Adaptation strategies of horses with induced forelimb lameness walking on a treadmill.

BACKGROUND: There is a paucity of research describing the gait pattern of lame horses at the walk. OBJECTIVES: To describe the changes in motion pattern and vertical ground reaction forces (GRFz) in horses with induced forelimb lameness at the walk and compare those changes with the changes observed at the trot. STUDY DESIGN: Experimental study. METHODS: In 10 clinically sound Warmblood horses, moderate forelimb lameness was induced using a sole pressure model followed by trot and walk on a treadmill. Kinematic data were collected using 3D optical motion capture (OMC), and GRFz by an instrumented treadmill. Mixed models were used to compare sound baseline versus forelimb lameness (significance was set at P < .05). RESULTS: Lameness induction significantly reduced peak GRFz on the second force peak, and vertical impulse in the lame limb. Stride and stance duration in all limbs were reduced. Lameness significantly affected the vertical movement symmetry of the head and withers. Maximum limb retraction angle, fetlock extension and protraction speed were reduced in the lame limb. Body centre of mass (COM) translation was reduced in the side-to-side direction and increased in the vertical and fore-aft directions. Several compensatory kinetic and kinematic changes were observed in the nonlame limbs. The observed changes in both kinetics and kinematics were generally smaller at walk with fewer variables being affected, compared to the trot. MAIN LIMITATIONS: Only one degree and type of orthopaedic pain (sole pressure) was studied. CONCLUSIONS: Compensatory strategies of forelimb lameness at the walk include alteration of several kinetic and kinematic parameters and have some specific patterns and inter-individual differences that are not seen at the trot. However, much like at the trot, head movement and forelimb vertical force symmetry seem to be the most useful parameters to detect forelimb lameness at walk.

Passive Dynamics Explain Quadrupedal Walking, Trotting, and Tölting.

This paper presents a simplistic passive dynamic model that is able to create realistic quadrupedal walking, tölting, and trotting motions. The model is inspired by the bipedal spring loaded inverted pendulum (SLIP) model and consists of a distributed mass on four massless legs. Each of the legs is either in ground contact, retracted for swing, or is ready for touch down with a predefined angle of attack. Different gaits, that is, periodic motions differing in interlimb coordination patterns, are generated by choosing different initial model states. Contact patterns and ground reaction forces (GRFs) evolve solely from these initial conditions. By identifying appropriate system parameters in an optimization framework, the model is able to closely match experimentally recorded vertical GRFs of walking and trotting of Warmblood horses, and of tölting of Icelandic horses. In a detailed study, we investigated the sensitivity of the obtained solutions with respect to all states and parameters and quantified the improvement in fitting GRF by including an additional head and neck segment. Our work suggests that quadrupedal gaits are merely different dynamic modes of the same structural system and that we can interpret different gaits as different nonlinear elastic oscillations that propel an animal forward.

Comparison of limb loading and movement of Icelandic horses while tölting and trotting at equal speeds.

OBJECTIVE: To compare gait mechanics and limb loading in Icelandic horses tölting and trotting at equal speeds and estimate their impact on orthopedic health. ANIMALS: 12 orthopedically normal Icelandic horses. PROCEDURES Kinetic and kinematic gait variables were simultaneously recorded as each horse was ridden at a tölt and trot on an instrumented treadmill at 3.4 m/s and 3.9 m/s. Differences between gaits were tested via 1-factor repeated-measures ANOVA. RESULTS: Horses had a higher stride rate and lower stride impulses at a tölt than at a trot. For forelimbs at a tölt, shorter relative stance duration resulted in higher peak vertical force (Fz(peak)). Conversely, for hind limbs, longer relative stance duration resulted in lower Fz(peak). The higher head-neck position at a tölt versus trot caused no weight shift to the hind limbs, but a higher forehoof flight arc and lower proretraction movement were identified. Stance durations for forelimbs were briefer than for hind limbs at a tölt, and the inverse was observed at a trot. Minimal height of the horse's trunk at the point of Fz(peak) of the respective limb suggested a spring-like mechanism for all limbs at a tölt. Hind limb measurements revealed no evidence of increased collection. Stride-to-stride limb timing varied more at a tölt than at a trot. At a trot, horses had brief or no suspension phases and a slightly 4-beated footfall rhythm was common. Post hoc energetic estimations revealed that tölting at the measured speeds was less advantageous than trotting. CONCLUSIONS AND CLINICAL RELEVANCE: High forelimb action in Icelandic horses and higher head-neck position at a tölt were associated with more restricted limb proretraction, higher Fz(peak), and faster force onset than at a trot. The impact of these differences on orthopedic health needs to be investigated more in detail.

Effects of shoeing on intra- and inter-limb coordination and movement consistency in Icelandic horses at walk, tölt and trot.

To enhance expressiveness of forelimb movement and improve the four-beat rhythm of the tölt, Icelandic horses are commonly ridden with excessively high and long hooves. The aim of this study was to objectively assess the effect of shoeing on intra- and inter-limb coordination and limb movement consistency (inter-stride variability) at walk, tölt and trot. Thirteen sound and fit Icelandic horses accustomed to exercise with a rider on a treadmill were assessed with long and high hooves commonly used for competition (S(H)) and with the hooves trimmed according to the standards of normal shoeing (S(N)). Limb timing variables were extracted from the four vertical ground reaction force curves measured with an instrumented treadmill. Measurements were taken at walk and at two tölting and trotting speeds. High hooves with long toes reduced stride rate and increased breakover duration. At the tölt, the footfall rhythm showed less tendency to lateral couplets. Movement consistency of the walk remained unchanged, whereas, at the tölt, stride-to-stride variability of selected time parameters increased in SH and/or at the higher velocity. At the faster trotting speed, variability of hind limb duty factor decreased, whereas variability of contralateral step duration in the forelimb increased. High hooves with long toes improve the clearness of the four-beat footfall rhythm of the tölt, but disturb the movement consistency of the gait. The prolonged breakover duration observed in all gaits may have negative implications for the health of the palmar structures of the distal foot.

