Barrie D. Grant

Measurement of vertical forces and temporal components of the strides of horses using instrumented shoes

Summary Instrumented shoes were used to measure the vertical forces exerted by horses moving at a variety of gaits. Two types of shoes were used; one contained a single transducer positioned over the center of the frog and the second contained transducers located at the toe and both sides of the heel. Horses were shod with these instrumented shoes and walked and trotted over a force plate. Forces were simultaneously recorded from the transducers in the shoes and from the force plate. Comparisons were made between the amount and duration of the forces exerted on the transducers and the vertical and horizontal forces recorded from the force plate. Forces recorded from the single transducer shoes showed strong correlations with the forces recorded from the force plate for horses moving at the walk; however, at the trot only moderate correlations occurred between these forces. At both the walk and trot, forces recorded from each side of the heel and the total forces occurring on all three transducers from the front hooves of horses shod with three transducer shoes showed strong correlations to the vertical forces recorded from the force plate. Vertical forces were also recorded from the instrumented shoes as horses walked, trotted and galloped on a track straightaway. Forces recorded from normal horses shod with single transducer shoes on all four feet were greater on the forelimbs than the rear limbs at the walk and trot. At the gallop, forces were highest on the lead front followed by the nonlead front, lead rear and nonlead rearlimb, respectively. Forces recorded from a three transducer shoe on the right front hoof of a horse walking, trotting and galloping in a right lead were highest on the medial side of the heel and occurred during the middle of the support period. Peak forces on the toe occurred at or near the time of heel lift. The results of these studies indicate that these instrumented shoes have advantages over the methods previously used to measure locomotor forces. These instrumented shoes can be used to simultaneously record the temporal components and the amount and distribution of vertical forces exerted during consecutive strides of horses moving at a variety of gaits.

Relationships between locomotor forces, hoof position and joint motion during the support phase of the stride of galloping horses

Three methods were used simultaneously to determine the relationships between the vertical forces exerted on the hooves and the positions of the limbs and hooves at the times of peak vertical forces from 2 horses galloping on a track straightaway. Vertical forces were recorded from an instrumented shoe, fetlock joint motion was measured with an electrogoniometer and the angles of the carpus, fetlock and hoof were determined from slow-motion films. At hoof contact, the mean angles of the carpus and fetlock were 181-182 degrees and 199-206 degrees, respectively. Peak vertical forces on the heel occurred at or near maximum extension of the carpal and fetlock joints. Peak forces on the toe occurred during flexion of the fetlock joint and at mean hoof angles of 28-31 degrees from the horizontal. The mean angles of the hoof from the horizontal at the time of heel contact were 6-7 degrees. Hoof lift occurred at mean carpal angles of 173-174 degrees and mean fetlock angles of 199-200 degrees.

Diagnostic ultrasound examination of the dorsal aspect of the equine metacarpophalangeal joint

Summary Diagnostic ultrasonography was used to demonstrate villonodular synovitis of the equine metacarpophalangeal joint. The presence of the soft tissue, intracapsular mass was confirmed with conventional radiography and positive contrast arthrography. The mass was surgically excised and submitted for histopathologic identification.

Cervical Vertebral Malformations

Cervical vertebral malformations are recognized clinically when they result in spinal cord compression causing neurologic deficits. Confirmation of diagnosis is based on radiographic and myelographic evidence of cord compression. Medical therapy is not usually successful. Several successful surgical treatments are described.

Quantitative evaluation of equine carpal lamenesses

Summary Electrogoniometry was used to evaluate carpal joint motion of seven horses with diagnosed carpal lamenesses. Data from at least six consecutive strides of each horse were collected and compared with data from six clinically normal horses. The evaluations included the shapes and patterns of the goniograms, the ranges and amplitudes of movement, the angular velocities, and the swing and support periods of the stride. The amplitudes of movement of the affected joint were less than normal, primarily due to decreased flexion. In addition, irregularities of movement occurred during the extension phase as the affected limbs advanced. Analysis of the swing and support periods of the stride and changes in the angular velocities during flexion and extension indicated that carpal lamenesses may affect either or both phases of the stride. Therefore, the lamenesses may be classified as a swinging leg, supporting leg or mixed lameness if only one limb is involved. Other parameters, such as stride length and arcs of flight of the limbs, must be determined in addition to the electrogoniometric data to definitively classify bilateral carpal lamenesses. The results of this study indicate that electrogoniometry can provide a more quantitative assessment of the severity of carpal lamenesses than is possible by clinical examination alone. Using electrogoniometry in conjunction with the clinical examination it may be possible to determine whether a lameness is due to pain, mechanical interference or both.

