DOCTORA L T H E S I S
2007:11
Dynamic Ankle-Foot Orthoses
in Children with Spastic Diplegia
interview and experimental studies
-20
07:1
1
Universitetstryckeriet, Luleå
Luleå University of Technology Department of Health Science
Division of Physiotherapy 2007:11|: 102-15|: - -- 07⁄11 --
Annika Näslund
Annika NäslundDynamic Ankle-F oot Or thoses in Childr en with Spastic Dipleg ia - inter view and exper imental studies
-Dynamic Ankle-Foot Orthoses in Children with
Spastic Diplegia
- interview and experimental studies -
Annika Näslund
Luleå University of Technology, Department of Health Science, Division of Physiotherapy
Fantasy is more important than knowledge
Albert Einstein
CONTENT
ABSTRACT 7
Dynamic Ankle-Foot Orthoses in Children with Spastic Diplegia 7
- interview and experimental studies - 7
ABBREVIATIONS 9 ORIGINAL PAPERS 10 INTRODUCTION 11 Cerebral palsy 11 Definition 11 Classification 12 Postural control 18 Theoretical framework 19
Standing postural adjustments in children 21
Standing postural adjustments in children with CP 22
Ankle-foot orthoses in children with CP 24
Foot Orthoses 29
Reaching performance 31
Typically developing children 31
Children with CP 32
Laboratory measurements of postural control 33
Kinematics 33 Kinetics 34 Electromyography 34
Rationale for this thesis 35
METHODS 37
Interview study 38
Study design 38
Participants 38
Data collection methods 38
Data analysis 38
Experimental / Laboratory studies 39
Study design 39
Participants 41
Data collection methods 42
Data analysis 44
Statistics 46 Ethics 47
RESULTS 49
Parent´s perception of DAFOs (study I) 49
DAFOs effects on standing posture and weight distribution (study II) 50 DAFOs effects on CoP displacement and anticipatory postural adjustments
during different support conditions (study III) 53
Reach performance and postural adjustments wearing DAFOs (study IV) 56
Reach performance 56
Postural adjustments 59
DISCUSSION 63
Results 63
Parent´s perception of DAFOs 63
DAFOs effects on standing posture and weight distribution 64
DAFOs effects on CoP displacement and anticipatory postural adjustments
during different support conditions 64
Methodological considerations 68 Trustworthiness 68 Credibility 68 Transferability 69 Study group 69 Internal validity 70 External validity 71 Clinical implications 72 CONCLUSIONS 73 SVENSK SAMMANFATTNING 75
Dynamisk Ankel-Fot Ortos (DAFO) hos Barn med Spastisk Diplegi 75
- intervju och experimentella studier - 75
ACKNOWLEDGEMENTS 77
REFERENCES 80
ABSTRACT
Dynamic Ankle-Foot Orthoses in Children with Spastic Diplegia - interview and experimental studies -
Dynamic ankle-foot orthosis (DAFO) is a thin supra malleolar orthosis used as a compliment to the total treatment program in children with cerebral palsy (CP) in order to facilitate function in sitting, standing and walking. The DAFO keeps the foot in a functional position and is said to provide the child with proprioceptive feedback for balance- and postural control. The aim of the present thesis was to explore how parents of children with spastic diplegia experience the use of DAFOs and to determine the effects of DAFOs in stan-ding during a reaching movement, in relation to postural orientation, anti-cipatory- and compensatory postural adjustments, and the quality of the reaching movement. The parents of 15 children, aged 4-18 years, who had spastic diplegia and wore DAFOs were interviewed with a broad research question “How do you perceive that DAFO influence your child” and analysed with content analysis. Children with spastic diplegia, aged 5-12 years, (n=6 in studies II and IV and n=4 in study III) classified at level II-IV according to Gross Motor Function Classification System (GMFCS) and typically developing children (controls) (n=8 in study III and n=6 in study IV) in the same age-group performed a voluntary reaching movement towards a target while standing on force plates. This allowed for registration of forces, movement and muscle activity (EMG). Children with spastic diplegia used DAFOs and/or shoes during the experiment while controls used shoes only. The parents experienced that DAFOs with their stabilizing effect on the foot and ankle enabled postural control and alignment, which contributed to functional activities under more favourable physical conditions. Moreover, psychosocial aspects such as a feeling of security, safety and freedom were regarded by the parents as being as important as the physical effects. Our findings showed that children with more severe spastic diplegia applied their body weight in standing more evenly between the legs and improved extension of the knee using DAFOs compared to wearing shoes alone. To initiate the reaching movement, despite different support conditions, children with spastic diplegia wearing DAFOs, as well as the controls make use of anticipatory postural adjustments. Furthermore, during the acceleration and deceleration phase of the reaching movement, children with spastic diplegia make use of
postural adjustments characterized by co-contraction of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles bilaterally. The postural adjustments in the controls were characterized by increased TA activity on the reach side during the acceleration phase and increased LG activity on the non-reach side during the deceleration phase. Movement quality in reaching in children with spastic diplegia showed that coordination between upward and forward reach velocity differed regarding temporal phasing and amplitudes of velocity peaks compared to the controls.
According to parents´ perceptions DAFOs can be regarded as a part of treat-ment that improves stability, balance and functional skills. Children with severe spastic diplegia wearing DAFOs can, in spite of different support conditions, practice standing with a more evenly distributed body weight on the feet. The practice of reaching movements while standing with DAFOs can promote mo-tor learning of postural adjustments and thereby improve the ability to use the hands in daily activities.
Key words: Spastic Diplegia, Postural Control, Standing, Reaching, Kinema-tics, KineKinema-tics, Electromyography.
ABBREVIATIONS
ACPIC American Cerebral Palsy Information Center ADL Activity of Daily Living
AFO Ankle-Foot Orthosis
AMTI Advanced Mechanical Technology Incorporation
ASCII American Standard Code for Information Interchange
BoS Base of Support
CCD Charge-Coupled Device
CoM Center of Mass
CP Cerebral Palsy
DAFO Dynamic Ankle-Foot Orthosis
ELITE Elaboratore di Immagini Televisive EMG Electromyography
FO Foot Orthosis
GMFCS Gross Motor Function Classification System
GRF Ground Reaction Forces
HAFO Hinged Ankle-Foot Orthosis
ICF International Classification of Functioning, disability and health ISO International Organization of Standardization
LG Lateral Gastrocnemius
MACS Manual Ability Classification System
PLS Posterior Leaf Spring orthosis
RMS Root Mean Square
RoM Range of Movement
SAFO Solid Ankle-Foot Orthosis
SCPE Surveillance of Cerebral Palsy in Europe
SMO Supra Malleolar Orthosis
SWASH Standing, Walking and Sitting Hip orthosis
TA Tibialis Anterior
ORIGINAL PAPERS
The present thesis is based on the following papers, which will be referred to by their roman numerals:
I. Näslund A, Tamm M, Ericsson A-K, von Wendt L. Dynamic ankle- foot orthoses as a part of treatment in children with spastic diplegia – parents perceptions. Physiotherapy Research International 8 (2); 59-68, 2003.
II. Näslund A, Jesinkey K, Sundelin G, von Wendt L, Hirschfeld H. Effects of dynamic ankle-foot orthoses on standing in children with severe spastic diplegia. International Journal of Therapy and Rehabilitation 12 (5); 200-207, 2005.
III. Jesinkey K, Näslund A, Hirschfeld H. Initiating of reaching when standing with and without DAFOs in children with spastic diplegia. Advances in Physiotherapy 7; 144-153, 2005.
