Key result
In children with spinal muscular atrophy, the overall prevalence of hip displacement was 75.6%, with SMA type II (P=0.04) and clinically relevant scoliosis (P=0.04) as independent risk factors.
Why the study?
Genetic severity and gross motor function level had not been investigated as risk factors for hip displacement in spinal muscular atrophy, and the effects of disease-modifying agents on hip displacement prevention were unknown.
Cohort (n=82)
Hip displacement is highly prevalent in children with SMA, with SMA type II and clinically relevant scoliosis serving as independent risk factors that can guide surveillance programs.
PURPOSE: Hip displacement (HD) is common in spinal muscular atrophy (SMA), but neither genetic severity nor gross motor function level have been investigated as risk factors. Although disease-modifying agents (DMA) have improved function and overall health, their effects on the prevention of HD are unknown. The purpose of this study was to determine risk factors for HD development in SMA. METHODS: Retrospective cohort. Children with SMA presenting between January 2005 and August 2021, at least 1 hip radiograph, and a minimum 2-year follow-up were included. The primary outcome measure was the prevalence of HD (migration percentage ≥40%). Secondary outcomes included SMA type (I/II/III), survival motor neuron 2 copy number, Hammersmith Functional Motor Scale (HFMS, out of 66), ambulatory status (Functional Mobility Scale at 50 m), clinically relevant scoliosis (>40 degrees and/or surgery), and DMA treatment (>1-year duration, nusinersen/risdiplam/onasemnogene abeparvovec) as risk factors. Univariate and multivariate logistic regression analyses were performed. RESULTS: Eighty-two patients (52% female) with SMA type I (n=32, 39%), II (n=36, 44%), and III (n=14, 17%) met the inclusion criteria, with a final follow-up of 4.5 (SD: 2.7) years. Age at first hip radiograph was 3.4 (SD: 2.9) years. The prevalence of HD was 75.6%, with a mean age of onset of 4.6 (SD: 2.7) years. When stratified by SMA type, the prevalence/age of onset (mean, years) was 84%/3.1 (SD: 1.7), 80%/5.8 (SD: 2.3), and 36%/9.0 (SD: 4.3), respectively. HFMS score >23 was protective against HD by receiver operating characteristic analysis ( P =0.008). Significant risk factors by univariate analysis were SMA type I ( P =0.002) and II ( P =0.002), HFMS ≤23 ( P =0.01), nonambulatory status (Functional Mobility Scale at 50 m = 1, P =0.001), clinically relevant scoliosis ( P =0.01), and DMA treatment ( P =0.01). By multivariate analysis, only SMA type II ( P =0.04) and scoliosis ( P =0.04) were independent risk factors. CONCLUSIONS: The prevalence of HD in SMA is highly linked to disease severity. Identified risk factors can be used in the development of surveillance programs for early detection of HD in SMA, allowing for timely management. LEVEL OF EVIDENCE: Level III.
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Ulusaloğlu et al. (2023) conducted a cohort in Spinal muscular atrophy (SMA) (n=82). Risk factors including SMA type, functional level, scoliosis, and disease-modifying treatments vs. Reference groups was evaluated on Prevalence of hip displacement (migration percentage ≥40%). In children with spinal muscular atrophy, the overall prevalence of hip displacement was 75.6%, with SMA type II (P=0.04) and clinically relevant scoliosis (P=0.04) as independent risk factors.
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