INTRODUCTION
Static neurological injuries can affect ankle mobility secondary to impairments in range of motion (ROM), strength, muscle tone, and selective motor control.1 Children with cerebral palsy (CP), a common form of static neurological injury, typically present with greater weakness in distal musculature, difficulty with concentric contractions, and difficulty with quick velocity movements.2,3 These impairments lead to altered gait mechanics and impaired balance.4 Ross and Engsberg5 concluded that lower-limb strength was highly related to gait performance in children with spastic diplegia.
For children with lower-limb impairments secondary to a neurological injury, physical therapy (PT) is an addition to their routine throughout their lifespan.6 PT interventions include therapeutic exercise for strengthening and balance, serial casting for increasing ROM, and the use of orthotic devices to promote lower-limb stability and improve functional mobility.4 Therapy access and scheduling are hurdles to participation in outpatient PT, which makes participation in a home exercise program (HEP) essential for meaningful gains. Although it can be challenging to implement, the addition of 1 hour per week of exercise at home can measurably increase the intensity of therapy.7 Adherence to HEPs has been qualitatively studied in pediatrics, and common themes have emerged.8,9 Families acknowledge factors that impair their ability to adhere to an HEP such as the need for equipment to modify exercises, autonomy, motivation, effort, and time management.10 Adherence is multifactorial including environmental limitations,10 personal limitations,10 characteristics of exercises,11 and physical therapists' teaching styles.11
PedBotHome (Figures 1A and 1B) is a robotic platform with a video gaming interface designed to allow children to complete ankle exercises at home in a fun engaging way. It is modeled after PedBotLab, a more robust and expensive device designed for the clinic setting, currently undergoing efficacy studies.12 The home-based platform addresses HEP adherence limitations noted in the literature such as the ability to use specialized equipment in the home, remote monitoring by a health care professional, and incorporation of favored hobbies, such as video gaming.8,9 Active video games have been shown to be a valuable rehabilitation tool to improve gross motor skills.13 Platform-based robotic ankle rehabilitation has reduced motor impairment and enhanced functional motor outcomes in those with ankle impairments.14 Most ankle robots are designed for adults to improve cooperation and treatment intensity.14 Previous platforms were designed with 1 or 2 degrees of freedom (DOF), limiting the functional training available as the ankle moves in 3 planes of motion.15–19 Zhang et al14 concluded that to be successful, platform-based ankle robots need to provide effective movement, active assistance, and work in multiple planes of motion to mimic the true ankle joint. However, no current system available has 3 DOF combined with assist-and-resist modes.20 PedBotHome is unique in that the device has 3 DOF, mimicking the natural movement of the ankle joint, and can provide motorized assistance or resistance in all directions of movement. A review by Alvarez-Perez et al21 states that a disadvantage of platform-based robots is the need for a clinician to operate the device and their exclusive presence in a clinic. PedBotHome addresses this by allowing play in the home, providing more opportunities for use.
Fig. 1.: PedBotHome hardware and software. A photograph of the PedBotHome foot platform hardware (A). An illustration of the PedBotHome setup in a participant's home (B). A flowchart of the PedBotHome software algorithm for progressive play (C). A screen-capture of the PedBotHome video game interface, including on-screen readouts (D). CP indicates
cerebral palsy; RoM, range of motion. This figure is available in color online (
www.pedpt.com).
This pilot study was designed to assess the feasibility of PedBotHome to withstand frequent use and monitoring use while in the home for 28 days. Secondary outcomes include assessment of ankle ROM, spasticity, and strength. PedBotHome's pilot study has 2 hypotheses: (1) children will participate in at least 20 of 28 days (or ∼5 days per week, adherence rate of 72%) of home exercise with a novel device in the home and (2) use of PedBotHome will improve ankle strength, increase ROM, and/or reduce plantar flexor spasticity.
