0107: Role of Achilles Elastography in Differentiating Patients with Early Psoriatic Arthritis

Background/Purpose: Elastography (EL) is an imaging technique that evaluates the biomechanical properties of tissues. Pathological tissues have different elastic properties compared to healthy tissues.

In diseases like psoriatic arthritis (PsA), tendon structure and function can be affected, leading to enthesitis, being the Achilles tendon one of the most commonly involved structures. EL allows for the evaluation of tendons´ response to mechanical strain, detecting changes in their elasticity that may indicate inflammation or structural damage. The underlying hypothesis is that Achilles tendon stiffness increases significantly after physical activity in patients with Achilles involvement, while in those without enthesitis, elasticity remains stable.

The purpose of this study is to demonstrate the utility of Achilles elastography (EL-AQ) in the diagnosis of PsA in patients with clinically referred Achilles involvement (PsA-A) or without it, compared to three types of controls.

Methods: Baseline and post-exercise EL-AQ results were compared between PsA and PsA-A patients (diagnosed < 24 months) from four rheumatology centers and three control groups: athletes, non-athletic individuals with normal weight, and overweight/obese subjects, all without known psoriatic disease. Controls were matched to patients by sex and age (±2 years). Baseline and post-exercise comparisons were performed, and correlations between these results, clinical characteristics, and MASEI scores were analyzed. EL-AQ was performed using a General Electric S8 ultrasound machine equipped with a low-frequency linear probe. Tendon stiffness was measured using shear wave elastography, averaging three 1 cm² regions of interest within the enthesis of the non-dominant Achilles tendon (controls and PsA patients) or the symptomatic tendon (PsA-A patients). The controlled exercise consisted of 20 minutes on a stationary bicycle at medium resistance with a target of 150% of the resting heart rate.

Results: A total of 57 patients (27 PsA, 30 PsA-A) and 171 controls were included. Patients’ mean age (SD) = 39.9 (6.7) years. Time since diagnosis = 12 (7) months. Baseline EL-AQ results for controls and patients were 114.6 (32.9) and 77.0 (21.6) kPa, respectively (p < 0.001). EL-AQ post-exercise gradients in controls and patients were 65.7 (28.7) and 20.0 (9.3) kPa, respectively (p < 0.001). An inverse correlation was observed between MASEI and EL-AQ post-exercise change (Pearson’s coefficient -0.445; p < 0.001). Among patients, baseline EL-AQ was 70.1 (21.0) in the PsA-A group and 84.7 (19.9) kPa in the PsA group (p < 0.05); EL-AQ post-exercise gradient was 15.9 (7.2) in the PsA-A group and 24.5 (9.4) kPa in the PsA group (p < 0.001).

Conclusion: Baseline EL-AQ demonstrates discriminatory diagnostic capacity between PsA patients with or without clinical Achilles involvement and healthy controls. Adaptive ability to physical exercise, analyzed via post-exercise EL-AQ gradient, also demonstrated strong discriminatory capacity between patients and control subgroups. EL-AQ should be considered a test of interest for evaluating patients suspected of having PsA with or without Achilles involvement.