Bridging the knowledge gaps in adolescent idiopathic scoliosis : an emphasis on growth, flexibility and outcome measures

Abstract

Adolescent idiopathic scoliosis is the commonest pediatric spinal deformity. Mild cases need only observation, but those who deteriorate may require bracing or surgery. Determining which patients should be treated requires a comprehensive assessment of a patient’s remaining growth potential. Most of the commonly used methods such as change in body height and arm span, onset of menarche, Risser sign, and bone age assessments are flawed by being retrospective, inconsistent, inaccurate and difficult to use. The distal radius and ulna (DRU) classification has been developed to be an accurate parameter with a large range of coverage from the very young to adolescents reaching skeletal maturity. In this thesis, the DRU classification was studied with reliability analysis, simplification and modification for easy use, and tested against other conventional growth parameters for predicting growth. Simplification of the grading scheme with only one single morphological change was performed and the reliability of this scheme was found to be excellent. It was also superior to commonly used growth parameters with strong prediction for peak growth and growth cessation, which are important time points for initiating and weaning brace treatment, respectively.

In addition to growth assessment, flexibility is important for prediction of treatment strategies and outcomes, but is often overlooked. There are many variations of flexibility assessments for AIS but the supine and fulcrum bending radiographs are two routinely used methods in our unit. The supine radiographs in particular have been used to determine the curve flexibility prior to brace wear. However, its ability to predict in-brace correction is unknown. In this thesis, supine correction of AIS curves was found to correlate highly with in-brace correction and is thus a useful guide to the expected correction achievable with brace treatment. Fulcrum bending radiographs have been shown to predict postoperative curve correction, fusion level selection, and instrumentation strategy. However, there are certain unknown factors that contribute to inaccurate predictions in some operative cases. This was hypothesized to be due to curves without uniform flexibility. AIS curves in this thesis were found to have different segmental flexibilities with the upper and middle segments stiffer than the lower segments. This proves that curve flexibility is not uniform and strategic placement of implants for curve correction should be performed. The stiffer upper and middle segments may require more screws for correction.

Postoperative assessments of AIS are also important to determine treatment outcomes. Although Cobb angle measurements are important radiological outcomes, patient perceived outcomes with objective scores are equally if not more relevant. Having a generic questionnaire such as the EuroQol 5-dimension 5-level (EQ-5D-5L) is necessary to compare the AIS treatment with other pathologies for cost-utility analyses. Yet, the role of the EQ-5D- 5L in assessment of AIS is unclear. In this thesis, validation of the EQ-5D-5L was performed in AIS patients followed by testing its responsiveness and mapping the disease-specific Scoliosis Research Society 22-item questionnaire onto the EQ-5D-5L. Results are promising which support its role in monitoring disease and treatment outcomes in AIS patients.