Sagittal spinal balance after lumbar spinal fusion: the impact of anterior column support results from a randomized clinical trial with an eight- to thirteen-year radiographic follow-up

Randomized clinical trial.To analyze the long-term clinical impact of anterior column support on sagittal balance after lumbar spinal fusion.Several investigators have stressed the importance of maintaining sagittal balance in relation to spinal fusion to avoid lumbar 'flat back,' accelerated adjacent segment degeneration, pain, and inferior functional outcome. Only limited evidence exists on how sagittal alignment affects clinical outcome. Anterior lumbar interbody fusion combined with posterolateral fusion has been proved superior to posterolateral fusion alone regarding outcome and cost-effectiveness. No randomized controlled trial has been published analyzing the effect of anterior support on radiographic measurements of sagittal balance.Between 1996 and 1999, 148 patients with severe chronic low back pain were randomly selected for posterolateral lumbar fusion plus anterior support (PLF + ALIF) or posterolateral lumbar fusion. A total of 92 patients participated. Sagittal balance parameters were examined on full lateral radiographs of the spine: pelvic incidence (PI), pelvic tilt (PT), sacral slope, thoracic kyphosis, lumbar lordosis, and positioning of C7 plumb line. The type of lumbar lordosis was evaluated and outcome assessed by Oswestry Disability Index (ODI).Follow-up rate was 74%. Sagittal balance parameters were similar between randomization groups. None of the parameters differed significantly between patients with an ODI from 0 to 40 and patients with ODI over 40. Balanced patients had a significantly superior outcome as measured by ODI (P0.05) compared with unbalanced patients.No difference in the investigated sagittal balance parameters was seen between patients treated with PLF + ALIF or posterolateral fusion alone. Lumbar lordosis and type of lordosis correlated with outcome but could not explain the superior outcome in the group with anterior support. Whether sagittal balance and anterior support during fusion provide a protective effect on adjacent motion segments remains unclear.