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To determine the effects of 3 α2-adrenergic receptor agonists (α2-ARAs), alone or in combination with butorphanol tartrate, on objective measurements of lameness in horses.


17 adult polo horses with naturally occurring forelimb or hind limb lameness (or both).


In a crossover design, each horse received each protocol (saline [0.09% NaCl] solution [2 mL, IV] or xylazine hydrochloride [0.33 mg/kg, IV], detomidine hydrochloride [0.007 mg/kg, IV], or romifidine hydrochloride [0.033 mg/kg, IV] alone or in combination with butorphanol [0.007 mg/kg, IV]) in random order, with a washout period (≥ 7 days) between protocols. Horses were assessed immediately prior to (baseline) and 10, 15, 20, 30, and 40 minutes after administration of each protocol for degree of sedation, mechanical nociceptive threshold (MNT), and objective lameness measurements.


Compared with baseline values, sedation scores and MNTs were significantly higher at all evaluated time points following administration of all sedation protocols except xylazine alone; following administration of xylazine alone, sedation scores and MNTs were significantly higher at ≤ 30 minutes and ≤ 20 minutes, respectively. Significant differences in objective forelimb lameness measurements were noted after administration of the 3 α2-ARA-butorphanol combinations. Most significant differences in objective measurements of hind limb lameness were detected after administration of detomidine or romifidine, alone or in combination with butorphanol.


In the study horses, xylazine alone had the least impact on objective lameness measurements. The administration of α2-ARAs, particularly detomidine or romifidine, alone or in combination with butorphanol, resulted in small but significant effects on objective lameness measurements.

Full access
in American Journal of Veterinary Research


OBJECTIVE To determine the ability of an accelerometer within a commercially available portable media device (PMD) to measure changes in postural stability of standing horses during various stance conditions and to compare these results with data obtained by use of a stationary force platform.

ANIMALS 7 clinically normal horses.

PROCEDURES A PMD was mounted on a surcingle; the surcingle was placed immediately caudal to the highest point of the shoulders (withers). Each horse was examined while standing on a stationary force platform system in a normal square stance, forelimb base-narrow stance, and normal square stance at 5 and 10 minutes after sedation induced by IV administration of xylazine hydrochloride. A minimum of 5 trials were conducted for each stance condition. Ranges of craniocaudal and mediolateral motion as well as SDs were collected for the PMD and force platform system. Analyses were performed with mixed-model ANOVAs, and correlation coefficients were calculated.

RESULTS Stance condition significantly altered craniocaudal accelerations measured by use of the PMD, all craniocaudal and mediolateral displacements of the center of pressure, and velocities measured by use of the stationary force platform. For both the PMD and force platform, SDs were significantly affected by stance condition in both craniocaudal and mediolateral directions. Correlation coefficients between the systems for all variables were low to moderate (r = 0.18 to 0.58).

CONCLUSIONS AND CLINICAL RELEVANCE Body-mounted PMDs should be investigated for use in assessment of postural stability in horses with neuromuscular abnormalities.

Full access
in American Journal of Veterinary Research


Objective—To evaluate the effect of underwater treadmill exercise on static postural sway in horses with experimentally induced carpal joint osteoarthritis under various stance conditions.

Animals—16 horses.

Procedures—On day 0, osteoarthritis was induced arthroscopically in 1 randomly selected middle carpal joint of each horse. Beginning on day 15, horses were assigned to either underwater or overground (without water) treadmill exercise at the same speed, frequency, and duration. Two serial force platforms were used to collect postural sway data from each horse on study days −7, 14, 42, and 70. Horses were made to stand stationary on the force platforms under 3 stance conditions: normal square stance, base-narrow placement of the thoracic limbs, and removal of visual cues (blindfolded) during a normal square stance. The mean of 3 consecutive, 10-second trials in each condition was calculated and used for analysis.

Results—Displacement of the center of pressure differed significantly depending on the stance condition. Among horses exercised on the underwater treadmill, postural stability in both the base-narrow and blindfolded stance conditions improved, compared with findings for horses exercised on the overground treadmill. Horses exercised on the overground treadmill were only successful at maintaining a stable center of pressure during the normal square stance position.

Conclusions and Clinical Relevance—Variations in stance position had profound effects on the mechanics of standing balance in horses with experimentally induced carpal joint osteoarthritis. Underwater treadmill exercise significantly improved the horses’ postural stability, which is fundamental in providing evidence-based support for equine aquatic exercise.

Full access
in American Journal of Veterinary Research


CASE DESCRIPTION A 12-year-old mixed-breed mare (horse 1) and 6-year-old Friesian gelding (horse 2) were examined for chronic lameness associated with the stifle joint.

CLINICAL FINDINGS Lameness examination revealed effusion of the right (horse 1) or left (horse 2) femoropatellar and medial femorotibial joints and grade 3/5 (horse 1) or 4/5 (horse 2) lameness. A diagnosis of cranial cruciate ligament (CCL) injury with associated mineralization and avulsion (horse 1) or mineralization alone (horse 2) was facilitated in both horses with a caudomedial-craniolateral oblique radiographic view obtained 45° medial to the caudocranial line, which highlighted the origin of the ligament on the caudoaxial aspect of the lateral femoral condyle within the intercondylar fossa. These lesions were subsequently confirmed via CT.

TREATMENT AND OUTCOME Arthroscopy of the medial and lateral femorotibial joints was performed for horse 1 and revealed the osseous fragment associated with the CCL, but the fragment could not be removed. Horse 2 was euthanized while anesthetized following CT owing to the poor prognosis.

CONCLUSIONS AND CLINICAL RELEVANCE Radiography is typically the first imaging modality attempted for horses with CCL injury, particularly outside the hospital setting. A 45° caudomedial-craniolateral oblique radiographic view may aid in diagnosis of CCL injury when avulsion or mineralization is present. Although this view is not commonly included in the typical radiographic series for imaging of the stifle joint in horses, it should be considered when CCL injury is suspected.

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in Journal of the American Veterinary Medical Association


OBJECTIVE To evaluate the effects of exercise in an underwater treadmill (UWT) on forelimb biomechanics and articular histologic outcomes in horses with experimentally induced osteoarthritis of the middle carpal joint.

ANIMALS 16 horses.

PROCEDURES An osteochondral fragment was induced arthroscopically (day 0) in 1 middle carpal joint of each horse. Beginning on day 15, horses were assigned to exercise in a UWT or in the UWT without water (simulating controlled hand walking) at the same speed, frequency, and duration. Thoracic and pelvic limb ground reaction forces, thoracic limb kinematics, and electromyographic results for select thoracic limb muscles acting on the carpi were collected on days -7 (baseline), 14, 42, and 70. Weekly evaluations included clinical assessments of lameness, response to carpal joint flexion, and goniometric measurements of thoracic limb articulations. At study conclusion, articular cartilage and synovial membrane from the middle carpal joints was histologically examined.

RESULTS Exercise in a UWT significantly reduced synovial membrane inflammation and resulted in significant clinical improvements with regard to symmetric thoracic limb loading, uniform activation patterns of select thoracic limb muscles, and return to baseline values for carpal joint flexion, compared with results for horses with simulated hand walking.

CONCLUSIONS AND CLINICAL RELEVANCE Overall improvements in thoracic limb function, joint range of motion, and synovial membrane integrity indicated that exercise in a UWT was a potentially viable therapeutic option for the management of carpal joint osteoarthritis in horses.

Full access
in American Journal of Veterinary Research