Introduction: What constitutes optimal thoracic curve scoliosis correction is controversial. The development and application of powerful pedicle screw-aided instrumentation constructs has, in some cases, led to hypercorrection of the thoracic scoliosis with resulting coronal imbalance, trunk shift, and shoulder imbalance. The purpose of this study was to compare the clinical and radiographic outcomes between Lenke 1 patients with the highest and lowest degree of correction to assess this risk. Our hypothesis was that greater scoliosis curve correction can be done without producing secondary decompensation.
Methods: Using a prospective AIS database, Lenke 1 curves, with 2-year follow-up (n=385) were ranked by percent coronal correction. The top 15% or high correction group (>80% coronal correction) were compared with the bottom 15% or low correction group (< 40% coronal correction). Clinical and radiographic outcomes, including parameters of coronal and sagittal balance, were compared using ANOVA and χ tests (P ≤ 0.007).
Results: The high correction group (n=39) and the low correction group (n=40) did not differ preoperatively except in lumbar flexibility. In the coronal plane, the high correction group did not show postoperative clinical imbalance (trunk shift and shoulder height) and had better radiographic balance (C7-CSVL shift). The deformity-flexibility quotient (DFQ), which is the ratio of residual lumbar curve to remaining unfused lumbar segments, was lower (optimal) in the high correction group. The residual rib hump was also better. In the sagittal plane, the high correction group had less kyphosis secondary to a loss of kyphosis compared with a gain (improvement) in the low correction group. Despite these differences, SRS scores were not different.
Conclusions: Maximizing Lenke 1 curve correction to achieve greater lumbar correction and improved clinical appearance can be done without compromising coronal balance but may occur at the expense of sagittal alignment. However, surgeons who are learning to apply powerful new corrective methods should be cautious in trying to obtain full correction. Proper preoperative evaluation, fusion level selection, and surgical technique are needed to attain this outcome.