H. H. C. M. Savelberg

Kinematics of treadmill versus overground locomotion in horses

A kinematic analysis was carried out to compare treadmill and overground locomotion in horses at the trot. Stride variables and limb and trunk movements of 10 Dutch Warmblood horses were measured using the CODA-3 gait analysis system. Overground recordings were made on a rubber ground surface and on an asphalt track. Treadmill recordings were taken after a controlled habituation programme and at the same velocities as measured overground. On asphalt, a shorthened stride duration and a decreased vertical displacement of the withers were found compared with those on rubber ground. On the treadmill, stance duration of the forelimbs was longer than for either overground condition. Correspondingly, the hind limbs were placed earlier than the forelimbs in making diagonal ground contact in overground locomotion, but this changed to preceding forelimbs on the treadmill. Both forelimbs and hind limbs were moved more caudally during the retraction phase on the treadmill, while no differences were found in the protraction angle. The vertical movement of the hooves as well as the withers was smaller on the treadmill than on rubber ground. Treadmill belt velocity decreased by 9% during the stance phase. This is supposed to be an important reason for the differences in biomechanics and kinematics between treadmill and overground locomotion, which must be kept in mind when data obtained during treadmill locomotion have to be extrapolated to overground conditions.

The effect of toe weights on linear and temporal stride characteristics of standardbred trotters.

Summary Toe weights are applied to influence the stride characteristics of trotters. The quantitative effect of 88-g toe weights on the stride characteristics of Standardbred trotters was evaluated in a kinematic study using a CODA-3 analysis system. Six trotters were studied at a speed of 11 m/s on a treadmill. Temporal gait variables, joint angles, and the trajectories of the forelimb hoof were calculated. The stride patterns of the individual trotters were assessed by a judge and compared to the CODA-output. Those trotters with poor flexion of the carpal joint during the swing phase or with insufficient knee action responded with better carpal flexion and more knee action when toe weights were attached. No effect of toe weights on the protraction of the forelimb could be demonstrated. Stride length, stride duration, and the relative duration of the stance and swing phase as a percentage of the stride did not respond to toe weights. It is concluded that toe weights can be useful in Standardbred trotters, but their effect depends on the individual gait pattern.

LOAD REDISTRIBUTION AFTER DESMOTOMY OF THE ACCESSORY LIGAMENT OF THE DEEP DIGITAL FLEXOR TENDON IN ADULT HORSES

Summary An analysis of joint moments was used to study the biomechanical implications, load redistribution and kinematic pattern following desmotomy of the accessory ligament of the deep digital flexor tendon (AL) in adult horses. Recordings of 6 sound horses were made before and 10 days after desmotomy of the AL of the right forelimb at the walk and the trot. Kinematic recordings of the right forelimb and the left distal forelimb were made using the CODA-3 system. Kinetic recordings of the ground reaction forces in both forelimbs were made using a Kistler force plate simultaneously with the kinematic recordings. Radiographic localisation of the CODA-3 markers in both distal limbs allowed an analysis of coffin and fetlock joint moments, moment arms and forces in the digital flexor tendons. No transfer of load from the operated to the contralateral limb was found. In the operated limb the total joint moment of the coffin joint decreased substantially due to a reduced moment arm of the vertical ground reaction force component during the entire stance phase, while the fetlock joint moment decreased only slightly. To compensate for the loss of AL function, the superficial digital flexor tendon (SDFT) took a higher load during midstance, while at the end of the stance phase, the deep digital flexor tendon (DDFT) carried a higher load with a marked load peak just before heel off. While the compensation was adequate during midstance (no changes in maximal hyperextension of the fetlock joint), a prolonged hyperextension of the fetlock joint together with a rapid flexion at the start of the swing phase indicated that the DDFT was unable to compensate completely for the loss of AL function. It was concluded that the changes in total joint moments and increases in loading of the SDFT and DDFT allow locomotion without serious overloading of the compensating tendons following AL desmotomy.

Bilateral lameness in horses a kinematic study

The kinematic pattern of mild bilateral lameness was studied by inducing a supporting limb lameness in both fore-limbs of 11 sound Dutch Warmblood horses. The kinematics of the horses were recorded while they trotted (3.5 m/s) on a treadmill. The locomotion analysis system CODA-3 was used to determine the temporal stride patterns, limb movements as well as head and trunk movement patterns. The transient lameness model, by which pressure-induced pain is evoked on the hoof sole, was used. Differences between left and right limbs as well as between the sound and the lame condition were tested using a paired t-test. Stride and stance duration did not change significantly (p < 0.05) during bilateral lameness compared to the pattern of sound horses. Diagonal advanced placement changed to an earlier placement of both forelimbs. Fetlock hyperextension decreased also in both forelimbs, while the pro- and retraction, hoof impact angle, maximal hoof height, and all hind limb variables remained unchanged. Vertical head and trunk movements tended to decrease, but these changes were not significant. It was concluded that fetlock hyperextension and diagonal advanced placement indicate locomotor disturbances, but that mild bilateral lameness may be difficult to distinguish from individual patterns in single assessments because of the lack of locomotor asymmetries. Evaluation of these variables at regular intervals may allow an early detection of bilateral lameness, which then could be confirmed by diagnostic local anaesthesia.