ROTATIONAL EFFECT OF THE 3D BRACE IN THE TREATMENT OF ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Objective: To evaluate the axial correction capacity of the 3D brace in treating Adolescent Idiopathic Scoliosis (AIS). Methods: A retrospective study was carried out with 61 patients with AIS who obtained the 3D brace, between 2019 and 2022, in a laboratory that manufactures orthotics and orthopedic prostheses. These individuals underwent independent analysis of radiographic parameters by evaluating vertebral rotation using the Nash and Moe classification. The analyzed radiographs were taken in orthostasis before and after treatment with the 3D vest. Patients were divided into groups I and II-IV according to the Nash and Moe radiographic classification. Corrective capacity was estimated by assessing the degree of vertebral rotation before and after treatment. Results: Of the 61 patients evaluated, 36 (59%) had Nash and Moe grade I, and 25 patients grade II-IV before treatment. After treatment, 13 (21%) had grade II-IV, and 48 had grade I. Of the patients categorized as II-IV, 64% had improvement in the rotational profile. None clinical studies or radiographic parameter was associated with a change in rotational profile other than brace use (p=0.012). Conclusion: In the studied sample, treatment with the 3D vest promoted a change in vertebral rotation according to the Nash and Moe classification. The majority showed improvement in this parameter of evaluation of treatment of AIS. Level of Evidence III; Retrospective Study.


INTRODUCTION
The Milwaukee and Boston vests have been the most widely used orthoses in the conservative treatment of AIS over the last few decades.¹Both orthoses, due to their mechanism of action, do not act on vertebral rotation and tend to rectify the physiological curves in the sagittal plane, with the potential to produce what we know as flatback.² ,³ Multi-planar correction vests first appeared in the early 1990s with the work of Chêneau.The Chêneau brace provided the biomechanical basis for multiplanar correction for other orthoses developed later, such as the Wood-Chêneau-Rigo (WCR ® ), 4 the Sforzesco, the Dynamic Derotation Braces (DDBs), S4D, etc.In Brazil, these orthoses are generically known as 3D vests, whose main purpose is to transfer multifocal corrective forces to the spine, acting on the scoliotic curve in the sagittal, coronal, and axial planes. 2,5The 3D brace's ability to correct vertebral rotation in the axial plane is a major advantage over the braces used in previous decades. 6Controlling the rotation of the curve is fundamental to controlling the progression and imbalance of vertebral alignment. 7However, to date, no study has evaluated the rotational corrective effect of the 3D brace. 8herefore, this study aims to evaluate the effect of the 3D vest on vertebral rotation in patients with adolescent idiopathic scoliosis.

Research design
A retrospective study was carried out to evaluate the effect of the 3D vest on the vertebral rotation of scoliotic curves in patients with AIS using the Nash and Moe method.

Ethics
This work is part of the EIA research line and was approved by our institution's Research Ethics Committee, with the CAAE identification number: 44775621.1.0000.5128.
Place and period of the study The study was carried out between January 2019 and January 2022 with patients diagnosed with AIS who came to an orthosis and prosthesis laboratory in Belo Horizonte-MG.

Main event
The main event of this study was the variation in the rotational profile of the apex of the scoliotic curve assessed by the Nash and Moe method before and after treatment with the 3D vest.The adjacent vertebra with the highest degree of rotation was used when the curve's apex was in an intervertebral disc.

Secondary variables
The secondary variables studied were: gender, age, side of the convexity of the main curve, the apex of the main curve, location of the curve, type of curve, Risser classification, and magnitude.Table 1 describes the name and operational definition of each variable studied.

Sample
Sixty-two patients with AIS were admitted during the study period to evaluate the degree of vertebral rotation after using the vest.Of the 62 patients evaluated, one was excluded due to insufficient data or because he was not in the 10-17 age group.Sixty-one patients made up the final sample of this study.

Development of the study
We selected only patients diagnosed with AIS, aged between 10 and 17 years, who had panoramic anteroposterior radiographs of the spine in orthostasis taken before and after treatment with the 3D vest.
Two investigators collected data, both orthopedic surgeons who are members of the Brazilian Society of Orthopaedics and Traumatology.The degree of apical vertebral rotation using the Nash and Moe classification was identified using the tools in the Surgimap® software (Figure 1).The following secondary variables were then analyzed about scoliotic curves: apex of the main curve, location of the curve, type of curve, Risser classification, and magnitude.Risser's sign has also been grouped into type A (0,1,2) and type B (3,4,5). 9,10

Data analysis
After selecting the data and radiographic images of the 61 patients, they were all classified according to Nash and Moe before the use of the 3D vest and immediately after its use, and a descriptive statistical analysis of the profile of the study participants was carried out.An association study of the secondary variables with the Nash and Moe classification change, stratified into two categories, was also carried out -grade I and grade II-IV categories of vertebral rotation.
The mean, standard deviation, median, quartiles, minimum and maximum were calculated to describe the continuous variables.For categorical variables, the absolute and relative frequency.The Table 1.Description of the secondary variables studied.

Variable Characterization
1. Sex Male or female.

Age
Age in years at the time the vest was made.

Side of the curve
According to the location of the convexity of the main curve: right or left.

Apex of the main curve
Vertebra or disc furthest from the midline belongs to the main curve's convexity.After defining the apex of the main curve, the Scoliosis Research Society (SRS) topographic classification was used 8 : thoracic (T2 to T11-T12 disc), thoracolumbar (between T12 and L1), lumbar (L1-L2 disc to L4-L5 disc).

