Intra-articular injection of an extended-release flavopiridol formulation represents a potential alternative to other intra-articular medications for treating equine joint disease.

OBJECTIVE: To establish the pharmacokinetics of the cyclin-dependent kinase-9 inhibitor flavopiridol in equine middle carpal joints, using an extended-release poly lactic-co-glycolic acid (PLGA) microparticle formulation. ANIMALS: 4 healthy horses without evidence of forelimb lameness. METHODS: A 6-week longitudinal pharmacokinetic study was conducted in 2 phases (6 weeks each) in 4 healthy horses. The PLGA microparticles containing 122 µg flavopiridol in 3 mL saline were administered by intra-articular injection into 1 middle carpal joint, with empty PLGA microparticles injected into the contralateral joint as a control. Synovial fluid and plasma were collected at time points out to 6 weeks, and drug concentrations in synovial fluid and plasma were determined using validated protocols. Synovial fluid total protein and total nucleated cell count and differential, CBC, serum biochemistry, and lameness exams were performed at each of the time points. RESULTS: Synovial fluid flavopiridol averaged 19 nM at week 1, gradually reduced to 1.4 nM by 4 weeks, and was generally below the detection limit at 5 and 6 weeks. There was no detectable flavopiridol in the plasma samples, and no adverse effects were observed at any time point. CLINICAL RELEVANCE: Intra-articular injection of PLGA microparticle-encapsulated flavopiridol was well tolerated in horses, with detectable levels of flavopiridol in the synovial fluid out to 4 weeks with negligible systemic exposure. Flavopiridol is a cyclin-dependent kinase-9 inhibitor with potent anti-inflammatory and analgesic activity. The extended-release microparticle formulation promotes intra-articular retention of the drug and it may be an alternative to other intra-articular medications for treatment of equine joint disease.

Athletic prognosis following arthroscopic removal of osteochondral fragments of the proximal dorsal sagittal ridge of the fetlock in Thoroughbreds intended for flat racing.

OBJECTIVE: To establish racing prognosis in Thoroughbred yearlings with proximal sagittal ridge osteochondral lesions and compare them to dorsoproximal and palmar/plantar first phalanx osteochondral lesions. ANIMALS: A total of 47 horses had proximal sagittal ridge lesions, 34 had palmar/plantar first phalanx lesions, and 115 had dorsoproximal first phalanx lesions. STUDY DESIGN: Retrospective case series. METHODS: Medical records of Thoroughbred yearling racing prospects treated arthroscopically for fetlock osteochondral lesions were reviewed. Data were collected from a public database, including the ability to train and race, earnings, starts, wins, and placed races. Racing prognosis was analyzed and compared between three lesion locations. RESULTS: Of the proximal sagittal ridge group, 76.6% raced, 65.71% of the palmar/plantar first phalanx group, and 74.58% of the dorsoproximal first phalanx group. Career length was similar for all lesions. A lower number of "starts" in the group "five years old and older" was found for the dorsoproximal first phalanx group compared to the cohort with proximal sagittal ridge lesions. Mares had more "earnings" at two years old but fewer "starts" at "five years old" compared to colts and geldings. Forelimb lesions were predictive for fewer total career starts. CONCLUSION: Proximal sagittal ridge lesions had similar prognoses to dorsoproximal and palmar/plantar first phalanx lesions. In older horses, there was an increase in the number of starts for the proximal sagittal ridge group compared to the dorsoproximal first phalanx group. Mares and forelimb lesions were associated with decreased racing starts. CLINICAL SIGNIFICANCE: These findings aid in prognostication for Thoroughbreds with osteochondral lesions removed arthroscopically in the fetlock joint.

Treatment Comparison for Medial Femoral Condyle Subchondral Cystic Lesions and Prognosis in Yearling Thoroughbred Racehorse Prospects.

