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

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