Roussouly Type Research Articles

T1 Pelvic and Lumbar Pelvic Angles Normative Values: A Prospective Cohort Study of 472 Asymptomatic Volunteers.

Cross-sectional analysis of a prospectively enrolled cohort. Determine the normative values of the T1 Pelvic Angle (TPA) and Lumbar Pelvic Angle (LPA) in an asymptomatic cohort of volunteers. The TPA and LPA have been introduced as sagittal spino-pelvic parameters to guide correction of adult spinal deformity. Suggested values for these parameters were derived from linear regressions based on Oswestry Disability Index scores from adult spinal deformity patients. While a few studies have evaluated the normative value of TPA, none have evaluated the LPA in asymptomatic individuals. TPA and LPA were measured on radiographs of 472 asymptomatic volunteers between 20 and 40 years old. TPA and LPA were calculated as originally described from the centroid of T1 and L1 respectively, to the center of the femoral head to the midpoint of the sacral endplate. TPA and LPA were also evaluated using the midpoint of the superior endpoint as a surrogate to the centroid of the vertebra to compare these two measurement techniques. TPA and LPA normative values were respectively 7.3 [6.8-7.8] and 6.3o [5.9-6.7]. There was no statistically significant difference between using the centroid of T1 or L1 versus using the midpoint of the superior endplate with respective results of 7.5o [7.0-8.0] (P=0.55) and 6.1o [5.6-6.5] (P=0.43). TPA was significantly different between Roussouly types 1-2-3 versus type 4 with respective results of of 6.7o, 7.2o, 6.5o and 9.2o (P<0.001). The same difference was observed for the LPA with normative results of 3.8o, 5.1o, 5.8o and 9.3o (P<0.001), respectively, for Roussouly types 1,2,3 and 4. TPA and LPA normative values are 7o and 6o, respectively, and vary between Roussouly morphotypes 1,2 and 3 versus type 4. Using the midpoint of the superior endplate of T1 and L1 versus the centroid yielded similar results and therefore could be easier to use intraoperatively.

P141. Factors associated with construct failures in adult spine deformity patients matching ideal Roussouly type

P141. Factors associated with construct failures in adult spine deformity patients matching ideal Roussouly type

Can pelvic incidence affect changes in sagittal spino-pelvic parameters between standing and sitting positions in individuals with lumbar degenerative disease?

The aim of this study was to explore the correlation between PI and standing-to-sitting changes of the sagittal alignment in patients with lumbar degenerative diseases, and investigate the differences in posture changes among Roussouly types. A total of 209 patients with lumbar degenerative disease were retrospectively included in this study. All the patients received lateral full body imaging in both standing and sitting positions. Sagittal parameters including SVA, OD-HA, PT, PI, PT/PI, SS, LL, TK, Upper LL (L1-L4) and Lower LL (L4-S1) were measured in both standing and sitting position, and the parameters were compared between two positions. The correlations between PI and lumbo-pelvic changes were analyzed. The postural changes were compared among different Roussouly types. From standing to sitting, all the parameters except PI significantly changed, including SVA, OD-HA, PT, PT/PI, SS, LL, TK, Upper LL and Lower LL. The contribution of lower LL was greater to global LL than upper LL. PI had a significant correlation with ΔPT, ΔSS, ΔLL, ΔUpper LL and ΔLower LL. From standing to sitting, type 4 patients had the most pronounced ΔPT, ΔSS and ΔLL, and ΔLower LL of types 3 and 4 were greater than that of types 1 and 2. In patients with degenerative disease, PI plays an important role in determining the extent of lumbo-pelvic changes from standing to sitting. Among different Roussouly types, type 4 patients have the most pronounced changes of PT, SS and LL, suggesting the relatively greater flexibility of pelvis and lumbar spine.

Analysis of Spinal-Pelvic Sagittal Plane Parameters in Patients with Lumbar Vertebral Posterior Ring Apophysis Separation

To investigate the characteristics of the spinal-pelvic sagittal sequence in patients with lumbar vertebral posterior ring apophysis separation (PRAS). A retrospective analysis was conducted on 119 hospitalized patients with PRAS, and 119 adults without symptoms of low back and leg pain were selected as the control. General data and spinal-pelvic sagittal parameters were collected and analyzed. Compared to the control group, the pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis of the PRAS group were significantly lower, while the pelvic tilt (PT), sagittal vertical axis, and PI minus LL were significantly higher. There was no significant difference in thoracolumbar kyphosis between the 2 groups. In patients with PRAS, the LL value of lumbar curvature was moderately correlated with thoracic kyphosis and SS, while PI, PT, and SS were pairwise correlated, indicating that the change in one parameter is often accompanied by simultaneous changes in other parameters if PRAS happens. The correlation between different parameters could provide guidance for the diagnosis of PRAS. In terms of LL type, the PRAS group was mainly of Roussouly type I, while the control group was mainly of type II, and the difference in the composition ratio was statistically significant. As reflected by the spinal-pelvic sagittal parameters, the patients with PRAS exhibited reduced thoracic and lumbar curvature, posterior PT, and fewer vertebral bodies involved in LL. These morphological characteristics indicate the changes of the mechanical structure of the spine.

