A videofluoroscopy-based tracking algorithm for quantifying the time course of human intervertebral displacements

Abstract

The motions of individual intervertebral joints can affect spine motion, injury risk, deterioration, pain, treatment strategies, and clinical outcomes. Since standard kinematic methods do not provide precise time-course details about individual vertebrae and intervertebral motions, information that could be useful for scientific advancement and clinical assessment, we developed an iterative template matching algorithm to obtain this data from videofluoroscopy images. To assess the bias of our approach, vertebrae in an intact porcine spine were tracked and compared to the motions of high-contrast markers. To estimate precision under clinical conditions, motions of three human cervical spines were tracked independently ten times and vertebral and intervertebral motions associated with individual trials were compared to corresponding averages. Both tests produced errors in intervertebral angular and shear displacements no greater than 0.4° and 0.055 mm, respectively. When applied to two patient cases, aberrant intervertebral motions in the cervical spine were typically found to correlate with patient-specific anatomical features such as disc height loss and osteophytes. The case studies suggest that intervertebral kinematic time-course data could have value in clinical assessments, lead to broader understanding of how specific anatomical features influence joint motions, and in due course inform clinical treatments.

Keywords:

• Vertebral tracking
• fluoroscopy
• cross-correlation
• intervertebral motions
• intervertebral shear

Acknowledgements

The authors gratefully acknowledge Dr. Edward Cambridge D.C. for his assistance in grading patient disc height loss. No commercial relationships or conflicts of interest exist in this work. Dr. John W. Baird holds the rights to the ‘Digital Motion X-ray (DMX)’ trademark in Canada.