Validation of a new computer-assisted tool to measure spino-pelvic parameters

Although the Roussouly classification of common variants in spinal sagittal alignment is well accepted, no studies have implemented it in an asymptomatic adult population. In addition, no study investigated the radiographic features of asymptomatic patients with an anteverted pelvis. The aim of this prospective radiographic study of 296 asymptomatic adults without spinal pathology was to investigate how the Roussouly classification could include the anteverted pelvis concept. Pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), and the lumbar parameters lumbar lordosis (Global LL), lordosis tilt angle (LTA), total number of lordotic vertebra (LL verteb), and C7 plumbline/sacrofemoral distance ratio (C7PL ratio) were evaluated in 296 healthy volunteers (126 males, 170 females; mean age, 27 years; range 18–48 years). Comparison between the five types of the Roussouly classification used Student, ANOVA, and Tukey tests for quantitative variables and χ
 2, Fischer, and Holm tests for qualitative variables. Mean PI and PT were, respectively, (39°, 10°) for type 1, (41°, 10°) for type 2, (53°, 13°) for type 3, and (62°, 12°) for type 4 (p   35°. PT was low or negative (mean 4° ± 3°). C7PL ratio was >1 (in front of the hip axis) in 13% of all cases, and between 0 and 1 (between sacrum and hip axis) in 49%. Although asymptomatic adults stood with stable global balance, the sagittal spinal alignment of healthy subjects, newly divided in 5 sagittal types, varied significantly. Type 3 AP appears as a new and unusual sagittal shape with low-grade PI, very low or negative PT, and hyperlordosis. Whereas most asymptomatic adults stood with C7PL behind the hip axis, a sizeable portion had C7 in front of the hip axis. This could be a new controversial aspect of ideal spinal balance.

Classification of normal sagittal spine alignment: refounding the Roussouly classification

To evaluate the incidence of mechanical complications in patients with adult spine deformity (ASD) treated by restoring the normal shape according to the Roussouly classification. This is a retrospective multicentric study with a minimum follow-up of 2 years. Patients operated on with fusion for ASD (minimum performed fusion: L2 to sacrum) were included. Patients with a history of previous spinal fusion of more than three levels were excluded. Spinal and pelvic parameters were measured on the preoperative and the immediate postoperative follow-up. All mechanical complications were recorded. A total of 290 patients met the criteria of inclusion with a minimum follow-up of 2 years. Mechanical complications occurred in 30.4% of the cohort. The most common complication was PJK with an incidence of 18% while nonunion or instrumentation failure (rod breakage, implant failure) occurred in 12.4%. 66% of the patients were restored to the normal shape according to the Roussouly classification based on their PI and had a mechanical complication rate of 22.5%, whereas the remaining 34% of patients had a complication rate of 46.8% (p < 0.001). The relative risk for developing a mechanical complication if the algorithm was not met was 3 (CI 1.5–4.3; p < 0.001) In the recent literature, there are no clear guidelines for ASD correction. Restoring the sagittal spinal contour to the normal shapes of Roussouly according to the PI could serve as a guideline for ASD treatment. Ignoring this algorithm has a threefold risk of increased mechanical complications. We recommend this algorithm for treatment of ASD. IV cross-sectional observational study. These slides can be retrieved under Electronic Supplementary Material.

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Mechanical complications in adult spinal deformity and the effect of restoring the spinal shapes according to the Roussouly classification: a multicentric study.

