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Objective—To evaluate the effects of continuous oral administration of phenylbutazone on serum and synovial fluid biomarkers of skeletal matrix metabolism in horses.

Animals—11 adult female horses without clinical or radiographic evidence of joint disease.

Procedures—Horses were randomly assigned to control or treatment groups. Phenylbutazone was administered orally twice daily at a dose of 4.4 mg/kg for 3 days to the treatment group and subsequently at a dose of 2.2 mg/kg for 7 days. Serum and radiocarpal synovial fluid samples were obtained at baseline and thereafter at regular intervals for 4 weeks. Biomarkers of cartilage aggrecan synthesis (chondroitin sulfate 846) and type II collagen synthesis (procollagen type II C-propeptide) and degradation (collagen type II cleavage) were assayed. Biomarkers of bone synthesis (osteocalcin) and resorption (C-terminal telopeptide of type I collagen) were also measured.

Results—No significant differences were found between control and treatment groups or temporally for the biomarkers chondroitin sulfate 846, procollagen type II C-propeptide, collagen type II cleavage, and C-terminal telopeptide of type I collagen in serum or synovial fluid. A significant increase in osteocalcin concentration occurred in synovial fluid during treatment in the treated group. No treatment effect was detected for serum osteocalcin concentration.

Conclusions and Clinical Relevance—Results suggested that continuous phenylbutazone administration at recommended doses altered some biomarkers in healthy equine joints after short periods of administration. Increased osteocalcin concentration may indicate an undetermined anabolic effect of phenylbutazone administration on periarticular bone or transient induction of osteogenesis in articular chondrocytes or a mesenchymal subpopulation of synoviocytes.

Full access
in American Journal of Veterinary Research


OBJECTIVE To measure the minimal joint space width (mJSW) in caudocranial radiographic views of orthopedically normal femorotibial joints of horses, to compare the accuracy of measurements with those of a software program designed for humans, and to identify the ideal caudocranial radiographic projection angle for mJSW measurement.

ANIMALS 12 healthy mares (22 femorotibial joints) and 3 equine cadavers (6 stifle joints).

PROCEDURES Caudocranial views of femorotibial joints were acquired in the proximodistal plane at 5°, 10°, and 15° (caudo-5°-proximal-craniodistal oblique, 10°, and 15°) and lateromedial plane (caudo-10°-proximo-5°-lateral-craniodistomedial oblique and caudo-10°-proximo-5°-medial-craniodistolateral oblique). The mJSWs of medial and lateral femorotibial joint compartments were measured manually by 2 evaluators and automatically by a digital analysis software program. Interevaluator reproducibility was assessed. Post hoc tests were used to identify the projection angle that provided the largest measurements. Validation of mJSW measurements was performed by evaluation of 6 stifle joints ex vivo.

RESULTS Excellent agreement was achieved between the 2 evaluators and between the veterinary radiologist and the analysis software for the medial and lateral compartments of femorotibial joints. Angle of caudocranial view in the proximodistal but not lateromedial plane had a significant effect on the medial compartment mJSW measurements. Mean mJSW for the medial compartment was significantly higher for the caudoproximal-craniodistal oblique projection made at 10° from the horizontal than for other angles. Angle had no significant effect on mean mJSW for the lateral compartment. Agreement between automated measurements of mJSW in the medial compartment and thickness of nonmineralized cartilage in histologic preparations of associated tissues was excellent.

CONCLUSIONS AND CLINICAL RELEVANCE Measurements of mJSW in the medial compartment of femorotibial joints, the most common site of osteoarthritis in horses, were reproducible and optimal with a caudoproximal-craniodistal oblique radiographic projection made at 10° from the horizontal. (Am J Vet Res 2016;77:127–136)

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in American Journal of Veterinary Research


Objective—To characterize expression of cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1) and regulation of prostaglandin E2 (PGE2) production by equine articular chondrocytes.

Sample Population—Articular cartilage from the metacarpophalangeal joints of 7 adult horses.

Procedure—Equine chondrocyte monolayer cultures were stimulated with different concentrations (2.5, 5, 10, and 20 ng/mL) of recombinant human interleukin- 1β (rhIL-1β) for 24 hours and then with rhIL-1β (5 ng/mL) for 3, 6, 9, 12, and 24 hours. Concentration of PGE2 in the media was measured via radioimmunoassay. Total RNA was extracted from harvested chondrocytes, and regulation of COX-2 and mPGES-1 mRNA was studied via reverse transcriptase-polymerase chain reaction assay and Southern blot analysis with equine-specific probes. Western blot analyses were performed on cellular extracts to characterize expression of COX-2 and mPGES-1 protein.

