Objective:Develop a global joint score (GJS) reflecting equine osteoarthritis (OA) structural severity and identify clinical or molecular parameters predicting disease severity. Methods:A retrospective analysis was performed using data from horses (n = 104; 58 females and 46 geldings; 2 to 5 years old) undergoing experimental OA induction via surgical osteochondral fragment creation in the middle carpal joint and high-speed treadmill exercise over 70 days. Longitudinal measures included subjective lameness examinations (lameness, effusion, and flexion), synovial fluid (SF) and serum glycosaminoglycan (GAG), SF prostaglandin E2, and SF cell and synovium gene expression (mRNA sequencing, n = 8). All samples were collected every 14 days except synovium, which was collected on days 0 and 70. Macroscopic and histopathologic data (day 70) were combined creating a GJS characterizing structural severity. Clinical parameters, biochemical markers, and transcriptomic alterations were modeled against the GJS to identify diagnostic methods predicting severity of OA progression. Results:Subjective lameness examinations and GAG and PGE2 concentrations did not predict OA severity. In contrast, subsets of genes (46 in SF cells and 8 in synovium) demonstrated high predictive value with GJS, coupled with significant endpoint expression changes. Conclusions:Single clinical markers are not strong predictors of disease severity due to the heterogeneity of OA. Gene expression and transcriptomic biomarkers may be more sensitive predictors of disease severity. Clinical Relevance:This study provides preliminary evidence toward the identification of target genes and pathways to further elucidate the pathophysiology of early OA and potential therapeutic targets, advancing our understanding of the molecular underpinnings of joint disease.

OBJECTIVE:To compare implant failure and gap displacement characteristics of simulated medial mid-body proximal sesamoid bone (PSB) fractures repaired with bone-screw-fasteners (BSF) or cortical screws (CS) in single or double screw configurations. STUDY DESIGN:Ex vivo experimental study. SAMPLE POPULATION:A total of 14 paired equine cadaver forelimbs. METHODS:Medial mid-body PSB osteotomies were created in each forelimb. Surgical repair was performed using either: (1) single 3.5 mm BSF (BSFsingle), (2) single 4.5 mm CS (CSsingle), (3) two 3.5 mm BSFs (BSFdouble), or (4) two 3.5 mm cortical screws (CSdouble) (n = 7 repairs/group). Biomechanical properties and failure characteristics were evaluated through a single cycle to failure. Comparisons between groups were made using Wilcoxon-matched pairs or Mann-Whitney tests. Statistical significance was p < .05. RESULTS:The BSFdouble group (2081 ± 181 N) had significantly higher yield than BSFsingle (1458 ± 92 N, p = .01) and CSsingle (1532 ± 86 N, p = .02) groups. The CSdouble group (2101 ± 126 N) had significantly higher yield than BSFsingle (p = .001) and CSsingle (p = .003) groups. Biomechanical properties were not different between BSFsingle and CSsingle groups, or between BSFdouble and CSdouble groups. Gap measurements at construct failure were significantly higher abaxially than axially in all groups (all p < .05). CONCLUSION:No differences were detected between the single BSF and 4.5 mm CS for repair of medial mid-body PSB fractures. Surgical repair using two screws has biomechanical advantage to single screw repair, regardless of screw type ex vivo. CLINICAL SIGNIFICANCE:The BSF is not different to CS for repair of PSB fractures. Counteracting abaxial forces in surgical repair of mid-body PSB fractures warrants further investigation.

