In the Driver’s Seat: A Randomized, Crossover Clinical Trial Protocol Comparing Home and Community Use of the Permobil Explorer Mini and a Modified Ride-On Car by Children With Cerebral Palsy

Abstract

Objective

The aims of this study are 2-fold: (1) to evaluate a powered mobility intervention to promote developmental, activity, and participation outcomes of young children aged 12 to 36 months who have cerebral palsy; and (2) to compare the use patterns (frequency, duration, environment) of 2 different powered mobility options.

Methods

This study is a multisite, mixed-methods, doubly counterbalanced, randomized, crossover clinical trial, where intervention A is the Permobil Explorer Mini and intervention B is a modified ride-on toy car. The study will take place in rural and urban home and community settings surrounding 3 sites (Washington, Oregon, and Michigan). There will be 24 child-caregiver dyads in the study (8 dyads per site). Primary outcome measures include the Bayley Scale of Infant and Toddler Development, the Youth and Children’s Participation and Environment Measure, the Assessment for Learning Power mobility use, automated device use tracking logs, caregiver semistructured interviews, and the Acceptability, Feasibility, and Intervention Appropriateness Measures. Secondary measures include the Child Engagement in Daily Life and caregiver diaries.

Impact

The use of powered mobility devices for young children with cerebral palsy has gained traction, with evidence that the use of powered mobility at young ages complements (rather than detracts from) other interventions focused on more traditional mobility skills such as crawling and walking. However, research is limited, and often comprised of low-level evidence. Given the clearance of the first powered mobility device for infants, the Permobil Explorer Mini, and the recent popularity of modified ride-on toy cars as an alternative for powered mobility for young children with disabilities, this study will contribute to rigorous examination of the developmental outcomes, use patterns, and caregiver perceptions of these novel devices.

Introduction

Millions of children in the United States (6% of all children under the age of 18) have disabilities, and the prevalence of mobility disabilities among children has continued to rise over the last decade.¹ An estimated 10,000 newborns in the United States are diagnosed with cerebral palsy each year, and approximately 764,000 people in the United States are living with cerebral palsy.² Children with cerebral palsy often have delays in self-initiated mobility (eg, walking), and across the lifespan may use mobility devices (wheelchairs, walkers, or crutches) to increase independent mobility and enhance participation.^3,4

Regardless of how it is achieved, self-initiated mobility is a fundamental human right and essential for all children to access their world and achieve meaningful participation in family and community life.^5–10 This is especially important for young children with cerebral palsy, who are often dependent upon adults to provide them access to mobility experiences.^5,11 Mobility technology, such as manual and power wheelchairs, scooters, and more recently, modified ride-on toy cars, have a positive impact on developmental skills such as communication and cognition, self-care, mobility, and participation in the home and community.^8,12–14 Further, introduction of mobility technology reduces caregiver stress and lessens the need for caregiver support of the child’s participation.^14,15 Powered mobility provides a unique opportunity for young children with cerebral palsy to use self-initiated mobility to explore the environment and simultaneously work on therapeutic goals related to body function, activity, and participation. This holistic approach contrasts standard care interventions within pediatric rehabilitation, which may focus on one physical skill in isolation of other therapeutic goals.¹⁶

Unfortunately, multiple factors limit the use of powered mobility for young children with cerebral palsy, including an historic rehabilitation focus on walking as a preferred mode of mobility, shortcomings in the design and availability of pediatric mobility technology, stigma and attitudinal barriers, potential safety concerns, and a lack of accessibility in physical and social environments.^5,17–20 For example, issues of stigma, perceptions of powered mobility as a “last resort,” and fears that the use of powered mobility will interfere with motor skill acquisition persist among many families and clinicians alike, despite evidence demonstrating that gains in mobility and cognitive skills, including walking, are actually enhanced following the introduction of a powered mobility device.^13,21–23 Further, although universal design is improving, an ongoing lack of accessibility in the built environment coupled with size and bulk of devices adds layers of complexity for families navigating everyday life, such as transporting large pieces of equipment or having to preplan accessible routes and locations.^24–26 As a result, young children with cerebral palsy are less likely to have access to powered mobility devices, thereby limiting their engagement in self-initiated mobility experiences, decreasing social interactions with caregivers and peers, and increasing the likelihood of secondary cognitive and developmental delays.^9,27

