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Abstract

Objective—To determine analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses.

Animals—6 horses.

Procedures—Ethyl alcohol was injected in the medial palmar digital nerve of 1 forelimb, and formaldehyde was injected in the contralateral nerve. The lateral palmar digital nerve in 1 forelimb was surgically exposed, but not injected, and the contralateral lateral palmar digital nerve was not treated. For each heel, severity of lameness in response to experimentally induced heel pain (lameness score and peak vertical force), thermal reaction time, and heel skin sensitivity scores were recorded. Heel pain was experimentally induced by advancing a threaded bolt through a custom-made horseshoe to apply pressure to the palmar horned aspect of the hoof. Horses were followed up for 112 days, when a subset of nerves was sampled for histologic analysis.

Results—Alcohol and formaldehyde significantly reduced all measures of heel pain, and analgesia was evident over the 112 days of the study. Pastern circumference was significantly greater for formaldehyde-treated than for alcohol-treated limbs. Histologic evaluation showed preservation of nerve fiber alignment with an intact epineurium, loss of axons, axon degeneration, fibrosis, and inflammation in alcohol-treated and formaldehyde-treated nerves.

Conclusions and Clinical Relevance—Results suggested that intraneural injection of either ethyl alcohol or formaldehyde in the palmar digital nerves of horses resulted in substantial, but partial, heel analgesia that persisted for at least 112 days. No advantage of formaldehyde over alcohol was found, and formaldehyde resulted in greater soft tissue inflammation.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effects of exercise on the distribution and pharmacokinetics of technetium Tc 99m medronate (99mTc-MDP) following intra-articular (IA) injection in horses.

Animals—5 horses.

Procedures—1 antebrachiocarpal joint (ACJ)/horse was assigned to the exercised group (n = 5), and the contralateral ACJ was evaluated in the nonexercised group (5) after a minimum washout period of 7 days. Following IA injection of 99mTc-MDP (148 MBq), blood and scintigraphic images of the carpus were obtained at 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 240, 360, 480, 600, 720, and 1,440 minutes. Plasma and scintigraphic radioactivity were determined over time, and pharmacokinetic parameters were generated via noncompartmental and compartmental analyses. Each horse was monitored via physical and lameness examination and ACJ synovial fluid analysis before injection and at days 1, 2, 3, and 7

Results—Lameness was not observed. Mean ± SD synovial fluid WBC count increased at day 1 (exercised, 721 ± 234 cells/μL; nonexercised, 948 ± 223 cells/μL), but returned to baseline at days 3 and 7 Mean time to maximum plasma radioactivity was earlier in the exercised group (16.00 ± 2.35 minutes) than the nonexercised group (43.75 ± 3.64 minutes). Linear regression of the scintigraphic radioactivity-time curves revealed a greater negative slope in the exercised group within the first 25 minutes. There was no difference in absorption or elimination rate constants in a 2-compartment model.

Conclusions and Clinical Relevance—IA injection of 99mTc-MDP was safe and effective for evaluating synovial solute distribution. Exercise significantly increased early transfer of 99mTc-MDP from the ACJ into plasma, although absorption and elimination rate constants were not affected. Exercise may affect synovial clearance and withdrawal times of medications administered IA.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate use of kinetic gait analysis for detection, quantification, and differentiation of hind limb lameness and spinal ataxia in horses.

Design—Prospective clinical study.

Animals—36 horses.

Procedures—Kinetic gait analysis with a force plate was performed for 12 clinically normal horses, 12 horses with hind limb lameness, and 12 horses with spinal ataxia. Kinetic variables were compared among groups, correlated to subjective grading, and used to build predictive models to assess the accuracy of discrimination.

Results—Subsets of kinetic variables were characteristically altered in ataxic and lame gaits. Ataxic horses had significantly increased lateral force peak and variation in vertical force peaks in both hind limbs. Lame horses had significantly decreased vertical force peak and increased variation in vertical force peaks only in the lame hind limb. These variables were used to differentiate between spinal ataxia and hind limb lameness with excellent accuracy. There were significant correlations between a subset of kinetic variables and subjective lameness and neurologic grades.

Conclusions and Clinical Relevance—Kinetic gait variables, specifically lateral force peak and the variation in vertical force, can be used to support the differential diagnosis between spinal ataxia and hind limb lameness in horses. Kinetic gait analysis may also be applied for quantification of equine hind limb gait abnormalities as well as confirming lack of lameness and ataxia in soundness examinations.

Full access
in Journal of the American Veterinary Medical Association

SUMMARY

Objectives

To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1β (IL-1β) in isolated innervated or denervated equine metacarpophalangeal joints.

Animals

One metacarpophalangeal joint of 24 adult horses.

Procedures

The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1β. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1β, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation.

Results

IL-1β induced significant neutrophilic leukocytosis in synovial fluid and synovial membrane. IL-1β concentration had returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints.

