Atlantoaxial instability treated with free-hand C1-C2 fusion in a child with Morquio syndrome.

Mucopolysaccharidosis type IVA, also known as Morquio syndrome, is an autosomal recessive lysosomal storage disease. Skeletal dysplasia with short stature, dysplastic-hypoplastic dens (os odontoideum), ligamentous hyperlaxity, and C1-C2 instability are characteristic features. Most patients with Morquio syndrome present with compressive myelopathy at a young age as a result of a combination of C1-C2 instability and extradural soft tissue thickening; treatment generally consists of anterior decompression with occipito-cervical fusion and external orthosis. In this report, we describe the successful treatment of a young child using posterior C1-C2 fusion alone with a free-hand technique. A 3-year-old boy presented at our hospital with a 5-month history of progressive quadriparesis. A whole-body skeletal survey showed skeletal dysplasia with hypoplasia, thoracolumbar kyphosis, and atlantoaxial subluxation. Preoperative cervical imaging showed compressive myelopathy at C1-C2 and atlantoaxial subluxation. C1-C2 fixation and decompression were performed successfully. After the operation, the patient had improved strength and was able to walk independently 8 months postoperatively. Establishment of stability via C1-C2 fusion is challenging in patients with genetic disorders characterized by skeletal dysplasia because of these young patients' small bone size and deficient bone quality. In this unique case, the treatment consisted solely of C1-C2 fusion with a free-hand technique. This case report presents a new approach in the treatment of atlantoaxial instability in Morquio syndrome.