IV. Näslund A, Sundelin G, Hirschfeld H. Reach performance and
postural adjustments during standing in children with severe spastic diplegia using DAFOs.
Submitted for publication.
Introduction
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INTRODUCTION
The work presented in this thesis focused on postural control and reaching kinematics during standing in children with moderate to severe spastic diplegic cerebral palsy (CP) wearing dynamic ankle-foot orthoses and on parent’s perception of the orthoses. Postural control is according to Campbell (1990), a promising outcome of physical therapy interventions in the management of CP. However, some studies have investigated the effectiveness of physical therapy interventions for enhancing postural control in children with CP, for example, adapted seating, balance training, neurodevelopmental treatment, ankle-foot orthoses, etc. (Myhr et al. 1991, Myhr and von Wendt 1995; Butler 1998; Kuczynski 1999; Rennie et al. 2000; Kott and Held 2002; Washington et al. 2002; Shumway-Cook et al. 2003).
Cerebral palsy
Rosenbaum (2003) states that CP can not be cured, but interventions can improve functional abilities, participation and quality of life. CP is the most common physical disability in childhood (Kuban and Leviton 1994; Rosenbaum 2003; Koman et al. 2004). It is caused by non-progressive damage to the developing brain, which occurs in utero during delivery or during the first 2 years of life (Cans 2000). The prevalence of CP is about 2-2.5 per 1000 live born children in the Western world (Cans 2000; Stanley et al. 2000; Hagberg et al. 2001) and has been thoroughly investigated for patients in Sweden (Hagberg et al. 1993), in the UK (Pharoa et al. 1990) and in Australia (Stanley and Watson 1992). CP is a well- recognized neurodevelop-ment impairneurodevelop-ment affecting the newborn child, and it persists through-out the lifespan (Bax et al. 2005).
Definition
Defining CP has always been a challenge (Bax et al. 2005) and consensus about the term is lacking but attempts to solve the termi-nological confusion have been made through the years (Kavcic and
Introduction
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Vodusek 2005). Bax (1964) in cooperation with an international work group stated that CP is a disorder of movement and posture as a result of a defect or lesion of the immature brain. Furthermore, Mutch and colleagues (1992) modified the definition according to the heterogeneity of disorders and described the term CP as an umbrella term that covered a group of non-progressive, motor impairments syndromes secondary to lesions or anomalies of the immature brain in the early stages of development. This definition emphasized the motor impairment and its variability and excluded progressive disease. Rosenbaum and co-workers (2005) describe CP as a group of disorders of the development of movement and posture, caused by activity limitation, resulting from non-progressive disturbances that occurred in the developing fetal or infant brain. The motor disorders of CP are often accompanied by disturbances of sensation, cognition, communication, perception, and/or behaviour, and/or by a seizure disorder.
Classification
The classification of CP covers a wide range of clinical presentations and degrees of activity limitation and is used to further categorize individuals with CP into classes or groups (Cans 2000; Paneth et al. 2005). The degree of impairment depends on the location and the severity of the irreversible damage to the brain and ranges between a minor motor impairment to whole body involvement (Koman et al. 2004). Furthermore, the impairments change constantly throughout the life cycle as the child grows, develops and compensates for underlying abnormalities along with changing demands from the environment (Campbell 1997). CP has traditionally been classified according to topographic distribution of abnormal muscle tone, posture or movement (Cans 2000; Koman et al. 2004; Paneth et al. 2005) and includes:
x hemiplegia (hemiparesis) – involving one leg and one arm on the same side
x diplegia – involving both legs (some limited involvement of the arms)
Introduction
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Another classification based on the most obvious motor impairment includes: spastic, ataxic, athetotic and dystonic CP (Hagberg et al. 1993; Bullock and Henze 2000; Cans 2000; ACPIC 2001). The classi-fication scheme according to Hagberg and co-workers (1993) classify CP in three main categories: spastic (hemiplegia, diplegia and tetraplegia), ataxic (diplegia) and dyskinetic (choreoathetosis, dys-tonic), and is often used in epidemiological studies (Kavcic and Vodusek 2005).
Spastic CP results from involvement of the motor cortex or white matter projections to and from cortical sensor motor areas of the brain (Shumway-Cook and Wollacott 2001) and is the most common disorder affecting 70-80% of children with CP (ACPIC 2001; Hagberg et al. 2001). Spasticity is clinically characterized by velocity dependent resistance to passive movement that increases muscle tone, abnormal movement synergies, poorly selective muscular control, limited active range of movement (RoM) due to co- activation of agonist and antagonist, and abnormal postural control (Campbell 1991; Shumway-Cook and Wollacott 2001). Accordingly, spastic CP affects various muscles in the trunk and extremities depending on the severity of the upper motor neuron trauma (Nowak and Handford 1999). The hyperactivity of the muscles has a functional impact on the child and effects development and maintenance of posture, balance and gait (Whittle 1997; Shumway-Cook and Wollacott 2001). The ataxic type of CP is categorized by damage to the cerebellum and problems with balance and coordinated movements appears (Bullock and Henze 2001; Shumway-Cook and Wollacott 2001).
Athetotic or dyskinetic CP is a disorder characterized by slow, unintentional or uncontrolled writhing movements caused by lesion to the extra pyramidal system (Bullock and Henze 2001; Shumway-Cook and Wollacott 2001).
The classification of CP according to the Surveillance of Cerebral Palsy in Europe (SCPE) has been slowly increasing and classifies CP into different subtypes of motor impairment (Table 1) (Cans 2000; Rosenbaum 2005).
Introduction
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Table 1. European classification of motor impairment in CP.
Spastic cerebral palsy is characterised by at least two of
- abnormal movement pattern of posture or movement - increased tone
- pathological reflexes
Spastic bilateral cerebral palsy is diagnosed if
- limbs on both sides of the body are involved
Spastic unilateral cerebral palsy is diagnosed if
- limbs on one side of the body are involved
Ataxic cerebral palsy is characterised by both
- abnormal pattern of both posture and movement
- loss of orderly muscular coordination so that movements are performed with abnormal force, rhythm and accuracy
Dyskinetic cerebral palsy is dominated by both
- abnormal pattern of posture or movement
- involuntary, uncontrolled, recurring and occasionally stereotyped movements
Dystonic cerebral palsy is dominated by both
- hypokinesia (reduced activity – stiff movement) - hypertonia (increased muscle tone)
Choreoathetotic cerebral palsy is dominated by both
- hyperkinesia (increased activity – stormy movement) - hypotonia (decreased muscle tone)
Since traditionally classification of CP focuses primarily on distributed pattern of affected extremities and predominant type of muscular tone, an Executive Committee for the Classification of Cerebral Palsy has proposed a revised and updated four dimensional classification system in order to expand our understanding and improve our ability to be more accurate to classify children with CP. Previous classification schemes included only involvement of upper and lower extremities, however the updated classification scheme takes into account all body regions, i.e. trunk, all extremities and oropharynx (Table 2) (Paneth et al. 2005).
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Table 2. Components of CP classification.
1. Motor abnormalities
A. Nature and typology of the motor disorder: observed tonal abnormalities (hyper- hypotonus) and movement disorders (spasticity, ataxia, dystonia or athetosis)
B. Functional motor abilities: extent of limitation in motor function in all body areas, including oromotor and speech function
2. Associated impairments
Seizures, hearing or vision impairments, or attentional, behavioural, communicative and/or cognitive deficits and the extent to which impairments interact in individuals with CP
3. Anatomic and radiological findings
A. Anatomic distribution by motor impairments or limitations, affected parts of the body (limbs, trunk or bulbar region)
B. Radiological findings: neuroanatomic findings such as ventricular enlargement, white matter loss, or brain anomaly
4. Causation and findings
Whether there is a clearly identified cause as it usually is with postnatal CP (head injury or meningitis) or when brain malformations are present and the time frame during when the injury occurred
Most commonly motor abilities that define CP are accompanied by one or more nervous system dysfunctions such as cognitive distur-bance, visual difficulties, hearing loss, learning disabilities and behav-ioural problems (Bax 1963; Badawi et al. 1998).
