Impact of visual and somatosensory deprivation on dynamic balance in adolescent idiopathic scoliosis

Do adolescents with different types and degrees of idiopathic scoliosis curves differ in postural control compared to their healthy peers? a cross-sectional study

BACKGROUND

Numerous scoliosis research studies have investigated postural control changes in adolescents with idiopathic scoliosis and compared them to healthy controls. However, the results have been controversial. Therefore, the present study aimed to compare whether postural control in adolescent idiopathic scoliosis (AIS) patients is different from their age-matched healthy counterparts.

METHODS

An exploratory cross-sectional study was conducted comprising 121 adolescents (11 to 17 years) divided into five groups, including those diagnosed with idiopathic scoliosis (n = 95) and healthy control peers (n = 26). According to the type (single or double), location (thoracic or lumbar), and severity (mild = Cobb's angle ≤ 25°, moderate = 26° ≤ Cobb's angle ≥ 45°) of AIS, the groups included: group 1: mild single curve in the thoracic region, group 2: mild single curve in the lumbar region, group 3: mild double curves, group 4: moderate double curves, and group 5: healthy control. Computerized Dynamic Posturography (CDP)/ /NeuroCom International, Inc., Clackamas, OR, USA was used to assess the postural control parameters. The assessment included the Sensory Organization Test (SOT), the Adaptation Test (ADT), the Motor Control Test (MCT), the Weight-Bearing Squat test (WBS), and finally the Unilateral Stance Test (UST).

RESULTS

The study analyzed data from 121 participants (36 boys, 85 girls) across five groups. No significant differences were found between the AIS and control groups concerning the type of curve or when comparing single and double curves. A one-way ANOVA indicated that variables related to the SOT were normally distributed, while other tests did not show normal distribution. Comparisons controlled for BMI, curve type (single or double), and severity of the major curve revealed no significant differences in postural control variables between AIS and control groups. Notable p-values include SOT 1 (p = 0.964), SOTstrategy 1 (p = 0.192), SOT 2 (p = 0.733), SOTstrategy 2 (p = 0.497), SOT 3 (p = 0.057), SOTstrategy 3 (p = 0.693), MCT (p = 0.089), USleftOpen (p = 0.087), and USrightOpen (p = 0.057).

CONCLUSION

This study's findings indicated that there were no statistically significant differences in postural control when performing activities of daily living among adolescents with idiopathic scoliosis compared to their healthy aged-matched peers. Therefore, there is no need for additional training to improve postural control in these adolescents with idiopathic scoliosis. However, the importance of identifying the postural control mechanisms in these populations is considerable for treating scoliosis.

Postural control and shoulder rotators isokinetic strength in squash players with and without idiopathic scoliosis

Idiopathic scoliosis is a postural deformity of the spine that not only changes the shape of the spine but may also alter postural control and muscle strength. Although this deformity is more common in some sports, it is not known whether the scoliosis athlete's balance and strength are altered. Balance and strength are essential to perform complex technical movements and prevent injuries. This cross-sectional study compared postural control and isokinetic strength of shoulder rotator muscles in squash players with and without idiopathic scoliosis and the control group. We report a higher mediolateral stability index in the frontal plane in scoliosis athletes and this may be associated with increased variability in postural control in the frontal plane. Additionally, the peak torque of the shoulder rotators was not different between the groups. While the relationship between function and posture is complex, these results provide information for preventive health care interventions in scoliosis athletes.

Neurophysiological, balance and motion evidence in adolescent idiopathic scoliosis: A systematic review

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a spinal deformity that affects approximately 4% of the world's population. Several hypotheses regarding the etiology of AIS have been investigated. In the last decades, impaired visual-spatial perception, alterations in spatial body orientation and sensory integration deficits have been documented.

OBJECTIVE

We aimed to summarize the neurophysiological, balance, and motion evidence related to AIS published in the last fifteen years, between January 2008 and April 2023. Both observational and interventional studies were considered. Only studies using quantitative assessment methods, such as electroencephalography (EEG), electromyography (EMG), magnetic resonance imaging (MRI), somatosensory evoked potentials, force platform, or motion capture, were included.

METHODS

1250 eligible records identified from online database searching were filtered by duplicate removal, title and abstract screening, and qualitative analysis. 61 articles met the inclusion criteria (i.e., Cobb range 10°-35°, age range 10-18 years) and were summarized.

