Anatomical Pelvic Parameters Using the Anterior Pelvic Plane: Normative Values and Estimation of the Standing Sagittal Alignment in Healthy Volunteers

Masayuki Ohashi; Kazuhiro Hasegawa; Shun Hatsushikano; Norio Imai; Hideki Tashi; Tatsuo Makino; Keitaro Minato; Masayuki Sato; Kei Watanabe

doi:10.22603/ssrr.2023-0181

Anatomical Pelvic Parameters Using the Anterior Pelvic Plane: Normative Values and Estimation of the Standing Sagittal Alignment in Healthy Volunteers

Spine Surg Relat Res. 2023 Nov 2;8(1):97-105. doi: 10.22603/ssrr.2023-0181. eCollection 2024 Jan 27.

Authors

Masayuki Ohashi¹, Kazuhiro Hasegawa², Shun Hatsushikano², Norio Imai³, Hideki Tashi⁴, Tatsuo Makino¹, Keitaro Minato¹, Masayuki Sato¹, Kei Watanabe^{1

2}

Affiliations

¹ Division of Orthopedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
² Niigata Spine Surgery Center, Niigata, Japan.
³ Division of Comprehensive Geriatrics in Community, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
⁴ Division of Musculoskeletal Science for Frailty, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.

Abstract

Introduction: In this study, we aim to estimate the natural standing sagittal alignment in patients with adult spinal deformity (ASD), firstly by investigating the normative values of anatomical pelvic parameters based on the anterior pelvic plane (APP) in a healthy population, and to clarify the relationships between the anatomical and positional pelvic parameters in standing position.

Methods: The images of biplanar slot-scanning full-body stereoradiography in 140 healthy Japanese volunteers (mean age, 39.5 years; 59.3% female) were examined. In addition to three-dimensional measurements including pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT), the APP angle (APPA; anterior tilting=positive) was measured as the angle between the APP and the vertical line using the two-dimensional lateral image. Anatomical SS and PT (aSS and aPT) were calculated as the angles of SS and PT in reference to APP.

Results: The mean (range) values of APPA, aSS, and aPT were determined to be 0.7° (-16.8°/15.5°), 36.8° (18.3°/64.9°), and 13.2° (-0.6°/28.7°), respectively. Moreover, SS was found to be significantly correlated with PI and aSS, while PT was significantly correlated with PI, aSS, aPT, and body weight. Also, PT was significantly larger in females than in males. Multiple linear regression analysis deduced the following equations: SS=0.404×aSS+0.203×PI+12.463, PT=-0.391×aSS+0.774×PI+1.950×sex (male=0, female=1)-12.971, wherein aSS had the greatest effect for predicting SS among the included factors and PI had the greatest effect for predicting PT. In addition, no significant differences were noted between PT/PI and aPT/PI.

Conclusions: As per the results of this study, significant correlations were noted among parameters and predicting models for positional parameters (SS and PT) using anatomical parameters (aSS and aPT) in a healthy population. This novel measurement concept based on the APP has been considered to be useful in estimating natural SS and PT in standing position using the anatomical pelvic parameters in patients with ASD.

Keywords: anatomical parameter; anterior pelvic plane; pelvic incidence; pelvic tilt; sacral slope; standing sagittal alignment.