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

The study investigates the relationship between subtle hindlimb lameness in horses and changes to their back movements. Findings reveal that even slight lameness can lead to significant alterations in the thoracolumbar motion, suggesting that chronic subtle lameness could potentially lead to back dysfunction.

Research Objectives

• The main objective of this research was to examine the effect of induced minor hindlimb lameness on the thoracolumbar kinematics (the study of motion) in horses. The study aims to bridge the gap in knowledge as there are currently no detailed investigations linking hindlimb lameness with altered back movements in horses.

Research Methodology

• Six riding horses were utilized in the study. Their movements were monitored during walking and trotting on a treadmill in both normal conditions and while experiencing pressure on the sole of their left hindlimb.
• This pressure was applied through an established sole pressure model. The changes in their movements and locomotion were then recorded using reflective markers positioned at specific anatomical landmarks.
• The ground reaction forces (GRF) within individual limbs were calculated to identify alterations in the weight distribution among the limbs.

Research Findings

• When pressure was applied to the horses’ hindlimbs, causing a subtle lameness (graded 2 on the AAEP scale), the researchers observed no major unloading of the affected limb within the group of horses. However, statistically significant changes to back kinematics were identified.
• The flexion-extension (FE) range of motion (ROM) of the vertebral column increased in most horses while walking, specifically within the thoracic segments. Concurrently, an increase was observed in the axial rotation (AR) ROM of the pelvis.
• During trotting, the FE ROM decreased, but only in the L3-L5-S3 segment. When the lame hindlimb was in the stance phase, the T6-T10-T13 segment demonstrated more flexion and the neck was lowered to accommodate the changes.
• Interestingly, the stride length or protraction-retraction angles in the horses’ limbs showed no significant modifications due to the induced lameness.

Research Conclusions

• The researchers concluded that even minor lameness in the hindlimb can trigger observable and significant changes in horses’ back movements. The study found that slight lameness resulted in an increased ROM and hyperextension of the thoracolumbar back, alongside a decrease in the ROM of the lumbosacral segment and the rotational changes of the pelvis.
• The study findings underscore the tight connection between limb function and thoracolumbar motion. Thus, chronic presence of even subtle lameness could potentially result in back dysfunction in horses, a significant implication for horse welfare and performance.