Objective:To develop and define a model of acute neck pain in an equine cervical articular process joint (APJ) using recombinant equine IL-1β (reIL-1β). Methods:12 horses in this experimental study received a randomly assigned, unilateral intra-articular injection of 50 ng (n = 6) or 100 ng (n = 6) of reIL-1β and saline (contralateral side as control) into the C5-to-C6 APJ. Blinded ultrasonographic, clinical, and biomechanical parameters were evaluated between 4 hours and 14 days. Results:There was a significant increase in APJ effusion on ultrasonographic examination that peaked at 24 hours (P = .0256; effect size, 0.8312; CI, 1.0594 to 0.629). There was a time effect on the clinical examination score (myofascial pain and stiffness) and a significant decrease in stride length and velocity at 24 hours. There was an adverse event (extravasation of injectate) in 1 horse. Conclusions:Ultrasonographic evidence of the presence and severity of APJ effusion was readily identified and tracked over time. Unilateral injection of the APJ with reIL-1β induced clinical signs of myofascial pain, neck stiffness, and gait adaptations. Using individual control horses, rather than a contralateral saline injection within the same horse, would improve our understanding of the clinical presentation of acute APJ pain using this model. Clinical Relevance:Diagnosing the presence, localization, and clinical effects of neck pain in horses remains challenging and would benefit from the establishment of an experimental model. The induction of acute synovitis using reIL-1β within the C5-to-C6 APJ opens the door for future studies to ultimately better understand equine cervical pain and dysfunction.

Post-traumatic osteoarthritis (PTOA) is a common cause of lameness in the horse. There is no cure, therefore treatments are aimed at reducing pain and improving the joint environment by modifying inflammatory pathways or by viscosupplementation. Here, we report the safety and efficacy of the biolubricant (poly(2-methacryloyloxyethyl phosphorylcholine; pMPC) to mitigate the physical, gross, histological, and biochemical effects of arthritis. We created an osteochondral fragment in the middle carpal joint of one limb in 16 horses to induce PTOA; the contralateral limb served as a sham-operated joint. Two weeks postoperative, half (n = 8) of the horses received a single injection of pMPC in the PTOA joint, while the other half received saline. All sham-operated joints (n = 16) received saline. We conducted clinical evaluations weekly while synovial fluid biomarkers were measured biweekly during the 70-day study period. Subsequently, we performed postmortem gross and histologic analyses. Horses in which PTOA joints were treated with pMPC exhibited mild increases in clinical data, including lameness, effusion, and flexion scores. Similarly, synovial cell count, total protein, and prostaglandin E2 values were higher for pMPC-treated joints. Radiographic changes included significantly higher osteophyte scores in pMPC-treated joints at the terminal timepoint. The biolubricant may demonstrate some chondroprotective effects with lower total erosion scores and higher cartilage glycosaminoglycan content. In summary, when pMPC is administered to PTOA joints, the biolubricant induces a mild inflammatory response but may offer some chondroprotective effects in horses.

Background: Dual-energy (DE) detection of bone marrow edema (BME) would be a valuable new diagnostic capability for the emerging orthopedic cone-beam computed tomography (CBCT) systems. However, this imaging task is inherently challenging because of the narrow energy separation between water (edematous fluid) and fat (health yellow marrow), requiring precise artifact correction and dedicated material decomposition approaches. Purpose: We investigate the feasibility of BME assessment using kV-switching DE CBCT with a comprehensive CBCT artifact correction framework and a two-stage projection- and image-domain three-material decomposition algorithm. Methods: DE CBCT projections of quantitative BME phantoms (water containers 100-165 mm in size with inserts presenting various degrees of edema) and an animal cadaver model of BME were acquired on a CBCT test bench emulating the standard wrist imaging configuration of a Multitom Rax twin robotic x-ray system. The slow kV-switching scan protocol involved a 60 kV low energy (LE) beam and a 120 kV high energy (HE) beam switched every 0.5 degrees over a 200 degrees angular span. The DE CBCT data preprocessing and artifact correction framework consisted of (i) projection interpolation onto matched LE and HE projections views, (ii) lag and glare deconvolutions, and (iii) efficient Monte Carlo (MC)-based scatter correction. Virtual non-calcium (VNCa) images for BME detection were then generated by projection-domain decomposition into an Aluminium (Al) and polyethylene basis set (to remove beam hardening) followed by three-material image-domain decomposition into water, Ca, and fat. Feasibility of BME detection was quantified in terms of VNCa image contrast and receiver operating characteristic (ROC) curves. Robustness to object size, position in the field of view (FOV) and beam collimation (varied 20-160 mm) was investigated. Results: The MC-based scatter correction delivered > 69% reduction of cupping artifacts for moderate to wide collimations (> 80 mm beam width), which was essential to achieve accurate DE material decomposition. In a forearm-sized object, a 20% increase in water concentration (edema) of a trabecular bone-mimicking mixture presented as similar to 15 HU VNCa contrast using 80-160 mm beam collimations. The variability with respect to object position in the FOV was modest (< 15% coefficient of variation). The areas under the ROC curve were > 0.9. A femur-sized object presented a somewhat more challenging task, resulting in increased sensitivity to object positioning at 160 mm collimation. In animal cadaver specimens, areas of VNCa enhancement consistent with BME were observed in DE CBCT images in regions of MRI-confirmed edema. Conclusion: Our results indicate that the proposed artifact correction and material decomposition pipeline can overcome the challenges of scatter and limited spectral separation to achieve relatively accurate and sensitive BME detection in DE CBCT. This study provides an important baseline for clinical translation of musculoskeletal DE CBCT to quantitative, point-of-care bone health assessment.