Surgical treatment of Roussouly type 1 with realigning Roussouly spinal shape and improving SRS-Schwab modifier: effect on minimal clinically important difference.

To evaluate outcomes of choosing different Roussouly shapes and improving in Schwab modifiers for surgical Roussouly type 1 patients. Baseline (BL) and 2-year (2Y) clinical data of adult spinal deformity (ASD) patients presenting with Roussouly type 1 sagittal spinal alignment were isolated in the single-center spine database. Patients were grouped into Roussouly type 1, 2 and 3 with anteverted pelvis (3a) postoperatively. Schwab modifiers at BL and 2Y were categorized as follows: no deformity (0), moderate deformity (+), and severe deformity (++) for pelvic tilt (PT), sagittal vertical axis (SVA), and pelvic incidence and lumbar lordosis mismatch (PI-LL). Improvement in SRS-Schwab was defined as a decrease in the severity of any modifier at 2Y. A total of 96 patients (69.9 years, 72.9% female, 25.2kg/m2) were included. At 2Y, there were 34 type 1 backs, 60 type 2 backs and only 2 type 3a. Type 1 and type 2 did not differ in rates of reaching 2Y minimal clinically important difference (MCID) for health-related quality of life (HRQOL) scores (all P > 0.05). Two patients who presented with type 3a had poor HRQOL scores. Analysis of Schwab modifiers showed that 41.7% of patients improved in SVA, 45.8% in PI-LL, and 36.5% in PT. At 2Y, patients who improved in SRS-Schwab PT and SVA had lower Oswestry disability index (ODI) scores and significantly more of them reached MCID for ODI (all P < 0.001). Patients who improved in SRS-Schwab SVA and PI-LL had more changes of VAS Back and Short Form-36 (SF-36) outcomes questionnaire physical component summary (SF-36 PCS), and significantly more reached MCID (all P < 0.001). By 2Y, type 2 patients who improved in SRS-Schwab grades reached MCID for VAS back and ODI at the highest rate (P = 0.003, P = 0.001, respectively), and type 1 patients who improved in SRS-Schwab grades reached MCID for SF-36 PCS at the highest rate (P < 0.001). For ASD patients classified as Roussouly type 1, postoperative improvement in SRS-Schwab grades reflected superior patient-reported outcomes while type 1 and type 2 did not differ in clinical outcomes at 2Y. However, development of type 3a should be avoided at the risk of poor functional outcomes. Utilizing both classification systems in surgical decision-making can optimize postoperative outcomes.

Characteristics of Spinal Morphology According to the "Current" and "Theoretical" Roussouly Classification Systems in a Diverse, Asymptomatic Cohort: Multi-Ethnic Alignment Normative Study (MEANS).

Cross-sectional cohort study. To classify spinal morphology using the "current" and "theoretical" Roussouly systems and assess sagittal alignment in an asymptomatic cohort. 467 asymptomatic volunteers were recruited from 5 countries. Radiographic parameters were measured via the EOS imaging system. "Current" and "theoretical" Roussouly classification was assigned with sagittal whole spine imaging using sacral slope (SS), pelvic incidence (PI), and the lumbar apex. One-way analysis of variance (ANOVA) was performed to compare subject characteristics across Roussouly types, followed by post hoc Bonferroni correction. Volunteers were categorized into 4 groups (Types 1-4) and 1 subgroup (Type 3 AP) using the "current" and "theoretical" Roussouly systems. The mean PI in "current" Roussouly groups was 40.8° (Type 1), 43.6° (Type 2), 52.4° (Type 3), 62.4° (Type 4), and 43.7° (Type 3AP). The mean PI in "theoretical" Roussouly groups was 36.5° (Type 1), 39.1°(Type 2), 52.5° (Type 3), 67.3° (Type 4), and 51.0° (Type 3AP). The difference in PI between "current" and "theoretical" Roussouly types was significant for Type 1 (P = .02), Type 2 (P < .001), Type 4 (P < .001), and Type 3AP (P < .001). 34.7% of subjects had a "current" Roussouly type different from the "theoretical" type. Type 3 theoretical shape had the most frequent mismatch, constituting 61.1% of the mismatched subjects. 51.5% of mismatched Type 3 become "current" Type 4. The distribution of Roussouly types differs depending on whether the "current" or "theoretical" classification are employed. A sizeable proportion of volunteers exhibited current and theoretical type mismatch, highlighting the need to interpret sagittal alignment cautiously when utilizing the Roussouly system.