Two powered mobility device options designed for young children show promise for improving access to these critical self-initiated mobility and exploration experiences at ages similar to their peers without disabilities. First, cleared by the US Food and Drug Administration in March 2020, the Permobil Explorer Mini (Permobil AB, Timrå, Sweden) is a powered mobility device for use in children 12 to 36 months of age with mobility limitations. Second, modified off-the-shelf, battery-operated ride-on toy cars are a nontraditional powered mobility device that have been widely used for children in this same age range.^5,28,29 Existing evidence supporting use of powered mobility in young children, however, is limited to 1 US randomized controlled trial¹³ and multiple studies providing lower levels of evidence.^29–34 Further, there is little to no evidence in the literature describing the potential advantages or intervention benefits of ride-on toy cars compared with the Explorer Mini. We hypothesize that fundamental differences may exist in outcomes related to control mechanism (a single, all-or-nothing switch on the ride-on toy car vs a proportional joystick on the Explorer Mini), device turning radius (large turning radius for the ride-on toy car vs 360-degree turning radius for Explorer Mini), driving position (seated in a ride-on toy car vs seated or standing in an Explorer Mini), variety of driving environments, and differing perceptions of device aesthetics. Additionally, it is rare that children have access to these different devices for long-term trials. Thus, given the time-limited environment of family life and resource-limited environment of contemporary clinical practice, the primary aims of this study are to: (1) evaluate a powered mobility intervention to promote developmental activity and participation outcomes of young children with cerebral palsy; and (2) compare the use patterns (frequency, duration, environment) of 2 different powered mobility options—the Permobil Explorer Mini and a modified ride-on toy car. Our hypotheses are: (1) Participation in a powered mobility intervention will result in significantly improved cognitive, language, motor, social-emotional, and adaptive behavior development as well as improved participation and self-care skills. (2) The Explorer Mini will be used more frequently, for a longer duration, and in more environments than a modified ride-on toy car.

We will also conduct a qualitative investigation to generate new knowledge from caregivers about the advantages and disadvantages of both powered mobility devices, and future hypotheses or research questions. To increase the level of evidence, these objectives will be addressed via a mixed-methods, doubly counterbalanced, randomized, crossover clinical trial. Primary outcomes will include developmental outcomes and data from automated device use tracking. Secondary outcomes will include participation outcomes, semistructured caregiver interviews, driving assessments, driving diaries, and intervention acceptability measures.

As shown in Figure 1, this clinical trial employs 2 intervention conditions, condition A (use of the Explorer Mini) and condition B (use of the modified ride-on toy car). The study will be conducted at 3 sites (Washington, Oregon, and Michigan). These sites are based on the complementary expertise and experience of the researchers and will provide geographic, socioeconomic, ethnic, and cultural diversity within the participant pool. All participants at all sites will undergo the same research procedures. All study activities will be carried out in the children’s homes.

Figure 1.

Study design and timeline flow diagram. This study is a randomized, crossover clinical trial in which each participant will be randomized into 2 groups per study site based on device, with condition A being the Explorer Mini and condition B being a modified ride-on toy car. Study procedures will be conducted at baseline (T0), mid-study (T1), and final study (T2).

Methods

This protocol has been developed in accordance with the Standard Protocol Items: Recommendations for Intervention Trials (SPIRIT) checklist.³⁵ All study procedures have been developed and will be supervised by 3 site principal investigators; 2 (H.A.F and L.K.K.) are PhD trained, licensed physical therapists and board-certified pediatric clinical specialists, and the third (S.W.L.) has a PhD in kinesiology and has completed a 2-year postdoctoral research fellowship in pediatric rehabilitation. All site principal investigators have extensive expertise in pediatric powered mobility research as well as mixed methods data collection and analysis.

Participants

Twenty-four child-caregiver dyads (8 at each site) will participate in this study. Each child will be between 12 and 36 months of age and have a diagnosis of cerebral palsy or be at risk of cerebral palsy (including static encephalopathy) according to birth history and current developmental status. See Table 1 for inclusion criteria. It is important to note that powered mobility readiness was intentionally omitted from study inclusion criteria due to: (1) the focus on self-initiated mobility and exploration (rather than goal-directed driving) for the age group in the current study⁹; (2) past research from our study team and others reporting successful powered mobility use by children not considered traditional “candidates” based on cognitive status^29,30,36; and (3) the application of contemporary understandings of mobility and learning based on developmental and neuropsychological theories such as grounded cognition that preclude the need for predetermined baseline skills.^16,37

Table 1.