OBJECTIVE To compare 3 perioperative feeding regimens and their effect on anesthetic complications, manure output, and colic proportion in healthy horses. METHODS 45 horses presenting for elective orthopedic procedures were randomly assigned to 1 of 3 groups: not fasted (NF; continuous access to hay perioperatively), fasted muzzled (FM; 10-hour preoperative fast with slow refeeding postoperatively and muzzle placement), or fasted not muzzled (FNM; same as FM without muzzle placement). Anesthetic protocol was standardized. Outcomes compared between groups included anesthesia time, arterial oxygenation, duration of hypotension, perioperative manure output, time to first passage of manure postoperatively, pain scores, and colic proportion. Comparisons were made with a mixed model and Fisher exact test with statistical significance considered at P <= .05. RESULTS No differences were seen in pain scores, oxygenation, hypotension, or colic between groups. Groups FM and FNM had a significantly greater mean reduction in postoperative manure weight (-81% and -70%; P = .003) and number of manure piles (-63% and -55%; P = .005) compared to group NF (-39% and -22%; P < .001; weight and piles, respectively). Mean +/- SD minutes to passage of manure postoperatively was significantly shorter in group NF (238 +/- 13 minutes) than groups FM (502 +/- 174 minutes; P < .001) and FNM (444 +/- 171 minutes; P = .003). CLINICAL RELEVANCE Horses with continuous access to hay prior to and following recovery from anesthesia passed more manure and passed manure sooner after surgery than their fasted counterparts without detrimental effect on anesthetic param-- eters and postoperative complications. Continuous access to hay perioperatively supports manure production in healthy horses without increase in anesthetic complications.

BackgroundRadiological findings in the proximal sesamoid bones (sesamoids) are a persistent source of controversy at Thoroughbred sales, due to inconsistent classification and conflicting assignment of potential clinical importance.ObjectivesTo define the prevalence of sesamoid findings on sales repository radiographs in yearling and 2-year-old Thoroughbreds and to analyse associations with racing performance. To track the changes in sesamoid findings between 1 and 2 years of age in horses that present for sale at both ages.Study designProspective cohort study using an enrolled sample.MethodsHorses were enrolled from a 2016 yearling sale and five 2017 2-year-old sales with consignor permission. Radiological findings relating to sesamoid vascular channel appearance, abaxial contour changes and sesamoid fragments were examined. Associations between sesamoid findings and racing performance from 2 to 4 years of age were examined using multivariate regression analyses. Clinical follow-up was sought to ascertain why horses that did not race never started.ResultsA total of 2508 yearlings and 436 2-year-olds were included for evaluation. Interobserver agreement using the new grading system was substantial. Yearling findings associated with a significantly reduced probability of starting a race were: Grade 3 vascular channels in forelimb sesamoids (0.52, P < 0.001, 95% confidence interval (CI): 0.37-0.67), abaxial new bone in forelimb sesamoids (0.62, P = 0.01, 95% CI: 0.49-0.73), apical or abaxial fragments in forelimb sesamoids (0.55, P = 0.005, 95% CI: 0.37-0.72). For affected horses that did race, Grade 3 vascular channels in forelimb sesamoids were associated with fewer race starts (9.9 starts, P = 0.03, 95% CI: 8.0-12.2) and Grade 3 vascular channels in hindlimb sesamoids were associated with a delayed start to racing careers (54 days, P = 0.01, 95% CI: 20-89). Abaxial new bone in forelimb sesamoids was associated with a 54% reduction in total earnings (P = 0.003, 95% CI: 24-72) and a 46% reduction in earnings per start (P = 0.002, 95% CI: 21-64). Abaxial concavity occurred predominantly in yearling medial forelimb sesamoids, had no impact on racing performance and mostly resolved by 2-year-old sale.Main limitationsThese findings are applicable to horses presented for sale at public auction and may underestimate the prevalence of severe lesions in non-sales horses.ConclusionsGrade 3 vascular channels, forelimb sesamoid abaxial new bone and forelimb sesamoid fragments are important findings in sales repository radiology. The new grading scale assigns a numerical grade for vascular channel appearance that matches the number of enlarged vascular channels evident in a given sesamoid. Abaxial contour changes, when present in sesamoids that are Grade 0 for enlarged vascular channels, are noted separately as either abaxial new bone or abaxial concavity. Fragments are also noted and interpreted separately.

