Evaluation of Chêneau brace in the treatment of thoracic and lumbar adolescent idiopathic scoliosis with apical vertebral rotation

Abstract

BACKGROUND:

Adolescent idiopathic scoliosis (AIS) is a common structural disorder of the spine in adolescents, often associated with structural deformities in both coronal and axial positions. Apical vertex rotation (AVR) is one of the main indicators of axial deformity in patients with scoliosis. Currently, there are few studies on the impact of AVR in the treatment of AIS.

OBJECTIVE:

This study examined the influence of different AVR on AIS after brace treatment.

METHODS:

Data were collected from 106 AIS participants aged 11–16 years from the orthopedic outpatient clinic of the Second Hospital of Lanzhou University. Two orthopaedic professionals measured the Cobb angle, AVR and spinal mid-line offset before and after brace treatment, and descriptive and linear correlation analyses were used to determine the correlation between AVR and AIS measured parameters.

RESULTS:

(1) In AIS volunteers with the same AVR, the treatment effect of AIS with lumbar predominant curvature was higher than that of AIS with thoracic predominant curvature. The treatment effect tended to decrease with increasing AVR. (2) Spinal mid-line deviation was associated with AVR. For patients with AIS with I and II degrees of AVR, the treatment effect of spinal mid-line offset after bracing is better. For AIS patients with AVR III degrees and above, the degree of correction of spinal mid-line offset decreases with the continuous correction of Cobb angle.

CONCLUSIONS:

The efficacy of AIS was found to be related to the severity of AVR. The efficacy of AIS with predominantly lumbar curvature was significantly higher than that of AIS with predominantly thoracic curvature. The efficacy of treatment of mid-line spinal deviation also decreased with increasing AVR.

Keywords

Adolescent idiopathic scoliosis brace treatment Cobb angle apical vertebral rotation spinal mid-line deviation

1. Introduction

AIS is one of the common diseases of skeletal deformation in adolescents. Typically, scoliosis is defined as a bend of 10 ${}^{\circ}$ or more (Cobb Angle) [1]. Studies have found that the incidence at home and abroad is 2%–4%, and the proportion of women is higher than that of men [2]. The male to female ratio is about 1:4. Although the specific etiology of AIS has not been determined, the role of genetic factors in its development has been widely accepted [3]. Among adolescents aged 1–16 years, the incidence of AIS is 1%–3%, accounting for 74.7% of adolescent scoliosis [4]. The incidence of Cobb Angle $>$ 30 ${}^{\circ}$ was 0.2%, and the incidence of Cobb Angle $>$ 40 ${}^{\circ}$ was 0.1%. When the Cobb Angle was around 10 ${}^{\circ}$ , there was no significant gender difference in the incidence of AIS. However, with the gradual increase of Cobb Angle, when Cobb $>$ 30 ${}^{\circ}$ , the male and female incidence approached 1:10. Usually only about 10% of patients require therapeutic intervention [5]. Scoliosis is often accompanied by pathological phenomena such as three-dimensional curvature of the spine, vertebral and thoracic deformation, body asymmetry, proprioceptive dysfunction and motor imbalance [6], which sometimes have serious consequences and affect the life and health of patients.

AIS is mostly associated with a rotational deformity of the apical vertebral body. This axial deformity poses additional problems in the treatment of AIS patients, increases the treatment time and is accompanied by additional complications. For example, prolonged brace wear can lead to complications such as lumbar muscle atrophy, decreased muscle strength, low back pain, aggravated thoracic deformity, decreased pulmonary function, skin pressure sores, and allergies, which can have a significant impact on quality of life [7, 8], as well as reduced active muscle movement. Studies have demonstrated that long-term abstinence has a tendency to "shut down" the stabilizing muscles of the spine [9], leading to decreased quality of motion, muscle strength, and control of the neuromuscular system, which reduces quality of life and may lead to re-injury. In some cases, spinal motor dysfunction and abnormal body shape may occur, and in severe cases may lead to cardiopulmonary dysfunction, affecting the quality of life and healthy growth of children [10].

