Foot and Ankle Abnormalities in the Hurler Syndrome

Abstract

After successful hematopoietic stem cell transplantation maintaining function and mobility has become the key goal in the management of patients with mucopolysaccharoidosis type 1 (MPS-1). We detail the foot and ankle pathology in 18 patients with MPS-1 managed in our unit. Functional assessment was performed using the Oxford Foot and Ankle Questionnaire for children (OxAFQ-C). Morphologic assessment was performed by means of a mirrored foot photograph box, the Foot Posture Index (FPI), and clinical photography. Standardized radiologic investigations were sought when clinically warranted. Average lateral talus-first metatarsal angle, anteroposterior and lateral talocalcaneal angles, and lateral distal tibial angle (LDTA) were determined. The average patient-reported OxAFQ-C score was 44.7 (range, 10 to 60). The average proxy-reported OxAFQ-C score was 45.7 (range, 11 to 60). Ten of the 18 patients wore customized footwear. Of the 36 feet examined 11 were found scored as "highly pronated" (FPI>+9), 12 feet had a "pronated posture" (FPI +6 to +9), and 13 feet were found to have a "normal posture" (FPI 0 to +5). Thirteen of the 18 (72%) patients studied had curly toes. The average talus-first metatarsal angle recorded was 10.7 degrees (range, -7 to 30 degrees). The average lateral and anteroposterior talocalcaneal angles were 45.8 degrees (range, 16 to 62 degrees) and 31 degrees (range, 1 to 51 degrees), respectively. The average LDTA was found to be 70.6 degrees (range, 48 to 82 degrees). A single-sample Student t test shows significant divergence of measured LDTA, OxAFQ-C, and FPI from normal populations (P<0.005). MPS-1 is associated with a significant degree of foot and ankle pathology that has not been previously described. We found a high incidence of curly toes, ankle valgus, functional foot, and ankle disability and a requirement for customized footwear among our cohort. We recommend that careful assessment of foot and ankle pathology should be routine in the interdisciplinary management of patients with MPS-1. Level III.