Effectiveness of the Rigo Chêneau versus Boston-style orthoses for adolescent idiopathic scoliosis: a retrospective study

Adolescent idiopathic scoliosis (AIS) affects 2 to 3% of adolescents between the ages of 10 and 18 years [1, 2]. Brace treatment is commonly offered when the spinal curve has reached 25° [3]. Since the Bracing in Adolescent Idiopathic Scoliosis Trial study in 2013 [4], bracing has been increasingly recognized as an effective nonsurgical means of scoliosis treatment. However, the comparative effectiveness of most types of braces for AIS has not been definitively established [5].

A rigid thoracolumbosacral orthosis (TLSO) is a brace worn to minimize progression of AIS. There are various TLSO designs (e.g., Boston, Milwaukee, Wilmington) [6]. Rigo Chêneau orthoses (RCOs) were developed approximately two decades ago, with the intent to combine biomechanical forces in three dimensions, including curve derotation. They use an open pelvis design with anterior opening. However, studies of the RCO are limited, and we know little about its effectiveness, particularly in relation to other braces [5, 7, 8].

In the current study, we reviewed records of patients treated at one large academic medical center’s pediatric orthopedic scoliosis practice who were prescribed full-time bracing for AIS. Our objective was to determine if brace type, specifically the RCO compared with a Boston-style TLSO, affected outcomes. Our hypothesis was that different brace designs would lead to different patient outcomes.

In this retrospective review of a large academic medical center’s patients with AIS and their experience with full-time brace treatment, we found that patients treated with RCOs were substantially less likely to progress to spinal surgery and had smaller mean change and smaller percent increase in major curves from treatment initiation through follow-up than patients treated with a TLSO, despite similar baseline characteristics and brace wear time. The outcomes of curve progression less than 45° or progression to surgery and major curve improvement of at least 6° were not statistically different; however, they appeared to favor RCOs. Although previous studies have shown the benefits of bracing [4, 11–13] and the benefits of the RCO for treatment of AIS [7, 8], none has compared efficacy of the RCO with other orthoses. For this study, we incorporated guidelines from the SRS Bracing Committee and SOSORT to establish our inclusion criteria [10] and tracked patients from early Risser stages until maturity or surgery to understand the effects of brace type, specifically RCO versus TLSO, on outcomes.

We consider our outcomes for brace treatment in relation to previous studies’ findings. In the Bracing in Adolescent Idiopathic Scoliosis Trial study, 72% of those with TLSO bracing had curve progression to less than 50° [4]. Similarly, our study showed that 68% of patients with TLSO bracing had major curve progression to less than 45° [4]. Previous studies, mostly using Milwaukee TLSO braces, have shown a large spectrum of success rates for a range of curve outcomes, likely because of dissimilarity in brace quality, patient characteristics, and decision thresholds for spinal surgery [14–18]. Most of these studies took place before SRS and SOSORT guidelines on reporting; thus, standards of outcome measurement and participant selection varied [10].

Little research has been published on outcomes for RCOs. Zaborowska-Sapeta et al. [8] reported on 79 patients with RCOs in Poland. In their study, 12.9% of patients progressed to a major curve greater than 50° at final follow-up, with a mean major curve increase of 9.2° for the overall study population [8]. Although we used the SRS-recommended outcome of 45°, our results are comparable to those of Zaborowska-Sapeta et al. [8]. However, our population had a lower mean change in major curve from baseline to follow-up with the RCO. Ovadia et al. [7] published the results of 93 patients in Israel treated with RCOs and found that 84% of patients’ curves progressed by less than 5°. Although we studied a smaller number of patients with RCOs than these two international reports, our study is an important addition to the research because it is one of the first to compare outcomes after RCO use versus general Boston-style TLSO bracing.

Several factors could have contributed to the favorable outcomes for RCOs compared with TLSOs in our study. First, the RCO construction with three-dimensional corrective forces may have a better effect on scoliosis curves compared with the TLSO. Second, the lighter weight of the RCO and more open design may have made it more desirable and comfortable for patients to wear, leading to increased compliance. However, we did not observe a difference in patient-reported mean wear time between brace types during the course of follow-up. Third, because this was an observational study of clinical practice, families had a choice of orthotists and orthoses. Although we did not measure how families made these decisions, we believe variation in geographical distance to orthotists and heterogeneity of insurance coverage for orthoses could have influenced the type of brace adolescents received. In addition, families who chose the RCOs could have had other factors that made their adolescents more likely to have successful bracing outcomes.

This study has limitations. Despite the large number of records encompassing 15 years of a busy, academic scoliosis clinical practice, we had a relatively small sample of patients using RCOs compared with the two international reports, and this may have limited our ability to detect statistically significant differences in some measures [7, 8]. RCO braces were principally made by one skilled orthotist in the region, which contributed to their lower frequency. Despite this, the relative comparability of our outcomes with previous TLSO and RCO studies provides face validity. In addition, this was a retrospective review of an outpatient clinical practice, and we did not have quality-of-life measures, objective monitoring of time wearing the brace, or blinded, independent outcome assessment. Although self-reports tend to overestimate brace wear time [19], it is unlikely that reported wear time would differ systematically between patients with TLSOs and RCOs in this review of a real-world clinical practice.

Another potential limitation was that although the percent initial in-brace major curve correction appeared to be better in RCOs compared with TLSOs, the difference was not statistically significant, as we may have expected given the positive RCO outcomes at the end of treatment. This could have been caused in part by the smaller number of RCOs and by the fact that if the initial correction was not clinically acceptable to the orthopedist, he would recommend the patient return for brace adjustments to achieve optimal correction. Further, in-brace radiography was generally not performed. Thus, the 1-month in-brace measurements presented here may underestimate actual in-brace correction, particularly for RCOs. In addition, the in-brace measured curve correction reflects coronal changes only, not rotational changes, which could not be studied. However, on clinical assessment such as out-of-brace examination of forward bending, the orthopedist noticed that rotational prominence often diminished in RCO-treated patients. The RCO’s influence on curve derotation may be particularly important for its effectiveness in treating scoliosis; however, future research is needed to elucidate how this mechanism contributes to bracing success [7].

There are several strengths of our report. We followed guidelines for patient inclusion and choice of clinical outcome variables [9, 10]. Our results provide a real-world comparison of patient experience with brace types in a large outpatient scoliosis practice. This use of SRS and SOSORT criteria to compare outcomes by brace type is rare in prior studies. Moreover, the similar clinical characteristics at baseline allow an assessment of differences between brace types, despite a relatively small sample size for the RCO group.

In this large retrospective review of an academic outpatient scoliosis practice, patients treated with RCOs were substantially less likely to progress to spinal surgery than those treated with Boston-style TLSOs. Patients treated with RCOs also had smaller mean change and smaller percent increase in major curves from treatment initiation through follow-up. Future studies should examine differences in outcomes by brace type in other settings and in larger samples, and they should investigate the impact of the rotational dimension of correction with RCOs. Clinicians may consider increasing use of RCOs for AIS.