Study Inclusion Criteria and Rationale^a

Participants	Criteria	Rationale/Documentation
Children	1. Age 12–36 mo 2. Have a diagnosis of CP (including static encephalopathy) or be at risk of CP due to birth history and current developmental status 3. Be able to maintain a seated position with or without support 4. Be able to tolerate upright sitting with or without support while moving through space for 30 min	Assessed by caregiver report during screening Because early CP diagnosis varies based on access to health care specialists and presentation of the child, the research team is intentionally including children with signs and symptoms of CP in addition to children already diagnosed
Caregivers	1. Age 18 y or older 2. Be the legal guardian of the child participant and reside in the same household as the child 3. Must be able to communicate proficiently in English	Documented by researcher during phone and in-person visits To ensure safety of the child and effective communication by caregivers about their child’s use of devices in home environments

^a CP = cerebral palsy.

It is expected that child participants will exhibit gross motor function commensurate with a Gross Motor Function Classification System (GMFCS) level II–IV.³⁸ Inclusion criteria will be assessed via caregiver report using screening questions. Functional classification systems (eg, the GMFCS, Mini-Manual Ability Classification System, Communication Function Classification System, and the Mini-Eating and Drinking Ability Classification System) will be used as appropriate to create participant profiles.^39–42 For participants who are at risk of cerebral palsy or who have not formally been diagnosed with cerebral palsy, descriptors related to gross motor ability, manual ability, communication ability, and eating and drinking abilities will be obtained via caregiver report, using a standardized written prompt with terminology consistent with the descriptions used in the above classification systems.

Recruitment and Randomization

Participant recruitment will occur continuously until 8 child-family dyads are recruited for each site. Recruitment will be conducted through local agencies and early intervention clinics at each site, and potential participants will self-select to contact the research team and be screened for eligibility. Once enrolled, randomized assignment to intervention A (Explorer Mini) or intervention B (modified ride-on toy car) will occur at each site on the individual child level. Randomization will be doubly counterbalanced by site and device order. Using Proc SurveySelect in SAS 9.4 (SAS Institute, Cary, NC, USA), a simple random sample without replacement will be used to split participants at each site (n = 8) into 2 groups based on intervention. This process will be repeated for each site. The resultant 3 randomization schemes will be randomly assigned (without replacement) to the 3 sites. At each site, the randomization scheme for each participant will be placed in a sealed envelope. As a participant is enrolled at each site, the site principal investigator will blindly select an envelope (without replacement) to determine the intervention order for the specific participant at the specific site. To avoid a testing effect, Proc SurveySelect in SAS 9.4 will be used to randomize the administration order of 5 out of 6 outcome measures at each testing session (T0, T1, T2). A sixth measure evaluating the appropriateness and feasibility of each intervention will be administered last at each appropriate testing session (T1 and T2) to avoid caregivers’ perceptions of a device potentially influencing their responses to other measures.

Intervention

All participants will randomly receive both intervention A (Explorer Mini) and intervention B (modified ride-on toy car) during the study. Three research sessions will be scheduled during the study. The baseline session (T0) will consist of initial device training (either the Explorer Mini or modified ride-on toy car as determined by the randomization procedures), home safety and accessibility, and device safety checkoffs to determine appropriate driving locations, and administration of outcome measures. If a participant’s home allows for only limited use of the devices, alternative driving locations (ie, garage, sidewalk, park path, school blacktop, etc) will be identified. Safety and training videos for each device will be used to supplement in-person training and will allow caregivers to review safe device use procedures as needed during the study. Intervention phase 1 will take place for 8 weeks, followed by a mid-study assessment (T1) at which time outcome measures will be repeated and caregiver perception/satisfaction with the device will be assessed. Training and home and safety checkoffs on the second device will occur. No washout period between intervention phases is indicated because both interventions provide self-initiated mobility. Intervention phase 2 will take place for 8 weeks, followed by the final study assessment (T2), where devices will be removed from the participants’ homes and a final set of outcome measures will be administered. During each 8-week study phase, the researchers will conduct 2 virtual check-ins with each family to answer questions and provide support and standard activity suggestions for device use as part of the child’s daily mobility routine (ie, open exploration, switch/joystick play, goal-directed driving if indicated). These check-ins will be structured to allow for standardized support, categorized based on the most common previously identified barriers to device use (child, device, caregiver, and environmental), and using the facilitating strategies based on driver learning level (explore function, explore sequence, and explore performance) provided in Appendix 2 of the Assessment of Learning Powered mobility use (ALP 2.0) instrument literature.^43,44 See Figure 1 for study phases and timeline.

