The goal of this study was to evaluate the 4-year minimum (5.5-y average) results of trapeziectomy and ligament reconstruction using a modified Thompson technique with the abductor pollicis longus tendon for the primary treatment of advanced-stage basal joint arthritis (Eaton stages III and IV). We evaluated 25 thumbs in 18 patients after ligament reconstruction arthroplasty for surgical treatment of advanced thumb basal joint arthritis. Treatment consisted of piecemeal excision of the entire trapezium, ligament reconstruction and interposition using the abductor pollicis longus tendon, and 8 weeks of K-wire immobilization of the thumb metacarpal. We evaluated range of motion, lateral pinch, tip pinch, grip strength, and outcomes questionnaires including the Arthritis Impact Measurement Scales 2 Short Form before and at an average of 5.5 years after surgery. Seventeen of 18 patients reported excellent or good relief of pain and were satisfied with their operation, and all of the patients would have the operation again. Of the 25 thumbs, 24 adducted fully into the plane of the palm and opposed to the fifth metacarpal head. Preoperative and postoperative strength comparisons demonstrated an average increase in grip, key pinch, and tip pinch strength of 14%, 12%, and 6%, respectively. The outcomes data demonstrated noteworthy improvement in writing, buttoning a shirt, turning a key/lock, and arthritis pain categories. This technique restored a stable, pain-free thumb that yielded excellent strength and motion at an average of 5.5 years after the procedure. Compared with published reports of techniques that use hematoma distraction or harvest of all or part of the flexor carpi radialis tendon, this modified Thompson technique has similar pain relief, satisfaction, and motion but had less improvement in strength, which might have resulted from differences in the studied samples.