Objective—To determine the anisotropic characteristics of the microarchitecture of the subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the metacarpal condyles in horses with different stages of SCB disease.
Sample Population—12 third metacarpal bone pairs from racing Thoroughbreds euthanized for diverse reasons.
Procedures—Both metacarpi were collected from horses with SCB changes that were mild (sclerosis and focal radiolucencies; n = 6) or severe (multifocal radiolucencies and articular surface defects; 6). Sample blocks of SCB plate and TBB were collected from the distopalmar aspect of both condyles and the sagittal ridge and examined via 3-D micro-computed tomography at 45-?m isotropic voxel resolution. For each sample, the angle between the principal orientation of trabeculae and the sagittal plane and the degree of anisotropy (DA) were calculated from mean intercept length measurements.
Results—Condylar samples had significantly lower angle (mean, 8.9°; range, 73° to 10.9°) than sagittal ridge samples (mean, 40.7°; range, 33.6° to 49.2°), TBB had significantly higher DA (mean ± SE, 1.75 ± 0.04) than SCB plate (1.29 ± 0.04), and mildly diseased TBB had higher DA (1.85 ± 0.06) than severely diseased TBB (1.65 ± 0.06).
Conclusions and Clinical Relevance—The highly ordered appearance of trabeculae within the condyles supports the concept that joint loading is primarily transmitted through the condyles and not the sagittal ridge. The sharp changes in the trajectories of the SCB trabeculae at the condylar grooves may be indicative of hypothetical tensile forces at this location contributing to the pathogenesis of condylar fractures. (Am J Vet Res 2010;71:1148—1153)
Objective—To determine the cardiovascular effects
of 60 minutes of abdominal insufflation with CO2 to
an intra-abdominal pressure of 15 mm Hg in standing
horses receiving a constant rate infusion of detomidine.
Procedure—Horses were randomly allocated into
treatment or control groups. A washout period of a
minimum of 7 days separated the 2 experimental
periods of the crossover study. Catheters were
placed into the right atrium, pulmonary artery, jugular
vein, and right transverse facial artery after lidocaine
infiltration. All horses were sedated with detomidine
(8.54 µg/kg/h, IV). Horses in the treatment
group received abdominal insufflation with CO2 via
a laparoscopic cannula to a final and constant intraabdominal
pressure of 15 mm Hg for 60 minutes.
Systemic arterial pressure, right atrial pressure,
heart rate, cardiac output, core body temperature,
and the pH and gas tensions of arterial and mixed
venous blood were obtained. Cardiac index and systemic
vascular resistance were calculated. Data
were collected in 3 stages: preinsufflation (–10 and
–5 minutes), insufflation (0, 15, 30, 45, and 60 minutes),
and postinsufflation (70 and 80 minutes). The
quality of sedation and level of analgesia were
Results—The PaO2 of horses in the treatment group
was significantly higher after 60 minutes of pneumoperitoneum
than in the control group. Core body
temperature decreased significantly from baseline in
Conclusions and Clinical Relevance—A 60-minute
period of abdominal insufflation to an intra-abdominal
pressure of 15 mm Hg did not induce significant cardiovascular
abnormalities in healthy horses. ( Am J Vet Res 2004;65:357–362)
Objective—To determine the effects of indwelling nasogastric intubation on the gastric emptying rate of liquid in horses.
Animals—6 healthy horses.
Procedures—Horses were assigned to treatment and control groups in a prospective randomized crossover study with a washout period of at least 4 weeks between trials. Acetaminophen (20 mg/kg) diluted in 1 L of distilled water was administered via nasogastric tube at time points of 0, 12, 30, 48, and 72 hours to evaluate the liquid-phase gastric emptying rate. In control horses, nasogastric tubes were removed after administration of acetaminophen. In horses receiving treatment, the tube was left indwelling and maintained for 72 hours. A 10-mL sample of blood was collected from a jugular vein immediately before and 20, 40, 60, 80, 100, 120, and 180 minutes after acetaminophen administration. Serum acetaminophen concentrations were measured by use of a colorimetric method.
Results—Peak serum acetaminophen concentration was significantly higher in the control group (38.11 μg/mL) than in the treatment group (29.09 μg/mL), and the time required to reach peak serum acetaminophen concentration was significantly shorter in the control group (22.79 minutes) than in the treatment group (35.95 minutes).
