Ultrasonography of the suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression of findings and associations with racing performance.

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.

Concurrent radiological and ultrasonographical findings in the forelimb proximal sesamoid bones and adjacent suspensory ligament branches in yearling and 2-year-old Thoroughbred sales horses.

BACKGROUND: Changes 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. OBJECTIVE: To 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 DESIGN: Prospective cohort study using an enrolled sample. METHODS: Horses 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. RESULTS: A 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 LIMITATIONS: Hindlimbs 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. CONCLUSIONS: The 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.

Radiological findings in the proximal sesamoid bones of yearling and 2-year-old Thoroughbred sales horses: Prevalence, progression and associations with racing performance.

BACKGROUND: Radiological 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. OBJECTIVES: To 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 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. 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. RESULTS: A 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 LIMITATIONS: These findings are applicable to horses presented for sale at public auction and may underestimate the prevalence of severe lesions in non-sales horses. CONCLUSIONS: Grade 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.

In Vitro Effects of High-Intensity Laser Photobiomodulation on Equine Bone Marrow-Derived Mesenchymal Stem Cell Viability and Cytokine Expression.

OBJECTIVE: This study aimed to examine the influence of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation on equine bone marrow-derived mesenchymal stem cell (MSC) viability, proliferation, and cytokine expression in vitro. BACKGROUND: Photobiomodulation of cells using monochromatic light is a technique designed to influence cellular processes. Previous studies have shown dose-dependent effects of low-level laser irradiation on cell proliferation and cytokine expression in a range of cell types and species. Evidence for the influence of 1064 nm wavelength near-infrared irradiation on MSCs is sparse, and high-energy doses have shown inhibitory effects. METHODS: MSC cultures from six horses were exposed to 1064 nm irradiation with an energy density of 9.77 J/cm2 and a mean output power of 13.0 W for 10 sec. MSC viability and proliferation were evaluated through flow cytometry and real-time live cell analysis. Gene expression and cytokine production in the first 24 h after irradiation were analyzed through polymerase chain reaction (PCR), multiplex assay, and enzyme-linked immunosorbent assay. RESULTS: No difference in viability was detected between irradiated and control MSCs. Irradiated cells demonstrated slightly lower proliferation rates, but remained within 3.5% confluence of control cells. Twenty-four hours after irradiation, irradiated MSCs demonstrated a significant increase in expression of interleukin (IL)-10 and vascular endothelial growth factor (VEGF) compared with control MSCs. CONCLUSIONS: Under these irradiation parameters, equine MSCs remained viable and expressed increased concentrations of IL-10 and VEGF. IL-10 has an anti-inflammatory action by inhibiting the synthesis of proinflammatory cytokines at the transcriptional level. This response to 1064 nm irradiation shows promise in the photobiomodulation of MSCs to enhance their therapeutic properties.

Musculoskeletal Pathology.

The current understanding of pathology as it relates to common diseases of the equine musculoskeletal system is reviewed. Conditions are organized under the fundamental categories of developmental, exercise-induced, infectious, and miscellaneous pathology. The overview of developmental pathology incorporates the new classification system of juvenile osteochondral conditions. Discussion of exercise-induced pathology emphasizes increased understanding of the contribution of cumulative microdamage caused by repetitive cyclic loading. Miscellaneous musculoskeletal pathology focuses on laminitis, which current knowledge indicates should be regarded as a clinical syndrome with a variety of possible distinct mechanisms of structural failure that are outlined in this overview.