Subchondral cystic lesions (SCL) in the medial femoral condyle are a usual finding in Thoroughbred survey and auction repository radiographs. Several treatments with different outcomes have been studied over the years to improve soundness and racing prognosis. Our objective was to report the racing prognosis in Thoroughbred yearlings intended for racing that were diagnosed with SCL in the medial femoral condyle and were treated using four current and different techniques: intralesional injection of corticosteroids, SCL debridement through the joint with a drill bit, translesional cortical screw placement, and absorbable hydroxyapatite implant placement. Data from 182 Thoroughbred yearlings treated for SCL in the medial femoral condyle were collected from 2014 to 2020. Limb affected, age at surgery, sex, and radiographic measurements of the SCL were recorded. Auction price and racing performance were collected for treated horses and compared to 154 maternal siblings free of medial femoral condyle SCL. Analyses were conducted to assess if racing prognosis was affected by SCL size, to detect differences in auction price and selected flat racing outcome parameters between cases and controls, and to compare racing prognosis between the studied treatments. Mares and lesions located in the right stifle were significantly overrepresented. The auction price of treated horses was significantly lower than that of their siblings. Horses treated for SCL had significantly lower chances to start in a race than controls (59% vs. 74% respectively). Wider SCL negatively affected the chances to start at least in one race, and negatively affected the earnings made in the 2-year-olds' racing year. Horses with SCL treated using a bioabsorbable implant had a significantly higher median in starts as 3-year-olds (seven starts) than horses that had the SCL debrided with a drill bit (three starts). In conclusion, Thoroughbred yearlings treated for a medial femoral condyle SCL had lower auction prices and decreased ability to start a race compared to siblings' wider cysts had worse prognosis to start a race and might affect earnings as 2-year-olds; and horses treated with bioabsorbable composite implant placement had more starts as 3-year-olds than with other techniques.

Comparison of 18 F-sodium fluoride positron emission tomography and computed tomography for imaging of the fetlock in 25 nonracehorses.

BACKGROUND: 18 F-sodium fluoride (18 F-NaF) positron emission tomography (PET) has been validated as a useful imaging technique in the racehorse fetlock. The use of 18 F-NaF PET in the nonracehorse fetlock has not been reported. OBJECTIVES: To describe 18 F-NaF PET findings in nonracehorse fetlocks, to compare with computed tomography (CT) findings and to compare PET findings between horses with and without fetlock pain. STUDY DESIGN: Retrospective observational study. METHODS: All horses undergoing 18 F-NaF PET and CT imaging of the fetlock between October 2016 and March 2021 were included in the study. Medical records were reviewed for associated lameness information. RESULTS: Thirty-six fetlocks (33 front and 3 hind) from 25 horses were included. The interobserver agreement for PET [0.62 (95% confidence interval [CI] 0.59-0.65)] was higher than for CT [0.47 (95% CI 0.43-0.51)]. Increased 18 F-NaF uptake was most common in the medial subchondral bone of the proximal phalanx (23/36), the dorsomedial (20/36) and dorsosagittal (16/36) metacarpal/metatarsal distal subchondral bone, whereas sclerosis was identified on CT in these areas in 22 of 36 (p > 0.9), 33 of 36 (p = 0.001) and 23 of 36 (p = 0.15), respectively. Significant correlations were found between PET grades and both subchondral sclerosis and resorption CT grades (p < 0.001, Spearman r = 0.19 and 0.21, respectively). Abnormal 18 F-NaF uptake in the proximal sesamoid bones (PSBs) was identified in 12 of 36 of the fetlocks, which was more common than CT abnormalities (3/36, p = 0.02). Periarticular increased uptake was seen in 7 of 36 fetlocks, whereas osteophytosis was recognised on CT in 20 of 36 (p = 0.1). Maximal standardised uptake values (SUVmax) were significantly higher in painful than in nonpainful fetlocks (22.0 and 11.9, respectively, p = 0.038). MAIN LIMITATIONS: Retrospective study and limited sample size. CONCLUSIONS: Overall PET and CT findings follow a similar distribution in their location. PET identified more abnormalities in the PSBs than CT. SUVmax is a pertinent factor to take into consideration for the assessment of the clinical significance of findings.

Treatments and Prognosis for Subchondral Cystic Lesions in the Distal Extremities in Thoroughbred Prospect Racehorses.