The common sites of AIS are the thoracic and lumbar segments of the spine. The improvement effect of AIS brace after treatment at different sites is different, and the treatment difficulty is also different. From the normal morphological structure of the spine, it can be found that AIS patients with scoliosis of the thoracic spine, due to their special bone structure, are affected by the frame or the structure of the thoracic spine, and when the force is larger, the cushioning force is larger. Patients with curved AIS, due to the absence of a special bone structure frame, will have a better effect of correction through treatment. With the change of time, the vertebrae of AIS patients will have different degrees of rotation, which has a great impact on the treatment of the orthosis. Therefore, we study the effect of the change of AVR on the treatment of AIS with orthoses, which can be a guide for future treatment.

In order to treat AIS with rotational deformity, we use the Cheneau brace with anti-rotational properties, created by the French physician Cheneau, also known as the CTM orthosis, which belongs to the TLSO class of orthoses, commonly known as the Xenu orthosis. It is indicated for the correction of idiopathic scoliosis in patients with a Cobb angle of less than 50 ${}^{\circ}$ below T6 and for the conservative treatment of other scoliosis patients, and is distinguished by a series of three-dimensional pressure pads for scoliosis curvature and torsion and a large release space for better correction of compression and rotation deformities.

2. Participants and methods

2.1 General information

All participants with adolescent idiopathic scoliosis who presented at the orthopedic clinic of the Second Hospital of Lanzhou University during 2021–2022 were invited to participate. All participating adolescents and their guardians were informed of the study and signed an informed consent form.

2.2 Inclusion criteria

(1) Adolescent idiopathic scoliosis patients must meet the indications for brace treatment; (2) The age of initial diagnosis was 9–16 years old; (3) AIS volunteers who choose a single main curvature Cobb angle between 12 and 45 degrees; (4) AIS volunteers who can wear braces regularly; (5) The case data and imaging data were complete, and the volunteers and them family agreed to receive bracing treatment [11].

2.3 Exclusion criteria

(1) Cannot follow visitors regularly; (2) Patients with chronic diseases such as congenital thoracic dysplasia and osteochondrosis that seriously affect the efficacy and quality of life of braces [12]; (3) Patients who are not willing to accept brace treatment; (4) Scoliosis patients with Cobb Angle $>$ 50 ${}^{\circ}$ ; (5) Adult scoliosis patients.

2.4 Measurement of Cobb angle [13]

Fully automatic measurements of axial vertebral rotation for assessment of spinal deformity in idiopathic scoliosis were conducted.

2.5 Measurement of mid-line deviation of the spine

The distance between the outermost edge of the apical vertebra and the line joining the seventh cervical vertebra and the mid-line of the sacrum was measured.

2.6 Measurement of apical vertex rotation of the spine

Nash Moe [14] was used to evaluate the rotation of scoliosis in clinic. The degree of rotation of the vertebral body was evaluated by observing and measuring the position changes of the pedicle on the convex and concave sides of the vertebral body in the anteroposterior film.

2.7 Statistical analysis

SPSS 22.0 software was used for statistical analysis. The measured data were expressed as mean $\pm$ standard deviation ( $x\pm s$ ). $T$ -test was used for comparison between groups, and $P<$ 0.05 indicated that the difference was statistically significant.

3. Results

3.1 The occurrence of AIS is related to gender and the location of scoliosis

A total of 106 adolescent idiopathic scoliosis patients (22 males and 84 females) were treated with the Chêneau brace in this study. The mean age was 13.7 $\pm$ 1.6 years. The average observation time is 8.72 $\pm$ 5.09 months. There were 56 cases in the thoracic spine and 50 cases in the lumbar spine. Cobb angles for thoracic principal curvature ranged from 12.5 ${}^{\circ}$ to 45 ${}^{\circ}$ , with a mean of 25.91 ${}^{\circ}$ $\pm$ 7.47. Cobb angles for lumbar principal curvature ranged from 14.5 ${}^{\circ}$ to 39.7 ${}^{\circ}$ , with a mean of 24.31 ${}^{\circ}$ $\pm$ 6.17 ${}^{\circ}$ . Thoracic parietal rotation: 20 patients with I degree AVR, 26 patients with II degree AVR, and 10 patients with III degree AVR. Lumbar parietal rotation: 14 patients with I degree AVR, 23 patients with II degree AVR, 8 patients with III degree AVR, and 5 patients with IV degree AVR.

