Antonio M. Cruz

Determination of the prevalence and severity of metacarpophalangeal joint osteoarthritis in Thoroughbred racehorses via quantitative macroscopic evaluation

OBJECTIVEnTo determine the prevalence and severity of osteoarthritis in the metacarpophalangeal joints of Thoroughbred racehorses via development and validation of a quantitative macroscopic evaluation system.nnnSAMPLE POPULATIONnMetacarpophalangeal joints from 50 Thoroughbred racehorses.nnnPROCEDURESnJoints were collected from horses that died or were euthanized within 60 days of racing. Metacarpophalangeal joints were assessed for osteoarthritic degeneration by use of macroscopic and histologic scoring systems, polarized light microscopy, and cartilage biochemical analysis. The global macroscopic score for the entire metacarpophalangeal joint was based on factors that reflected the size and severity of lesions as well as the involvement of weight-bearing surfaces.nnnRESULTSnOne-third of all 2- and 3-year-old horses had partial-or full-thickness cartilage lesions and osteoarthritis. Osteoarthritis severity increased until age 6 in this population. Significant correlations were found between macroscopic grade and age, cause of death, glycosaminoglycan depletion, and loss of superficial cartilage zone polarized light intensity.nnnCONCLUSIONS AND CLINICAL RELEVANCEnThe macroscopic system devised for this study had good correlations with quantitative methods. Two-and 3-year-old horses had full-thickness cartilage lesions that may have been career limiting. Year-to-year attrition and a small population of older horses may have led to underestimation of the prevalence of osteoarthritis in older horses. The macroscopic scoring system was reliable when used by nonexpert and expert users.

Evaluation of a laparoscopic technique for collection of serial full-thickness small intestinal biopsy specimens in standing sedated horses

OBJECTIVEnTo assess a technique for laparoscopic collection of serial full-thickness small intestinal biopsy specimens in horses.nnnANIMALSn13 healthy adult horses.nnnPROCEDURESnIn the ex vivo portion of the study, sections of duodenum and jejunum obtained from 6 horses immediately after euthanasia were divided into 3 segments. Each segment was randomly assigned to the control group, the double-layer hand-sewn closure group, or the endoscopic linear stapler (ELS) group. Bursting strength and bursting wall tension were measured and compared among groups; luminal diameter reduction at the biopsy site was compared between the biopsy groups. In the in vivo portion of the study, serial full-thickness small intestinal biopsy specimens were laparoscopically collected with an ELS from the descending duodenum and distal portion of the jejunum at monthly intervals in 7 sedated, standing horses. Biopsy specimens were evaluated for suitability for histologic examination.nnnRESULTSnMean bursting strength and bursting wall tension were significantly lower in the ELS group than in the hand-sewn and control groups in both the duodenal and jejunal segments. Use of the hand-sewn closure technique at the biopsy site reduced luminal diameter significantly more than use of the stapling technique. In the in vivo part of the study, all 52 biopsy specimens collected during 26 laparoscopic procedures were suitable for histologic examination and no clinically important perioperative complications developed.nnnCONCLUSIONS AND CLINICAL RELEVANCEnLaparoscopic collection of serial full-thickness small intestinal biopsy specimens with a 45-mm ELS may be an effective and safe technique for use in healthy adult experimental horses.

Multiple Pathways to Osteoarthritis and Articular Fractures: Is Subchondral Bone the Culprit?

Osteoarthritis and articular fractures are commonly responsible for early retirement from athletic performance. The subchondral bone (SCB) in those conditions is being recognized as an integral component in their pathophysiology. Early recognition of these potentially career-ending diseases may require understanding of the progression of changes occurring in SCB with time and exercise.

Mechanical properties of subchondral bone in the distal aspect of third metacarpal bones from Thoroughbred racehorses

OBJECTIVEnTo 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.nnnSAMPLE POPULATIONn12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.nnnPROCEDURESnMC3s 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.nnnRESULTSnNo 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.nnnCONCLUSIONS AND CLINICAL RELEVANCEnA 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.

Structural characterization of subchondral bone in the distal aspect of third metacarpal bones from Thoroughbred racehorses via micro–computed tomography

OBJECTIVEnTo 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).nnnSAMPLE POPULATIONn12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons.nnnPROCEDURESnMC3s were collected from horses with mild (n = 6) or severe (6) SCB disease, as determined via micro-CT. Cubic (6 x 6 x 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.nnnRESULTSnCondyles 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.nnnCONCLUSIONS AND CLINICAL RELEVANCEnThe 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.

