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  • Author or Editor: Gordon J. Baker x
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Summary:

Retrospective radiographic and scintigraphic analyses were performed on 27 fractures of the distal phalanx in 25 horses. Location of 99mtechnetium methylene diphosphonate (99mTc-mdp) uptake was compared with fracture line location as seen on radiography. Intensity (intense, moderate, mild) and pattern (focal, diffuse) of 99mTc-mdp uptake was recorded and compared with duration of fracture. Nine horses were monitored during convalescence by obtaining additional scintigraphic views 3 to 68 months after injury.

Palmar scintigraphic views had evidence of focal areas of increased 99mTc-mdp uptake that corresponded to fracture line location as seen on radiography. Lateral scintigraphic views had evidence of diffuse increased uptake. There was a significant (P < 0.01) association between duration of fracture and intensity of uptake, with fractures < 3 months in duration more likely to have intense focal uptake. All fractures < 10 days in duration had intense focal uptake. As fracture age increased, 99mTc-mdp uptake became less intense and more diffuse. Three fractures not evident on radiography had evidence of 99mTc-mdp uptake on scintigraphy. Stall rest resulted in decreased 99mTc-mdp uptake in 6 of 9 horses, but increased uptake was still visible in all horses between 4 and 25 months after injury. The only scintigraphic view without evidence of increased uptake was that obtained from a horse reexamined 68 months after injury.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Suspensory ligaments (sl) from 32 Thoroughbreds and 32 Standardbreds were collected to evaluate the variation in muscle content with respect to age, breed, sex, limb, and use. Six transverse sections, each 3 to 5 mm thick, were obtained from each sl. Four sections were taken from the body of the sl and 1 from the midportion of each branch. Sections were stained with van Gieson picric acid-fuchsin solution, then photographed, and black-and-white slides were made from the processed negatives. The transverse-sectional area of the sl and tbe contained muscle were determined by use of a computer with a color monitor and a digitizing device with its associated software. The percentage of muscle was then calculated for each section, for the entire ligament, and for each horse. Results were analyzed by multiple-regression analysis and Duncan multiple-range test, using the General Linear Model of SAS. Standardbreds had 40% more muscle in their sl than did Thoroughbreds. There was no significant difference in the percentage of sl muscle among sex, age, use, individual limb, or forelimb vs hind limb. For Standardbred horses, females had significantly greater muscle area content than intact males. Also, hind limb muscle area content was significantly greater than forelimb muscle content. Thoroughbred horses between 2 and 10 years of age not in training had significantly more muscle content than horses of the same age not in training. The reasons for these differences remain unclear.

Free access
in American Journal of Veterinary Research

Summary

Liquid mercury strain gauges were implanted in the forelimb proximal sesamoidean ligaments (psl) of 8 adult horses. The gauges measured psl strain while horses were standing with or without external support. In 6 of the horses, the gauges also measured PSL strain in horses at a walk, with or without external support. Gauges were enclosed within sliding polypropylene tubes to prevent nonaxial deformation. Each gauge was placed in 1 arm of a low-resistance half-bridge circuit. To provide temperature compensation, a dummy gauge was placed in the adjacent arm of the bridge circuit and was implanted next to the active gauge in the surrounding fascial tissue.

External support included fiberglass cast support (cast), dorsal fetlock splint support (dfs), support wraps of 3 bandage materials (SW1, SW2, and SW3), and support wrap with caudal splint (SW4). The cast was applied, with the fetlock and foot in weightbearing position, from the proximal portion of the metacarpus distal to and including the foot. The dfs was applied by placing the cranial half of the fiberglass cast on the dorsal aspect of the instrumented limb. The SW1, SW2, and SW3 were applied in a figure-8 pattern around the fetlock, using 50% of the linear stretch capacity of the bandage material, with the horse standing squarely on all 4 limbs. The SW4 was applied identically to the other support wraps, with the exception of addition of a flexible caudal splint incorporated in the support wrap.

