The effect of induced forelimb lameness on thoracolumbar kinematics during treadmill locomotion.

This study explores the relationship between subtle forelimb lameness in horses and changes in their back movement during walking and trotting. Findings revealed that the lameness affected the horses’ range of motion and vertebral angular motion patterns, especially at a trot, and potentially leads to back and/or neck dysfunction in chronic lameness cases.

Objective and Methodology

• The objective of the research was to quantify how induced subtle forelimb lameness affects thoracolumbar kinematics (the motion of the spine) in horses.
• Six riding horses’ kinematics were measured before and after inducing a Grade 2 lameness on the American Association of Equine Practitioners (AAEP) scale from 1-5.
• The lameness was carefully induced to be reversible so as not to permanently harm the horses.
• Measurements of the horses’ movement were taken while they walked and trotted on a treadmill.
• Ground reaction forces (GRFs), which refer to the force exerted by the ground on a body in contact with it, were calculated for individual limbs.

Results

• When trotting, the horses significantly unloaded the painful limb by 11.5%. Unloading at a walk, however, was not significant.
• Also during trotting, the overall flexion-extension range of back motion increased by 3.3 degrees, a significant change (P<0.05). At a walk, this range decreased by an average of 0.2 degrees.
• Changes to the angular motion patterns of vertebral joints were only recorded at a trot. These changes included an increase in flexion by 0.9 degrees at the T10 vertebral joint (the angle between T6, T10, and T13) during the stance phase when the sound diagonal was in stance, and an increased extension of the thoracolumbar area during the stance of the lame diagonal.
• Subtle forelimb lameness caused a lateral bending of the cranial thoracic vertebral column towards the lame side during stance of the lame diagonal. This is considered statistically significant (P<0.05) and could potentially lead to back and/or neck dysfunction in the case of chronic lameness.

Conclusion

• Subtle forelimb lameness affects the horses’ range of motion and the angular motion patterns of their vertebral joints.
• At a walk, the effect is minimal, but at a trot, the horses’ increase their thoracolumbar range of motion and shift their movement patterns, probably attempting to shift their centre of gravity from the lame side and reduce the force on the affected limb.
• This study has opened up opportunities for future research to explore whether these altered movement patterns lead to dysfunctions in the back and/or neck with chronic lameness.