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
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)
Objective—To evaluate the effectiveness of a novel trimethoprim-sulfadiazine oral suspension for the treatment of naturally acquired Streptococcus equi subsp zooepidemicus infection in horses.
Design—Randomized, controlled field trial.
Animals—180 horses with S equi subsp zooepidemicus infection.
Procedures—Horses with lower respiratory tract infections caused by S equi subsp zooepidemicus were treated with a new formulation of combined trimethoprim-sulfadiazine oral suspension at a dosage of 24 mg/kg (10.9 mg/lb) twice daily for 10 days (treatment group) or with an equivalent volume of saline (0.9% NaCl) solution (placebo group). Response to treatment, including clinical signs and fecal consistency scores, was assessed twice daily. Any adverse effects were recorded. The primary outcome variable was clinical response; the secondary outcome variable was eradication of S equi subsp zooepidemicus on study day 17 as determined by bacteriologic culture of repeated transtracheal-wash specimens.
Results—Of the 119 horses allocated to the treatment group, 69 (58%) had a positive clinical response. A significantly smaller proportion of horses in the placebo group (9/61 [15%]) had a positive clinical response. By day 5, 25 of 61 (41%) placebo horses had been withdrawn from the study because of negative clinical response, compared with only 10 of 119 (8.4%) treated horses. By day 10, 28 of 61 (46%) placebo horses had been withdrawn because of negative clinical response, compared with only 13 of 119 (11%) treated horses. There were few adverse events associated with the trimethoprim-sulfadiazine suspension. There were no significant differences in fecal consistency scores between treatment and placebo groups.
Conclusions and Clinical Relevance—The new oral suspension administered at 24 mg/kg twice daily effectively treated the clinical signs of S equi subsp zooepidemicus lower respiratory infection in horses and eliminated the organism from the respiratory tract. Adverse effects were minimal.
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.
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;
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
Sample Population—25 pairs of adult equine cadaver
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
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
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)
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.
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.
Objective—To measure alterations in lameness severity that occur following use of extracorporeal shock wave therapy (ESWT) in horses with naturally occurring unilateral forelimb lameness.
Design—Nonrandomized clinical trial.
Animals—9 horses with unilateral forelimb lameness.
Procedures—Force platform gait analysis was performed prior to administration of any treatments (baseline) and after use of local anesthesia to eliminate the lameness. Extracorporeal shock wave therapy was then administered, and gait analysis was repeated 8 hours later and then daily for 7 days.
Results—Compared with the baseline value, peak vertical force was significantly increased 8 hours and 2 days after ESWT, and peak vertical force on day 2 was not significantly different from force measured after use of local anesthesia to eliminate the lameness. Similarly, vertical impulse was significantly increased, compared with the baseline value, 8 hours and 2 days after ESWT, but at all times, it was significantly lower than vertical impulse measured after use of local anesthesia.
Conclusions and Clinical Relevance—Results suggest that in horses with naturally occurring lameness, use of ESWT results in a period of acute improvement in lameness severity that typically persists for 2 days. Thus, in horses undergoing ESWT, exercise should be controlled for a minimum of 2 days after treatment to prevent further injury.
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)
Objective—To determine whether conditions representing
activities that are typical in the recreational
use of horses, including transport to and from show
grounds, stall confinement in unfamiliar surroundings,
and light exercise, are associated with increased incidence
of gastric ulcers in horses.
Design—Randomized controlled study.
Animals—20 client-owned horses.
Procedure—Horses had no gastric ulcers as determined
by endoscopic examination on study day –1.
Ten control horses were maintained on-site with no
changes in management variables. Ten horses were
transported via trailer for 4 hours on day 0 to another
site, placed in individual stalls, fed twice daily, and
exercised twice daily for 3 days. On day 4, they were
transported back to the original site via trailer for 4
hours. On day 5, endoscopic examinations were performed
on all horses to assess gastric mucosa status.
Results—Horses that were transported and housed
off-site had a significantly higher incidence of hyperkeratosis
and reddening of the gastric mucosa than
control horses. Two control horses and 7 transported
horses developed gastric ulcers by day 5. Ulcer
scores of transported horses increased significantly
from day –1, whereas ulcer scores in control horses
did not change significantly from day –1.
Conclusions and Clinical Relevance—Activities that
are typical in recreational use of horses were ulcerogenic,
and ulcers in the gastric squamous mucosa can
develop under these conditions within 5 days. ( J Am Vet
Med Assoc 2005;227:775–777)
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
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
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)