Electromyographic evaluation of horses with laryngeal hemiplegia

Summary Thirty-eight horses suspected of having laryngeal hemiplegia had electromyograms (EMGs) performed on the dorsal cricoarytenoid muscle (DCAM). Electromyographic abnormalities consisted of fibrillation potentials, positive sharp waves, bizarre high frequency discharges, and reduced insertional activity. Normal motor activity consisted of motor unit activity during inspiration, or less frequently motor unit activity during inspiration with subsequent tonic motor activity. In affected muscles, motor unit activity was often absent but when present there was activity consisting of motor units which did not correspond to a particular phase of respiration or it was consistent with normal motor unit activity.

Jugular venous prosthesis on the horse: A preliminary report

Summary Woven dacron vascular prostheses a were implanted in 6 horses to replace segments of external jugular veins. Anticoagulant therapy using sodium heparin and coumadin was done postoperatively. Clotting profiles and red blood cell counts were determined by measuring activated partial thromboplastin time (APTT), one stage prothrombin time (OSPT), and packed cell volume (PCV). The horses were observed postoperatively for 4 to 38 days. Real time ultrasonography was used to monitor patency of the prostheses. All grafts remained patent during the observation period, although 3 cases of septic thrombosis were seen at necropsy.

Stride rates of horses trotting and cantering on a treadmill

Summary Fifteen Thoroughbred racehorses were exercised at the walk, trot and canter three times a week for seven weeks on an inclined treadmill. Stride rates of each horse were measured at the trot and canter during each exercise period. At both gaits, stride rates were consistent between trials for each horse and a general linear relationship between stride frequencies at the trot and canter occurred. Stride rates outside of the 95% confidence level occurred in only 17 of the 522 trials and, of these, gait abnormalities could be identified in only five of these trials. Three horses exhibited signs of dorsal displacement of the soft palate during some of the trials. No effects of this condition on stride frequencies were observed. The consistency of the stride rates at the trot and canter suggests that individual horses have a preferred stride frequency at a given velocity and gait. Horses that have high ratios between stride frequencies at the trot and canter would tend to have longer stride lengths at the canter at a given speed. Since maximum velocity is directly related to the length of stride, horses with longer strides should have higher peak speeds than those horses with shorter strides. Many other factors must be considered in any predictions of performance potential.

The effects of a compressible plastic shoe - The Seattle shoe®- on the kinematics of the strides of galloping thoroughbred horses

Summary This study was undertaken to determine if the kinematic parameters of galloping horses were altered when these horses were shod with Seattle Shoes®. Analyses of films of six Thoroughbred horses galloping through a track straightaway, with and without Seattle Shoes®, were used to determine velocity, stride length, stride time, swing time and support time ofthelimbs, the percentages of the stride time spent in the swing and support phases, and the arcs of flight of the carpi and fetlocks of the forelimbs and the coronets of all four limbs. Descriptive statistics were calculated for each of these variables. Comparisons were made between those measured from ® horses shod with and without the Seattle Shoe,usingboththe paired-t test and analysis of covariance, which eliminated the influence of differing velocities. No significant differences occurred in the stride lengths or timing parameters when these horses were shod with Seattle Shoes®. The Seattle Shoe® had its most significant effect on the arcs of flight of the limbs. The compression of the Seattle Shoe® appears to store a portion of the potential energy normally stored in the suspensory appa- ratus and results in a decreased extension of the fetlock. This energy is then released, causing significant increases in the heights of the forelimb during retraction and protraction. Although kinematic adjustments are required by horses to maintain the level of performance, the Seattle Shoe® appears to have no detrimental effects on the performance of galloping horses and it may decrease strain on the suspensory apparatus.

ESOPHAGEAL OBSTRUCTION BY ANTIBIOTIC BOLUSES IN A THOROUGHBRED FILLY: A CASE REPORT

Summary A case of equine midcervical esophageal obstruction by medicinal boluses is described. A discussion of the physical and endoscopic examination is included. Attempts at medical and manipulative therapy including massage, intraesophageal probing and endoscopically assisted efforts to snare the obstruction were nonrewarding. A standing midcervical esophagotomy was performed to facilitate the removal of the entrapped boluses. A positive contrast esophagram obtained five days after surgery indicated an absence of leakage of contrast media from the lumen of the esophagus. The filly was returned to athletic competition at seven days following surgery. No evidence of dysphagia or esophageal obstruction was reported six months following surgery. In this particular case, a standing midcervical esophagotomy afforded a successful alternative when manipulative and medical therapy proved inadequate.