Conclusions and Clinical Relevance—Results indicated that indwelling nasogastric intubation has a delaying effect on the gastric emptying rate of liquids. Veterinarians should consider the potential for delayed gastric emptying when placing and maintaining an indwelling nasogastric tube for an extended period of time after surgery. Repeated nasogastric intubation may be better than maintenance of an indwelling tube in horses with ileus.
Objective—To quantify changes in hoof wall strain distribution associated with exercise and time in Standardbreds.
Animals—18 young adult Standardbreds.
Procedures—9 horses were exercised 4 d/wk for 30 to 45 minutes at a medium trot for 4 months; 9 nonexercised horses served as the control group. Rosette strain gauges were used to measure the principal surface strains at the toe, lateral quarter of the hoof wall (LQ), and medial quarter of the hoof wall (MQ) of the right forefoot at the beginning and end of the experiment. Midstance maximal (msϵ1) and minimal (msϵ2) principal and peak minimal principal (pkϵ2) surface strains were measured; SDs of each of those variables were also calculated. Results were compared through ANOVA of time and exercise effects between and within the groups.
Results—Both the exercised and nonexercised groups had changes in strain distribution in their hooves over time. The msϵ1 did not change significantly with exercise; however, it changed significantly in both groups at both hoof quarters over time. At the beginning of the study, mean msϵ2 and pkϵ2 values were significantly higher in the exercised group than in the control group at the MQ and LQ but not at the toe. At the end of the study, these values were significantly higher in the control group than in the exercised group at the toe but not at the MQ or LQ.
Conclusions and Clinical Relevance—Detected changes in hoof wall surface strain may indicate the ability of hoof capsule material to respond to exercise. A better understanding of hoof adaptation to applied forces may allow implementation of proper trimming and shoeing techniques to promote adaptation to exercise loads in horses.
Objective—To evaluate the performance of a chemiluminescent endotoxin activity assay in horses with colic and healthy horses.
Animals—20 horses with colic and systemic inflammatory response syndrome (SIRS group), 8 horses with colic with no SIRS (NSIRS group), and 20 healthy horses.
Procedures—Venous blood was collected into EDTA blood collection tubes after completion of a physical examination, and a chemiluminescent endotoxin activity assay was performed within 60 minutes of collection. Medical or surgical interventions and outcome were recorded for each horse.
Results—Mean ± SE endotoxin activity was 0.16 ± 0.05 for healthy horses, 0.18 ± 0.07 for the NSIRS group, and 0.53 ± 0.05 for the SIRS group and was significantly different among the groups. Mean endotoxin activity was significantly higher in the SIRS group than in the NSIRS group and the healthy group. No significant difference between the healthy and NSIRS groups was present. The higher the measured endotoxin activity, the more likely it was for horses to be euthanized.
Conclusions and Clinical Relevance—The chemiluminescent endotoxin assay was easy to use, required a short time to perform, could be completed at the patient's side, and with some modifications, may be a useful component in the clinical assessment and prognostication of horses with colic.
Objective—To evaluate the clinical effects and pharmacokinetics of vancomycin in plasma and synovial fluid after intraosseous regional limb perfusion (IORLP) in horses and to compare results with those obtained after IV regional limb perfusion (IVRLP).
Procedures—1 forelimb of each horse received vancomycin hydrochloride (300 mg in 60 mL of saline [0.9% NaCl] solution) via IORLP; the contralateral limb received 60 mL of saline solution (control). Solutions were injected into the medullary cavity of the distal portion of the third metacarpal bone. Synovial fluid from the metacarpophalangeal (MTCP) and distal interphalangeal (DIP) joints and blood were collected prior to perfusion and 15, 30, 45, 65, and 90 minutes after beginning IORLP, and synovial fluid from the MTCP joint only and blood were collected 4, 8, 12, and 24 hours after beginning IORLP. Plasma urea and creatinine concentrations and clinical appearance of the MTCP joint region and infusion sites were determined daily for 7 days. Results were compared with those of a separate IVRLP study.
Results—Clinical complications were not observed after IORLP. Mean vancomycin concentration in the MTCP joint was 4 μg/mL for 24 hours after IORLP. Compared with IORLP, higher vancomycin concentrations were detected in the DIP joint after IVRLP. Compared with IVRLP, higher vancomycin concentrations were detected in the MTCP joint for a longer duration after IORLP.
Conclusions and Clinical Relevance—IORLP with 300 mg of vancomycin in a 0.5% solution was safe and may be clinically useful in horses. Intravenous and intraosseous routes may be better indicated for infectious processes in the DIP and MTCP joints, respectively.
