Short-Term Benefit from Core Stabilization Exercises in Adolescent Idiopathic Scoliosis: A Meta-Analysis of Randomized Controlled Trials

Background . Idiopathic scoliosis may afect adolescents’ physical development. Tis systematic review and meta-analysis determined the efectiveness of core stabilization exercises in improving clinical symptoms of idiopathic scoliosis in adolescents. Methods . We searched PubMed, the Cochrane Library, and Embase for randomized controlled studies investigating core stabilization exercise and idiopathic scoliosis. Two investigators independently extracted data based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting guidelines. Te Newcastle–Ottawa Scale (NOS) was used to evaluate the quality of the selected literature and we performed a meta-analysis to assess the clinical utility of core stabilization exercise for the improvement of patients with idiopathic scoliosis. Heterogeneity was assessed with the I 2 statistic. Results . Tis systematic review and meta-analysis included 9 studies. Tree of the studies revealed that core stabilization exercise improved Cobb’s angle (SMD: − 1.06, 95% confdence interval (CI): ( − 1.41, − 0.72), and P < 0 . 001) in adolescents’ idiopathic scoliosis, but the subgroup analysis showed no signifcant diference in Cobb’s angle in the thoracic and lumbar segments (SMD: − 0.25, 95% CI: ( − 0.55, 0.04), and P � 0 . 89). In the angle of trunk rotation subgroup analyses (SMD: 0.35, 95% CI: ( − 0.01, 0.72), and P � 0 . 33), there was no signifcant diference before and after core stabilization exercise treatment. Conclusions . Te results showed a very short-term efect of core stabilization exercise on patients with idiopathic scoliosis. However, this study contains a relatively short period of research and more long-term research is needed in the future to support this conclusion


Introduction
Adolescent idiopathic scoliosis (AIS), which is a spinal deformity disease caused by unknown etiological factors during the growth and development of adolescents aged 10-16 years, has become one of the common diseases endangering the pathology of adolescents [1].Regarding age at onset, it has been reported that about 80% of the individuals with scoliosis had onset in adolescence and the deformity appears during the sudden growth period before puberty [2].Te prevalence of AIS is 0.47-5.2%,and the incidence and severity of spinal curvature are higher in girls than in boys worldwide [3].With the development of the body, the degree of spinal deformity increases and makes the patient exhibit signifcant stooping and hunching of the back.AIS has a certain efect on the clavicular angle, pelvic inclination angle, and Cobb's angle and could even decrease the lung function of the patient [4].Except in extreme cases, AIS does not usually cause health problems; however, surface deformities have a negative impact on adolescents and may lead to psychological disorders [5].Te severity of AIS is divided into mild, moderate, and severe, with mild Cobb's angle being less than 25 °, moderate being between 25 °and 45 °Cobb's angle degrees, and severe being greater than 45 Cobb's angle degrees [6].Te larger the Cobb's angle, the higher the functional limitations in adulthood [7].Currently, the most efective nonsurgical treatment of AIS is bracing, exercises have an important role as an adjunct modality that can be added to the brace treatment and it only should be considered for AIS curves of less than 20 °, and for curves of higher than 20 °, bracing and exercise is indicated for this population [1].Moreover, recent report has shown that bracing is also efective for curves of higher than 40 °(40-60 °) [8], while severe AIS tends to be treated by surgery [9] and artifcial disc replacement may beneft to patients with previous long fusion for scoliosis surgery [10,11].Terefore, it is recommended that AIS be treated as early as possible.
Exercise is a common conservative approach to correcting the curvature of the spine for AIS.It is considered an important method of maintaining spinal function and preventing the pathogenic development of scoliosis [12,13].Tere are a variety of exercise training approaches to improving AIS, with the most studied of these being the Schroth exercise; however, the study fndings are contradictory [14].In contrast, most other exercise training studies are merely retrospective and fail to report compliance, intention-to-treat analyses, or blind evaluators [15].Tus, there is presently a controversy regarding exercise therapy and a lack of high-quality evidence as to whether AIS can be treated with exercise therapy [6].
Core stabilization (CS) exercises have recently been used in the conservative treatment of AIS [16].CS exercises have been reported to improve local and overall spinal stability by improving muscle imbalances, particularly between the paraspinal muscles and multiple muscle groups [17].Increasing spinal stability is one of the main treatment goals of the CS exercises approach to scoliosis.It focuses on spinal stability and core strength, training the deep trunk muscles by controlling the trunk position during static posture and functional activities [18].It has been found that CS exercises are more efective than traditional exercise in improving spinal stability, lowering Cobb's angle and reducing pain scores in AIS [19].However, not much research has been performed in depth on CS exercises for adolescent scoliosis and the efectiveness is unclear.Terefore, it is necessary to verify the efcacy of CS exercises in AIS based on recently published studies and we elucidated the very-short efect of the CS exercises on AIS by a comprehensive meta-analysis.

