Concrete use of the joint coordinate system for the quantification of articular rotations in the digital joints of the horse.

This research paper presents a method for accurate quantification of three-dimensional joint movements in horse limbs, which was tested using various in vitro scenarios.

Methodology

• The researchers model each joint in a horse’s digit (finger/toe) as a series of three single-axis rotating joints.
• The ‘Joint Coordinate System’ is used to gather data on movements. This system utilises a specific sequence of cardanic angles (three angles that, together with their three axes of rotation, describe the orientation of an object in 3D space).
• The researchers choose to decompose the angles in a way such that the three basic angles line up with the expected movements: flexion/extension, passive abduction/adduction (sideways movement), and lateral/medial rotations (rotations towards and away from the centreline of the body).
• Procedures and algorithms were outlined specifically for the equine front digital joints, the joints in the fingers of a horse’s front limbs.

Testing Procedure

• Four forelimbs were tested in vitro, or outside a living body.
• Each limb was loaded with a press, applying pressure between 500 and 6000 Newtons. Angle values during this process were measured for analysis.
• Tests were then repeated, but this time a wedge was used to raise a portion of the hoof (toe, heel, lateral or medial side), causing modifications in the angular patterns of the joints.

Results and Implications

• The method allowed for precise quantitative determination of 3D joint movements. It revealed noticeable changes in joint angles when the wedge was applied.
• This data both affirms, and gives more precise measurements for, previously semi-quantitative observations.
• Thus, the method provides a tool for gathering objective data on the functional anatomy of joints. It could be particularly helpful to scientists wanting to study the effects of shoeing on horse hooves.
• Furthermore, it has potential application beyond horses, and could be used for investigating minor joint movements in other species, particularly movements that occur outside the sagittal plane (the vertical plane which divides the body into right and left halves).