Effect of dorsopalmar projection obliquity on radiographic measurement of distal phalangeal rotation angle in horses with laminitis.

The researchers studied how the angle at which an x-ray is taken (dorsopalmar projection obliquity) affects the measurement of the rotation of the last bone in a horse’s foot (distal phalangeal rotation) associated with a debilitating and potentially fatal horse disease called laminitis.

Study Participants and Method

• The researchers selected 8 feet from 5 horses euthanized due to laminitis for this study.
• A true lateromedial view of each foot was taken. This served as the reference or baseline for further studies.
• Additionally, x-ray views of the feet were taken at different angles: 5, 10, 15, and 20 degrees rotation of the x-ray tube head, in both a dorsal (from back to front) and a palmar (from front to back) direction.

Findings

• The study found that dorsopalmar projection obliquity consistently underestimated the distal phalangeal rotation (DPR) angle, indicating that the angle at which the x-ray is taken could affect diagnosis.
• Differences in DPR angle measurements were found to be significant when the projection obliquity exceeded 10 degrees, suggesting that accurate imaging is necessary for correct understanding of the condition.
• The degree to which the DPR was underestimated did not seem to depend on the severity of the rotation. This implies that the effect of projection obliquity on DPR measurement is independent of the seriousness of the laminitis in the horse.

New Radiographic Variable

• The researchers defined and measured a new radiographic variable called ‘the mean normalized intercondylar distance’ on 13 horse feet.
• This new variable was introduced to help estimate the angle of projection obliquity in routine clinical studies, which could assist practitioners in more accurate diagnosis and treatment planning for horses suffering from laminitis.