Résumé :
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Because of its clinical similarities with Duchenne muscular dystrophy, the GRMD (Golden Retriever Muscular Dystrophy) model is used in pre-clinical trials to assess functional effects, notably on locomotion. Accelerometry has been validated as a reliable gait analysis tool in adult clinically stable GRMD dogs. However, therapeutic strategies are usually tested in young GRMD dogs, while both disease and growth progress.This study aimed to assess the ability of 3D-accelerometry to quantitatively monitor gait, during disease progression. Six healthy and 24 GRMD dogs underwent fortnightly tests, from the age of 2 to 9 months. Nine gait variables identified in adults were studied in puppies. A global gait quality index was also created, by calculating the distance between each individual, and a reference point, using a PCA (principal component analysis). A repeated measures ANOVA was used to investigate the effects of group (healthy vs GRMD) and of age on each variable. The ability of acccelerometry to be used during pre-clinical trials to monitor gait was assessed by evaluating 4 GRMD dogs treated with an immunosuppressive treatment associating cyclosporine and prednisolone, from the age of 2 to 9 months, and comparing them with the untreated GRMD population using an ANOVA.At the age of 2 months, the speed, stride length, and total power were significantly decreased (p<0.01), and the global index significantly increased (p=0.0002), reflecting the early gait impairment of GRMD puppies. These variables declined with age, while the others (stride frequency, relative force, regularity, relative powers in the 3 axes) became altered later, quantifying the locomotor worsening of the dogs. All the variables were able to quantify the major inter-individual heterogeneity, often described but rarely quantified in GRMD dogs. Despite the wide dispersion of the GRMD population, accelerometry was able to detect a clear locomotor benefit in the 4 immunosuppressed GRMD dogs, several variables being significantly improved (p<0.05).These results show that accelerometry can be used in growing GRMD dogs to quantify the evolution of gait and the effect of a treatment. They also show that clinical heterogeneity is a surmountable obstacle using tools able to reliably quantify affected functions, even with few individuals.
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