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- Author or Editor: Scott McClure x
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Abstract
Objective
To measure and compare concentrations of selected blood lipids before and after thyroidectomy in horses.
Animals
5 healthy adult mares.
Procedure
Mares were confirmed to be euthyroid. Thyroidectomy was performed, and hypothyroidism was confirmed. Selected blood lipid variables were measured before hypothyroidism was induced and weekly for 4 weeks after induction. Plasma concentrations of very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), serum triglyceride (TG), total cholesterol (TC), and nonesterified fatty acid (NEFA) were measured. The composition of VLDL and LDL also was examined.
Results
Mean plasma concentrations of VLDL and LDL increased significantly after thyroidectomy. By 4 weeks after thyroidectomy, a ninefold increase in mean plasma concentration of VLDL and a threefold increase in LDL, compared with baseline values, were detected. After thyroidectomy, mean percentage of TG in VLDL increased significantly, whereas free cholesterol and cholesterol ester content decreased. Mean percentage of TG in LDL also increased by 3 to 4 weeks after thyroidectomy. Serum concentrations of TG and TC increased, whereas serum NEFA concentration decreased.
Conclusions
Hypothyroidism significantly alters blood lipid concentrations of horses. After thyroidectomy, markedly high VLDL concentration, appearance of TG-rich VLDL, increased serum concentrations of TG and TC, and decreased blood concentration of NEFA were evident.
Clinical Relevance
Examination of blood lipid concentrations of horses may be useful for detecting naturally acquired hypothyroidism. (Am J Vet Res 1999; 60:730-733)
Abstract
Objective—To measure changes in the modulus of elasticity (E) and describe histologic findings after extracorporeal shock wave therapy and radial pressure wave therapy on equine cortical bone specimens.
Sample Population—16 bone specimens from the proximodorsal cortex of an equine third metacarpal or metatarsal bone.
Procedure—Baseline E was determined by the density (ρ) and unidirectional ultrasound transmission velocity (C) of each specimen according to the equation E = ρC2. Eight specimens were treated with 500 pulses of 0.15 mJ/mm2 of extracorporeal shock wave therapy, and 8 specimens were treated with 500 pulses of 0.16 mJ/mm2 of radial pressure wave therapy. After treatment, C was determined again. Four treatment sessions resulted in 2,000 pulses and 5 C measurements. The ρ of each sample was measured again. Mean post-treatment E was calculated for each group. Nondecalcified sections of all specimens were stained with toluidine blue or basic fuchsin for histologic evaluation.
Results—Overall treatment group effect was not significant for C or E. Final E was not different from baseline values for extracorporeal shock wave therapy and radial pressure wave therapy. No histologic changes could be attributed to either treatment modality.
Conclusions and Clinical Relevance—Extracorporeal shock wave therapy and radial pressure wave therapy did not affect the material properties of equine bone at the energy and pulse values used in this study. (Am J Vet Res 2004;65:207–212)
Abstract
Objective—To evaluate the ability of industrial polystyrene foam insulation pads to redistribute loads placed on clinically normal weight-bearing structures of the foot and shift the location of the center of pressure palmarly in horses.
Animals—25 nonlame mature horses.
Procedures—Both forefeet from each horse were evaluated. Center of pressure data and solar load distribution patterns were recorded during a 5-second trial by use of a commercial pressure measurement system prior to placement of foam sole support and at 0, 6, 12, 24, and 48 hours after placement. Total contact surface area, contact pressure, peak contact pressure, and center of pressure positions were compared by use of a linear mixed model with repeated measurements.
Results—Total contact surface area was increased significantly at all time points, whereas contact pressure and peak contact pressure were significantly decreased at all time points following application of foam sole supports. Immediately following application of sole support, the position of the center of pressure was significantly moved cranially. However, by 48 hours, the center of pressure was significantly positioned more palmarly than prior to application of the foam supports.
Conclusions and Clinical Relevance—Results indicated that the use of foam sole supports may be an effective, economical, and immediate treatment for acute laminitis.
