For many years Logitech made one of the few alternatives to a mouse for people who had some sort of wrist or hand issue like Carpal Tunnel syndrome (or folks who just hated a mouse). That alternative was the Trackball and there were several versions to choose from for users. About a decade ago, Logitech vacated that space leaving those needing

Source: Hot Hardware – Logitech MX Ergo Reinvents The Trackball Mouse After A Decade-Long Absence