The impact of novel nusinersen treatment on hip stability in spinal muscular atrophy patients

Abstract

Introduction: Hip instability is common in spinal muscular atrophy (SMA) patients due to muscle imbalance. Nusinersen, a novel treatment, has documented effects on improving strength and functionality. Our study aimed to evaluate the effects of nusinersen on hip subluxation. Methods: This is a retrospective study of all SMA patients who received nusinersen at our institution from 2018 to June 2021. We included all patients with SMA who received nusinersen and had post-treatment assessments. We excluded those who received hip surgery within the study period. Baseline X-rays taken at pre-nusinersen screening were compared to the latest X-rays using Reimer’s migration index (RMI). Clinically significant changes were defined as progression from reduced to subluxed/dislocated or from subluxed to dislocated and as progression of RMI from <0.5 to >0.5 or from >0.5 to >0.8. Results: The average follow-up period was 22 months (range, 14-36). RMI progressed in 10 out of 16 hips in type I patients, 7 out of 16 hips in type II patients, and 2 out of 4 hips in type III patients. In hips with RMI progression, 4 were clinically significant in type I, 3 were clinically significant in type II, and none were clinically significant in type III. Discussion and Conclusion: Preliminary results show some progression in hip instability in SMA patients treated with nusinersen. More studies with longer follow-up periods are required to monitor the long-term effects. SMA patients on nusinersen require closer monitoring for hip instability and more aggressive management may be warranted.