The scaphotrapeziotrapezoid (STT) joint is the second most common site in the wrist affected by degenerative arthritis. STT fusion has been the traditional treatment for patients with isolated STT arthritis but there are concerns about the complication rate and loss of wrist movement post-surgery. The current study presents the results of an interposition arthroplasty using a scaphoid trapezium pyrocarbon implant (STPI, BIOProfile). Ten STPI's were implanted in nine patients (mean age 66, 58-76 years) with isolated STT arthritis. The mean follow-up was 16.4 (3-35) months. Following surgery, VAS pain scores improved significantly and most patients had minimal restrictions in function, with a mean DASH score of 21. The mean wrist flexion-extension arc was 126 degrees and radioulnar deviation was 43 degrees. Mean grip strength was 82% and pinch strength 85% compared to the non-operated side. Patients were highly satisfied with the results of their surgery (mean VAS score 9.1). No surgical complications were encountered and no significant changes in carpal alignment were noted on radiographs. The results of this study suggest that STPI interposition arthroplasty may be a good alternative to STT fusion for isolated STT arthritis.