AIS occurs mainly in adolescence, especially during puberty, and the incidence is different in males and females. As can be seen from Table 1, the ratio of males to females is approximately 1:4. The incidence of AIS varies in different parts of the spine, with the most common sites being the thoracic and lumbar regions of the spine.

Table 1
Basic information

Project	Type	Number
Years	13.7 $\pm$ 1.6
Gender	Male	22
	Female	84
Lateral bending parts	Thoracic curve	56
	Lumbar curve	50

3.2 The treatment effect of AIS at different sites varies after brace treatment

AIS usually occurs in the thoracic and lumbar segments of the spine. After stent treatment, it was found that AIS, which mainly focuses on thoracic curvature, has different therapeutic effects compared to AIS, which mainly focuses on lumbar curvature. A study [15] showed that changes in Cobb angle $>$ 5 ${}^{\circ}$ before and after treatment are considered effective treatment methods. Therefore, we conducted statistical analysis based on changes in Cobb angle $>$ 5 ${}^{\circ}$ before and after treatment. As shown in Table 2, we found that the overall treatment effectiveness of AIS with thoracic spine flexion as the main treatment was 51.78%, while the overall treatment effectiveness of AIS with lumbar spine flexion as the main treatment was 60%.

Table 2
Improvement rate of thoracic flexion and lumbar flexion in AIS after brace treatment

Main bending part	Number of people improving	Total number of people	Improvement rate %
Chest section	29	56	51.78
Lumbar section	30	50	60

3.3 The effectiveness of AIS treatment changes depending on the site of the scoliosis and the AVR

Due to the different vertebral structures in the different segments of the spine, the muscles and ligaments have different effects, which ultimately lead to different changes in the vertebral body. As seen in Table 3, the most common degrees of vertebral rotation in patients with AIS were 1 and 2 degrees. The percentage of 1 and 2 degrees was 82.14% in AIS with predominantly thoracic flexion and 74% in AIS with predominantly lumbar flexion.

Table 3
Improvement rates of thoracic and lumbar scoliosis with different degrees of rotation

Vertebral body	AVR	Improved number	Total number	Improvement rate
Thoratic	1 degree	12	20	60.0%
	2 degrees	13	26	50.0%
	3 degrees	4	10	40.0%
Lumbar	1 degree	10	14	71.4%
	2 degrees	16	23	69.6%
	3 degrees	3	8	37.5%
	4 degrees	1	5	20.0%

Table 4

Cobb angle changes after bracing in adolescents with thoracic flexion versus lumbar flexion of the AIS

Vertebral body	AVR	Cobb angle before treatment ( ${}^{\circ}$ )	Post-treatment Cobb’s angle ( ${}^{\circ}$ )	$P$ value
Thoracic	1 degree	25.82 $\pm$ 7.30	18.92 $\pm$ 5.81	${}^{**}$
	2 degrees	25.33 $\pm$ 7.44	20.62 $\pm$ 7.89	${}^{*}$
	3 degrees	27.58 $\pm$ 7.61	23.24 $\pm$ 6.79	0.11 $>$ 0.05
Lumbar	1 degree	20.88 $\pm$ 3.71	14.06 $\pm$ 2.63	${}^{***}$
	2 degrees	23.37 $\pm$ 5.48	16.64 $\pm$ 4.86	${}^{***}$
	3 degrees	28.69 $\pm$ 6.36	24.50 $\pm$ 6.37	$>$ 0.05
	4 degrees	31.24 $\pm$ 4.83	27.68 $\pm$ 5.82	$>$ 0.05

${}^{*}p<$ 0.05, ${}^{**}p<$ 0.01, ${}^{***}p<$ 0.001.

