Effectiveness of Three Dimensional Correction During in Bracing in Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS), a three-dimensional (3D) deformity of the spinal column characterized by lateral deviation and vertebral rotation, affects 3.5% of children during puberty in Hong Kong. Untreated scoliosis continues to deteriorate beyond adolescence, and curves that progress beyond 50 degrees can lead to chronic back pain, cardiopulmonary compromise, poor cosmesis and negative psychological impact. Hence, surgical correction of the deformity by instrumented spinal fusion is recommended when curves reach 50 degrees. Although surgical risks have decreased with improved techniques, surgeries for scoliosis correction still carry significant medical co-morbidities, psychological stress to the children and their families, and substantial financial burden on healthcare. Effective non-operative strategies to prevent curve progression during adolescence are needed. Currently, the most effective non-operative treatment supported by high quality randomised controlled trial to prevent curve progression is by spinal bracing. In the Bracing in Adolescent Idiopathic Scoliosis Trial (BrAIST) study, bracing was effective in preventing curve progression to threshold for surgery in 72% of cases. The failure rate, therefore, remains substantially high despite the best available non-operative treatment. Previous studies have identified factors affecting brace success, including skeletal age, curve type, curve magnitude, and flexibility, but none of these is modifiable. Brace treatment requires a wholistic approach, and brace design and fabrication are important determinants of brace effectiveness. Traditional Boston-style thoracolumbosacral orthoses (TLSO), such as those used in the BrAIST study, can achieve in-brace coronal curve correction reliably but their effects on the 3D curve correction are highly variable. Since AIS is a 3D deformity, it is reasonable to postulate that braces which can achieve correction in all three planes have a higher chance of success.

Rigo Chêneau orthoses (RCO) were developed approximately two decades ago by Dr. Manuel Rigo of Barcelona who made improvements to the Chêneau brace that French doctor Jacques Chêneau invented in 1978. RCO was designed with the intent to combine biomechanical forces in three dimensions, including curve derotation. They use an open pelvis design with anterior opening. Instead of focusing on one-dimensional correction, RCO treats scoliosis in all three dimensions and follows a unique curve Rigo classification protocol to guide brace design. RCO not only keeps the curves from getting worse as seen on an X-ray, but also corrects as much as possible the way the body looks. Every attempt is made to decrease the noticeable effects of scoliosis such as rib humps, uneven shoulders, hips which are translated or rotated, and centering the head over the pelvis. To achieve successful 3D scoliosis correction, in-brace Cobb angle correction must be 50% to be considered acceptable. This is often true and it is also true that the Cobb angle, which is easily assessed, has been the gold standard of measurement for brace quality. However, not all patients can and/or should be corrected to 50% in-brace correction. In some cases, a 25% in-brace correction coupled with good 3D correction is acceptable and sufficient to prevent scoliosis progression, when greater Cobb angle correction would cause negative compensations. Overall, some patients are best served by targeting a low in-brace correction, whereas for others an 80% in-brace correction is both achievable and desirable.