Evolution of Sagittal Imbalance Following Corrective Surgery for Sagittal Plane Deformity

BACKGROUND: Sagittal balance in adult spinal deformity is a major predictor of quality of life. A temporary loss of paraspinal muscle force and somatic pain following spine surgery may limit a patient's ability to maintain posture. OBJECTIVE: To assess the evolution of sagittal balance and clinical outcomes during recovery from adult spinal deformity surgery. METHODS: Retrospective review of a prospective observational database identified a consecutive series of patients with sagittal vertical axis (SVA) > 40 mm undergoing adult deformity surgery. Radiographic parameters and clinical outcomes were measured out to 2 yr after surgery. RESULTS: A total of 113 consecutive patients met inclusion criteria. Mean preoperative SVA was 90.3 mm, increased to 104.6 mm in the first week, then gradually reduced at each follow-up interval to 59.2 mm at 6 wk, 45.0 mm at 3 mo, 38.6 mm at 6 mo, and 34.1 mm at 1 yr (all P <.05). SVA did not change between 1 and 2 yr. Pelvic incidence-lumbar lordosis (PI-LL) corrected immediately from 25.3° to 8.5° (16.8° change; P <.01) and a decreased pelvic tilt from 27.6° to 17.6° (10° change; P <.01). No further change was noted in PI-LL. Pelvic tilt increased to 20.2° (P =.01) at 6 wk and held steady through 2 yr. Mean Visual Analog Scale, Oswestry Disability Index, and Short Form-36 scores all improved; pain rapidly improved, whereas disability measures improved as SVA improved. CONCLUSION: Radiographic assessment of global sagittal alignment did not fully reflect surgical correction of sagittal balance until 6 mo after adult deformity surgery. Sagittal balance initially worsened then steadily improved at each interval over the first year postoperatively. At 1 yr, all clinical and radiographic measures outcomes were significantly improved.