Thumb rotation patterns during pinch in patients with trapeziometacarpal osteoarthritis

Trapeziometacarpal joint stability during pinch depends on the balance between the opponens pollicis and the first dorsal interosseous muscles, which control pronation and supination of the first metacarpal, respectively. Disruption of this muscular balance may contribute to joint instability in patients with trapeziometacarpal osteoarthritis, although the mechanisms underlying movement pattern changes in these patients remain unclear. This study aimed to quantitatively compare thumb rotation patterns during tip pinch between patients with trapeziometacarpal osteoarthtits and healthy individuals.

The thumb rotation angle during tip pinch was measured in 36 hands of 27 patients with trapeziometacarpal osteoarthritis and 19 hands of 11 healthy controls using a three-axis gyroscope equipped with a three-axis accelerometer fixed to the dorsum of the thumb metacarpal. The pronation/supination angle was recorded as the rotation around the long axis of the gyroscope.

The trapeziometacarpal osteoarthritis group demonstrated a lower median change in pronation angle during pinch (2.6°) compared with the control group (3.7°) (p = 0.014). The frequency of the thumb supination during pinch was higher in the trapeziometacarpal osteoarthritis group (25%) than in the control group (8.8 %) (p = 0.013). Pronation angles were moderately and negatively associated with the Eaton-Littler and Kellgren-Lawrence classifications for osteoarthritis.

Altered thumb rotation patterns during pinch may contribute to joint misalignment and the development of osteoarthritis. The findings may influence targeted rehabilitation interventions to improve dynamic stabilization of trapeziometacarpal joint.

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