Location of curves
Defined according to the topographic classification of the SRS8 and the side of the curve, subdivided into right thoracic, left thoracic, right thoracolumbar, left thoracolumbar, right lumbar, and left lumbar.

Type of curve
According to the number of structured curves: single (one curve), double (two curves), and triple (three curves).

RESULTS
Tables 2 and 3 describe the characteristics of the sample studied.In this study, females predominated (81.97%), with the convexity of the curve to the right (57.38%).The apical vertebra was located in the thoracic region in 45.9% of patients, Risser category A in 59.02%, and double curve in 54.10%.The average age of the participants was 13.1 years.
Grade I vertebral rotation was predominant both before and after treatment.(Table 4) Table 5 shows the frequency distribution of the variables studied according to categories I and II-IV of the Nash and Moe classification before using the 3D vest.The average age did not differ between the categories, with an average of 12.8 ± 1.6 in category I and 13 ± 1.9 in categories II-IV (p=0.196).The apex of the curve in the thoracic region predominated in rotation category I, while in categories II-IV, there was no predominance in the location of the apexes in the thoracic, thoracolumbar, and lumbar regions.Table 6 shows the frequency distribution of the variables studied according to categories I and II-IV of the Nash and Moe classification after using the 3D vest.
Table 7 compares the change in classification before and after wearing the vest (reduced: III, IIIII, IVIII, IVII; remained or increased: II, III, IIII, IIIIV).The average age of the patients who had reduced spinal rotation was 13.8 ± 1.9, while the average age of those who had no change or increased the degree of rotation was 12.7 ± 1.6, with a statistically significant difference (p-value = 0.018).
Table 8 shows that of the 25 patients classified as category II-IV before using the 3D vest, 16 had a reduction in the degree of vertebral rotation after using the 3D vest and were now classified as category I, representing 64% of the patients (p=0.012).And of the 36 patients who were in Category I, four (11.1%) moved to Category II-IV.

DISCUSSION
The purpose of 3D vests is to correct scoliosis in all three planes of the deformity. 4,6,11The correction in the axial plane seems to be the most notable feature of these vests, differentiating them from the Boston and Milwaukee vests.Freitas Junior et al., in a study of 138 patients treated with the 3D vest, demonstrated the corrective capacity in the coronal plane but did not evaluate the impact of these vests on rotation. 8Other studies corroborate the effectiveness of these vests in the conservative treatment of scoliosis with curves between 20-45 degrees in terms of the magnitude of the curve measured by the Cobb degree in the frontal plane.Still, no study to date has demonstrated the effect of vertebral rotation of these vests in the treatment of scoliosis. 1,12his study evaluated the effect of the 3D vest on spinal rotation in a retrospective analysis involving 61 patients, with the measurement of the degree of rotation assessed by the Nash and Moe classification as the main outcome.The Nash and Moe system is the most widely used method for assessing vertebral rotation in daily orthopedic practice. 13The results showed that 64% of patients categorized as grade II-IV significantly reduced the degree of vertebral rotation, indicating a possible defeat effect in curves with higher degrees of vertebral rotation (p=0.018).On the other hand, in patients with grade I, 11.1% of them had an increase or no change in vertebral rotation.The data collected in this study did not allow us to identify the possible causes of increased or unchanged vertebral rotation.The progression of rotation or absence of change in grade I can be attributed, albeit speculatively, to the low reliability of the Nash and Moe classification, to a possible initial progression, or the failure of treatment with the vest in this group.
This study has limitations.This is a retrospective study in which the main event studied was vertebral rotation, the assessment of which undergoes variations related to image quality, anatomical variations of the scoliotic vertebrae, and factors inherent to the reliability of the Nash and Moe classification. 13Intra-and inter-observer  variations in the classification are only known in controlled radiographs taken on biomechanical test specimens. 13Furthermore, this study did not compare the defeating effect of the 3D vest with the Boston or Milwaukee vests.Another important limitation was the one-off assessment of the vest's immediate defeating effect on the first control X-ray after starting treatment.The study suggests some defeating effects on turns with higher degrees of rotation while wearing the vest.Although this immediate defeating effect is positive in the conservative treatment of scoliosis, nothing can be concluded about its long-term effect, especially after you stop using it.It is unknown whether the gain in the rotation is definitive or transitory, nor the importance of rotational control with the 3D vest in the long-term results of conservative scoliosis treatment.The authors of this study are conducting a long-term line of research aimed at analyzing the results after discontinuing the use of the vest.
Comparative prospective studies are needed to shed light on this relatively new form of conservative treatment for scoliosis.

Figure 1 .
Figure 1.T10 apical vertebra was marked before and after using the vest, and the change from II to I in the Nash and Moe classification was observed.Chi-Square test and Student's t-test were used to evaluate the change in classification.The analyses were carried out using Stata software version 16, and the tables were prepared using Microsoft Excel software (2019).

Table 2 .
Descriptive characteristics of the sample profile (categorical variables).

Table 3 .
Descriptive characteristics of the sample profile (continuous variables).

Table 4 .
Distribution of vertebral rotation frequencies before and after treatment according to the Nash and Moe classification.

Table 5 .
Frequency distribution of the variables studied according to categories I and II-IV of the Nash and Moe classification before using the 3D vest.

Table 6 .
Frequency distribution of the variables studied according to categories I and II-IV of the Nash and Moe classification after using the 3D vest.

Table 7 .
Change in Nash and Moe classification before and after wearing the 3D vest.