Improving gross motor function and postural control ...

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children were assessed by the Gross Motor Function Measure (GMFM) and accelerometry. The results .... hippotherapy internship with the North American.
Physiotherapy Theory and Practice, 2010, Early Online, 1–8 Copyright & Informa Healthcare ISSN: 0959-3985 print/1532-5040 online DOI: 10.3109/09593981003623659

CASE REPORT

Improving gross motor function and postural control with hippotherapy in children with Down syndrome: Case reports Physiother Theory Pract Downloaded from informahealthcare.com by University of Sherbrooke on 09/01/10 For personal use only.

Danielle Champagne, OT, MSc and Claude Dugas, PhD De´partement des sciences de l’activite´ physique, Universite´ du Que´bec a` Trois-Rivie`res, Trois-Rivie`res, Que´bec, Canada

ABSTRACT The purpose of this case report is to describe the impact of an 11-week hippotherapy program on the gross motor functions of two children (respectively 28 and 37 months old) diagnosed with Down syndrome. Hippotherapy is a strategy that uses the horse’s motion to stimulate and enhance muscle contraction and postural control. The children were assessed by the Gross Motor Function Measure (GMFM) and accelerometry. The results indicate that both children improved on many dimensions of the GMFM. Power spectral analysis of the acceleration signals showed improvement in postural control of either the head or trunk, because the children adopted two different adaptative strategies to perturbation induced by the moving horse.

INTRODUCTION Children with Down syndrome (DS) learn to walk and acquire many other fundamental skills later than children with typical development (Virji-Babul and Latash, 2008). The motor deficits associated with DS are described as general clumsiness and slowness of movement that persist through adulthood. Such children have longer movement and reaction times (Henderson, Morris, and Frith, 1981), balance and postural deficits (Shumway-Cook and Woollacott, 1985), and altered motor synergies (Latash, 2007). These problems may have a causal link to delays in achieving motor development milestones. The delayed motor development of infants and children with Down syndrome is characteristically associated with generalized muscle hypotonia and ligament laxity (Kubo and Ulrich, 2005). Down syndrome is a recognized disorder that can benefit from hippotherapy if there is no atlantoaxial instability (Engel, 1997). Hippotherapy is a therapeutic Accepted for publication 13 January 2010. Address correspondence to Danielle Champagne, OT, MSc, Universite´ du Que´bec a` Trois-Rivie`res, Sciences de l’activite´ physique, 3351, Boulevard des Forges, Trois-Rivie`res, Quebec, G9A 5H7 Canada. E-mail: [email protected]

intervention that uses the multidimensional movement of a horse (Fleck, 1992) to improve posture, balance, and overall function (Benda, McGibbon, and Grant, 2003). Research evidence is confirming that hippotherapy is an efficacious, medically indicated intervention in gross motor rehabilitation (Casady and Nichols-Larsen, 2004; Haehl, 1996; McGibbon, Andrade, Widener, and Cintas, 1998). Its benefits have been mainly seen in children with cerebral palsy (CP) according to various clinical observation scales and kinematic analysis that have demonstrated improvements in functional motor performance. Benda, McGibbon, and Grant (2003) reported increased muscle symmetry in children with CP, whereas Bertoti (1988) noted significant amelioration of posture during a period of therapeutic riding. Clinically subjective improvements in muscle tone quality and weightbearing abilities have also been observed by referring physical therapists. One of the aims of hippotherapy is to make the patient’s trunk receptive and responsive to movements transferred by the horse (Strauss, 1995). The effects of hippotherapy in Down syndrome have not been investigated at great length. Biery and Kauffman (1989) examined the balancing ability of teenagers and young adults with mental retardation, including Down syndrome, before and after involvement in a therapeutic riding paradigm. Their work 1

