Children with visual impairments may have altered joint movement : an observational case-control study

Correspondence address: Juliana Ferreira Sauer – Rua Cipotânea, 51 – Cidade Universitária – CEP: 05360-000 – São Paulo (SP), Brasil – E-mail: jujusauer@yahoo.com.br Presentation: Jun. 2013 – Accepted for publication: May 2014 – Financing source: São Paulo Research Foundation (FAPESP) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) – Conflict of interests: nothing to declare – Approval’s report at the Ethics Committee No. 0959/08. ABSTRACT | To assess the articular range of motion in children with congenital visual impairment. Were evaluated 75 children between five and twelve years old, 49 with normal visual acuity and 26 visually impaired. Two evaluators performed the measure of active and passive range of motion by goniometry of shoulder and hip in all axes of motion. All examiners made a test of correlation between data obtained, to determine the inter-rater reliability, using the intraclass correlation coefficient (ICC). In individuals with visual impairments was statistically significant difference, with higher range of motion in individuals with visual impairments to medial and lateral rotation of shoulder and hip lateral rotation. Were found: high correlation in the inter-rater reliability (ICC>0.70) for 9 (22.5%) groups of articular range of motion, moderate correlation (0.7>ICC>0.5) for 25 (62.5%) groups and low correlation to 6 (15%) groups ranges of motion. Sampled children with congenital visual impairment showed greater joint mobility for rotational range of motion of the shoulder and hip than children with normal visual acuity, although they have also shown lower values for articular range of motion in abduction and extension in shoulders.


INTRODUCTION
Vision plays an essential role in the development of the body, being a primary source of stimuli that enable the direct relationship between the individual and the external environment 1,2 .This relationship is represented by the ability to move and explore the environment, thus determining the acquisition of essential experiences that enable the global development and the adaptation to the environment 3 .
Several studies have been trying to find relationships between the incidence of visual impairment and anthropometric changes in the affected population [4][5][6][7] , which are often motivated by the stereotyped posture that is present in some of these individuals or by the mannerisms that can be a result of poor motor development during childhood, usually associated with imperfect or absent visual stimuli 8,9 .
Other studies try to correlate such observations with the static posture 10,11 , or to correlate posture to functional tasks 12 and gait 13 .Bouchard e Tétreault 2 found that children with visual impairment presented with poorer and weaker motor skills and, in order for their movements to be functional, they would tend to change the way they performed several tasks.This study also described the decreased range of motion involving rotations, however, with no experimental confirmation, which could be related to the poor repertoire acquired during motor development.
Changes in the joint range of motion may cause alterations in the development of the musculoskeletal system of the children; especially when considering the transition period to adolescence, in which severe physical and structural changes happen 14,15 .Besides, it should be considered that children have higher values of range of motion in comparison to adults, and they can also present with benign hypermobility in childhood, which affecs 5 to 30% in the populations 16 .
According to the Brazilian Institute of Geography and Statistics (IBGE), in 2000, 14% of the Brazilians had some type of visual impairment, and, out of these, 57% had a permanent difficulty to see; nowadays, it is the most incident visual impairment in Brazil 17 .
The objective of this study was to compare the joint range of movement in children aged 5 to 12 years old with blindness and congenital low vision with asymptomatic controls.
The hypothesis is that children with visual impairment during development will present with lower values of joint range of movement.

METHODOLOGY
Male and female children, aged from 5 to 12 years old, attending the institutions Escola Júlio Mesquita, Instituição Padre Chico, Associação Brasileira de Assistência ao Deficiente Visual and patients assisted by the Sector of Sub-Normal Vision of Hospital das Clínicas, in São Paulo.Children who presented with neuromuscular, musculoskeletal and cardiorespiratory diseases were excluded 18 .
All of the participants were contacted by educational institutions that were interested to participate in the study, or families were contacted by telephone.An assessment report was offered to each one of the participants after the study was concluded.
The participation of the children depended on the parents or parties in charge signing the Informed Consent Form.The study was approved by the Research Ethics Committee of Hospital das Clínicas, in the Medical School of Universidade de São Paulo (CAPPesq).
Participants formed two groups: the control group (CG), composed of individuals with no visual alterations, and the experimental group (EG), composed of children with visual impairment caused by congenital, infectious, genetic or parasitic disorders, which would lead the visual capacity to be higher than 70% with the best correction, that is, low vision.
The dysfunctions included in the study for the EG approach the disorders that affect the sampled population the most 8 , being retinal or refraction problems, abnormality in crystalline lens or oculomotor pathologies.
In the CG, there were 49 children with mean age of 8.8±1.5 years old, being 25 male and 24 female participants, with mean weight of 30.5±11.5 kg, mean height of 1.3±0.2m, mean body mass index (BMI) of 17.5±4.7 kg/m 2 ; in the EG, there were 26 children with mean age of 8.4±2.4 years old, 12 male and 14 female participants, with mean weight of 31.5±8.7 kg, mean height of 1.3±0.1 m, mean BMI of 17.2±3.1 kg/m 2 , with visual impairment.
Goniometry was conducted by a universal goniometry by Carci®, according to the methodology described by Marques 19 for flexion, extension, abduction, lateral rotation and medial rotation movements in shoulder and hip joints, actively and passively, with participants wearing bathing suits (speed or bikini).
Measurements were taken by two different examiners, in order to ensure the reliability of the values.Inter-rater reliability was calculated by the intraclass correlation coefficient (ICC).Measurements were taken on two different days, so that the result from the first measurement would not influence the next one.