Examining autocorrection of concurrent cervical malalignment following thoracolumbar deformity surgery.

The aim of the study was to assess preoperative radiographic parameters predictive of cervical deformity (CD) autocorrection in patients undergoing thoracolumbar deformity (ASD) surgery. This was a retrospective cohort study. Inclusion criteria were operative ASD patients with complete baseline (BL) and 2-year radiographic data. Patients with cervical fusion during index surgery, revision involving cervical fusion, and those who developed proximal junctional kyphosis by 2-year postoperative were excluded from the study. If patients met CD criteria at BL but not at 6 weeks or 2 years postoperatively, they were considered autocorrected (AC). Descriptive and univariate analysis, binominal logistic regression, and multivariable backward stepwise regression. Two hundred and twenty ASD patients were included. 51.4% of patients had preoperative CD. By 6-week postoperative, 32.7% achieved AC. At 2 years, 24.8% of preoperative CD patients obtained AC. 2-year AC patients had lower BL sacral slope, lumbar lordosis (LL), T1 slope, cervical lordosis (CL), and C2-T3, and T2-T12 kyphosis (all P < 0.05). Patients with BL-unmatched Roussouly types are corrected postoperatively and are more likely to experience autocorrection at 1 year (45.2% vs. 19.0%; P = 0.042) and at 2 years (31% vs. 4.8%; P = 0.018). Multivariable analysis revealed that patients with BL-mismatched Roussouly types were corrected postoperatively and showed a significant increase in likelihood of AC at 1 year (odds ratio [OR]: 18.72; P = 0.029) and 2 years (OR: 8.5; P = 0.047). Similarly, BL LL (OR: 0.772; P = 0.003) and CL (OR: 0.829; P = 0.005) exhibited significant predictive value for autocorrection at 1 year and 2 years (OR: 0.927; P = 0.004 | OR: 0.942; P = 0.039; respectively). Autocorrection is more likely in patients with postoperatively corrected Roussouly types, those with lower BL cervical, and LL. Given these findings, it may not be necessary to routinely extend reconstruction into the cervical spine for ASD patients with similar characteristics to those in this study.

Validation of Roussouly classification in predicting the occurrence of adjacent segment disease after short-level lumbar fusion surgery

BackgroundRecent studies demonstrated that restoring sagittal alignment to the original Roussouly type can remarkably reduce complication rates after adult spinal deformity surgery. However, there is still no data proving the benefit of maintaining ideal Roussouly shape in the lumbar degenerative diseases and its association with the development of adjacent segment disease (ASD). Thus, this study was performed to validate the usefulness of Roussouly classification to predict the occurrence of ASD after lumbar fusion surgery.Materials and MethodsThis study retrospectively reviewed 234 consecutive patients with lumbar degenerative diseases who underwent 1- or 2-level fusion surgery. Demographic and radiographic data were compared between ASD and non-ASD groups. The patients were classified by both “theoretical” [based on pelvic incidence (PI)] and “current” (based on sacral slope) Roussouly types. The patients were defined as “matched” if their “current” shapes matched the “theoretical” types and otherwise as “mismatched”. The logistic regression analysis was performed to identify the factors associated with ASD. Finally, clinical data and spinopelvic parameters of “theoretical” and “current” types were compared.ResultsWith a mean follow-up duration of 70.6 months, evidence of ASD was found in the 68 cases. Postoperatively, ASD group had more “current” shapes classified as type 1 or 2 and fewer as type 3 than the non-ASD group (p < 0.001), but the distribution of “theoretical” types was similar between groups. Moreover, 80.9% (55/68) of patients with ASD were mismatched, while 48.2% (80/166) of patients without ASD were mismatched (p < 0.001). A multivariate analysis identified age [odds ratio (OR) = 1.058)], 2-level fusion (OR = 2.9830), postoperative distal lordosis (DL, OR = 0.949) and mismatched Roussouly type (OR = 4.629) as independent risk factors of ASD. Among the four "theoretical" types, type 2 had the lowest lumbar lordosis, DL, and segmental lordosis. When considering the "current" types, current type 2 was associated with higher rates of 2-level fusion, worse DL, and greater pelvic tilt compared with other current types.ConclusionsDL loss and mismatched Roussouly type were significant risk factors of ASD. To decrease the incidence of ASD, an appropriate value of DL should be achieved to restore sagittal alignment back to the ideal Roussouly type.Level of Evidence: Level 4.

Modern Concepts in Sagittal Curve Measurement: Comparison of Spline-Based and Fixed Landmark Measurements in a Cohort of 1520 Healthy Subjects.