Background: Equine suspensory ligament branch (branch) ultrasonography is becoming increasingly commonplace presale. No ultrasonographical branch reference data exists for Thoroughbred sales horses. Objectives: To define the prevalence of ultrasonographical findings in the forelimb suspensory branches of yearling and 2-year-old sales Thoroughbreds and to analyse associations with racing performance. To track changes in branch findings between 1 and 2 years of age in horses that present for sale at both ages. Study design: Prospective cohort study using an enrolled sample. Methods: Horses were enrolled from a 2016 yearling sale and five 2017 2-year-old sales with consignor permission. Ultrasonography was performed immediately prior to the sales. Ultrasonographical findings relating to branch size, fibrillar pattern, the presence of hyperechoic foci, periligamentar tissue thickness and the adjacent proximal sesamoid bone surface were examined. Associations with racing performance from 2 to 4 years of age were investigated using multivariate regression analyses. Clinical follow-up was sought to ascertain why horses that did not race never started. Results: A total of 593 sales yearlings and 367 2-year-olds had forelimb branch ultrasonography performed. Grade >= 2 fibrillar branch change was present in 8.9% of yearlings and 14.4% of 2-year-olds. A 0.25 cm increase in branch width was associated with a 49-day delayed start to racing careers (P < 0.001, 95% confidence interval (95% CI): 21-77 days). The presence of grade 2 hyperechoic foci was associated with significantly lower total earnings (P = 0.01, 95% CI: $2000-$16 022) and lower earnings per start (P = 0.003, 95% CI: $349-$1718) in United States Dollars. Grade 3 fibrillar branch change had clinically important reductions in the probability of racing, the calibre of racing performance and earnings. Grade 1 fibrillar pattern was associated with significantly higher earnings per start (P = 0.004, 95% CI: $2641-$5759). Main limitations: The findings are applicable to horses prepared for public auction and deemed fit to be entered for sale. The results may underestimate the proportion of severe lesions in horses not entered for sale. Conclusions: Reference values specific to young Thoroughbreds have been established. Grade 1 fibrillar branch change should be regarded as an acceptable appearance in sales yearlings and 2-year-olds. Approximately one-third of grade 2 yearling branches progressed to a grade 3 lesion. Evidence of enlarged branch width and grade 2 hyperechoic foci at 2-year-old sales constitute a risk to racing performance.