Subchondral cystic lesions (SCLs) in equines and their treatments have been mainly studied in the medial femoral condyle of the femur. SCLs in the distal extremities affecting the fetlock or interphalangeal joints are frequent, but treatment or prognosis studies in horses are currently sparse. Our objective was to compare four treatments for SCLs in the distal extremities (intralesional injection of corticosteroids, transcortical drilling, cortical screw placement, and absorbable hydroxyapatite implant placement) and report the racing prognoses for affected thoroughbred yearlings. Data from 113 thoroughbred yearlings treated for SCLs in the distal extremities were collected from 2014 to 2020. Age at surgery, sex, bone affected, radiographic SCL measurements, SCL shape, and type of treatment were recorded. Sale data and racing performance were collected for the operated horses and for 109 maternal siblings that were free of SCLs. An analysis was conducted to assess if SCL size affected racing prognosis and to detect differences in sale value and selected racing parameters between the cases and controls. The outcomes for the different treatments, the different bones affected, and the SCL shape type were also analyzed. There was no difference in the ability to start in a race between the cases and controls (60.2% vs. 69.7%, respectively). The auction value of the treated horses was significantly lower than that of their siblings. The bone affected did not impact any of the racing variables studied, whereas the height of the SCLs negatively affected the number of wins and placed races. The type of treatment for the horses affected by SCLs did not have an impact on sale prices, ability to start a race, race starts, wins, and places, or age at the time of the first start. In conclusion, yearlings diagnosed with an SCL in the distal extremities had lower auction prices and decreased racing performances, with lower numbers of wins correlated with larger SCL heights compared to the siblings. Similar racing performance was found regardless of the treatment received.

18F-sodium fluoride positron emission tomography provides pertinent additional information to computed tomography for assessment and management of tarsal pain in horses.

OBJECTIVE: To assess the value of 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) for imaging the tarsus and proximal metatarsus and compare it with CT and lameness evaluation. ANIMALS: 25 horses with lameness localized to the tarsal and proximal metatarsal regions that underwent 18F-NaF PET/CT between 2016 and 2021. METHODS: 18F-NaF PET and CT images were retrospectively independently evaluated by 3 observers. Standardized uptake values (SUV) were used to characterize 18F-NaF uptake. Correlation between PET and CT findings with subjective and objective maximum (Max-D) and minimum pelvic height lameness data was estimated. RESULTS: The inter-observer Kappa-weighted value (κ) was higher for PET (κ = 0.66) than CT (κ = 0.6). CT and PET scores were fairly correlated (R = 0.49; P < 0.05). PET SUVratio (SUV of the main lesion/SUV talus) had the highest correlation with Max-D (R = 0.71; P < .05). PET and CT scores for the plantar region were significantly higher in Quarter Horses (P < .05) and showed consistently higher correlation with objective lameness data (CT plantar grade - Max-D [R = 0.6; P < .05], PET plantar grade - Max-D [R = 0.47; P = .04]) than other regions of the distal tarsal joints. Three Warmbloods presented marked uptake at the medial cochlea of the distal tibia. CLINICAL RELEVANCE: PET had a moderate correlation with CT for assessment of tarsal lesions. The degree of PET uptake can help differentiate active versus inactive lesions. Specific location of the uptake is important in determining clinical relevance.

Progression of shallow medial femoral condyle radiographic lucencies in Thoroughbred repository radiographs and their influence on future racing careers.

