3D, Dynamic and Mechanically-informed Decision Making in AIS

Adolescent Idiopathic Scoliosis (AIS) is a growth defect of the spine that primarily occurs in prepubertal children between the age of 10 to 14 years, affecting approximately 3% of these otherwise normal children. AIS has been associated with problems related to posture, load-related back pain, as well as aesthetic problems, e.g. the induced asymmetry of the shoulder. Therefore, early diagnosis followed by the appropriate treatment is vital to prevent further curve progression of AIS and minimize the health-related complications of these patients. The current treatment recommendation to stop curve progression for an immature patient with a scoliosis curve between 25 and 40 degrees is to wear a brace. If the curve in the skeletally immature patient is not responding to the brace treatment, dynamic scoliosis correction by vertebral body tethering can be considered when there is still some growth potential left. State-of-the-art guidelines for the selection of fusion levels are currently mainly based on two-dimensional (2D) static radiographic parameters (such as, the Cobb angle and Shoulder balance) and a qualitative assessment of 2D bending or traction radiographs. Several classification systems and algorithms that are based on the 2D static radiographic (X-ray) parameters exist to assist surgeons in determining the appropriate levels to be instrumented. Despite this wide range of classification systems and detailed guidelines available in the literature, spinal fusion does not always yield satisfying 2D radiographic clinical outcome, with revision rates ranging from 3.9% to 22%. Overall, the surgeon is presently not provided with 3D dynamic and mechanical information regarding the deformity of the AIS to guide the decision-making. Obtaining this vital 3D dynamic information regarding the curvature and mechanical behavior of the spine will allow the surgeon to make an evidence-based and well-informed decisions in the treatment of the AIS patient. Consequently, realizing these objectives has the potential to improve patient satisfaction, reduce the postoperative complications and accordingly reduce socio-economic costs associated with AIS treatment. Recent advances in the use of subject specific musculoskeletal models will form the basis to realize this shift from 2D to 3D dynamic in AIS care.