Cationic contrast-enhanced computed tomography (CECT) capitalizes on increased contrast agent affinity to the charged proteoglycans in articular cartilage matrix to provide quantitative assessment of proteoglycan content with enhanced images. While high resolution microCT has demonstrated success, we investigate cationic CECT use in longitudinal in vivo imaging at clinical resolution. We hypothesize that repeated administration of CA4+ will have no adverse side effects or complications, and that sequential in vivo imaging assessments will distinguish articular cartilage repair tissue from early degenerative and healthy cartilage in critically sized chondral defects. In an established equine translational preclinical model, lameness and synovial effusion scores are similar to controls after repeated injections of CA4+ (eight injections over 16 weeks) compared to controls. Synovial fluid total protein, leukocyte concentration, and sGAG and PGE2 concentrations and articular cartilage and synovial membrane scores are also equivalent to controls. Longitudinal in vivo cationic CECT attenuation in repair tissue is significantly lower than peripheral to (adjacent) and distantly from defects (remote sites) by 4 weeks (p < 0.001), and this difference persists until 16 weeks. At the 6- and 8-week time points, the adjacent locations exhibit significantly lower cationic CECT attenuation compared with the remote sites, reflecting peri-defect degeneration (p < 0.01). Cationic CECT attenuation at clinical resolution significantly correlates with cationic CECT (microCT) (r = 0.69, p < 0.0001), sGAG (r = 0.48, p < 0.0001), and ICRS II histology score (r = 0.63, p < 0.0001). In vivo cationic CECT imaging at clinical resolution distinguishes fibrous repair tissue from degenerative and healthy hyaline cartilage and correlates with molecular tissue properties of articular cartilage.

