Proper posture provides the best balance and body stability at minimal muscular effort. It is constantly controlled by the central nervous system, which integrates the stimuli from the proprioceptors (deep feeling sensors), vision receptors, and balance receptors through the subcortical structures. The main purpose of the study was to describe single stance stability and its correlation with the degree of scoliosis and trunk rotation among patients suffering from idiopathic scoliosis and in the control group without scoliosis. The study included 80 patients (69 girls and 11 boys) and 40 healthy children without scoliosis (21 girls and 19 boys). The Cobb angle technique was used to determine the magnitude of the deformity. All subjects were divided into three subgroups according to Bogdanov’s classification. Single stance stability with eyes open and eyes closed was assessed with an electronic postural station—Delos Postural Proprioceptive System (DPPS). In case of multiple group comparisons for variables with normal distribution ANOVA with Scheffe, post hoc test was used or Kruskal-Wallis test was used as the nonparametric equivalent. The relationship between the two continuous variables was investigated using either Pearson product-moment correlation or Spearman’s rank correlation. In all these calculations, the statistical significance level was set to
Proper posture provides the best balance and body stability at the minimal muscular effort. It is constantly controlled by the central nervous system (CNS), which integrates the stimuli from the proprioceptors (deep feeling sensors), vision receptors, and balance receptors through the subcortical structures [
Still, even the slightest disturbance in the action of any of the above systems may affect the whole process of postural control and human balance. The process which regulates postural and body balance reflexes may also be affected by scoliosis.
Idiopathic scoliosis is a three-dimensional deformation of the spine. In the sagittal plane, it involves either increased or decreased physiological curvature of the spine; in the frontal plane, vertebrae are inclined to the side; and in the transverse plane, vertebrae are rotated. In spite of developing diagnostic tools and advanced medical and surgical treatment of scolioses, the ethology of the condition still remains unknown. Research indicates a significant contribution of the CNS in the etiology of scolioses [
The aim of the study was to determine the postural control index, the proprioceptive control index, and the role of visual information during unipodal support in patients with idiopathic scoliosis. The hypothesis in this study states that the degree of scoliosis and trunk rotation correlates with the indexes of postural stability and proprioception in patients with idiopathic scoliosis. The occurrence of three-dimensional deformation of the spine has been significantly related to the deterioration of the body balance parameters.
The postural control system was assessed on 120 subjects: the study group of 80 patients with scoliosis (69 girls and 11 boys) aged 11-18 (average age: 13.96; SD 1.80) and the control group of 40 healthy children (21 girls and 19 boys) aged 11-18 (average age: 14.11; SD 2.08). The characteristics of the subjects are summarized in Table
Subject characteristics.
Variables | Study group | Control group | |||||
---|---|---|---|---|---|---|---|
Girls | Boys | All subjects | Girls | Boys | All subjects | ||
69 | 11 | 80 | 21 | 19 | 40 | ||
Age (years) | >0.05 | ||||||
Risser sign | — | — | — | — | |||
Height (cm) | >0.05 | ||||||
Body weight (kg) | >0.05 | ||||||
Body mass index (kg/m2) | >0.05 |
Values are
Inclusion criteria to the study group were idiopathic scoliosis with a Cobb angle between 10 and 55 and no previous spine surgery or other musculoskeletal disorder.
Exclusion criteria both for the study and control group were the subjects with nervous system diseases, sensory integration disorders, condition after lower limb fractures, and injuries in the year preceding the study or with lower limb abbreviations. Moreover, subjects with any posture defects and scoliosis were also excluded from the control group.
The number of study participants was determined on the basis of a pilot study on 24 people with idiopathic scoliosis, whose body posture control results have been compared to the standards specified by the device producer. The 40 age-matched control children were recruited from surrounding schools in Gdańsk (primary schools, junior and senior high schools). The study group was divided into three subgroups according to Bogdanov’s classification (Table
Group characteristics according to the value of the primary curve among 80 patients with idiopathic scoliosis according to Bogdanov.