RESULTS

We found significant evidence of impaired standing balance in individuals with AIS who greatly rely on visual and proprioceptive information to stay upright. EMG studies frequently reported an increased activity on the convex side of the intrinsic spinae muscles. EEG data show increased delta and theta power, higher alpha peak frequencies, and significant suppression in the alpha and beta bands in subjects with AIS during standing tasks. MRI studies report changes in white matter structures, differences in the vestibular system, and abnormal cortical activations over motor-related areas in subjects with AIS. Bracing appears to be an effective treatment for AIS, leading to improvements in static balance and gait. Methodological issues prevent reliable conclusions about the effects of other treatment options.

CONCLUSIONS

This review underscores the importance of quantitative assessment methods to explore the etiology and pathophysiology of AIS. Further research is needed to measure the impact of physical therapy and orthotic treatments on the neurophysiological mechanisms of the disease.

A scoping review of the different types of exercise programs proposed for the improvement of postural balance in adolescents with idiopathic scoliosis

BACKGROUND

Adolescent idiopathic scoliosis (AIS), which is the most common type of scoliosis, is a progressive disease that occurs in children aged 10-16 years. Abnormal curvature in AIS provokes spinal asymmetry of the upper body alignment and might deteriorate postural balancing and control ability.

OBJECTIVE

To evaluate the effect of exercise interventions on balance and postural stability in patients with adolescent idiopathic scoliosis.

METHODS

Embase, Scopus, Pubmed (Medline) and Web of Science databases were searched using the terms idiopathic scoliosis, physiotherapy, and balance. The articles selected were published in English in peer-reviewed journals from 2012 to July 2022.

RESULTS

Ten studies met the inclusion criteria. The PEDro scale values ranged from 2 to 6 (mean, 3.6), indicating a low level of scientific rigor. In the sample studies, spinal stabilization exercises were most often trialed (n= 3), followed by Schroth's exercise (n= 2), stretching and self-elongation exercise (n= 2), the exercise protocol of Blount and Moe, physiotherapeutic scoliosis-specific exercise, and proprioceptive neuromuscular facilitation exercise (all n= 1).

CONCLUSIONS

Physical therapists will be able to apply hippotherapy, Schroth exercise, physiotherapy scoliosis-specific exercise, trunk stabilization, proprioceptive neuromuscular facilitation exercise, spinal stabilization exercise, core stabilization exercise, and body awareness therapy to manage balance impairments in patients with adolescent idiopathic scoliosis, and further studies are needed to provide stronger evidence.

The evaluation of static and dynamic postural balance in children with thoracic hyperkyphosis

BACKGROUND

To investigate how postural balance is affected by thoracic hyperkyphosis compared to healthy children and elucidate the relationship between balance and strength and tightness.

METHODS

A cross-sectional analysis using standardized measures to identify balance function in children with thoracic hyperkyphosis (n = 31) and compare age-matched healthy children (n = 31). Primary outcome measurements were performed for the static and dynamic balance with the biodex balance system and limits of stability with the functional reach test. Secondary outcome measurements were strength with a hand-held dynamometry, tightness with the length test of pectoralis minor and hip flexors, and the sit-reach test for hamstrings. Mann-Whitney U test was used to compare the difference between the groups. Spearman's correlation was used to analyze the possible correlations between balance and strength and tightness.

RESULTS

A significant difference was found between the groups for static balance with eyes closed (except double-leg stance anteroposterior stability index) and for the forward reach distance (p < 0.05). Strength and tightness were significantly different in children with thoracic hyperkyphosis than in healthy children (p < 0.05). Also, it was found that muscle strength of trunk extension and hip abduction and tightness of hip flexors and hamstring were factors associated with static balance with eyes closed (r > 0.10, p < 0.05).

CONCLUSIONS

Static balance in children with thoracic hyperkyphosis is affected when visual input is particularly removed, and static balance with eyes closed is correlated with changed strength and tightness in some of the trunk and lower extremity muscles.

Comparison of two periods of Schroth exercises for improving postural stability indices and Cobb angle in adolescent idiopathic scoliosis

BACKGROUND

Adolescents with idiopathic scoliosis present postural instability when compared with healthy subjects. Although Schroth exercises therapy (SET) is broadly utilized, its effect on postural stability is still not clear.

