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

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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Lumbar Level Significantly Influences Postoperative Global Sagittal Balance Following Pedicle Subtraction Osteotomy

Global Spine Journal ◽

10.1177/21925682211032563 ◽

2021 ◽

pp. 219256822110325

Author(s):

Athan G. Zavras ◽

T. Barrett Sullivan ◽

Navya Dandu ◽

Howard S. An ◽

Christopher J. DeWald ◽

...

Keyword(s):

Sagittal Balance ◽

Sagittal Alignment ◽

Adult Spinal Deformity ◽

Vertical Axis ◽

Pedicle Subtraction Osteotomy ◽

Current Evidence ◽

Sacral Slope ◽

Sagittal Vertical Axis ◽

Lumbar Level ◽

Global Sagittal Alignment

Study Design: Retrospective cohort study. Objectives: The current evidence regarding how level of lumbar pedicle subtraction osteotomy (PSO) influences correction of sagittal alignment is limited. This study sought to investigate the relationship of lumbar level and segmental angular change (SAC) of PSO with the magnitude of global sagittal alignment correction. Methods: This study retrospectively evaluated 53 consecutive patients with adult spinal deformity who underwent lumbar PSO at a single institution. Radiographs were evaluated to quantify the effect of PSO on lumbar lordosis (LL), thoracic kyphosis (TK), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), T1-spinopelvic inclination (T1SPI), T1-pelvic alignment (TPA), and sagittal vertical axis (SVA). Results: Significant correlations were found between PSO SAC and the postoperative increase in LL ( r = 0.316, P = .021) and PT ( r = 0.352, P = .010), and a decrease in TPA ( r = −0.324, P = .018). PSO level significantly correlated with change in T1SPI ( r = −0.305, P = .026) and SVA ( r = −0.406, P = .002), with more caudal PSO corresponding to a greater correction in sagittal balance. On multivariate analysis, more caudal PSO level independently predicted a greater reduction in T1SPI (β = −3.138, P = .009) and SVA (β = −29.030, P = .001), while larger PSO SAC (β = −0.375, P = .045) and a greater number of fusion levels (β = −1.427, P = .036) predicted a greater reduction in TPA. Conclusion: This study identified a gain of approximately 3 degrees and 3 cm of correction for each level of PSO more caudal to L1. Additionally, a larger PSO SAC predicted greater improvement in TPA. While further investigation of these relationships is warranted, these findings may help guide preoperative PSO level selection.

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Sacral incidence to pubis: a novel and alternative morphologic radiological parameter to pelvic incidence in assessing spinopelvic sagittal alignment

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-04093-z ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Yasuhito Takahashi ◽

Kei Watanabe ◽

Masashi Okamoto ◽

Shun Hatsushikano ◽

Kazuhiro Hasegawa ◽

...

Keyword(s):

