Validation of measurable radiographic parameters for quantitative assessment of carpal and metacarpal bone morphology...

Radiographic morphometry provides a quantitative means to evaluate bone conformation in horses, yet validation of these parameters in foals has not previously been undertaken. This study aimed to determine the intra- and inter-rater repeatability and reproducibility of established carpal and third metacarpal (MC3) radiographic parameters in Thoroughbred foals and to establish baseline conformational data. Twenty Thoroughbred foals were radiographed without sedation from birth to 14 months of age at two-month intervals. Dorsopalmar carpal and lateromedial MC3 radiographs were obtained using standardised protocols. Fifteen individual and eleven relative angular carpal parameters, along with three MC3 cortical dimensions, were measured three times by two evaluators. Intra-class correlation coefficients (ICC) and Bland-Altman analyses were used to assess reliability. All parameters were measurable in vivo, and intra-rater repeatability was excellent (ICC > 0.9) for 6 of 15 (40%) individual angular carpal and all MC3 variables. Inter-rater repeatability was excellent for eight individual and six relative carpal parameters. MC3 cortical dimensions demonstrated excellent agreement between and within raters (ICC > 0.9; bias ≤ 0.09 mm). These findings indicate that standardised radiographic methods can be reliably applied to foals to quantify carpal and metacarpal conformation. The validated parameters and baseline data established here provide a foundation for future investigations of skeletal growth, conformation, and injury risk in young Thoroughbred horses.