The methods to classify CP by body involvement and by movement disorder are often subjective in nature and focus on impairment rather than on the child’s functional level (Cans 2000). The Gross Motor Function Classification System (GMFCS) for Cerebral Palsy was developed to measure the child’s disability in a standardized way and according to abilities and limitations as listed by the World Health Organization (Palisano et al. 1997). The GMFCS has been tes-ted for validity and reliability in children with CP aged 0-12 years (Wood and Rosenbaum 2000). It is a five-level classification system used to describe the child’s self-initiated functional ability in sitting and walking and the need to use assistive devices (walkers, crutches, wheelchair) (Table 3) (Palisano et al. 1997). A child classified at level I can perform all activities, as those of an age-matched peer except
dif-Introduction
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ficulties concerning speed, balance and coordination. A child at level V has difficulties with all positions due to lacking postural control of the head and trunk (Morris and Bartlett 2004). GMFCS has internationally been cited in a number of research designs to select and describe the study samples in order to enhance communication among and between health professionals (Morris and Bartlett 2004), including interventions used in the physical management of children with CP such as physical therapy (Bower et al. 2001; Knox and Evans 2002; Trahan and Molouain 2003) and orthoses (White et al. 2002).
Table 3. The five levels of Gross Motor Function Classification System (GMFCS).
Level I Walks without restrictions; limitations in more advanced
gross motor skills
Level II Walks without assistive devices; limitations in walking outdoors
and in the community
Level III Walks with assistive devices; limitations in walking outdoors and
in the community
Level IV Self mobility with limitations; children are transported or use
power mobility outdoors and in the community
Level V Self mobility is severely limited even with the use of
supporting technology
Paneth et al. (2005) state that SCPE recommended that the upper and lower extremity should objectively be classified separately. The Man-ual Ability Classification System (MACS) was developed by Eliasson and co-workers (2006) to assess arm and hand function and was shown to have good interrater reliability between parents and pro-fessionals.
For children with CP the World Health Organization´s (WHO) Model of health and disease is an important conceptual framework that provides a broad spectrum focusing on functioning and disability across the lifespan (WHO 2001). The International Classification of
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Functioning, Disability and Health (ICF) classifies abnormalities at two levels (Figure 1) (WHO 2001).
x body structures (anatomical) and body function (physiological and psychological)
x limitations in everyday activities and restrictions in participation in life situations
Figure 1. World Health Organization of the International Classification of Functioning, Disability and Health (ICF).
The main purpose of managing children with CP, according to Rosenbaum and Stewart (2005) should be to use appropriate combi-nations of interventions to prevent secondary impairments in order to enhance function and to increase developmental capabilities.
In this thesis we focused mainly on non-ambulatory children with spastic diplegia (involving the lower more than the upper extremity) at GMFCS level III-IV. According to the ICF this thesis emphasised body structure/function and activity in the experimental studies, and on body structure/function, activity and participation in the interview study. PERSONAL FACTORS ACTIVITY BODY STRUCTURE FUNCTION PARTICIPATION ENVIRONMENTAL FACTORS HEALTH CONDITION
Introduction
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Postural control
Maintaining postural control is required for the performance of activities of daily life. Postural control for movement involves controlling the body’s orientation in space for stability as well as the body´s orientation to the task within environmental context (Massion 1994; Horak and Macpherson 1996). Postural stability reflects the ability to control the body´s equilibrium at rest (static equilibrium) and during movement (dynamic equilibrium), i.e. to control the center of mass (CoM) over the base of support (BoS) (Horak 1992). Postural orientation for most functional tasks includes both biomechanical alignment of the body segments to vertical and the body orientation to the environment (Shumway-Cook and Wollacott 2001). Postural control and balance control have been used in parallel to refer to the act of returning or keeping the body close to the equilibrium point (Karlsson and Fryktberg 2000). Forces acting to control posture and balance, exerted by different groups of muscles, are reflected in the ground reaction forces (GRF) (Horak and MacPherson 1996).
The central nervous system organizes the postural control system through activation of muscle synergies since the brain can not identify every single muscle contraction (Massion et al. 2004). To control our posture in standing or assume any desired position we continually change our motor response pattern according to perceptual in-formation that specifies the environment and our body´s orientation in it. Several perceptual systems are involved in detecting the body´s position and movement in space with respect to gravity and environment. Kinesthetic inputs from vestibular systems provide us with information about head position and movement, and pro-prioception provides us with information about limbs and body parts position relative to each other. Visual information tells us about the body´s position relative to the environment (Horak and MacPherson 1996).
Two different types of postural control mechanisms can be identified, anticipatory and reactive/compensatory postural adjustments. A voluntary arm movement can perturb postural stability since movement of one or more body segments results in a displacement in the CoM and can move it outside BoS unless compensation occurs.
Introduction
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Furthermore torques arising from acceleration of one body segment will act upon other segments and must be counteracted to minimize changes in the body posture (Zajac and Gordon 1989).
One way to maintain postural stability and control the perturbing forces is to make anticipatory postural adjustments before or in conjunction with a voluntary movement (Massion 1994; Horak and MacPherson 1996; Massion and Wollacott 1996). The type and mag-nitude of anticipatory postural adjustments are determined by the speed and direction of the voluntary movement (Aruin and Latash 1996) and seem to be based on earlier experience rather than sensory input (Patla 1995).
The center of pressure (CoP) reflects the point at which the reaction force of the ground impacts on the body (Winter et al. 2003) and is used to analyze postural stability and anticipatory postural adjust-ments (Horak and MacPherson 1996).
Reactive/compensatory postural adjustments compensate for perturbed equilibrium triggered by somatosensory and kinaesthetic input after and during an arm movement activity to compensate for inadequate anticipatory control or in reaction to external pertur-bations (Horak and MacPherson 1996). These postural adjustment mechanisms act both to stabilize the body segments for movement and to stabilize the body against gravity (Massion 1994). For example, in standing the ankle strategy (small perturbation) distal-to-proximal synergy activation pattern of the lower limb muscles or the hip strategy (larger perturbation), which activate larger multi-joint movements, are acting to bring the CoM within BoS (Nashner 1989). Theoretical framework
In this thesis the theoretical and clinical assumptions are based on the systems model of motor control proposed by Horak (1991, 1997). The model consists of a collection of systems that depending on the functional goal, contribute to the control of movement for a given task. These include the musculoskeletal system, predictive central set, environmental adaptation, perception of orientation, sensory inter-action and sensory motor strategies.