3.4 Cobb’s angle changes over time in patients with AIS

AIS will have different outcomes as the duration of bracing the brace increases, with improvement, worsening and stabilization. Most patients with AIS will improve after brace treatment. As seen in Table 4, when the AVR of AIS patients was I to II degrees, the Cobb angle improved after bracing the brace from 25.82 ${}^{\circ}$ $\pm$ 7.30 ${}^{\circ}$ to 18.92 ${}^{\circ}$ $\pm$ 5.81 ${}^{\circ}$ and 25.33 ${}^{\circ}$ $\pm$ 7.44 ${}^{\circ}$ to 20.62 ${}^{\circ}$ $\pm$ 7.89 ${}^{\circ}$ , respectively. The changes before and after treatment were statistically significant ( $P<$ 0.05). When the AVR was III degree, the Cobb angle decreased from 27.58 ${}^{\circ}$ $\pm$ 7.61 ${}^{\circ}$ to 23.24 ${}^{\circ}$ $\pm$ 6.79 ${}^{\circ}$ , and the overall scoliosis was relieved to some extent, but it was not statistically significant. Patients with AIS do not have specific skeletal structural limitations in the lumbar region, so the AVR of the vertebral body can reach higher degrees of rotation. Therefore, more patients with high AVR can be found in AIS with lumbar curvature in clinical practice. As can be seen in Table 4, patients with AIS with lumbar curvature treated with a brace have different AVR and different degrees of improvement after treatment. Among them, participants with AVR of degree I and II had a significant change ( $P<$ 0.05) in Cobb angle from 20.88 ${}^{\circ}$ $\pm$ 3.71 ${}^{\circ}$ to 14.06 ${}^{\circ}$ $\pm$ 2.63 ${}^{\circ}$ and 23.37 ${}^{\circ}$ $\pm$ 5.48 ${}^{\circ}$ to 16.64 ${}^{\circ}$ $\pm$ 4.86 ${}^{\circ}$ , respectively, after brace treatment, with a significant improvement in scoliosis treatment. Although volunteers with AVR of III and IV degrees showed a decrease in Cobb angle after brace treatment, the before and after treatment results were not statistically significant.

3.5 Correction of the AIS spinal mid-line offset is also associated with AVR

Figure 1.

Changes of the mid-line of the spine after the change of Cobb angle of different apical rotation degrees in AIS patients with thoracic curvature after brace treatment. The abscissa is the change of Cobb sangle, and the ordinate is the change of the mid-line of the spine.

Figure 2.

Changes of the mid-line of the spine after the changes of Cobb angle of different apical rotation in AIS patients with lumbar curvature after brace treatment. The abscissa is the change of Cobb angle, and the ordinate is the shift of the mid-line of the spine. A, B, C, and D show the apical vertebrae at degrees 1, 2, 3, and 4.

Figure 3.

X-ray graphs of AIS patients with different AVR mainly with thoracic curvature before and after brace treatment. A, B and C are the X-ray graphs with AVR of 1 degree, 2 degrees and 3 degrees.

Figure 4.

X-ray graphs of AIS patients with different AVR mainly with lumbar bending before and after brace treatment. A, B, C, and D are the X-ray graphs with AVR of 1, 2, 3, and 4 degrees.

In brace-treated AIS patients, deviations from the mid-line of the curve dominated by the thoracic and lumbar spine changed both before and after treatment. We found that the correction of the deviation of the spinal center (distance from the most distal spine to the spinal center-line) was related to the severity of AVR. Figure 1 shows the trend of change in Cobb angle and change in spinal center-line deviation in patients with AIS with predominantly thoracic curvature in different AVR after bracing (the horizontal coordinate is the change in the difference in Cobb angle before and after treatment, and the vertical coordinate is the change in the difference in spinal center-line deviation before and after treatment). The trend line equations for A, B, and C are Y $=$ 1.390 $*$ X $-$ 4.070, R ${}^{2}$ $=$ 0.5; Y $=$ 0.1170 $*$ X $+$ 5.075, R ${}^{2}$ $=$ 0.01; and Y $=$ 1.398 $*$ X $-$ 2.555, R ${}^{2}$ $=$ 0.46. It can be seen that there is a strong correlation between these two trends when AVR is degree I and III, 0.5 and 0.46, respectively. This indicates that in AIS patients with AVR degree I and AVR degree III, after bracing treatment, with Cobb angle was continuously corrected, the deviation of the spinal mid-line was also improved. Further analysis revealed that when the Cobb angle change was within 5 degrees, the correction of the spinal mid-line was small, basically within 10 mm. When the Cobb angle correction exceeded 5 ${}^{\circ}$ , a significant correction of the spinal mid-line of the AIS could be found. Figure 2 shows the trend of Cobb angle change and spinal mid-line offset in patients with AIS with predominantly lumbar curvature with different AVR after bracing. The trend line equations for A, B, C, and D when the AVR was degree I, II, III, and IV were Y $=$ 0.5124 $*$ X $-$ 0.4867, R ${}^{2}$ $=$ 0.12; Y $=$ 1.171 $*$ X $-$ 0.8486, R ${}^{2}$ $=$ 0.37; Y $=$ 2.007 $*$ X $-$ 4.537, R ${}^{2}$ $=$ 0.62; and Y $=$ $-$ 1.147 $*$ X $+$ 5.321, R ${}^{2}$ $=$ 0.26.The change in Cobb angle is closely related to the deviation of the spinal mid-line, especially in patients with 3rd degree AVR (R ${}^{2}$ $=$ 0.62). Patients with AIS with I, II and III degree AVR, after brace treatment, the Cobb angle keeps improving and the deviation of the spinal mid-line keeps corrected and tended to normalize. However, when the AVR reaches degree IV, the correction of the spinal mid-line becomes smaller and tends to deteriorate as the Cobb angle improves. Overall, it can be seen that brace treatment is effective when the change in Cobb angle is $>$ 5 ${}^{\circ}$ . Patients with AIS with low (1st and 2nd degree) AVR have a sustained increase in mid-line offset of the spine and improvement in coronal plane deformity. Patients with AIS with high (degree IV) AVR may present with exacerbation after prolonged brace wear.