Variables | Scoliosis value (°) | ||
---|---|---|---|
<20 | 20-40 | 41-60 | |
No. of subjects (%) | 21 (26) | 47 (59) | 12 (15) |
Cobb angle of the |
Values are
Characteristics of the participants from the study group in relation to the angle of trunk rotation (
Variables | Study group | ||
---|---|---|---|
Group 1 | Group 2 | Group 3 | |
Range of ATR value (°) | ≤5 | 6-10 | ≥11 |
No. of subjects (%) | 18 (23) | 46 (58) | 15 (19) |
ATR value: the angle of trunk rotation; values are
A mean value of Cobb angle was
The subgroups were homogenous with respect to the subjects’ age,
A mean value of trunk rotation at the level of the apical vertebra of the primary curve was
The study group was diagnosed in a physical examination followed by an X-ray examination in the posterior-anterior view (P-A) obtained in standing position. The Cobb angle technique was used to determine the magnitude of the deformity, involving measuring the angle between the lines parallel to the border vertebral bodies of the structural curve [
Delos Postural Proprioceptive System: (a) the postural proprioceptive station; (b) wooden research station (Delos Equilibrium Board); (c) DVC vertical controller (Delos Vertical Controller); (d) vests used for DVC fastening (material from the “Wyspa” Therapy Center in Gdańsk, Poland).
Delos Postural Proprioceptive System makes it possible to evaluate the posture control system while standing on one leg with eyes alternately open and closed and allows for controlled training of posture stability and the balance of lower limbs, spine, and pelvis, using visual feedback elements. The single stance test (SST) was conducted with the subjects standing on the left leg first and then on the right, with the eyes open and closed. SST comprised six trials, 20 s each (two trials with open eyes (OE) and four with closed (CE)). Elements of the postural stability control system Delos enable to assess the deep feeling in the extremity tested by means of the static wooden station DEB (Delos Equilibrium Board), electronic postural reader DVC (Delos Vertical Controller) applied on the subject’s sternum, and a metal bar with infrared sensor DPA (Delos Postural Assistant) for support in case of lack of postural control (see Figure
The stability index (SI) was determined by the trunk inclination on the grounds of the assessment of postural instability and is capable of ranking all kinds of performances from the highest to the lowest level. SI is a score from 0 to 100 percentage [
A high value of the proprioceptive control index is characteristic of a proper balance, maintained during single-leg standing without visual control. A decrease in the proprioceptive control system manifests at first by the increase in the amplitude of the postural cone (PIxy) and next by the increase in applying the precautionary strategy, i.e., supporting by leaning against the bar. Afterward, if such need exists, the amount of necessary support is increasing and the amplitude of the postural cone decreases. This situation can occur during trials with both closed and open eyes. The stability index during the trial with closed eyes is the result of the effectiveness of the proprioceptive system, even though the simultaneous activation of the vestibular system cannot be excluded [
In the statistical description of quantitative data, classical measures of location such as arithmetic means and median and measures of variation such as standard deviation and range were used. The normality of distribution of the variables and variance equality of a studied feature in groups were tested by the use of appropriate Shapiro-Wilk’s test and a variance equality test. In order to compare groups in pairs for quantitative data,
The obtained results indicate significant differences between the mean of the postural control index SI OE (stability index in trials with eyes open) and the mean of the proprioceptive control index SI CE (stability index in trials with eyes closed) in the control group (
A slight but significant difference was observed in the result of SI OE between the control and the study groups,
Graphical comparison of the mean stability index between the control and the scoliosis (study) group. SI OE: stability index in trials with open eyes/postural control index; SI CE: stability index in trials with closed eyes/proprioceptive control index.
