Systemic absorption of triamcinolone acetonide is increased from intrasynovial versus extrasynovial sites and induces hyperglycemia, hyperinsulinemia, and suppression of the hypothalamic-pituitary-adrenal axis.

Steroid-associated laminitis remains a major concern with use of corticosteroids in horses. Individual case factors such as joint pathology, pre-existing endocrinopathies, or corticosteroid type, dose, and timing influencing steroid-induced laminitis risk have not been investigated. This study aimed to determine if systemic absorption of triamcinolone acetonide (TA) varies between intrasynovial (antebrachiocarpal) and extrasynovial (sacroiliac) injection sites, and to determine the effects of TA absorption on glucose, insulin, cortisol, and adrenocorticotropic hormone (ACTH). Twenty adult horses were randomized into antebrachiocarpal or sacroiliac joint injection groups, and each horse received bilateral injections with a total dose of 18 mg triamcinolone. Blood was collected prior to injection and at 1, 2, 4, 6, 8, 10, 12, 16, 20, 24, 36, 48, 60, and 72 h post-injection. Peak TA absorption occurred at 8 h in both groups, and was significantly higher in the intrasynovial group compared to the extrasynovial group (1.397 ng/mL, 0.672 ng/mL, p < 0.05). Plasma TA levels were significantly higher in the intrasynovial group from 8 to 36 h post-injection (p < 0.05). There was no difference in glucose, insulin, cortisol, or ACTH between groups at any time point. Insulin and glucose were significantly increased from baseline at all timepoints from 10-72 h and 1-72 h post-injection, respectively. Horses with elevated baseline insulin values (>20 µU/mL) from both groups experienced a more marked hyperinsulinemia, reaching a mean peak insulin of 197.5 µU/mL as compared to 90.06 µU/mL in those with normal baseline insulin. Cortisol and ACTH were significantly decreased from baseline at timepoints from 4-72 h post-injection in both groups. This study is the first to evaluate drug absorption from the sacroiliac site and demonstrates that drug absorption varies between intrasynovial and extrasynovial injection sites. TA absorption causes metabolic derangements, most notably a marked hyperinsulinemia that is more severe in horses with elevated baseline insulin values. The influence of baseline endocrinopathies on response to corticosteroid administration as well as the effect of corticosteroid-induced metabolic derangements warrant further investigation as risk factors for corticosteroid-associated laminitis.

No correlation found between palpation and ultrasound for evaluation of effusion in the medial femorotibial and femoropatellar joint compartments of horses.

OBJECTIVE: To compare palpation and ultrasound scores of effusion of the medial femorotibial and femoropatellar joints of horses. ANIMALS: 40 horses (80 stifles) were evaluated over a 12-week period. METHODS: Horses > 1 year of age without history of stifle disease were enrolled from September to December 2022. Palpation of right and left medial femorotibial and femoropatellar joint compartments was performed. Amount of effusion was scored by a board-certified large animal surgeon, a third-year large animal surgery resident, and an equine sports medicine intern. Effusion of right and left medial femorotibial and femoropatellar joints was quantified with ultrasound by a board-certified equine sports medicine and rehabilitation clinician. Amount of effusion on palpation and ultrasound was graded as none-mild (1), moderate (2), or severe (3). A 2-way intraclass correlation coefficient evaluated interrater reliability of palpation scores. The Spearman rank correlation determined association between palpation and ultrasound scores. RESULTS: Interrater reliability for palpation of effusion was poor between all observers for all joint compartments. No significant correlation was identified between palpation and ultrasound scores for any joint compartment for any observer. CLINICAL RELEVANCE: Clinicians often rely on palpation of joint effusion as an indication of stifle pathology. We found interrater reliability to be poor for palpation scores, indicating low agreement for palpation of joint effusion between clinicians within our group. No correlation was found between palpation and ultrasound scores for joint effusion, indicating that clinicians should not rely on palpation alone to quantify joint effusion of the medial femorotibial and femoropatellar joints.

Advances in Imaging Techniques to Guide Therapies and Monitor Response to the Treatment of Musculoskeletal Injuries.

Continual advancements in diagnostic imaging have allowed for more accurate and complete diagnoses of injuries in the performance horse. The use of several different imaging tools has further allowed the equine sports medicine clinician to more carefully direct treatment options, monitor response to therapy and guide rehabilitation recommendations. The advancements in diagnostic imaging and novel treatment options have led to the improvement in the overall prognosis of many injuries that affect the horse and their performance. The purpose of this section is to review the advancements made in diagnostic imaging of the horse and to aid the practitioner in the selection of the appropriate modality and how best to use them to guide treatment and monitoring decisions.

Alterations to the synovial invaginations of the navicular bone are associated with pathology of both the navicular apparatus and distal interphalangeal joint when evaluated using high field MRI.

Limited information exists regarding associations between distal interphalangeal joint (DIPJ) abnormalities and synovial invagination changes in the distal sesamoid (navicular) bone. This retrospective, analytical study aimed to measure specific characteristics of the synovial invaginations of the navicular bone to determine whether any single characteristic was associated with abnormalities in the DIPJ or navicular apparatus (NA) using high field MRI and a sample of 200 horses' feet. The DIPJ and NA were graded independently by three scorers. The grades were averaged, creating a global pathology score for the DIPJ, NA, and synovial invaginations. Higher global scores represented more severe pathology. The number of invaginations, depth of penetration, invagination shape, and cross-sectional area (CSA) of the largest invagination were recorded. Interobserver agreement was measured using Cohen's Kappa. Associations of global scores of the DIPJ and NA with individual invagination characteristics were assessed using linear mixed modeling. A significant relationship was found between the number of invaginations and global DIPJ score, with higher invagination numbers associated with higher DIPJ scores. For invagination depth and CSA, a significant relationship was noted with global scores of both the DIPJ and NA. Reliable relationships between the shape of synovial invaginations and global scores of DIPJ and NA were not found, likely due to poor interobserver scoring (0.305). These findings suggest that primary DIPJ disease and NA pathology should be considered when noticing alterations to navicular synovial invaginations on MRI. This contrasts traditional views that synovial invagination abnormalities are indicative solely of NA pathology.