All participants were able to attain at least 3 consecutive days of 9 hours daily wear of DR-AFOs. Duration of wear over the 2-week intervention phase ranged from 2 to 11 hours per day (mean = 5.0) for DR-AFOs and 5 to 10 hours per day (mean = 8.0) for the placebo. Individual intervention time means are reported in Table 1. By parent and participant report, negative factors related to DR-AFO wear included more difficulty rising from the floor and climbing stairs and hills and minor skin itching/discomfort. Negative factors related to placebo wear were limited to mild itching and sweating of feet.
Timed Tests. Individual performance data for timed test outcomes are presented in Table 2. With DR-AFO use, median time taken to walk 10 m increased (median increase = 0.8 s [range 0.7-3.4]), whereas median 6MWD decreased (median decrease = −25.0 m [range −44.0 to 18.8]). Median time to rise from the floor was also increased with DR-AFO wear (median increase = 2.7 s [range −0.8 to 4.4]), as was time to climb 4 stairs (median increase = 2.4 s [range 2.2-6.5]). Although these findings are consistent in suggesting worsening walking speed, endurance, rise from the floor time, and stair climb time with DR-AFO use, it is worth noting that high variability in performance was evident for timed tests, both within a single participant across multiple baseline (no intervention) tests and across different participants in terms of the magnitude and/or direction of DR-AFO effects on performance. All 3 boys demonstrated slowed 10-m walk and stair climb times with the DR-AFO intervention, and 2 of 3 showed a decrease in performance in 6MWD and rise from the floor time. However, 1 participant (#3) showed nominally improved performance in 6MWD and rise from the floor time in the setting of high baseline variability. Quantitative evaluation of stability in baseline performance showed that 10-m walk time was the least variable (median baseline difference = 0.3 s [range 0.0-1.0]). Median baseline differences for 6MWD, rise from floor time, and 4 stair climb time were 56.3 m (range 18.8-106.2), 1.7 s (range 0.3-2.2), and 2.8 s (range 0.2-6.4), respectively.
Fall Frequency. All participants reported experiencing at least 1 fall during the 1-week washout (no intervention) phase (median = 2 [range 2-4]) and during the 2-week DR-AFO phase (median = 6 [range 1-12]). Consistent with findings of gait characteristics that could suggest a more halting and unbalanced gait pattern during DR-AFO use, 2 of 3 participants also reported a higher frequency of falls during 2 weeks of DR-AFO use, compared with during 2 weeks of placebo use. Individual fall data are summarized in Table 1.
In this pilot study, a small sample of boys with DMD walked more slowly over 10 m, covered less distance in a 6-Minute Walk Test, took longer to rise from the floor and climb stairs, adopted a widened base of support when ambulating, and fell more frequently when wearing DR-AFOs. The slowed speeds when rising from the floor and stair climbing are not surprising. Typical motor patterns for rising from the floor and stair climbing can be impeded by AFO wear that limits talocrural motion near neutral because additional ankle dorsiflexion and plantar flexion are needed to move efficiently with these functional activities. Dynamic response AFOs, which do limit talocrural motion, together with DMD-related muscle weakness, may have conspired to make these functional activities more challenging. Duchenne muscular dystrophy natural history studies confirm that, even without AFOs, rising from the floor and stair climbing become increasingly difficult for boys with DMD, particularly after the age of 7 years.6,15 In this study, the decrease in 4 stair climb speed of all 3 boys exceeded a previously identified minimal clinically important difference (MCID) of 2.1 to 2.2 s,15 suggesting that this loss of speed indeed represented a meaningful decrement in performance.
Findings of a widened base of support and more frequent falls with DR-AFO wear corroborate the prevailing belief that bracing does not improve walking stability in boys with DMD and may even have negative effects on already impaired balance, an idea that has been more theoretically than empirically based.10,23 Given underlying osteopenia and increased risk of femoral and lumbar fractures24 that can bring an end to functional ambulation, fall prevention is an important clinical goal for boys with DMD. More frequent falls with AFO wear implies an increased risk for fall-related fractures, particularly for boys on long-term glucocorticoid therapy.
Mean duration of wear for all 3 participants was higher during the placebo condition than that of DR-AFO condition. Less wear of the DR-AFO could indicate lower tolerance for this intervention, suggesting that the placebo was easier and more comfortable to use. On the contrary, any beneficial effects of treatment using DR-AFOs may not have had the same opportunity to exert themselves because the DR-AFOs were not actually used for the same amount of time as the placebo device. It would be interesting to know, for example, if the reported fall episodes (which were more frequent with DR-AFO use) occurred when the participants were actually wearing the AFOs or during periods when they were not worn. This information was solicited in parental report logs, but was not reported in a clear enough fashion to allow analysis.
The aim of this pilot study was, in part, to assess the feasibility of a future randomized controlled trial of AFO effects on walking in boys with DMD. Given the small sample size of this pilot, statistical comparison of DR-AFO and placebo conditions was not indicated. A comparison of data between the 2 intervention conditions showed high-performance variability, even under baseline (no intervention) conditions, suggesting the need for large sample sizes in any future trials. Potential contributors to day-to-day performance variability include glucocorticoid dosing schedule,25 fatigue,26 and variable motivation/effort.27 Glucocorticoids (eg, prednisone or deflazacort) constitute the only pharmacological therapy with proven potential to decrease (temporarily) the expected decline in motor function in boys with DMD.28,29 Although daily dosing is common, intermittent dosing (eg, 10 days on/10 or 20 days off) has also been studied and recommended, with the aim of achieving similar benefits to muscle and function as with daily dosing, alongside tempered negative side effects including weight gain, stunted growth, bone loss, irritability, and hyperactivity.3,30–32 A statistical comparison of motor performance between corticosteroid “on” and “off” times with intermittent dosing regimens could not be found, but published data suggest that performance on day 10 of corticosteroid dosing is consistently better than at the end of an “off” phase.25 Therefore, intermittent dosing poses an additional challenge to DMD study design and will need to be accounted for in future trials. In addition, future PT intervention studies should consider differences in patterns of change over time between boys younger than 7 years (in whom improvements in timed test performance and 6MWD may occur) and boys 7 years and older (in whom improved performance suggests robust intervention effects)15 and recruit participants accordingly.
The findings from this pilot study do not suggest clear benefits with DR-AFO use for household or community ambulation in boys with DMD. Although individual responses vary, DR-AFO wear may slow walking speed over both short and long distances and may be associated with instability and falls for some boys. Additional studies of orthotic use should include a larger sample, collect more detailed fall data, and take into account the potential effect of corticosteroid dosing schedule.
Dynamic response AFOs were provided by Allard, USA. We thank orthotist Gordon Craig, CO, BOPCO, of New England Orthotic & Prosthetic Systems (NEOPS) for consultation, Brian Tseng, MD, PhD, for an introduction to the study of Duchenne muscular dystrophy and the boys and their families for participation in this study.
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