Objective—To evaluate clinical variables, regional
concentrations, and pharmacokinetics of vancomycin
in the synovial fluid of distal forelimb joints of horses
after IV regional limb perfusion.
Procedure—Vancomycin was administered via IV
regional limb perfusion to the distal portion of the
forelimbs of anesthetized horses. Drug (300 mg of
vancomycin hydrochloride in 60 mL of saline [0.9%
NaCl] solution) was infused into 1 forelimb, whereas
the contralateral limb served as a control and was perfused
with 60 mL of saline solution. Solutions were
injected into the lateral digital vein after digital exsanguination.
Synovial fluid from the metacarpophalangeal
(MTCP) and distal interphalangeal (DIP) joints
and systemic blood were collected prior to perfusion
and 15, 30, 45, 65, and 90 minutes after initiation of
the infusion. Synovial fluid from the MTCP joint and
blood were also obtained at 4, 8, 12, and 24 hours
after infusion. Plasma urea and creatinine concentrations,
degree of lameness, and certain clinical variables
involving the MTCP joint and infusion site were
assessed for 7 days. Results were compared
between the vancomycin treatment and control
Results—No complications or significant differences
in renal function, lameness, or clinical variables were
observed between groups. Vancomycin concentrations
exceeded 4 µg/mL in MTCP joints for approximately
20 hours. Higher concentrations were reached
in DIP joints than in MTCP joints.
Conclusions and Clinical Relevance—IV regional
limb perfusion with 300 mg of vancomycin as a 0.5%
solution was safe and may be useful in horses as
treatment for distal limb infections. (Am J Vet Res
Objective—To characterize the microstructure of subchondral bone (SCB) plate and trabecular bone (TBB) of the distopalmar aspect of the condyles of third metacarpal bones (MC3s) from Thoroughbred racehorses at 2 different stages of SCB disease via micro–computed tomography (CT).
Sample Population—12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.
Procedures—MC3s were collected from horses with mild (n = 6) or severe (6) SCB disease, as determined via micro-CT. Cubic (6 × 6 × 6-cm) specimens of SCB plate and TBB were cut from the palmar aspect of condyles and sagittal ridges and examined with 3-dimensional micro-CT. For each specimen, apparent bone mineral density (aBMD), true BMD (tBMD), bone volume fraction (BVF), trabecular thickness (TBT), trabecular separation (TBS), and connectivity (CN) were calculated.
Results—Condyles had higher aBMD, tBMD, BVF, and TBT and lower TBS than did the sagittal ridge. In bone specimens with mild SCB changes, SCB plate had higher aBMD, TBT, and CN and lower TBS than did TBB. In bone specimens with severe SCB disease, TBB had higher aBMD and TMD and lower TBS than it did in bone specimens with mild disease, and values were similar to those for SCB plate in bone specimens with severe disease.
Conclusions and Clinical Relevance—The microstructure of SCB of the distopalmar aspect of metacarpal condyles of horses varied according to the severity of changes identified via micro-CT. With mild SCB disease, sclerosis existed in the SCB plate of the condyles; with severe disease, sclerosis also invaded condylar TBB.
Objective—To characterize the mechanical properties of subchondral bone (SCB) of the distopalmar aspect of the condyles of the third metacarpal bone (MC3) and their correlations with structural aspects of MC3s in Thoroughbred racehorses.
Sample Population—12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.
Procedures—MC3s were collected from horses with mild (n = 6) and with severe (6) SCB changes, as determined by micro–computed tomography (CT). Specimens of SCB plate and trabecular bone were cut from the distopalmar aspect of condyles and sagittal ridge and examined with 3-dimensional micro-CT. Specimens were tested in compression, and elastic modulus, yield stress, yield strain, and toughness were calculated. Apparent and true bone mineral density, bone volume fraction, trabecular thickness, trabecular separation, and connectivity were also calculated. Differences in mechanical properties among various classifications of bone were evaluated. Correlations between structural and mechanical variables were also assessed.
Results—No differences were detected between left and right forelimbs. Specimens from condyles had higher values for elastic modulus, yield stress, and toughness than did specimens of sagittal ridge. In SCB with severe changes attributable to SCB disease, SCB plate was weaker and trabecular bone was stronger than in SCB with mild changes. Microstructural and mechanical properties were significantly correlated.
Conclusions and Clinical Relevance—A marked gradient in mechanical properties of SCB from horses, which could be involved in the pathogenesis of condylar fractures, was detected. Mechanical properties of SCB from the distal aspect of MC3s can be predicted to some extent via micro-CT.