Retrospective multicenter study. Our objective was to compare the spline-based measurement of sagittal spinal curvatures to fixed landmarks in a normative population. Recent research has stressed the importance of considering sagittal curvature in its entirety using a spline reconstruction. To date, no data supports the superiority of this method in comparison to classic measurement methods. Full-spine biplanar radiographs of subjects over 20 years old who had normal radiographs were analyzed. Thoracic kyphosis (TK) and lumbar lordosis (LL) were measured following two modalities: either using predefined landmarks (TK T1T12 , TK T5T12 , and LL L1S1 ) or spline-based measurement (TK Spline and LL spline ). A total of 1520 subjects were included (mean 54yo). The mean difference between TK spline and TK T1T12 was 1.4° and between TK spline and TK T5T12 was 11.7° ( P <0.001). LL spline was significantly larger than LL L1S1 (55° vs . 54°, P<0.001 ). LL spline and LL L1S1 were correlated ( R =0.950, P <0.001). Pelvic incidence had no influence on the difference between LL spline and LL L1S1 ( R =-0.034, P= 0.184). Using LL L1S1 measurements, LL was underestimated in 17% of the cases. The comparison of outlier distributions according to age groups ( P =0.175), sex ( P =0.937), or pelvic incidence groups ( P =0.662) found no difference. There were significantly more outliers in Roussouly type 1 compared with other types (56%, P <0.001). Our results suggest that the use of TK T1T12 and LL L1S1 is acceptable to assess spinal sagittal curvatures. However, TK T5T12 is not accurate for the thoracic curve and should be used with caution. LL L1S1 can be used to accurately assess the lumbar curve, except in Roussouly type 1.

Effects of dynamic and rigid implantation on biomechanical characteristics of different sagittal alignment lumbar after single- or double-level spinal fixations: a finite-element modeling study

BackgroundAlthough it is critical to understand the accelerated degeneration of adjacent segments after fusion, the biomechanical properties of the spine have not been thoroughly studied after various fusion techniques. This study investigates whether four Roussouly’s sagittal alignment morphotypes have different biomechanical characteristics after different single- or double-level spinal fixations.MethodsThe parametric finite element (FE) models of Roussouly’s type (1–4) were developed based on the radiological data of 625 Chinese community population. The four Roussouly's type models were reassembled into four fusion models: single-level L4–5 Coflex fixation model, single-level L4–5 Fusion (pedicle screw fixation) model, double-level Coflex (L4–5) + Fusion (L5–S1) model, and double-level Fusion (L4–5) + Fusion (L4–5) model. A pure moment of 7.5 Nm was applied to simulate the physiological activities of flexion, extension, lateral bending and axial rotation.ResultsBoth single-level and double-level spinal fixation had the greatest effect on lumbar range of motion, disc pressure, and annulus fibrosis stress in flexion, followed by lateral bending, extension, and axial rotation. In all models, the upper adjacent segment was the most influenced by the implantation and bore the most compensation from the fixed segment. For Type 2 lumbar, the L4–L5 Coflex effectively reduced the disc pressure and annulus fibrosis stress in adjacent segments compared to the L4–L5 Fusion. Similarly, the L4–L5 Coflex offered considerable advantages in preserving the biomechanical properties of adjacent segments for Type 1 lumbar. For Type 4 lumbar, the L4–L5 Coflex did not have superiority over the L4–L5 Fusion, resulting in a greater increase in range of motion at adjacent segments in flexion and extension. The difference between the two fixations was not apparent in Type 3 lumbar. Compared to the single-level Fusion, the changes in motion and mechanics of the lumbar increased after both the double-level Coflex + Fusion and Fusion + Fusion fixations, while the differences between two double-level fixation methods on adjacent segments of the four lumbar models were similar to that of the single-level fixation.ConclusionType 3 and Type 4 lumbar have good compensatory ability and therefore allow for a wider range of surgical options, whereas surgical options for small lordotic Type 1 and Type 2 lumbar are more limited and severe.

Evolution of sagittal spinal shape for the development of thoracic ossification of ligamentum flavum.