METHODS
PedBotHome is a robotic device with a mobile foot platform with multiple sizes for growth, a smartphone, a desktop computer, an adaptive chair, and associated software including a novel video game and a game progression algorithm (Figures 1A-D). The footprint of the device is 2 × 4 ft. The system is placed in an area of the home that is easily accessible and has reliable Wi-Fi. PedBotHome has 3 DOF and can be used in active mode (the participant is active, and the motors are inactive), active assisted mode (the participant is active, and the motors assist movement toward a target), or resisted mode (participant is active, and the motors resist movement toward the target). The angular movement of the robotic footplate is tracked by a smartphone attached underneath that communicates with the desktop computer via the participant's home Wi-Fi. Multiple motors control pitch (plantar flexion and dorsiflexion), yaw (abduction and adduction of the forefoot), and roll (inversion and eversion) and provide assistance and resistance as needed. For safety, the device has an accessible emergency stop button.
The child's foot, which is strapped into a casting shoe mounted on the footplate, acts as an input device to pilot an airplane through a series of hoops in the video game (Figure 1D). The hoops present in a pattern to promote movement in pitch, yaw, roll, or any combination. The participant begins playing at his or her baseline ROM within 1 or multiple planes of motion as established by the physical therapist. Three sets of exercises are performed for 10 minutes each via gameplay every session. A set is defined as play in a specified singular plane or combined planes of motion. Daily gameplay is progressed automatically by an algorithm in the software (Figure 1C). The participant advances to working against resistance and then within a larger ROM with visual targets spaced further apart. If there is difficulty with progression, the system moves into assistance mode. A report is generated weekly by the software system, which allows the team to analyze trends in active ROM (AROM) and successful gameplay. The team reviews the report weekly and chooses to modify the exercise sets.
PedBotHome was approved by the local Institutional Review Board. Informed consent was obtained from participants and guardians before starting the trial. Participants were recruited through outpatient clinics at a large freestanding pediatric hospital. Most had previously completed the PedBotLab study. Inclusion criteria for the pilot study consisted of children between the ages of 4 and 18 years with a static neurological injury who had the ability to walk a community distance with or without assistive device (Gross Motor Function Classification System I-III for those with CP), with an adult guardian capable of giving consent. Participants were excluded if they were unable to follow single-step commands, had plantar flexion contractures greater than 10° from neutral, were unable to achieve subtalar neutral with passive ROM (PROM), had previous pathological fractures, had central nervous system surgery or orthopedic surgery on the affected limb in the previous 6 months, or received botulinum toxin injections during the trial or within 1 month prior to the study.
Installation of PedBotHome was completed by the team's mechanical engineer, software engineer, and physical therapist in the participant's home and was completed on average in 2 hours. The mechanical engineer completed physical setup of the system, while the software engineer connected the system to the home Wi-Fi network and completed a software test run. The physical therapist assisted the mechanical engineer in customizing the device for optimal patient alignment, safety, and comfort and educated users on device use and navigation of the software. The participant and family were given a user manual on how to use and troubleshoot the device. Contact information for the troubleshooting team was given to all families, and on-site and remote assistance was available as needed. Participants were informed that the goal would be to use the device as many days as possible over 28 days. Successful adherence was defined as using the device 20 of 28 days or an adherence rate of approximately 72%.
Using a pretest/posttest design, participants completed ankle ROM, strength, and plantar flexor spasticity assessments. A pediatric physical therapist with 15 years of experience and advanced training in orthopedic assessments completed all pre- and posttest measurements to avoid interrater differences. No analysis or review of individual data was performed until completion of the final assessment. All measurements were performed on both limbs to assess progression of symmetry.
The intraclass correlation coefficient (ICC) was used to measure intrarater reliability for strength assessment via dynamometry. Reliability analyses were performed on data taken from 6 participants. For each parameter, 3 measurements were taken, and a 2-way random-effects model based on single ratings and absolute agreement was used to assess the intrarater reliability. Mean estimation along with 95% confidence intervals are reported for each ICC. ICC values (Table 1), were good or excellent for all muscle groups for strength.22 Intrarater reliability values for ROM using goniometry and for the Modified Tardieu Scale (MTS) were not determined prior to this study.
