Surgical Level Selection in Adolescent Idiopathic Scoliosis: An Evidence-Based Approach

Abstract

The selection of fusion levels in the treatment of adolescent idiopathic scoliosis remains complex. The goals of surgery are to minimize the risk of future progression and optimize spinal balance while fusing the least number of levels necessary. Several classifications, rules, and algorithms exist to guide decision making, although these have previously not been easily referenced in a study. This review aims to provide an evidence-based approach of selecting fusion levels that balances the expert opinion of the authors with the current literature.A dolescent idiopathic scoliosis (AIS) is defined as a three-dimensional curvature of the spine resulting in 10°or more spinal angulation in individuals aged 10 to 18 years without an otherwise identified medical etiology. 1 The prevalence of AIS is 0.5% to 5%, with a higher ratio of affected female than male patients.The overall prevalence of patients with curves at or greater than 30 or 40 degrees is 0.2% and less than 0.1%, respectively. 2 Of all patients diagnosed, 10% will require some form of intervention, with approximately 0.1% of patients progressing to a curve magnitude that requires surgical intervention. 2 While AIS curves of 30°or less at skeletal maturity are unlikely to have additional progression, a curve of 45°to 50°in the thoracic spine and 40 to 45 in the lumbar spine at skeletal maturity will progress upwards of 15°o ver a patient's lifetime. 2 Patients with curves 50°or greater at skeletal maturity will progress roughly 1 degree per year over a patient's lifetime. 2 The literature demonstrates benefits to spinal mobility and clinical outcomes with sparing lumbar segments during fusion when possible, highlighting the importance of understanding appropriate fusion levels. 3 Contrarily, improperly chosen levels can potentially lead to proximal or distal junctional kyphosis (PJK, DJK), shoulder or pelvic asymmetry, curve adding on, or truncal shifts. Given the clinical and economic importance of optimizing levels included in a fusion construct, considerable effort and study have been devoted to this topic. Nonetheless, there still is a lack of clear consensus on the selection of fusion levels. PurposeWhile choosing levels retains a component of the "art" of medicine rather than a purely algorithmic approach, we have done our best to combine our

Comparable rates of lumbar disc degeneration at long-term following adolescent idiopathic scoliosis spinal fusion extended to L3 or L4: systematic review and meta-analysis

“…According to Lenke classification [ 1 ], inclusion of all structural curves in the spinal fusion area is recommended. Thus, when dealing with double major or TL/L curves (Lenke pattern 3, 4, 5 and 6), the fusion area must be extended to the lumbar spine, and the usual recommendation for the selection of the lowest instrumented vertebra (LIV) falls on L3 or L4 based on TL/L factors [ 1 , 3 , 10 ].…”

“…The goals of AIS surgery are to minimize risk of future deformity progression, to optimize spinal balance both in the coronal and sagittal plane and fuse the least possible number of motion levels [ 3 ].…”

“…The advent of segmental instrumentation allowed spinal surgeons to apply translation and derotation forces on all instrumented levels; therefore, it has become possible to preserve motion levels distally [ 5 ]. Up to date, the selection of lowest instrumented vertebra (LIV) when fusing a TL/L curve is substantially limited to L3 or L4, in rare cases L5 [ 3 , 5 – 11 ].…”