Background Subchondral bone pathology is common in Thoroughbred racehorses and believed to precede more serious injury. Early identification of pathology is critical to allow for intervention. Objectives To determine interobserver variability of fetlock subchondral bone lesions using cone beam and fan beam computed tomography (CBCT, FBCT) and to validate a robotics‐controlled CBCT to identify fetlock subchondral bone pathology in the Thoroughbred racehorse. Study design Prospective cohort study. Methods FBCT and CBCT images were acquired of 25 metacarpo‐/metatarsophalangeal joints of Thoroughbred racehorses. Images were analysed for subchondral bone lesions commonly identified in Thoroughbred fetlocks by an imaging specialist and surgery specialist. Interobserver and intermodality equivalence were determined with a Pearson correlation analysis and Bland‐Altman equivalence test. Results Interobserver FBCT correlation was significant (P < .05) for 19 of 25 variables (Pearson R mean 0.77). Concordance was significant for all 25 variables (Bland Altman average difference 0.28 ± 0.21 mm). Interobserver CBCT correlation was significant for 21 of 25 variables (Pearson R mean 0.73). Concordance was significant for all variables (Bland Altman average difference 0.07 ± 1.90 mm). Intermodality (FBCT vs CBCT) correlation and concordance was significant for all variables as interpreted by the radiologist (Pearson R mean of 0.72, Bland Altman average difference 0.21 ± 0.47 mm). Intermodality correlation was significant for 19 of 25 variables as interpreted by the surgeon (Pearson R mean of 0.72). Concordance was significant for all variables (Bland Altman average difference 0.49 ± 0.52 mm). Main limitations Neither FBCT nor CBCT images were compared with other imaging modalities/histopathology; limited number of cases included; inconsistent agreement of small lesions in specific categories. Conclusions Standing CBCT is a valid diagnostic modality to identify subchondral bone lesions in Thoroughbred fetlocks. This technology may provide valuable information regarding the development and progression of fetlock pathology and yield insight into predisposing factors leading to more severe pathology.

Background Standing cone beam computed tomography (CT) provides cross‐sectional imaging of the caudal cervical articular process joints (CAPJs) in the sedated horse, though the clinical implications of osteoarthritis (OA) identified on CT in this location are unknown. Increases in concentrations of intra‐synovial cytokines could lend support to the clinical significance of CAPJ OA identified on this imaging modality. Objectives Investigate the presence and concentration of intra‐synovial inflammatory cytokines in CAPJs with and without standing cone beam CT evidence of OA using an equine specific multiplex assay. Study design Prospective clinical study. Methods Standing cone beam CT of C5‐6 and C6‐7 was performed on horses with CAPJ OA and control horses. Synovial fluid samples of the CAPJs of C5‐6 and C6‐7 were obtained bilaterally using ultrasound guidance and analysed for concentrations of IFN‐γ, IL‐1β, IL‐6, IL‐10, IL‐17 and TNFα with the Milliplex® multi‐analyte profiling kit. CT Images were retrospectively graded using a novel grading scheme. Significant differences between concentrations of inflammatory cytokines between joints with different categories of osteoarthritis severity were explored using a Wilcoxon rank‐sum test or Kruskal‐Wallis test. Results Concentrations of intra‐synovial cytokines were higher in joints with moderate to severe OA when compared to joints with no or mild OA, with differences in concentrations of IL‐17 reaching statistical significance (P = .007). Main limitations Limitations include discrepancy in number, age, and breed between control and OA populations, use of a novel grading scheme, and lack of a histologic gold‐standard to confirm the presence and severity of CAPJ OA. Conclusions Differences in inflammatory cytokines between caudal CAPJs with and without evidence of moderate to severe osteoarthritis on standing cone beam CT exist. This finding lends support to the clinical relevance of a diagnosis of moderate to severe CAPJ OA in the caudal cervical vertebral column as identified with this imaging modality.

To investigate the effects of fracture characteristics and concurrent subchondral bone pathology identified with computed tomography (CT) on the racing performance of Thoroughbred racehorses with fractures of the MC3/MT3 lateral condyle. Study design: Retrospective cohort study. Sample population: Thoroughbred racehorses (n = 50) with a fracture of the MC3/MT3 lateral condyle, which had preoperative CT and internal fixation performed.Methods: Medical records were reviewed for age, sex, limb, and surgical treatment. Computed tomography scans were evaluated to determine fracture characteristics including length, whether the fracture was incomplete or complete, and displacement. The presence of subchondral bone injury (SBI), sesamoid bone fracture, articular comminution, and fragmentation in the joint was noted. Racing data was obtained from an online database. Univariable and multivariable analyses determined associations between independent variables and outcomes. Results: Thirty-three (66%) horses raced after surgery. Horses with sesamoid bone fractures (P = .021), MC3/MT3 comminution (P = .016) and intraarticular fragmentation (P = .015) were less likely to race postoperatively. Concurrent SBI did not affect outcome. In the final multivariable model, sex (P = .015) and whether a fracture was incomplete or complete (P = .007) were the most significant predictors of racing postoperatively with females and horses with complete fractures being less likely to race. Conclusion:The prognosis for racing after a lateral condylar fracture is favorable but is decreased in horses with complete fractures and certain concurrent joint pathology. Clinical significance: Horses presenting with lateral condylar fractures commonly have concurrent joint pathology. Computed tomography can aid in

A 15-year-old Thoroughbred gelding was presented for investigation of fever, right temporomandibular region swelling, and progressive pain when opening the mouth. Right temporomandibular joint (TMJ) sepsis was diagnosed based on synovial fluid analysis, sonographic imaging, and standing robotic cone-beam computed tomography. Concurrent otitis media and temporohyoid osteoarthropathy (THO) were also noted. The horse was treated with arthroscopic debridement and lavage during standing sedation followed by local and systemic antimicrobial therapy. There were no complications associated with the surgical procedure and the gelding’s clinical signs resolved. Arthroscopy of the TMJ can be accomplished in the standing horse and should be considered when arthroscopic exploration or debridement of this joint is indicated. This is also the first case report of concurrent otitis media, TMJ sepsis, and THO; due to their close anatomic relationship, it is possible that septic otitis media could lead to pathology in the TMJ and temporohyoid joint, as described in humans.

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