Correlation Coefficient ◽

Pelvic Incidence ◽

Sagittal Alignment ◽

Intraclass Correlation ◽

Hip Dislocation ◽

Standing Position ◽

Regression Equation ◽

Whole Body ◽

Spinopelvic Parameters ◽

Pelvic Inclination

Abstract Background Although pelvic incidence (PI) is a key morphologic parameter in assessing spinopelvic sagittal alignment, accurate measurements of PI become difficult in patients with severe hip dislocation or femoral head deformities. This study aimed to investigate the reliability of our novel morphologic parameters and the correlations with established sagittal spinopelvic parameters. Methods One hundred healthy volunteers (25 male and 75 female), with an average age of 38.9 years, were analysed. Whole-body alignment in the standing position was measured using a slot-scanning X-ray imager. We measured the established spinopelvic sagittal parameters and a novel parameter: the sacral incidence to pubis (SIP). The correlation coefficient of each parameter, regression equation of PI using SIP, and regression equation of lumbar lordosis (LL) using PI or SIP were obtained. The intraclass correlation coefficient (ICC) was calculated as an evaluation of the measurement reliability. Results Reliability analysis showed high intra- and inter-rater agreements in all the spinopelvic parameters, with ICCs > 0.9. The SIP and pelvic inclination angle (PIA) demonstrated strong correlation with PI (R = 0.96) and pelvic tilt (PT) (R = 0.92). PI could be predicted according to the regression equation: PI = − 9.92 + 0.905 * SIP (R = 0.9596, p < 0.0001). The ideal LL could be predicted using the following equation using PI and age: ideal LL = 32.33 + 0.623 * PI – 0.280 * age (R = 0.6033, p < 0.001) and using SIP and age: ideal LL = 24.29 + 0.609 * SIP – 0.309 * age (R = 0.6177, p < 0.001). Conclusions Both SIP and PIA were reliable parameters for determining the morphology and orientation of the pelvis, respectively. Ideal LL was accurately predicted using the SIP with equal accuracy as the PI. Our findings will assist clinicians in the assessment of spinopelvic sagittal alignment. Trial registration This study was retrospectively registered with the UMIN Clinical Trials Registry (UMIN000042979; January 13, 2021).

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Usefulness of anterior column release for segmental lordosis restoration in degenerative lumbar kyphosis

Journal of Neurosurgery Spine ◽

10.3171/2021.5.spine202196 ◽

2021 ◽

pp. 1-7

Author(s):

Jin-Sung Park ◽

Chong-Suh Lee ◽

Youn-Taek Choi ◽

Se-Jun Park

Keyword(s):

Sagittal Alignment ◽

Adult Spinal Deformity ◽

Anterior Column ◽

Sacral Slope ◽

High Morbidity ◽

Global Sagittal Alignment ◽

The Mean ◽

Lumbar Kyphosis ◽

Segmental Lordosis

OBJECTIVE Three-column osteotomies (3COs) for surgical correction of lumbar kyphosis show a strong correction capacity, but this procedure carries high morbidity rates. The anterior column release (ACR) technique was developed as a less invasive procedure. In this study the authors aimed to evaluate sagittal alignment restoration using ACR and to determine factors that affect the degree of correction. METHODS This study included 36 patients (68 cases) who underwent ACR of more than one level for adult spinal deformity. Parameters for regional sagittal alignment included segmental lordosis (SL). The parameters for global sagittal alignment included pelvic incidence, lumbar lordosis, sacral slope, pelvic tilt, and sagittal vertical axis (SVA). In addition, the interdiscal height (IDH) and difference of interdiscal angle (DIDA) were measured to evaluate the stiffness of the vertebra segment. The changes in SL were evaluated after ACR and the change of global sagittal alignment was also determined. Factors such as the location of the ACR level, IDH, DIDA, cage height, and additional posterior column osteotomy (PCO) were analyzed for correlation with the degree of SL correction. RESULTS Thirty-six patients were included in this study. A total of 68 levels were operated with the ACR (8 levels at L2–3, 27 levels at L3–4, and 33 levels at L4–5). ACR was performed for 1 level in 10 patients, 2 levels in 20, and 3 levels in 6 patients (mean 1.9 ± 0.7 levels per patient). Mean follow-up duration was 27.1 ± 4.2 months. The mean SL of the total segment was 0.4° ± 7.2° preoperatively and increased by 15.3° ± 5.5° at the last follow-up (p < 0.001); thus, the mean increase of SL was 14.9° ± 8.1° per one ACR. Global sagittal alignment was also improved following SL restoration with SVA from 101.9 mm to 31.4 mm. The degree of SL correction was correlated with the location of ACR level (p = 0.041) and was not correlated with IDH, DIDA, cage height and additional PCO. CONCLUSIONS This study demonstrated that the mean correction angle of SL was 14.9 per one ACR. The degree of disc space collapse and stiffness of segment did not affect the degree of correction by ACR.

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Sacral incidence to pubis: a novel and alternative morphologic radiological parameter to pelvic incidence in assessing spinopelvic sagittal alignment

10.21203/rs.3.rs-20179/v3 ◽

2021 ◽

Author(s):

Yasuhito Takahashi ◽

Kei Watanabe ◽

Masashi Okamoto ◽

Shun Hatsushikano ◽

Kazuhiro Hasegawa ◽

...

