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To evaluate bone mineral content patterns between fracture configurations using novel CT image analysis.


CT images from 97 Thoroughbred racehorses with third metacarpal/tarsal condyle fractures provide the case population for analysis.


Fractures were grouped by radiographic appearance. Image analysis objectively measured area of highly attenuating pixels (aHAP), areal density of highly attenuating pixels (dHAP) utilizing novel convex hull analysis, and subjective assessment of apparent attenuation intensity ranking (AAIR) for each fracture. Differences between fracture configuration groups were evaluated.


Analysis of dHAP identified lower-density regions of highly attenuating pixels in propagating fractures and higher-density regions of highly attenuating pixels in unicortical fractures (P = .028). Complete and incomplete configurations were almost indistinguishable in dHAP (P = 1.000). The ratio of dHAP between fractured and nonfractured condyles revealed higher density gradients between condyles in unicortical (P = .040) and incomplete (P = .031) fractures than propagating fractures.


Differences in patterns of bone mineral content were identified between propagating, bicortical (incomplete and complete), and unicortical fractures of third metacarpal/tarsal bone condyles. Computer-assisted geometric measurement of dHAP identified on CT images could help to assess fracture risk in equine athletes. This application may have greater relevance as standing CT screening becomes more available.

Open access
in American Journal of Veterinary Research


Objective—To characterize medial femoral condyle (MFC) morphometrics and subchondral bone density patterns in Thoroughbred racehorses and to determine whether these variables differ between left and right limbs.

Sample—Stifle joints harvested from 6 Thoroughbred racehorses euthanized for reasons other than hind limb lameness.

Procedures—The distal portion of the left and right femurs of each cadaver was scanned via CT. Hounsfield units were converted to dipotassium phosphate equivalent densities through use of a phantom on each specimen. Medial femoral condyle width, length, height, and curvature; subchondral bone plate densities; and subchondral trabecular bone densities were analyzed in multiple sections in 5 frontal planes and 3 sagittal planes and were compared between left and right MFCs.

Results—MFC width, length, and height did not differ between left and right limbs. Regions of interest in the right caudoaxial subchondral bone plate and subchondral trabecular bone were significantly denser than their corresponding left regions of interest in the frontal and sagittal planes. A concavity in the otherwise convex articular surface of the cranial aspect of the MFC was identified in 11 of 12 specimens.

Conclusions and Clinical Relevance—A disparity was identified between left and right subchondral bone density patterns at the caudoaxial aspect of the MFC, which could be attributable to the repetitive asymmetric cyclic loading that North American Thoroughbred racehorses undergo as they race in a counterclockwise direction. The uneven region at the cranial aspect of the MFC could be associated with the development of subchondral bone cysts in horses.

Full access
in American Journal of Veterinary Research


OBJECTIVE To determine the ability of an accelerometer within a commercially available portable media device (PMD) to measure changes in postural stability of standing horses during various stance conditions and to compare these results with data obtained by use of a stationary force platform.

ANIMALS 7 clinically normal horses.

PROCEDURES A PMD was mounted on a surcingle; the surcingle was placed immediately caudal to the highest point of the shoulders (withers). Each horse was examined while standing on a stationary force platform system in a normal square stance, forelimb base-narrow stance, and normal square stance at 5 and 10 minutes after sedation induced by IV administration of xylazine hydrochloride. A minimum of 5 trials were conducted for each stance condition. Ranges of craniocaudal and mediolateral motion as well as SDs were collected for the PMD and force platform system. Analyses were performed with mixed-model ANOVAs, and correlation coefficients were calculated.

RESULTS Stance condition significantly altered craniocaudal accelerations measured by use of the PMD, all craniocaudal and mediolateral displacements of the center of pressure, and velocities measured by use of the stationary force platform. For both the PMD and force platform, SDs were significantly affected by stance condition in both craniocaudal and mediolateral directions. Correlation coefficients between the systems for all variables were low to moderate (r = 0.18 to 0.58).

CONCLUSIONS AND CLINICAL RELEVANCE Body-mounted PMDs should be investigated for use in assessment of postural stability in horses with neuromuscular abnormalities.

Full access
in American Journal of Veterinary Research


Objective—To assess clinical, radiographic, histologic, and biochemical effects of sodium pentosan polysulfate (NaPPS) administered IM for treatment of experimentally induced osteoarthritis in horses.

Animals—18 horses.