Thoracic ossification of the ligamentum flavum (TOLF) is a rare pathology for which limited research exists. While it is known that mechanical factors play a role in the development of TOLF, little is currently understood about the sagittal alignment and related mechanical stress involved in its development. This study aims to describe the sagittal alignment of patients with TOLF based on the pathologic evolution of the Roussouly classification. The current study evaluated the preoperative Roussouly type in consecutive patients who underwent posterior decompressive laminectomy with or without posterior screw fixation for TOLF between January 2015 and December 2021. The post-evolution sagittal alignments were analyzed using the classic Roussouly classification based on sacral slope (SS). To determine the pre-evolution Roussouly type, the patients were retrospectively classified using their individual PI and PT values. Lumbopelvic parameters and morphological index including inflection point (IP), lumbar apex (LA), and lordosis distribution index (LDI) were also evaluated. Forty-three patients (21 women and 22 men) were included; their mean age was 64.21 ± 11.01 years (range 43-81). The most affected level was T10-11 (48.83%). The mean PI was 50.81 ± 9.56°, the mean SS was 33.11 ± 8.61°and the mean PT was 17.69 ± 7.89°. According to the post-evolution Roussouly classification, type 2 shape was the most frequently observed type (n = 23, 53.5%) in the post-evolution classification while type 3 was the most common type observed in the pre-evolution classification (n = 22, 51.5% and P = .00). The level of IP and LA in type 3 moved caudally (around L2 and L4/5 level, respectively) and the LDI increased (77.98 ± 8.08%) than the normal standard value. The authors found that the majority of the patients had a false type 2 spine, which had evolved pathologically from Roussouly type 3 and exhibited increased LDI, a lowered level of IP, and a lowered level of LA. These changes of spinal shape, including the transition to long hypolordosis and increased length of the thoracic kyphosis, may have accentuated tensile stress at the lower thoracic spine and contributed to the development of TOLF.

Restoring the ideal Roussouly sagittal alignment in Lenke 5 adolescent idiopathic scoliosis patients: a method for decreasing the risk of proximal junctional kyphosis.

Although the Roussouly classification has been widely used in surgical planning for adult scoliosis patients, little is known about whether it can be used to guide sagittal correction for adolescent idiopathic scoliosis (AIS) patients. The purpose of this study was to explore whether the Roussouly classification could be used to help surgeons restore the ideal sagittal alignment for AIS patients to avoid the development of proximal junctional kyphosis (PJK). In this retrospective cohort study, eighty-seven patients with Lenke 5 AIS who underwent surgery from January 2010 to August 2020 were enrolled and divided into two groups: the PJK group and the non-PJK group. All patients were classified into "current types" and "ideal types" according to two versions of the Roussouly classification, and the mismatch rate was evaluated in terms of the consistency between their current type and ideal type. Student's t test, Mann‒Whitney U test, Pearson's Chi-square test, and others were used to compare the two groups regarding patient demographic characteristics (age, sex, Risser sign, etc.) and radiographic parameters (sagittal vertical axis [SVA]; thoracic kyphosis [TK]; thoracolumbar junctional kyphosis [TLK]; lumbar lordosis [LL]; pelvic incidence [PI]; pelvic tilt [PT]; sacral slope [SS]; upper instrumented vertebra [UIV]; lower instrumented vertebra [LIV]; etc.). Multivariate logistic regression with backwards stepwise selection was performed to identify the risk factors for PJK. PJK was observed in 16 out of 87 patients (18.4%) until the final follow-up. The incidence of PJK was significantly higher in the patients not matching their ideal type than in those who did after surgery (60.9% vs. 3.1%, p = 0.000). The patients with ideal Type 1 had the highest incidence of PJK, while the lowest incidence was observed in patients with ideal Type 2 (50.0% vs. 5.1%, p = 0.000). The PJK group had greater TK, LL, and PI-LL than the non-PJK group before and after surgery. The postoperative PJA in the PJK group was also larger than that in the non-PJK group. Multivariate logistic regression revealed that postoperative Roussouly type mismatch was significantly associated with the occurrence of PJK (OR = 64.2, CI = 9.6-407.1, p = 0.000). The Roussouly classification could serve as a prognostic tool for PJK in Lenke 5 AIS patients. Corrective surgery should restore sagittal alignment with respect to the patient's ideal sagittal profile (according to the Roussouly classification based on the PI) to decrease the incidence of PJK in AIS patients.

