Relative motion between the flexor digitorum superficialis tendon and paratenon in zone V increases with wrist flexion angle

Abstract

Carpal tunnel syndrome is characterized by non-inflammatory fibrosis of the subsynovial connective tissue (SSCT), a paratenon-like structure inside the carpal tunnel. This pathology suggests repetitive and/or excessive shear forces are involved in injury development. We assessed relative motion between the flexor digitorum superficialis (FDS) tendon and adjacent paratenon in Zone V using colour Doppler imaging as 16 healthy participants completed three long finger movements (metacarpophalangeal joint flexion, proximal and distal interphalangeal joint flexion, full finger flexion) in three wrist postures (30˚extension, 0˚, 30˚flexion). While the type of finger movement did not affect tendon-paratenon relative motion, we found a significant main effect of wrist posture (p < 0.001). Relative displacement between the FDS tendon and paratenon (as a percentage of tendon displacement) increased from 27.2% (95%CI ¼ 24.8-29.5%) in 30˚wrist extension to 39.9% (95%CI ¼ 37.3-42.4%) in 30˚wrist flexion. Optical motion capture confirmed that wrist posture did not affect metacarpophalangeal joint range of motion (p ¼ 0.265) or proximal interphalangeal joint range of motion (p ¼ 0.582). These results indicate that relative motion increased due to paratenon strain when the wrist was flexed. While our findings agree with previous cadaveric research in wrist flexion, we found that relative displacement decreased in 30˚wrist extension (compared to 0˚). These results differ from cadaveric research, possibly due to challenges maintaining anatomic fidelity of the viscoelastic paratenon tissue in vitro. Overall, our study suggests a greater susceptibility to shear injury during repetitive finger movements, particularly when the wrist is flexed. ß

Tendon displacements during voluntary and involuntary finger movements

“…When more finger joints are free to move, tendon displacement will increase. Thus, our maximum index tendon displacement of 27 ± 4 mm for an average 120°finger joint angle is a logical extrapolation from cadaver data (Kociolek and Keir, 2016;Lopes et al, 2011). Ring finger FDS tendon displacement has not been studied before.…”

“…In various pathological conditions, the fingers and/or their tendons are affected, such as arthritis (Arauz et al, 2017), tenosynovitis and carpal tunnel syndrome (Bianchi et al, 2007;Kociolek and Keir, 2016;Korstanje et al, 2012;Singh et al, 2015;Tat et al, 2016). In patients with flexor tendon disorders, tendon displacements have been studied using ultrasound imaging (Korstanje et al, 2012).…”

A Novel Adhesion Index for Verifying the Extent of Adhesion for the Extensor Digitorum Communis in Patients with Metacarpal Fractures

“…However, because the EDC tendon is very close to the surface of the hand, it can be visually identified, making it relatively easy to locate compared to other tendons in the human body. Third, previous studies have found that joint positions, movement velocity, and single-digit motion influence the extent of relative displacement between the tendon and its surrounding tissue 21 35 36 37 . However, the preceding variables were not included in the present study for the following reasons: For joint motion, the intrinsic-plus and intrinsic-minus position were considered a safer and more stable position for patients with metacarpal fracture.…”

External Compression and Partial Ischemia Decrease Human Finger Flexor Tendon and Subsynovial Connective Tissue Relative Motion

“…The probe was positioned at the proximal wrist crease (Fig. A), in line with the area corresponding to zone V of the middle finger FDS tendon . The tendon was visually identified by its fibrillar‐striated pattern, which differs from the SSCT that appears as a thin hyperechoic band adjacent to the tendon (Fig.…”

“…However, excessive shear strain (differential motion) between the flexor tendons and the adjacent SSCT can rupture parts of the collagen network, and has been suggested as a risk factor in the development and progression of CTS . Workplace risk factors such as repetitive motion, fast movement speeds, and flexed wrist postures have been shown to increase tendon‐SSCT shear strain during normal finger flexion‐extension, but the influence of mechanical compression and ischemia remains unknown.…”