Orthopedic Management in Patients Affected by Spinal Muscular Atrophy: Retrospective Analysis of a Single Institute Experience and Review of the Literature

Background: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease that affects motor neurons and leads to hypotonia and muscle weakness. SMA causes systemic involvement and requires a multidisciplinary approach. Orthopedic management focuses primarily on the treatment of scoliosis, one of the most serious complications contributing to worsening lung function. Currently, spinal surgery is the treatment of choice. Padua University Hospital is recognized as one of the centers of excellence for orthopedic and multidisciplinary management of this disease. Objectives: This study aims to improve knowledge on the orthopedic management of SMA patients through the experience of a single institute and a review of the literature. Specifically, the study intends to investigate the natural progression of scoliosis and analyze spine surgery patterns in patients with SMA. Methods: An analysis of longitudinal data from 34 patients treated at the Padua University Hospital was conducted. Linear regression analyses are used for studying the progression of scoliosis in relation to age. The study population was divided into several subgroups to investigate scoliosis progression in relation to prognostic factors such as type of SMA, motor function, treatment with DMTs and HFMSE scores. For each subgroup, a trend of natural scoliosis progression was obtained. Results: The most severe scoliosis progression was observed in patients with SMA type 1, with an average annual Cobb angle progression of 7.928°, and in non-sitter patients, who exhibited an average annual progression of 6.792°. Severe scoliosis developed early in SMA type 1 patients, with 78% of these patients reaching a Cobb angle greater than 40° by age 6. The probability of scoliosis surgery in patients with at least 15 years of follow-up, was 60% in SMA type 1, 100% in SMA type 2, and 75% in SMA type 3. 100% of patients with SMA type 3, who lose the ambulation before the age of ten, underwent scoliosis surgery. Mean age at surgery was 7 for SMA type 1, 12.36 for SMA type 2, and 13.33 for SMA type 3. Surgery type varied with age: 100% of patients under 10 underwent surgery with Growing Rods, while patients over 10 underwent Spinal Fusion, with 82% using metal wires and 18% using pedicle screws. Motor function, measured using the HFMSE scale, was inversely correlated with the Cobb angle (p < 0.05). Conclusions: Compromised motor function and loss of ambulation are predictors of severe scoliosis progression. Scoliosis monitoring should begin in the first years of age for SMA type 1 patients. Continuous follow-up is essential to detect early severe scoliosis progression.