Introduction: Therapeutic bone marrow transplantation has increased survival in Hurler syndrome, but the effects on musculoskeletal development remain unclear. Long term reports on mobility are poor, with many patients gradually losing walking ability in later childhood secondary to hip subluxation and joint contractures. As previous cohorts are small, data is limited.

Methods: We detail the follow up of twenty patients over a mean of 94 months (range 1 – 17.4 years). Radiographs were assessed for hip dysplasia using acetabular angle of Sharp, centre edge angle of Wiberg and tibiofemoral shaft angle. Clinical examination was performed at an annual multidisciplinary assessment by one clinician and compared against age matched controls. 3D gait analysis was performed on eight older children, and deviance in kinematic variables was plotted against controls with Mann-Whitney U test for statistical analysis.

Results: All patients demonstrated characteristic ace-tabular dysplasia. Fourteen patients have undergone containment surgery at a mean of 4.4 years. Innominate osteotomy is an essential part of this. Mean preoperative acetabular angle was reduced from 34 ± 4° to 22 ± 3°. Femoral head containment is maintained, with mean centre edge angle in older patients 39 ± 7°. Genu valgum is observed early, and five patients underwent medial epiphyseal stapling at a mean of 7.8 years, decreasing tibiofemoral angle by a mean of 8.0°. All patients are currently independently mobile, with restriction of internal hip rotation being the only significant clinical finding (P< 0.001). Joint contractures were not noted. Walking speed and stride length were comparable to controls, but endurance is reduced by about one quarter. Gait analysis demonstrates a characteristic pattern, with anterior pelvic tilt secondary to thoracolumbar gibbus, relative hip flexion throughout the gait cycle, valgus knees and compensatory pronated feet; all measured deviations were significant (P< 0.001).

Conclusions This large group maintained successful hip containment and good mobility throughout childhood. Innominate osteotomy alone has been used recently. Despite plain film appearance, genu valgum is a functional problem in gait, and we would anticipate greater use of corrective stapling in the future. This is the first report of gait analysis in Hurler syndrome, and features specific to the condition are described.

Background: A sharp, localised, thoracolumbar gibbus is pathognomonic of the mucopolysaccharidosis (MPS) group of disorders, the most common of which is Hurlers syndrome (MPS I). Untreated patients with this disease run an inevitable course of neurological and physical degeneration until death within the first decade. Haemopoietic stem cell transplantation (HSCT) has resulted in considerable improvement in survival with amelioration of many of the symptoms and signs which characterise this disease. Data, however, is disappointing in relation to the impact of HSCT on skeletal dysplasia. This study reviews the natural history of spinal deformity in Hurler’s syndrome after HSCT in infancy.

Methods: Twenty three patients (12 male and 11 female), transplanted at a mean age of 0.9 years ± 0.47, (range 0.27 – 1.8yrs) were investigated, of whom 19 were at least two years post-HSCT and were included. HLA identical donor sources included unaffected or heterozygote family members, unrelated adults or cord blood. Mean age at review was 9.4 years ± 4.57, (range 2.5 – 18.4yrs). Serial measurements of the thoracolumbar spines incorporated clinical records, radiographs and surface topography. The thoracolumbar gibbus was measured on lateral spinal radiograph using the standard adaptation of the Cobb method. Two segments of the spine were documented: the gibbus itself and the thoracic profile above it. Clinical assessment and surface topography were contrasted with this.

Results: At presentation, all showed the characteristic gibbus at the thoracolumbar junction, with a flat and stiff thoracic spine above. Three patients underwent surgery to correct or maintain the gibbus, which was unsuccessful in two; the third is stable, but still young. Two patients have developed scoliosis: one in the juvenile period and one in infancy. Three female patients are now post-menarchal and have shown no progression of their gibbus. One male patient, now aged 19 years, had significant progression of his gibbus at puberty, but is now stable, untreated and cosmetically acceptable. The remainder are still pre-pubertal but their deformities are not currently progressive.

Conclusion: The fate of the spinal deformity in untreated MPS-I has been poorly documented, as the condition was invariably fatal from cardiorespiratory failure during the first decade. These interim results suggest that, while the deformity persists and may become more pronounced during growth and adolescence, it does not significantly impact on quality of life. The considerations which usually dictate intervention in other spinal deformities of childhood may not necessarily apply and should be approached with caution. The more recent availability of recombinant human -L- iduronidase adds further interest to the management of these patients and warrants cautious expectation , in the context of experience gained in these groups of patients. In conclusion atients with MPS I have complex multisystem disorders, independent of their orthopaedic status. While monitoring their spinal deformity is indicated, over-intrusive investigation and treatment may be counterproductive.