Equipment

Specifications regarding each of the Explorer Mini (Explorer Mini, Permobil AB, Timra, Sweden) and the modified ride-on car, specifically a Fisher Price Lightning McQueen toy car (Fisher Price, East Aurora, NY, USA), are provided in Figure 2.

Figure 2.

Specifications of the Permobil Explorer Mini and the modified ride-on car. FDA = US Food and Drug Administration.

Outcome Measures

All child-caregiver dyads will participate in the same assessments, regardless of crossover assignment. Two primary outcome measures have been identified for the study: the Bayley Scales of Infant Development—Fourth Edition (Bayley-4)⁴⁵ in Aim 1, and automated device use data in Aim 2. The Bayley-4 will be administered and scored by trained assessors (licensed pediatric physical therapists who are board-certified pediatric clinical specialists). Administration will be video recorded and assessors will establish interrater reliability (intraclass correlation coefficient ≥0.80) to indicate an acceptable level of agreement.⁴⁶ Secondary outcome measures for Aim 1 include the Young Children’s Participation & Environment Measure (YC-PEM),⁴⁷ the Child Engagement in Daily Life,⁴⁸ and the Assessment of Learning powered mobility use (ALP).⁴⁴ Secondary measures for Aim 2 include caregiver-reported driving diaries, semistructured interviews, and a 3-measure perceptual implementation outcome survey consisting of the Acceptability of Intervention Measure, the Intervention Appropriateness Measure, and the Feasibility of Intervention Measure.⁴⁹

Drawing from a phenomenological approach aimed at understanding caregivers’ experiences and perceptions of their child’s use of powered mobility, semistructured interviews will be conducted by research team members trained in qualitative methods.⁵⁰ A semistructured interview guide has been created based on findings from the team’s previous qualitative powered mobility research and will be deployed at each study visit to discuss barriers and facilitators to device use, device expectations and performance, and design needs and preferences. Additional details regarding these outcome measures, separated by aim, are provided in Tables 2 and 3, and the full semistructured interview guide has been included in the Supplementary Appendix.

Table 2.

Primary Outcome Measures Pertaining to Aim 1^a

Measure	Administration Time	Description	Rationale for Use	Psychometrics (if Applicable)
Bayley-4b	30–70 min	Therapist administered, comprehensive developmental assessment for children aged 16 d to 42 mo Includes 5 domains: 1. Cognitive 2. Language (receptive and expressive communication subdomains) 3. Motor (fine and gross motor subdomains) 4. Social-emotional 5. Adaptive behavior (including receptive, expressive, personal, interpersonal relationships, play and leisure subdomains)	1. Requires less time to administer than previous versions 2. Recognizes and scores emerging behaviors as well as behaviors that are either mastered or not observed 3. Incorporates caregiver queries into administration and scoring	Excellent reliability (>.93) of normative sample, increased sensitivity to detect children at risk of delay, and excellent correlation (r >.91) with the previous Bayley-3 version45
CEDL	10 min	Caregiver-report measure to describe and evaluate children’s participation in family and recreational activities and self-care (feeding, dressing, bathing, and toileting) Assesses frequency and enjoyment of participation and the degree to which the child participates in the self-care activities	1. Brevity 2. Ease of administration 3. Focus on caregiver-perceived constructs of participation 4. Focus on ease of caregiving	Construct validity, internal consistency, and test–retest reliability in young children with CP (GMFCS levels I–V)64
YC-PEM	20 min	Caregiver report measure evaluating the level of participation and qualities of the environment in which these activities take place For children aged 0 to 5 y Includes 3 sections: 1. Home 2. Daycare/preschool 3. Community	1. Adds multiple contexts of participation 2. Assesses environmental supportiveness within context	Construct validity, internal consistency, and test–retest reliability in children with developmental disabilities and delays (including children with CP)47
ALP	~10–20 min	Therapist observational measure focused on the process of learning to use a powered mobility device Defines 8 phases (ranging from novice to expert) within 3 learning stages: explore function (phases 1–3), explore sequence (phases 4–5), explore performance (phases 6–8) Categories of observation with each phase: attention, activity and movement, understanding of tool use, expressions and emotions, and interaction and communication	1. Brevity 2. Ease of administration 3. Assesses progress of driving capability throughout learning among all learner groups 4. Provides facilitating strategies for learners at each stage 5. Specifically created for powered mobility device assessment 6. Assists in intervention decision-making	Good content validity and qualitative credibility, transferability, and dependability for adults and children with disabilities who are learning powered mobility44