Introduction
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For the organization of postural control the following systems are interactive: the musculoskeletal system contributes to the biomechanical factors resulting from internal (muscle forces) and external (gravity) forces and the movement of body segments; the predictive central set system provides anticipatory strategies based on experience and learning; the environmental adaptive system provides both feed forward and feedback control by using somatosensory, vestibular and visual information for the activation of postural strategies; the perception of orientation system determines the postur-al orientation gopostur-al for a specific task; the sensory interaction system adjusts all sensory information to the postural context based on postural experience and expectations; and the sensory motor strategy system provides a number of innate and learned movement strategies used for planning of an action in order to meet the postural goal. Shumway-Cook and Wollacott (2001) considered the systems model as a foundation for clinical application and stated that movement arises from an interaction between the task, the environment and the multiple sensory, motor and cognitive processes within the individual. The development of postural control (postural adjustments) is based on the development of neural- and musculoskeletal systems such as motor processes - maintaining postural stability in the body segments through the emergence of neuromuscular response synergies; sensory processes - maturation of central sensory strategies that organize out-puts from visual, vestibular and somatosensory systems for orien-tation of the body segments in space and musculoskeletal com-ponents - development of muscle strength and RoM (Shumway-Cook and Wollacott 2001). Postural control in the child emerges when each of these three systems reaches the level necessary to support the specific motor behaviour (Thelen 1986). Based on the systems of motor control, these systems work in concert and interact with other sub-systems to produce efficient strategies for safe body posture and recovery of postures (Thelen 1986; Horak 1991).
According to Forssberg and Hirschfeld (1994) postural control is organized at two functional levels. The first level is the basic direction-specific patterns of postural adjustments and the second level is the fine tuning of this basic pattern. During external
Introduction
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perturbations a forward sway of the body induced primarily an activation of the dorsal muscles and a backward sway of the body induced primarily an activation of the ventral muscles. Through multisensory afferent input (somatosensory, visual and vestibular) modulation of this motor pattern can be activated by changing order in which the agonist muscles are recruited (distal-to-proximal or in a reversed order), by modifying the size of the muscle contraction or by altering the degree of antagonistic activation.
Standing postural adjustments in children
During the age period of 9 to 12 months infants can stand without support (Piper and Darrah 1994). External perturbation has been used to investigate reactive/compensatory postural adjustments in standing children (Shumway-Cook and Wollacott 2001). With increasing age and thereby increasing capacity in standing infants learn through experience to use direction-specific postural adjust-ments (Sveistrup and Wollacott 1997).
Reactive/compensatory postural adjustments
Forward platform translation during standing in children showed direction-specific activation of ventral postural muscles while backward translations activated dorsal postural muscles, the order in which the neck, trunk and legs are activated depend on the age of the child (Forssberg and Nashner 1982; Sveistrup and Wollacott 1996). Forssberg and Nashner (1982) found consistently activated (reac-tive/compensatory) postural adjustments as response to perturbations in newly walking children at 15 months.
As soon as children are able to stand and walk independently postural adjustments are characterized by a strong dominance of postural recruitment in a bottom-up fashion (Sveistrup and Wollacott 1996). Antagonistic co-activation was present from the emergence of independent stance until 5 years of age (Forssberg and Nashner 1982). In the age period of 7-10 years reactive/compensatory postural adjustments became more adult like with no significant differences in onset latency, variability or temporal coordination between leg muscles in this age group compared to adults (Shumway-Cook and Wollacott 1985). Roncesvalles and colleagues (2002) studied the
Introduction
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development of two balancing strategies, i.e. ankle (strategy for small disturbances) and hip (used for larger disturbances) and found that infants with less than 6 months of walking experience were able to apply both strategies.
Anticipatory postural adjustments
The postural activity preceding a voluntary movement is dependent on age, position and task. Anticipatory postural control provides a framework for skilled movements and develops in parallel with reac-tive/compensatory postural control (Shumway-Cook and Wollacott 2001).
During most standing tasks anticipatory postural adjustments emerge at the age of 13-14 months (Barela et al. 1999; Witherington et al. 2002) and are consistently present beyond the age of 18 months (Forssberg and Nashner 1982; Haas et al. 1989; Assaiante et al. 2000). However, Riach and Hayes (1990) demonstrated no consistently anti-cipatory adjustments preceding arm rising in standing children aged 4 years.
At the beginning of each new acquisition of the child the first anticipatory postural adjustment response pattern commonly found is a co-contraction and through experience and practice of a movement in the specific posture more variability in postural adjustments and movement occurs (Hadders-Algra et al. 1992; Vereiiken et al. 1992). Standing postural adjustments in children with CP
Studies on postural control in standing in children with CP mainly used external perturbations and very few used self-initiated move-ments.
Reactive/compensatory postural adjustments
Standing children with spastic diplegia aged 1.7-14 years of age showed non-selective activation of agonist and antagonist muscles, increased recruitment of antagonist muscles and increased frequency of reversals activity of the basic muscle recruitment pattern (proximal to distal) of leg and thigh muscles in response to platform
pertur-Introduction
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bations (Burtner et al. 1998; Wollacott et al. 1998). Nashner and co-workers (1983) showed reversal in muscle onset sequencing, proximal to distal (hamstrings/quadriceps muscles activated prior to gastroc-nemius/tibialis anterior) and co-contraction of agonist and antagonist muscles in children aged 7-9 years with spastic diplegia following platform translations.
Burtner et al. (1998) and Wollacott et al. (1998) found that in typically developing children a crouched posture in standing during platform translations contributed to disorganized muscle responses such as co-activation of agonists and antagonists and a more proximal-to-distal muscle recruitment order. According to the authors this suggests that one contributing factor to disorganized muscle responses in children with spastic diplegia is their musculoskeletal alignment leading to a crouched posture (hips and knees flexed and ankles dorsiflexed). Furthermore, Roncesvalles and co-workers (2002) concluded that due to the smaller limits of stability in children with spastic diplegia they are unable to increase muscle response amplitude when balance threats increase in magnitude compared to typically developing children.
During quiet standing ambulatory spastic diplegic as well as healthy children with eyes closed and opened make use of transverse rotation of the body for anterior-posterior balance control revealed by CoP measures, thus this postural strategy is especially important for chil-dren with spastic diplegia since these chilchil-dren have poor ankle control (Ferdjallah et al. 2002).
Anticipatory postural adjustments
During a reaching task in standing children with spastic diplegia aged 6-12 years showed similar anticipatory muscular activity patterns as typically developing children although with later onset time and greater variability (Zaino and Westcott 1997; Westcott et al. 1998). Children with spastic diplegia according to GMFCS level I and II showed less consistency of direction-specific anticipatory postural adjustments (Liu et al. 2000) and more distally posteriorly (gastroc-nemius) muscle onset initially as compared to the more typically distally anterior muscle activation (tibialis anterior) in typically devel-oping children (Zaino 1999).
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CoP trajectories in a stand and reach task in children with spastic di-plegia at GMFCS level II showed greater movement in a me-dial/lateral direction and less in an anterior/posterior direction and increased CoP length than typically developing children; this was done in order to keep CoP well within BoS (Zaino 1999; Liu et al. 2000). Children at GMFCS level III showed activation of anticipatory coordination patterns approximately 400 msec prior to an arm movement as compared to both typically developing children and children GMFCS level I (60 msec). As suggested by Westcott et al. (1998) and Liu (2001) a compensatory mechanism preparing well in advance for internal perturbations caused by the reaching movement which resulted in poor timing of the postural control and the arm movement.
In a reach and stand task on different surfaces children with CP showed more difficulties and variable anticipatory postural adjust-ments compared to typically developing children (Thorpe et al. 1998).
Ankle-foot orthoses in children with CP
Orthoses for lower extremity play an important role in the physical management of children with CP and are primarily designed to prevent deformities and facilitate function (Gage 1991; Morris 2002 b). Children with CP often use orthoses to improve standing and walking functions (Knutson and Clark 1991). See Table 4 for an over-view. Only a few of these studies have focus on non-ambulatory children, who are the target group in this thesis.