Abstract
Objective—To identify the duration and potential mechanisms of analgesia following extracorporeal shock wave therapy (ESWT) and radial pressure wave therapy (RPWT) in limbs of horses and sheep.
Animals—6 horses and 30 sheep.
Procedure—An electrical stimulus was used to identify the nociceptive threshold for each horse daily for 3 days before treatment (baseline) with ESWT or RPWT, 8 hours after treatment, and at 24-hour intervals for 7 days after treatment. Testing was conducted for the treatment field (midmetacarpus or midmetatarsus) and nerve field (medial and lateral forelimb heel bulbs) distal to a treatment site that included the nerve on the abaxial surface of the proximal sesamoid bone. All 4 limbs of 30 sheep were treated with ESWT, RPWT, or a sham treatment. Two sheep were euthanatized daily and tissue harvested for histologic evaluation of nerves, and concentrations of substance P and calcitonin gene-related peptide were measured in the skin and periosteum.
Results—Values did not differ significantly between baseline and after treatment for the treatment field or nerve field sensation. There was a large difference in the slope when data for horses were plotted for the first 3 days after treatment, compared with the slope for days 4 to 7 after treatment. No differences were found in neuropeptide concentrations after treatment of the sheep, but there was an inflammatory response in the treated nerves.
Conclusions and Clinical Relevance—A small cutaneous analgesic effect may exist at the treatment site for approximately 3 days after ESWT or RPWT in horses. (Am J Vet Res 2005;66:1702–1708)
Abstract
Objective—To determine the accuracy and precision of dual energy x-ray absorptiometry (DEXA) for measuring bone mineral density in horses in situ.
Sample Population—12 randomly selected forelimbs from 12 horses.
Procedure—Metacarpi were scanned in 2 planes and DEXA measurements obtained for 6 regions of interest (ROI). Each ROI was isolated and bone density measured by Archimedes' principle. Linear regression analysis was used to determine the correlation between the 2 measurements at each ROI. An additional metacarpus was measured 10 times to determine the coefficient of variation for both techniques.
Results—Dual energy x-ray absorptiometry and bone density were significantly associated at multiple ROI. The addition of age, weight, and soft tissue or bone thickness improved these associations. Repeated measurements had a low coefficient of variation.
Conclusions and Clinical Relevance—Dual energy x-ray absorptiometry can be used to accurately and precisely measure the bone density in the equine metacarpus. Dual energy x-ray absorptiometry appears suitable for serial in vivo measurement of bone density of the equine metacarpus. Dual energy x-ray absorptiometry may be used for studies to evaluate the effects of diet or drugs on bone density or density changes from bone remodeling that develop prior to stress fractures. ( Am J Vet Res 2001; 62:752–756)
Abstract
Objective—To evaluate the effect of focused extracorporeal shock wave therapy (ESWT) and radial pressure wave therapy (RPWT) on immunohistochemical staining for substance P and calcitonin gene-related peptide (CGRP) in the skin and periosteum of sheep.
Animals—36 sheep.
Procedures—All 4 limbs of 36 sheep were treated with ESWT, RPWT, or a sham treatment. For 14 days after treatment, at least 2 sheep were euthanized daily and tissue was harvested for histologic evaluation of nerves via staining for substance P and CGRP in the skin and periosteum.
Results—No effects of ESWT or RPWT were observed on the number of nerves with stain uptake for substance P or CGRP in the skin or periosteum.
Conclusions and Clinical Relevance—Substance P- and CGRP-containing nerve fibers are not disrupted by EWST or RPWT. Further studies are needed to identify the mechanism of analgesia observed in association with these treatment modalities.
Abstract
Objective—To evaluate in vitro holding power and associated microstructural and thermal damage from placement of positive-profile transfixation pins in the diaphysis and metaphysis of the equine third metacarpal bone.
Sample Population—Third metacarpal bones from 30 pairs of adult equine cadavers.
