Non-invasive assessment of sacroiliac joint and lumbar spine positioning in different unilateral sitting postures

ABSTRACT

Background

Sacroiliac joint (SIJ) motion has been documented using invasive and noninvasive kinematic techniques. No study has explored SIJ angular positions in functional postures using noninvasive techniques. The purpose of this study was to quantify SIJ positioning among different seated postures in a healthy population.

Methods

Twelve female and 11 male healthy young participants participated. Left and right anterior and posterior superior iliac spines were manually digitized during standing, neutral sitting and four different seated postures. Rigid bodies recorded the kinematics of the lumbar spine. Angles calculated included transverse sacroiliac angle, innominate sagittal angle, sacral tilt, lumbar flexion-extension, lumbar lateral bend and lumbar axial twist.

Findings

The observed range of angular positions was approximately 3 to 4 degrees across the SIJ-related angles. The main effect of seated posture was observed for all angles measured. The main effect of sex was observed for all angles except lumbar lateral bending. Females consistently experienced more posterior sacral tilt than males. Interaction effects between sex and posture were only observed at the right-transverse sacroiliac angle and sacral tilt. Previous sitting posture affected the subsequent neutral sitting posture for the right-transverse sacroiliac angle and lumbar spine angle.

Interpretation

SIJ angular position differences among the seated postures were similar in magnitude to motions previously reported in participants undergoing prone passive hip abduction and external rotation. Sex differences, including greater sacral posterior tilt observed in females, likely reflect underlying morphological and physiological differences. Future studies should explore SIJ positioning during functional tasks in pathological populations to help elucidate the underlying causes of SIJ pain and inform treatment strategies.

KEYWORDS:

• Pelvis
• sacrum
• spine
• trunk
• innominate bone
• motion

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This project was funded by the Natural Sciences and Engineering Council (NSERC) of Canada.

Notes on contributors

Sara Riazi

Sara Riazi is a graduate of McMaster University's Masters of Physiotherapy program. Prior to this, Sara completed her Master of Science in Biomechanics and her Bachelor of Science in Human Kinetics at the University of Guelph. She is currently working as a full-time physiotherapist in a private practice orthopedic clinic. Her clinical interests include lower back, sacroiliac joint and sport-related injuries.

Olena Klahsen

Olena Klahsen earned her Hon. Bachelor of Biological Science at the University of Guelph. She then earned her MSc at the University of Guelph with a research focus on the injury induced spinal degeneration. She is currently completing her PhD at the University of Ottawa with a research focus on the physiological impacts of aging on female pelvic floor musculature.

Merwa Al-rasheed

Merwa Al-Rasheed received her B.Eng degree in Biomedical Engineering from the University of Guelph. She completed her MASc. in System Design Engineering at the University of Waterloo. She is currently working as an R&D Biomedical Engineer in wearable biomedical technology. Her current research interests include computational modeling of human motion and understanding injury mechanisms in bones.

Shawn m. Beaudette

Shawn M. Beaudette is an Assistant Professor in the Department of Kinesiology at Brock University (St. Catharine, Ontario, Canada). He received his PhD in Spine and Muscle Biomechanics from the University of Guelph (2018). After graduating from Guelph, he worked as a post-doctoral fellow in the School of Human Kinetics at the University of Ottawa (2018–2019) specializing in data science and machine learning. At Brock University, Shawn is affiliated with the Centres for Bone and Muscle Health, and Neuroscience. His research program aims to understand the neuromechanical factors contributing to spine (dys)function. Specifically, his work aims to develop non-invasive and objective approaches to improve the diagnosis, treatment, performance, and rehabilitation of the lower back.

Stephen h. m. Brown

Stephen H. M. Brown received his Bachelors and Masters at the University of Windsor, his PhD at the University of Waterloo and did a post-doctoral fellowship at the University of California, San Diego. He has been at the University of Guelph since 2010 and is currently an Associate Professor. Dr. Brown’s research is focused on the functional biomechanics and physiology of the lumbar spine and spine musculature, as well as muscle function and control. This study allows for further investigation into injury, adaptation and rehabilitation of the lumbar spine and associated tissues.