Introduction ____________________________________________________ Table 4. An ov erview of studi es on o rthoses for lower extremity in children with CP. Soli d AFO (SAFO ), hinged AFO (HAFO), dynam ic ankle foo t orthosis (DA FO), posterior leaf sp ring (PLS) orthosis, standing, walking and si
tting hip (SWASH) ortho
sis an d sup ra malleolar o rthosis (SMO). Author n Characteristics Orthoses Control Methods/design Key outco m es Ro m k es J , Hell A K, Brunner R. 2006 10 Hem iplegic CP HAFOs Barefoot Experi m ental study .
EMG of lower extrem
ity m u scl es, gait analysis. Changes in m u scle activity
and gait pattern (fro
m toe-gait to a heel-toe g ait). Im proved stri de length, walking
speed and kinem
atics in loading response.
Em bre y DG, West cott SL. 2006 Abstract 10 Spastic diplegia SWAS H No SWASH Repeated m easure s design. EMG data collected
in sitting and standing, 10 s. and while walking 20 feet.
SW
ASH did not increase
adductor
muscle tone.
Radtka SA, Skinner SR, Johanson EM. 2005
12 Spastic diplegia HAFOs SAFOs HAFOs Repeated m
easures design. Muscle tim
ing, joint m o tions, m o m ents
and powers and tem
poral-distance characte ri stics were m easure d.
Both orthoses coul
d be used to im
p
rove the position in
stance. The
HAFOs would be reco
mm ended to produce m o re nor m
al patterns during term
inal
stance and
pre-swing in gait. Lam WK, Leong JC, Li YH , Hu Y, Lu WW. 2005 13 Spastic CP AFOs DAFOs Motion analysis wi th EM G, evaluatio n of the bio m echanical
and EMG effects of AFOs and
DAFOs in gait
.
DAFOs had the ad
vantage of less restriction on ankle
m
ove
m
ent, which avoids m
u scular atrophy and im p roves orthotic co m p liance. Park ES , Pa rk CI,
Chang HJ, Choi JE, Lee DS. 2004
19 Spastic diplegia HAFOs Barefoot Before -after trial. Tem poral, kinem atic and
kinetic data were c
o
llected during sit-to-stand
transfers barefoot and with HAFOs.
HAFOs contributed to so m e i m p rovem ents of tem poral, kinem
atic and kinetic para
m
ete
rs and they
are beneficial for s
it-to-stand transfer
activity in
children with spastic diplegia.
Buckon CE, Sienko Tho
m as S, Jakobson-Huston S, Moor M, Suss m an M, Aiona M. 2004 16 Spastic diplegia SAFOs HAFOs PLS HAFOs PLS SAFOs Barefoot
Gait analy
sis, oxygen consu
m ption and functio nal outco m e m easures.
All AFO configurations nor
m
ali
zed ankle kinem
atics
in stance, increas
ed
step
/stride length, decreas
ed
cadence and decre
ased energy cost o
f walking. Functionally all AFOs im proved the execution of walking/running/jum p
ing skills, upper extre
m it y coordination and fi ne m o tor speed/dexterity . La m p e R , Mitterna cht J, Schrodl S, Gerdes m eye r L , Natrath M, Gradin ger R. 2004 18 Spina bifida CP Orthopaedic shoes Insoles Orthoses for lower extre
m it y W ithout orthopaedic device Experim ental study . EMG, kine m atics and
kinetics of the gait, especially of the knee joint, were analyzed.
The orthotic devices im
proved the feeling of gait
stability of the patients. Various but li
ttle effects on the
kinem
atics and kinetics of the knee joint. Individual
findi
ngs, of restricted general significance.
W
esdock KA, Edge
AM. 2003
11
Spastic CP Crouched posture SAFOs Wedged shoes + AFOs
(WAFOs ) No orthoses Experim ental study , 8
weeks. Knee extension:
goniom
eter. Duration of stan
ding bala nce: stopwatch. W A FOs i m p
roved unassisted standin
g balance
co
m
p
ared with
no orthoses and SAFOs alone (in four
children) W h ite H, Jenkins J, Neace WP , T y lkowski C, Walker J. 2002 115 CP Diplegia n=97 Hem iplegia n=18 HAFOs SAFOs Barefoot A retrospective study . Three di m
ensional gait analysis.
Tem
poral and spatial gait para
m
eters
significantly
increased with the
use of bot
h ty
pes of AFOs versus
barefoot walking. Kott KM , Held SL . 2002 28 CP
AFOs for upright skills and am
bulati on W ithout orthoses Standardized walk
ing obstacle course (S
W O C), pediatric balance s cale (PB S), perform ance self-reports of co m fort and stability. No significant bet ween SW OC and PBS. 18% perform ed better o n
an individualized goal with their
orthoses and 48%
reported m
o
re
co
mfort and stability
Introduction ____________________________________________________ Table 4. An ov erview of studi es on o rthoses for lower extremity in chil dr HQ ZLWK&3 «« ««« FRQWLQXHG Ro m k es J , Brunner R. 2002 12 He m iplegic CP
DAFO HAFO with
blocked
ankle plantarflexion
Barefoot
Gait anal
ysis, sagit
tal plane kine
m
atic
and
kinetic data of walking were co
m
p
ared.
DAFO did not im
p
rove gait significantly
whereas the
HAFO
did. HAFO changed toe walking into a heel-toe
gait. Dursun E, Dursun N, Alican D. 2002 24 Spastic CP patient s with dy nam ic equinus. AFOs Barefoot Experi m ental study . Videotape recordings
barefoot and with AFOs. Clinical
Ga it Assess m ent Score . Children (CP) with dy nam ic equinus deform ities can benefit fro m AFOs for am bulation. Ekblo m B, My hr U. 2002 4 Spastic diplegia
Hip abduction orthosis
5 controls Muscle activit y m easured by surface EMG . Hip abduction angle m easured by a gonio m eter. Sitting Assess m ent Scale, videoanalysis.
No significant differences in EMG voltage under different sitting conditions, with or without hip abduction ortho
sis. May i m p ly that if a functional
sitting position is assured, further addition of an orthosis is not needed.
S m ile y SJ, Jacobsen FS, Mielke C, Johnston R, Park C , Ovaska GJ. 2002 14 Spastic diplegia
SAFOs HAFOs PLSOs
Shoes
Gait analy
sis,
Energy
Efficiency
Index data and
individual preference.
No significant differences in
velocit
y, cadence, stride
length or in the Energy
Efficiency In dex. Eight children preferred articulated brac es, six chose PLS,
none chose the SAFOs.
Buckon CE, Sienko Tho
m as S, Jakobso n-Huston S, Moor M, Suss m an M, Aiona M. 2001 30 Spastic he m iplegia
HAFOs SAFOs PLSOs
W ithout orthoses Gait analy sis, R O M, energy consu m ption and functional m o tor s k ills were assessed. Im prove m ents in functional m obility were greatest in the HAFOs and PLSOs. Beals RB. 2001 4 Non-am bulatory
children with spastic CP
AFOs set at 90 q W ithout AFOs
Sitting on a bench, sagittal i
m
ag
e pro
jected onto
a piece of paper on the wall. Tracings were made of the shadows of the trunks, with and without AFOs. Pos
terior pelvic tilt
,
displacem
ent of the apex of ky
phhoti
c curve and
the sitting angle were
m
easured.
The a
m
ount of kyphosis in sitting, in nona
m
buatory
children with CP,
can be decreased
with the use of
AFOs set at 90 q. Crenshaw S, Herz og R,
Castagno P, Richards J, Mille
r F , Michal oski G, Mo ra n E. 2000 8 Spastic diplegia HAFOs HAFOs + inhibitive foot plate SMOs Barefoot Prospective study W
ithin subject design.