^a Aim 1: to evaluate a power mobility intervention to promote developmental, activity, and participation outcomes of young children with CP. ALP = Assessment of Learning Powered mobility use; Bayley-3 = Bayley Scales of Infant Development—Third Edition; Bayley-4 = Bayley Scales of Infant Development—Fourth Edition; CEDL = Child Engagement in Daily Life; CP = cerebral palsy; GMFCS = Gross Motor Function Classification System; YC-PEM = Young Children’s Participation & Environment Measure.

^b Indicates primary outcome.

Table 3.

Outcome Measures Pertaining to Aim 2^a

Measure	Administration Time	Description
Automated device-use datab	No additional administration time	Frequency and duration of activation, average speed, and distance traveled Collected via a custom data logger (attached to the modified ride-on cars) and a GPS + accelerometer unit attached to the Permobil Explorer Mini
Daily driving diary	<5 min/d	Caregiver form indicating: 1. The date, time, and environment of device use 2. General activities the child engaged in while using the device 3. The child’s enjoyment level
Individual, semistructured interviews	30–45 min	A semistructured interview to explore: 1. Caregiver experiences regarding use of each powered mobility device 2. Perceived barriers encountered and solutions discovered 3. Perceptions of self-efficacy and behavioral capacity Two key questions will provide insight as to caregiver perceptions of their child’s emerging agency and powered mobility devices over time65,66: 1. “Can you describe [child’s name] for me?” 2. “How do you think your child will respond/responded to power mobility training?”Interviews will be audio recorded and transcribed verbatim
A 3-measure perceptual implementation outcome survey: acceptability, appropriateness, feasibility	5 min total	1. The AIM measures acceptability, ie, how receptive stakeholders are to adopting an intervention 2. The IAM measures appropriateness, ie, the suitability of the intervention in a given environment or circumstance 3. The FIM is designed to measure feasibility (how possible and likely stakeholders are to adopt an intervention). All 3 surveys have substantive and discriminative content validity, construct validity, internal consistency, and test–retest reliability.49

^a Aim 2: to compare use patterns of the Explorer Mini and a modified ride-on toy car. AIM = Acceptability of Intervention Measure; FIM = Feasibility of Intervention Measure; GPS = global positioning system; IAM = Intervention Appropriateness Measure.

^b Indicates primary outcome.

Data Management

All data will be stored on a password-encrypted computer and transferred to secure university servers, with the master list of participants and participant codes stored in a separate, locked file cabinet in a locked office. Audio and video recordings will be deleted once data analysis is complete. Only institutionally approved study team members will have access to the data.

Data Analysis

Planned statistical analyses will be conducted using SPSS (version 26.0; IBM, Armonk, NY, USA). Descriptive participant characteristics (eg, age, sex, race/ethnicity, cerebral palsy subtype, GMFCS level) will be summarized as categorical variables. Details regarding all data analysis procedures, separated by aim, are provided in Table 4, including determination of high and low device use frequency groupings for secondary analyses.

Table 4.

