Evaluation of Gait Pattern and Lower Extremity Kinematics of Children with Morquio Syndrome (MPS IV).

Jose J Salazar-Torres,W G Stuart Mackenzie,William G Mackenzie,Chris Church,Lydia Fisher,M Wade Shrader,Thomas Shields

doi:10.3390/diagnostics11081350

Abstract

Morquio syndrome (mucopolysaccharidosis IV/MPS IV) is a genetic disorder leading to skeletal abnormalities and gait deviations. Research on the gait patterns and lower extremity physical characteristics associated with skeletal dysplasia in children with MPS IV is currently limited. This research aimed to provide baseline gait patterns and lower limb skeletal alignment of children with MPS IV utilizing three-dimensional instrumented gait analysis. This Institutional Review Board-approved retrospective study evaluates the kinematics of the lower extremities of children with MPS IV during gait, comparing them with an age-matched group of typically developing children. Thirty-three children with MPS IV were included (8.6 ± 4.0 years old). Children with MPS IV walk with increased anterior pelvic tilt, knee valgus, knee flexion, external tibial torsion, and reduced walking speed and stride length (p < 0.001). Multiplanar abnormal alignment results in abnormal knee moments (p < 0.001). Limited correlations exist (r = 0.69–0.28) between dynamic three-dimensional measurements of knee varus/valgus and rotational alignment and traditional static two-dimensional measures (physical examination or radiographs) suggesting the possibility of knee instability during gait and the benefits of dynamic assessment.

Highlights

Mucopolysaccharidosis IV (MPS IV), or Morquio syndrome, is a rare progressive genetic disorder that has a well-known effect on lysosomal storage metabolism, which affects the development of connective tissue [1,2,3,4]
Most previous orthopedic studies on MPS IV have focused on the atlantoaxial stability of the cervical spine [2,7,8,9,10]; fewer studies have investigated the severity of lower extremity deformities including genu valgum, ankle valgus, progressive hip dysplasia, and other physical attributes, such as joint laxity, and their impact on 3D gait patterns [7,8]
While a previous paper from our group described 3D gait analysis, clinical examination, and radiographic data on 9 children diagnosed with MPS IV, this is the first study to report in a large number of patients, providing a further comparison on torsional measurements and correlations between 3D kinematics and physical examination

Summary

Introduction

Mucopolysaccharidosis IV (MPS IV), or Morquio syndrome, is a rare progressive genetic disorder that has a well-known effect on lysosomal storage metabolism, which affects the development of connective tissue [1,2,3,4]. Common symptoms of MPS IV include skeletal manifestations affecting the spine and extremity alignment, decreased joint stability, and altered gait kinematics with wide-ranging levels of severity dependent on each child [2,3,4]. The incidence of MPS IV ranges from 1/76,000 births in Northern Ireland to 1/640,000 births in Australia, with some symptoms presenting as late as 3 years of age [1,4]. Most previous orthopedic studies on MPS IV have focused on the atlantoaxial stability of the cervical spine [2,7,8,9,10]; fewer studies have investigated the severity of lower extremity deformities including genu valgum, ankle valgus, progressive hip dysplasia, and other physical attributes, such as joint laxity, and their impact on 3D gait patterns [7,8]. Further investigations to understand the variability in lower extremity deformities in children with MPS IV and the relationship between their severity and dynamic outcomes are warranted

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