The aim of this study was to determine the clinical and radiographic outcomes and survivorship of the ISIS® (Evolutis™, Briennon, France) trapeziometacarpal prosthesis at a minimum follow-up of 5 years. Of the 77 implants (66 patients) reviewed at a mean follow-up of 107.5 months, pain and function had improved significantly. Fourteen cups (19%) and three stems (4%) appeared to have loosened on radiographs. Loosening occurred more often with cemented cups than screwed cups (p = 0.0342). In five cases, the prosthesis was removed and revised by trapeziectomy and interposition: four were cemented cups (three loosening, one trapezium fracture) and one was a loosened metacarpal stem. A single case of dislocation occurred during the follow-up period. The survival rate was 94% (95% CI: 85 to 97). The ISIS® prosthesis is a reliable implant for treating disabling thumb basal joint arthritis, with a low complication rate and long-lasting clinical and functional improvements. Using a screwed trapezial cup instead of a cemented one appears to prevent loosening and the need for surgical revision.