Methods
Tis systematic review and meta-analysis was conducted in line with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [20] and targeted the following PICO question: after undergoing CS exercises, to what extent is AIS improved in AIS patients?CS exercises training consist of three stages.Te frst phase is to activate the core muscles to improve proprioception and muscle coordination in the spinal region, and in the second and third phases, the intensity of the exercise is increased to improve muscle stability and endurance [21].

Search Strategy.
A literature search was conducted in relevant databases including PubMed, Embase, and the Cochrane Library up to September 16, 2022.We selected the Medical Subject Headings (MeSH) terms, and keywords "scoliosis" and "exercise" and their synonyms to search these databases (see Supplementary Table 1 for the complete search strategy).Two of these investigators (RC and JZ) coded all characteristics of the selected studies separately for this metaanalysis (see Supplementary Table 2).Tey assessed the risk of bias independently by using Cochrane's risk of bias tool 2.0 [22], which includes randomization processes, assignment hiding, blinding, data integrity, and selective reporting.For each domain, the risk of bias was judged as being low risk or unclear (see Supplementary Figure 3).All discrepancies were resolved through discussion prior to data analysis.

Outcomes of Interest.
Te frst primary outcome of interest is Cobb's angle; this point was chosen to account for the efect of CS exercises, which is the most used value to quantify spinal deformity [23].Te other outcomes of interest were the angle of trunk rotation (ATR), Walter Reed Visual Assessment Scale (WRVAS), and Scoliosis Research Society 22 Questionnaire (SRS-22) in order to compute efect sizes.

Statistical Analysis.
Te strength of the correlation between the main efect and subgroup analyses was assessed by estimating the standardized mean diference (SMD) and 95% confdence intervals (CIs) through a random efects model (DerSimonian and Laird methods).P < 0.05 was considered a statistically signifcant diference.Tese data were analyzed in Stata 16.0 (Stata Corp, College Station, TX, USA).

Characteristics of the Included Studies for Meta-Analysis.
Te selection of eligible studies is shown in Figure 1.Our initial computer literature search identifed 3926 results in all.After a thorough review of titles and abstracts, 995 of these records were found to be duplicates.Ultimately, we identifed 9 studies for meta-analysis (Figure 1).Te characteristics of these included studies are listed in Table 1.Tis meta-analysis investigated the efect of CS exercise training on the improvement of AIS patients, with outcome indicators including Cobb's angle and trunk rotation angle.

Meta-Analysis of CS Exercises and the Angle of Trunk
Rotation.Two studies investigated the association between CS exercises and the thoracic ATR, and all of the reported results suggested that CS exercise training may not improve the ATR (SMD and 95% CI: 0.35 (−0.01, 0.72) and P � 0.33, Figure 4) with low with heterogeneity (I 2 � 3.78%).