The objective of this retrospective study is to identify the best immediate postoperative radiological predictors for the occurrence of proximal junctional kyphosis (PJK). Four proposed methods will be explored. A homogeneous database of adult scoliosis from multiple centers was used. Patients with whole spine X-rays at the required follow-up (FU) periods were included. Spinal and pelvic parameters were measured and calculated to compare four predictive methods: Method 1: assessment of the global sagittal alignment (GSA); Method 2: restoration of the theoretical values of lumbar lordosis (LL) and thoracic kyphosis (TK) according to pelvic incidence (PI); Method 3: evaluation of TK + LL, and Method 4: restoration of the apex of sagittal LL to its theoretical values according to various spine shapes in Roussouly Classification. PJK occurrence was assessed at the last FU radiograph. 250 patients were included; mean age was 56.67 years and mean FU was 2.5 years. PJK occurred in 25.6% of cases. PJK occurred in 19.9% in patients with a GSA 45° (p = 0.04, OR = 1.71). Restoring the sagittal apex of the LL to its theoretical values according to PI deceased PJK to 13.5% compared to 38.9% in the other cases (p = 0.01, OR = 4.6). The two other described methods (2 and 3) were not significant predictors. The comparison between the four predictive methods showed that a GSA >45° and restoration of sagittal apex of lordosis according to PI, were the most predictive methods for PJK in ASD. The latter had a higher predictive value. Our findings could prove useful in effective preoperative planning in ASD surgery to reduce PJK rates. Level IV.

Proximal junctional kyphosis in adult scoliosis: comparison of four radiological predictor models

To present the description of sagittal alignment of the degenerative human spine and its possible evolution. This is a retrospective observational study of degenerative evolution in spinal alignment in low back pain patients. Full spine EOS® sagittal X-rays were analyzed, and pelvic and spinal parameters were measured. Spinal shapes were classified on the hypothesis that the possible sagittal shapes of degenerative spine would be divided into four categories: “classical” Roussouly types 1–4, anteverted types (PT ≤ 5), retroverted types (PT ≥ 25) and kyphotic types. A total of 331 patients (280 women and 51 men) were included. “Classic” types 1–4 represented the majority in this cohort (71.9%). Retroverted types made the second most common category with 20.8% of the cohort. Kyphosis group (lumbar and global) make only 5.8% of this cohort, while anteverted group make the lowest incidence (1.5%). Retroverted type 2 with thoracic kyphosis should be considered a separate type and made 1.5% of this cohort. Two theoretical subtypes, retroverted type 1 and type 4 were not found. This is the first description of degenerative spine disease based on its shape and based on the classification of the normal variation in the sagittal alignment of the human lumbar spine described by Roussouly. Eleven types, divided into classical types, anteverted types, false shapes (retroverted) and kyphotic shapes, are described and an evolution pathway is proposed. An evaluation of surgical results in order to propose a treatment algorithm based on this classification should follow. Level IV cross sectional observational study.

Description of the sagittal alignment of the degenerative human spine

The purpose of this study was to evaluate the inter- and intra-observer variability of the computerized radiologic measurements using Keops® and to determine
 the bias between the software and the standard paper measurement. Four individuals measured all frontal and sagittal variables on the 30 X-rays randomly selected on two occasions (test and retest conditions). The Bland–Altman plot was used to determine the degree of agreement between the measurement on paper X-ray and the measurement using Keops® for all reviewers and for the two measures; the intraclass correlation coefficient (ICC) was calculated for each pair of analyses to assess interobserver reproducibility among the four reviewers for the same patient using either paper X-ray or Keops® measurement and finally, concordance correlation coefficient (rc) was calculated to assess intraobserver repeatability among the same reviewer for one patient between the two measure using the same method (paper or Keops®). The mean difference calculated between the two methods was minimal at −0, 4° ± 3.41° [−7.1; 6.4] for frontal measurement and 0.1° ± 3.52° [−6.7; 6.8] for sagittal measurement. Keops® has a better interobserver reproducibility than paper measurement for determination of the sagittal pelvic parameter (ICC = 0.9960 vs. 0.9931; p = 0.0001). It has a better intraobserver repeatability than paper for determination of Cobbs angle (rc = 0.9872 vs. 0.9808; p < 0.0001) and for pelvic parameter (rc = 0.9981 vs. 0.9953; p < 0.0001). We conclude that Keops® has no bias compared to the traditionally paper measurement, and moreover, the repeatability and the reproducibility of measurements with this method is much better than with similar standard radiologic measures done manually in both frontal and sagittal plane and that the use of this software can be recommended for clinical application. Diagnostic, level III.

C. Heyberger

Papers

Reproducibility and repeatability of a new computerized software for sagittal spinopelvic and scoliosis curvature radiologic measurements: Keops ®