Introduction: Thoracolumbar kyphosis is a skeletal manifestation of Mucopolysaccharidosis I (MPS‐I), Hurler syndrome. We present the largest case series in the published literature to date in order to define its natural history and management.
Methods: Forty two patients with MPS‐I had treatment with bone‐marrow transplantation and/or enzyme replacement therapy between June 1995 and October 2007. These patients had regular systematic clinical review and were seen at least annually. Standing lateral radiographs of the thoracolumbar spine taken at these visits were retrieved, digitized, enhanced using computer software (Adobe Photoshop CS4, Adobe Systems Inc.) and the Cobb angle measured (Screen Protractor 4.0, Iconico). Statistical analysis was performed using mean values, standard deviation (SD), 95% confidence intervals (95% CI) and repeated measures ANOVA.
Results: All patients had been followed up for a mean of 2years 8months. At initial examination (average age 1year 1month) the thoracolumbar kyphosis measured an mean of 40 degrees (SD 12 degrees). Five patients underwent anterior vascularised rib graft at an average age of 3 years for progressive deformity ‐ mean Cobb angle pre‐operatively was 53 degrees and at final follow‐up (average 8years 10months) was 44 degrees. Analysis of non‐operatively treated patients revealed that patients with an initial Cobb angle (at an average age of 1 year 2months) of less than 40 degrees were statistically significantly (p=0.005) less likely to develop progressive kyphosis over the average follow‐up period of 3.5 years (mean initial Cobb angle 30 degrees and at final follow‐up 34 degrees) than those with an initial Cobb angle greater than 40 degrees (mean Cobb angle initially 46 degrees and at final follow‐up 61 degrees).
Conclusion: Thoracolumbar kyphosis is of variable severity in Hurler's syndrome and those who present with a Cobb angle of greater than forty degrees are significantly more likely to develop progressive kyphosis. Treatment in the form of vascularised rib graft in these patients appears to arrest progression of the deformity.
Significance: This study outlines the previously undefined natural history of thoracolumbar kyphosis in Hurler syndrome, its clinical management and results of treatment.