Thoracolumbar Kyphosis in Treated Mucopolysaccharidosis 1 (Hurler Syndrome)

Study Design. A retrospective radiographical follow-up study of thoracolumbar deformity in 33 children with mucopolysaccharidosis 1 (Hurler syndrome). Objective. To report the severity, natural history, risk factors for progression, and results of intervention for thoracolumbar kyphosis in children with Hurler syndrome. Summary of Background Data. Literature on the subject of thoracolumbar kyphosis in Hurler syndrome and its treatment is limited to small case series. The natural history and thus indications for intervention are unknown. Methods. Patients who had been treated with bone marrow transplantation and/or enzyme replacement therapy were followed up with erect radiographs of the spine. Mean follow-up period was 3.5 years (range, 2-12 yr). Radiographs were retrieved and analyzed retrospectively. Seven patients underwent varied forms of surgical intervention for progressive deformity, the technique and principles of which are described. Results. The thoracolumbar kyphosis on initial radiographs obtained at a mean age of 17 months measured 38 degrees (95% confidence interval, 34 degrees-42 degrees). Fifteen of the 33 patients (45%) followed for more than 2 years developed a deformity that made a progression of more than 10 degrees. The magnitude of the initial deformity was predictive of whether the deformity progressed (univariate analysis, P < 0.001). An initial kyphosis angle greater than 45 degrees was predictive of progression of more than 10 degrees with sensitivity of 67% and specificity of 88%. All patients who underwent surgical intervention had sustained improvement in the magnitude of thoracolumbar deformity. Conclusion. Thoracolumbar kyphosis in Hurler syndrome is of variable severity with an average deformity, in our series, of 38 degrees at a mean age of 17 months. Forty-five percent of patients developed progression of greater than 10 degrees. Patients with an initial deformity greater than 45 degrees seemed to be more likely to progress. Surgical interventions in the form of anterior fusion, combined anterior and posterior surgery and use of the vertical expandable prosthetic titanium rib provided good correction.