Evaluation attempt of own body sensing amongst persons with and without scoliosis

1. Introduction

Adolescent idiopathic scoliosis (AIS) is a common structural spine deformity affecting 2–4% of adolescents, mainly between 10–18 years of age [1, 2]. Lateral curvature of the spine of 10 ∘ or more, often with a rotational component, is defined [3]. Advanced curvatures of the spine cause significant clinical and socioeconomic changes and usually require medical intervention [4]. Due to the unknown cause of idiopathic scoliosis, its therapy is a long-term and often unsatisfactory process. In 0.1% of patients with AIS, futile attempts to stop scoliosis progression end with surgical treatment [5]. Many hypotheses have been proposed to explain the etiology of scoliosis including genetic factors, skeletal growth, nervous system, and metabolic dysfunction [6]. By following the literature on the subject, one can notice more and more often appearing suggestions of authors who see problems related to the feeling of one’s own body as one of the causes of AIS. According to Pialasse et al., dysfunctional sensorimotor control is associated with the onset of scoliosis [7]. Also in the opinion of Herman et al., patients with scoliosis show perceptual disorders, deficits in sensorimotor adaptation and balance control [8].

The assessment of the quality of feeling your own body certainly gives the opportunity to personalize the therapeutic program. Despite the noticeable increase in interest in the subject of sensory processing among people with scoliosis, it should be emphasized that there is little research on this problem, and in addition these studies use advanced technologies that seem to be hardly available in physiotherapy rooms on a daily basis. That is why, in the presented work, short and simple tests were used to assess the feeling of one’s own body among people with and without scoliosis. Besides, Savvides et al. shows that individuals with idiopathic scoliosis have more concern about their body appearance than individuals without idiopathic scoliosis [9]. The aim of this study was thus to assess the feeling of one’s own body among children with and without scoliosis on the example of feeling the head position, pelvis shape and balance.

2. Material and methods

Fifty-five people took part in the study. They were patients of the FEDmed Center for the Treatment of Spinal Diseases in Kraków and volunteers who were students of schools who did not meet any of the exclusion criteria and volunteered for the tests.

The study group (SG) consisted of 30 people with scoliosis diagnosed on the basis of radiological examination, without any comorbidities and injuries that could affect the test results. The age of respondents ranged from 11 to 19 years, average age was 14.73 years ( ± 2.2). There were 25 girls and 5 boys in the study group. The group consisted of people with single-arch (11 people), two-arch (18 people) and three-arch (1 person) scoliosis. The minimum scoliosis value was 7 ∘ and the maximum was 53 ∘ . The average value was 25 ∘ ( ± 10.11 ∘ ).

The Adams Forward Bend Test was carried out among these people, during which the angle of trunk rotation (ATR) was measured with a scoliometer. The measurement was made on the top of primary curvatures, where the ATR had the highest value. The rotation angle ranged from 4 ∘ to 22 ∘ , averaging 10.82 ∘ ( ± 4.11 ∘ ) The bone age was also assessed for every participant with the use of the Risser classification. The lowest result was 2 and the highest was 5. The average value was 3.37 ( ± 0.8). Eleven people had compensated scoliosis and 19 had uncompensated scoliosis.

The control group (CG) consisted of 25 people without diagnosed scoliosis, diseases or injuries that could affect the test results. The age of the people in the control group ranged from 11 to 18 years, average age was 13.13 ( ± 2.05). There were 14 girls and 11 boys in this group.

The criteria for inclusion in the study were: age between 11–19, and diagnosis of scoliosis by a specialist, with the type specified and Cobb angle measured. Exclusion criteria included sight and hearing damage, neuromuscular disorders throughout the body, and previous musculoskeletal injuries that could affect test results.

The research was carried out from November 2018 to March 2019. The participants took part in the study in clothing that did not limit their movement and without footwear. During the study three functional tests were used: Cervical Joint Position Error Test, Clinical Test of Sensory Integration on Balance and Body proportion demonstration test.

Joint position sense (JPS) is described as the ability to relocate the natural head position without the assistance of vision [10]. The cervical joint position error test (CJPET) was used to test the position error of the joint [11]. To perform the test you need a “laser tracker” target, a headband with a laser mounted and a chair with a backrest. The chair is placed 90 cm from the shield. After the patient adopts the appropriate position and puts a laser band on the head, the examiner sets the laser so that the laser beam in the neutral position of the patient’s head falls on the center of the “laser tracker” target. The test consists of four movements: head turn left, head turn right, extension and flexion of the cervical spine. Movements are made with the eyes closed. The task of the examined person is to return to the initial (neutral) position of the head. Persons taking the test are informed that their movements are natural, without excessively increasing the range of motion. Six tests are performed for each direction. The patient may open his eyes between individual tests. Each time the examiner marks on the target a point, which according to the patient was the initial position of the head. Due to the fact that patients usually strive to achieve the result as close as possible to the center of the target, they are asked to open their eyes only after marking a point on the shield to avoid inadvertently correcting the position of the head. It is also worth noting that the room where the test is carried out was properly prepared. It was properly lit, so that the point of incidence of the laser beam can be read easily, and there were no people or objects in the room that could disturb the examined person’s concentration during individual movements, affecting the test results.