TABLE 1 -
Intrarater Reliability for Strength Assessments
Strength Assessments |
Intrarater Reliability ICC (95% CI) |
Right Pretest |
Left Pretest |
Right Pretest |
Left Pretest |
Ankle dorsiflexion with knee flexion |
0.68a (0.23-0.94) |
0.90b (0.66-0.98) |
0.65a (0.14-0.93) |
0.50c (0.00-0.89) |
Ankle dorsiflexion with knee extension |
0.79b (0.43-0.96) |
0.79b (0.25-0.97) |
0.93b (0.75-0.99) |
0.84b (0.51-0.97) |
Ankle plantar flexion |
0.95b (0.81-0.99) |
0.89b (0.61-0.98) |
0.75b (0.34-0.96) |
0.93b (0.75-0.99) |
Ankle inversion |
0.73a (0.31-0.95) |
0.95b (0.82-0.999) |
0.90b (0.67-0.98) |
0.93b (0.75-0.99) |
Ankle eversion |
0.75b (0.32-0.96) |
0.98b (0.91-1.00) |
0.67a (0.22-0.94) |
0.93b (0.73-0.99) |
Abbreviations: CI, confidence interval; ICC, intraclass correlation coefficient.
All ankle ROM was measured with the same standard goniometer.23 Goniometry is considered a valid and reliable clinical tool for assessing ankle ROM.24 Dorsiflexion was assessed with the knee flexed and extended, plantar flexion with the knee flexed, and inversion and eversion were measured with the knee extended. AROM of the ankle was completed in gravity-eliminated positions via the use of a goniometer: side-lying position for ankle dorsiflexion with knee flexed and extended, side-lying position for ankle plantar flexion with the knee flexed, and prone position for inversion and eversion with the knee extended.25 PROM was measured in prone position. Plantar flexor spasticity was assessed using the MTS where R1, first resistance, is defined as the onset of resistance to passive stretch signaled by a catch-and-release or onset of clonus during a fast-paced passive stretch into ankle dorsiflexion.26R2, second resistance, is defined as the end range passive dorsiflexion measurement with full length of the plantar flexors following a slow stretch. R1 and R2 were assessed via goniometric measurements. The MTS has been shown to have acceptable reliability when used among children with CP.27
For dorsiflexion and plantar flexion strength assessments, the MicroFET 2 hand-held dynamometer was used to assess muscle force production using kilograms of force (kgF), following the protocol from Andrews et al.28 Hand-held dynamometry is a reliable tool to measure change in lower-limb muscle strength in children with CP.29 The participants were instructed to perform a maximum isometric contraction. Strength was measured 3 times for each muscle group, and the best score was used. If there was a perceived error in measurement due to poor effort, attention, or understanding by the participant, the trial was repeated. The same hand-held dynamometer was used to evaluate all participants at both assessments.
Participants were asked to report the amount of time played and any hardware or software concerns in a daily log. The PedBotHome team remotely monitored use via Chrome Remote Desktop and used these data to corroborate participant logs and modify prescribed exercises. Child and parent interaction with the system was observed during the final week of each trial. Between participant trials, software and hardware were adjusted or repaired on the basis of feedback provided from the previous participant.
Following completion of all 8 trials, data from pre- and posttest assessments were analyzed for trends across the following 4 variables: AROM, PROM, plantar flexor spasticity, and strength. Two-tailed paired Student t tests were used to assess statistically significant differences between pre- and posttest assessment data. Because of the large number of t tests for each variable, a multiple-test Bonferroni post hoc correction was applied to control for the possibility of a type 1 error. The calculated Bonferroni-corrected new critical value was 0.0125 (0.05/4) for those motions where 4 separate t tests were conducted (ankle dorsiflexion with knee flexion and ankle dorsiflexion with knee extension). For the remainder of the 3 motions (ankle plantar flexion, ankle inversion, and ankle eversion), 3 separate t tests were conducted for each and the calculated Bonferroni-corrected new critical value was 0.0167 (0.05/3) for them. Data from participant interviews were organized into 21 factors that mapped into 3 categories of experience (Personal Factors, Fit of Exercise Program in the Home Environment, and Therapist Support) based on synthesizing the 2 theories of HEP adherence, as described in Schladen et al.30
RESULTS
Eight participants enrolled in and completed the feasibility study with the device in their home for at least 28 days. No participant sustained injury related to the use of PedBotHome; however, periodic discomfort was reported. A summary of participant usage is given in Table 2. Half exceeded the goal of 20 sessions in 28 days. All the participants who did not complete 20 sessions experienced technical difficulties, resulting in gaps of use until a team engineer could perform a home visit for system maintenance. The median number of sessions played was 20 over a 28-day use period or an adherence rate of 72%.