Changes in
m
u
scle
activity
and gait pattern (fro
m toe-gait to a heel-toe g ait). Im proved stri de length, walking
speed and kinem
atics in loading response.
Burtner PA, Woollacott MH, Q
u
alls
C. 1999
4
Spastic diplegia
SAFOs Spiral-graphite (dyna
m ic ) AFOs W ithout AFOs 4 controls
EMG and kinem
atic data collected
and
co
m
p
ared between
groups and in three orthotic
conditions.
The results support the use of DAFOs
to correct skeletal m al -alignm en t in children w ith spastic diplegia. Rethlefsen S, Kay R, Dennis S, Forstein M, Tolo V. 1999 21 Spastic diplegia SAFOs HAFOs HAFOs SAFOs Shoes
Gait anal
ysis.
Greate
r dorsiflexion occurred at initia
l contact with
both SAFOs and HAFOs than shoes alone. Dorsiflexion at term
in
al stance
was g
reatest in
HAFOs.
HAFOs are approp
riate as
long as adequate range of
m o tion is available . Abel MF , Juhl GA , Vaughan CL, Da m iano DL. 1998 35 Spastic diplegia AFOs Barefoot Retrospective, cros s-sectional assessm en t.
Barefoot and AFO gait analy
sis, te
mporal-distance factors and sagittal kine
m ati cs. Co m p
ared with barefoot gait, AFOs
enhanced gait
functio
n in diplegi
c subjects. Benefits resulted fro
m elim ination of prem ature pl antar flexion and im pr oved progression of foot
contact during stance.
Hainsworth F, Harrison MJ , Sheldon TA, Roussounis SH. 1997 12 CP AFOs W ithout AFOs
Clinical trial. Range of ankle dorsifle
xion.
Video analysis. Mediolateral shea
r force, using a Kist
ler force
plate.
ROM and gait deteriorated
during the periods without
Introduction ____________________________________________________ Table 4. An ov erview of studi es on o rthoses for lower extremity in chil dr HQ ZLWK&3 «« ««« FRQWLQXHG Carlson W E , Vaughan CL, Da m iano D L , Abel MF. 1997 11 Spastic diplegia SAFOs SMOs Shoes Gait anal ysis, four ca m
eras and two f
o rce plates. Ti m e-distance, kin em
atic and kinetic
param
eters
were obtained for
each condition.
SAFOs did offer so
m
e bio
m
echanical benefits to the
child with spastic diplegia
. SMOs appeared to have very littl e m easura ble effect.
Radtka SA, Skinner SR, Dixon DM, Johanson ME. 1997
10
Spastic CP, 6 w
ith
diplegia and 4 with hem
iplegia
DAFOs SAFOs SAFOs DAFOs Without orthoses
Repeated m easure s. Lower-extre m ity m u scl e ti m ing, joi nt m o tions and te m poral-dista nce characte ristics were co m p ar ed.
Both orthoses increased
stride length, decreas
ed
cadence and reduced excessive plantar flexion. No differences were found when co
m
p
aring the two
orthoses. Wilson H, Haideri N, Song K, Telfor d D. 1997 15 Spastic diplegia HAFOs SAFOs Barefoot Controls
Evaluation of effects of the orthoses o
n the transitional m ovem ent of sit-to-stan d. Kine m ati c
and kinetic data. Ti
m
e to
reach stable
standing.
Children with spastic diplegia with uncontrolled dynam
ic
equinus b
enefit fro
m
the use of HAFOs for
the
m
ovem
ent of s
it-to-stand.
Öunpuu S, Bell KJ, Davis RB,
De Luc a PA. 1996 31 Unilateral (19) and bilateral (12) CP PLS Barefoot
Retrospective.Gait analysis to dete
rmine the
orthosis effect on a
nkle functio
n.
PLS reduces exces
sive equinus in swi
ng phase and
allow ankle dorsiflexion in
m idstance. Carm ick J . 1995 1 Spastic diplegia HAFOs SAFOs SAFOs HAFOs
Prospective, single case study. Physic
al therapy,
photo
graphs, ROM, functional tests.
SAFOs blocked needed foot and ankle
m
obility. The
gait im
proved when using HAFOs. B
io
m
echanical
changes can be achieved by
switching fro m SAFOs to HAFOs. My hr U, von W en d t L. 1993 8 C P Abduction or htose s Contr ols
EMG, four leg
m u scles. Perform ing upper-extre m it y task in si
tting, various seat
inclinations.
The use of an abdu
ction orthosis and
horizontal and
forward-leaning seats decrease
lower-extre m it y m u scle activity and it m ig h t also im prove upper-extre m ity functio n. Butler PB, Tho m p son N, Major RE. 1992 6
CP, diplegia and hem
iplegia
SAFOs
Barefoot Shoes
Balance training for four to six
m onths using SAFOs. Gait asses sm ent by video-recording and ground reaction fo rce data. Treat m ent resulted in im pr ovem
ent in posture during
heel-strike and stance phase in shoe and barefoot condition.
Mossberg KA, Lin ton KA, Fr iske K. 1990 18 Spastic diplegia SAFOs W ithout SAFOs Am bulation, heart rate, velocity and d istance .
The energy expenditure of am
bulation at self selected
speed was reduced
using SAFOs. Middleton EA. Hurley GR. M cIlw ain JS. 1988 1 Spastic diplegia HAFOs SAFOs
Single-subject design. Kinem
atic coordinate data, using W A TSMART video sy stem , Kistler
force plate, Jensen´s photogr
am m etric m ethod. HAFOs m o re
effective than SAFOs.
More natural ankle m o tion, greater s y m m etry of seg m ental lower extre m it y m o
tion while wea
ring HA FOs. Harris SR. Rif fl e K. 1986 1 Spastic quadriplegia, AFOs + inhibitive foot plate Barefoot
Single-subject, alternate treat
m ents desi gn. Im provem ents
in duration of standing balance,
sym
m
etry of stance, and ease of
m
aintaining standi
ng
balance during the “with-orthoses” co
ndition. Taylor CL. Ha rris SR 1986 1 Spastic diplegia AFOs + inhibitive foot plate Barefoot
Single-subject design. Assess
m
ent of the
subject´s standing
balance, videotaped test
sessions.
Both qualitative and quantitative changes occurred when using the orthoses, indicating t
h at they m ight im p rove functional m o tor perfor m
ance in children with
Introduction
____________________________________________________
The International Organization for Standardization (ISO) (2003) cate-gorizes the orthoses into upper and lower limb orthoses. The ankle-foot orthosis (AFO) and the ankle-foot orthosis (FO) are two types of lower limb orthoses. The AFO is defined as one orthosis that involves the ankle joint and the whole or part of the foot, and the FO is defined as an orthosis that involves the whole or part of the foot. The AFO provides control or elimination of motion in the ankle and subtalar joint resulting in re-alignment of body segments and thereby theoretically altering the GRF affecting more proximal joints as well (Bartonek and Eriksson 2005).
Different kinds of AFO designs have been used in the management of spastic CP (Morris 2002 a, b; Bartonek and Eriksson 2005), whereas the most common are; the solid (rigid or standard) AFO, the hinged (articulated) AFO and the posterior leaf spring (PLS) AFO. The standard construction of an AFO is without a mechanical ankle joint to place the foot plantigrade (if possible), with the subtalar and the ankle joint in a neutral position thereby restricting movements in dorsi and plantar flexion. The AFO is aimed to compensate for the inability to produce appropriate action/reaction forces by stabilizing the ankle joint and restraining forward translation of the shank. The orthosis is also used to restrain foot deformities such as varus and valgus (Butler and Nene 1991; Bartonek and Eriksson 2005).
