The immediate goals of treatment for children with EOS are to minimize physical disability including respiratory symptoms and relieve pain to improve appearance. The long-term aim of treatment is to prevent the onset of new symptoms, minimize future decline in function, and prevent premature death. While several useful frameworks have been proposed to organize outcomes, the International Classification of Functioning [9] has particular relevance to surgery.

The pathway (Fig. 55.2) begins with a disease, which in turn leads to impairment. Impairment is defined as an abnormality of structure or function. Impairments lead to disabilities, defined as the lack of ability to perform an activity in a manner considered normal. Finally, activity restrictions lead to handicap or role limitation, the inability to fulfill roles, which for children refer to family, friends, and school. In the ICF pathway, the disease could be congenital scoliosis leading to spinal, chest wall, and lung deformity. These impairments lead to physical and respiratory disability, limitations in school and play, and, possibly, early death. Such a pathway is particularly relevant to the area of early-onset scoliosis because our treatments are often directed at reducing spine and chest-wall deformity. If treatments reduce impairments, the hope is that, in turn, we will ameliorate activity restrictions, enhance role function, and prevent early death. However, the pathway is clearly not linear. Furthermore, children with EOS often have associated conditions that moderate the pathway, influence the success of treatment, and lead to other impairments with additional consequences. Nevertheless, this framework provides a way to categorize measures and draw attention to the important question of what treatment is best at reducing impairments, thereby positively affecting the consequences of disease.

The Cobb angle is a well-accepted primary endpoint in adolescent idiopathic scoliosis. However, Campbell has highlighted the complex three-dimensional relationships between EOS thoracic deformity and pulmonary function, which are poorly reflected in the unidimensional Cobb measurement [10–12]. Sagittal deformity on radiograph can provide a second dimension of the complex spinal deformity, and it is an often-utilized outcome in EOS studies. Campbell and others [10, 11] have described a variety of other radiographic measures including the space available for the lung, thoracic height, the spinal penetration index, and the posterior thorax symmetry ratio. Other potential radiographic measures include the interpedicular line ratio, decompensation, shoulder level, and vertebral rotation. Mehta [13] has brought attention to the importance of the position of the ribs in relation to the spine in the idiopathic infantile scoliosis population. A rib vertebral angle difference of 20° or more strongly predicted progression in this group. However, even within the diagnostic category of “infantile idiopathic scoliosis,” it is not clear that we are examining a single clinical entity. As Fernandes and Weinstein [14] questioned, “Is resolving scoliosis, as opposed to progressive scoliosis, a different entity with a different etiology, or does infantile idiopathic scoliosis have a full spectrum of presentations.”

While pulmonary function is of central importance in the EOS population, the measurement of pulmonary function in very young children requires special equipment and technique. Furthermore, it is not clear that traditional measures of pulmonary function such as vital capacity and expiratory volumes sufficiently describe the pathology relevant to the children with EOS. Redding [15] has shown significant alterations in lung function in children with congenital scoliosis and has hypothesized that scoliosis affects lung function by incursion into the hemithorax, as well as by reducing chest-wall compliance and excursion, producing asymmetry in lung size and function. However, this study of 39 patients with EOS did not demonstrate a correlation between Cobb angle and pulmonary measures. Computerized tomography with three-dimensional reconstructions provides the ability to estimate lung volumes and characterize the intrathoracic deformity [16]. Work by Adam [17] has shown strong correlations between lung volumes as measured by CT and pulmonary function tests. This study highlights the complex nature of spine, thoracic, and lung deformity, and it discusses the limitations of traditional pulmonary function tests that ignore the significant asymmetries in right versus left lung. However, concerns about the increased risk of malignancy associated with routine and perhaps repeated CT scans limit its use as a research tool [18]. Magnetic resonance imaging may have similar potential, though investigations in this area are still in their infancy.

It is clear that many patients with early-onset scoliosis have significant issues with a variety of aspects of health-related QOL, but measurement of QOL is fraught with difficulties in this population. Vitale et al. [7] have documented significant perturbations in health-related QOL as measured by the Child Health Questionnaire [19] in older patients who had undergone expansion thoracoplasty. However, generic measures of QOL have been developed and validated primarily in patients >5 years of age limiting the usefulness in this population. Children develop and mature, creating a moving target for functional assessment in this population. Finally, health issues in this heterogeneous population can be quite specific and may not be fully captured with available “off-the-shelf” measures of health status.

Therefore, collaborative efforts between the Children’s Spine Foundation and Growing Spine Study Group have yielded the Early-Onset Scoliosis Questionnaire (EOSQ), which is a validated instrument in EOS patients. It is now being utilized in various studies as a novel and valid outcome for EOS patients.

Despite the considerable obstacles to meaningful clinical research in this area, research efforts have afforded clinicians some initial understanding of important issues in this area. Following is a brief summary of the available evidence pertinent to the field of early-onset scoliosis.