OBJECTIVES

To compare the two treatment periods of the SET for improving the postural stability indices and Cobb angle, and to examine the correlation between the Cobb angle and stability indices in adolescent idiopathic scoliosis (AIS).

METHODS

Twenty girls aged 10-16 years with AIS (study group) and 20 age-matched girls without AIS (control group) were examined. The Biodex Balance System was used to evaluate the overall stability index (OSI), anteroposterior index (APSI), and mediolateral stability index (MLSI) in the study group before SET and one and three months after the therapy. A plain X-ray was used to measure the Cobb angle before and three months after SET. Stability indices and Cobb angle were measured only once for the control group.

RESULTS

One-way repeated-measures ANOVA revealed that the three-month duration of SET was the most effective for improving OSI, APSI, and MLSI (p< 0.001). The significant proximities of OSI, APSI, and MLSI to the normal values post three months of SET were 29.65%, 24.07, and 20% respectively. The MLSI was robust and correlated with the Cobb angle (r= 0.85) three months post intervention.

CONCLUSION

Stability indices and Cobb angles were highly improved after three months of SET compared to one month among AIS patients. The MLSI is the most substantial index correlated with the Cobb angle.

A 10-Week Program of Combined Hippotherapy and Scroth's Exercises Improves Balance and Postural Asymmetries in Adolescence Idiopathic Scoliosis: A Randomized Controlled Study

Introduction: The most frequent type of spine abnormality throughout adolescence was adolescent idiopathic scoliosis (AIS). Hippotherapy improved posture, balance and gait of different musculoskeletal conditions. Therefore, this study aims to see how hippotherapy combined with Schroth exercises affected postural asymmetry and dynamic balance in AIS compared to traditional physiotherapy (Schroth exercises) alone. Materials and methods: In this randomized controlled trial, fifty-two patients with AIS (10–18 years, 37 girls and 15 boys) participated. They were arbitrarily allocated into two groups: experimental (19 female/8 male; aged 14.74 ± 1.79 years; Cobb angle 18.59 ± 2.66 degrees) and control (18 female/7 male; aged 15.04 ± 1.81 years; Cobb angle 19.32 ± 2.69 degrees) groups. Both groups received Schroth exercises for 10 weeks, three days/week. The experimental group additionally received hippotherapy training. Pre-treatment and post-treatment assessment for the scoliotic, kyphotic angle, pelvic obliquity, pelvic torsion and vertical spinal rotation and the anteroposterior, mediolateral and overall stability indices were assessed using the formetric system 4D and Biodex Balance System, respectively. Results: After intervention, both groups illustrated significant improvements in all examined variables (p < 0.05). The experimental group illustrated significant improvements in scoliotic angle, kyphotic angle, pelvic obliquity, pelvic torsion and vertical spinal rotation and the stability indices compared to the control group (p < 0.05). Conclusion: In adolescence idiopathic scoliosis, hippotherapy training combined with Schroth exercises improves posture asymmetry and balancing ability more effectively than Schroth exercises alone.

Impact of the Vestibular System on the Formation and Progression to Idiopathic Scoliosis: A Review of Literature

The physiopathogenesis of adolescent idiopathic scoliosis remains unknown. However, a multifactorial pathogenesis is being assumed. Besides biomechanical, biochemical, and genetic factors, some studies have focused on congenital or acquired abnormalities in the vestibular organ with consecutive development of scoliosis. This study aims to analyze a possible correlation between any vestibular organ congenital or acquired pathologies and scoliosis based on the current literature. Therefore, we conducted a literature search in three databases, with search terms such as “scoliosis,” “organ of balance,” “idiopathic scoliosis,” “vestibular organ,” “spine,” and “balance.” Fifteen studies were selected and used for research. The relationship between scoliosis and vestibular organ abnormalities was recorded from all included works. Seven studies demonstrated a direct correlation between vestibular organ anatomical abnormalities and the form of the scoliotic spine. Another study confirmed the influence of the pathology of the vestibular organ on scoliosis but questioned whether it had an impact on the formation or the progression of the curvature. Others demonstrated a temporal overlap of the embryonic development of the vestibular organ and the beginning of pre-scoliotic characteristics, but their relationship remained questionable. In three studies, the correlation remained unclear, and any context has been denied. It seems unlikely that an isolated vestibular disorder can trigger structural scoliosis. However, the vestibular system pathologies may certainly occur in the multifactorial genesis of idiopathic scoliosis. Whether the correlation refers to the expression or the progression of scoliosis or may even have an influence on both remains unclear. New treatment options could be derived from these findings with a positive influence on the course of the deformity.