Pelvic index: A new pelvic parameter for assessing sagittal spinal alignment

The incidence of correctional surgery for adult spinal deformity (ASD) has increased significantly over the past 2 decades. Pelvic incidence, an angular measurement, is the gold standard pelvic parameter and is used to classify spinal shapes into Roussouly types. Current literature states that restoration of the spine to its original Roussouly classification optimizes outcomes. We propose a new pelvic parameter, pelvic index, as a length measurement to complement pelvic incidence in more accurately characterizing Roussouly types. This study is a retrospective evaluation of sagittal spinal radiographs of 208 patients who were assessed by a single fellowship trained orthopedic spine surgeon between January and December 2020. Measurements included pelvic incidence, sacroacetabular distance, and L5 vertebral height. Pelvic index was calculated as the ratio of sacroacetabular distance to L5 height. Each spine was also classified into one of the Roussouly types: 1, 2, 3 anteverted pelvis (AP), 3, or 4. The 2 pelvic parameters were compared between groups to assess their ability to differentiate between Roussouly types. Of the 208 patients included, 103 (49.5%) were female and 105 (50.5%) were male. The mean pelvic incidence was 54.9 ± 12.3° and the mean pelvic index was 3.99 ± 0.38. The difference in mean pelvic index was statistically significant between types 1 and 2 (0.15; p=.046) and between types 1 and 3 AP (0.19; p=.029). It was not statistically significant between types 3 and 4 (0.05; p=.251). However, in terms of pelvic incidence, the mean difference was statistically significant only between types 3 and 4 (10.4; p<.001). Pelvic index is the ratio of the sacroacetabular distance to the height of the L5 vertebra. In conjunction with pelvic incidence, pelvic index can help to distinguish between Roussouly types 1 and 2 and between types 1 and 3 AP, the low-pelvic incidence types.

Evaluation of spinopelvic alignment according to Roussouly classification can predict the occurrence of adjacent segment disease after lumbar fusion

Objective: To investigate the correlation of spinopelvic alignment according to Roussouly classification on the occurrence of adjacent segment disease (ASD) in the patients undergoing fusion surgery for lumbar degenerative diseases. Methods: A cross-sectional study. Clinical data of 166 consecutive patients who had undergone lumbar fusion between January 2009 and January 2019 in the Affiliated Changzhou Second People's Hospital of Nanjing Medical University and Affiliated Drum Tower Hospital of Medical School of Nanjing University were retrospectively reviewed. There were 59 males and 107 females, with an average age of (58.6±9.5) years (ranged 41-78 years). Fusion length averagely spanned (1.7±0.7) levels (ranged 1-3 levels). The patients were classified by both "theoretical" (based on pelvic incidence (PI)) and "current"(based on sacral slope (SS)) Roussouly types. The patients were classified as "matched" if their "current" shape matched the "theoretical" type and otherwise as "unmatched". Multivariate logistic regression analysis of the variables recruited from univariate analyses was performed to identify the factors independently associated with the development of ASD after lumbar fusion. Results: The average follow-up duration after initial surgery was (49.2±20.7) months (ranged 25 to 134 months). Thirty (18.1%, 30/166) patients were diagnosed as ASD. Postoperatively, two thirds of the patients who suffered ASD after surgery were unmatched, while 36.8% (50/136) of the patients without ASD had unmatched type. Univariate analyses showed that older age, more fusion levels, float fusion, pre-and postoperative worse spinopelvic alignment, and postoperative unmatched Roussouly type were identified as risk factors of ASD. Multivariate logistic regression analysis identified postoperative Roussouly type mismatch (OR=3.310, 95%CI: 1.282-8.545, P=0.013), old age (OR=1.074, 95%CI: 1.019-1.131, P=0.008) and postoperative SS (OR=0.928, 95%CI: 0.865-0.995, P=0.036) as the independent risk factors of development of ASD after lumbar fusion. Conclusion: A significant association between postoperative sagittal malalignment and occurrence of ASD is detected, the evaluation of sagittal alignment by Roussouly classification could help predict the occurrence of ASD.

Relationship between lumbar disc herniation and Roussouly classification in the sagittal alignment of the spine and pelvis in young people.

