Changes in Achilles tendon stiffness in gout measured by elastography – a preliminary study

Background: In addition to acute attacks of severe joint pain and swelling, chronic gout has been 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 elastography is a non-invasive method of quantifying these changes in tendon stiffness and elastography findings have not previously been reported in individuals with gout. Objective: To determine differences in Achilles tendon stiffness in people with chronic gout compared to controls (non gout) Methods: A cross sectional study comparing people with gout according to 2015 ACR/EULAR criteria and 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. Previously validated protocols for conventional US imaging [1] and shear wave elastography [2] were used. Prior to data collection, intra-observer error was good (ICC (2) 0.69 (95%CI 0.62-0.89)). Ten elastography measures were taken along a longitudinal section of the mid-point of the Achilles tendon bilaterally. Data were summarised using descriptive statistics and a repeated measures ANCOVA was used to compare elastography outcomes between the two groups for the left and right foot separately after accounting for Body Mass Index (BMI)Results A total of 14 people with gout and 13 age/sex matched control subjects participated. Table 1 displays clinical and demographic data. A small proportion of those with gout presented with intra-tendon aggregates and/or intra-tendon tophi in one or both tendons n=7 (27%) for both). There was no significant difference in tendon thickness between groups, neo-vascularity was present in n=3 (21%) gout participants. Elastography findings (table 2) demonstrated significantly reduced tendon stiffness in those with gout compared to controls. Table 1 Clinical & demographic characteristics Gout Non gout Male:Female11:311:2Mean age (SD)71.9 (10.54)71 (10.8)Mean BMI (SD)30.8 (5)27.8 (4.54)Mean duration gout years (SD)12.7 (9.88)-Comorbidities (%)DiabetesHypertensionDyslipiaemiaCardiac diseaseChronic Kidney disease5085645736627070238Gout management n (%)NoneNSAID (prn)AllopurinolCholchinePrednisolone3 (9)2 (7)6 (21)1 (3)2 (7)Table 2 Elastography findings (using marginal mean results and adjusted for BMI)Gout ControlDifference(95% CI)P valueElastography Right Achilles m/sMean (±SD)8.38(1.94)9.70(0.27)1.625(0.55-2.699)0.005Elastography Left Achilles m/sMean (±SD)8.73(1.67)9.63Conclusion Subjects with chronic gout show reduced Achilles tendon stiffness compared to controls. From a clinical standpoint, our findings were similar to elastography measurements in otherwise healthy subjects with Achilles tendinopathy and who did not have gout [3]References1 Carroll M, Dalbeth N, Allen B, et al. Ultrasound Characteristics of the Achilles Tendon in Tophaceous Gout: A Comparison with Age- and Sex-matched Controls. J Rheumatol. 2017 44(10):1487-1492.2 Payne C, Watt P, Cercignani M, Webborn N. Reproducibility of shear wave elastography measures of the Achilles tendon. Skeletal Radiol. 2017 17 2846-8. 3 Payne C 2018 Clinical Applications of shear wave elastography to Achilles tendon imaging and monitoring of a rehabilitation protocol for Achilles tendonopathy PhD Thesis, University of Brighton(0.66)1.214(0.23-2.198)0.018