Conclusion

Cellular response to IL-1β was rapid and sustained; joint clearance of IL-1β was rapid, and endogenous production of IL-1β did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage to IL-1β was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response. (Am J Vet Res 1998;59:88–100)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare the biochemical, histochemical, and immunohistochemical profiles of articular cartilage from horses with naturally acquired distal tibial osteochondrosis (OC) with cartilage from a similar location in clinically normal horses.

Animals

9 affected horses (group 1, 16 OC lesions) and 4 control horses (group 2, 8 normal osteochondral specimens).

Procedure

OC specimens were collected during arthroscopic removal of the fragment, and control specimens were collected by aseptic osteotomy. Uronic acid, total protein, total glycosaminoglycan (GAG), chondroitin sulfate (CS), and keratan sulfate (KS) contents were determined. Histomorphologic, histochemical, and immunohistochemical examinations were performed on specimens after snap freezing at −80 C and cryosectioning. Monoclonal antibodies (MAB) 3B3 and 5D4 were applied for location of epitopes of CS and KS, respectively.

Results

OC lesions had significantly lower quantity of uronic acid, total GAG, and CS, compared with normal cartilage. OC cartilage had significantly less intense staining with toluidine blue, along with irregular cellularity and tidemark characteristics, compared with normal cartilage. Monoclonal antibodies 3B3 and 5D4 stained OC cartilage, whereas MAB 5D4 did not stain control cartilage. Additionally, MAB 3B3 and 5D4 stained the fibrous tissue that was found firmly attached to the OC lesion located between the parent distal portion of the tibia and OC fragment.

Conclusion

OC cartilage lesions of the distal intermediate ridge of the tibia in horses are biochemically, histochemically, and immunohistochemically distinct from normal cartilage from the same location. Results may reflect the inability of the chondrocyte of the developing joint to alter matrix components that would allow proper maturation and differentiation into bone. (Am J Vet Res 1997;58:89–98)

Free access
in American Journal of Veterinary Research

Summary

The effects of intra-articular administration of methylprednisolone acetate (mpa) on the healing of full-thickness osteochondral defects and on normal cartilage were evaluated in 8 horses. In group-1 horses (n = 4), a 1-cm-diameter, full-thickness defect was created bilaterally in the articular cartilage on the dorsal distal surface of the radial carpal bone. Cartilage defects were not created in group-2 horses (n = 4). One middle carpal joint was randomly selected in each horse (groups 1 and 2), and treated with an intra-articular injection of 100 mg of mpa, once a week for 4 treatments. Injections began 1 week after surgery in group-1 horses. The contralateral middle carpal joint received intra-articular injections of an equivalent volume of 0.9% sodium chloride solution (scs), and served as a control. Horses were evaluated for 16 weeks, then were euthanatized, and the middle carpal joints were examined and photographed. Synovial and articular cartilage specimens were obtained for histologic and histochemical evaluation.

Gross morphometric evaluation of the healing defects in group-1 horses revealed that 48.6% of the defect in control joints and 0% of the defect in mpa-treated joints was resurfaced with a smooth, white tissue, histologically confirmed as fibrocartilage. This replacement tissue was a firmly attached fibrocartilage in control joints and a thin fibrous tissue in mpa-treated joints. The articular cartilage in joints treated with mpa had morphologic changes, including chondrocyte cluster formation, loss of palisading architecture, and cellular necrosis in both groups of horses. Histochemical (safranin-0) staining intensity was reduced significantly (P < 0.05) in all layers of articular cartilage in mpa-treated joints in groups 1 and 2. In the replacement tissue, intense safranin-0 staining was found only in the chondrocyte clusters deep in the tissue of control joints, confirming fibrocartilage repair. Intra-articular administration of mpa in this dosing regimen thus induced degenerative changes in normal articular cartilage and resulted in histomorphologic changes in the repair of full-thickness articular osteochondral defects in horses.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether enrofloxacin has detrimental, dose-dependent effects on equine articular cartilage in vitro.

Animals

Cartilage explants were developed from 6 healthy horses between 0 and 96 months old.

Procedure

Patellar cartilage explants were incubated in 5 concentrations of enrofloxacin (2 μg/ml, 10 μg/ml, 1,000 μg/ml, 10,000 μg/ml, and 50,000 μg/ml) for 72 hours. Proteoglycan synthesis (Na35SO4 incorporation for 24 hours), proteoglycan degradation (Na35SO4 release for 72 hours), endogenous proteoglycan content (dimethylmethlene blue assay), and total protein content were determined. Cartilage explants were evaluated by use of histomorphologic and histomorphometric techniques (toluidine blue stain) for cytologic and matrix characteristics. Quantitative data were analyzed with a one-way ANOVA to compare results among various enrofloxacin concentration groups and the control group. A general linear model was used to determine whether age had an effect.

Result

Proteoglycan synthesis was excellent in control specimens and in specimens incubated in low concentrations of enrofloxacin (2 μg/ml and 10 μg/ml). High concentrations of enrofloxacin (> 1,000 μg/ml) effectively eliminated proteoglycan synthesis regardless of horse age. Proteoglycan degradation at low concentrations (2 μg/ml and 10 μg/ml) was not different than control. High concentrations of enrofloxacin (> 1,000 μg/ml) caused significant degradation. Different concentrations of enrofloxacin did not affect endogenous proteoglycan. High concentrations of enrofloxacin were associated with a significant increase in number of pyknotic nuclei.