BACKGROUND: Shallow lucencies less than 4 mm deep into the medial femoral condyle (MFC) are frequent in Thoroughbred horses undergoing screening sales radiographs. It is unclear if these shallow defects are precursors to larger cystic lesions or if they are fully developed defects that remodel into a flattened femoral condyle. OBJECTIVE: To evaluate radiological lucencies of the MFC and their progression in size, in a cohort of Thoroughbred horses, ranging from 5 to 18 months of age and to report on the racing careers of these horses compared to their maternal siblings free of stifle pathology. STUDY DESIGN: Retrospective cohort. METHODS: Radiographic reports were reviewed to identify cases with MFC lucency. Medical data including age at the time of radiographic sale set, sex, and MFC lucency radiographic measurements were recorded. The data were analysed for changes in lucency morphology. Racing data were collected and analysed for the following 5 years. RESULTS: From 12 938 sales reports reviewed, 3874 horses were found to have radiographic sets available at both weanling and yearling sales. A MFC lucency ≤3 mm in depth was diagnosed in at least one radiographic sales set in 248 horses (6.4%). The right femur was more commonly affected (73.9%) than the left. Radiographic lucencies in the left femur were significantly smaller (P = .02) than lucencies in the right femur. Radiographic lucencies resolved in 6.1% of cases, 3.6% of cases developed into a cyst, 40.7% of cases were unchanged in size, 23.6% of lucencies decreased in size and 8.2% increased in size. Cysts >3 mm deep regressed into smaller lesions accounting for 4.9% of the lucencies, and 12.9% of lucencies developed from a normal or flat medial femoral condyle contour. Horses with a medial femoral condyle lucency had significantly less starts as a 2-year-old vs. their maternal siblings (P < .01). MAIN LIMITATIONS: Data were collected retrospectively. Measurement errors may have occurred due to the measuring tool scale, small size of the defects and/or radiographic position. Treatments between radiographic studies were unknown and could not be accounted for. Observers were not blinded to radiographic sales reports. CONCLUSIONS: Radiographically diagnosed lucencies in the MFC of immature Thoroughbreds have the potential to fully resolve or develop into a cyst. However, most radiographic lucencies do not change in size. Thoroughbreds with MFC lucencies had less starts as 2-year-olds when compared to their maternal siblings free of stifle pathology.

Evaluation of the caudal cervical articular process joints by using a needle arthroscope in standing horses.

OBJECTIVE: To determine the safety and efficacy of caudal cervical articular process joint arthroscopy by using needle arthroscopy in standing sedated horses. STUDY DESIGN: Prospective experimental case series. ANIMALS: Six adult horses. METHODS: Three horses underwent exploration of bilateral C5-6 vertebral articular process joints and three bilateral C6-7 articular process joints by using a 1.2 × 65-mm needle arthroscope under standing sedation. The 16-gauge arthroscopic trocar and canula assembly was inserted in the desired articular process joint under ultrasonographic guidance without distention of the joint. RESULTS: All 12 articular process joints were successfully explored. Entering the joint on the first attempt was achieved in 10 of 12 joints. A craniodorsal approach for arthroscope insertion allowed evaluation of the most cranial aspect of the articular cartilage surface. Triangulation with a spinal needle was determined to be difficult and resulted in a limited space for movement. CONCLUSION: Needle arthroscopy of the caudal cervical facet joints was performed safely and efficiently in standing sedated horses. CLINICAL SIGNIFICANCE: Standing cervical articular process needle arthroscopy is a minimal morbidity technique with the potential to be an advantageous technique for the diagnosis and treatment of cervical articular process pathology.

Evaluation of the effects of initial water temperature and curing time on fiberglass cast strength.

OBJECTIVE: To determine the effects of water temperature and cure time on cast strength. STUDY DESIGN: Prospective randomized experimental study. METHODS: Two water temperatures were tested, 23°C (cold) and 42°C (warm). Cast constructs were made of 4-inch fiberglass casting material over a rubber mandrel. Each construct was divided into 3 segments and tested in 4-point bending at 0.5, 1, and 24 hours. Stiffness and bending moment, cumulative energy, and angular deformation at yield and failure were recorded and analyzed by using repeated measures ANOVA. RESULTS: Mean time ± SD to complete the construct was 2.2 ± 0.8 and 2.3 ± 0.6 minutes for warm and cold water, respectively. Warm water and longer cure times produced constructs with greater stiffness (23.05 vs 20.88 newton-meter degrees [Nm°] at 0.5 hours), bending moment (121.75 vs 107.31 Nm° at 0.5 hours), and cumulative energy (557.33 vs 428.89 Nm° at 1 hour) at yield and failure. Longer cure time significantly increased angular deformation of rods at failure; however, water temperature did not. In general, the strongest casts were produced with warm water and after curing for 24 hours. CONCLUSION: Fiberglass casts continued to gain strength for at least 24 hours. Use of warm water increased the rate of curing, resulting in stronger constructs at earlier time points. CLINICAL SIGNIFICANCE: Use of warm water is recommended to initiate fiberglass cast curing, especially if the casted limb will be loaded soon after cast application.