6136 Hip instability in children with spinal muscular atrophy: a single centre retrospective study in the United Arab Emirates, 2018–2023

Objectives To assess Hip Instability in children with Type 1, 2 and 3 Spinal Muscular Atrophy in Dubai, Al Jalila Children's Specialty Hospital. Methods This is a retrospective cohort study where data analysis has been performed on a cohort of 54 children with a genetic diagnosis of SMA. Patients were grouped based on their SMA type (SMA type 1, 2, or 3) and their motor function level (non-sitters, sitters, or walkers). Relevant parameters were collected and compared including Hip Subluxation/Dislocation (which was measured on a hip x-ray using the Migration Index, Acetabular Index, and Acetabular depth to width ratio), degree of scoliosis (measured by the Cobbs angle), number of SMN2 copies, and age of patient. Results Out of the 54 patients, 34 of them were type 1 SMA, 16 were type 2 SMA, and 4 were type 3 SMA. After multiple comparisons of the data using the Chi-squared test, several significant relationships were found, including the data found in table 1 which shows the prevalence of hip instability within the different types of SMA. Hip dislocations were only found in patients with type 1 SMA and presence of subluxation in both hips was most prevalent in patients with type 1 SMA (p=0.046). Better motor function levels also correlated with an increased number of SMN2 copies (p=0.008). With regards to the presence of scoliosis, there was no significant correlation between the presence of hip subluxation/dislocation and scoliosis. Patients with fewer SMN2 copies were more likely to have scoliosis (p=0.023). Out of 24 patients with 2 copies of SMN2, 16 of them had scoliosis. On the other hand, out of 14 patients with 3 copies of SMN2, only 3 had scoliosis. Conclusion This study has provided data on hip subluxation and scoliosis in children with SMA for the first time in the UAE and the region. Hip dislocation/subluxation seems to be most severe in type 1 SMA patients, with increased presence of bilateral subluxation or dislocation compared to other SMA types. A lower number of SMN2 copies correlates with increased occurrence of scoliosis.