Depending on the scoliosis angle measured according to the Cobb angle technique and Bogdanov classification (
However, irrespective of the fact whether the eyes were open or closed, the scoliosis degree according to the Bogdanov classification did not have influence on the decrease in stability indexes,
Graphic comparison of the mean values of the stability indexes in the groups with open and closed eyes. SI OE and SI CE with respect to scoliosis value according to Bogdanov. SI OE: the stability index in open eyes trials; SI CE: the stability index in closed eyes trials.
Relationships examined by Spearman rank correlations did not indicate significant correlations between ATR and SI OE (
The diagram of correlation between ATR index and the mean stability index in the closed eyes trials (
Table showing multiple variables SI OE and SI CE in the study group with scoliosis divided with respect to the value of the angle of the trunk rotation. Three groups distinguished depending on the angle of trunk rotation: I, II, and III. Group I: ≤5° ATR, group II: 6-10° ATR, and group III: ≥11° ATR.
Variables | Group I | Group II | Group III | (pI, pII, pIII) |
---|---|---|---|---|
SI OE | (NS, NS, NS) | |||
SI CE | (NS, <0.05, <0.05) |
SI OE: the stability index in open eyes trials; SI CE: the stability index in closed eyes trials; pI: group I vs. group II; pII: group I vs. group III; pIII: group II vs. group III; NS: not significant.
The single stance test was aimed at determining the value of the stability index in patients suffering from idiopathic scoliosis and in the control group. Moreover, the authors attempted to examine the influence of the magnitude of scoliosis determined by the Cobb angle technique and the angle of trunk rotation on the functioning of the postural control system in the subjects. Test results may allow to determine these clinical variables which could affect the postural control system functioning. A hypothesis was made that among patients with diagnosed scoliosis, the postural control index and the proprioceptive control index were significantly lower compared to those without scoliosis. What is more, the degree of scoliosis and grade of trunk rotation correlate with the deterioration of the level of the indexes.
In literature, there has been a growing interest in the study of systems responsible for balance and control of body posture. According to Dayer et al., irregularities in posture control concern primarily the vestibular and the proprioceptive systems and usually occur during their maturation [
The fact that the single-limb support period accounts for 80% of the gait cycle at normal walking speed while the double-support period accounts for 20% [
In our study, the postural control system was assessed in single-leg support with eyes alternately open and closed. The stability index of EO trials was taken as an indicator of postural control while the stability index of EC trials was considered an indicator of proprioceptive control and of its effectiveness as the primary stabilizer of posture.
According to Riva, it is sufficient to conduct a static single stance test to evaluate the postural strategy responsible for restoring the disturbed body balance and determine compensation mechanisms [
Other authors also believe that only performing a one leg test (itself) allows the functional assessment of the body control system. Haddas et al. searched for cone of the economy (CoE) during functional balance tests (Romberg’s with eyes opened) in a group of adult degenerative scoliosis (ADS) patients [
Because idiopathic scoliosis causes deformations of the body artery and, as many studies indicate, affects body balance [
The primary findings of our study are as follows:
In this study, statistical differences were found between the study group and control group in the mean postural control index and proprioceptive control index between the test and control groups. However, for the trials with eyes closed, the difference was much larger and could indicate deterioration of proprioceptive sensation. The results presented in the work indicate a significant reduction in proprioceptive sensation among patients diagnosed with idiopathic scoliosis. The proprioception index was significantly lower, comparing with people without curvature of the spine, which could indicate that proprioception is not the dominant mechanism in the body posture control process in this group of patients. Our results indicate that for patients with scoliosis, the body schema, which is based on a properly functioning proprioceptive system, is disturbed. Patients may experience disturbances in the sense of the mutual arrangement of body elements and the movement of its sections against each other. Thus, exercising without eye control may not be effective. We would like to draw the readers’ attention to the fact that proprioception disorders may extend the time of rehabilitation and reduce its effectiveness. Exercises should be performed with the controlled body position not only by the person doing exercises but also by the physiotherapist and the patient’s parents. Proprioception disorders increase the role of the parent in the process of conservative rehabilitation