Evaluation of endotoxin activity in blood measured via neutrophil chemiluminescence in healthy horses and horses with colic

OBJECTIVEnTo evaluate the performance of a chemiluminescent endotoxin activity assay in horses with colic and healthy horses.nnnANIMALSn20 horses with colic and systemic inflammatory response syndrome (SIRS group), 8 horses with colic with no SIRS (NSIRS group), and 20 healthy horses.nnnPROCEDURESnVenous 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.nnnRESULTSnMean + or - SE endotoxin activity was 0.16 + or - 0.05 for healthy horses, 0.18 + or - 0.07 for the NSIRS group, and 0.53 + or - 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.nnnCONCLUSIONS AND CLINICAL RELEVANCEnThe chemiluminescent endotoxin assay was easy to use, required a short time to perform, could be completed at the patients side, and with some modifications, may be a useful component in the clinical assessment and prognostication of horses with colic.

Analysis of the subchondral microarchitecture of the distopalmar aspect of the third metacarpal bone in racing Thoroughbreds

OBJECTIVEnTo 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.nnnSAMPLE POPULATIONn12 third metacarpal bone pairs from racing Thoroughbreds euthanized for diverse reasons.nnnPROCEDURESnBoth 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.nnnRESULTSnCondylar 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).nnnCONCLUSIONS AND CLINICAL RELEVANCEnThe 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.

Use of quantitative ultrasonography for noninvasive surveillance of the third metacarpal bone in racing and training Thoroughbreds

OBJECTIVE-To use quantitative ultrasonography to evaluate the association between the speed of sound (SOS) at 9 sites in the third metacarpal bone (MCIII) of racing Thoroughbreds with workload accumulation and the effect that MCIII failure has on this association. ANIMALS-Sixty-two 2- and 3-year-old Thoroughbreds in racing condition. PROCEDURES-Cumulative work index (CWI) was used to calculate total workload (CWI(total)) and also 3 independent CWIs for the various gaits (ie, trot [CWI(trot)], gallop [CWI(gallop)], and race [CWI(race)]) used during training and racing. Speed of sound was monitored in horses during the 2007 racing season and compared with the CWIs via regression analysis. Sex, age, limb, and MCIII failure were included as covariates in the model. RESULTS-SOS was significantly associated with CWI(total) at 8 sites and with independent CWIs of the various gaits at all 9 sites. Progression of SOS in MCIIIs with workload differed significantly in horses with clinical signs of metacarpal bone failure, compared with results for horses with clinically normal MCIIIs, in 1 site by use of CWI(total) and in 5 sites by use of the independent CWIs for the various gaits. CONCLUSIONS AND CLINICAL RELEVANCE-These results indicated that SOS in the MCIII of racing Thoroughbreds followed a constant pattern of progression as workload accumulated. With the development of more precise quantitative ultrasonography devices, SOS corrected for amount of activity may be used to identify horses at risk of bone failure.

Repeatability of gait pattern variables measured by use of extremity-mounted inertial measurement units in nonlame horses during trotting.

OBJECTIVE To determine repeatability of gait variables measured by use of extremity-mounted inertial measurement units (IMUs) in nonlame horses during trotting under controlled conditions of treadmill exercise. ANIMALS 10 horses. PROCEDURES Six IMUs were strapped to the metacarpal, metatarsal, and distal tibial regions of each horse. Data were collected in a standardized manner (3 measurements/d on 3 d/wk over a 3-week period) while each horse was trotted on a treadmill. Every measurement consisted of a minimum of 20 strides from which a minimum of 10 strides was selected for analysis. Spatial and temporal variables were derived from the IMUs. Repeatability coefficients based on the within-subject SD were computed for each gait analysis variable at each week. RESULTS Most of the temporal and spatial variables had high repeatability (repeatability coefficients < 10), and the repeatability coefficients were consistent among the 3 weeks of data collection. Some spatial variables, specifically the symmetry variables (which were calculated from other variables), had somewhat higher repeatability coefficients (ie, lower repeatability) only in the last week. CONCLUSIONS AND CLINICAL RELEVANCE With the exceptions of some symmetry variables, which may reflect individual variations during movement, the extremity-mounted IMUs provided data with high repeatability for nonlame horses trotting under controlled conditions of treadmill exercise. Repeatability was achieved for each instrumented limb segment with regard to the spatial relationship between 2 adjacent segments (joint angles) and the temporal relationship among all segments (limb phasing). Extremity-mounted IMUs could have the potential to become a method for gait analysis in horses.

Changes in hoof surface strain distribution in response to moderate exercise in Standardbreds

OBJECTIVEnTo quantify changes in hoof wall strain distribution associated with exercise and time in Standardbreds.nnnANIMALSn18 young adult Standardbreds.nnnPROCEDURESn9 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.nnnRESULTSnBoth 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.nnnCONCLUSIONS AND CLINICAL RELEVANCEnDetected 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.