Characterization of the extensor digitorum communis tendon using high-frequency ultrasound shear wave elastography

Hand tendon injuries caused by various accidents are common in emergency departments. The assessment of tendon properties is crucial for evaluating the effectiveness of therapy or rehabilitation during recovery after hand injuries. Many recent studies have indicated that the shear wave velocity (SWV) of tendons is related to their stiffness. However, measurement of SWV of hand tendon is still a challenge because the small size of tendon and the limitation of existing ultrasound systems for detecting fast SWV.

We propose a high-frequency ultrasound (HFUS) elastography system using an external vibrator to measure the SWV of the extensor digitorum communis (EDC) tendon. First, animal studies were performed by measuring the SWV and stress of porcine tendons using the proposed HFUS elastography and materials testing systems respectively. In the human experiment, SWVs were measured during hand extension and flexion. The applied stress from a finger during the movements was recorded synchronously by using a load cell.

The experimental results reveal that a favorable linear correction (R² of 0.96) was obtained between tendon SWV and stress in animal studies. In the human (hand) EDC tendon experiments, the SWV increased with the extension and flexion of the hand. The SWV of the EDC tendon was in the range of 20 to 135 m/s as the applied force from the finger of a healthy human increased to 50% maximal voluntary contraction.

All the experimental results show that the proposed HFUS elastography system can be used to characterize the EDC tendon and has potential use for evaluating tendon stiffness during recovery after hand injures.