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How Many Trials Are Needed to Estimate Typical Lumbar Movement Patterns During Dynamic X-Ray Imaging?
Ameet Aiyangar1, Tom Gale2, Sabreen Magherhi2
1Mechanical Systems Engineering, Empa - Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, Duebendorf, Zürich 8600, Switzerland; Biodynamics Lab, Department of Orthopaedic Surgery, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA 15203.
Dynamic biplane radiographic (DBR) imaging offers insights into vertebral motion. Collecting at least three repetitions minimizes uncertainty and radiation exposure, improving the reliability of DBR metrics for lower back disorder analysis.
Area of Science:
- Biomechanics
- Radiographic Imaging
Background:
- Dynamic biplane radiographic (DBR) imaging enables accurate measurement of vertebral motion during functional tasks.
- DBR has potential for developing novel biomechanical markers for lower back disorders, moving beyond static measurements.
- Reliability concerns exist due to movement variability and radiation exposure from repeated DBR measurements.
Purpose of the Study:
- To determine the margin of uncertainty (MOU) in estimating intervertebral kinematics waveforms from limited movement repetitions.
- To assess the day-to-day repeatability of intervertebral kinematics waveforms measured using DBR.
- To optimize DBR data acquisition protocols for reliable and safe clinical application.
Main Methods:
- Lumbar spine kinematics data were collected from two participant groups performing functional tasks (flexion-extension, lateral bending).
- Group 1 performed ten repetitions on a single day to estimate MOU as a function of repetition number.
- Group 2 performed five repetitions on two separate days to assess day-to-day repeatability.
Main Results:
- Margin of uncertainty (MOU) was specific to movement type and spinal motion segment.
- Using only one or two trials resulted in high MOU (>4 degrees or 4 mm).
- Collecting at least three repetitions reduced MOU by over 40%, enhancing measurement reproducibility.
Conclusions:
- Reproducibility of DBR-derived measurements is significantly improved by acquiring a minimum of three repetitions.
- This approach enhances measurement reliability while minimizing participant radiation exposure.
- Optimized DBR protocols with at least three repetitions are recommended for clinical use.