Keyword(s):

Correlation Coefficient ◽

Pelvic Incidence ◽

Sagittal Alignment ◽

Intraclass Correlation ◽

Hip Dislocation ◽

Standing Position ◽

Regression Equation ◽

Whole Body ◽

Spinopelvic Parameters ◽

Pelvic Inclination

Abstract Background: Although pelvic incidence (PI) is a key morphologic parameter in assessing spinopelvic sagittal alignment, accurate measurements of PI become difficult in patients with severe hip dislocation or femoral head deformities. This study aimed to investigate the reliability of our novel morphologic parameters and the correlations with established sagittal spinopelvic parameters. Methods: One hundred healthy volunteers (25 male and 75 female), with an average age of 38.9 years, were analysed. Whole-body alignment in the standing position was measured using a slot-scanning X-ray imager. We measured the established spinopelvic sagittal parameters and a novel parameter: the sacral incidence to pubis (SIP). The correlation coefficient of each parameter, regression equation of PI using SIP, and regression equation of lumbar lordosis (LL) using PI or SIP were obtained. The intraclass correlation coefficient (ICC) was calculated as an evaluation of the measurement reliability. Results: Reliability analysis showed high intra- and inter-rater agreements in all the spinopelvic parameters, with ICCs > 0.9. The SIP and pelvic inclination angle (PIA) demonstrated strong correlation with PI ( R = 0.96) and pelvic tilt (PT) ( R = 0.92). PI could be predicted according to the regression equation: PI = –9.92 + 0.905 * SIP ( R = 0.9596, p < 0.0001). The ideal LL could be predicted using the following equation using PI and age: ideal LL = 32.33 + 0.623 * PI – 0.280 * age ( R = 0.6033, p < 0.001) and using SIP and age: ideal LL = 24.29 + 0.609 * SIP – 0.309 * age ( R = 0.6177, p < 0.001). Conclusion: Both SIP and PIA were reliable parameters for determining the morphology and orientation of the pelvis, respectively. Ideal LL was accurately predicted using the SIP with equal accuracy as the PI. Our findings will assist clinicians in the assessment of spinopelvic sagittal alignment.

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Multilevel Pedicle Subtraction Osteotomy for Correction of Severe Rigid Adult Spinal Deformities: A Case Series, Indications, Considerations, and Literature Review

Operative Neurosurgery ◽

10.1093/ons/opaa419 ◽

2020 ◽

Author(s):

Darryl Lau ◽

Alexander F Haddad ◽

Marissa T Fury ◽

Vedat Deviren ◽

Christopher P Ames

Keyword(s):

Pain Relief ◽

Sagittal Plane ◽

Adult Spinal Deformity ◽

Thoracolumbar Spine ◽

Case Series ◽

Pedicle Subtraction Osteotomy ◽

Spinal Deformities ◽

Spinal Region ◽

Spinal Imbalance

Abstract BACKGROUND Rigid and ankylosed thoracolumbar spinal deformities require three-column osteotomy (3CO) to achieve adequate correction. For severe and multiregional deformities, multilevel 3CO is required but its use and outcomes are rarely reported. OBJECTIVE To describe the use of multilevel pedicle subtraction osteotomy (PSO) in adult spinal deformity (ASD) patients with severe, rigid, and ankylosed multiregional deformity. METHODS Retrospective review of 5 ASD patients who underwent multilevel PSO for the correction of severe fixed deformity and review the literature regarding the use of multilevel PSO. RESULTS Five patients presented with spinal imbalance secondary to regional and multiregional spinal deformities involving the thoracolumbar spine. All patients underwent a single-stage two-level noncontiguous PSO, and 2 of the patients underwent a staged third PSO to treat deformity involving a separate spinal region. Significant radiographic correction was achieved with normalization of spinal alignment and parameters. Two-level PSO was able to provide greater than 80 degrees of sagittal plane correction in both the lumbar and thoracic spine. Two patients experienced new postoperative weakness which recovered to preoperative baseline at 3 to 6 mo follow-up. At most recent follow-up, 4 of the 5 patients gained significant pain relief and had improved functionality. CONCLUSION Noncontiguous multilevel PSO is a formidable surgical technique. Additional risk (compared to single-level 3CO) comes in the form of greater blood loss and higher risk for postoperative weakness. Nonetheless, multilevel PSO is feasible and effective for correcting severe multiplanar and multiregional ASD, and patients gain significant benefits in increased functionality and pain relief.

