Development of a kinematic model to predict finger flexor tendon and subsynovial connective tissue displacement in the carpal tunnel

• Published in: Ergonomics Vol. 58; no. 8; pp. 1398 - 1409
• Main Authors: Kociolek, Aaron M., Keir, Peter J.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 03.08.2015; Taylor & Francis LLC
• Subjects: Adult; Biomechanical Phenomena; Carpal Joints - diagnostic imaging; Carpal Joints - physiopathology; Carpal tunnel syndrome; Carpal Tunnel Syndrome - diagnostic imaging; Carpal Tunnel Syndrome - physiopathology; Ergonomics; Female; finger; Fingers & toes; Fingers - diagnostic imaging; Fingers - physiopathology; Friction; Healthy Volunteers; Human factors research; Humans; Kinematics; Male; Movement; Range of Motion, Articular; relative displacement; repetitive motion; shear injury; Synovial Membrane - diagnostic imaging; Synovial Membrane - physiopathology; tendon travel; Tendons - diagnostic imaging; Tendons - physiopathology; Ultrasonic imaging; Ultrasonography, Doppler, Color; Wrist - diagnostic imaging; Wrist - physiopathology; Young Adult; finger; shear injury; tendon travel; repetitive motion; relative displacement
• DOI: 10.1080/00140139.2015.1013575
• ISSN: 0014-0139

Finger flexor tendinopathies and carpal tunnel syndrome are histologically characterised by non-inflammatory fibrosis of the subsynovial connective tissue (SSCT) in the carpal tunnel, which is indicative of excessive and repetitive shear forces between the finger flexor tendons and SSCT. We assessed flexor digitorum superficialis (FDS) tendon and adjacent SSCT displacements with colour Doppler ultrasound as 16 healthy participants completed long finger flexion/extension movements captured by a motion capture system. FDS tendon displacements fit a second-order regression model based on metacarpophalangeal and proximal interphalangeal joint flexion angles (R 2  = 0.92 ± 0.01). SSCT displacements were 33.6 ± 1.7% smaller than FDS tendon displacements and also fit a second-order regression model (R 2  = 0.89 ± 0.01). FDS tendon and SSCT displacement both correlated with finger joint thickness, enabling participant-specific anthropometric scaling. We propose the current regression models as an ergonomic method to determine relative displacements between the finger flexor tendons and SSCT. Practitioner Summary: Relative displacements between the finger flexor tendons and SSCT provide insight into gliding and friction in the carpal tunnel. Our regression models represent a move towards mechanistic-based ergonomic risk assessment of the wrist/hand. This is a natural evolution of ergonomic methods based on tendon-joint interaction.