According to this study it is possible, in patients selected according to the SRS inclusion criteria, and treated with an appropriate conservative treatment following SOSORT criteria, to obtain reductions of AIS in most of the patients. This is true considering the SRS outcomes but also in regard others such as the Cobb degrees, ATR, Aesthetic Index and ISICO clinical outcomes. Moreover, in patients who accept treatment it is possible to avoid surgery in AIS that has not previously been treated, with curvatures ranging from 25° to 40° and Risser between 0 and 2.
The subject study was retrospective, and therefore it includes only an efficacy analysis of patients who had reached the end of treatment. Accordingly, the results should be interpreted from this perspective. Most of the studies published in the literature are retrospective as well ; one of the published papers that followed the SRS criteria was retrospective , while the other one is prospective  and ongoing . Prospective studies allow to perform and intent-to-treat analysis, as suggested by the SRS criteria . Nevertheless, an efficacy analysis has its own value in showing what results can be achieved with patients who follow the required treatment, while, conversely, an intent-to-treat analysis allows one to include all drop-outs, which in any case represent a failure of treatment. What should be questioned is whether drop-outs should be considered as fusions (i.e. real failures) or if, in the case of a conservative approach to AIS, dropping out does not automatically mean the patient will arrive at fusion and/or progress beyond 5°. In fact, in the prospective paper by Coillard, patients who withdraw were listed separately but not included in the fused group . In a previous study  we had a low drop-out rate (3.6%, or four patients out of 112) with the same approach presented here, even if the population was different. Currently, we are conducting a prospective study which will presumably be completed within a couple of years' time, in order to perform an intent-to-treat analysis and complete the efficacy analysis performed here.
In this study we did not have one patient fused, nor did we have adolescent who finished treatment at more than 45°. We understand that this result could appear to reduce credibility of the study, being results normally reported in the literature completely different form the ours. Nevertheless, this corresponds to our own everyday experience. Obviously, there could be drop-outs who finish fused, and this can be observed only through a prospective study. Moreover, these results confirm our previous prospective paper published in 2008 , where we obtained a surgery rate of 0.9% in this same efficacy analysis (4.5% in the intent to treat, considering drop-outs as fused patients) in a less-specific population including curvatures from 11° to 53° Cobb.
Comparison with other studies following the SRS criteria
The other two published papers that followed the SRS criteria reported results which were completely different. According to Janicki , using a TLSO in 48 AIS, 85% of patients worsened 6° or more, 62.5% were in excess of 45° at the end of treatment, and 79% were fused; using a Providence brace in 35 patients, the outcomes were 69%, 42.8% and 60%, respectively. This was a retrospective paper, and suffered the same possible bias of the study presented here, albeit with a significant difference: Janicki and colleagues are surgeons, while we are conservative specialists. It could be hypothesized that the drop-outs in our series were mainly patient candidates for surgery who did not achieve good results (and this could explain to some extent why we did not have any patient treated surgically in our series) , while the opposite could be true for a surgical group (even if we don't believe in this assumption). Moreover, we had a very high compliance rate using braces full-time, while Janicki et al. had the best adherence with nightly bracing. Consequently, they concluded by stating their preference for the latter solution to increase compliance. Nevertheless, we must consider that adherence to treatment is not only a matter of the braces used but also of the total management of patients . Obviously, raising the point of surgeons versus conservative specialists, we are not stating anything about competence, but only about general settings and attitudes toward treatment and interpretation of obtained results, that are possibly understood by patients and can drive their behaviours.
Another significant reason for the differences found with Janicki et al.  could be the type of braces used (i.e. mechanisms of action) and/or their quality (i.e. single-brace efficacy in the context of single patients). Unfortunately, we do not have any measurement system for this, apart from in-brace correction , which is not reported in these papers.
