Fusion Level Determination in Adolescent Idiopathic Scoliosis

Abstract

A number of different methods have been described to determine the upper and lower fusion levels in adolescent idiopathic scoliosis (AIS). These include the stable zone, neutral vertebra, use of bending films to assess mobility of adjacent discs, traction radiographs and prone-push radiographs, etc. Whichever method is used, the selection ultimately relies a great deal on the surgeons experience. We propose that the most important determinant of fusion level is the spines flexibility, such that shorter fusions can be performed for flexible curves, while more rigid curves require longer fusions to achieve balance. Use of the fulcrum bending radiograph could reliably predict spinal flexibility before surgery, and we have successfully used this to determine fusion levels. The principle and technique involved will be discussed in detail.