TABLE 2 -
Description of Participants and Adherence Rate
Participant |
Age, y |
Sex |
Clinical Diagnosis |
GMFCS/Functional Level |
Adherence Rate |
Days of Use |
Software Issues |
Hardware Issues |
Resolution of Issues |
1 |
14 |
F |
Spastic hemiparetic cerebral palsy |
2 |
89% |
25/28 |
No |
Yes |
Yes |
2 |
14 |
F |
Spastic hemiparetic cerebral palsy |
1 |
67%a |
19/35 |
Yes |
No |
Yes |
3 |
16 |
M |
Spastic hemiparetic cerebral palsy |
2 |
96% |
27/28 |
No |
No |
NA |
4 |
16 |
F |
Spastic diplegic cerebral palsy |
2 |
86% |
24/28 |
No |
No |
NA |
5 |
11 |
F |
Spastic hemiparetic cerebral palsy |
2 |
18% |
5/28 |
Yes |
No |
Yes |
6 |
9 |
F |
Spastic hemiparetic cerebral palsy |
1 |
75% |
21/28 |
Yes |
No |
Yes |
7 |
11 |
F |
Spastic hemiparesis s/p brain tumor |
NAb |
61% |
17/28 |
No |
Yes |
Yes |
8 |
13 |
F |
Spastic hemiparetic cerebral palsy |
2 |
25% |
7/28 |
No |
Yes |
Noc |
Abbreviations: GMFCS, Gross Motor Function Classification System; NA, not available.
aAdherence calculated with 28 days of usage—PedBotHome was unusable for 7 days.
bIndependent ambulator without assistive device.
cFamily did not return team's calls to attempt to fix device.
Individual outcome measure results are graphed in Figures 2A-D. Seven of the 8 participants had positive changes in measurements across all outcome measures. The average of participant results and their statistical significance are given in Table 3. Six of 8 participants had statistically significant improvements in plantar flexor spasticity with the knee extended (P = .0050). Strength improved for all participants in at least 3 of 5 measurements, more consistently in ankle dorsiflexion, plantar flexion, and eversion. Statistically significant improvements were seen in ankle dorsiflexion strength with the knee flexed (P = .0003). Most participants had positive changes in PROM and AROM across 4 of 5 measurements. Improvement in eversion AROM was statistically significant (P = .0124). Table 4 categorizes positive and negative feedback for each adherence factor identified by Lillo-Navarro et al11 and Taylor et al.10 Parent and participant responses are included. Positive and negative feedback was received.
Fig. 2.: Improvements in patient performance after using PedBotHome. Participants experienced improvements in passive (A) and active (C) range of motion for ankle dorsiflexion while the knee was extended. Participants also had reduced plantar flexor spasticity as noted by an increase in
R 1 (B). They also exerted significantly more force as measured by ankle dorsiflexion while the knee was extended (D). DF indicates dorsiflexion; ROM, range of motion; PF, plantar flexor; MTS, Modified Tardieu Scale; N/A, not applicable; NT, not tested. This figure is available in color online (
www.pedpt.com).
