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

Overview

• This study validated measurable radiographic parameters to quantitatively assess the shape and structure of carpal and metacarpal bones in growing Thoroughbred foals.
• It confirmed that standardized X-ray measurements of bone angles and cortical thicknesses are reliable and reproducible when done by different observers, providing baseline data for future research on foal bone development and injury risk.

Introduction and Purpose

• Radiographic morphometry refers to quantifying bone shape and structure using X-ray images. It helps in objectively evaluating bone conformation and abnormalities.
• While these measurements are established for mature horses, they had not been validated for foals, whose bones are still growing and may show different features.
• The study’s main goals were to:
• Assess repeatability and reproducibility of carpal (wrist) and third metacarpal (MC3) bone measurements in foals.
• Establish baseline conformational data for these bones in young Thoroughbred horses.

Methodology

• Subject Selection and Timeline:
• Twenty Thoroughbred foals were studied from birth to 14 months of age.
• Radiographs were taken at two-month intervals without sedation to avoid stress or movement affecting images.
• Radiographic Techniques:
• Dorsopalmar views of the carpal region and lateromedial views of the third metacarpal bone were obtained following standardized imaging protocols.
• Parameters Measured:
• Fifteen individual angular measurements of carpal bones (angles describing bone alignment and relationships).
• Eleven relative angular carpal parameters (comparisons or ratios of angles).
• Three cortical (outer bone layer) dimensions measured on the third metacarpal (MC3) bone.
• Measurement Protocol:
• Two evaluators independently measured each parameter three times to test intra- (same evaluator repeated measures) and inter-rater (between different evaluators) reliability.
• Statistical Analysis:
• Intra-class correlation coefficients (ICC) evaluated the consistency of measurements within and between raters.
• Bland-Altman analyses assessed agreement and bias in measurements.

Results

• Feasibility:
• All radiographic parameters could be successfully measured in live foals without sedation.
• Intra-rater Repeatability (same evaluator reliability):
• 6 of 15 individual carpal angular parameters showed excellent repeatability (ICC > 0.9), indicating measurements were highly consistent when repeated by the same person.
• All MC3 cortical bone measurements had excellent intra-rater repeatability (ICC > 0.9), showing strong measurement stability.
• Inter-rater Repeatability (between evaluators reliability):
• Eight individual carpal angular parameters and six relative carpal parameters showed excellent agreement between different evaluators.
• MC3 cortical dimensions had excellent inter-rater agreement (ICC > 0.9) with very low bias (≤ 0.09 mm), indicating measurements were reliably reproduced by different raters.

Conclusions and Implications

• The study demonstrates that standardized radiographic methods and measured parameters previously used for mature horses are applicable for foals.
• Validated measurements of carpal angles and MC3 cortical dimensions are reliable tools for quantitatively assessing bone conformation during growth phases in foals.
• Baseline conformational data established in this study provide a useful reference for future research regarding skeletal growth patterns.
• The findings support using radiographic morphometry as an objective method to investigate:
• Normal developmental changes in young Thoroughbred horses.
• Potential links between bone conformation and risk of injury or musculoskeletal disorders in foals.
• Applications in breeding, management, and veterinary assessment of young horses.