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did not provide any information on the level of training of the observers who evaluated balance control; thus, the validity of their results is questionable. To our knowledge, no one has yet assessed the impact of hippotherapy on head and trunk control in children with Down syndrome. To quantify the impact of this intervention on the neuromotor system and possible transfer of the therapy to daily activities of children with Down syndrome, gross motor performance must be evaluated. The Gross Motor Function Measure (GMFM) is recognized as being reliable and sensitive enough to quantify gross motor changes in children with Down syndrome (Gemus et al, 2001). The GMFM was developed for children with CP (Russell et al, 1989). Russell et al (1998) confirmed that the GMFM-88 was an adequate tool for Down syndrome in their validation study. It has 88 items that are grouped into five subsections: A, Lying and rolling; B, Sitting; C, Crawling and kneeling; D, Standing; and E, Running, walking, and jumping. All items can be generally accomplished by 5-year-old children without motor delays. Each item is scored on a 4-point ordinal scale. Scores for each dimension are expressed as a percentage of the maximum score for that dimension. The total score varies from 0 to 100 and is obtained by adding the percent score for each dimension and dividing by 5. Each dimension, therefore, contributes equally to the total score (Gemus et al, 2001). There are various ways to measure the kinematics of body movement. Accelerometers are force transducers that quantify the reaction forces associated with acceleration of a body segment. Body mass is accelerated against a force transducer, producing a voltage signal proportional to the acceleration (Shumway-Cook and Woollacott, 2001). Accelerometer technology in postural control could generate a better understanding of the underlying neuromuscular mechanisms induced by equine motion. The benefits of using accelerometers with children during hippotherapy compared to more traditional postural analysis instruments are that testing is not restricted to a laboratory environment; the instruments are so small that movement is relatively unrestricted; and direct measurements of three-dimensional (3D) accelerations eliminate errors associated with differentiating displacement and velocity data (Kavanagh and Menz, 2008). These are all important factors related to accelerometry application in hippotherapy intervention. Thus, the goal of the present case report was to determine how forward horse motion influenced gross motor function of head and trunk control in two children with Down syndrome after 11 weeks of hippotherapy. The impact of hippotherapy on the gross motor function of these two children with Down syndrome was assessed by the GMFM before and after Copyright & Informa Healthcare USA, Inc.

the intervention and with multiaxial accelerometer comparisons before and during the intervention.

CASE DESCRIPTIONS Two children with Down syndrome were recruited with the help of the Regroupement pour la Trisomie 21.

Child 1 history The first child was a boy born at 37 weeks’ gestation, weighing 6.1 pounds and measuring 18 inches. Down syndrome was diagnosed a few hours after birth, and the karyotype was confirmed a week later. When the intervention started, child 1 was 28 months old. Complete physical examination revealed that this child had asthma requiring an anti-inflammatory drug and a bronchodilator when needed. The child was not given his medications during the intervention with the horse. He had a cardiac defect that was surgically repaired at the age of 4 months. The physician noted difficulties in balance, learning and cognitive skills with no hyperlaxity of the hip joint. X-ray screening for atlantoaxial instability was negative, and medical consent for horseback riding was obtained from the physician.

Child 2 history The second child was a girl born at 40 weeks’ gestation, weighing 6 pounds 14 ounces and measuring 21 inches. Down syndrome was diagnosed at birth, and the karyotype confirmed this pathology. When the intervention started, child 2 was 37 months old. Complete physical examination revealed that she had a heart murmur that was completely resolved. She also had surgery at 1 month for Hirschsprung disease. The physician noted difficulties in learning and cognitive skills but no hyperlaxity of the hip joint. X-ray screening for atlantoaxial instability was negative, and medical consent for horseback riding was granted by the physician. Both children communicated by sign language and, at the time of testing, their repertoire comprised approximately 50 words. Their parents agreed not to continue their medications or to incorporate any new activities throughout the 11-week intervention period. This work was approved by the Ethics Committee of the Universite´ du Que´bec a` Trois-Rivie`res (CER-07-123-06.08).

INTERVENTION Each hippotherapy session lasted approximately 30 minutes, during which the child would take three

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different positions (face forward, side-sitting, face backward) and perform therapeutic activities on the moving horse. Sessions were conducted in indoor and outdoor arenas and trails as weather permitted. The same horse was used for both children who wore an approved lightweight helmet for horseback riding and a home-made safety belt with handles. The horseback equipment was composed of a saddle pad, a flat surcingle, a licol, and a lead chain. The author responsible for hippotherapy is an occupational therapist with 17 years of practice recognized by the American Hippotherapy Association (AHA). She completed a level II approved course and a hippotherapy internship with the North American Therapeutic Riding for the Handicapped Association (NARHA) to become a NARHA therapist. The intervention team was comprised of a horse handler and two side walkers who held the child only by the knees, to let him/her adapt safely to the various balancing challenges offered by the horse. During the intervention, the occupational therapist walked at a 45-degree angle behind the team to provide constant and immediate information to the team and to correct the horse’s direction, speed, and the child’s position. This set-up allowed the therapist to ensure that the child received the best input from the horse. The side walkers were a certified assistant therapeutic riding instructor with the Canadian Therapeutic Riding

Association (CanTRA) and a volunteer. CanTRA regulations for safety riding were respected at all times. With the parents’ approval, each therapy session was videotaped to keep a visual log of the children’s postural progression so that the stimulation received by each child in each position could be quantified (Table 1). These positions were chosen to implement various treatment goals (Table 2), and they were standardized for both children during the course of intervention. Particular attention was paid to minimize the number of stops during the therapy and to maximize the stimulation offered by the horse. The two children received about the same amount of stimulation time on the horse in each position (Table 1). The rest of the time (635%) was mainly spent on letting the parents communicate instructions to their child in sign language, and stops were made to modify the position of the children on the horse to improve the quality of the intervention. One child was absent for one hippotherapy session because of a medical intervention.