The PLS is an AFO with a posterior trimline allowing a slight dorsi-flexion movement since the material allows some dynamics in the ankle joint during the stance phase in walking. The material returns to the original state and the orthosis to neutral position during the swing phase (Bartonek and Eriksson 2005).
The hinged AFO is a modification of the solid AFO with a movable ankle joint maintaining medial and lateral stability at the subtalar joint and foot, allowing some or all ankle motions. A hinged AFO with a dorsiflexion stop allows free plantar flexion but will stop dorsal flexion over the neutral position of the foot (Bartonek and Eriksson 2005).
Introduction
____________________________________________________
Foot Orthoses
The supra malleolar orthosis (SMO) with removed anterior and posterior portions does not cross the ankle joint resulting in medio-lateral stability with free dorsal and plantar flexion.
The dynamic AFO (DAFO) or the tone reducing AFO is a short, very thin, and flexible form fitted SMO that keeps the subtalar joint in neutral position and supports the arches of the foot. The custom countered footplate of the DAFO is similar to that of the inhibitive cast (Duncan and Mott 1983) with built-up areas under the toes, lateral and medial longitudinal arches and transverse metatarsal arch, and recessed areas under the metatarsal and calcaneal pad areas to provide support and stabilization to the arches, of the foot and position the midtarsal and subtalar joints in a neutral position. A toe strap stabilizes the first digit and an ankle strap holds the heel within the orthosis (Hylton 1990).
The rationale for the purpose, design and use of the inhibitive AFO is proposed to be based on the inhibitory or tone reducing cast concept (Hylton 1990; Duncan and Mott 1983). The footplate is designed to reduce abnormal muscle activity, improve proprioception and to effect biomechanical changes such as decreased ankle plantar flexion and improved motions of the lower extremity, pelvis and trunk during standing and walking.
Since the DAFO provides minimal support and stability around the foot, it is thought to improve function, postural control and balance reactions that are learned by unrestricted neural feedback mechanisms (Hylton 1990). According to the Hylton (1990) concept there are dif-ferent types of DAFOs, i.e. the standard DAFO, a modified SMO, the DAFO with a plantarflexion stop, and the DAFO with dorsi-flexion stop. In this thesis we focused on the standard DAFO (Figure 2).
Introduction
____________________________________________________
Figure 2. Dynamic ankle-foot orthosis (DAFO).
Researchers have documented improvements in gait efficiency in children with spastic diplegia using solid AFOs (Carlson et al. 1997; Radtka et al. 1997, 2005; Rethlefsen et al. 1999; Buckon et al. 2004; Lam et al. 2005) and hinged AFOs (Brunner et al. 1998; Crenshaw et al. 2000; Ferdjallah et al. 2000; Romkes and Brunner 2002; Buckon et al. 2004; Radtka et al. 2005). However, SMOs did not improve toe walking (Carlson et al. 1997; Crenshaw et al. 2000).
By comparing solid AFOs, hinged AFOs and PLS, Buckon and colleagues (2004) found that children with spastic diplegia could benefit functionally from all three orthoses by improved walking characteristics such as normalized ankle kinematics, increased step length and decreased energy cost of walking. In contrast, when Smiley and co-workers (2002) compared walking with solid AFOs, hinged AFOs, PLS and shoes only, they found no significant differences in gait efficiency (velocity, cadence, stride length and energy cost) between the four conditions.
Introduction
____________________________________________________
The ability to move from sit to stand in children with spastic equinus improved using hinged AFOs (Wilson et al. 1997; Park et al. 2004) and solid AFOs (Wilson et al. 1997) compared to barefoot condition. Studies comparing DAFOs to other orthotic conditions have revealed various results. Radtka and co-workers (1997) found reduced equinus and increased walking speed in spastic diplegic children using both DAFOs with a plantar flexion stop and solid AFOs compared to barefoot condition, but no differences between the orthotic condi-tions. Romkes and Brunner (2002) showed that DAFOs did not improve gait significantly whereas the hinged AFOs did by control-ling plantarflexion, i.e. decrease plantarflexion which leads to increase step and stride length, in children with hemiplegic CP. Burtner and co-workers (1999) suggested that the use of solid AFOs in children with spastic CP decreased recruitment of ankle strategies for postural adjustment during perturbed standing, whereas DAFOs did not. Furthermore, they concluded that DAFOs can be preferred to solid AFOs in correcting mal-alignments. Lam and colleagues (2005) stud-ied a group of children with spastic CP wearing solid AFOs and DAFOs and reported longer stride length, pre-positioning for initial heel contact and controlled plantar flexion during swing phase in both orthotic conditions. The DAFO was reported to have less restriction on the ankle movement, which according to the authors minimizes atrophy of the leg muscles (Table 4).
Reaching performance
Typically developing children
From a motor control perspective reaching movements in adults consist of two phases. The first phase, the transport phase, is a ballistic movement of the arm towards the target that covers most of the reaching distance without visual feedback. The second phase is visually guided, and involves the arm transporting the hand to an object as the hand forms the grip characteristics that are needed to grasp the object (Jeannerod 1997). Chieffi and Gentilucci (1993) found that regardless of object size and distance to the object the formation of the hand starts approximately two-thirds of the total
Introduction
____________________________________________________
movement time. Bell shaped velocity profiles reflect that the start and stop are planned prior to the movement onset. For structuring early infant reaching, von Hofsten (1991) has described reaching in terms of movement units (one acceleration and deceleration phase) as earlier described by Jeannerod (1984).
When children start to reach around 3-4 months of age, one reaching movement consists of several (3-7) movement units (Fallang et al. 2000). The characteristics of the reaching movement change with increasing age. Children aged 12 years have, like adults, a decrease of movement units (Kuhtz-Buschbeck et al. 1998) and of the length of the displacement path of the hand (Fallang et al. 2000) as well as an increase of the straightness of hand trajectory (Kuhtz-Buschbeck et al. 1998; Schneiberg et al. 2002) and movement velocity (Kuhtz-Buschbeck et al. 1998). Rösblad (1996) found that the movement tra-jectory path and the movement time were longer in children aged 6-12 years without visual feedback from the hand and target compared to older children. However, the peak velocity was not affected by the amount of visual information. Kuhtz-Buschbeck and colleagues (1998) found in a reaching and grasping task in children 4-12 years that children did not show dependency on visual feedback despite age but the absence of visual information shortened the acceleration phase and lengthened the deceleration phase. Furthermore, according to Bertenthal and Hofsten (1998) postural control, such as control of the head and trunk is a foundation for development of the reaching movement.
Children with CP
In children with CP reaching movements are characterized by multijoint dyscoordination leading to abnormal movement trajectories (Shumway-Cook and Wollacott 2001). However, little is known about the kinematic characteristics of reaching. Reaching kinematics have been investigated mostly in children with spastic hemiplegia (Steenbergen et al. 1996, 1998, 2000; Utley and Sugden 1998; Van Thiel and Steenbergen 2001; Volman et al. 2002) showing longer movement time, a lower peak velocity and less smooth reach tra-jectories comparing the least affected arm to the most affected. Steenbergen and Van der Kamp (2004) showed that the reaching
Introduction
____________________________________________________
movement in children with CP showed multiple segmentation and concluded that the motor planning of the reaching movement seemed to be organized in a stepwise way by visual feedback. Children with CP aged 4-18 months showed in a longitudinal study that reaching performance improved with increasing age and was related to postural control of the trunk (Hadders-Algra et al. 1999 b). In a study involving sitting children 2-11 years with spastic hemiplegia and bilateral CP the result showed significantly worse quality of reaching related to severity of CP, i.e. longer movement time and more movement units compared to typically developing children (Van der Heide et al. 2005). This was also true in children with spastic quadriplegic CP aged 7-12 years (Fetters and Kluzik 1996). Furthermore, Chang and co-workers (2005) found that in a group of children with spastic hemi-, di- and quadriplegia in sitting, the number of movement units was the most sensitive kinematic variable to discriminate between normal and spastic reaching.
