Efficacy of Scoliosis Specific Exercise (SSE) in Patients With Adolescent Idiopathic Scoliosis (AIS) During Bracing: A Randomized Controlled Clinical Trial

Adolescent Idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine, characterized by a lateral curvature and vertebral rotation. Its prevalence is estimated to be 2.5% in children between aged 10 and 16 in Hong Kong. Curve progression occurs during pubertal growth spurt. If the primary curve does not exceed 40 degree at skeletal maturity, it is unlikely to continue to progress, and there are little or no long-term clinical consequences. However, if the curve progresses beyond 50 degree during adolescence, it may cause functional limitation, accelerated disc degeneration with potential neurological deficit, cosmetic concerns, decreased quality of life, and possible progression in adulthood. Thus, surgical correction of the deformity with instrumented spinal fusion is usually recommended if the curve reaches 50 degree during adolescence.

Currently, spinal bracing is the only the only non-operative treatment supported with high-quality evidence that can prevent curve progression. In a randomized controlled trial, Weinstein et al. recently reported in the New England Journal of Medicine that bracing was effective in preventing curve progression to threshold for surgery in 72% of cases. The trial was terminated early due to the treatment benefit in favor of bracing. Nonetheless, the authors reported a treatment failure rate of 25% in the randomized cohort, which was similar to previous published studies. Hence, despite the best available non-operative treatment, the number of adolescents ultimately requiring surgery remains substantial. Surgery is associated with medical comorbidities, can cause psychosocial stress to the children and their families, and has significant financial impact on healthcare, with the total costs of spinal surgery to correct AIS ranked second only to appendicitis among children 10 to 17 years of age. Consequently, further effective strategies to prevent scoliosis progression in children are needed.

Scoliosis-specific exercise (SSE) has been proposed as an additional non-operative intervention that may reduce curve progression during the adolescent growth spurt. However, the standard of care for non-operative treatment of AIS varies widely between North America and Europe, and the use of SSE is not universally accepted. SSE is a potentially low-cost intervention that will be of substantial benefit even if a relative risk reduction in curve progression or reaching the threshold for surgery is reduced in a modest proportion of those participating.

SSE, as opposed to generalized physiotherapy, consists of individually-adapted exercises that aim to promote spinal realignment through self-correction and stabilization, as well as modulating patterns of trunk muscles recruitment. Electromyography (EMG) of paraspinal and abdominal muscles in AIS patients revealed disrupted patterns of muscles recruitment, which are associated with a disparity in trunk isometric rotation strength between sides. AIS patients demonstrate proprioceptive and balance control problems, along with a distorted body schema, resulting in a mismatch between the actual spinal alignment and the patients' internal representation of the body. SSE aims to reverse the anomalous patterns of muscle recruitment through training, and modify the body schema with visual and somatosensory feedback. This forms the theoretical neurophysiological basis for using this treatment strategy for AIS.

Schroth SSE is one of the most studied and widely-used schools of SSE. It is a technique tailored to the type of scoliosis and the curve magnitude of each patient. It is based on vertebrae deflections and sagittal corrections that result in horizontal vertebrae de-rotation. It uses rotational breathing and postural auto-correction to reverse the underlying impairments in spinal muscle function, postural control and proprioception which contribute to the development of curvature in AIS. Patients will also be given cognitive behavioral strategies to empower them to self-manage their conditions.