Biomechanical and wearability testing of novel legwear for variably limiting extension of the metacarpophalangeal joint of horses

Objective: To evaluate the ability of a MCPJ support boot (legwear) to redirect loading forces from the flexor apparatus to the dorsal aspect of the cannon and pastern regions during: a) walk, trot, and canter exercise; and b) stall confinement. Animals: Six healthy adult horses. Procedures: Legwear-derived force data, reflecting redirected flexor apparatus load, were telemetrically recorded under four conditions: inactive legwear (unlimited legwear extension) and mild (activemild [30°]; 30° legwear extension), moderate (activemoderate [20°]; 20° legwear extension), or maximal (activemax [10°]; 10° legwear extension) restriction of legwear extension. The association between legwear setting and: i) gait and ii) stall activity level, with the corresponding peak legwear loads and legwear torques, was assessed using mixed effects models. Limbs were examined visually and manually for adverse physical effects of the legwear following testing. Results: During treadmill exercise, activemoderate [20°] resulted in significantly (p=0.005) higher peak legwear torque and redirected flexor apparatus load than activemild [30°]. Increasing speed during ambulation yielded significantly higher legwear torque and redirected flexor apparatus (p<0.0001). During in-stall wear, activemax [10°] prompted significantly (p=0.016) higher legwear torque and peak load than activemoderate [20°]. Unrestrained stall activity resulted in significantly (p=0.004) higher legwear torque and peak load than restrained activity. Legwear application caused minimal adverse physical effect on the limbs. Conclusions and clinical relevance: Controlled return to activity is crucial for rehabilitating flexor apparatus injuries. Findings imply that the legwear may variably reduce flexor apparatus load, promoting an enhanced mechanical environment for healing.