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Acute failure of S2-alar-iliac screw pelvic fixation in adult spinal deformity: novel failure mechanism, case series, and review of the literature

Journal of Neurosurgery Spine ◽

10.3171/2021.2.spine201921 ◽

2021 ◽

pp. 1-9

Author(s):

Christopher T. Martin ◽

David W. Polly ◽

Kenneth J. Holton ◽

Jose E. San Miguel-Ruiz ◽

Melissa Albersheim ◽

...

Keyword(s):

Failure Mechanism ◽

Lumbar Lordosis ◽

Adult Spinal Deformity ◽

Case Series ◽

Vertical Axis ◽

Consecutive Series ◽

Adult Deformity ◽

Pelvic Fixation ◽

Fixation Points ◽

Acute Failure

OBJECTIVE Pelvic fixation with S2-alar-iliac (S2AI) screws is an established technique in adult deformity surgery. The authors’ objective was to report the incidence and risk factors for an underreported acute failure mechanism of S2AI screws. METHODS The authors retrospectively reviewed a consecutive series of ambulatory adults with fusions extending 3 or more levels, and which included S2AI screws. Acute failure of S2AI screws was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS Failure occurred in 6 of 125 patients (5%) and consisted of either slippage of the rods or displacement of the set screws from the S2AI tulip head, with resultant kyphotic fracture. All failures occurred within 6 weeks postoperatively. Revision with a minimum of 4 rods connecting to 4 pelvic fixation points was successful. Two of 3 (66%) patients whose revision had less fixation sustained a second failure. Patients who experienced failure were younger (56.5 years vs 65 years, p = 0.03). The magnitude of surgical correction was higher in the failure cohort (number of levels fused, change in lumbar lordosis, change in T1–pelvic angle, and change in coronal C7 vertical axis, each p < 0.05). In the multivariate analysis, younger patient age and change in lumbar lordosis were independently associated with increased failure risk (p < 0.05 for each). There was a trend toward the presence of a transitional S1–2 disc being a risk factor (OR 8.8, 95% CI 0.93–82.6). Failure incidence was the same across implant manufacturers (p = 0.3). CONCLUSIONS All failures involved large-magnitude correction and resulted from stresses that exceeded the failure loads of the set plugs in the S2AI tulip, with resultant rod displacement and kyphotic fractures. Patients with large corrections may benefit from 4 total S2AI screws at the time of the index surgery, particularly if a transitional segment is present. Salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

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Beyond Pelvic Incidence–Lumbar Lordosis Mismatch: The Importance of Assessing the Entire Spine to Achieve Global Sagittal Alignment

Global Spine Journal ◽

10.1177/2192568217699405 ◽

2017 ◽

Vol 7 (6) ◽

pp. 536-542 ◽

Cited By ~ 8

Author(s):

Robert K. Merrill ◽

Jun S. Kim ◽

Dante M. Leven ◽

Joung Heon Kim ◽

Samuel K. Cho

Keyword(s):