Procedure—Centrally threaded positive-profile transfixation pins were placed in the diaphysis of 1 metacarpal bone and the metaphysis of the opposite metacarpal bone of 15 pairs of bones. Tensile force at failure for axial extraction was measured with a materials testing system. An additional 15 pairs of metacarpal bones were tested similarly following cyclic loading. Microstructural damage was evaluated via scanning electron microscopy in another 6 pairs of metacarpal bones, 2 pairs in each of the following 3 groups: metacarpal bones with tapped holes and without transfixation pin placement, metacarpal bones following transfixation pin placement, and metacarpal bones following transfixation pin placement and cyclic loading. Temperature of the hardware was measured with a surface thermocouple in 12 additional metacarpal bones warmed to 38 C.
Results—The diaphysis provided significantly greater resistance to axial extraction than the metaphysis. There were no significant temperature differences between diaphyseal and metaphyseal placement. Microstructural damage was limited to occasional microfractures seen only in cortical bone of diaphyseal and metaphyseal locations. Microfractures originated during drilling and tapping but did not worsen following transfixation pin placement or cyclic loading.
Conclusions and Clinical Relevance—Centrally threaded, positive-profile transfixation pins have greater resistance to axial extraction in the diaphysis than in the metaphysis of equine third metacarpal bone in vitro. This information may be used to create more stable external skeletal fixation in horses with fractures. (Am J Vet Res 2000;61:1304–1308)
Summary
Breaking strength (torque at failure) of equine third metacarpal bones, with transfixation pins placed parallel in the frontal plane and 30° divergent from the frontal plane, was determined in vitro. Two transfixation pins were placed through the distal metaphysis, using a jig designed to drill the holes in the assigned configuration. Paired metacarpal bones II through IV from 12 horses were tested in torsion. The torsional moment of the force applied through the transfixation pins at failure was compared for each limb. Metacarpal bones with divergent pins were significantly (P = 0.030) stronger, compared with those with parallel pins. Metacarpal bones with parallel pins failed with longitudinal oblique fractures through a proximal bone-pin interface, whereas those with divergent pins failed with more comminuted fractures through multiple bone-pin interfaces.
Summary
Axial stability of equine oblique proximal phalangeal osteotomies with application of the standard short limb cast or 1 of 3 configurations of transfixation casts was determined in vitro. Transfixation cast methods included use of parallel pins, divergent pins, or parallel pins incorporating a metal walking bar. Displacement at the osteotomy was recorded for each limb at 4,448 N. Standard short limb casts provided significantly (P = 0.0002) less axial stability than did any form of transfixation cast. Significant differences were not found between the 3 transfixation casts.
Abstract
Objective—To compare the in vitro holding power and associated microstructural damage of 2 large-animal centrally threaded positive-profile transfixation pins in the diaphysis of the equine third metacarpal bone.
Sample Population—25 pairs of adult equine cadaver metacarpal bones.
Procedure—Centrally threaded positive-profile transfixation pins of 2 different designs (ie, self-drilling, self-tapping [SDST] vs nonself-drilling, nonself-tapping [NDNT] transfixation pins) were inserted into the middiaphysis of adult equine metacarpal bones. Temperature of the hardware was measured during each step of insertion with a surface thermocouple. Bone and cortical width, transfixation pin placement, and cortical damage were assessed radiographically. Resistance to axial extraction before and after cyclic loading was measured using a material testing system. Microstructural damage caused by transfixation pin insertion was evaluated by scanning electron microscopy.
Results—The temperature following pin insertion was significantly higher for SDST transfixation pins. Periosteal surface cortical fractures were found in 50% of the bones with SDST transfixation pins and in none with NDNT transfixation pins. The NDNT transfixation pins were significantly more resistant to axial extraction than SDST transfixation pins. Grossly and microscopically, NDNT transfixation pins created less damage to the bone and a more consistent thread pattern.
Conclusions and Clinical Relevance—In vitro analysis revealed that insertion of NDNT transfixation pins cause less macroscopic and microscopic damage to the bone than SDST transfixation pins. The NDNT transfixation pins have a greater pull out strength, reflecting better initial bone transfixation pin stability. (Am J Vet Res 2000;61:1298–1303)