The acceptable error for this test is 1.5 to 2 inches (3.8–5.1 cm) from the center of the target. A distance greater than 2 inches (5.1 cm) is considered as incorrect. If most of the tests were outside the tolerable error, the test result in general is considered positive [12].

The Clinical Test of Sensory Integration on Balance (CTSIB) in equilibrium was created to assess the effect of the visual, vestibular and somatosensory systems on the posture control. The test consists of four stages: (1) Standing on a hard surface with your eyes open, (2) standing on a hard surface with your eyes closed, (3) standing on an unstable surface with your eyes open, and (4) standing on an unstable surface with your eyes closed.

During each stage, the test subjects stand upright with their feet together and the upper limbs crossed on the chest. A 10 cm foam sponge was used to create the unstable surface. The task of the patient is to stand still in each of the four conditions for 30 seconds. If a person during the test changed the position of the feet, upper limbs or opened their eyes when they were to be closed, the test was interrupted and repeated. A maximum of 3 attempts can be made at each stage. At the end of the test, the total duration of the test is counted. The body swing is also observed during the test. The norm for this test is to perform it in 120 seconds, with only one attempt at each stage. Repetition of any of the stages of the test is considered as an irregularity [13].

Body proportion demonstration test (BPDT) is based on assumption that even with closed eyes we should be able to demonstrate the proportions of the body, quite accurately determine the size of the foot or show the width of the pelvis [14]. The test consists in demonstrating the width of one’s own pelvis with eyes closed. Prior to the test, the examiner measures the actual pelvic width, between the anthropological ic (illiocristale) points, which are located most laterally on the iliac crests. The starting position is standing with the lower limbs in a natural setting and with the upper limbs lowered along the torso. Then, the patient is asked to demonstrate the width of the pelvis using the upper limbs and keeping eyes closed. The examiner then measures the size shown between the styloid processes of the radial bones. Each person is instructed to open his/her eyes only after taking the measurement to avoid correcting the size shown. It is also important that the person, when demonstrating the width of the pelvis, should not touch his/her hips, only show the width by stretching the upper limbs forward spontaneously, just as he/she feels.

A statistically significant difference was found between the study group and the control groups in all three tests.

People with diagnosed scoliosis perform significantly more tests that do not fall within the Cervical Joint Error Test standard (on average 15.13) than people without scoliosis (on average 4.92).

People with diagnosed scoliosis perform the Clinical Test of Sensory Integration on Balance in a significantly lower total time (118.68 s on average) than people without scoliosis (119.8 s on average). The average time of standing with open eyes was 30 s for both the test group and the control group on each of the surfaces. The average time of standing with closed eyes on a hard surface was 30 s for both groups, while for standing on an unstable surface it reflected 34.4 s for the study group and 30.8 s for the control group. People with diagnosed scoliosis show a significantly larger pelvis width (3.98 cm on average) than people without scoliosis (2.32 cm on average). It was also examined whether the test results of people with scoliosis are related to the size of their Cobb angles (Table 2) and ATR (Table 3). None of the tests showed any correlation between the results of the study group and the values of their Cobb angles and ATR.

4. Discussion

Among the many hypotheses and theories aimed at understanding the etiology of idiopathic scoliosis, there are those that emphasize the role of the nervous system. Veldhuizen, among others, points to evidence that scoliosis may be associated with neurological dysfunction [15]. This evidence appears to correlate with the anatomical structure. This author, after conducting research, showed differences in the thickness of the cerebral cortex associated with motor and vestibular functions as well as the volume of the cerebellum, between people diagnosed with scoliosis and people without scoliosis [4]. Geissele et al., in turn, based on magnetic resonance imaging of the brainstem of people with juvenile idiopathic scoliosis, recorded the existence of asymmetry in the abdominal part of the bridge or medulla [15]. In addition, Rousie et al. showed correlations between basic labyrinth measurements during MRI, labyrinth activity and lumbar scoliosis [16]. Pialasse et al. emphasize that multisensory integration depends on the proper maturation and functioning of the nervous system, impacting the balance control, among others [7].

Literature on the subject contain studies on the assessment of not only nerve structures, but also somatosensory functions in people with scoliosis. As one of the few, Le Berre et al. used three clinical tests to assess proprioception in people with AIS: “Fukuda-Utenbergerstepping test” to assess dynamic balance, as well as the “SharpenedRomberg test” and “Unipedal stance test” to assess the static balance. They examined 114 people with scoliosis, with an average Cobb angle of 35.7 ∘ . Their results revealed differences between the control group and people with AIS in the dynamic balance test. They found no significant differences between the study group and the control group in static balance tests. These authors suggested combining clinical tests with more advanced methods, including for ex. force platforms to evaluate both static and dynamic proprioception and confirm the validity of the tests performed. In addition, they recommend the dynamic proprioception test to be used as screening test for people exposed to scoliosis [17]. Kessen et al. also noted worse results of somatosensory assessment among people with AIS. The purpose of their research was to evaluate the precise position of the hands. The obtained results allowed them to find worse proprioception in the upper limbs of people with scoliosis compared to people without scoliosis [18].