The other study following SRS criteria, by Coillard et al. , was performed on 170 patients wearing the SpineCor brace and reported at the end of treatment (efficacy analysis) that 22.9% of patients were fused, 33.5% had progression of at least 6° and 24.1% finished treatment in excess of 45°. There were 12 patients (7.1%) who withdrew from treatment and were not included in the efficacy analysis. These results were much better than those reported by Janicki  but worse than those reported in this study. Nevertheless, the comparison of Coillard's results with ours is coherent with what has been reported elsewhere in the literature. In fact, the effectiveness of the SpineCor brace has been reported to be inferior to rigid TLSO braces in a randomised controlled trial , as well as in a study with an historical control group .
Compliance and SOSORT Criteria
The compliance rate can serve as a general justification for these results. SpineCor brace results have been reported by the developers of the brace; moreover, the SpineCor approach requires systematic, frequent contact with the patient by a well-trained team . All these points are part of the SOSORT criteria of brace treatment management , which we followed in this study. Consequently, the study by Coillard et al. is more comparable to our results than to those of Janicki, given the management applied during treatment.
Another characteristic of our study should be pointed out: Apart from the application of the SOSORT criteria, each treatment has been tailored on each single patient so as to maximise compliance, as well as to allow the best possible inclusion of patients and their parents in the treating team. Not only the starting point of treatment (23 versus 21, or 18 hours per day of bracing, or even Risser cast or exercises), but also the final possible results were tailored during treatment (i.e. we decreased brace wearing individually, according to the need) in terms of the optimal or minimal results following the ISICO outcomes . Finally, exercises were used as a means to increase compliance, not simply as a way to increase bracing results, as has been proved in some studies [16, 21, 22]. In practice, all treatment management was focused on the patient not only in terms of SOSORT criteria but also in terms of treatment planning.
Another possible explanation for the high compliance rate observed could be the private setting of our Institute, versus the usual Health National Service one used in the remaining of our country (Italy): nevertheless, in our view the SOSORT criteria, the psychological approach we used, the presence of a complete and well trained team play the most important role in increasing compliance.
Strengths and weaknesses of the study
This is the third study published with respect to SRS criteria, and it is the first one that has also fulfilled the SOSORT criteria for bracing studies. The former criteria provide the methodological framework while the latter give the clinical framework so as to gather the best possible data on this kind of treatment. The number of patients is low, but the population is comprehensively selected and cohesive.
This is a retrospective study. Ideally, we should have performed a prospective study, but our institute was established in 2003 and we have been collecting a prospective database since that time. We verified, in a preliminary analysis, that the population with respect to the SRS criteria was too low at this stage to perform an adequate prospective study. Consequently, we decided upon a retrospective analysis of all patients who completed their treatment which, at the start, respected the SRS criteria.
Another characteristic of the paper is that not simply has one standardized treatment been proposed but patients have been treated with different braces and some have been treated with exercises exclusively (even if these have been excluded from the whole group and considered as a group per se). Nevertheless, this research concentrates on a complete, conservative approach, focused on the increase of compliance through management and a clinical everyday approach. It represents the everyday clinical reality instead of a "laboratory" setting as it could be in other studies. This could be considered a weakness of the paper as well as a strength.
Other possible limits to be considered include: the high prevalence of females in this population, but this is typical of the everyday clinical reality in scoliosis treatment (moreover we did not find differences according to genders); the inclusion of two patients treated with exercises only and two with casting before bracing, and not only of braced patients, but we did not find any difference in the subgroup analyses, and the retrospective design required in our view to include all patients respecting the SRS criteria without introducing any other possibly confounding inclusion criterion; the fact that only 85% of patients reached the 2 years follow-up, but this subgroup was not different from the entire population for any basal characteristic nor any final result.
It must also be stated that for many years we have conducted our work with consideration for the SOSORT criteria , in fact well before they had been established, because they are part of our everyday clinical approach. In this respect, they are not something new to our work, which is totally focused on compliance that exceeds the SOSORT criteria in various respects.