TABLE 3 -
Average Participant Outcomes
|
Average Pretest PROM (Degrees) |
Average Posttest PROM (Degrees) |
Average PROM Change ± SD (Degrees) |
Average Pretest R
1 (MTS) (Degrees) |
Average Posttest R
1 (MTS) (Degrees) |
Average R
1 Change ± SD (Degrees) |
Average Pretest AROM (Degrees) |
Average Posttest AROM (Degrees) |
Average AROM Change ± SD (Degrees) |
Average Pretest Strength (kgF) |
Ankle DF with knee flexion |
15 |
20 |
5a ± 3 |
−3.3 |
3.7 |
7 ± 7.1 |
−1.4 |
6.3 |
7.7 ± 11.9 |
5.2 |
Ankle DF with knee extension |
7.4 |
13.5 |
6.1 ± 6.1 |
−11.4 |
0.3 |
11.7a ± 7.2 |
−7.5 |
−3.3 |
4.2 ± 6.3 |
4.4 |
Ankle plantar flexion |
55.3 |
58.8 |
3.5 ± 6.2 |
NA |
NA |
NA |
41.9 |
44.3 |
2.4 ± 9.5 |
5.7 |
Ankle inversion |
23.3 |
27.1 |
3.8 ± 4.3 |
NA |
NA |
NA |
15.3 |
20.3 |
5b ± 4.2 |
4.1 |
Ankle eversion |
10.9 |
13.4 |
2.5 ± 3.3 |
NA |
NA |
NA |
6 |
10.4 |
4.4b ± 3.7 |
3.8 |
Abbreviations: AROM, active range of motion; DF, dorsiflexion; MTS, Modified Tardieu Scale; NA, not available; PROM, passive range of motion; SD, standard deviation.
aP < .0125 (Bonferroni-corrected P value threshold for 4 t tests).
bP < .0167 (Bonferroni-corrected P value threshold for 3 t tests).
TABLE 4 -
Fit of Exercise Program Based on Environmental and Participant Factors
Adherence Factor |
Positive Feedback |
Negative Feedback |
Family support or disruption10,11 |
|
|
Exercise equipment10 |
|
|
Exercise logbook10 |
-
Convenient
-
Clear and concise
|
|
Program factors (time, duration)10 |
|
|
What the exercise is/therapist factors10 |
|
|
Perceived effectiveness11 |
|
|
Fun doing exercise11 |
|
|
Comfort during exercise11 |
|
|
Perceived complexity of doing exercise11 |
|
|
Autonomy10 |
|
|
Motivation10 |
|
|
Effort10 |
|
|
Health10 |
|
|
Time management10 |
-
Efficient way to manage their own time better
-
Decreases time traveling to the clinic
-
More potential time in therapy in the home system
|
|
DISCUSSION
This pilot study of PedBotHome demonstrates that the device is a safe and feasible option for these participants to improve ankle mobility and promote performance of a prescribed HEP in their home. However, limitations in the software and hardware (Table 2) led to gaps in play likely interrupting gains in ROM and strength, as some participants went multiple days unable to play secondary to pending repairs. Depending on whether the issue was hardware or software, repairs were completed in person or remotely. This explains the variance in the number of days that participant 2 had the device in the home. Participant 7 had many a day that the device was “out of service,” but no additional days were added to the trial as the gaps in time were not sequential. Participant 8 had a major barrier with hardware and software connection that affected gameplay, with at least 6 days of the device being out of service. Participant 8's family did not return communication with the study team, and the device was never serviced. Primary reliance on the family to contact the team for hardware or software repairs is a limitation. Participant logs provide valuable insight but are not communicated in real time and are not always reliable. Future iterations will have capabilities to track days of use and allow for better remote monitoring and communication through a participant portal. Other limitations of the study included heterogeneity of the study population, small sample size, prior exposure to robotic intervention, and lack of long-term follow-up assessments to gauge maintenance of results.
An in-depth publication focusing solely on participant feedback from the interviews has been previously published.30 The interview feedback provides valuable information on barriers to adherence when using PedBotHome and is useful to facilitate a redesign. According to Lillo-Navarro et al,11 improved adherence and completion of HEP relied on pleasure of the specific task and low risk of pain. Feedback from participants highlights that part of the footplate and box-like setup of the device caused discomfort during play, negatively impacting their experience. Multiple participants reported that while there was initial novelty of the video game, it eventually became boring and repetitive. They also reported some frustration over how long some of the exercises lasted. Future software will include new games and more autonomy in gameplay for the participants. Taylor et al10 identify that one of the biggest barriers to successful adherence to exercise programs is the environmental factor of assistance, both physical and verbal. From a physical assistance perspective, most participants and their parents reported that a positive aspect of the system was that parents did not need to help the child use the device. The participant with the lowest compliance, however, required additional support for setup and had scheduling difficulties with parental availability. Social engagement is an area that is not addressed well in this current version of PedBotHome. A handful of participants who had completed the PedBotLab study benefited from the social nature and direct real-time feedback and encouragement from the in-person physical therapist. Support from a physical therapist has been previously identified as an important category to adherence. Future modifications will incorporate ways for the therapist to communicate with the participant through the system to improve engagement.
