Generation of percentile curves for strength and functional abilities for boys with Duchenne muscular dystrophy

Abstract

Introduction/Aims Considering the heterogeneity of the clinical manifestations of Duchenne muscular dystrophy (DMD), it is important to describe their various clinical profiles. Thus, in this study we aimed to develop percentile curves for DMD using a battery of measures to define the patterns of functional abilities, timed tests, muscle strength, and range of motion (ROM). Methods This retrospective data analysis was based on the records of patients with DMD using the Motor Function Measure (MFM) scale, isometric muscle strength (IS), dorsiflexion ROM, 10‐meter walk test (10 MWT), and 6‐minute walk test (6 MWT). Percentile curves (25th, 50th, and 75th percentiles) with MFM, IS, ROM, 10 MWT, and 6 MWT on the y axis and patient age on the x axis were constructed using the generalized additive model for location, scale, and shape, with Box‐Cox power exponential distribution. Results There were records of 329 assessments of patients between 4 and 18 years of age. The MFM percentiles showed a gradual reduction in all dimensions. Muscle strength and ROM percentiles showed that the knee extensors were the most affected from 4 years of age, and dorsiflexion ROM negative values were noted from the age of 8 years. The 10 MWT showed a gradual increase in performance time with age. For the 6 MWT, the distance curve remained stable until 8 years, with a subsequent progressive decline. Discussion In this study we generated percentile curves that can help health professionals and caregivers follow the trajectory of disease progression in DMD patients.

Longitudinal trajectories of muscle impairments in growing boys with Duchenne muscular dystrophy

“…Larger deficits were observed for dorsiflexion ROM with knee extended than with knee flexed, suggesting that the gastrocnemius is more affected than the soleus in the boys with DMD. Previous literature found that the absolute dorsiflexion ROM declined linearly from early ages onwards [32,37], which is in contrast with the non-linear piecewise trajectories in the current results. Although the observed decline rates in absolute dorsiflexion ROM were steeper than the previously reported longitudinal results of Kiefer et al [37], the boys with DMD in the current study lost the ability to achieve neutral ankle angles at approximately 12 years of age with knee extended and at approximately 14 years of age with knee flexed, which was at an older age than reported by Leon et al [32].…”

“…The variations in decline rate among muscle groups can be partially attributed to the timing of the breakpoint and the existing initial weakness. Previous literature reported a similar sequence of decline rate among muscle groups [32,33]. However, the longitudinal trajectories are not entirely equivalent, but due to methodological discrepancies among the studies, comparing the results proves challenging.…”

“…The ankle dorsiflexion ROM gradually declined with age. Negative ROM values (i.e., ROM deficit to reach the neutral ankle angle of 90°) were observed from 8 years onwards with knee extended and from 9 years onwards with knee flexed, highlighting a pathological shortening in ankle plantar flexors [32]. However, previous studies did not account for the typical reduction in ROM observed in TD children aged 2 to 17 years [38–40].…”

“…A previous longitudinal analysis indicated that absolute knee extension/flexion strength increased until the age of 7.5 years, while after the age of 7.5 years strength declined, with even a more pronounced decline after 9 years of age [31]. Recently, Leon et al [32] generated percentile curves of muscle strength for boys with DMD aged 4 to 18 years based on an extended longitudinal dataset consisting of 230 assessments in 73 boys. Knee extension strength exhibited the most pronounced decline, followed by hip flexion strength, and then knee flexion strength.…”

Quantifying Variability in Motor Function in Duchenne Muscular Dystrophy: UK Centiles for the NorthStar Ambulatory Assessment, 10 m Walk Run Velocity and Rise from Floor Velocity in GC Treated Boys

“…More recently, these methods have been developed for other motor function outcomes including the Motor Function Measure (MFM) for DMD [14] and several outcome measures for cerebral palsy [15][16][17]. Centiles have also recently been presented for the MFMF, 10MWR time and other strength measures in a small cohort (73 patients) in Brazil, however, the low sample size, discretised age and lack of imputation of scores leads to biased trend over time (such as linearly increasing 10MWR times with age) [18]. Centiles for age help to describe the relative heterogeneity.…”