Description of Planned Analyses^a

Aims	Description	Planned Analyses	Post Hoc Analyses
Aim 1: To evaluate a power mobility intervention to promote developmental, activity, and participation outcomes of young children aged 12–36 mo who have CP	Descriptive statistics will be calculated for developmental, activity, and participation outcomes Data will be assessed for normality and symmetry. If normality assumptions are met, we will use parametric statistics to examine between- and within-subject effects. If assumptions are not met, we will use the nonparametric equivalent of the planned analyses, including Friedman test for ANOVA and multiple Wilcoxon tests for MANOVAs	Separate 2 (group: 1, 2) × 3 (time: T0, T1, T2) repeated measures ANOVAs will be calculated to determine between- and within-subject changes on mean scores of developmental outcomes (each Bayley subscale) A 2 (group: 1, 2) × 3 (time: T0, T1, T2) repeated measures MANOVA will be calculated to determine between- and within-subject changes on mean scores activity and participation outcomes (YC-PEM, CEDL) Stratification into low- and high-use groups will occur based on mean device use data We will use these stratified groups to run our analyses to determine if device use is related to developmental, activity, and participation outcomes. Separate 2 (group: low use, high use) × 3 (time: T0, T1, T2) repeated measures MANOVAs will be calculated to determine between- and within-subject changes on mean scores of developmental, activity, and participation outcomes Visual analysis will be used to determine if clinically significant differences exist	Bonferroni correction will be used for the planned analyses to control for the type I error rate and determine where the significant differences exist
Aim 2: To compare the use patterns (frequency, duration, environment) of 2 different power mobility options	Descriptive statistics will be calculated for automated device use tracking data, including 95% CIs, for number of driving sessions, duration (min) of driving sessions, and total duration (min) of driving sessions, stratified by device type Variable distributions will be examined to: (1) identify appropriate response variable distributions, (2) screen for outliers, and (3) characterize patterns of data missingness. If assumptions for parametric statistics are met, we will use parametric statistics to examine within-subject effects. If assumptions for parametric statistics are not met, we will use the nonparametric equivalent of the planned analyses, including multiple Wilcoxon tests for MANOVAs Descriptive statistics will be calculated for caregiver diaries and automated device use tracking data to describe home and community use trends for both devices (mean distance traveled, speed, number of mobility bouts, number of controller activations, etc), stratified by device type	A 2 (group: 1, 2) × 2 (time: T1, T2) repeated measures MANOVA will be calculated to determine within-subject changes on the dependent measures of the mean number of driving sessions, mean duration (min) of driving sessions, and summed total duration (min) of device use	Bonferroni correction will be used for the planned analyses to control for the type I error rate and determine where the significant differences exist

^a ANOVA = analysis of variance; Bayley = Bayley Scales of Infant Development; CEDL = Child Engagement in Daily Life; CP = cerebral palsy; MANOVA = multivariate analysis of variance; YC-PEM = Young Children’s Participation & Environment Measure.

Interview recordings will be transcribed verbatim and coded by members of the research team using DeDoose Qualitative Software (SocioCultural Research Consultants, Los Angeles, CA, USA). Codebook development will be led by 2 of the site principal investigators (H.A.F. and L.K.K.) who have extensive qualitative research training and experience. Open coding followed by focused coding will be conducted independently by at least 2 research team members per site until themes emerge. Results will be compared and disagreements will be resolved through discussion until at least 90% thematic agreement is reached. To ensure trustworthiness of the data, results will be shared via member checking with participants to ensure accuracy and avoid misinterpretation.⁵⁰ We will also use the Linguistic Inquiry and Word Count (LIWC 2015)⁵¹ program to objectively analyze caregiver interviews. LIWC 2015 is a text-analysis program developed on the premise that the words people use reflect their physical and mental health and can be used to learn about their beliefs, thinking patterns, emotions, social relationships, and personalities.^51,52 LIWC 2015 examines each word in a transcript against an internal dictionary of more than 6000 words to place the word into linguistic and psychological categories on the basis of 4 summary language variables: analytical thinking, clout, authenticity, and emotional tone. These variables will be used to compare each caregiver’s perceptions of their child, as reflected in their use of words, at the beginning and at the end of the study to complement traditional qualitative interview coding procedures.³³

Given the recent Food and Drug Administration clearance for the Explorer Mini and use of the new, fourth edition of the Bayley-4,⁴⁵ previous data are not available for a sample size calculation based on Aim 1. The power analysis to determine the number of participants (N) necessary to satisfy statistical assumptions for the study was conducted based on preliminary data from prior published research studies pertaining to Aim 2 and to the existing randomized control trial examining the developmental effects of powered mobility introduction.^11,13,53,54 Power was calculated from the results of the total time (minutes) a modified ride-on toy car was used between 2 groups: (1) families who received biweekly support via in-person researcher visits (mean [SD] = 1060 [783.8] minutes), and (2) families who received no support throughout a 3-month intervention period (mean = 171.4 [206.1] minutes). β was set at .80 and α at .05 to calculate N. Analysis indicated that a sample of 6 participants in each group (modified ride-on toy cars, Explorer Mini) would produce meaningful treatment differences. This power analysis is appropriate given our hypothesis that the Explorer Mini will be used more frequently, for a longer duration, and in more environments, than a modified ride-on car based on device design features. The above power analysis from previous data was based on between-group differences, whereas the current study will examine within-group differences of use patterns between devices, resulting in less variability and greater likelihood of observing differences, if differences exist.

