The proximal aspect of the suspensory ligament in the horse: How precise are ultrasonographic measurements?
Authors: Zauscher J M, Estrada R, Edinger J, Lischer C J
Journal: Equine veterinary journal
Summary
# Editorial Summary: Ultrasonographic Measurement Precision of the Equine Proximal Suspensory Ligament Accurate ultrasonographic assessment of the proximal suspensory ligament (PSL) is fundamental to diagnosing and monitoring soft tissue injury in horses, yet the reliability of various measurement techniques remains unclear. Zauscher and colleagues examined intra- and interobserver variability by having two operators perform repeated ultrasound examinations of the PSL in all four limbs of 14 horses using different probes and scanning protocols, then applying statistical agreement indices and limits of agreement to evaluate measurement consistency. Dorsopalmar/-plantar thickness measurements demonstrated excellent reliability in both longitudinal and transverse planes, with agreement indices ≥0.89 and acceptable limits of agreement, whereas lateromedial width, cross-sectional area and circumference showed considerably higher variability regardless of imaging technique, with limits of agreement exceeding clinical target thresholds. The authors noted that since a minimum 20% difference is required to reliably distinguish physiological variation from pathological change, the poor precision of transverse measurements for these latter parameters substantially limits their clinical utility for objective PSL assessment. Practitioners should therefore restrict their quantitative PSL evaluations to dorsopalmar/-plantar thickness measurements, whilst being cautious about relying on transverse-plane measurements of width, area or circumference for longitudinal monitoring or prognostic decision-making.
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Practical Takeaways
- •Only dorsopalmar/-plantar thickness measurements are sufficiently reliable for clinical monitoring; avoid relying on transverse plane measurements of width, area, and circumference for diagnostic decision-making
- •When using ultrasound to assess PSL changes over time, expect measurement variability and require at least 20% change before concluding true pathology development
- •Forelibs yield more reproducible measurements than hindlimbs; use consistent scanning technique and operator when possible, particularly for hindlimb assessment
Key Findings
- •Dorsopalmar/-plantar thickness measurements achieved acceptable precision (AI ≥0.89) in both longitudinal and transverse planes for intra- and interoperator reliability
- •Lateromedial width, cross-sectional area, and circumference on transverse imaging showed higher variability with 95% LOA exceeding target values regardless of technique
- •Forelibs demonstrated better measurement precision than hindlimbs across all parameters
- •A minimum 20% difference is required to reliably distinguish physiological from pathological changes in PSL dimensions