BackgroundChanges in the proximal sesamoid bones (sesamoids) and the insertional region of the adjacent suspensory ligament branch (branch) are of particular importance in young Thoroughbreds sold at public auction. Little is known about the prevalence of concurrent ultrasonographical branch change, relative to the various grades of radiological sesamoid appearance.ObjectiveTo examine the existence of concurrent radiological and ultrasonographical findings in individual sesamoid-branch units in sales horses; to determine whether there are any radiological findings that are consistently accompanied by a particular degree of insertional branch change, and to provide practical recommendations as to when suspensory branch ultrasonography may be warranted in a sales environment.Study designProspective cohort study using an enrolled sample.MethodsHorses were enrolled with consignor permission from a large Thoroughbred yearling sale and five 2-year-old Thoroughbred sales the following year. Data from the radiological evaluation of forelimb sesamoids and the ultrasonographical examination of the adjacent forelimb suspensory branches were described.ResultsA total of 2204 yearling forelimb sesamoid-branch units and 1336 2-year-old forelimb sesamoid-branch units were included, from 551 sales yearlings and 334 sales 2-year-olds. The proportion of yearling sesamoids with grade <= 1 vascular channels that had adjacent grade >= 2 fibrillar branch change was 1.2%. The same proportion for 2-year-olds was 3.8%, with medial forelimb sesamoids with grade 1 vascular channels overrepresented in 2-year-olds in this category. In yearlings, 31% of sesamoids with grade 2 vascular channels had adjacent grade >= 2 fibrillar branch change and 59% of sesamoids with grade 3 vascular channels had adjacent grade >= 2 fibrillar branch change. In 2-year-olds, 47% of sesamoids with grade 2 vascular channels had adjacent grade >= 2 fibrillar branch change and 67% of sesamoids with grade 3 vascular channels had the same. Only one yearling sesamoid and one 2-year-old sesamoid with radiological abaxial concavity had grade >= 2 fibrillar branch change.Main limitationsHindlimbs were not included. Clinical examinations were not performed and the status of any past or present inflammatory process at the sesamoid-branch enthesis could not be inferred from radiographs and ultrasonographic images alone.ConclusionsThe existence and prevalence of concurrent radiological and ultrasonographical findings in the proximal sesamoid bones and adjacent suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses has been established. General recommendations have been made for selective branch ultrasonography on the basis of radiological sesamoid appearance. The results support a separate aetiology for radiological sesamoid abaxial concavity that does not primarily involve the suspensory branch insertion. HintergrundVerä nderungen der proximalen Sesambeine (Gleichbeine) und des Ansatzes der angrenzenden Fesselträ gerschenkel (Schenkel) sind bei jungen Vollblü tern, die auf ö ffentlichen Auktionen verkauft werden, von besonderer Bedeutung. Ü ber die Prä valenz gleichzeitiger ultrasonographischer Schenkelverä nderungen im Verhä ltnis zu den verschiedenen Graden des radiologischen Gleichbein-Aussehens ist wenig bekannt.ZieleUntersuchung des Vorhandenseins gleichzeitiger radiologischer und ultrasonographischer Befunde in einzelnen Gleichbein-Schenkeleinheiten bei Verkaufspferden; festzustellen, ob es radiologische Befunde gibt, die durchgä ngig mit einem bestimmten Grad der Verä nderung der Insertionsä ste einhergehen, und praktische Empfehlungen zu geben, wann eine Ultraschalluntersuchung der Fesselträ gerschenkel in einer Verkaufsumgebung gerechtfertigt sein kann.StudiendesignProspektive Kohortenstudie mit einer rekrutierten Stichprobe.MethodenDie Pferde wurden mit Erlaubnis des Verkä ufers aus einer gro ss en Vollblut-Jä hrlingsversteigerung und fü nf 2-jä hrigen Vollblutversteigerungen im folgenden Jahr erfasst. Die Daten aus der radiologischen Beurteilung der Gleichbeine der Vordergliedma ss en und der ultrasonographischen Untersuchung der angrenzenden Fesselträ gerschenkel der Vordergliedma ss en wurden mittels deskriptiver Statistik ausgewertet.ErgebnisseInsgesamt wurden 2.204 Gleichbein-Schenkeleinheiten von Jä hrlingen und 1.336 Gleichbein-Schenkeleinheiten von 2-Jä hrigen aus 551 verkauften Jä hrlingen und 334 verkauften 2-Jä hrigen untersucht. Der Anteil der Gleichbeine von Jä hrlingen mit Gefäss kanä len des Grades <= 1, die angrenzende fibrillä re Schenkelverä nderungen des Grades >= 2 aufwiesen, betrug 1,2%. Bei den 2-Jä hrigen betrug der gleiche Anteil 3,8%, wobei die medialen Gleichbeine der Vordergliedma ss en mit Gefäss kanä len des Grades 1 bei den 2-Jä hrigen ü berreprä sentiert waren. Bei Jä hrlingen wiesen 31% der Gleichbeine mit Gefäss kanä len des Grades >= 2 wiesen fibrillä re Schenkelverä nderungen des Grades >= 2 auf und 59% der Gleichbeine mit Gefäss kanä len des Grades 3 wiesen fibrillä re Schenkelverä nderungen des Grades >= 2 auf. Bei den 2-Jä hrigen wiesen 47% der Gleichbeine mit Gefäss kanä len des Grades 2 und 67% der Gleichbeine mit Gefäss kanä len des Grades 3 die gleichen Grad >= 2 fibrillä ren Verä nderungen auf. Das Gleichbein von nur einem Jä hrling und einem 2-jä hrigen mit radiologischer abaxialer Konkavitä t wies fibrillä re Schenkelverä nderungen vom Grad >= 2 auf.HauptlimitationenHinterbeine wurden nicht untersucht. Klinische Untersuchungen wurden nicht durchgefü hrt und der Status eines frü heren oder aktuellen Entzü ndungsprozesses an der Gleichbein-Schenkel-Enthese konnte nicht allein aus Rö ntgen- und Ultraschallbildern abgeleitet werden.Schlu ss folgerungenDas Vorhandensein und die Prä valenz von gleichzeitigen radiologischen und ultrasonographischen Befunden in den Gleichbeinen und der angrenzenden Fesselträ gerschenkel wurde bei einjä hrigen und zweijä hrigen Vollblutpferden untersucht. Es wurden allgemeine Empfehlungen fü r eine selektive Schenkelsonographie auf der Grundlage des radiologischen Erscheinungsbildes der Gleichbeine ausgesprochen. Die Ergebnisse sprechen fü r eine separate Ä tiologie fü r die radiologische abaxiale Sesambeinkonkavitä t, die nicht primä r den Ansatz des Fesselträ gerschenkels betrifft.

