The proximal aspect of the suspensory ligament in the horse: How precise are ultrasonographic measurements?

This study assesses the precision of ultrasonographic measurements of a horse’s proximal suspensory ligament by comparing the variability in measurements made by two operators. It shows that the most accurate measurements were those taken of the dorsopalmar/-plantar thickness, while other measurements showed significant variability.

Objective and Scope

• The researchers’ goal here was to evaluate the reliability and repeatability of ultrasonographic measurements of the proximal aspect of the suspensory ligament (PSL) in horses.
• The study was undertaken in order to differentiate between normal and abnormal measurements associated with physiological changes or pathological alterations in the ligament.
• The study tested intra- (conducted by the same operator) and interobserver (performed by two different operators) variability of the measurements to evaluate their precision.

Methods

• Two operators were involved in the study, examining the PSL of 14 horses twice using different techniques and probes, both with and without standoff pads.
• The measurements were drawn from both longitudinal and transverse images.
• The team assessed the inter- and intraoperator variability using agreement indices (AI) and the 95% limits of agreement (LOA).

Results

• The results revealed that the mean inter- and intraoperator AIs for the dorsopalmar/-plantar thickness were both above 0.89, and the 95% LOA were within target values for most comparisons.
• The study also noted similar AIs and 95% LOA for the dorsopalmar/-plantar thickness on the transverse image.
• However, in the case of lateromedial width, cross-sectional area, and circumference measurements on the transverse image, the mean AIs ranged between 0.81 and 0.95 and the 95% LOA were higher than target values, indicating higher variability.
• Additionally, the forelimbs achieved better AI and LOA values as compared to the hindlimbs.

Conclusions

• The study found that acceptable precision could be achieved in measurements of dorsopalmar/-plantar thickness in both longitudinal and transverse scans.
• However, there was a significant degree of variability with width, cross-sectional area, and circumference measurements, suggesting disproportionate reliability in using these parameters for objective assessment of PSL from transverse ultrasound images.