Statistics
The software Statistica 8.0 was used, and the Shapiro-Wilk test was conducted to verify data normality.Afterwards, the Student's t-test was performed for independent variables, in order to assess the differences in mean values of joint motion between the CG and the EG, with α=0.01.
By using the ICC, measurements from both evaluators were compared to determine inter-rater reliability.
ICC values of 0.00 to 0.25 were classified as little or no reliability; low reliability comprised values from 0.26 to 0.49; moderate reliability, from 0.50 to 0.69; high reliability, from 0.70 to 0.89; and very high reliability, for values that were higher than 0.90 [20][21][22] .

RESULTS
Values concerning the range of movement of passive and active medial shoulder rotation are shown in Table 1.There was a significant difference (p<0.01) between the EG and the CG, and range values are higher in the EG.
For the hip range of motion, movements that presented statistically significant differences in the Student's t-test were the passive lateral rotations and the passive left hip medial rotation, as observed in Table 2.

DISCUSSION
The objective of this study was to observe possible changes in the joint range of motion among children with visual impairment.Data show that children with visual impairment presented increased hip and shoulder range of motion, when compared to children at the same age group with no visual impairment.According to Decree n. 5,296, from December 2 nd , 2004, the person characterized with blindness is the one with visual acuity similar to or lower than 0.05 in the best eye, with the best optical correction; low vision consists of visual acuity between 0.3 and 0.05 in the best eye, also with the best optical correction, and in cases when the sum of the visual field measurement in both eyes is equal to or lower than 60º, or the simultaneous occurrence of any of the previous conditions.
It is possible that the use of rotational movements during childhood for visual impaired children is higher due to the need to discover the environment around them in an alternative way 23 , therefore, they are more developed during maturation.
Gaunet et al. 24 reported that early blindness affects both exploratory patterns and the performance of individuals, by interacting with objects disposed in a space, when compared to blind-folded individuals.
As previously described, it was expected that individuals with imperfect or absent visual acuity had differences concerning functional repertoire in their motor development, which would result in possible biomechanical changes.Results differed from the expected as to the form of these differences, since the hypothesis was that individuals with such impairment would obtain lower values of range of motion, which is exactly the opposite of what was found.
Another effect that would possibly lead to the obtained results would be sampling-related problems, once most individuals in the EG were institutionalized and participated in numberless extracurricular tasks, such as physical activities, musical education, arts, among others.Children in the CG were not stimulated nor did they have the access offered by the school to the same activities.
In order to verify this last possibility, the precision of comparisons between groups was decreased between groups.The expectation was that, in case the affirmative was true, higher values of range of motion would be higher in the EG than in the CG.
For non-rotational shoulder movements, significantly different values were obtained between groups for passive and active movements of abduction, flexion, and extension; the CG presented the highest values of range of motion.
These findings may be explained by the presupposition that, during the period of motor learning, these children experiment stimuli to reach lower levels in comparison to a situation in which they would not have visual impairment.Another possibility would be the delay to acquire cephalic stabilization, even if not completely, thus interfering in the modulation of reflexes in childhood and making it difficult to stabilize the cinguli 25 , therefore affecting the use of limbs.These findings are also in contrast with the hypothesis that institutions would be a source of error in the inferences of this study.
The intra-rater correlation index demonstrated that, for most measurements, correlation was moderate.

CONCLUSION
This study shows that children with congenital low vision have higher ranges of motion for medial shoulder rotations, both in the passive and the active forms of motion, besides the higher mobility in the passive

Table 1 .
Mean, standard-deviation and comparison between groups for movements of medial rotation, lateral rotation, abduction, flection and extension of the shoulder, passively and actively, for the right and left upper limb *Statistically significant in the Student's t-test; MR: medial rotation; LR: lateral rotation; Ab: abduction; F: flection; Ex: extension; P: passive; A: active; R: right; L: left; CG: control group; EG: Study group

Table 2 .
Mean, standard-deviation and comparison between groups for movements of medial rotation, lateral rotation, abduction, flection and extension of the shoulder, passively and actively, for the right and left lower limb Study group medial and lateral hip rotations.These findings point out to a new focus concerning training programs for motor skills and preventive interventions among children with low vision.