Procedures—Osteoarthritis was induced arthroscopically in 1 middle carpal joint of all horses. Nine horses received NaPPS (3 mg/kg, IM) on study days 15, 22, 29, and 36. Nine control horses received the same volume of saline (0.9% NaCl) solution IM on study days 15, 22, 29, and 36. Clinical, radiographic, gross, histologic, histochemical, and biochemical findings as well as findings of synovial fluid analysis were evaluated.

Results—No adverse treatment-related events were detected. Induced osteoarthritis caused a substantial increase in lameness, response to flexion, joint effusion, radiographic findings, synovial membrane inflammation, and articular cartilage fibrillation. Articular cartilage fibrillation was substantially reduced by NaPPS treatment, and concentrations of chondroitin sulfate 846 epitope were significantly increased in the synovial fluid of osteoarthritic and nonosteoarthritic joints of treated horses.

Conclusions and Clinical Relevance—Results indicated that NaPPS has some beneficial disease-modifying effects and may be a therapeutic option for osteoarthritis in horses.

Full access
in American Journal of Veterinary Research


Objective—To assess the clinical, biochemical, and histologic effects of extracorporeal shock wave therapy (ESWT) in the treatment of horses with experimentally induced osteoarthritis (OA).

Animals—Twenty-four 2- to 3-year-old horses without evidence of lameness.

Procedures—OA was induced arthroscopically in 1 middle carpal joint of each horse. Fourteen days after induction of OA, horses were treated with a sham ESWT probe (placebo; n = 8), polysulfated glycosaminoglycan (PSGAG) administered IM every 4 days for 28 days as a positive control treatment (8), or ESWT administered on days 14 and 28 with a focused shock wave unit (8). Evaluations included clinical assessments of degree of lameness every 2 weeks and weekly synovial fluid analyses. Horses were euthanized 70 days after induction of OA, and gross pathologic and histologic examinations of cartilage and synovial membrane specimens were performed at necropsy. A generalized linear mixed model was used to compare outcomes among treatment groups.

Results—No adverse treatment-related events were detected in any horse. The degree of lameness in horses treated with ESWT improved significantly, compared with the degree of lameness in placebo- or PSGAG-treated horses. No disease-modifying effects were evident in results for synovial fluid, synovial membranes, or cartilage from the ESWT- or PSGAG-treated horses.

Conclusions and Clinical Relevance—Although a disease-modifying effect of ESWT was not detected, the significant clinical effect of ESWT suggested that this modality should be considered for treatment of horses with OA in combination with another modality that does affect the disease process.

Full access
in American Journal of Veterinary Research


OBJECTIVE To evaluate the efficacy of IV administration of a product containing hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine for prevention or treatment of osteoarthritis in horses.

ANIMALS 32 healthy 2- to 5-year-old horses.

PROCEDURES The study involved 2 portions. To evaluate prophylactic efficacy of the test product, horses received 5 mL of the product (n = 8) or saline (0.9% NaCl) solution (8; placebo) IV every fifth day, starting on day 0 (when osteoarthritis was induced in the middle carpal joint of 1 forelimb) and ending on day 70. To evaluate treatment efficacy, horses received either the product or placebo (n = 8/treatment) on days 16, 23, 30, 37, and 44 after osteoarthritis induction. Clinical, diagnostic imaging, synovial fluid, gross anatomic, and histologic evaluations and other tests were performed. Results of each study portion were compared between treatment groups.

RESULTS Limb flexion and radiographic findings were significantly worse for horses that received the test product in the prophylactic efficacy portion than for placebo-treated horses or product-treated horses in the treatment efficacy portion. In the prophylactic efficacy portion, significantly less articular cartilage erosion was identified in product-treated versus placebo-treated horses. In the treatment efficacy portion, joints of product-treated horses had a greater degree of bone edema identified via MRI than did joints of placebo-treated horses but fewer microscopic articular cartilage abnormalities.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that caution should be used when administering the evaluated product IV to horses, particularly when administering it prophylactically, as it may have no benefit or may even cause harm.

Full access
in American Journal of Veterinary Research



To evaluate the effects of a commercially defined, serum-free medium additive on equine articular cartilage explants, compared with effects of serum-free and serum-supplemented media.


Articular cartilage from a 3-year-old, mixed breed horse euthanatized for reasons other than musculoskeletal disease or sepsis.