The sagittal plane of spine-pelvis morphology of adult patients with lumbar disc herniation (LDH) differs from that of normal people. There is a correlation between abnormal sagittal plane morphology and adult LDH. This study aimed to investigate the relationship between LDH in young people and the Roussouly classification in the sagittal alignment of the spine and pelvis. A total of 126 patients with LDH hospitalized in our tertiary hospital between January 2020 and January 2021 who met the inclusion and exclusion criteria were retrospectively analyzed in a cross-sectional study. Participants were grouped according to the spinal level of disc herniation (L4/5 group, L5/S1 group, L3/4 group). Pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) of all cases were measured using standing lateral spinal radiographs. Facet joint angles (FJA) were measured using lumbar computed tomography (CT) horizontal radiographs, and the height of the anterior, middle, and posterior margins of the herniated disc was measured using sagittal radiographs. The classification of Pfirrmann disc degeneration was determined via magnetic resonance imaging (MRI) film of the lumbar region. Roussouly classification was performed according to sagittal plane morphology, and data were analyzed among each group. In all, 126 patients aged from 18 to 40 years, with an average age of 31.04±5.886 years were included. There were 63 cases of L4/5 disc herniation, 59 cases of L5/S1 herniation, and 4 cases of L3/4 herniation. There were 35 cases of epiphyseal separation. The Roussouly classification included 21 cases of type 1, 56 cases of type 2, 32 cases of type 3, 4 cases of type 4, and 13 cases of type 3 + anteverted pelvis (type 3-AP). The L4/5 disc herniation group had significantly more types 2 and 3 than the other groups, and the L5/S1 disc herniation group had significantly more types 1 and 2 than the other groups. There were no significant differences in the Pfirrmann grade of intervertebral disc degeneration; epiphyseal separation; the height of anterior, middle, and posterior margins of the herniated disc; the difference between left and right facet angle and bilateral facet angle; and the thoracic kyphosis (TK) value among any of the groups (P>0.05). There were significant differences in PI, PT, SS, lumbar lordosis (LL), and height of the anterior and posterior margins of the intervertebral space among all groups (P<0.05). PI values were grouped at 50°; PT, SS, and LL were significantly different (P<0.05), whereas TK values were not significantly different between the 2 groups (P>0.05). SS values were grouped at 35°, and there were significant differences in PI, TK, and LL between the 2 groups (P<0.05). According to the disc herniation segment, the patients were divided into L4/5 and L5/S1 groups. There were significant differences in PI, PT, anterior edge height, anterior to posterior edge height, left facet angle, right facet angle, and bilateral facet angle (P<0.05). LDH is common in L4/5 and L5/S1 segments. The incidence of Roussouly type 1 and 2 LDH is significantly higher than other types, and type 4 is the lowest. Small PI and small SS are more obvious in the L5/S1 segment. L5/S1 disc herniation is more common in patients with Roussouly type 1 and 2 classifications, whereas L4/5 disc herniation is more frequent in patients with Roussouly type 2 and 3 classifications.

A Validation Study of Four Preoperative Surgical Planning Tools for Adult Spinal Deformity Surgery in Proximal Junctional Kyphosis and Clinical Outcomes.

Four guidelines have been suggested for optimal correction in adult spinal deformity surgery: Scoliosis Research Society (SRS)-Schwab classification, age-adjusted sagittal alignment goals, Global Alignment and Proportion (GAP) score, and the Roussouly algorithm. Whether these goals provide benefit in both proximal junctional kyphosis (PJK) reduction and clinical outcome improvement remains unclear. To validate 4 preoperative surgical planning tools in PJK development and clinical outcomes. We retrospectively reviewed patients who underwent ≥5-segment fusion including the sacrum for adult spinal deformity with a follow-up of ≥2-year. PJK development and clinical outcomes were compared among the groups separately using 4 surgical guidelines: SRS-Schwab pelvic incidence (PI)-lumbar lordosis (LL) modifier (Group 0, +, ++), age-adjusted PI-LL goal (undercorrection, matched correction, and overcorrection), GAP score (proportioned, moderately disproportioned, and severely disproportioned groups), and the Roussouly algorithm (restored and nonrestored groups). A total of 189 patients were included in this study. The mean age was 68.3 years, and there were 162 women (85.7%). There were no differences in the rate of PJK development and clinical outcomes among SRS-Schwab PI-LL modifier and GAP score groups. With the age-adjusted PI-LL goal, PJK developed significantly less frequently in the matched group compared with the under- and overcorrection groups. Clinical outcomes were significantly better in the matched group compared with the under- and overcorrection groups. With the Roussouly algorithm, PJK developed significantly less frequently in the restored group than in the nonrestored group. However, there were no differences in clinical outcomes between the 2 Roussouly groups. Correction according to the age-adjusted PI-LL goal and the restored Roussouly type was associated with reduced PJK development. However, differences in clinical outcomes were only observed in the age-adjusted PI-LL groups.

The Analysis of Preoperative Roussouly Classification on Pain Scores and Radiological Data in Lateral Lumbar Interbody Fusion for Patients with Lumbar Degenerative Disease

A retrospective observational study. The type of sagittal profile defined by Roussouly has affected spinal degeneration and surgical outcome. This study aimed to investigate the effect of preoperative Roussouly classification on pain intensity and radiological data of patients with lumbar degenerative disease who underwent indirect decompression with lateral lumbar interbody fusion (LLIF). We retrospectively investigated 102 patients who underwent LLIF without direct decompression. Patients were subdivided into 4 groups according to the Roussouly classification determined from preoperative full-length and lateral spine X-rays, and classified according to Roussouly types I, II, and IV in the nonstandard group and Roussouly type III in the standard group. The nonstandard group showed improved sagittal vertical axis and lumbar lordosis after LLIF surgery, but the midsagittal canal diameter and axial central canal area of the thecal sac using T2-weighted sagittal and axial magnetic resonance imaging were smaller than those in the standard group. On the other hand, each numeric rating scale score 1year after surgery improved in all patients. Changes in numeric rating scale scores in low back pain, leg pain, and numbness were not statistically significant between Roussouly classification types. These results suggest that the nonstandard group may have less indirect decompression effect from LLIF than the standard group. In the short term, we show for the first time after LLIF surgery that preoperative sagittal spinal alignment and the pelvic position may not significantly impact pain improvement.