Results—Stimulation with 5, 10, and 20 ng of rhIL- 1β/mL caused a significant increase in PGE2 concentrations in the culture media, and incubation of cells with rhIL-1β (5 ng/mL) for 6 to 24 hours increased PGE2 production significantly. The increase in prostaglandin production was associated with an induction of COX-2 and mPGES-1 transcripts. There also was an rhIL-1β–dependent induction in COX-2 and mPGES-1 protein expression.

Conclusions and Clinical Relevance—Collectively, results indicated that the rhIL-1β–dependent increase in PGE2 production in equine chondrocytes in monolayer culture was associated with coordinated upregulation of COX-2 and mPGES-1 expression. The pathophysiologic consequences of upregulated COX-2 and mPGES-1 expression and of PGE2 synthesis in rhIL-1β–stimulated equine chondrocytes remain to be elucidated. (Am J Vet Res 2005;66:1985–1991)

Full access
in American Journal of Veterinary Research


Objective—To ultrasonographically quantify experimentally induced effusion of the distal interphalangeal (DIP) joint of horses and compare results with those obtained with palpation.

Sample—8 forelimbs from equine cadavers and forelimbs of 5 mares.

Procedures—Preliminary ex vivo experiments were performed to validate the methods. Then, the DIP joints of the forelimbs of standing horses were serially distended with saline (0.9% NaCl) solution (1, 4, and 10 mL) by injection through an intra-articular catheter. Two ultrasonographers measured distension of the dorsal recess of the DIP joint, and 2 surgeons, who were not aware of the volume injected, graded joint effusion by palpation.

Results—Intraobserver and interobserver repeatability was excellent for ultrasonographic measurements. Interobserver agreement for use of palpation to detect joint distension was moderate (κ = 0.45). There was an overall increase in the palpation distension grade with an increase in injected volume. Sensitivity for detection with palpation of larger volumes (4 and 10 mL) was high (92% and 100%, respectively). However, sensitivity was lower (57%) for detection with palpation of minimal distension (1 mL).

Conclusions and Clinical Relevance—Although palpation provided a reliable clinical assessment of DIP joint effusion for volumes of 4 to 10 mL, ultrasonographic measurements were easy to obtain, more accurate, and able to detect smaller amounts of distension. This may be clinically relevant for the assessment of effusion of the DIP joint that can arise in horses with early osteoarthritis or infectious arthritis with concomitant soft tissue swelling that precludes accurate assessment with palpation.

Full access
in American Journal of Veterinary Research


Objective—To identify the prevalence of fragmentation of the proximal tubercle of the talus (FPTT) in a hospital population of horses, characterize the anatomic features of the affected area and fragments, and describe clinical findings, diagnosis, treatment, and outcome for horses with FPTT.

Design—Retrospective case series.

Animals—9 horses with FPTT.

Procedures—2,543 radiographic views of the tarsal region of 1,526 horses that were evaluated between June 2004 and December 2010 were reviewed. Medical case records for horses with detectable FPTT were retrieved, and signalment, history, clinical signs, diagnostic methods, treatment, and outcome were recorded for assessment.

Results—9 horses (median age, 5 years; age range, 1 to 12 years) with FPTT were identified. Seven horses were warmbloods. Diagnosis was made on the basis of radiographic findings, occasionally along with results of ultrasonography and CT. The only horse that was lame in the affected limb had a history of a prior traumatic event and resultant lateral tibial malleolus fracture. One horse underwent arthroscopy, but fragments were not found and were presumed to be extra-articular. Outcome was available for 7 horses; mean ± SD duration of stable radiographic and clinical examination findings was 3 ± 1 years (range, 1 to 4 years).

Conclusions and Clinical Relevance—FPTT appeared to occur more frequently in warmbloods and was not usually associated with lameness. Affected horses remained clinically and radiographically stable over time. These data have provided some information regarding the importance of FPTT for practitioners who perform radiographic screenings during prepurchase examinations.

Restricted access
in Journal of the American Veterinary Medical Association