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OBJECT Previous forceplate studies analyzing the impact of sagittal-plane spinal deformity on pelvic parameters have demonstrated the compensatory mechanisms of pelvis translation in addition to rotation. However, the mechanisms recruited for this pelvic rotation were not assessed. This study aims to analyze the relationship between spinopelvic and lower-extremity parameters and clarify the role of pelvic translation. METHODS This is a retrospective study of patients with spinal deformity and full-body EOS images. Patients with only stenosis or low-back pain were excluded. Patients were grouped according to T-1 spinopelvic inclination (T1SPi): sagittal forward (forward, > 0.5°), neutral (−6.3° to 0.5°), or backward (< −6.3°). Pelvic translation was quantified by pelvic shift (sagittal offset between the posterosuperior corner of the sacrum and anterior cortex of the distal tibia), hip extension was measured using the sacrofemoral angle (SFA; the angle formed by the middle of the sacral endplate and the bicoxofemoral axis and the line between the bicoxofemoral axis and the femoral axis), and chin-brow vertical angle (CBVA). Univariate and multivariate analyses were used to compare the parameters and correlation with the Oswestry Disability Index (ODI). RESULTS In total, 336 patients (71% female; mean age 57 years; mean body mass index 27 kg/m2) had mean T1SPi values of −8.8°, −3.5°, and 5.9° in the backward, neutral, and forward groups, respectively. There were significant differences in the lower-extremity and spinopelvic parameters between T1SPi groups. The backward group had a normal lumbar lordosis (LL), negative SVA and pelvic shift, and the largest hip extension. Forward patients had a small LL and an increased SVA, with a large pelvic shift creating compensatory knee flexion. Significant correlations existed between lower-limb parameter and pelvic shift, pelvic tilt, T-1 pelvic angle, T1SPi, and sagittal vertical axis (0.3 < r < 0.8; p < 0.001). ODI was significantly correlated with knee flexion and pelvic shift. CONCLUSIONS This is the first study to describe full-body alignment in a large population of patients with spinal pathologies. Furthermore, patients categorized based on T1SPi were found to have significant differences in the pelvic shift and lower-limb compensatory mechanisms. Correlations between lower-limb angles, pelvic shift, and ODI were identified. These differences in compensatory mechanisms should be considered when evaluating and planning surgical intervention for adult patients with spinal deformity.

CBVA, chin-brow vertical angleHRQoL, health-related quality of lifeMcGS, slope of McGregor's lineODI, Oswestry Disability IndexSLs, slope of the line of sight.

Because children are notably more sensitive to the carcinogenic effects of ionizing radiation, judicious use of imaging methods and a search for newer technologies remain necessary. Results of the current study show that the new microdose acquisition protocol can be used in clinical practice without altering the quality of the images. Relevant clinical measurements can be made manually, but the landmarks are also visible enough to allow accurate 3D reconstructions (ICC >0.91 for all parameters). The resulting radiation exposure was 5.5 times lower than that received with the prior protocol, corresponding now to a 45-fold reduction compared to conventional radiographs, and can, therefore, almost be considered negligible.

Predominance of high PI and female gender was emphasized in DS population. Moreover, these findings highlighted the importance of sagittal alignment analysis in DS with 24 % of patients with anterior malalignment and in the remaining 76 % (normal C7Tilt), more than 50 % had pelvic retroversion. Consequently, DS sagittal malalignment should lead to specific surgical correction adapted to each subgroup of patients.

PJK is a frequent complication in thoracic AIS, occurring 16%, but remains often asymptomatic (less than 3% of revisions in the entire cohort). An interesting finding is that patients with high pelvic incidence and consequently large LL and TK were more at risk of PJK. As demonstrated in ASD, one of the causes of PJK might be postoperative posterior imbalance that can be due to increased LL, insufficient TK or inflection point shift during surgery. These slides can be retrieved under Electronic Supplementary Material.

CoCr and Ti rods both provide significant and stable frontal correction in AIS treated with posteromedial translation technique using hybrid constructs. However, CoCr might be considered to emphasize sagittal correction in hypokyphotic patients.