Abstract
Due to a lack of appropriate image resolution, most ultrasound scanners are unable to sensitively discern the pulley tissues. To extensively investigate the properties of the A1 pulley system and the surrounding tissues for assessing trigger finger, a 30 MHz ultrasound system was implemented to perform in vitro experiments using the hypodermis, A1 pulley, and superficial digital flexor tendon (SDFT) dissected from cadavers. Ultrasound signals were acquired from both the transverse and sagittal planes of each tissue sample. The quantitative ultrasonic parameters, including sound speed, attenuation coefficient, integrated backscatter (IB) and Nakagami parameter (m), were subsequently estimated to characterize the tissue properties. The results demonstrated that the acquired ultrasound images have high resolution and are able to sufficiently differentiate the variations of tissue textures. Moreover, the attenuation slope of the hypodermis is larger than those of the A1 pulley and SDFT. The IB of A1 pulley is about the same as that of the hypodermis, and is very different from SDFT. The m parameter of the A1 pulley is also very different from those of hypodermis and SDFT. This study demonstrated that high-frequency ultrasound images in conjunction with ultrasonic parameters are capable of characterizing the A1 pulley system and surrounding tissues.
Highlights
Pulley is a crucial tissue that extends from the head of the metacarpal bones to the base of the distal phalanges at eight specific points along the tendon sheath [1]
A1 pulley; pulley; and and (c) superficial digital flexor tendon (SDFT) acquired acquired in in Figure the sagittal plane, and those acquired in the transverse plane corresponding the corresponding to to (d)
A high frequency ultrasound system with a 30 MHz central frequency was used to apply to measure ultrasonic backscattered signals reflected from the A1 pulley, hypodermis, and SDFT in both transverse and sagittal planes
Summary
Pulley is a crucial tissue that extends from the head of the metacarpal bones to the base of the distal phalanges at eight specific points along the tendon sheath [1]. Together with the flexor tendons to close to the phalanges, the pulley tissue plays an integral role in controlling the movements of finger flexion and extension [2]. The primary function of pulley tissues is to provide a fulcrum for transferring the force of the muscle-tendon unit into rotation and torque at the finger joints [3]. The anatomic morphology of pulley tissues generally can be classified into five annular pulleys The A1, A3, and A5 pulleys are located at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints, respectively, and those of A2 and A4 pulleys are located respectively at the proximal and middle phalanx. The locations of C1, C2, and C3 are respectively within the space between the A2 and A3 pulleys, the A3 and A4 pulleys, and the distal
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