AIS with different AVR has different changes after brace treatment, which we can see more visually from the radiographs of the patients. Figure 3 shows the chest flexion as the main AIS imaging pictures. A, B, C are the x-rays of the patients with AVR of degree I, II, and III AIS before and after treatment. From the imaging pictures, it is clear that patients with 1–2 degrees of AVR have a significant treatment effect, with significant improvement in Cobb angle and reduction in spinal midline deviation. Patients with grade 3 AVR have a poorer treatment effect, with little change before and after treatment. Figure 4 shows the imaging images of patients with AIS with predominantly lumbar bending. A, B, C, and D are AVR of degrees I, II, III, and IV, respectively. According to the pre- and post-treatment radiographs, it can be found that AVR of degrees I, II and III had a significant treatment effect with significant improvement of Cobb angle and reduction of spinal midline deviation. AVR of degree IV had a poor treatment effect and showed aggravation.

4. Discussion

Through our research, it has been found that different locations of scoliosis in adolescents and varying degrees of rotation of the top vertebrae can affect the therapeutic effect of braces. From Table 2, it can be seen that the treatment of AIS mainly focused on the lumbar spine is generally better than AIS mainly focused on the thoracic spine. Figures 1 and 2 show that the treatment of midline deviation of the spine is also different for AIS with different vertex rotations after brace treatment. It can be observed from Figs 3 and 4 that as the degree of vertebral rotation increases, the therapeutic effect of the brace decreases.

The rate of growth and development is the same on both sides of the normal spine. However, the growth of the two sides of the vertebral body in patients with scoliosis is different. According to Hueter Volkmann’s law [16], when the epiphyseal pressure increases, bone growth is inhibited, and when the epiphyseal pressure decreases, bone growth accelerates. Excessive pressure inhibits growth of epiphyseal plates, and tension between them accelerates their growth. As a result, the vertebral epiphysis on one side of the AIS patient is pulled and accelerated, while the epiphysis on the concave side of the AIS patient is suppressed, creating a vicious cycle of gradually expanding the Angle of the scoliosis. When scoliosis occurs, the pressure on the two sides of the vertebrae is different, the side that is pulled accelerates growth, and the side that is compressed, growth is inhibited, resulting in an increasing Cobb angle, and the different growth rates on the two sides affect the stability of the spine and aggravate the degree of scoliosis. Therefore, any factor that reduces the internal stability of the spine as well as the flexibility of the spine flexion increases the likelihood of scoliosis. These factors include neuromuscular and ligament problems, metabolic and chemical abnormalities, and harmful chemicals [17].

