(C-106) Low Back Pain (LBP) Protocol Development: Integrating Inertial Measurement Units (IMUs), Markerless Motion Capture, and Pain Reports

Low back pain (LBP) is the most common health problem, affecting 80% of the global population across all age groups[1].  Due to the majority of low back pain being unrelated to imaging results, approximately 40-80% of LBP patients are misdiagnosed[2].  Further, the complexity of the spinal structure, consisting of 33 vertebrae, adds to the challenges of diagnosis.  The majority of motion analysis studies for LBP focus solely on the lumbar spine limiting understanding of overall spinal motion[1,3,4].  However, the spinal and lower extremity are interconnected, with the hip being connected to the spine and creating leg motion[3], and many patients experiencing both spine and hip pain simultaneously[1,5].  For this reason, studying total spinal motion with lower extremity motion can improve our understanding of the source of LBP.  This study aims to develop a comprehensive protocol that combines the use of eight Inertial Measurement Units (IMUs) to analyze spinal motion during specific activities, full-body markerless motion capture technology (Theia3D) to examine lower extremity motion, and a Pain Button App, developed in our lab, for patients to record pain levels during motion (Figure 1). 

Linear acceleration and angular velocity of spinal segments will be obtained with wearable IMUs sensors.  A precise positioning method was developed to place two IMUs adjacent to the spine in four locations, using a ratio of ⅓ and ⅔ from C7 to L4 vertebrae (Figure 1a).  To ensure accurate data collection, preliminary testing was conducted.  Controlled dynamic tests were performed to assess the accuracy and reliability of the IMUs, such as moving a sensor to a known distance and rotating its axis frame.  Noise filtering and integrating were used to process the data to approximate position and verify whether the sensors achieved the known displacement.  Additionally, a patient protocol was established outlining a step-by-step process to be followed by the researcher during every trial for precise data collection.  The protocol describes three activities the patient will perform: sit-to-stand, trunk range of motion (ROM), and gait activities.  This will allow for a comprehensive understanding of how the hip and spine function together to facilitate motion.  The implementation of Theia3D and the Pain Button App enables comprehensive full-body motion analysis, while also allowing patients to record their pain levels by providing data on timing and intensity.

The results of our preliminary tests confirm the accuracy of the rotation matrix applied to the gyroscope and acceleration data, ensuring consistent alignment with the world frame and accounting for the gravitational force (Figure 2). This novel protocol will allow for data collection that can provide motion analysis input for spinal and lower extremity motion metrics. These metrics and relationship to pain will be used to distinguish three groups: a control group, individuals with chronic LBP, and individuals with chronic LBP accompanied by hip pain.  The next steps include performing statistical analysis to identify motion patterns that lead to pain that can be used to improve diagnostic tools. 

This study was supported by the University of California Leadership Excellence through Advanced Degrees (UC LEADS) program and UC Skeletal Research Enhancing Training Collaboration & Health (STRETCH).   Special thanks to Professor Grace O’Connell, Professor Jeannie Bailey, Erin Archibeck, and Yarah Feteih.

References: 

[1] Wong, T. K. T., & Lee, R. Y. W. (2004). Effects of low back pain on the relationship between the movements of the lumbar spine and hip. Human Movement Science, 23(1), 21–34. https://doi.org/10.1016/j.humov.2004.03.004

[2] Hendler, N. (2016). Why chronic pain patients are misdiagnosed 40 to 80% of the time. J Recent Adv Pain, 2(3), 94-98.

[3] Eftekhary, N., Shimmin, A., Lazennec, J. Y., Buckland, A., Schwarzkopf, R., Dorr, L. D., ... & Vigdorchik, J. (2019). A systematic approach to the hip-spine relationship and its applications to total hip arthroplasty. The Bone & Joint Journal, 101(7), 808-816.

[4] Sembrano, J. N., & Polly, D. W., Jr (2009). How often is low back pain not coming from the back?. Spine, 34(1), E27–E32. https://doi.org/10.1097/BRS.0b013e31818b8882

[5] Parvizi, J., Pour, A. E., Hillibrand, A., Goldberg, G., Sharkey, P. F., & Rothman, R. H. (2010). Back pain and total hip arthroplasty: a prospective natural history study. Clinical orthopaedics and related research, 468(5), 1325–1330. https://doi.org/10.1007/s11999-010-1236-5

[6] The bones of the lower body by Medicalrf.com. Photos.com. (n.d.). https://photos.com/featured/5-the-bones-of-the-lower-body-medicalrfcom.html 

[7] Fun Facts for Kids on Animals, Earth, history and more!. DK Find Out! (n.d.). https://www.dkfindout.com/uk/human-body/skeleton-and-bones/ 

[8] Markerless motion capture redefined. Theia Markerless. (2022, August 31). https://www.theiamarkerless.ca/