Effect of Postural Control Demands on Early Visual Evoked Potentials during a Subjective Visual Vertical Perception Task in Adolescents with Idiopathic Scoliosis

Subjective visual vertical (SVV) judgment and standing stability were separately investigated among patients with adolescent idiopathic scoliosis (AIS). Although, one study has investigated the central mechanism of stability control in the AIS population, the relationships between SVV, decreased standing stability, and AIS have never been investigated. Through event-related potentials (ERPs), the present study examined the effect of postural control demands (PDs) on AIS central mechanisms related to SVV judgment and standing stability to elucidate the time-serial stability control process. Thirteen AIS subjects (AIS group) and 13 age-matched adolescents (control group) aged 12–18 years were recruited. Each subject had to complete an SVV task (i.e., the modified rod-and-frame [mRAF] test) as a stimulus, with online electroencephalogram recording being performed in the following three standing postures: feet shoulder-width apart standing, feet together standing, and tandem standing. The behavioral performance in terms of postural stability (center of pressure excursion), SVV (accuracy and reaction time), and mRAF-locked ERPs (mean amplitude and peak latency of the P1, N1, and P2 components) was then compared between the AIS and control groups. In the behavioral domain, the results revealed that only the AIS group demonstrated a significantly accelerated SVV reaction time as the PDs increased. In the cerebral domain, significantly larger P2 mean amplitudes were observed during both feet shoulder-width-apart standing and feet together standing postures compared with during tandem standing. No group differences were noted in the cerebral domain. The results indicated that (1) during the dual-task paradigm, a differential behavioral strategy of accelerated SVV reaction time was observed in the AIS group only when the PDs increased and (2) the decrease in P2 mean amplitudes with the increase in the PD levels might be direct evidence of the competition for central processing attentional resources under the dual-task postural control paradigm.

Balance and gait performance of scoliotic subjects: A review of the literature

INTRODUCTION

Scoliosis is one of the common spinal deformities and considered as lateral curvature of the spine. Scoliosis lead to changes in the synergy between body segments, spinal anatomy, left-right trunk symmetry and cause pathological gait pattern [1,4,5-7]. Scoliosis is a structural deformity, so it can alter center of mass (COM) position and weight distribution on lower limbs. This suggests that scoliotic patients show the poorer stability rather aged match normal group. It was controversial that scoliosis influences the balance and gait performances, and also the effects of brace on these parameters. Therefore, it was aimed to evaluate the available literatures on balance and gait of scoliotic subjects.

MATERIALS AND METHODS

We conducted a search via PubMed, Google scholar and ISI web of knowledge to identify studies on scoliosis field and the effect of this deformity on kinetic and kinematic parameters as well as the influence of bracing on mentioned parameters. Some key words such as kinetic, kinematic, gait, stability, and walking were used in combination with scoliosis. The publication dates of the full-length articles were between 1998 and 2014. Down and Black tool was used to evaluate the quality of the articles.

RESULTS

Our multiple Medline searches led to the find out 54 papers that 26 of which were relevant based on title and abstract. Based on their references, we retrieved 6 more articles. We ultimately included 31 articles in this literature review. The number of studies regarding the influence of brace on kinetic and kinematic parameters in scoliotic subject was small. Based on the results of various studies, there is no correlation between gait pathology and scoliotic curve direction, no difference between stability of scoliotic and normal subjects and no difference between range of motions of lower limb joints in scoliotic subjects while walking with and without orthosis.

CONCLUSION

There was a not sufficient robust evidence to judge about the influence of scoliosis deformity on kinetic and kinematic parameters. However, it should be emphasized that use of orthosis may influence the symmetry of gait and improve standing stability in adult with idiopathic scoliosis.

Lower Muscle Mass and Body Fat in Adolescent Idiopathic Scoliosis Are Associated With Abnormal Leptin Bioavailability

STUDY DESIGN

This was a case-control study.

OBJECTIVE

This study aimed to investigate the body composition and its correlation with leptin and soluble leptin receptor (sOB-R) levels in girls with adolescent idiopathic scoliosis (AIS) and compared with healthy controls.