of scoliosis. It is also important to provide adequate visual feedback on body positioning during exercise, for example, using mirrors. Moreover, according to the authors [ The authors of the study were unable to obtain statistically significant differences in the level of indexes of postural control and proprioceptive control in the subjects, depending on the value of the angle of scoliosis determined by the Cobb angle technique. The scoliosis magnitude does not determine the decrease in stability indexes. However, all patients presented a significant overall difference in results between the mean value of the stability index for open and closed eyes. The differences between the stability index levels in OE and CE trials inform about the influence of visual dependence on postural control. It was observed that patients with scoliosis showed a significantly higher dependence on the use of visual system in the body posture control process, which would point to an extremely important role of visual information in maintaining posture stability. Vision, whose major function is maintaining a relatively good balance with eyes open, may not be a sufficient component in the postural control. Impaired vision or any movement performed without the control of vision may result in a fall and injury. Moreover, regaining balance without visual control may be carried out inappropriately. Improving stance stability based on proprioceptive reflexes and with decreased visual dependence is crucial in preventing falls
Discrepant results were observed by Haumont et al. who observed that the amplitude of spine deformity in adolescent idiopathic scoliosis was a significant factor affecting the posture parameters [
On the other hand, the results presented by Assaiante et al. show that the occurrence of spinal curvature does not affect the control of vertical orientation and body stabilization strategies in the group of patients with scoliosis [
Given the above article, we believe that drawing the right conclusions from many studies is only possible if the conditions under which the tests are conducted are harmonized. The fact whether the test is conducted under static or dynamic conditions, or position included standing on one or both limbs, can significantly affect the test results. The standardization of the study conditions is noticed by Dalleau et al., who, as in the present study, also proved that in the group of girls with scoliosis during quiet standing, there is a greater variation in the location of the foot pressure center compared to girls without scoliosis [ No correlation was observed between the value of the ATR and the level of index of postural control with eyes open. For patients with scoliosis, appropriate postural control is obtained during single-leg standing with eyes open when the visual component used to maintain balance is greater. However, the authors of this study observed a significantly negative correlation between the level of index of proprioceptive control (single-leg standing with eyes closed) and the grade of trunk rotation examined by means of Bunnell scoliometer during the test of forward bending (ATR)
Testing torso rotation by means of a Bunnell scoliometer allows for objective assessment of a child’s growing spine, and early detection of its rotation relative to the longitudinal axis of the body prevents further progression of scoliosis [
In this study, we determined parameters of the postural control in relation to the alterations in the spine curvature disorders: the severity degrees of deformity and trunk rotation magnitude. The location of the curvature and the number of arches in the curvature could also contribute to the deterioration of the equilibrium parameters. Therefore, further studies should be extended to identify the influence of AIS type on the postural stability control. In addition, most patients with scoliosis were conservatively treated during the study. It should be checked in the long run whether the undertaken treatment and its type (kinesiotherapy, braces) improves proprioception.
Furthermore, the study group has a predominant number of girls; hence, the conclusions of the study cannot be transferred to children of both sexes, but rather to the female population. Nevertheless, scoliosis affects girls more often.
Significantly lower values of the stability index during single-leg standing with eyes closed indicated balance impairment which is mainly connected with inadequate functioning of the proprioceptive system. The character of these alterations is much influenced by the degree of spine rotation. The level of scoliosis according to the Bogdanov classification does not affect the level of SI OE and SI CE. Thus, the value of rotation of the trunk may be a factor considerably aggravating proprioceptive control. Therapeutic activities aiming at reducing the angle of the trunk rotation may result in the improvement of the person’s balance.
The date used to support the findings of this study may be released upon application to the Department of Rehabilitation Medicine, Medical University of Gdansk, who can be contacted at Aneta Dąbrowska;
The authors declare that they have no conflict of interest.