BACKGROUND Subchondral lucencies (SCLs) in the distal aspect of the medial femoral condyle (MFC) of young Thoroughbred horses are a source of controversy on presale radiographs. There is limited scientific evidence regarding the risk of progression and impact on future racing performance. OBJECTIVES To (1) identify the prevalence of MFC SCLs on sales repository radiographs in yearling and 2-year-old Thoroughbreds; (2) identify any association between grade of MFC SCL and future racing performance and (3) monitor changes in MFC SCL grades between yearling and 2-year-old sales. STUDY DESIGN Prospective cohort study. METHODS Radiographs were obtained with consignor permission from a 2016 yearling sale and five 2017 2-year-old sales. Stifle radiographs were evaluated and MFC SCLs graded on a scale of 0-3. Axial MFC lucencies were recorded separately. Maximum MFC grades per horse were analysed for associations with racing performance outcomes, adjusted for sex, to the end of the horses' 4-year-old racing year. Analysis was via logistic, negative binomial or linear regression as appropriate, with the threshold for significance set at α = 0.05. RESULTS Radiographs from 2508 yearlings (5016 stifles) and 436 2-year-olds (872 stifles) were included in the study. MFC SCLs of grades 1-3 were observed in 242 (9.65%) yearlings and 49 (11.2%) 2-year-olds. Bilateral MFC SCLs of grades 1-3 were observed in 54 (2.2%) yearlings and 12 (2.8%) 2-year-olds. Grade 1 MFC SCLs in yearlings either remained unchanged (14/31), progressed to a grade 2 (6/31) or resolved (11/31) by the 2-year-old sale. Grade 2 MFC SCLs in yearlings remained unchanged (6/10), progressed to a grade 3 (2/10) or improved to a grade 1 (2/10). Yearlings with a grade 3 MFC SCL had a 78% probability of starting a race (95% confidence interval [CI] 58.2-89.6%), compared with an 84% probability of racing for grade 0 yearlings (95% CI 82.7-85.8%). Six of the seven yearlings with axial MFC lucencies raced. MAIN LIMITATIONS This study may underestimate the prevalence of severe lesions in the general yearling population of U.S. Thoroughbreds. However, the convenience sample used is representative of the population of interest at sales. The study design could not address exclusions prior to sale. CONCLUSIONS Grade 1 MFC SCLs are the most common type seen in yearling and 2-year-old sales horses. The majority of yearling grade 1 MFC SCLs resolved or remained static by 2-year-old sales. It was also possible for grade 2 and 3 MFC SCLs to improve one grade between sales. Fewer sales yearlings with a grade 3 MFC SCL raced, but in those that did race there was no evidence of worse performance compared to unaffected peers. Axial MFC lucencies did not affect racing performance.

We report the relationships between linear vs. network polymer architecture and biomechanical outcomes including lubrication and cushioning when the polymers are applied to the surface of articulating knee cartilage. Aqueous formulations of the bioinspired polymer poly(2-methacryloyloxylethyl phosphorylcholine) (pMPC) exhibit tuneable rheological properties, with network pMPC exhibiting increased elasticity and viscosity compared to linear pMPC. Application of a polymer network, compared to a linear one, to articulating tissue surfaces reduces friction, lessens tissue strain, minimizes wear, and protects tissue - thereby improving overall tissue performance. Administration of the network pMPC to the middle carpal joint of skeletally mature horses elicits a safe response similar to saline as monitored over a 70 day period.

Bisphosphonates are a group of drugs that can reduce bone resorption by incorporating into the crystal structure of exposed hydroxyapatite where they are taken up by osteoclasts. Bisphosphonates have several other mechanisms of action including reducing pain and inflammation and altering macrophage function. There are two types of bisphosphonates-nitrogenous and non-nitrogenous, the latter of which is used in horses. This article provides a literature-based review of the proposed mechanisms of action and therapeutic uses of bisphosphonates including a brief review of bone response to disease. A review of the literature available in horses including safety data and current rules and regulations is also provided.Published by Elsevier Inc.