SUMMARY OF BACKGROUND DATA

Patients with AIS are associated with lower body weight, taller stature, lower body mass index (BMI), and deranged bone quality. Despite the widely reported lower BMI and body weight in girls with AIS, the body composition of these patients was not thoroughly studied with sufficient sample size. Leptin is an important factor in regulating energy and bone metabolism, and has been postulated as one of the etiologic factors of AIS.

METHODS

One hundred forty-eight AIS and 116 control girls aged 12 to 14 were recruited. Body composition was measured with bioelectrical impedance analysis. Caloric intake and physical activity level were assessed by food frequency and Baecke questionnaires respectively. Serum total leptin and sOB-R levels were measured with enzyme-linked immunosorbent assay, and free leptin index was calculated.

RESULTS

AIS girls had lower body weight and BMI, other anthropometric and sexual maturity parameters were comparable with controls. There were no difference in caloric intake and physical activity levels. After adjustment for physical activity level, AIS girls had lower skeletal muscle mass, lower body fat, and %body fat. Higher sOB-R and lower free leptin index were found in AIS girls after adjusted for age and body weight. Weaker correlations between serum total leptin, FLI, and body composition parameters were observed in AIS girls.

CONCLUSION

Results suggested that the lower body weight in AIS girls was contributed by both lower skeletal muscle mass and lower body fat. Altered leptin bioavailability also exists in AIS girls and could lead to lower body weight, lower BMI, and abnormal body composition that were manifested in AIS simultaneously.

LEVEL OF EVIDENCE

4.

Effects of Indoor Rowing Exercise on the Body Composition and the Scoliosis of Visually Impaired People: A Preliminary Study

Objective

To evaluate the effects of rowing exercise on body composition, laboratory data, fitness and scoliosis in visually impaired people. The majority of visually impaired people do not participate in active sports due to efficiency and safety issues. Rowing is a safe whole-body exercise with aerobic and anaerobic components.

Methods

Twenty subjects were recruited from among those admitted to a facility for visually impaired people (16 men and 4 women). Laboratory data, body composition, physical fitness, Cobb's angle, and fall index were checked before and after 6 weeks (5 days a week) of indoor rowing using Concept2 Model E.

Results

After the training, fat mass and total body fat percent decreased significantly. In the fitness test, back strength and trunk flexion score increased significantly. Laboratory data showed significant increases in serum protein and albumin and decreases in low-density lipoprotein (LDL) cholesterol. There were 9 subjects with scoliosis and after the training Cobb's angle decreased by 1.11°±1.55°, though this was not statistically significant.

Conclusion

Visually impaired people frequently have abnormal body composition, low physical fitness, and scoliosis. A rowing exercise program can be helpful, with a positive effect on body composition and physical fitness; however, with respect to scoliosis, we need an earlier intervention program in visually impaired people.

Adolescent idiopathic scoliosis and spinal fusion do not substantially impact on postural balance

BACKGROUND

The spinal curvature in patients with Adolescent Idiopathic Scoliosis (AIS) causes an asymmetry of upper body postural alignment, which might affect postural balance. However, the currently available studies on balance in AIS patients are not consistent. Furthermore, it is not known whether potential deficits are similar between patients with single and double curves. Finally, the effects of a corrective posterior spinal fusion on postural balance have not yet been well established.

METHODS

Postural balance was tested on a force plate, in 26 female subjects with AIS (12-18 years old; preoperative Cobb-angle: 42-71°; single curve n = 18, double curve n = 6) preoperatively, at 3 months and 1 year postoperatively. We also conducted a balance assessment in 18 healthy age-matched female subjects. Subjects were tested during quiet double-leg standing in four conditions (eyes open/closed; foam/solid surface), while standing on one leg, while performing a dynamic balance (weight shifting) task and while performing a reaching task in four directions.

RESULTS

AIS subjects did not demonstrate greater COP velocities than controls during the double-leg standing tasks. In the reaching task, however, they achieved smaller COP displacements than healthy controls, except in the anterior direction. AIS patients with double curves had significantly greater COP velocities in all test conditions compared to those with a single curve (p < 0.05). For the AIS group, a slight increase in COP velocities was observed in the foam eyes closed and right leg standing condition at 3 months post surgery. At 1-year post surgery, however, there were no significant differences in any of the outcome measures compared to the pre-surgery assessment, irrespective of the curve type.

