Repeatability of ultrasonographic measurement of cross‐sectional area of the multifidus muscle in the horse
Authors: Symonds Nicolle E., Dart Andrew J., Perkins Nigel R., Burns Gillian, Young Alex C., Bell Robin J. W., Jeffcott Leo B.
Journal: Equine Veterinary Education
Summary
# Editorial Summary Ultrasonographic assessment of multifidus cross-sectional area has been increasingly adopted in equine practice to evaluate back pain and monitor rehabilitation outcomes, yet the technique remains poorly validated in horses despite being adapted from human protocols. Symonds and colleagues examined the repeatability of this measurement across three separate investigations: comparing single-session versus multi-day imaging consistency, evaluating portable versus console ultrasound equipment, and testing measurement reproducibility using dedicated analysis software (OsiriX) at four thoracolumbar sites bilaterally. Whilst measurements demonstrated good-to-excellent repeatability when images were acquired and analysed within a single session, clinically important limitations emerged—inter-day repeatability fell to poor-to-moderate range, and comparing portable with console machines yielded only poor-to-good agreement, suggesting substantial variation in image quality and measurement precision between equipment and across separate occasions. These findings indicate that whilst the ultrasound technique itself shows technical promise under controlled conditions, its current application for tracking longitudinal changes in individual horses or comparing findings across different facilities or visits remains problematic. Practitioners should exercise considerable caution in interpreting multifidus measurements as objective indicators of rehabilitation progress or inter-facility comparisons until standardisation protocols—including equipment specifications, operator training and image acquisition parameters—are more rigorously established.
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Practical Takeaways
- •Ultrasound measurement of multifidus muscle cross-sectional area is not yet reliable enough for clinical monitoring of individual horses over time due to poor day-to-day repeatability
- •If using this technique, standardize equipment (console vs portable machine), operator technique, and imaging protocols rigorously, as measurement variability primarily stems from image acquisition rather than measurement error
- •Current evidence does not support using multifidus ultrasound measurements as a validated diagnostic or monitoring tool for equine back problems until standardization and validation studies with larger populations are completed
Key Findings
- •Ultrasound measurement of multifidus cross-sectional area showed good-to-excellent repeatability within single sessions but poor-to-moderate repeatability across different days
- •Portable ultrasound machines showed poor-to-good repeatability compared to console machines for the same measurements
- •Image measurement using external software (OsiriX) demonstrated good-to-excellent repeatability, suggesting measurement technique is not the limiting factor
- •Inconsistent image acquisition between sessions is the primary source of measurement unreliability, limiting clinical application of this technique