Editorial: Sagittal balance

Abstract

It has become increasingly clear in the past decade that local, regional, and global sagittal alignment of the spinal column is strongly correlated to both quality of life assessments and also the results of spinal surgical interventions. Traditional open spinal reconstructive procedures have emphasized these sagittal parameters recently, correlating to successful radiographic and clinical results. However, the quest for similar type of results when using less invasive surgical techniques has been more challenging. In their article, Manwaring and colleagues1 performed a preliminary radiographic study examining the role that minimally invasive anterolateral lumbar interbody fusion plays in optimizing lumbar sagittal lordosis restoration, global sagittal alignment, and ultimately clinical outcomes. In their retrospective review, data obtained in 36 patients in whom degenerative scoliosis had been diagnosed (coronal Cobb angle of > 10° or a sagittal vertebral axis of > 5 cm) were examined for various coronal and sagittal radiographic parameters. Of 36 patients, 27 had undergone standard anterolateral interbody fusion and 9 had undergone an anterior column release (ACR) with interbody fusion. In all patients a delayed second-stage surgery was performed and consisted of the placement of percutaneous transpedicular posterior instrumentation as well as an anterolateral lumbar interbody fusion or minimally invasive transforaminal lumbar interbody fusion at L5–S1 if that was included in the construct. The authors found, as others have shown, that a standard lateral interbody fusion really did not change segmental and regional lumbar lordosis, although it did improve the coronal Cobb angle. However, the ACR group had significant improvements in segmental and regional lumbar lordosis and sagittal realignment as well as improvement in the coronal Cobb angle. Unfortunately, there were no data provided on complications occurring during or after the procedure, and the mean follow-up for the small ACR group was admittedly short in the preliminary study (11 months). So what can we learn from this preliminary radiographic analysis of these less invasive surgical techniques? In patients with relatively small degenerative lumbar scoliosis (mean coronal curves, 25°), the ACR technique can increase segmental and regional lordosis, which is certainly an important component to the surgical goals and ultimate clinical outcomes. The addition of posterior segmental percutaneous instrumentation did not seem to change the alignment or results, which is intuitive since correction was obtained with the anterior interbody procedure. This is certainly an important finding in the evolution of less invasive spinal surgical reconstructive techniques. However, it is important to note that there are things we did not learn from this radiographic review, including the following: the actual or potential complications from the ACR technique, durability of the radiographic results because the follow-up period was so short, ultimate fusion rates, and clinical outcomes at a minimum 2to 5-year follow-up. Also, whether these results can be replicated at other centers is yet to be determined. I congratulate the authors on this important manuscript and urge them to continue to pursue and publish additional data on complications and longer-term followup in the degenerative lumbar scoliosis population treated with these less invasive surgical techniques. (http://thejns.org/doi/abs/10.3171/2013.10.SPINE13793)