Conclusion

Concentrations of enrofloxacin that might be achieved following systemic administration did not suppress chondrocyte metabolism in vitro. High concentrations of enrofloxacin (> 1,000 μg/ml) were toxic to chondrocytes. (Am J Vet Res 1999;60:577–582)

Free access
in American Journal of Veterinary Research

Objective

To determine whether fracture fragment dimensions, suspensory ligament damage, and racing status at the time of injury were associated with outcome in Standardbred horses with apical fracture of the proximal sesamoid bone.

Design

Retrospective study.

Animals

43 Standardbred racehorses.

Procedure

Medical records, racing records, and radiographs were reviewed, and ultrasonographic findings were scored. Measurements of the fractured portion of the proximal sesamoid bone were made.

Results

Seventy-four percent (32/43) of horses were pacers, and 26% (11/43) were trotters. Statistical differences between trotters and pacers regarding ability to start, number of starts, or amount of money earned after injury were not detected. Females earned significantly more money per start after injury than males. Eighty-six percent (37/43) of fractures involved hind limbs and 14% (6/43) involved forelimbs. Horses with forelimb injuries earned less money per start. Severity of suspensory ligament damage did not affect postinjury racing performance. A higher proportion of horses that had raced before injury returned to racing after surgery than horses that had not raced before injury, although a significant difference between these groups was not detected. Eighty-eight percent of horses that raced before injury raced after injury. Fifty-six percent of horses that did not race before injury raced after injury. Fracture fragment dimensions did not affect outcome.

Clinical Implications

Dimensions of the apical fracture fragment of the proximal sesamoid bone in Standardbred horses and degree of suspensory ligament damage did not affect outcome. Prognosis for return to racing soundness is good in horses that had raced before injury and fair in horses that had not raced before injury. (J Am Vet Med Assoc 1999;214:1653-1656)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate intra-articular autologous protein solution (APS) for the treatment of osteoarthritis in horses.

Animals—40 client-owned horses with naturally occuring osteoarthritis.

Procedures—APS was generated from a dual-device system that concentrated plasma and WBC proteins and enriched platelet growth factors. Horses were randomly assigned to receive an intra-articular injection of 5 mL of saline (0.9% NaCl) solution (n = 20) or APS (20), exercised on a treadmill, and evaluated on the basis of lameness grades, kinetic gait analysis, joint circumference, and range of motion for 14 days. Horses that received saline solution were administered APS at termination of the study, and clients scored horses for lameness and discomfort before, 12 weeks after, and 52 weeks after the APS injection.

Results—The APS group had significant improvements in lameness grade, asymmetry indices of vertical peak force, and range of joint motion by 14 days, compared with baseline or control group values. No adverse effects associated with APS treatment were evident. Clients assessed lameness and comfort as improved at 12 and 52 weeks. The APS had greater likelihood (OR, 4.3 to 30.0) of a therapeutic response in horses with a lameness score < 4, < 10% vertical force asymmetry, or absence of marked osteophyte formation, subchondral sclerosis, or joint space narrowing. Concentration of interleukin-1 receptor antagonist in APS was 5.8 times that in blood.

Conclusions and Clinical Relevance—Intra-articular administration of APS can be considered an effective treatment option for equine osteoarthritis, with the potential for disease-modifying effects.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate lameness and morphological changes associated with an osteochondral fragment–groove procedure as a means of experimental induction of metacarpophalangeal (MCP) joint osteoarthritis within an 11-week period in horses.

ANIMALS 6 nonlame adult warmbloods.

PROCEDURES The right MCP joint of each horse underwent an osteochondral fragment–groove procedure (day 0). After 1 week of stall rest (ie, starting day 7), each horse was trained daily on a treadmill. Weekly, horses underwent visual and inertial sensor-based assessments of lameness. Both MCP joints were assessed radiographically on days 0 (before surgery), 1, 35, and 77. A synovial fluid sample was collected from the right MCP joint on days 0 (before surgery), 35, 36, 49, 63, and 77 for cytologic and biomarker analyses. On day 77, each horse was euthanized; both MCP joints were evaluated macroscopically and histologically.

RESULTS Right forelimb lameness was detected visually and by the inertial sensor system when horses were moving on a straight line after distal forelimb flexion or circling left on days 14 to 77. Compared with presurgical values, synovial fluid interleukin-6, prostaglandin E2, hyaluronic acid, and interleukin-1 receptor antagonist protein concentrations were increased at 2 or 3 time points, whereas tumor necrosis factor-α and interleukin-10 concentrations were decreased at 1 time point. Gross examination of all right MCP joints revealed synovitis and wear lines; synovitis was confirmed histologically.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that a combined osteochondral fragment–groove procedure can be used to induce clinically and grossly observable early MCP joint osteoarthritis during an 11-week period in horses.

Full access
in American Journal of Veterinary Research