Objective—To compare gentamicin concentrations achieved in synovial fluid and joint tissues during IV administration and continuous intra-articular (IA) infusion of the tarsocrural joint in horses.
Animals—18 horses with clinically normal tarsocrural joints.
Procedure—Horses were assigned to 3 groups (6 horses/group) and administered gentamicin (6.6 mg/kg, IV, q 24 h for 4 days; group 1), a continuous IA infusion of gentamicin into the tarsocrural joint (50 mg/h for 73 hours; group 2), or both treatments (group 3). Serum, synovial fluid, and joint tissue samples were collected for measurement of gentamicin at various time points during and 73 hours after initiation of treatment. Gentamicin concentrations were compared by use of a Kruskal-Wallis ANOVA.
Results—At 73 hours, mean ± SE gentamicin concentrations in synovial fluid, synovial membrane, joint capsule, subchondral bone, and collateral ligament of group 1 horses were 11.5 ± 1.5 μg/mL, 21.1 ± 3.0 μg/g, 17.1 ± 1.4 μg/g, 9.8 ± 2.0 μg/g, and 5.9 ± 0.7 μg/g, respectively. Corresponding concentrations in group 2 horses were 458.7 ± 130.3 μg/mL, 496.8 ± 126.5 μg/g, 128.5 ± 74.2 μg/g, 99.4 ± 47.3 μg/g, and 13.5 ± 7.6 μg/g, respectively. Gentamicin concentrations in synovial fluid, synovial membrane, and joint capsule of group 1 horses were significantly lower than concentrations in those samples for horses in groups 2 and 3.
Conclusions and Clinical Relevance—Continuous IA infusion of gentamicin achieves higher drug concentrations in joint tissues of normal tarsocrural joints of horses, compared with concentrations after IV administration.
Objective—To develop a method for continuous infusion
of gentamicin into the tarsocrural joint of horses,
to determine pharmacokinetics of gentamicin in synovial
fluid of the tarsocrural joint during continuous
infusion, and to evaluate effects of continuous infusion
of gentamicin on characteristics of the synovial
Animals—12 healthy adult horses.
Procedure—An infusion catheter consisting of flow
control tubing connected to a balloon infuser was
used. Gentamicin solution (100 mg/ml) was infused in
the right tarsocrural joint and balanced electrolyte
solution was infused in the left tarsocrural joint for 5
days. Synovial fluid and serum gentamicin concentrations
were measured by use of a fluorescence polarization
Results—17 of the 24 (71%) infusion catheters initially
placed functioned without complications for the entire
5-day infusion period. Median gentamicin concentration
in synovial fluid from treated joints during the 5-day infusion
period ranged from 287.5 to 982 μg/ml. Median
serum gentamicin concentration during this period
ranged from 2.31 to 2.59 μg/ml. Mean (± SD) elimination
half-life and total clearance of gentamicin from the
synovial fluid were 6.25 ± 1.01 hours and
1.52 ± 0.96 ml/min, respectively.
Conclusions and Clinical Relevance—An infusion
catheter can be used for continuous infusion of gentamicin
into the tarsocrural joints of horses for up to 5
days. At a gentamicin dosage of 0.17 ± 0.02 mg/kg/h,
continuous intra-articular infusion results in synovial
fluid gentamicin concentrations greater than 100
times the minimal inhibitory concentration reported
for common equine pathogens. (Am J Vet Res 2000;61:407–412)
To compare heat generation and mechanical bone damage achieved with 2 tapered and 1 cylindrical transfixation pin taps in third metacarpal bones from equine cadavers.
18 pairs (36 specimens) of third metacarpal bones from euthanized horses with no known metacarpal disease.
In each bone, an investigator drilled 3 holes for placement of a 6.3-mm cylindrical transfixation pin, a 6.3-mm tapered pin using a prototype tapered tap, and a 6.3-mm tapered pin using a revised tapered tap. One bone of each pair was tapped by hand and the other with an electric drill. Temperatures of the drill bits, reamers, and taps were measured and used to compare heat generation among tap groups and tapping methods (hand vs power tapping). Macrodamage (all bone pairs) and microdamage (6 bone pairs) were assessed.
The revised tapered tap resulted in less heat generation and less total thread microdamage, compared with the prototype tapered and cylindrical taps. Power tapping created less bone damage but higher temperatures than did hand tapping for all bone groups.
CONCLUSIONS AND CLINICAL RELEVANCE
The revised tap design for tapered pin insertion was superior to the prototype tap design and yielded similar or less bone damage than achieved with cylindrical pin insertion in equine third metacarpal bone specimens. We recommend careful hand tapping for tapered pin insertion rather than power tapping, which generated greater heat. The revised tapered tap could be expected to perform better than a cylindrical pin tap in terms of thermal and mechanical microdamage and should be used for insertion of tapered transfixation pins.
Objective—To determine in vitro output temperature differences of 3 IV fluid warmers.
Design—Prospective, randomized study.
Sample—3 IV fluid warmers.