For AIS with skeletal dysplasia ranging in size from 20 ${}^{\circ}$ to 40 ${}^{\circ}$ with scoliosis, brace are still an ideal choice. The therapeutic effect of AIS combined with bracing varies in different parts, which may be related to the influence of surrounding skeletal structures, thoracolumbar ligaments and muscles, and intervertebral discs. In clinical practice, it is known that it is significantly larger and thicker than the vertebrae in the thoracic spine, and can withstand greater compression forces, thereby compensating for the compression and growth rate of the lumbar spine. Therefore, it can compensate for the compression of the lumbar spine, thereby reducing the growth rate of scoliosis and improving the correction effect. The strength of the surrounding ligaments also varies, which has a significant impact on bracing treatment. Due to the structure of the thoracic vertebrae, thoracic AIS is inherently less flexible and more prone to support disorders than lumbar AIS [19]. Ultimately, AIS with a focus on lumbar curvature will be more easily corrected, which is consistent with our research findings.

Upadhyay [20] and Kwan [21] noted that changes in AVR during orthotic wear are somewhat predictive of final outcome. Axial rotational correction within the stent can yield additional benefits as can coronal correction. This highlights the importance of AVR in AIS to predict the axial pattern of examination and reveals the effectiveness of brackets to produce greater rotational forces [22]. According to Figs 3 and 4, we found that AIS patients with AVR of I and II degrees showed significant improvement after bracing, while AIS patients with AVR of III degrees had no significant improvement effect. The treatment effect was obvious in AIS patients with AVR of I and II degrees for lumbar predominant AIS, and poor in AIS patients with AVR of III and IV degrees, and the change before and after treatment was not obvious. Therefore, the use of brace treatment for AIS patients with AVR of I and II degrees is obvious and should be encouraged, while the use of brace treatment for AIS patients with AVR of III and IV degrees needs to be determined on a case-by-case basis.

With further treatment of AIS with bracing, the mid-line offset of the spine changes. The position of the master curve and AVR are closely related to the changes in the mid-line deviation of the spine. As seen in Figs 1 and 2, when the AVR is lower rotation (I and II), the change in spinal mid-line deviation also increases, which means that the coronal plane deformity is corrected in AIS patients. However, in the case of high rotation of the AVR (III and IV degrees), the treatment is not effective and the deformity is aggravated. After studying the curve situation in Figs 1 and 3, we can observe that when the Cobb angle change is less than 5 degrees, the brace treatment for AIS mainly corrects the axial deformity, i.e., the rotational deformity of the spine. When the change in Cobb angle is more than 5 degrees, the correction of the offset of the spinal center-line is better, i.e., better treatment of coronal deformity. When the AVR is I to III degrees, the Cobb angle is continuously corrected, and the spinal center-line offset is continuously improved by bracing for a long time. When the AVR was IV degrees, the mid-line deviation of the spine tended to worsen. Based on this finding, we believe that it is necessary to wear orthoses to treat rotational deformities in AIS patients with low AVR. Therefore, in conclusion, for patients with low AVR, we recommend brace treatment. For patients with high AVR, bracing should be performed as appropriate and a specific response should be made according to the location of the AIS.

In adolescents with AIS, the spine is more flexible but less strong, more susceptible to external forces, and the scoliosis is easily corrected. As time changes, the flexibility of the spine decreases and the strength increases. In youth, the flexibility of the spine decreases, the strength increases, and the brace essentially does not work. When scoliosis occurs in adolescents, the flexibility and strength of the spine changes, which has implications for brace treatment. Adolescence is the most common period for AIS and the best time for AIS treatment. The therapeutic effect of orthoses by bracing them is positive. Roaf [23] proposed a vicious cycle of asymmetric loading in scoliosis, where (1) the pressure on the concave side of the curve increases and growth slows, and (2) the load on the convex side decreases and growth accelerates, leading to greater deformity and aggravating the asymmetric loading, perpetuating the cycle. Asymmetric loading leads to asymmetric spinal growth [24]. Therefore, when the point of action of the brace is on the side of the scoliosis, it slows the growth of the convex side and is effective in the correction of scoliosis.

