There are studies to back them -I don't have any such pain. But are these mouses really effective and not just another gimmick without proper research backing them? How does it feel to use such a mouse?
Evaluation of flat, angled, and vertical computer mice and their effects on wrist posture, pointing performance, and preference - PubMed
Increasing mouse height and angling the mouse topcase can improve wrist posture without negatively affecting performance.
pubmed.ncbi.nlm.nih.gov
Biomechanics and performance when using a standard and a vertical computer mouse - PubMed
Using a vertical mouse can decrease the exposure to biomechanical risk factors for computer mouse use-related musculoskeletal disorders. Using a vertical computer mouse resulted in less wrist pronation and lower wrist extensor muscle activity. But, training and familiarisation are required.
pubmed.ncbi.nlm.nih.gov