Purpose T1 pelvic angle (TPA) and global tilt (GT) are spinopelvic parameters that account for trunk anteversion and pelvic retroversion. To investigate spinopelvic parameters, especially TPA and GT, in Japanese adults and determine norms for each parameter related to health-related quality of life (HRQOL). Materials and methods Six hundred and fifty-six volunteers (262 men and 394 women) aged 50–92 years (mean, 72.8 years) were enrolled in this study. The incidence of vertebral fracture, spondylolisthesis and coronal malalignment were measured. Five spinopelvic parameters (TPA, GT, sagittal vertical axis [SVA], pelvic tilt [PT], and pelvic incidence-lumbar lordosis [PI-LL]) were measured using whole spine standing radiographs. The mean values for each parameter were estimated by sex and decade of life. HRQOL measures, including the Oswestry Disability Index (ODI) and EuroQuol-5D (EQ-5D), were also obtained. Pearson’s correlation coefficients were determined between each parameter and HRQOL measure. Moreover, the factors contributing to the QOL score were calculated using logistic regression with age, sex, the existence of vertebral fracture and spondylolisthesis, coronal malalignment (coronal curve >30°) and sagittal malalignment (SVA >95 mm) as explanatory variables and the presence of disability (ODI >40) as a free variable. Results The mean values for the spinopelvic parameters were as follows: TPA, 17.9°; GT, 23.2°; SVA, 50.2 mm; PT, 18.6°; and PI-LL, 7.5°. TPA and GT strongly correlated with each other (r = 0.990) and with the other spinopelvic parameters. TPA and GT correlated with ODI (r = 0.339, r = 0.348, respectively) and EQ-5D (r = −0.285, r = −0.288, respectively), similar to those for SVA. TPA, GT, PT, and PI-LL were significantly higher in women than in men. PT and PI-LL gradually increased with age, while TPA, GT, and SVA tended to deteriorate after the 7th decade. Based on a logistic regression analysis, the deterioration of ODI was mostly affected by the sagittal malalignment. The TPA and GT cut-off values for severe disability (ODI >40) based on linear regression modeling were 26.0° and 33.7°, respectively. Conclusions We determined reference values for spinopelvic parameters in elderly volunteers. Similar to SVA, TPA and GT correlated with HRQOL. TPA, GT, PT, and PI-LL were worse in women and progressed with age.

Study Design. Retrospective review. Objective. We investigated validity of T1 pelvic angle (TPA) for postoperative assessment and determined its target value for corrective scoliosis surgery. Summary of Background Data. TPA is a novel spinopelvic parameter accounting for both pelvic retroversion and trunk anteversion. As an angle, it is less affected by posture and correlates well with health-related quality of life in adult spinal deformity patients. According to our study in elderly volunteers, the threshold TPA value for disability (Oswestry Disability Index [ODI] score >20) was approximately 20°. Methods. Seventy adult scoliosis patients (5 men and 65 women; mean age, 67.8 yr) who underwent spinal deformity surgeries and were followed up for at least 2 years postoperatively were studied. The following parameters based on whole-spine and pelvic radiography were assessed preoperatively, soon after operation, and 2 years postoperatively: C7-central sacral vertical line, TPA, sagittal vertical axis (SVA), pelvic tilt, and pelvic incidence minus lumbar lordosis. ODI and Scoliosis Research Society-22 scores were obtained preoperatively and 2 years postoperatively. Based on postoperative TPA, patients were divided into two groups: ≤20° (group G) and greater than 20° (group P). Results. TPA and SVA correlated with health-related quality of life. Two years postoperatively, TPA best correlated with ODI and Scoliosis Research Society-22 scores, although all parameters correlated with them, and TPA soon after operation best correlated with ODI scores 2 years postoperatively. Two years postoperatively, each parameter and ODI scores in group G were better than those in group P. Conclusion. The correlation results showed that TPA appropriately assessed clinical outcomes following spinal deformity surgery. TPA assessed soon after operation correlated with ODI score 2 years postoperatively, and thus predicted prognosis. Because patients whose postoperative corrected TPA was 20° or lesser had better spinopelvic parameters and ODI scores 2 years postoperatively, TPA 20° or lesser was the proper target value for corrective surgery. Level of Evidence: 4

A retrospective study. To investigate the incidence of iliac screw loosening with a two-rod vs. multi-rod construct and the effect on clinical and radiographic outcomes after surgery for adult spinal deformity (ASD). Multi-rod construct is useful for preventing rod fracture in ASD surgery. However, limited information is available regarding the incidence of iliac screw loosening after corrective fusion surgery using a multi-rod construct. Total 106 patients with ASD (24 men and 82 women; mean age, 68 years) who underwent corrective fusion surgery using bilateral iliac screws and were followed up for at least 1 year were reviewed. The following variables were compared between patients who underwent surgery with a two-rod and multi-rod construct: age, sex, bone mineral density (BMD), fusion level, high-grade osteotomy, L5/S interbody fusion, screw loosening (upper instrumented vertebra [UIV], S1, and iliac), rod fracture, proximal junctional kyphosis, spinopelvic parameters, and Oswestry Disability Index (ODI) score. We also compared patients with and without iliac screw loosening in the multi-rod construct group. Of the 106 patients, 55 underwent surgery with a conventional two-rod construct and 51 with a multi-rod construct (three rods in 16, four rods in 35). Iliac and UIV screw loosening was observed in 24 patients (21%) and 35 patients (33%), respectively. The multi-rod group showed significantly higher incidence of iliac and UIV screw loosening and lower incidence of rod fracture. Patients with iliac screw loosening had a lower BMD than those without screw loosening; however, no significant differences were observed in the spinopelvic parameters or the ODI score. The use of multi-rod constructs led to a higher incidence of junctional screw loosening than the use of conventional two-rod constructs, especially in patients with osteoporosis. Iliac screw loosening did not affect sagittal alignment or clinical outcome in the short term.