Media were changed every 48 hours, and the glycosaminoglycan (GAG) content was determined in media collected at each time point. Glycosaminoglycan synthesis by explant chondrocytes, and residual GAG content of articular cartilage (as a measure of explant GAG loss) were determined at the end of the study (day 8).


Articular cartilage explants in serum-free medium and the commercial supplemented medium had significantly lower GAG synthesis and GAG content than did those incubated in serum-supplemented medium. There were no significant differences in GAG synthesis and content between serum-free and commercial supplemented medium groups. When comparing medium GAG content for all treatment groups, the GAG content in serum-free medium on day 8 was significantly greater than that in commercial supplemented medium, but significant differences were not evident in percentage of release of GAG (as an indicator of GAG degradation) among all 3 treatment groups.


Commercial supplemented medium had effects on articular cartilage matrix GAG loss into medium equal to those of serum-supplemented medium (eg, both lost articular cartilage explant GAG to a similar degree). However, residual articular cartilage GAG content was higher in serum-supplemented medium, as was GAG synthesis. Commercial supplemented medium appears to either lack the proper ingredients to maintain steadystate GAG synthesis, or lacks proper concentrations of these ingredients. (Am J Vet Res 1996;57:1261–1265)

Free access
in American Journal of Veterinary Research


Objective—To evaluate the sedative and analgesic effects of subanesthetic doses of ketamine in horses sedated with xylazine, with or without butorphanol.

Design—Prospective, randomized, controlled study.

Animals—10 adult horses.

Procedures—Each horse was sedated multiple times by administration of xylazine (treatment X), xylazine and butorphanol (treatment XB), xylazine with 1 of 2 dosages of ketamine (treatment XK1 or XK2), or xylazine and butorphanol with 1 of 2 dosages of ketamine (treatment XBK1 or XBK2). Head height and various behaviors, including responses to noise, insertion of a dental float, needle prick on the flank, algometer pressure on the scapula, and bilateral carpal arthrocenteses, were evaluated.

Results—No significant differences were detected among sedation treatments for head height, response to noise, or response to arthrocenteses. Insertion of a dental float was easiest with treatment XBK2 and most difficult with treatments XK1 and XK2. Response to a needle prick on the flank was lowest with treatment XB and highest with treatment XK2. Tolerance to algometer pressure over the scapula was highest with treatment XBK2 and lowest with treatment X.

Conclusions and Clinical Relevance—Administration of a subanesthetic dosage of ketamine with xylazine and butorphanol may facilitate certain procedures, such as insertion of a dental float, in horses and enhance tolerance to pressure stimulation, but it may worsen responses to acute pain, such as that caused by a needle prick. Further evaluation is needed to determine whether subanesthetic dosages of ketamine might be useful when performing certain clinical procedures in horses.

Full access
in Journal of the American Veterinary Medical Association


Objective—To assess the clinical, biochemical, and histologic effects of intra-articular administration of autologous conditioned serum (ACS) in the treatment of experimentally induced osteoarthritis in horses.

Animals—16 horses.

Procedures—Osteoarthritis was induced arthroscopically in 1 middle carpal joint of all horses. In 8 placebo- and 8 ACS-treated horses, 6 mL of PBS solution or 6 mL of ACS was injected into the osteoarthritis-affected joint on days 14, 21, 28, and 35, respectively; PBS solution was administered in the other sham-operated joints. Evaluations included clinical assessment of lameness and synovial fluid analysis (performed biweekly); gross pathologic and histologic examinations of cartilage and synovial membrane samples were performed at necropsy.

Results—No adverse treatment-related events were detected. Horses that were treated with ACS had significant clinical improvement in lameness, unlike the placebo-treated horses. Among the osteoarthritis-affected joints, ACS treatment significantly decreased synovial membrane hyperplasia, compared with placebo-treated joints; although not significant, the ACS-treated joints also appeared to have less gross cartilage fibrillation and synovial membrane hemorrhage. The synovial fluid concentration of interleukin-1 receptor antagonist (assessed by use of mouse anti–interleukin-1 receptor antagonist antibody) was increased following treatment with ACS.

Conclusions and Clinical Relevance—Results of this controlled study indicated that there was significant clinical and histologic improvement in osteoarthritis-affected joints of horses following treatment with ACS, compared with placebo treatment. On the basis of these findings, further controlled clinical trials to assess this treatment are warranted, and investigation of the mechanisms of action of ACS should be pursued concurrently.

Full access
in American Journal of Veterinary Research