Monitoring and Auditing

The study Data Safety Monitoring Plan outlines the oversight responsibilities for the responsible conduct of research and the collection and reporting processes for adverse events. A Data Safety Monitoring Board will be convened consisting of 3 independent individuals (1 from each research site) to review any adverse events or protocol deviations. All adverse events or protocol deviations will be reported to the University of Washington Human Subjects Division. The Data Safety Monitoring Plan also includes information about management of risk to participants, approaches to minimize risk, data management and security, discovery of incidental findings, and quality assurance procedures. No formal audit is scheduled for this clinical trial.

Ethics and Dissemination

Approval and Consent

This study has been approved by the Human Subjects Division at the University of Washington, which serves as the single institutional review board of record according to reliance agreements with both other sites. Only 1 caregiver is required to provide permission for their child and informed consent for themselves.

Confidentiality

Data from this study will use indirect identifiers of subject codes and pseudonyms. Any photos or videos included in dissemination will have consent documented for educational or scientific use. Following study conclusion, a summary of the data will be shared to clinicaltrials.gov.

Role of the Funding Source

This study is funded by the National Institutes of Child Health and Development, National Pediatric Rehabilitation Resource Center (C-PROGRESS; P2CHD101912), and the American Academy for Cerebral Palsy and Developmental Medicine. The sponsors of this work have had no role in the study design nor will they in data collection, data interpretation, or preparation of scientific manuscripts or presentations.

Discussion

Potential Impact and Significance

This study is significant because it aims to understand the effect of a powered mobility intervention on the developmental and participation outcomes of young children with cerebral palsy through provision of 2 emerging mobility technology options. This study embraces a potentially paradigm shifting approach of “on time mobility,” defined as an intentional powered mobility intervention (1) provided at an age when peers without disabilities start self-initiated mobility, and (2) targeted to provide exploration, mobility, and social engagement for children with cerebral palsy, or who are at risk of cerebral palsy, and who may experience mobility limitations. “On time mobility” suggests that powered mobility should be a valued intervention at developmentally appropriate stages, regardless of whether a child is delayed in mobility skills, not expected to attain specific mobility skills such as walking, or may not be efficient with other forms of mobility.^9,55

Strengths

This study design is a strength because previous powered mobility intervention research used study designs providing lower levels of evidence (ie, single-subject,^29,53,56,57 case reports,^32,58 case series,^30,59 or randomized group designs⁶⁰), although several previous powered mobility intervention studies also meet the National Institute of Health’s definition of a clinical trial. The current randomized clinical trial protocol aligns with an Oxford Center for Evidence-Based Medicine evidence level 2 study.⁶¹ Additionally, in the existing Jones et al randomized controlled trial,¹³ a total sample of 28 children participated (n = 14 in treatment and control groups), indicating that the current crossover study of 24 participants, all of whom will receive intervention, will be the largest of its kind.

Another strength of this protocol is the inclusion of automated device use tracking data as an objective outcome measure, in combination with parent diaries. Only 1 previous study to date has included automated device use tracking of modified ride-on toy cars.⁶² This study found no significant difference between automated tracking and parent diaries, but there was a general pattern of over- or underreporting device use depending on each family. Thus, this inquiry is significant in understanding how the concept of “dosage” may be applied to young children’s powered mobility use and family-specific needs in the future. In conjunction, the use of a mixed-methods approach will yield additional data about caregivers’ perceptions and satisfaction with each device. Finally, this protocol includes both caregiver-reported and clinician-reported measures, including assessment of specific powered mobility activity (eg, ALP), participation (eg, YC-PEM), and a full standardized developmental assessment (eg, Bayley-4) that spans multiple domains, all of which interact and may reciprocally influence each other as a result of powered mobility intervention. This combination of multiple stakeholder perspectives and measures across cognitive, communication, motor, socioemotional, adaptive, and participation domains has rarely been included in previous powered mobility literature, especially with children under the age of 3 years.