CONCLUSIONS

Postural balance in AIS patients scheduled for surgery was similar to healthy age matched controls, except for a poorer reaching capacity. The latter finding may be related to their reduced range of motion of the spine. Patients with double curves demonstrated poorer balance than those with a single curve, despite the fact that they have a more symmetrical trunk posture. Postural balance one year after surgery did not improve as a result of the better spinal alignment, neither did the reduced range of trunk motion inherent to fusion negatively affect postural balance.

Effects of visibility and types of the ground surface on the muscle activities of the vastus medialis oblique and vastus lateralis

[Purpose] The purpose of this study was to compare the effects of visibility and types of ground surface (stable and unstable) during the performance of squats on the muscle activities of the vastus medialis oblique (VMO) and vastus lateralis (VL). [Subjects and Methods] The subjects were 25 healthy adults in their 20s. They performed squats under four conditions: stable ground surface (SGS) with vision-allowed; unstable ground surface (UGS) with vision-allowed; SGS with vision-blocked; and UGS with vision-blocked. The different conditions were performed on different days. Surface electromyogram (EMG) values were recorded. [Results] The most significant difference in the activity of the VMO and VL was observed when the subjects performed squats on the UGS, with their vision blocked. [Conclusion] For the selective activation of the VMO, performing squats on an UGS was effective, and it was more effective when subjects’ vision was blocked.

Idiopathic scoliosis and the vestibular system

PURPOSE

Despite its high prevalence, the etiology underlying idiopathic scoliosis remains unclear. Although initial scrutiny has focused on genetic, biochemical, biomechanical, nutritional and congenital causes, there is growing evidence that aberrations in the vestibular system may play a role in the etiology of scoliosis. In this article, we discuss putative mechanisms for adolescent idiopathic scoliosis and review the current evidence supporting a role for the vestibular system in adolescent idiopathic scoliosis.

METHODS

A comprehensive search of the English literature was performed using PubMed ( http://www.ncbi.nlm.nih.gov/pubmed ). Research articles studying interactions between adolescent idiopathic scoliosis and the vestibular system were selected and evaluated for inclusion in a literature review.

RESULTS

Eighteen manuscripts of level 3-4 clinical evidence to support an association between adolescent idiopathic scoliosis (AIS) and dysfunction of the vestibular system were identified. These studies include data from physiologic and morphologic studies in humans. Clinical data are supported by animal model studies to suggest a causative link between the vestibular system and AIS.

CONCLUSIONS

Clinical data and a limited number of animal model studies suggest a causative role of the vestibular system in AIS, although this association has not been reproduced in all studies.

How 'idiopathic' is adolescent idiopathic scoliosis? A systematic review on associated abnormalities

Background

Despite more than a century of dedicated research, the etiology and pathogenesis of adolescent idiopathic scoliosis (AIS) remain unclear. By definition, ‘idiopathic’ implies an unknown cause. Nevertheless, many abnormalities concomitant to AIS have been described, often with the suggestion that these abnormalities are related to etio-pathogenesis. Insight in the concomitant abnormalities may assist in improving the understanding of the etiological pathways of AIS. We aimed to systematically review and synthesize available studies on abnormalities concomitant to AIS.

Methods

Original studies comparing untreated AIS patients with healthy adolescents on abnormalities other than the deformity of the spine were retrieved from PubMed and Embase. We followed PRISMA guidelines and to quantify the relationship between each abnormality and AIS we used a best-evidence-syntheses for relating risk-of-bias to consistency of effect sizes.

Results

We identified 88 relevant citations, forty-seven carried high risk-of-bias and twenty studies did not report quantitative data in a sufficient manner. The remaining twenty-one publications failed to report data from before initiation of the deformity and blind assessments. These cross-sectional studies provided data on fourteen abnormalities concomitant to AIS. With our best-evidence-syntheses we were unable to find both strong evidence and a consistent pattern of occurrence for AIS and any of these abnormalities. From moderate risk-of-bias studies a relatively consistent pattern of occurrence for AIS and impaired gait control (4 studies; 155 subjects; Cohen’s d = 1.00) and decreased bone mineral density (2 studies; 954 subjects; Cohen’s d = −0.83) was found. For nine abnormalities a consistent pattern of occurrence with AIS was found, but the evidence for these was weak.

Conclusions

Based on the available literature, strong evidence is lacking for a consistent pattern of occurrence of AIS and any abnormality. The relevance for understanding the multifactorial etiology of AIS is very limited.