The combination of PedBotHome's software, gaming algorithm, assistance and resistance modes, and remote monitoring by physical therapists creatively challenges the child while avoiding excessive difficulty. Experienced rehabilitation therapists advocate for active assisted exercise or assistance as needed as the optimal way to challenge a patient.31 Furthermore, it has been suggested that children respond well when programs are creative and challenging, without being too difficult.32 PedBotHome allows for mass practice of ankle movement in multiple planes with simultaneous visual feedback and mitigates some of the identified barriers to successful HEP completion. While participants had improvements in strength and/or ROM, the literature poorly defines the clinical significance of change in these outcome measures in the lower limb. However, changes in AROM may reflect improved selective motor control, as many participants were unable to move their ankle in the frontal plane volitionally at initial evaluation but were able to intrinsically motor plan the movement after PedBotHome use. While the average change in AROM does not exceed the minimal detectable change (MDC) and standard error of measure (SEM) for dorsiflexion, some individual changes in ankle dorsiflexion AROM exceed the MDC.33 In future studies, intrarater reliability for ROM and any additional outcome measures will be established. Previous studies that compare the use of virtual reality (VR) with conventional HEPs conclude children generate greater range of dorsiflexion, better control of active ankle dorsiflexion, and report greater interest in exercise when delivered through a VR system.34 This is consistent with the results seen in this trial. Participants had improvements in strength, ROM, and spasticity, which provide the foundation for improving gait and balance. For future efficacy trials, measurements of gait and function will additionally help determine significant clinical and functional changes.
As previously mentioned, a clinic-based design with more robust features, PedBotLab, inspired this first version of a home device.35 PedBotLab costs $12 500 to fabricate. PedBotHome has a smaller footprint and lower cost of production ($2000) with most components 3D printed. Despite the significant cost reduction, this is still a prohibitive cost for families. In addition, the lower-cost 3D printed components became a significant limitation of the device, as they frequently broke due to the force of the motors, leading to a need for in-person service and fewer days of play. Furthermore, the current box-like design led to discomfort and decreased ROM capability of the device. Therefore, PedBotHome version 2 is being designed with more sturdy components and a more ergonomic design, at a slightly higher production cost. One of the higher cost components was the adjustable chair. Although this does allow for PedBotHome to be used as the child grows, potentially limiting investments in other therapeutic devices and providing cost savings over time. A higher cost will make PedBotHome less accessible for families in the future; however, if proven efficacious and approved as a medical device, it has the potential to be funded by some insurances.
With the COVID-19 pandemic, further enrollment in this study was paused secondary to institutional safety protocols. However, this pandemic and its effects on health care have had the crucial need for remote monitoring and progression of exercise to provide safe and effective PT. Tele-rehabilitation is progressing to make remote services widely available. PedBotHome has potential to impact children with static neurological injuries to promote consistency with exercise to maintain or improve mobility within the safety of a child's home. The PedBotHome system also has the potential to be compatible with commercially available video games. In future designs, participants will play with or against each other, addressing social and participation restrictions often experienced by children with neurological impairments and improving their overall quality of life. This pilot study creates a paradigm for future innovative technologies in the rehabilitative robotics realm and provides a pathway for robotics to be integrated into pediatrics.
ACKNOWLEDGMENTS
The authors thank Satvika Garg, PhD, OTR/L, and William Coley, PhD, for their assistance with editing and formatting the manuscript. The authors also thank their wonderful participants who enrolled in this study.
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