Discussion
Our meta-analysis found that CS exercises had a very shortterm efect to reduce Cobb's angle and improve lumbar muscle strength in AIS patients compared with conventional training in three studies [7,25,26]; however, the subgroup analysis showed no signifcant improvement [16,27,28].Te subgroup analysis of the efects in Cobb's angle was divided into thoracic and lumbar segments.Te results showed no signifcant diference in the improvement of Cobb's angle before and after CS exercises, possibly because there was no signifcant improvement in the thoracic or lumbar segments alone, presumably in relation to the degree of deformity and the duration of exercises.Two studies suggested that CS exercise training may not improve the ATR [29,30]; another three studies showed no improvement in the WRVAS (Supplementary Figure 1) [29][30][31] or SRS-22 (Supplementary Figure 2) [16,29,30].Te most likely reason for these results is the short duration of the CS exercises.Terefore, in the present study, we investigated the efect of CS exercises on the treatment of patients with scoliosis by meta-analysis.We included nine relevant studies and found that it has a very short-term efect to improve deformity symptoms in scoliosis patients.Tis result implicates that CS exercises may be very short-term efective in patients of scoliosis.
To our knowledge, this is the frst meta-analysis to analyze the efect of CS exercise training on the treatment of AIS.Te reduction and prevention of scoliosis deformities is currently the main goal in the treatment of patients with AIS.Terefore, numerous clinicians and investigators have tried to fnd new ways to reduce scoliosis deformities and to elucidate the efciency of these treatments [32].In recent years, diferent exercise methods have been tried to improve  the symptoms of deformity caused by AIS and some supporting studies have been published on patients with AIS [33].
Exercise treatments for AIS include Schroth exercise, functional individualized therapy, and the Scientifc Exercise Approach to Scoliosis (SEAS) [34].Studies have found that Schroth exercise is a recommended treatment for patients with scoliosis and that it may be more benefcial to AIS patients with a Cobb's angle of 10 ∼ 30 °than for AIS patients with a Cobb's angle greater than 30 ° [16].One of the studies found that Schroth exercises are more efective than CS exercises in the correction of scoliosis and related problems in mild adolescent idiopathic scoliosis and CS exercises are more efective than Schroth exercises in the improvement of peripheral muscle strength [29].Our study found that CS exercises were not as efective as Schroth exercises in improving Cobb angle; however, this was the conclusion of only one single study.
However, there is limited research evidence on the effcacy of exercise training, and there is no defnitive evidence on which exercise is more efective.Although some studies have confrmed that Schroth exercise training can be effective for the treatment of scoliosis, the level of evidence for this is not very high [23].Te improvement of Cobb's angle has been an important target for the development of goals and plans for patients with AIS.North American standards recommend that patients with a Cobb's angle of 10-25 °should be observed for curve changes before deciding whether to start treatment aggressively; for patients with a Cobb's angle between 25 °and 45 °, conservative treatment such as bracing and exercise is recommended; bracing is a common nonsurgical technique that allows clinicians to prevent and correct malformations or injuries of a patient's spinal column, and it can be used as a conservative measure in the initial stage, as an adjunct to surgery, or as a defnitive treatment [35].One of the studies showed that CS exercises with bracing and scientifc exercises approach to scoliosis with bracing had similar efects in the short-term treatment of moderate adolescent idiopathic scoliosis [27].For other patients with a Cobb's angle greater than 45 °, surgical treatment is recommended for correction [36].
CS exercises may increase the strength of spinal muscles, improve the quality of life, and relieve pain in adolescents with AIS [19] and could correct the bad posture of scoliosis patients, which may be related to the balance of the electromyographic activities (convex concave side) of paravertebral muscles in AIS patients [7].CS exercises were more efective than traditional exercises alone in the correction of vertebral rotation and reduction of pain in adolescent idiopathic scoliosis [16].However, the literature included in our study was not observed for a long time, so it has been suggested that exercise therapy for AIS patients should be continued for at least 6 months or longer [37] so that the efect on Cobb's angle would be greater.Among the literature included in this study were those on CS exercises to improve pulmonary function.Yildirim [24] found that after 8 weeks of CS exercises, it was possible to increase the respiratory function of the children, making no statistical diference between their respiratory function and that of healthy controls, but that after other stretching, strengthening, breathing, and core training, although there was a signifcant improvement in the respiratory function parameters when they increased, they did not reach the values of the healthy controls.

Limitations of the Study.
Our investigation has several limitations.First, treatment of scoliosis is a long-term process that lasts approximately 2-3 years and should be followed up for at least 1 year.However, most of the studies which were included in this meta-analysis were relatively short-term, which probably makes our fndings relatively weak.Tere is no information about the follow-up duration of the exercise because the cases of some studies were schoolaged children to carry out the study without long-term follow-up and with a relatively small number of patients.More research needs to be performed diligently and should be followed up with long-term results.Second, more highlevel studies are needed to conduct more robust metaanalyses in the future.

Conclusion
In this study, we provided the impact of CS exercises on the treatment of patients with scoliosis through a meta-analysis.Te results showed a very short-term efect of CS exercises on patients with AIS.Tis study is the frst meta-analysis of the very short-term efect of CS exercises on patients with AIS and provides the basis for an evidence-based approach to exercise for patients with scoliosis.In conclusion, CS exercise may be a recommended treatment for patients with AIS.

Figure 1 :
Figure 1: Preferred Reporting Items For Systematic Reviews And Meta-Analyses (PRISMA) fow diagram of the literature search and study selection process.

Figure 2 :
Figure 2: Meta-analysis of Cobb's and CS exercises training.

Figure 3 :
Figure 3: Meta-analysis of subgroup Cobb's and CS exercises training.

Figure 4 :
Figure 4: Meta-analysis of ATR and CS exercises training.
Data Extraction and Quality Assessment.Two of our investigators (RC and JZ) independently retrieved the following data from each of the eligible studies: frst author, year of publication, country, sample size, age, percentage of women studied, exercise type, and Cobb's angle.

Table 1 :
Characteristics of the studies included in the meta-analysis.