Laboratory measurements of postural control
Laboratory measurements of movements, forces and muscle activity can provide us with objective and systematic information about how the nervous system acts to control and adjust posture by measuring performance parameters, i.e. how the person performs a task (Latash 1993).
Kinematics
Kinematic measures refer to the principles of motion without regard to force or mass. The most common of such descriptors refer to displacement (changes in position), velocity (speed), and acceleration (changes in speed). Kinematic measures are performance production measures that are based on recording the movement of specific body segments while the person is performing a task. Camera based systems involve either passively reflective or actively signalling markers placed on anatomical landmarks of specific body segments. When viewed from the camera the instantaneous three-dimensional position of the markers in relation to the fixed laboratory coordinate system can be determined (Kaufman 2004). In children with CP
Introduction
____________________________________________________
kinematic analysis has allowed clinicians and researches to examine variations of interventions, among them orthoses, during gait (Crenshaw et al. 2000; Buckon et al. 2001; Dursun et al. 2002; Romkes and Brunner 2002; Smiley et al. 2002; Lampe et al. 2004; Radtka et al. 2005) and during sit-to-stand transfer (Park et al. 2004). Kinematic analysis has also proved to be promising in investigation of sitting postural control (Van der Heide and Hadders-Algra 2005) and reaching performance (Chang et al. 2005; Van der Heide et al. 2005) in children with CP.
Kinetics
In the study of motion, the term kinetics refers to force as a course of motion. In laboratories commonly force plates are used to measure the GRF involved in the interaction between a person and the ground. During quiet stance a person exerts a force (action force) which is equal to body mass multiplied by the acceleration of gravity (Enoka 2002). Force plates measure variables such as the magnitude of forces and displacement of CoP. Researchers have studied by using force plates, gait (Buckon et al. 2001; Romkes and Brunner 2002; Lampe et al. 2004; Radtka et al. 2005) and standing postural control (Burtner et al. 1999) with orthoses, and the effect of balance training on standing stability (Shumway-Cook et al. 2003) in children with CP. Electromyography
Movement involves electrical activity in the muscles which can be measured by electromyography (EMG), This involves surface electrodes on the skin over muscles or inserting fine wire electrodes into a specific muscle (Basmajian 1979; Söderberg and Knutson 2000). EMG can be used in a variety of ways, one that is most relevant to postural control issues is the use of EMG to indicate when a muscle begins and ends activation (Hermens et al. 1999). No standard procedure for determination of EMG onset has been described (Hodges and Bui 1996; Hermens et al. 1999). Furthermore, the EMG onset is also influenced by signal processing such as the use of low-pass filtering and the sampling frequency (Hodges and Bui 1996). Several researchers have used EMG recordings to study gait with AFOs (Radtka et al. 2005; Lampe et al. 2004; Romkes and
Introduction
____________________________________________________
Brunner 2005), standing with (Burtner et al. 1999) and without orthoses (Burtner et al. 1998; Wollacott et al. 1998) and postural adjustments in sitting (Brogren 1996; Brogren et al. 1998, 2001; Hadders Algra et al. 1999 a; Ekblom and Myhr 2002; Van der Heide et al. 2004) and standing (Roncesvalles et al. 2002) in children with CP.
Rationale for this thesis
The purpose of different interventions addressing children with CP is to improve postural control and thereby gain more functional motor performance that will have spin-off effects on daily, school and recreational activities (Westcott and Burtner 2004). Furthermore, there is a need to study the efficacy and effectiveness of these interventions (Harris and Roxborough 2005). Lower limb orthoses such as DAFOs have an important role in the postural control management concerning children with CP (Morris 2002 a, b). DAFOs are often prescribed for daily use, 4-6 hours per day in order to prevent deformity and to obtain more normal proprioceptive feedback in order to improve postural control and balance reactions during sitting, standing and locomotion. Since there is a need for scientific evidence for the use of DAFOs effects on mechanisms underlying postural control the rationale behind this thesis was to investigate the effects of DAFOs on postural control in children with CP. This thesis focused on parent´s perspectives and experimental studies on DAFOs effects on mechanisms underlying postural control. The initiate study (study I) focused on parents´perceptions about DAFOs. The parents informed that DAFOs had positive effects on postural control and these effects did benefit the child in activities of daily living. An interesting question that arose was whether these positive perceptions experienced by the parents, could also be objectively verified in experimental studies.
Aims
____________________________________________________
AIMS
The general aim of the present studies in this thesis was, through quantitative and qualitative methods, to gain knowledge about the effects on postural control and reach kinematics in children with spastic diplegia wearing DAFOs.
The specific aims were
x to explore how parents of children with spastic diplegia expe-rienced the use of DAFOs (study I)
x to investigate whether DAFOs improve standing posture and support base conditions in children with spastic diplegia (study II)
x to assess if children with spastic diplegia wearing DAFOs who are not able to master free stance make use of anticipatory postural adjustments when reaching to target (study III)
x to evaluate the coordination between target reaching
kinematics and postural adjustments revealed by ankle muscle activity and ground reaction forces in children with severe spastic diplegia wearing DAFOs (study IV)
x to investigate reaching kinematics in children with severe spastic diplegia wearing DAFOs (study IV)
Methods
____________________________________________________
METHODS
The research in this thesis applied both qualitative and quantitative methods and the choice of method was guided by the research questions. In study I the aim was to explore the parents´ experiences of their children´s use of DAFOs through a qualitative approach. The results of the first study raised further research questions. It was obvious that parents experienced mainly positive effects of DAFOs. With these results in mind we objectively investigated by using quan-titative methods the effects of DAFOs in children with spastic diplegia in an experimental setting. This was done in studies II-IV. Study design, participants, data collection and analysis are outlined in Table 5.
Table 5. Summary of study design, participants, data collection and analysis (studies I-IV).
Study Participants Study design, data collection and analysis I. Parent´s perception of DAFOs 15 parents of children with spastic diplegia wearing DAFOs
An explorative descriptive study design with an open-ended interview. Analysis through qualitative content analysis.
II. The effects of DAFOs on standing posture and weight distribution 6 children with spastic diplegia wearing DAFOs
An experimental study design in a laboratory setting recording kinematics, ground reaction forces with a three-dimensional optoelectronic movement analysis system and two force plates.
Descriptive and non-parametric statistics were used.
III. The effects of DAFOs on CoP displace-ment and anticipatory postural adjust-ments 4 children with spastic diplegia wearing DAFOs and 8 typically developing children
An experimental study design in a laboratory setting recording kinematics, ground reaction forces with a three-dimensional optoelectronic movement analysis system and two force plates.
Descriptive statistics were used. IV. Reach performance and postural adjustments wearing DAFOs during different support con-ditions 6 children with spastic diplegia wearing DAFOs and 6 typically developing children
An experimental study design in a laboratory setting recording kinematics, ground reaction forces and muscle activity with a three-dimensional optoelectronic movement analysis system, two force plates and electromyography (EMG).
Descriptive and non-parametric statistics were used.
