The purpose of this study was to determine the long-term consequences of trapeziectomy and ligament reconstruction and tendon interposition (LRTI) for trapeziometacarpal osteoarthritis in patients aged less than 56 years. A retrospective study was performed to investigate the outcome of trapeziectomy and LRTI with a follow-up period of greater than 5 years in patients aged less than 56 years at the time of surgery. Patients completed the Disabilities of Arm, Shoulder, and Hand (DASH), the Patient-Rated Wrist Evaluation (PRWE), and a 10-point visual analog score for pain (VAS). Objective assessments included thumb opposition, palmar and radial abduction angles, and grip, lateral key, and thumb tip pinch strengths. Radiographic assessments of the thumb carpometacarpal joint were performed in three planes, and the trapezial space and trapezial space to metacarpal height ratios were calculated. Between January 2005 and December 2017, 105 patients were treated. Forty-eight patients with 58 thumbs returned for review. The mean patient age at the time of surgery was 52.5 years, and 96% of the patients were women. The mean follow-up period from surgery was 11 years. The mean VAS score was 1. A significant association was found between younger age at the time of surgery and increased proximal migration of the metacarpal, between high VAS pain scores and high PRWE and DASH scores, weak grip, lateral key pinch and thumb tip pinch strength, and Kapandji score, and between the follow-up period and increasing VAS pain, PRWE, and DASH scores. Trapeziectomy and LRTI are effective procedures for patients aged less than 56 years. The benefits of surgery should be balanced against the deterioration in the outcome measures of DASH and PRWE and increasing VAS scores with increasing intervals from surgery. Therapeutic IV.