Mean maximal strain while standing (∈s) without external support for 8 horses was 6.0% (range, 3.8 to 7.5%). Mean maximal strain at a walk (∈s) without external support for 6 horses was 5.9% (range, 4.1 to 8.2%). Only cast and dfs significantly reduced ∈s. Cast support reduced ∈s to a mean ± SEM 1.4 ± 0.2%, 77% reduction in total strain (P <0.0001). Use of dfs reduced ∈s to a mean 4.2 ± 0.3%, 30% reduction in total strain (P < 0.0001). The SW1, SW2, and SW3 did not significantly reduce ∈s (power > 0.8, δ = 20%). Conclusions cannot be made for reduction of ∈s with SW4 (power < 0.8, δ = 20%) because of low sample size. Only cast and dfs significantly reduced ∈w. Cast support reduced ∈w to a mean 2.0 ± 0.3%, 67% reduction in total strain (P < 0.0001). The dfs reduced ∈w to a mean 4.4 ± 0.4%, 25% reduction in total strain (P < 0.008). The SW1, SW2, and SW3 did not significantly reduce ∈w (power > 0.8, ∂ = 20%). Conclusions cannot be made for reduction of ∈w with SW4 (power < 0.8, ∂ = 20%) because of low sample size.

Free access
in American Journal of Veterinary Research

Summary

The case records, radiographs, and nuclear bone scans of 58 horses with stress reactions or stress fractures of the proximal palmar aspect of the third metacarpal bone (MC3) were reviewed. There were 47 Standardbreds, 4 Quarter Horses, 3 Thoroughbreds, 2 Arabians, 1 Oldenburg, and 1 Pony of America. Fifty-six of the horses were racehorses or performance horses. The mean and median ages of affected horses were 4 and 3 years, respectively. Lameness ranged from mild to severe. Physical findings were usually subtle and included signs of pain on deep palpation of the proximal palmar aspect of MC3 and slight effusion of the middle carpal joint in some cases. Lameness was commonly improved by high palmar and palmar metacarpal nerve blocks or anesthesia of the middle carpal joint. Fifty-three horses had higher than normal radiopharmaceutical uptake in the proximal palmar aspect of MC3 in the left or right limb. The other 5 horses had higher than normal radiopharmaceutical uptake bilaterally. Fifty-six of the 63 limbs with abnormal bone scans also had abnormal radiographs. Treatment consisted of a variable period of rest (1 to 6 months). Healing was best assessed by follow-up bone scans. Of the 45 horses for which follow-up information was adequate, 29 (64%) returned to their previous level of performance.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy.

Plasma K concentration remained constant (3.49 ± 0.09 mM K/L of plasma; mean ± sem) throughout the study. Erythrocyte potassium concentration decreased from 93.10 ± 1.94 mM K/L of erythrocytes on day 0 to 88.63 ± 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P < 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 ± 2.96 μM K/g of muscle (wet weight) to 79.61 ± 2.09 μM K/g of muscle (decrease of 12.6%; P < 0.05) on day 4 and decreased further on day 7 to 73.62 ± 1.85 μM K/g of muscle (decrease of 19.2%; P < 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = −0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = −0.018). The water content of the middle gluteal muscle remained constant (73.23 ± 0.36%) throughout the study.

Erythrocyte membrane potential did not change (−99.26 ± 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from −105.84 ± 1.67 mV on day 0 to −100.93 ± 2.10 mV on day 7 (P < 0.05).

Free access
in American Journal of Veterinary Research

Abstract

Objectives—To study the functional and structural responses of the right dorsal colon (RDC) of ponies to phenylbutazone (PBZ) in vitro at a concentration that could be achieved in vivo.

Animals—8 adult ponies.

Procedure—Short circuit current and conductance were measured in mucosa from the RDC. Tissues incubated with and without HCO3 were exposed to PBZ, bumetanide, or indomethacin. Bidirectional Cl fluxes were determined. After a baseline flux period, prostaglandin E2 (PGE2) was added to the serosal surfaces and a second flux period followed. Light and transmission electron microscopy were performed.

Results—Baseline short circuit current was diminished significantly by PBZ and indomethacin, and increased significantly after addictions of PGE2. After PGE2 was added, Cl secretion increased significantly in tissues in HCO3--free solutions and solutions with anti-inflammatory drugs, compared with corresponding baseline measurements and with control tissues exposed to PGE2. Bumetanide did not affect baseline short circuit current and Cl fluxes. The predominant histologic change was apoptosis of surface epithelial cells treated with PBZ and to a lesser extent in those treated with indomethacin.