Procedures—Warming capabilities of a distance-dependent blood and fluid warmer marketed for human and veterinary use (product A) and a veterinary-specific distance-dependent fluid warmer (product B) were compared at 0, 4, 8, and 12 cm from the device to the test vein and at flow rates of 20, 60, 100, 140, 180, 220, 260, and 300 mL/h with room temperature (approx 22°C) fluids (phase 1). The superior warming device was compared against a distance-independent IV fluid warmer (product C) with room temperature fluids at the same flow rates (phase 2). The effect of prewarmed fluids (38°C) versus room temperature fluids was evaluated with the superior warming device from phase 2 (phase 3).
Results—In phase 1, product B produced significantly warmer fluids than product A for all flow rates and distances. Both distance-dependent devices produced warmer fluid at 0 cm, compared with 4, 8, and 12 cm. In phase 2, product B produced warmer fluid than product C at 60, 100, 140, and 180 mL/h. In phase 3, there was no significant benefit to use of prewarmed fluids versus room temperature fluids. Output temperatures ≥ 36.4°C were achieved for all rates ≥ 60 mL/h.
Conclusions and Clinical Relevance—Product B had superior warming capabilities. Placing the fluid warmer close to the patient is recommended. Use of prewarmed fluids had no benefit. Lower IV fluid flow rates resulted in lower output fluid temperatures.
Objective—To determine synovial fluid gentamicin concentrations and evaluate adverse effects on the synovial membrane and articular cartilage of tarsocrural joints after implantation of a gentamicin-impregnated collagen sponge.
Animals—6 healthy adult mares.
Procedures—A purified bovine type I collagen sponge impregnated with 130 mg of gentamicin was implanted in the plantarolateral pouch of 1 tarsocrural joint of each horse, with the contralateral joint used as a sham-operated control joint. Gentamicin concentrations in synovial fluid and serum were determined for 120 hours after implantation by use of a fluorescence polarization immunoassay. Synovial membrane and cartilage specimens were collected 120 hours after implantation and evaluated histologically.
Results—Median peak synovial fluid gentamicin concentration of 168.9 μg/mL (range, 115.6 to 332 μg/mL) was achieved 3 hours after implantation. Synovial fluid gentamicin concentrations were < 4 μg/mL by 48 hours. Major histologic differences were not observed in the synovial membrane between control joints and joints implanted with gentamicin-impregnated sponges. Safranin-O fast green stain was not reduced in cartilage specimens obtained from treated joints, compared with those from control joints.
Conclusions and Clinical Relevance—Implantation of a gentamicin-impregnated collagen sponge in the tarsocrural joint of horses resulted in rapid release of gentamicin, with peak concentrations > 20 times the minimum inhibitory concentration reported for common pathogens that infect horses. A rapid decrease in synovial fluid gentamicin concentrations was detected. The purified bovine type I collagen sponges did not elicit substantial inflammation in the synovial membrane or cause mechanical trauma to the articular cartilage.
Objective—To determine the extent to which a hydroxyapatite coating promotes pin stability in the third metacarpal bone during transfixation casting in horses.
Animals—14 adult horses.
Procedures—7 horses each were assigned to either an uncoated or hydroxyapatite-coated pin group. Three transcortical pins were placed in the third metacarpal bone of each horse and incorporated into a cast for 8 weeks. Insertion and extraction torque were measured, and torque reduction was calculated. Radiography was performed at 0, 4, and 8 weeks. Lameness evaluation was performed at 2, 4, 6, and 8 weeks. Bacteriologic culture of pins and pin holes was performed at pin removal.
Results—All horses used casts without major complication throughout the study. Insertion torque was higher in uncoated pins. There was no effect of group on extraction torque. Hydroxyapatite-coated pins had lower torque reduction. Five of 15 hydroxyapatite-coated pins maintained or increased stability, whereas all uncoated pins loosened. Pin hole radiolucency, lameness grades, and positive bacteriologic culture rates were not different between groups.
Conclusions and Clinical Relevance—Hydroxyapatite coating increased pin stability within the third metacarpal bone of horses during 8 weeks of transfixation casting but did not improve pin performance on clinical assessments. Clinical use of hydroxyapatite-coated transfixation pins may result in greater pin stability; however, further research is necessary to improve the consistency of pin osteointegration and elucidate whether clinical benefits will ultimately result from this approach in horses.
Objective—To determine the effects of a continuous
intra-articular infusion of gentamicin on the synovial
membrane and articular cartilage in the tarsocrural
joint of horses.
Animals—6 healthy adult horses.
Procedure—A balloon infusion system attached to a
catheter placed in the plantarolateral pouch of both
tarsocrural joints in each horse was used for continuous
gentamicin solution (GM) or balanced electrolyte
solution (BES) delivery for 5 days. Cartilage and synovial
membrane specimens were collected on day 5
from 3 horses and on day 14 from the remaining 3
horses. Both infused joints from each horse were
assessed, using gross evaluation and histologic scoring
Results—Significant differences in the histologic
scores of synovial membrane specimens between
the GM- and BES-treated joints at either 5 or 14 days
were not observed. Safranin-O-fast green staining
scores were similar between cartilage specimens
from GM- and BES-treated joints. Although the synovial
membrane histologic scores and safranin-O-fast
green staining scores improved from day 5 to 14, the
changes in scores were not significant. Loss of synovial
intimal cells from villi was found more commonly
in sections of synovial membrane from GM-treated
joints, compared with BES-treated joints.