MEASURES Gross motor function measure The two children were assessed according to the following dimensions of the GMFM-88 for children

TABLE 1 Hippotherapy intervention time for each position on the horse in both children Position 1 Facing forward

Position 2 Side-sitting

Position 3 Facing backward

Total/330 min (11 sessions330 min)

Child 1

93 min

62 min

60 min

215 min (65%)

Child 2

95 min

55 min

61 min

211 min (64%)

TABLE 2 Treatment goals Hippotherapy intervention summary

Main goal

Objectives

Description of activities on the horse

Stimulation of balance

Crossing the midline with one hand

Reaching toys in different places on the horse

Stimulation of muscular control

Improving movement precision and strength Stimulation of anticipation to keep the visual platform stable Stimulation of memory

Grooming and throwing activities

Stimulation of visual-motor coordination Stimulation of verbal communication and cognitive skills

Catching activities Teaching vocabulary related to horses

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with Down syndrome: A, Lying/rolling; B, Sitting; C, Crawling/kneeling; D, Standing; and E, Walking/ running/jumping. It was administered in a standardized manner, as described in manuals, by a physiotherapist who is a clinical instructor in Que´bec for this particular type of assessment. GMFM evaluation took place before and after the 11-week hippotherapy intervention. The children’s parents assisted the physiotherapist in the evaluation process by using sign language and verbal cues to communicate with their child.

Interrater agreement Two physiotherapists, who had received training in GMFM-88 administration, rated the children’s performance. The first examiner recorded the scores live while the children were videotaped. The second rater was blinded (simple blind method) to whether the evaluation was done before or after hippotherapy by viewing only the videotapes. Interrater reliability between therapists ranged from 0.96 to 0.97 for the pre- and posttest, respectively.

Accelerometry The stimulation provided by the horse and the movements of the children were quantified by multiaxial accelerometers (MTx; Xsens Technologies, Enschede, The Netherlands) to follow the evolution of head and trunk control related to movements of the horse (Figure 1). The children were always seated facing forward and instructed to look in front of them during data collection. The accelerometers were

placed on the children only during the testing sessions. Signals from the accelerometers were collected at a sampling rate of 50 Hz on a portable computer with a customized LabView program. A low-pass Butterworth filter (second-order, zero-lagged) with a cut-off frequency of 30 Hz was applied to the raw acceleration data prior to analysis. Trigonometric correction was conducted in each axis to account for the small tilt angle between the axes of the accelerometer when it was attached to the child. Fourier transformation was performed for acceleration signals from the head and trunk in the vertical, anteroposterior (AP), and mediolateral (ML) directions. Fourier transformation is related to the frequency domain. This passage from the time domain (acceleration signal) to the frequency domain allows fine grain analysis of movement performance to better understand the compensatory responses related to movement of the horse. Frequency and harmonic analyses were undertaken on all acceleration data by customized software developed in Matlab version 6.0 (Mathworks R12). The power spectra for each child were inspected visually to identify relevant changes. Power spectral analysis was performed on head and trunk accelerations collected during the first and fourth hippotherapy sessions. During this case report, the intervention team experienced a technical problem with one accelerometer and were unable to replace it before the posttest, which explains why the pre- and midtest data were compared.

OUTCOMES Gross motor function measure

FIGURE 1 Placement of accelerometers on the child and the horse.

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Many dimensions evaluated by the GMFM showed improvements in both children, which were confirmed by the two physiotherapists who assessed them (Figure 2). Data analysis (t test for independent subjects, p,0.05) revealed that the mean total scores for the GMFM by both examiners disclosed a significant treatment effect in child 1 between the pre- and posttest (t53.058, df54, p,0.05), with a similar pattern for child 2 (t52.662, df54, p50.056). Item E (running, walking, and jumping) of the GMFM demonstrated the largest improvements in both children. This item also had the lowest scores on the pretest for both children. For both examiners, it was the item that had the largest number of variations between the pre- and posttest. McNemar’s nonparametric test was performed to determine if these variations between the pre- and posttest were in the same direction. For child 1, both examiners noted that

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80

DISCUSSION

60 40 20 0

(A)

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C GMFM items

D

E

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The vertical axis is inferred by the horse, and the child has no control over it, which explains why the results from this axis are not presented.

Post test

80 60 40 20 0

A

(B)

B

C GMFM items

D

E

FIGURE 2 GMFM results for child 1 (A) and child 2 (B).

seven variations were all in the same direction and were statistically significant (p,0.05). For child 2, examiner 1 recorded four variations, and examiner 2 reported eight variations, all in the favorable direction; these variations were also significant (p,0.05).

