We present 2 cases of symptomatic nondissociative dorsal intercalated segment instability (CIND-DISI) collapse after trapeziectomy and partial trapezoidectomy for pantrapezial arthritis. Preoperative radiographs showed normal carpal alignment in 1 case and a mild DISI alignment in the other. After surgery both developed increased CIND-DISI and carpal symptoms that differed from their original thumb-base problems. One required carpal realignment and fusion; to date the other has responded to nonsurgical treatment. Such problems may be recognized insufficiently by surgeons and thus may be more common than the current literature suggests.