The change of Roussouly classification after posterior lumbar fusion surgery.

Roussouly classification is an important morphologic classification which can help to determine high local stress zones of the spine. Different lumbar morphologies of Roussouly type suggest different biomechanics leading to degenerative evolution. This study aimed both to describe the change of the Roussouly classification of the human spine after posterior lumbar fusion surgery and to explore the influencing factors of postoperative Roussouly type. The study is a retrospective case-control study on preoperative and postoperative Roussouly types. A total of 167 patients with lumbar degenerative disease who had undergone short-level transforaminal lumbar interbody fusion surgery between January 2014 and December 2017 in the Department of Orthopedic Surgery, First Affiliated Hospital, Air Force Medical University, were recruited. Preoperative and postoperative general data including gender, age, follow-up time, Oswestry disability index (ODI) score, visual analogue scale (VAS) score, diagnosis, and surgical segment were recorded. Clinical parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and sagittal vertical axis (SVA) were measured using Surgimap software, and the Roussouly classification was assessed. This study included 86 male patients and 81 female patients with a mean age of 52.0±12.4 [14-88] years. The mean follow-up time for these patients was 11.5±6.9 months. The value of sagittal alignment parameters changed after the posterior lumbar fusion surgery, except for the PI value (P=0.591). Roussouly classification changed after surgery. The preoperative Roussouly values of preoperative PI, SS, and LL were significantly different in patients of 4 postoperative Roussouly types. The Roussouly classification changes after posterior lumbar fusion surgery. This change is independent of gender, age, follow-up time, and the number of surgical segments. The preoperative Roussouly type and PI value are essential in predicting one's postoperative Roussouly type.

Biomechanical Response of Four Roussouly's Sagittal Alignment Lumbar to Degeneration of Different Parts of Intervertebral Disc: Finite Element Model Analysis

BackgroundSpinal degeneration with age is commonly accompanied by excessive kyphosis and low-back pain, however, little is known about the connection between lumbar sagittal morphology and its degenerative biomechanics. This study investigates the biomechanical response of four Roussouly's sagittal alignment lumbar to degeneration of various parts of the intervertebral disc (IVD) based on threedimensional finite element (FE) models. MethodsUsing Roussouly's type parametric FE models, material properties of the degenerate nucleus populous (NP), annulus fibrosis matrix (AFM), and collagen fibers were assumed to be half of the intact IVD. A follower preload and vertical force were applied to simulate physical standing posture. Resultsthe reduced strength of the NP and AFM led to the increase of lumbar anteflexion, while the fiber mechanical properties have little effect on it. When facing IVD degeneration, Type 1 lumbar showed increased intradiscal pressures (IDPs) and fiber stress at the L1-2 and L4-S1 segments. Type 2 lumbar exhibited the highest lumbar anteflexion and pelvic rearward rotation, as well as increased IDPs among the models. Type 3 lumbar had the best biomechanical stability. Type 4 lumbar showed the higher AFM stress but the lower IDPs among the four types. ConclusionsIVD degeneration generated sagittal imbalance by increasing lumbar anteflexion movement (i.e., loss lordosis) and pelvic rearback rotation. The biomechanical response of the four Roussouly's lumbar types differed in intervertebral rotation and stress distribution.

The relationship between spino-pelvic alignment and primary dysmenorrhea.

Most women of reproductive age suffered from the primary dysmenorrhea (PD). Up to date, most studies on the etiology of dysmenorrhea focused on endocrine factors while ignored the effect of spino-pelvic bony anatomy on uterus. In this study, we innovatively shed light on the relationship between primary dysmenorrhea and sagittal spino-pelvic alignment. 120 patients diagnosed with primary dysmenorrhea and a control group of 118 healthy volunteers were enrolled into this study. All subjects received the standing full-length posteroanterior plain radiography to evaluate the sagittal spino-pelvic parameters. The visual analog scale (VAS) was used to assess pain rating of primary dysmenorrhea patients. Analysis of variance (ANOVA) or Student's t test was performed to measure statistical significance between differences. There was a significant difference in pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL) and thoracic kyphosis (TK) between PD group and Normal group (P<0.05). Furthermore, in PD group, the PI and SS was significant different between mild pain group and moderate pain group (P<0.05) and there was a significant negative correlation between pain rating and SS. From the perspective of sagittal spinal alignment, the majority of PD patients were classified with Roussouly type 2, meanwhile most normal people were classified with Roussouly type 3. Sagittal spino-pelvic alignment was related to primary dysmenorrhea symptoms. Lower SS and PI angles may contribute to a worsen pain in PD patients.