Impaired mechanical properties of Achilles tendon in spastic stroke survivors: an observational study.

Background: The spasticity could lead to decreased functional capacity and changes in musculoskeletal tissue.

Objective: To compare the Achilles tendon properties between the affected and contralateral limbs of participants with spasticity due to stroke and the healthy subjects.

Methods: Fifteen individuals with ankle spasticity due to stroke and 15 healthy subjects were recruited. Maximal isometric ankle joint torque was obtained with an isokinetic dynamometer, and an ultrasound was used to determine tendon length, tendon cross-sectional area, and the medial gastrocnemius myotendinous junction displacement. The Achilles tendon strength, displacement, stress, strain, stiffness, and Young's modulus were obtained during a maximum voluntary isometric plantarflexion contraction.

Results: There were no differences between Achilles tendon length among participants. Both limbs of participants with stroke showed reduced tendon cross-sectional area (~18%) compared to healthy limb. The affected limb showed decreased tendon strength (686 ± 293.3 N), displacement (10.6 ± 1.7 mm), Young's modulus values (849 ± 235.6 MPa), and lower stiffness (196.6 ± 67.6 N/mm) compared to the contralateral limb (strength, 1357.1 ± 294.8 N; displacement, 15.2 ± 5.5 mm; Young's modulus, 1431.8 ± 301.9 MPa; stiffness, 337.5 ± 98.1 N/mm) and to the healthy limb. The contralateral limb also showed decreased tendon strength (~26.2%) and stiffness (~21.5%) compared to the healthy group.

Conclusion: There is a decrement in Achilles tendon morphological and mechanical properties of the affected limb in individuals with spasticity due to stroke. The contralateral limb had a thinner tendon more compliant likely to physical activity reduction.