Difference between the thumb motions in carpal tunnel syndrome and trapeziometacarpal osteoarthritis.

BACKGROUND

This study quantified thumb movement in patients with trapeziometacarpal osteoarthritis and carpal tunnel syndrome and examined the characteristics of each disorder using three-dimensional motion analysis.

METHODS

Twenty-three hands of 23 patients with trapeziometacarpal osteoarthritis, 88 hands of 73 patients with idiopathic carpal tunnel syndrome, and 29 hands of 20 healthy volunteers were included in this study; three-dimensional thumb kinematics were measured during the circumduction task using a retroreflective surface-based marker method.

FINDINGS: Trajectory of thumb tip reduced in both patient groups compared to healthy controls, with carpal tunnel syndrome exhibiting the flattening shape. Trapeziometacarpal osteoarthritis patients had decreased range of motion in all directions at the trapeziometacarpal joint, while maintaining flexion-extension at the metacarpophalangeal and interphalangeal joints. Carpal tunnel syndrome patients showed reduced motion particularly in metacarpophalangeal and interphalangeal flexion-extension. Joint contribution analysis revealed decreased trapeziometacarpal involvement and increased compensatory metacarpophalangeal and interphalangeal movements in trapeziometacarpal osteoarthritis, while carpal tunnel syndrome showed impaired metacarpophalangeal abduction.

INTERPRETATION: This study provides novel insights into the distinct kinematic characteristics of trapeziometacarpal osteoarthritis and carpal tunnel syndrome, offering potential for improved screening and assessment of thumb motor impairments in these conditions.

EVIDENCE LEVEL: Diagnostic LEVEL III.