Real-time sonoelastography of Achilles tendon in patients with ankylosing spondylitis

Real-time sonoelastography (SE) is a new ultrasound-based imaging technique that provides information on tissue elasticity and stiffness. We determined the efficacy of SE for assessing Achilles tendon abnormalities in patients with ankylosing spondylitis (AS).

Forty-one consecutive AS patients and 32 asymptomatic healthy subjects were enrolled. Achillodynia was scored on a 0- to 100-mm visual analog scale. A high-resolution ultrasound machine equipped with an elastography-compatible linear probe was used to perform bilateral B-mode ultrasound, Doppler ultrasound, and SE examinations of Achilles tendons. Tendons were divided into proximal, middle, and distal segments. B-mode examinations included tendon thicknesses, echotextures, and enthesopathic findings. SE using color-coded images was performed in the same areas. Normal consistent tendon structures were coded as blue or green, and moderately (yellow) or severely (red) softened areas were considered pathological.

The distal third of the Achilles tendons was the most commonly affected part in the AS patients compared with healthy subjects (p = 0.001), whose middle third was more commonly affected. Achillodynia intensity tended to be higher in patients with pathological B-mode or SE examination findings (p = 0.09 and p = 0.07 respectively). Softening detected by SE in the distal third was associated with enthesopathy findings such as calcaneal bone erosions (Fisher's X (2), p = 0.07) and tendinous enlargement (Fisher's X (2), p = 0.001). B-mode and SE findings had moderate to good correlation in the assessment of Achilles tendon abnormalities.

Sonoelastography may be useful for the evaluation of tendon abnormalities in patients with AS; in addition; it may be useful for the evaluation of other inflammatory rheumatic conditions.