Conclusions and Clinical Relevance—Prostaglandin- induced Cl secretion appeared to involve a transporter that might also secrete HCO3 . Both PBZ and indomethacin altered ion transport in RDC and caused apoptosis; PBZ can damage mucosa through a mechanism that could be important in vivo. The clinically harmful effect of PBZ on equine RDC in vivo could be mediated through its effects on Cl and HCO3 secretion. (Am J Vet Res 2002;220:934–941)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To document age-related changes in the morphology of the endodontic system, reserve crown, and roots of equine mandibular cheek teeth.

Design

Equine mandibular cheek teeth from horses of various ages were compared, using radiography, x-ray computed tomography, and histologic examinations.

Sample Population

48 right hemi-mandibles from horses 2 to 9 years old.

Procedure

Hemi-mandibles were radiographed, imaged by computed tomographic reconstruction, and reformatted. Histologic examination was used to identify and correlate tissue types.

Results

Permanent mandibular cheek teeth of the horse, at the time of eruption, consisted of an exposed crown and a reserve crown with a widely dilated apex. The endodontic system consisted of 5 or 6 pulp horns that connected to an expansive pulp in the reserve crown, which was confluent with the primordial pulp bulb surrounding the tooth’s apex.

At the time of eruption, mandibular cheek teeth did not have a distinct pulp chamber, roots, or evidence of root formation. However, within 2 years after eruption, mesial and distal roots and a pulp chamber were present. A distinct pulp chamber, communicating with the pulp horns and both root pulp canals, was identifiable for 4 to 5 years from the time of root formation. The endodontic system of cheek teeth, 6 to 8 years after eruption, consisted of 2 unattached compartments, made up of a root canal, pulp chamber, and 2 or 3 pulp horns.

Clinical Relevance

The age-related morphologic changes in equine mandibular cheek teeth have important implications for application of endodontic therapy in horses. (Am J Vet Res 1996;57:31-38)

Free access
in American Journal of Veterinary Research

Summary

Sixteen helminth-free pony foals were inoculated with a mean (±sd) 2,000 (±545.5) infective Parascaris equorum eggs (day 0). Foals were allocated to replicates of 4, and treatments within each replicate were assigned at random. Treatment administered on postinoculation day (pid) 28 included no treatment (control), 0.2 mg of ivermectin/kg of body weight, 10 mg of oxibendazole/kg, or 6.6 mg of pyrantel base (pamoate)/kg. Paste formulations of the anthelmintics were administered orally. The foals were euthanatized 14 days after treatment (pid 42) and examined for P equorum larvae in the small intestine. The mean ± sd (and range) numbers of fourth-stage P equorum larvae recovered from nontreated foals and those treated with ivermectin, pyrantel, or oxibendazole were 1,603.8 ± 1,026.8 (305 to 2,480), 29.3 ± 55.8 (0 to 113), 413.0 ± 568.1 (0 to 1,204), or 889.5 ± 1,123.1 (1 to 2,345), respectively. Compared with the value for control (nontreated) foals, treatment with ivermectin, pyrantel, and oxibendazole was 98.2, 74.2, and 44.5% effective, respectively, when administered 28 days after experimentally induced infection with P equorum. Adverse reactions attributable to treatment were not observed.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Navicular bone intraosseous pressure, gross pathologic, histologic, and histochemical data were collected from 8 horses with navicular disease and 4 control horses. Simultaneous navicular bone intraosseous, medial palmar arterial, and saphenous venous pressures were measured for the left and right forelimbs of each horse under general anesthesia. Gross pathologic evaluation included grading of changes on the flexor surface of the navicular bone. Safranin-O-fast green-stained sections were used for histologic-histochemical grading of the hyaline articular and fibrocartilage surfaces of the navicular bones. Hematoxyhn and eosin-stained sections were used for morphologic evaluation of the marrow spaces of navicular bones. Mean navicular bone intraosseous pressure for horses with navicular disease was significantly (P< 0.001) higher than that for controls. Differences in medical palmar arterial or saphenous venous pressures were not significant between groups. The median flexor surface gross pathologic and histologic-histochemical fibrocartilage scores for horses with navicular disease were significantly (P< 0.001) more severe than those for control horses. The histologic-histochemical hyaline cartilage scores for control horses and those for horses with navicular disease were not significantly different. Fibrosis of the marrow spaces beneath the flexor cortex of horses with navicular disease was more pronounced than that of control horses.

Free access
in American Journal of Veterinary Research