Accelerometry Power spectral analysis disclosed a decrease in lower frequency content (0 to 5 Hz), which reflected more stability of either the head (child 1) or the trunk (child 2) over time in the mediolateral plane (Figure 3). Cumulative power curves of the trunk in the mediolateral plane for child 1 were identical between 1 and 5 Hz for the pre- and midtest. However, child 2 showed a sharp decrease of cumulative power between the pre- and midtest for these same frequencies. This trend was reversed for the head, with child 1 presenting a clear reduction of cumulative power from the pre- to midtest, and child 2 manifesting very similar curves for the pre- and midtest (Figure 3). The anterior-posterior axis frequency profiles of head and trunk accelerations were similar for child 2 and only for the trunk for child 1. The increase observed from 1 to 5 Hz for the head could be a transient phase for this child, and a longer treatment period could have generated similar improvements for this direction also.

This report highlighted the potential of hippotherapy of children with Down syndrome. The complex sensory motor stimulation offered by the horse’s movement is very difficult to reproduce in a traditional therapy setting. In fact, an adult horse walking can offer up to 110 postural perturbations in various directions in 1 minute (Strauss, 1995). Most hippotherapy sessions last 30 minutes; the horse will take 3000 steps during a session, walking at 100 steps/minute, which implies that the child explores a range of motor solutions in terms of muscle synergies involved in trunk and head control. Moreover, such stimulation provides a valuable environment for learning new motor strategies that could be used by the child in daily functional activities (McGibbon, Benda, Duncan, and Silkwood-Sherer, 2009). The GMFM results revealed improvements in gross motor behaviour, particularly for walking, running, and jumping (dimension E). These functional tasks require good control of the head and trunk (Pozzo, Berthoz, and Lefort, 1990). In fact, trunk control is recognized as a critical feature to minimize the impact of gaitrelated oscillations on head movement (Kavanagh, Morrison, and Barrett, 2005). Both children improved their overall scores from the pre- and posttest: child 2 (83.2%/87.9%) and child 1 (77.2%/83.1%). However, the results for child 2 did not reach the level of statistical significance, which could be partially explained by the fact that this child was close to a ceiling effect in the pretest for two dimensions (A, B). These improvements in the GMFM were coupled with specific strategies in terms of head and trunk control in the mediolateral axis for the acceleration profiles. According to Assaiante, McKinley, and Amblard (1997), independent control of the upper body appears earlier for anterior-posterior balance compared to mediolateral balance in children and also when adults are confronted by new postural challenges. The mediolateral plane offers the most difficult challenge to the motor control system even in adults (Assaiante, McKinley, and Amblard, 1997). Kavanagh, Morrison, and Barrett (2005) investigated head and trunk coordination during walking in healthy young adults by accelerometry and reported that the largest differences were between the head and trunk in the mediolateral direction. The overall accelerometry data demonstrated interesting adaptive responses to the postural challenges induced by the horse. Two distinct strategies permitted improvements in dimension E (walking, running, and jumping) Physiotherapy Theory and Practice

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Head M/L

Cumulative power (%)

100

Head A/P 100

80 60

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FIGURE 3 Cumulative power of each harmonic frequency for the head and trunk in child 1 (A) and child 2 (B) for ML and AP axis.

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of the GMFM. When the child is responding to movements of the horse, he/she must maintain his/her head and trunk over the base of support to stabilize vision and coordinate postural muscle synergies. Both children improved their overall gross motor functions by damping head and trunk movements in lower-frequency content (0 to 5 Hz). Such damping could be linked to improvements in anticipatory mechanisms that allowed both children to diminish compensatory responses, as illustrated by a clear reduction of frequency content (cumulative power). As suggested by Latash, Almeida, and Corcos (1993), the variability of motor responses represents adaptive processes within the central nervous system that considers aptitudes and limitations to optimize motor performance. The hippotherapy intervention for these two children with Down syndrome improved their motor performances in fundamental motor skills (walking, running, and jumping), as revealed by the GMFM results. These improvements could be related to the fact that the intervention team maximized the time spent on the moving horse (child 1: 65% and child 2: 64%; Table 1) to allow the children to respond to the stimulation in a nearly continuous manner. The quantification of postural control permitted us to measure modifications during the treatment phase. Based on these results, the authors believe that accelerometers could objectively quantify changes in the postural control system during hippotherapy. Moreover, one possible outcome of this approach is that clinicians could be guided to establish the optimal time frame for intervention that could produce significant clinical effects. One pitfall to external validity in case studies is the limited number of subjects. A small number of subjects limits generalizability of the results, but legitimizes fullscale research. Finally, the authors are confident that this report constitutes a stepping stone to implement accelerometry as a tool in hippotherapy research.

ACKNOWLEDGMENTS We thank the American Hippotherapy Association for their financial support and E´liane Trempe for all aspects related to horses, volunteers, and staff. Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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