Conclusions and Clinical Relevance—Continuous
infusion of GM into the tarsocrural joint of horses
does not have significant effects on histologic scores
of articular cartilage or synovial membrane, compared
with those infused with BES. Continuous infusion of
GM into the tarsocrural joint of horses for 5 days is an
acceptable method for the treatment of septic arthritis.
(Am J Vet Res 2002;63:683–687)
Objective—To determine clinical findings, complications, and outcome of septic synovitis in which continuous intrasynovial antimicrobial infusion (CIAI) was used for local antimicrobial delivery in horses.
Design—Retrospective case series.
Animals—22 adult horses and 9 foals (horses < 1 year of age).
Procedures—Records of horses with septic synovitis that had CIAI during treatment were reviewed. The association between clinical variables and whether horses performed their intended use following treatment was determined.
Results—42 synovial cavities were treated via CIAI. Twenty-nine cases were chronic (> 7 days) in nature, 15 had been refractory to standard treatments, and 13 synovial infections had associated osteomyelitis. Mean duration from infection to initiation of CIAI was 19.7 days, and mean duration of CIAI was 6.1 days. Temporary discharge from the catheter site at the time of removal was evident in 8 horses. Dysfunction of the infusion system occurred in 2 horses and was corrected during the course of treatment. No long-term complications were reported. Thirty-nine (93%) synovial infections in 29 (94%) horses were resolved. Twenty adult horses and 8 foals were discharged from the hospital, and 19 of 24 horses with long-term follow-up performed their intended use.
Conclusions and Clinical Relevance—CIAI was a useful adjunctive treatment for septic synovitis and allowed intrasynovial antimicrobial delivery into a variety of synovial cavities.
Objective—To determine whether heavy (≥ 680 kg [≥ 1,500 lb]) draft horses undergoing surgical treatment for acute signs of abdominal pain were at a greater risk for anesthetic and postoperative complications and lower postoperative survival rates than light (< 680 kg) draft horses.
Design—Retrospective case series.
Animals—72 draft horses.
Procedures—Medical records of draft horses that underwent exploratory celiotomy for signs of acute abdominal pain from October 1983 to December 2002 were reviewed. Medical records of draft horses in which a celiotomy was performed for correction of reproductive abnormalities were not included in the study.
Results—When compared with light draft horses, heavy draft horses had longer durations of anesthesia, more postoperative complications, and lower survival rates. Seventy-six percent of horses that recovered from anesthesia had postoperative complications. Postoperative complications associated with low survival rates included myopathy and neuropathy, ileus, diarrhea, and endotoxemia. All horses with postoperative myopathy and neuropathy died or were euthanized. The short-term survival rate for horses that recovered from anesthesia was 60%. Horses undergoing small intestinal surgery had a worse prognosis for short-term survival than those undergoing large intestinal surgery. The survival rate for horses for which long-term (> 1 year) follow-up information was available was 50%.
Conclusions and Clinical Relevance—Draft horses weighing > 680 kg that underwent surgery because of acute signs of abdominal pain had longer durations of anesthesia, more postoperative complications, and higher mortality rates than draft horses weighing < 680 kg.
Objective—To determine the effect of 2 hydroxyapatite pin coatings on heat generated at the bone-pin interface and torque required for insertion of transfixation pins into cadaveric equine third metacarpal bone.
Sample Population—Third metacarpal bone pairs from 27 cadavers of adult horses.
Procedures—Peak temperature of the bone at the cis-cortex and the hardware and pin at the trans-cortex was measured during insertion of a plasma-sprayed hydroxyapatite (PSHA)—coated, biomimetic hydroxyapatite (BMHA)—coated, or uncoated large animal transfixation pin. End-insertional torque was measured for each pin. The bone-pin interface was examined grossly and histologically for damage to the bone and coating.
Results—The BMHA-coated transfixation pins had similar insertion characteristics to uncoated pins. The PSHA-coated pins had greater mean peak bone temperature at the cis-cortex and greater peak temperature at the trans-cortex (70.9 ± 6.4°C) than the uncoated pins (38.7 ± 8.4°C). The PSHA-coated pins required more insertional torque (10,380 ± 5,387.8 Nmm) than the BMHA-coated pins (5,123.3 ± 2,296.9 Nmm). Four of the PSHA-coated pins became immovable after full insertion, and 1 gross fracture occurred during insertion of this type of pin.
Conclusions and Clinical Relevance—The PSHA coating was not feasible for use without modification of presently available pin hardware. The BMHA-coated pins performed similarly to uncoated pins. Further testing is required in an in vivo model to determine the extent of osteointegration associated with the BMHA-coated pins in equine bone.