Effects of shoeing on limb movement and ground reaction forces in Icelandic horses at walk, tölt and trot.

Tölt is a symmetric four-beat gait with a speed range extending into that of trot and canter. Specific shoeing methods, such as unnaturally high and long hooves, are used to enforce individual gait predisposition. The aim of this study was to assess the consequences of this shoeing style on loading and movement of the limbs at walk, tölt and trot, and at different velocities. Simultaneous kinetic and kinematic gait analysis was carried out at walk (1.4m/s) and at two tölting and trotting speeds (3.3m/s and 3.9 m/s) on an instrumented treadmill. Thirteen sound Icelandic horses were first measured with high, long front hooves (SH) and, 1 week later, after trimming the hooves according to standard shoeing principles (SN). Comparing SH with SN, front hooves had 21 ± 5 mm longer dorsal hoof walls, and the shoeing material per hoof was 273 ± 50 g heavier. In all three gaits, gait quality, as it is currently judged, was improved with SH due to a lower stride rate, a longer stride length and a higher, but not wider, forelimb protraction arc, which were also positively associated with speed. Forelimb-hind limb balance remained unchanged, but limb impulses were higher. Apart from an increase of ≤ 2.2% in the forelimbs at the faster speed of both tölt and trot, SH had little influence on vertical peak forces.

Saddle pressure distributions of three saddles used for Icelandic horses and their effects on ground reaction forces, limb movements and rider positions at walk and tölt.

Icelandic horse riding practices aim to place the rider further caudally on the horse's back than in English riding, claiming that a weight shift toward the hindquarters improves the quality of the tölt (e.g. giving the shoulder more freedom to move). This study compared saddle pressure patterns and the effects on limb kinetics and kinematics of three saddles: an Icelandic saddle (S(Icel), lowest point of seat in the hind part of the saddle), a treeless saddle cushion (S(Cush)) and a dressage-style saddle (S(Dres)). Twelve Icelandic horses were ridden with S(Icel), S(Cush) and S(Dres) on an instrumented treadmill at walk and tölt. Saddle pressure, limb forces and kinematics were recorded simultaneously. With S(Cush), pressure was highest under the front part of the saddle, whereas the saddles with trees had more pressure under the hind area. The saddles had no influence on the motion patterns of the limbs. The slight weight shift to the rear with S(Cush) and S(Icel) may be explained by the more caudal position of the rider relative to the horse's back.

Short term analgesic effect of extracorporeal shock wave therapy in horses with proximal palmar metacarpal/plantar metatarsal pain.

Extracorporeal shock wave therapy (ESWT) is an accepted form of treatment for chronic cases of proximal suspensory desmitis (PSD). Subjective evaluation of horses shortly after being treated with ESWT has led clinicians to comment on an immediate reduction in lameness. This study aimed to evaluate the analgesic effect of ESWT on 16 horses with PSD or PSD-like pain in a fore- or hindlimb. To objectively assess lameness, gait analysis was performed on an instrumented treadmill before and 6, 24, 48 and 72h after ESWT of the origin of the suspensory ligament and the results compared to the effects of local anaesthesia. Stride frequency, stance duration, vertical impulse and peak vertical force were determined. Thermographic imaging and evaluation of skin sensitivity of the treated area were carried out before and after ESWT in the same interval as gait analysis. The results showed that there were no significant improvements in the investigated parameters at any time after ESWT; however, in horses with affected forelimbs the contralateral weightbearing asymmetry decreased significantly 72h after ESWT. Neither skin sensitivity nor thermographic imaging revealed changes that could be attributed to ESWT.

Evaluation of skin sensitivity after shock wave treatment in horses.

OBJECTIVE: To evaluate the effects of shock wave treatment on cutaneous nerve function, compared with the effects of local nerve block and sedation. ANIMALS: 18 clinically sound Swiss Warmbloods. PROCEDURE: Horses were randomly allocated to 3 groups and received different amounts and types of shock waves (extracorporeal shock wave treatment [ESWT] or radial pressure wave treatment [RPWT]). Horses were sedated with xylazine and levomethadone. Shock waves were applied to the lateral palmar digital nerve at the level of the proximal sesamoid bones on 1 forelimb. Skin sensitivity was evaluated by means of an electrical stimulus at the coronary band before and 5 minutes after sedation and at 4, 24, and 48 hours after application of ESWT or RPWT. On the contralateral forelimb, skin sensitivity was tested before and 10 minutes after an abaxial sesamoid nerve block. RESULTS: No significant changes in skin sensitivity were detected, regardless of the shock wave protocol applied. Mean reaction thresholds after sedation were more than twice the baseline thresholds. After the abaxial sesamoid block, no reaction was recorded in any of the horses. CONCLUSIONS AND CLINICAL RELEVANCE: Application of ESWT or RPWT to the palmar digital nerve had no effect on cutaneous sensation distal to the treated region for at least 2 days after application. The analgesic effect of sedation on reaction to electrical stimuli was distinct but varied among horses.