OBJECTIVETo perform a pilot study with the intent of assessing the feasibility of a modified subchondroplasty (mSCP) technique in a validated preclinical equine model of full-thickness articular cartilage loss and evaluate the short-term patient response to the injected materials.ANIMALS3 adult horses.PROCEDURESTwo 15-mm-diameter full-thickness cartilage defects were created on the medial trochlear ridge of each femur. Defects were treated with microfracture and then filled by 1 of 4 techniques: (1) autologous fibrin graft (FG) via subchondral injection of fibrin glue (FG), (2) autologous fibrin graft via direct injection of FG, (3) subchondral injection of a calcium phosphate bone substitute material (BSM) with direct injection of FG, and (4) untreated control. Horses were euthanized after 2 weeks. Patient response was evaluated via serial lameness examination, radiography, magnetic resonance imaging, computed tomography, gross evaluation, microcomputed tomography, and histopathology.RESULTSAll treatments were successfully administered. The injected material perfused through the underlying bone into the respective defects without adversely affecting the surrounding bone and articular cartilage. Increased new bone formation was seen at the margins of the trabecular spaces containing BSM. There was no treatment effect on the amount or composition of tissue within defects.CLINICAL RELEVANCEThe mSCP technique was a simple, well-tolerated technique in this equine articular cartilage defect model without significant adverse effects to host tissues after 2 weeks. Larger studies with long-term follow-ups are warranted.

Cone-beam computed tomography (CBCT) is an emerging modality for imaging of the equine patient. The objective of this prospective, descriptive, exploratory study was to assess visualization tasks using CBCT compared with conventional fan-beam CT (FBCT) for imaging of the metacarpophalangeal joint in equine cadavers. Satisfaction scores were numerically excellent with both CBCT and FBCT for bone evaluation, and FBCT was numerically superior for soft tissue evaluation. Preference tests indicated FBCT was numerically superior for soft tissue evaluation, while preference test scoring for bone was observer-dependent. Findings from this study can be used as background for future studies evaluating CBCT image quality in live horses.

OBJECTIVE:The aim of this study was to assess screw placement in simulated dorsomedial-plantarolateral central tarsal bone (CTB) fractures using two imaging guidance techniques - computed tomography (CT) with fluoroscopy compared to digital radiography alone (DR). STUDY DESIGN:Experimental study. SAMPLE POPULATION:Equine cadaver hindlimbs (n = 10 pairs). METHODS:One tarsus per pair was randomly assigned to have a 4.5 mm cortical screw placed across the CTB using CT and fluoroscopy (CT/F group) or digital radiography alone (DR group). Postoperative CT was performed on all limbs. Variables related to marker placement, procedure time, and screw positioning were recorded and compared using a paired t-test for dependent means (p < .05). RESULTS:Time for marker placement was longer for the CT/F group (p = .001), with no difference in total procedure time (p = .12). CT/F was not superior to radiography alone (p > .05) for parameters related to screw positioning. Based on the 95% CI, there was greater range in relative screw length using radiography (76.5%-91.2%) versus CT/F (78.4%-84.0%). CONCLUSION:Internal fixation of CTB fractures can be successfully performed using either technique for imaging guidance. CT and fluoroscopy did not result in faster or more accurate screw placement compared to radiographs alone, except in determining screw length. CLINICAL SIGNIFICANCE:Mild adjustments in fluoroscopic or radiographic angle appeared to be a point of variability in the perception of screw placement. While CT is recommended for improved understanding of fracture configuration and surgical planning, radiographic guidance may be a suitable alternative for internal fixation of dorsomedial-plantarolateral fractures.

Introduction: Perineural analgesia is an important tool in diagnosing equine lameness. This study compared the ability of four distal limb diagnostic nerve blocks to resolve synovitis-induced lameness of the equine metacarpophalangeal joint (MCPJ).

OBJECTIVETo evaluate bone mineral content patterns between fracture configurations using novel CT image analysis.ANIMALSCT images from 97 Thoroughbred racehorses with third metacarpal/tarsal condyle fractures provide the case population for analysis.PROCEDURESFractures 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.RESULTSAnalysis 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.CLINICAL RELEVANCEDifferences 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.