A clinical and radiographic assessment of 80 patients with adult lumbar deformity (average age 53.4 years) who underwent long (average 7.6 vertebrae, 5-11 vertebrae) segmental posterior spinal instrumentation and fusion from the thoracolumbar spine to the L5-S1 (average 4.5 years, 2-15.8-year follow-up) was performed. We defined the optimal sagittal balance (n = 42) group, the distance from C7 plumb to superior posterior endplate of S1<or = 3