Rotational deformities of the vertebral body occur primarily due to changes in the forces around the vertebral body, which ultimately lead to uneven forces around the vertebral body. Rotation of the vertebral body can distort and strain the ligaments around the spine, resulting in significant changes in tension and stress levels in the vertebral facet joints, dislocations and even fractures. Since the heart and lungs are in front of the thoracic vertebrae, the ligaments around the thoracic vertebrae will be subjected to two opposing forces. The resulting force will eventually make the thoracic spine rotate clockwise or counterclockwise, which mainly affects the adjacent vertebrae in the Sagittal plane movement. The difference in the force of the surrounding ligaments will carry the vertebrae through the movement changes, and will also lead to the rotation of the vertebrae to different degrees. The continuous superposition of the forces acting on the vertebrae will lead to the maximum force and maximum rotation of the apical vertebrae. The main role of the brace is to exert pressure on the convex side of the scoliosis, slowing its growth and development and relatively accelerating the growth of the concave side, gradually making the growth and development of both sides consistent and improving the scoliosis. However, when the vertebral body rotates, the position of the brace changes, the pressure on the convex surface is dispersed, and the effect is reduced. Therefore, patients with AIS with a higher degree of rotation are treated poorly and those with AIS with a lower degree of rotation are treated well. In terms of mechanical versus geometric torsion, vertebrae with a higher degree of rotation are subjected to greater tension on the small joints and ligaments, with greater pressure on the convex side and greater inhibition of growth and development; therefore, bracing is less effective and those with a lower degree of rotation are treated better. Ford [25] noted that all paravertebral muscles tested in adolescent scoliosis patients have significantly reduced muscle spindles, which would result in lower lumbar strength in scoliosis patients than in normal scoliosis patients, despite the effectiveness of brace therapy. Complications such as low back pain and discomfort and back sprains are more likely to occur than in normal individuals and can only be improved with long-term treatment. In scoliosis, a curved “beam” structure is formed [26]. In mechanical theory, the concave and convex surfaces are subject to different pressures and tensions, which are influenced by muscles and muscle forces. Therefore, the physiological curve of the spine is achieved by adjusting the balance of the muscles on both sides of the spine by maintaining the normal posture of the spine and pulling the muscles and ligaments contracted on the concave side to enhance the normal maintenance and correction [27]. Therefore, treatment of AIS with bracing results in adolescents with little difference in external performance from adolescents of the same age, but much lower strength around the spine than normal adolescents of the same age.

5. Conclusion

In conclusion, our study found that the therapeutic effect of bracing continued to decrease with increasing AVR. Participants with low degree (I and II) AVR were better corrected with brace treatment. The treatment effect of AIS with predominant lumbar flexion was better than that of AIS with predominant thoracic flexion. However, this study also had some drawbacks and we did not study the brace treatment in younger ( $<$ 9 years) as well as too old ( $>$ 18 years) adolescents, which needs our further study in the future.

Ethical approval

The study was approved by the Ethics Committee of the Second Hospital of Lanzhou University (project number: 2022A-669).

Informed consent

All participants and their guardians agreed to participate and signed an informed consent form.

Funding

The study was financially supported by the Special Fund Project for Doctoral Training Program of Lanzhou University Second Hospital (YJS-BD-09), the Lanzhou Talent Innovation and Entrepreneurship Project (2019-RC-140) and the Lanzhou Talent Innovation and Entrepreneurship Project (2021-RC-126).

Author contributions

LA and GX contributed to the data collection and paper writing and KJ, WZ, CH and LW assisted with the data analysis.

Footnotes

Acknowledgments

The authors are thankful for the data support from the Brace Center of Lanzhou University Second Hospital and the help from members of the group.

Conflict of interest

The authors have no conflict of interest to report.

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Evaluation of Chêneau brace in the treatment of thoracic and lumbar adolescent idiopathic scoliosis with apical vertebral rotation

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

2. Participants and methods

2.1 General information

2.2 Inclusion criteria

2.3 Exclusion criteria

2.4 Measurement of Cobb angle [13]

2.5 Measurement of mid-line deviation of the spine

2.6 Measurement of apical vertex rotation of the spine

2.7 Statistical analysis

3. Results

3.1 The occurrence of AIS is related to gender and the location of scoliosis

Table 1 Basic information

Table 2 Improvement rate of thoracic flexion and lumbar flexion in AIS after brace treatment

Table 3 Improvement rates of thoracic and lumbar scoliosis with different degrees of rotation

3.5 Correction of the AIS spinal mid-line offset is also associated with AVR

5. Conclusion

Ethical approval

Informed consent

Funding

Author contributions

Footnotes

Acknowledgments

Conflict of interest

References

Table 1
Basic information

Table 2
Improvement rate of thoracic flexion and lumbar flexion in AIS after brace treatment

Table 3
Improvement rates of thoracic and lumbar scoliosis with different degrees of rotation