Among ergonomic mice, the most widespread type is the vertical mouse. The vertical mouse has an interesting concept of rotating the orientation of the hand to 45° to 90° compared to the typical mouse. Manufacturers claim that a typical mouse places your wrist in unnatural angles while the handshake position of the vertical mouse is natural.

Some people love the vertical mouse. Since their arm and hand positions have changed, previously overused muscles come to a pause. So their wrist pain is somewhat relieved.

Did vertical mouse really solve your issue? I mean, really?

Can you click a vertical mouse without using your thumb?

No.

The vertical mouse will not stay steady unless your thumb supports it while the buttons are being clicked. In other words, your thumb and index finger must be involved in a 'pinching grip' to click. No wonder why my thumb was sore using the vertical mouse.

Scientific findings support this. 

Dr. David Rempel¹ and his colleagues conducted a series of research to examine factors affecting carpal tunnel pressure. They found in 1997 that carpal tunnel pressure increases when the wrist position is in unneutral angles and when the fingertip is carrying out a pressing task². A year later, they found that carpal tunnel pressure was even higher when pinching than simply pressing³. This means that clicking-and-dragging is worse than just clicking because a pinching grip is sustained.

This leads us to conclude that vertical mice can actually increase wrist tension. This could answer why wrist pain did not go away even when you changed to a vertical mouse.

¹ Dr. David Rempel is a Professor Emeritus in the Department of Medicine at UC San Francisco and Faculty in the Ergonomics Laboratory at UC Berkeley.

² Rempel, D.M., Keir, P.J., Smutz, W.P., and Hargens, A., 1997. Effects of static fingertip loading on carpal tunnel pressure. Journal of Orthopaedic Research, 15(3), pp.422-426.

³ Keir, P.J., Bach, J.M., and Rempel, D.M., 1998. Fingertip loading and carpal tunnel pressure: differences between a pinching and a pressing task. Journal of Orthopaedic Research, 16(1), pp.112-115.