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Background: Agreement between experienced observers for assessment of pathology and assessment confidence are poorly documented for magnetic resonance imaging (MRI) of the equine foot., Objectives: To report interobserver agreement for pathology assessment and observer confidence for key anatomical structures of the equine foot during MRI., Study Design: Exploratory clinical study., Methods: Ten experienced observers (diploma or associate level) assessed 15 equine foot MRI studies acquired from clinical databases of 3 MRI systems. Observers graded pathology in seven key anatomical structures (Grade 1: no pathology, Grade 2: mild pathology, Grade 3: moderate pathology, Grade 4: severe pathology) and provided a grade for their confidence for each pathology assessment (Grade 1: high confidence, Grade 2: moderate confidence, Grade 3: limited confidence, Grade 4: no confidence). Interobserver agreement for the presence/absence of pathology and agreement for individual grades of pathology were assessed with Fleiss' kappa (k). Overall interobserver agreement for pathology was determined using Fleiss' kappa and Kendall's coefficient of concordance (KCC). The distribution of grading was also visualised with bubble charts., Results: Interobserver agreement for the presence/absence of pathology of individual anatomical structures was poor-to-fair, except for the navicular bone which had moderate agreement (k = 0.52). Relative agreement for pathology grading (accounting for the ranking of grades) ranged from KCC = 0.19 for the distal interphalangeal joint to KCC = 0.70 for the navicular bone. Agreement was generally greatest at the extremes of pathology. Observer confidence in pathology assessment was generally moderate to high., Main Limitations: Distribution of pathology varied between anatomical structures due to random selection of clinical MRI studies. Observers had most experience with low-field MRI., Conclusions: Even with experienced observers, there can be notable variation in the perceived severity of foot pathology on MRI for individual cases, which could be important in a clinical context., (© 2024 EVJ Ltd.)

Background: Investigation of image quality in clinical equine magnetic resonance (MR) imaging may optimise diagnostic value., Objectives: To assess the influence of field strength and anaesthesia on image quality in MR imaging of the equine foot in a clinical context., Study Design: Analytical clinical study., Methods: Fifteen equine foot studies (five studies per system) were randomly selected from the clinical databases of three MR imaging systems: low-field standing (LF St), low-field anaesthetised (LF GA) and high-field anaesthetised (HF GA). Ten experienced observers graded image quality for entire studies and seven clinically important anatomical structures within the foot (briefly, grade 1: textbook quality, grade 2: high diagnostic quality, grade 3: satisfactory diagnostic quality, grade 4: non-diagnostic). Statistical analysis assessed the effect of anaesthesia and field strength using a combination of the Pearson chi-square test or Fisher's exact test and Mann-Whitney test., Results: There was no difference in the proportion of entire studies of diagnostic quality between LF St (90%, 95% CI 78%-97%) and LF GA (88%, 76-95%, P = .7). No differences were evident in the proportion of diagnostic studies or median image quality gradings between LF St and LF GA when assessing individual anatomical structures (both groups all median grades = 3). There was a statistically significant difference in the proportion of entire studies of diagnostic quality between LF GA and HF GA (100%, 95% CI lower bound 94%, P = .03). There were statistically significant differences in median image quality gradings between LF GA (all median grades = 3) and HF GA (median grades = 1 (5/7 structures) or 2 (2/7 structures) for all individual anatomical structures (all P < .001). The reasons reported for reduced image quality differed between systems., Main Limitations: Randomised selection of cases from clinical databases. Individual observer preferences may influence image quality assessment., Conclusions: Field strength is a more important influencer of image quality than anaesthesia for magnetic resonance imaging of the equine foot in clinical patients., (© 2020 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.)

Background: Synovial sepsis of unknown origin is a rare cause of lameness in the adult horse, and a haematogenous pathogenesis has been proposed in previous cases., Objectives: To describe the features and outcome of synovial sepsis of unknown origin in adult Thoroughbred racehorses., Study Design: Retrospective case series., Methods: Hospital records for admissions between 2005 and 2015 were reviewed to identify adult horses diagnosed with synovial sepsis of unknown origin. Presentation, clinicopathological, microbiological and diagnostic imaging findings were recorded. Treatment methods, surgical findings, complications and long-term outcome were evaluated., Results: Eleven cases were identified over the study period. Diagnosis was established from clinical examination and clinicopathologic findings, which were comparable to other aetiologies of synovial sepsis. Affected structures included synovial joints, tendon sheaths and bursae. Concurrent osteochondritis dissecans or articular cartilage lesions were evident during arthroscopic surgery in three cases. Significant intrasynovial haemorrhage was not identified. Microbial culture of synovial fluid or synovial biopsy was positive in 6/11 of cases, with all isolates being Gram-positive cocci. Of the 6 positive microbial cultures, all isolates demonstrated in vitro sensitivity to a cephalosporin antimicrobial agent. A concurrent remote wound was present in a single case. No other potential origins of bacteraemia were identified. Treatment methods included endoscopic surgery, standing multineedle lavage, intravenous regional limb perfusion, intrasynovial medication and/or systemic antimicrobial administration. All horses survived to hospital discharge. For the 6/11 cases that raced following synovial sepsis, the median period for return to racing was 221 days., Main Limitations: A small study population, which was retrospectively reviewed., Conclusions: Synovial sepsis of unknown origin is rare in the adult Thoroughbred racehorse and can affect a range of synovial structures. A concurrent potential source of bacteraemia is rarely identified. With appropriate management, the prognosis to return to racing is fair., (© 2019 EVJ Ltd.)