Hip Instability in Children With Spinal Muscular Atrophy: A Retrospective Study

Area of Science:

• Pediatric Orthopedics
• Neuromuscular Disorders
• Biomechanical Analysis

Background:

• Hip subluxation and dislocation are prevalent in pediatric spinal muscular atrophy (SMA).
• Children with SMA often lack hip monitoring due to medical complexity.
• Natural progression of hip instability and acetabular morphology in SMA is not well-described.

Purpose of the Study:

• To investigate the natural progression of hip instability in pediatric patients with all types of spinal muscular atrophy.
• To describe patterns of hip migration and acetabular morphology in children with SMA.

Main Methods:

• Retrospective chart review of pediatric SMA patients under 18 years old.
• Radiographic analysis of hip migration index (MI), acetabular depth ratio (ADR), and acetabular index (AI).
• Statistical modeling to assess the impact of SMA type and age on hip parameters.

Main Results:

• Hip subluxation (MI) differed significantly across SMA types (1, 2, and 3) by age 4.
• Acetabular depth ratio (ADR) decreased with age in all SMA types.
• Acetabular index (AI) values were higher than expected in unaffected populations, indicating altered morphology.

Conclusions:

• Hip subluxation occurs in all SMA types, progressing fastest in SMA type 1.
• Children with SMA exhibit distinct acetabular morphology and abnormal remodeling compared to unaffected peers.
• Increased orthopedic monitoring for hip instability is crucial for the growing population of mobile SMA patients.