The aim of this study was to assess the feeling of one’s own body among children with scoliosis and among children without scoliosis on the example of feeling the head position, pelvis shape and balance. The obtained results confirmed the existence of differences between the groups. The biggest differences concerned the feeling of head position (average score: SG – 15.13, CG – 4.92). The head is an essential part of the musculoskeletal system. Usually, research concerns the assessment of its spatial location. Many authors have shown that head abnormalities are often associated with e.g. the development and persistence of back pain syndromes [19] or change in breathing pattern [20]. Due to the large number of proprioreceptors located in the neck area [21] head position also has a significant relationship to balance [22]. Our research concerned assessing not the location but the feeling of one’s own position. Given the results obtained, we are convinced that not only the assessment of the head posture, but also the feeling of its location should be an important element of clinical assessment and not only in case of patients with scoliosis.

Maintaining balance depends on many factors. The most important are proprioception, vision and the vestibular system. The vestibular system is one of the structures that may be involved in the onset of scoliosis. This system is involved in torso muscle activation either by direct efferent projections to the spinal cord through the medial vestibulospinal tract or by collateral activity of the reticulospinal tract. Thus, abnormalities in this system could translate into inappropriate phasic or tonic torso muscle activities [23]. This may be an explanation for worse results in our next test. The presented research revealed that people with scoliosis had worse results in the Clinical Test of Sensory Integration on Balance (average time: SG – 118.68, CG – 119.8). These people had greater problems in maintaining balance when standing with their eyes closed on an unstable surface, which may indicate a disturbance in the processing of somatosensory or vestibular information. The research of Sahlstrand et al. is consistent with the results presented [24]. These authors examined the effects of eye closure and ground instability on keeping balanced by people with AIS. Their results showed that masking sensory inputs by standing on a 10 cm foam and closing the eyes increased the total swing area much more than in the control group. When proprioception is impaired, a big role is played by surrogate feedback, thanks to which it is possible to improve spatial sensation of the body. This biofeedback is possible thanks to information provided, among others, by well-functioning eyesight or hearing. This hypothesis has been confirmed by Catanzaritii et al. These authors showed in their research five times more frequent occurrence of scoliosis among the blind persons compared to the control group [18]. It can also be an explanation of the lack of differences between people with and without scoliosis in the results of the test with eyes open.

Atrial perception, very important in controlling balance, also plays an important role in perception of the vertical line [14]. Misconception of body verticality has been correlated with poor posture control [25]. These are the conclusions of Cakrt et al. [26], who examined a group of 46 people using the “buckedmethod” and demonstrated a significantly changed perception of the subjective visual vertical (SVV) in patients with AIS. In addition, people with scoliosis have been shown to have more frequent spontaneous nystagmus and greater sensitivity to caloric tests, which may also indicate abnormal functioning of their vestibular system [24, 26]. Studies on the response of patients with AIS to vibration stimuli are also very interesting. The results, however, are not conclusive. Wyatt et al. found that people with AIS have a lower proprioceptive threshold. Barrack et al. came to the same conclusions. The results obtained by McInnes et al. prove the opposite. According to these authors, people with scoliosis have a much higher vibration threshold. It should be emphasized, however, that these tests only assess the threshold of the proprioceptive system, while they do not show the ability to transform sensory perception into appropriate motor commands [24].

The cortical level of motor integration presents the highest level of CNS control. It incorporates gnostic function, such as multisensory integration, allowing for body image, self- location and first-person perspective. With our eyes closed, we should be able to demonstrate our body proportions. The better the body image, the more precise and efficient the posture and movement [14]. In our studies, statistically significant differences were also found in the body proportion assessment (average value: SG – 3.98, CG – 2.32). The worse results of these tests in the group of children with scoliosis indicate that body perception dysfunction may be associated with scoliosis. These results encourage the enrichment of scoliosis therapy with both re-education of head feeling and body perception.

The results of all tests showed statistically significant differences. However, none of the studies showed a correlation between the results of people with scoliosis and the value of their Cobb angles. In our opinion, this phenomenon can be explained by the existence of well-functioning compensatory mechanisms. The reports of Pialeasse et al. confirm the lack of correlation between the size of the curvature and the parameters studied [27]. These authors showed that during and after vestibular stimulation, the balance control of AIS patients regardless of the severity of spine deformation (mild or severe) is altered compared to control group. They support the suggestion, that impaired vestibulomotor or sensorimotor control may be related to scoliosis onset but not necessarily related to curve progression. To explain the fact that, regardless of spine deformation magnitude, both AIS groups had a sensory reweighting impairment these authors suggest that the spine deformation of the mild AIS patients might progress over time.

In our opinion, the issues raised in this work should be subject to further research. It is necessary to develop tools to identify abnormal sensorimotor control.

5. Conclusions

We conclude the following:

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People with diagnosed scoliosis have a significantly worse feeling of head position than people without scoliosis.