Weaknesses

Despite its potential, this protocol may be underpowered to evaluate our hypotheses, because it is difficult to estimate expected mean score changes on developmental assessments. Furthermore, the small sample will limit our ability to balance the intervention groups based on participant characteristics in our randomization approach. Our current study design does not include a control group or a period of no treatment; hence we are unable to control for maturation effects outside matching the two 8-week intervention periods. It will also be difficult to determine if a cause-and-effect relationship exists between a powered mobility intervention and observed changes in developmental outcomes. Although the outcome measures are comprehensive, the response burden for participants is high. Additionally, although all written study materials and researcher check-in materials indicate an expectation to incorporate the devices into each child’s daily mobility routine, the potential for low device usage remains. These combined weaknesses will be important to address in future studies with even larger sample sizes, and study designs that incorporate control groups or treatment washout periods once more is known about device use patterns and preferences.

Contributions to the Physical Therapy/Rehabilitation Profession

This protocol will result in one of the largest and most methodologically rigorous powered mobility intervention studies to date. A recent evidence synthesis of 89 powered mobility studies indicates that most powered mobility studies have low-quality evidence levels.³⁴ Although no conclusive evidence about the effectiveness of powered mobility could be made, the evidence suggested strong support for the positive impact of powered mobility on movement and mobility, and moderate support for participation, play, safety, and pain management. This study has the potential to empirically test many of these parameters. Additionally, this protocol will provide new understanding of use patterns and caregiver perceptions of 2 emerging powered mobility devices over a longer period of time (ie, 16 weeks) than previously reported. This is especially relevant because given the new release of the Explorer Mini, there has only been one previous feasibility trial of the device, in which children participated in 15-minute driving sessions.⁶³ Therefore, the current protocol will result in only the second study to include use of the Explorer Mini, and the device will be used by children over a much longer time period allowing for in-depth assessment and responses. Further, the inclusion in this protocol of a semistructured interview with caregivers will shed further light about the complex interplay between device, child, and environment. Finally, this study will contribute new and high-quality knowledge to the field and serve as the foundation for large-scale follow-up studies to address current protocol weaknesses.

Conclusion

This protocol offers a timely investigation of a newly released powered mobility device for infants and toddlers with cerebral palsy or at risk of cerebral palsy. It has the potential to provide an enhanced understanding of the developmental and participation outcomes of powered mobility use by young children, caregiver perceptions about the feasibility and appropriateness of such technologies, and elevate the evidence levels supporting use of powered mobility as a means of embracing the concept of on-time, multimodal mobility intervention for young children with disabilities.

Author Contributions

Concept/idea/research design: H.A. Feldner, S.W Logan, L.K Kenyon

Writing: H.A. Feldner, S.W Logan, L.K Kenyon

Data collection: S.W Logan

Data analysis: S.W. Logan

Project management: H.A. Feldner, S.W Logan

Fund procurement: H.A. Feldner, S.W Logan, L.K Kenyon

Providing participants: H.A. Feldner, S.W Logan

Providing facilities/equipment: H.A. Feldner, S.W Logan

Consultation (including review of manuscript before submitting): L.K. Kenyon

Ethics Approval

This study has been approved by the Human Subjects Division at the University of Washington, which serves as the single institutional review board of record according to reliance agreements with both other sites. Only 1 caregiver is required to provide permission for their child and informed consent for themselves.

Funding

This study is being funded by the American Academy for Cerebral Palsy and Developmental Medicine and the National Pediatric Rehabilitation Resource Center (C-PROGRESS) through the National Institute of Child Health and Human Development (NICHD) (P2CHD101912). In addition, Permobil, the manufacturer of the Explorer Mini, loaned 6 of the 12 Explorer Minis needed to complete the study. The funding agencies and equipment manufacturer have no role in the design of the study, data analysis, interpretation, or preparation of scientific manuscripts or presentations.

Clinical Trial Registration

This study has been registered with the US National Library of Medicine Clinical Trial Registry under the National Clinical Trial (NCT) identified number NCT04684576 (Protocol Version 1) on December 24, 2020.

Disclosures

The authors completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest.