Demands on Posterior Fusion Hardware During Lordosis Restoration Procedures

2013 ◽  
Author(s):  
Audrey Martin ◽  
Connor Telles ◽  
Jeremi Leasure ◽  
Jessica Tang ◽  
Christopher Ames ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Sagittal Alignment ◽  
Critical Role ◽  
Biomechanical Study ◽  
Posterior Fusion ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Comparative Performance ◽  
Lower Lumbar

Lower lumbar lordosis plays a critical role in sagittal alignment. It has been shown that restoration of lumbar lordosis in patients with preoperative sagittal imbalance is necessary to prevent postoperative sagittal decompensation [1]. Further, restoration of lower lumbar lordosis in patients with degenerative flatback syndrome has been shown clinically to result in additional correction of the thoracic curve and sacral slope [2]. Currently, there are three commonly used intraoperative techniques to restore lumbar lordosis: (1) cantilever bending, (2) in situ bending, and (3) compression and/or distraction of screws along posterior fusion rods. Although powerful, all three techniques require the surgeon to impart large forces to the accompanying posterior fusion hardware, often causing failure of hardware and inconsistency to achieve pre-operatively planned lordosis. To date, there has been no clinical or biomechanical study to address the comparative performance of these three techniques. In efforts to determine a standard of care for sagittal alignment via lumbar lordosis restoration, the goal of this study is to establish a relation between the three techniques, and the resulting demands on posterior fusion hardware. It is hypothesized that greater loads will be observed in the hardware during in situ bending, increasing the risk of pedicle screw pullout.

Changes in sagittal alignment after restoration of lower lumbar lordosis in patients with degenerative flat back syndrome

2007 ◽  
Vol 7 (4) ◽  
pp. 387-392 ◽  
Author(s):  
Jee-Soo Jang ◽  
Sang-Ho Lee ◽  
Jun-Hong Min ◽  
Dae Hyeon Maeng
Keyword(s):  
Lumbar Lordosis ◽  
Thoracic Kyphosis ◽  
Sagittal Alignment ◽  
Plumb Line ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Spontaneous Correction ◽  
Flat Back ◽  
Lower Lumbar

Object The authors investigate the correlation between thoracic and lumbar curves in patients with degenerative flat back syndrome, and demonstrate the predictability of spontaneous correction of the thoracic curve and sacral angle after surgical restoration of lower lumbar lordosis. Methods The cases of 28 patients treated with combined anterior and posterior spinal arthrodesis were retrospectively reviewed. Inclusion criteria included loss of lower lumbar lordosis resulting in sagittal imbalance. Total lumbar lordosis, thoracic kyphosis, sacral slope, and C-7 plumb line length were measured on pre- and postoperative lateral views of the whole spine. Postoperative changes in thoracic kyphosis, sacral slope, and length of the C-7 plumb line were measured and evaluated according to extent of lumbar lordosis restoration. Results The mean (± standard deviation) preoperative sagittal imbalance was 64.6 ± 63.2 mm, which improved to 15.8 ± 20.7 mm after surgery (p < 0.0001). The preoperative mean lumbar lordosis was 15.6 ± 14.1°, which increased to 40.3 ± 14.5° at follow-up (p < 0.0001). The preoperative mean thoracic kyphosis was 1.6 ± 10.5° and increased to 17.2 ± 12.5° at follow-up (p < 0.0001). Significant preoperative correlations existed between kyphosis and lordosis (r = 0.628, p = 0.0003), and between lordosis and sacral slope (r = 0.647, p = 0.0002). Postoperative correlations also existed between kyphosis and lordosis (r = 0.718, p < 0.0001 and r = 0.690, p < 0.0001, respectively). Conclusions Lower lumbar lordosis plays an important role in sagittal alignment and balance. Surgical restoration of lumbar lordosis results in predictable spontaneous correction of the thoracic curve and sacral slope in patients with degenerative flat back syndrome.

Implications of Spinopelvic Alignment for the Spine Surgeon

Neurosurgery ◽  
2011 ◽  
Vol 70 (3) ◽  
pp. 707-721 ◽  
Author(s):  
Vivek A. Mehta ◽  
Anubhav Amin ◽  
Ibrahim Omeis ◽  
Ziya L. Gokaslan ◽  
Oren N. Gottfried
Keyword(s):  
Sagittal Balance ◽  
Lumbar Lordosis ◽  
Pelvic Incidence ◽  
Degenerative Spondylolisthesis ◽  
Disease Process ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Spinopelvic Parameters ◽  
Spinopelvic Alignment ◽  
Spinopelvic Balance

Abstract The relation of the pelvis to the spine has previously been overlooked as a contributor to sagittal balance. However, it is now recognized that spinopelvic alignment is important to maintain an energy-efficient posture in normal and disease states. The pelvis is characterized by an important anatomic landmark, the pelvic incidence (PI). The PI does not change after adolescence, and it directly influences pelvic alignment, including the parameters of pelvic tilt (PT) and sacral slope (SS) (PI = PT 1 SS), overall sagittal spinal balance, and lumbar lordosis. In the setting of an elevated PI, the spineadapts with increased lumbar lordosis. To prevent or limit sagittal imbalance, the spine may also compensate with increased PT or pelvic retroversion to attempt to maintain anupright posture. Abnormal spinopelvic parameters contribute to multiple spinal conditions including isthmic spondylolysis, degenerative spondylolisthesis, deformity, and impact outcome after spinal fusion. Sagittal balance, pelvic incidence, and all spinopelvic parameters are easily and reliably measured on standing, full-spine (lateral) radiographs, and it is essential to accurately assess and measure these sagittal values to understand their potential role in the disease process, and to promote spinopelvic balance at surgery. In this article, we provide a comprehensive review of the literature regarding the implications of abnormal spinopelvic parameters and discuss surgical strategies for correction of sagittal balance. Additionally, the authors rate and critique the quality of the literature cited in a systematic review approach to give the reader an estimate of the veracity of the conclusions reached from these reports.

Implications of Spinopelvic Alignment for the Spine Surgeon

Neurosurgery ◽  
2011 ◽  
Vol 76 (suppl_1) ◽  
pp. S42-S56 ◽  
Author(s):  
Vivek A. Mehta ◽  
Anubhav Amin ◽  
Ibrahim Omeis ◽  
Ziya L. Gokaslan ◽  
Oren N. Gottfried
Keyword(s):  
Sagittal Balance ◽  
Lumbar Lordosis ◽  
Pelvic Incidence ◽  
Degenerative Spondylolisthesis ◽  
Disease Process ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Spinopelvic Parameters ◽  
Spinopelvic Alignment ◽  
Spinopelvic Balance

Abstract The relation of the pelvis to the spine has previously been overlooked as a contributor to sagittal balance. However, it is now recognized that spinopelvic alignment is important to maintain an energy-efficient posture in normal and disease states. The pelvis is characterized by an important anatomic landmark, the pelvic incidence (PI). The PI does not change after adolescence, and it directly influences pelvic alignment, including the parameters of pelvic tilt (PT) and sacral slope (SS) (PI = PT 1 SS), overall sagittal spinal balance, and lumbar lordosis. In the setting of an elevated PI, the spineadapts with increased lumbar lordosis. To prevent or limit sagittal imbalance, the spine may also compensate with increased PT or pelvic retroversion to attempt to maintain anupright posture. Abnormal spinopelvic parameters contribute to multiple spinal conditions including isthmic spondylolysis, degenerative spondylolisthesis, deformity, and impact outcome after spinal fusion. Sagittal balance, pelvic incidence, and all spinopelvic parameters are easily and reliably measured on standing, full-spine (lateral) radiographs, and it is essential to accurately assess and measure these sagittal values to understand their potential role in the disease process, and to promote spinopelvic balance at surgery. In this article, we provide a comprehensive review of the literature regarding the implications of abnormal spinopelvic parameters and discuss surgical strategies for correction of sagittal balance. Additionally, the authors rate and critique the quality of the literature cited in a systematic review approach to give the reader an estimate of the veracity of the conclusions reached from these reports.

scholarly journals Correlation between lumbar sagittal alignment, Modic changes, and endplate erosion in patients with degenerative disease

2020 ◽  
Author(s):  
Bin Lv ◽  
Haosheng Wang
Keyword(s):  
Lumbar Lordosis ◽  
Sagittal Alignment ◽  
Modic Changes ◽  
Degenerative Disease ◽  
Defect Group ◽  
Sacral Slope ◽  
Precise Understanding ◽  
Significant Difference ◽  
Before And After ◽  
Operation Results

Abstract Purpose To explore the role of lumbar sagittal alignment in the occurrence of Modicchanges and endplate defects (MC&ED) development in patients with a spinal degenerative disease, and the relationship between lumbar sagittal alignment and patient-report outcomes. Background Increasing attention has been focused on MC&ED as playing a potential role in the etiopathogenesis of lumbar degeneration. The precise understanding of the mechanisms leading to progression of MC&ED is lacking. Hence, we investigated how lumbar sagittal alignment influences the MC&ED. Patients and methods Ninety-six consecutive asymptomatic or symptomatic patients with Modic changes or endplate defect were retrospectively recruited in this study from August 2016 to December 2018. MC&ED were observed in 76 patients and not observed in 20 patients, representing two groups for comparison. The lumbar sagittal parameters were measured, including lumbar lordosis (LL),pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT). The lumbar lordosis index (LLI) and idea LL were then calculated. Clinical outcomes were assessed using a visual analog scale(VAS) and a Oswestry Disability Index (ODI) before and after operation. Results There were no significant differences in the distribution of demographics and baseline clinical variables between both groups. Mean age and BMI showed a significant difference between both groups (P<0.05). There were significant correlations between LL, LLI, Lossof LL, and Level 1 (r=0.281, 0.230, and 0.284, P<0.05) Also, PI, PT were significantly correlated with Level 4 (r=0.249, 0.202, P<0.05).Compared with presurgery scores, an improvement was seen in postoperative VAS and ODI scores (P<0.05). Further, the postoperative scores at 24 months in the without Modicor end plate defect group showed greater improvements compared with the with Modic or endplate defect group (P<0.05). Conclusion This analysis indicated that maintaining lumbar sagittal alignment was related to a lower risk of Modic changes in patients with the spinal degenerative disease. The lumbar sagittal alignment might be a factor that influenced the posterior inclination of the pelvis in symptomatic lumbar disease.

scholarly journals Clinical Outcomes of S2 Alar-Iliac (S2AI) Screw Technique in The Treatment of Severe Spinal Sagittal Imbalance: A Retrospective 2-Year Follow-Up Study

2021 ◽  
Author(s):  
Yao Zhao ◽  
Beiyu Xu ◽  
Longtao Qi ◽  
Chunde Li ◽  
Zhengrong Yu ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Adult Spinal Deformity ◽  
Pearson Correlation ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Global Alignment ◽  
Mechanical Complications ◽  
Group A ◽  
Group B

Abstract Background The treatment of adult spinal deformity (ASD) remains a significant challenge, especially in elderly patients. This study aimed to evaluate the outcomes of the S2AI screw technique in the treatment of severe spinal sagittal imbalance with a minimum 2-year follow-up. Methods From January 2015 to December 2018, 23 patients with severe degenerative thoracolumbar kyphosis who underwent placement of S2AI screws for long segment fusion were retrospectively reviewed. Patients were divided into group A (no mechanical complications, 13 cases) and group B (with mechanical complications, 10 cases) according to the occurrence of mechanical complications at the last follow-up. Radiographic parameters were compared between groups preoperatively, 1 month postoperatively, and at the last follow-up. Risk factors for mechanical complications were analyzed. Results The incidence of mechanical complications was 43.5%, and the revision rate was 17.4%. At 1 month postoperatively, sagittal correction was better in group A than in group B (P<0.05). The lumbar lordosis (LL), pelvic incidence minus lumbar lordosis (PI-LL), T1 pelvic angle (TPA), and sagittal vertical axis (SVA) of both groups at the last follow-up were significantly different from corresponding values at 1 month postoperatively (P<0.05), and the sagittal correction was partially lost. Pearson correlation analysis revealed that the occurrence of mechanical complications was associated with sacral slope (SS), LL, PI-LL, and global alignment and proportion (GAP) score at 1 month postoperatively. Conclusion A high incidence of mechanical complications was observed in long-segment corrective surgery with the S2AI screw technique for severe spinal sagittal imbalance. Inadequate sagittal correction is a risk factor for the development of mechanical complications.

Spinopelvic Sagittal Alignment after Microendoscopic Laminotomy in Patients with Lumbar Degenerative Spondylolisthesis

2018 ◽  
Vol 79 (06) ◽  
pp. 479-485
Author(s):  
Sho Dohzono ◽  
Yusuke Hori ◽  
Shinji Takahashi ◽  
Akinobu Suzuki ◽  
Hidetomi Terai ◽  
...  
Keyword(s):  
Sagittal Alignment ◽  
Degenerative Spondylolisthesis ◽  
Group Versus ◽  
Leg Pain ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Low Grade ◽  
Spinopelvic Parameters ◽  
Spinal Sagittal Alignment ◽  
Global Sagittal Alignment

Background and Study Aims Spinopelvic sagittal balance is important in managing lumbar diseases. We evaluated the change in spinal sagittal alignment after microendoscopic laminotomy in patients with low-grade degenerative spondylolisthesis (DS). Material and Methods We retrospectively reviewed the records of 87 patients who underwent microendoscopic laminotomy. We enrolled 35 patients with DS and 52 patients without DS. Spinopelvic parameters were evaluated, including the sagittal vertical axis (SVA), lumbar lordosis (LL), sacral slope, pelvic tilt, and pelvic incidence (PI). Primary outcome was a change in spinopelvic alignment between the baseline and latest follow-up values (DS group versus non-DS group). Secondary outcomes were the relationships between improved global sagittal alignment and preoperative spinopelvic parameters. Results Both groups showed significantly alleviated low back pain (LBP), leg pain, and leg numbness. Preoperative SVA and PI were significantly higher in the DS group than in the non-DS group (p < 0.05). SVA significantly decreased and LL significantly increased in the DS group (p < 0.05), whereas those parameters did not differ significantly from before versus after surgery in the non-DS group. In both groups, SVA improvement correlated significantly with preoperative SVA (DS: r = 0.702; non-DS: r = 0.397). There was also a significant intergroup difference in the correlation coefficient (z = 1.98; r = 0.048). Conclusions SVA and LL significantly improved after microscopic laminotomy in patients with low-grade DS and neurologic symptoms. SVA improvement in the DS group was correlated with preoperative spinopelvic sagittal imbalance. The strength of those correlations was greater in the DS group than in the non-DS group.

scholarly journals Lumbar Sagittal Alignment May Be a Good Predictor for the Lumbar Spine Degeneration

2020 ◽  
Author(s):  
Xingping Xu ◽  
Chao Guo ◽  
Changwei Chen ◽  
Yong Tang ◽  
Fusheng Wang ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Influence Factor ◽  
Sagittal Alignment ◽  
Modic Changes ◽  
Defect Group ◽  
Sacral Slope ◽  
End Plate ◽  
Significant Difference ◽  
Before And After ◽  
Spine Degeneration

Abstract BackgroundIncreasing attention has been focused on (modic changes and end plate defect) MC&ED as a potential role in the etiopathogenesis of lumbar degeneration. The precise mechanism leading to progression of MC&ED is lacking. Some scholars thought lumbar sagittal alignment might be a key influence factor, but without enough clinical evidence. Hence, we investigated how lumbar sagittal alignment influences MC&ED.MethodsNinety-six asymptomatic or symptomatic patients with Modic changes or end plate defect were retrospectively recruited in this study from August 2016 to December 2018. MC&ED were observed in 76 patients and not observed in 20 patients, representing two groups for comparison. The lumbar sagittal parameters were measured, including lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT). The lumbar lordosis index(LLI) and idea LL were then calculated. Clinical outcomes were assessed using a visual analog scale(VAS) and an Oswestry Disability Index (ODI) before and after an operation.ResultsThere were no significant difference in the distribution of demographic and baseline clinical variables between both groups. Mean age and BMI showed significant difference between both groups (P < 0.05). There were significant correlations between LL, LLI, Loss of LL, and Level 1 (r = 0.281, 0.230, and 0.284, P < 0.05) Also, PI, PT were significantly correlated with Level 4 (r = 0.249, 0.202, P < 0.05). Compared with presurgery scores, an improvement was seen in postoperative VAS and ODI scores (P < 0.05). Further, the postoperative scores at 24 months in the without Modic or end plate defect group showed greater improvements compared with the with Modic or endplate defect group (P < 0.05).ConclusionThis analysis indicated that maintaining lumbar sagittal alignment was related to a lower risk of Modic changes in patients with the spinal degenerative disease. The lumbar sagittal alignment might be a factor that influenced the posterior inclination of the pelvis in symptomatic lumbar disease.

Two different types of postoperative sagittal imbalance after long instrumented fusion to the sacrum for degenerative sagittal imbalance

2020 ◽  
Vol 33 (5) ◽  
pp. 613-622
Author(s):  
Hyung-Youl Park ◽  
Young-Hoon Kim ◽  
Sang-Il Kim ◽  
Sung-Bin Han ◽  
Kee-Yong Ha
Keyword(s):  
Risk Factors ◽  
Sagittal Alignment ◽  
Sacral Slope ◽  
Sagittal Imbalance ◽  
Instrumented Fusion ◽  
Radiographic Measurements ◽  
Paravertebral Muscles ◽  
Different Types ◽  
Fatty Atrophy ◽  
Whole Spine

OBJECTIVEFew studies have addressed that dynamic sagittal imbalance can develop distal to the spinal fusion and cause sagittal malalignment, unlike proximal junctional kyphosis (PJK) in the proximal portion. The purpose of this study was to investigate risk factors between the 2 different types of postoperative sagittal imbalance after long fusion to the sacrum for the treatment of degenerative sagittal imbalance (DSI).METHODSEighty patients who had undergone surgical correction for DSI were included. Radiographic measurements included spinopelvic parameters on whole-spine plain radiographs and degeneration of paravertebral muscles on MRI. Univariate and multivariate analyses for clinical and radiological factors were conducted for respective risk factors. In subgroup analyses, the 2 different types of postoperative sagittal imbalance were directly compared.RESULTSForty patients (50%) developed postoperative sagittal imbalance; of these patients, 22 (55.0%) developed static proximal kyphosis from PJK, and 18 patients (45.0%) developed dynamic sagittal imbalance without PJK. The independent risk factors in proximal kyphosis were greater postoperative pelvic tilt (HR 1.11) and less change in sacral slope (SS) (HR 1.09), whereas there were more fusion levels (HR 3.11), less change in SS (HR 1.28), and less change in thoracic kyphosis (HR 1.26) in dynamic sagittal imbalance. Directly compared with the proximal kyphosis group, dynamic sagittal imbalance was more commonly found in patients who had less correction of sagittal parameters as well as fatty atrophy of the paravertebral muscles. Clinical outcomes in the dynamic sagittal imbalance group were superior to those in the proximal kyphosis group.CONCLUSIONSOptimal correction of sagittal alignment should be considered in long instrumented fusion for DSI, because insufficient correction might cause one of 2 different types of postoperative sagittal imbalance at different sites of decompression. Dynamic sagittal imbalance compared with proximal kyphosis was significantly associated with less correction of sagittal alignment, in conjunction with more fusion levels and degeneration of the paravertebral muscles.

scholarly journals Analysis of global spine sagittal parameters in cervical spondylotic patients and asymptomatic subjects

2020 ◽  
Author(s):  
Liang Zhu ◽  
Xiaojun Ma ◽  
Qiang Shen ◽  
Bao Sun ◽  
Qiang Fu
Keyword(s):  
Cervical Spondylosis ◽  
Lumbar Lordosis ◽  
Sagittal Alignment ◽  
Vertical Axis ◽  
Normal Group ◽  
Sacral Slope ◽  
Sagittal Vertical Axis ◽  
Thoracic Inlet ◽  
Global Sagittal Alignment ◽  
Sagittal Parameters

Abstract Background: Degenerative changes associated with cervical spondylotic can result in a change of normal sagittal alignment, and this may be the initial change of kyphosis and sagittal imbalance. Few studies have analyzed the correlations between the cervical spine lordosis and global spine balance in patients with cervical spondylotic. This study is applied to investigate the characteristics and relationships of cervical and global sagittal parameters in normal adults and cervical spondylotic patients. Methods: We reviewed 46 asymptomatic control subjects (normal group, NG) and 48 cervical spondylotic patients (cervical spondylotic group, CSG), who had both cervical MRI and global radiographs obtained together, between January 2016 and September 2018. Data includes C1-2 angle, C2–7 lordosis (CL), T1 slope (T1S), thoracic inlet angle (TIA), C2–7 sagittal vertical axis (CSVA), sagittal vertical axis(SVA), thoracic-kyphosis(TK), thoracic-lumbar lordosis(TL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). The values were presented as the mean ± standard deviation. Student t-test and Pearson’s correlation coefficient were used for statistical analysis. Probability values less than 0.05 were considered statistically significant. Results: 1.Comparison of global sagittal parameters between the normal group and cervical spondylosis group. A total of 48 cervical spondylotic patients with an average age of 57.91±9.58 and 46 healthy people with an average age of 28.00±8.09 were recruited in our study. CL in the NG was significantly lower than CSG (P<0.05), while TK and TL were significantly lower than in the CSG(P< 0.01). However, a comparison of the NG and CSG yielded no significant differences in C1-2, TIA, TIS, LL, PT, PI, SS, CSVA, and SVA. 2.The relationship between cervical and global sagittal alignment. CL positively correlated with T1S (r=0.433) and TK (r=0.335) while negatively correlated with CSVA (r=-0.309) in cervical spondylosis group. TIA has positively correlated with T1S (r=0.376 in NG and r=0.416 in CSG) and no correlated with other parameters in both groups. Conclusions Cervical spondylosis causes changes in sagittal parameters of the cervical and thoracic spine but does not affect on lumbar and pelvic parameters. TIA is a relative constant parameter, not affected by cervical spondylotic.

scholarly journals A Preliminary Algorithm Using Spine Measurement Software to Predict Sagittal Alignment Following Pedicle Subtraction Osteotomy

2017 ◽  
Vol 7 (6) ◽  
pp. 543-551
Author(s):  
Robert K. Merrill ◽  
Jun S. Kim ◽  
Dante M. Leven ◽  
Joshua J. Meaike ◽  
Joung Heon Kim ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Sagittal Alignment ◽  
Adult Spinal Deformity ◽  
Case Series ◽  
Pedicle Subtraction Osteotomy ◽  
Regression Equation ◽  
Sacral Slope ◽  
Pelvic Inclination ◽  
Manual Rotation ◽  
Measurement Software

Study Design: Retrospective case series. Objective: To evaluate if spine measurement software can simulate sagittal alignment following pedicle subtraction osteotomy (PSO). Methods: We retrospectively reviewed consecutive adult spinal deformity patients who underwent lumbar PSO. Sagittal measurements were performed on preoperative lateral, standing radiographs. Sagittal measurements after simulated PSO were compared to actual postoperative measurements. A regression equation was developed using cases 1-7 to determine the amount of manual rotation required of each film to match the simulated sagittal vertical axis (SVA) to the actual postoperative SVA. The equation was then applied to cases 8-13. Results: For all 13 cases, the spine software accurately simulated lumbar lordosis, pelvic incidence lumbar lordosis mismatch, and T1 pelvic angle, with no significant differences between actual and simulated measurements. The pelvic tilt (PT), sacral slope (SS), thoracolumbar alignment (TL), thoracic kyphosis (TK), T9 spino-pelvic inclination (T9SPi), T1 spino-pelvic inclination (T1SPi), and SVA were inaccurately simulated. The PT, SS, T9SPi, T1SPi, and SVA all change with manual rotation of the film, and by using the regression equation developed with cases 1-7, we were able to improve the accuracy and decrease the variability of the simulated PT, SS, T9SPi, T1SPi, and SVA for cases 8-13. Conclusions: Dedicated spine measurement software can accurately simulate certain sagittal measurements, such as LL, PI-LL, and TPA, following PSO. A number of measurements, including PT, SS, TL, TK, T9SPi, T1SPi, and SVA were inaccurately simulated. Our preliminary algorithm improved the accuracy and decreased the variability of certain measurements, but requires future prospective studies for further validation.

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