This article provides a qualitative and quantitative outcomes assessment of a consecutive series of 27 patients (30 thumbs) with basal joint arthritis of the thumb undergoing ligament reconstruction and tendon interposition arthroplasty. Outcome analysis revealed that 24 (89%) patients were satisfied with the relief of pain provided by the arthroplasty and 23 (87%) would undergo surgery again. Eighteen (67%) thumbs were noted to have improvement in the ability to perform activities of daily living. Significant improvements were noted in web space measurements and in grip and pinch strength determination. X-ray film assessment using the trapezial space ratio averaged 0.33 ± 0.08 in preoperative x-ray films of thumbs with stage III and IV degenerative arthritis and 0.23 ± 0.07 in thumbs following basal joint arthroplasty. This represents a total decrease of 51% in the trapezial space ratio following arthroplasty compared to the normal values obtained in previous studies and 33% compared to the preoperative values obtained in this study. Outcomes assessment at a mean of 42 months after surgery showed that there was no significant correlation between maintenance of trapezial height and both objective and subjective clinical outcomes. Although ligament reconstruction consistently failed to restore trapezial height, primary and secondary clinical outcomes following basal joint arthritis were almost uniformly satisfactory.