Differences in Achilles tendon stiffness in people with gout.

Abstract Background Chronic gout is associated with weaker foot/leg muscles, altered gait patterns and on-going foot pain. Inflammation associated with gout may change tissue elasticity and ultrasound imaging (US) utilising shear wave elastography (SWE) offers a non-invasive method of quantifying these changes in tendon stiffness and SWE findings have not previously been reported in individuals with gout. We sought to determine differences in Achilles tendon stiffness in people with chronic gout compared to controls (non-gout). Methods A cross sectional study comparing 24 people with gout and 26 age/sex-matched controls. Clinical and demographic data were collated and US imaging used to determine tendon thickness, presence of gouty tophi and/or aggregates and levels of angiogenesis. Ten shear wave elastography (SWE) measures were taken along a longitudinal section of the mid-point of the Achilles tendon bilaterally. Prior to data collection, intra-observer error was good (0.75). Data were summarised using descriptive statistics and a repeated measures ANCOVA was used to compare SWE measures between the two groups for the left and right foot separately after accounting for Body Mass Index (BMI). Results: A small proportion of those with gout presented with intra-tendon aggregates and/or intra-tendon tophi in one or both tendons. There was no statistically significant difference in tendon thickness between groups. Neo-vascularity was present in a third of gout participants. SWE findings demonstrated significantly reduced tendon stiffness in those with gout compared to controls: right Achilles mdiff =1.04 (95% CI (0.38 to 1.7) p=0.003 and left Achilles mdiff = 0.7 (95% CI 0.09 to 1.32) p=0.025. Conclusion: Subjects with chronic gout show significantly reduced Achilles tendon stiffness compared to non-gout controls. From a clinical standpoint, our findings were similar to SWE measurements in subjects with Achilles tendinopathy and who did not have gout.