Lumbar Lordosis ◽

Pelvic Incidence ◽

Adult Spinal Deformity ◽

Case Series ◽

Vertical Axis ◽

Retrospective Case ◽

Sagittal Vertical Axis ◽

Global Sagittal Alignment ◽

Sagittal Parameters ◽

Combined Parameters

Study Design: Retrospective case series. Objective: To investigate which sagittal parameters contribute to a normal sagittal vertical axis (SVA) when there is a pelvic incidence-lumbar lordosis (PI-LL) mismatch >10° following adult spinal deformity (ASD) correction. Methods: We performed a retrospective review of ASD patients with >5 levels fused. Sagittal measurements between cohorts of postoperative PI-LL >10° and PI-LL<10° were compared. We correlated SVA to pelvic tilt (PT), thoracic kyphosis (TK), PI-LL, cervical lordosis (CL), and correlated the pre- to postoperative change in SVA to change in PT, change in TK, change in PI-LL, and change in CL. We also correlated SVA and the change in SVA to combined parameters of ((PI-LL) − PT + TK). Results: We analyzed 52 patients with a mean age of 59 ± 16 years. In patients with a postoperative SVA <5cm, a smaller TK was seen when PI-LL >10° than when PI-LL<10° (15.45° vs 33.04°, P = .0004). Additionally, PT was larger when PI-LL >10° than when PI-LL <10° (25.73° vs 19.07°, P = .006). SVA correlated better with ((PI-LL) − PT + TK) ( R2 = 0.51) than with PI-LL alone ( R2 = 0.33). Lastly, there was no significant correlation between change in pre- to postoperative SVA with change in TK for all cases ( P = .73), but in cases where change in PI-LL was <10°, there was a significant correlation between change in TK and change in SVA ( P = .009). Conclusion: Our results demonstrate that PT and TK, and not just PI-LL, play an important role in maintaining sagittal balance when there is a PI-LL mismatch >10°.

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

10.21203/rs.3.rs-18890/v1 ◽

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.

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

10.21203/rs.3.rs-1033808/v1 ◽

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.

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Sacral incidence to pubis: a novel and alternative morphologic radiological parameter to pelvic incidence in assessing spinopelvic sagittal alignment

10.21203/rs.3.rs-20179/v2 ◽

2020 ◽

Author(s):

Yasuhito Takahashi ◽

Kei Watanabe ◽

Masashi Okamoto ◽

Shun Hatsushikano ◽

Kazuhiro Hasegawa ◽

...

Keyword(s):

Correlation Coefficient ◽

Pelvic Incidence ◽

Sagittal Alignment ◽

Intraclass Correlation ◽

Hip Dislocation ◽

Standing Position ◽

Regression Equation ◽

Whole Body ◽

Spinopelvic Parameters ◽

Pelvic Inclination

Abstract Background: Although pelvic incidence (PI) is a key morphologic parameter in assessing spinopelvic sagittal alignment, accurate measurements of PI become difficult in patients with severe hip dislocation or femoral head deformities. This study aimed to investigate the reliability of our novel morphologic parameters and the correlations with established sagittal spinopelvic parameters.Methods: One hundred healthy volunteers (25 male and 75 female), with an average age of 38.9 years, were analysed. Whole-body alignment in the standing position was measured using a slot-scanning X-ray imager. We measured the established spinopelvic sagittal parameters and a novel parameter: the sacral incidence to pubis (SIP). The correlation coefficient of each parameter, regression equation of PI using SIP, and regression equation of lumbar lordosis (LL) using PI or SIP were obtained. The intraclass correlation coefficient (ICC) was calculated as an evaluation of the measurement reliability.Results: Reliability analysis showed high intra- and inter-rater agreements in all the spinopelvic parameters, with ICCs > 0.9. The SIP and pelvic inclination angle (PIA) demonstrated strong correlation with PI (R = 0.96) and pelvic tilt (PT) (R = 0.92). PI could be predicted according to the regression equation: PI = –9.92 + 0.905 * SIP (R = 0.9596, p < 0.0001). The ideal LL could be predicted using the following equation using PI and age: ideal LL = 32.33 + 0.623 * PI – 0.280 * age (R = 0.6033, p < 0.001) and using SIP and age: ideal LL = 24.29 + 0.609 * SIP – 0.309 * age (R = 0.6177, p < 0.001).Conclusion: Both SIP and PIA were reliable parameters for determining the morphology and orientation of the pelvis, respectively. Ideal LL was accurately predicted using the SIP with equal accuracy as the PI. Our findings will assist clinicians in the assessment of spinopelvic sagittal alignment.

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