CORRInsights®: Preventing Fusion Mass Shift Avoids Postoperative Distal Curve Adding-on in Adolescent Idiopathic Scoliosis
When a scoliotic curve extends into the lumbar spine, the surgeon is faced with a natural desire to straighten the entire curve, permanently and completely. However, numerous authors [3-5] have shown that preservation of motion segments is important for long-term painless function, particularly in the low lumbar spine. Complicating the decision-making process is the phenomenon of adding-on, in which segments that may appear to be uninvolved in the curve become part of the lumbar curve after surgery. In the current study, Shigematsu and colleagues outline one factor, fusion mass shift, which appears related to the phenomenon of adding-on. Moreover, this factor is controllable by the surgeon, both in preoperative surgery level selection and in the conduct of surgery intraoperatively. As such, fusion mass shift has the potential to improve patient results by minimizing the risk of postoperative adding-on.
Selecting the levels of scoliotic surgery remains an art, but it is an art that is dependent upon the application of basic concepts such as the stable vertebra, the neutral vertebra, preservation of both sagittal and coronal balance, the influence of curve type and stiffness, and (now) fusion mass shift as defined by the authors. Our instrumentation is powerful, but good results still rely upon their artful application.