New applications of sonoelastography in rheumatology: where are we now?

REAL-TIME strain elastography: Applications in musculoskeletal system

BACKGROUND

Strain or compression sonoelastography (CE) provides a colour-coded elastogram representing tissue elasticity by measuring tissue deformability after repeated probe compression. Elastographic ultrasound (EUS) is a valuable tool for screening diagnosis and follow-up of inflammatory, degenerative, benign and malignant neoplastic pathologies of skin, subcutaneous tissue, muscles, tendons, ligaments, fascia and nerves; help in targeted biopsy; monitor healing tendons after surgery or nerve stiffness changes during physiotherapy.

OBJECTIVES

To assess stiffness of normal tendons, muscles and nerve. To diagnose cellulitis, fasciitis, abscess, tendinopathy, myositis, muscle/tendon rupture/contusion and differentiate between benign and malignant soft tissue tumours. To derive elastic score (ES) and strain ratio (SR) in cases and controls. To correlate B-mode findings with CE.

MATERIALS AND METHODS

A prospective study on 50 healthy subjects between 25 and 30 years and 50 cases of diffuse and focal musculoskeletal pathologies was done using B-mode and CE over 2 years. Statistical analysis of distribution, mean, associations, sensitivity, specificity, area under Receiver Operating Characteristic curve (AUROC) for B-mode, ES, SR combined B-mode/CE and their comparison was done.

RESULTS

Significant association was noted between SR in muscles and tendons with sex. Significant correlation was noted between ES/SR with B-mode. CE and B-mode had 100% and 52.4% sensitivity respectively for diagnosing diffuse pathologies. For differentiating benign and malignant masses sensitivity, specificity, and diagnostic accuracy of B-mode was 71.43%, 86.36% and 82.76%; of SR was 71.43%, 90.91% and 86.21%; of Combined B-mode with CE was 100%, 90.91% and 93.1% respectively. Elastographic pattern had highest diagnostic accuracy and largest AUROC.

CONCLUSION

CE as a screening test had higher diagnostic accuracy, supporting need for standardizing it for clinical use in MSK. EUS being a widely available, fast and affordable modality, can aid follow up of chronic MSK pathologies, response to medication, physiotherapy and surgery and mitigate the need for MRI.

Differences in Achilles tendon stiffness in people with gout: a pilot study

Background

Gout has been associated with weaker foot/leg muscles and altered gait patterns. There is also evidence of on-going foot pain and an increased risk of tendinopathy, with the Achilles and patella tendons most frequently affected in gout. Additionally, the inflammation associated with gout may change tissue elasticity. Ultrasound imaging utilising shear wave elastography (SWE) offers a non-invasive method of quantifying changes in tendon stiffness. SWE findings have not previously been reported in individuals with gout. We sought to determine differences in Achilles tendon stiffness in people with 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 the centre of a longitudinal section of the mid-portion of each Achilles tendon. Prior to data collection, intra-observer error was good (>0.69). 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 m/s (95% CI (0.38 to 1.7) p = 0.003 and left Achilles mdiff = 0.7 m/s (95% CI 0.09 to 1.32) p = 0.025. No relationship between the presence of tophi and SWE values were detected.

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.