complications in 155 patients who underwent oblique lateral interbody fusion surgery: perspectivesand indications from a retrospective multicenter survey. \u003cem\u003eSpine\u003c/em\u003e. \u003cb\u003e42\u003c/b\u003e (1), 55\u0026ndash;62 (2017).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4929751/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4929751/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e \u003cb\u003eStudy design\u003c/b\u003e: Retrospective study.\u003c/p\u003e \u003cp\u003e \u003cb\u003eObjective\u003c/b\u003e: To evaluate the associated factors for successful indirect decompression by assessing the changes in disc height and spinal canal width.\u003c/p\u003e \u003cp\u003e \u003cb\u003eMethods\u003c/b\u003e: This study included 63 patients and 104 involved surgical levels. The efficacy of OLIF for lumbar spinal stenosis on spinal canal and foramen before and after surgery was analyzed up to 1 year. Radiologic parameters were anterior disc height (ADH), posterior disc height (PDH), lumbar lordotic angle (LL), segmental lordotic angle (SL), foraminal height (FH), cross-sectional area (CSA) of the spinal canal, cross-sectional foraminal area (CSF), and subsidence (SD).\u003c/p\u003e \u003cp\u003e \u003cb\u003eResults\u003c/b\u003e: Comparing pre- and postoperative values, the mean CSA and CSF were significantly increased (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). FH increased from 15.23\u0026thinsp;\u0026plusmn;\u0026thinsp;3.48 mm to 18.78\u0026thinsp;\u0026plusmn;\u0026thinsp;2.93 mm and was stable for up to 1 year (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). The VAS leg and ODI scores significantly improved after surgery (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Changes of immediate postoperative and 1-year FH were significantly related to 1 year ADH, PDH, and VAS leg changes (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The group showing 1-year FH improvement (positive(+) group) demonstrated significantly larger immediate postoperative ADH and PDH changes compared with the FH negative(-) group (6.46 mm vs. 4.52 mm, p\u0026thinsp;=\u0026thinsp;0.038; 3.59 vs. 2.40, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001, respectively). The CSF positive(+) group also showed significantly higher immediate postoperative ADH and PDH changes (6.24 mm vs. 4.55 mm, p\u0026thinsp;=\u0026thinsp;0.043; 3.00 vs. 1.57, P\u0026thinsp;=\u0026thinsp;0.010, respectively).\u003c/p\u003e \u003cp\u003eConclusions\u003c/p\u003e \u003cp\u003eOLIF provided satisfactory indirect decompression up to 1 year. Considering the increase of foraminal height, we recommend more than 3.0 mm of immediate postoperative PDH increase, avoiding over-distraction of disc space.\u003c/p\u003e","manuscriptTitle":"What are the optimal disc height changes for successful indirect decompression with OLIF? \nAnalysis of pre- and postoperative parameter changes up to 1 year","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-16 06:54:09","doi":"10.21203/rs.3.rs-4929751/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-31T15:37:31+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-03-27T18:43:22+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"130647474016535392493522010627355324781","date":"2025-03-12T12:47:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-07T19:11:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"30152830265485675465266467754187286686","date":"2025-01-23T08:21:19+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-12-07T12:06:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"24051644774578121755271317479401891402","date":"2024-11-28T12:29:17+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-28T11:29:57+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-11-27T08:18:44+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-08-23T09:34:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-23T03:59:38+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-08-17T12:16:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a23d57d7-b6cb-4a47-ab06-7f472444a01e","owner":[],"postedDate":"October 16th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":38080764,"name":"Health sciences/Rheumatology/Musculoskeletal system"},{"id":38080765,"name":"Health sciences/Medical research/Outcomes research"}],"tags":[],"updatedAt":"2025-07-07T16:13:16+00:00","versionOfRecord":{"articleIdentity":"rs-4929751","link":"https://doi.org/10.1038/s41598-025-05562-4","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-07-01 15:58:36","publishedOnDateReadable":"July 1st, 2025"},"versionCreatedAt":"2024-10-16 06:54:09","video":"","vorDoi":"10.1038/s41598-025-05562-4","vorDoiUrl":"https://doi.org/10.1038/s41598-025-05562-4","workflowStages":[]},"version":"v1","identity":"rs-4929751","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4929751","identity":"rs-4929751","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}