An analysis on the determinants of head to pelvic balance in a Chinese adult population

Zongshan Hu; Claudio Vergari; Laurent Gajny; Gene Chi-Wai Man; Kwong-Hang Yeung; Zhen Liu; Tsz-Ping Lam; Zezhang Zhu; Yong Qiu; Winnie Chiu-Wing Chu; Jack Chun-Yiu Cheng; Wafa Skalli

doi:10.21037/qims-21-718

An analysis on the determinants of head to pelvic balance in a Chinese adult population

Quant Imaging Med Surg. 2022 Apr;12(4):2311-2320. doi: 10.21037/qims-21-718.

Authors

Zongshan Hu^#^{1

2

3}, Claudio Vergari^#⁴, Laurent Gajny⁴, Gene Chi-Wai Man^{2

3}, Kwong-Hang Yeung^{3

5}, Zhen Liu¹, Tsz-Ping Lam^{2

3}, Zezhang Zhu^{1

3}, Yong Qiu^{1

3}, Winnie Chiu-Wing Chu^{3

5}, Jack Chun-Yiu Cheng^{2

3}, Wafa Skalli⁴

Affiliations

¹ Department of Spine Surgery, Drum Tower Hospital of Nanjing University Medical School, Nanjing, China.
² Department of Orthopaedics and Traumatology, The Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
³ The Joint Scoliosis Research Center of the Chinese University of Hong Kong-Nanjing University, Faculty of Medicine, The Chinese University of Hong Kong Hong Kong, China.
⁴ Arts et Métiers Institute of Technology, Université Sorbonne Paris Nord, IBHGC-Institut de Biomécanique Humaine Georges Charpak, HESAM Université, F-75013, Paris, France.
⁵ Department of Imaging and Interventional Radiology, The Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.

^# Contributed equally.

Abstract

Background: Balanced global spinopelvic balance is important in the maintenance of the physiological alignment of all body segments above the pelvis with minimum energy expenditure. The key determinants affecting the 3D index-odontoid-hip axis (OD-HA) angle, and in particular its alterations, have not been clearly defined. The aim of this study is to identify the determinants of the 3D OD-HA angle in maintaining global spinopelvic balance in a large Chinese adult cohort of different gender and age groups.

Methods: A total of 516 asymptomatic adults were enrolled in this study. Biplanar radiographies were performed to reconstruct the subject's inter-acetabular axis and C2 odontoid process. The 3D angle formed by the vertical and the line between odontoid and mid-interacetabular axis (OD-HA angle) was computed and projected in the subject's sagittal and coronal planes. Thoracic kyphosis (TK), lumbar lordosis (LL), T1 pelvic angle (TPA) and sagittal vertical axis (SVA) were measured.

Results: The mean values of sagittal and coronal OD-HA were -0.2°±2.5° and 0.2°±1.1°, respectively. Both sagittal and coronal OD-HA had significant correlation with age (r=0.265 and r=-0.143, P<0.01, respectively), sagittal OD-HA showed increment from 20s to 80s (-1.3° to 0.8° for female, -0.3° to 1.5° for male) and a significant difference between male and female from 20 to 69 years old. Further analysis showed that sex, weight, TK, PT, SVA, TPA and ODI were determinants of OD-HA.

Conclusions: 3D OD-HA angle showed physiological stability with little variability from young to elderly adults, with SD of 2.45° and 1.06° in sagittal and coronal planes, respectively. OD-HA angle confirms the hypothesis that the head tends to remain above the pelvis in a small cone of stability. This study provides an analysis of the determinants of OD-HA and the reference range of the head-pelvis balance in each decade and gender based on a large-scale asymptomatic population.

Keywords: 3D reconstruction; adult; asymptomatic; odontoid-hip axis (OD-HA); postural alignment.