Musculoskeletal modelling of childrens gait

Abstract

Introduction and aim: Musculoskeletal modelling allows for a greater in-depth analysis of gait. Although it has been performed extensively in adults, producing validated muscle activity during various movements, musculoskeletal modelling of children has only been performed at the ages of 6 years old and above [1]. Previous work using EMG found that during locomotion in toddlers muscle activity varieswithmaturityof gait [2]. Thematuringorganisation of muscles appeared to make the muscular coordination more efficient. The present study aims to assess variables that are not able to be compared through the sole use of motion capture software. The variables to be assessed are the joint reaction forces (JRF) in the femoral head and muscle forces in the lower extremities at key stages of the gait cycle, with the aim of comparing changes found between the age groups. Patients/materials and method: Five children aged three to seven years old were studied, one subject from each age, and an adult subject (24 years old). Gait data was collected using a 10 ProReflex MCU (Qualisys, Sweden). A lower limb standard Helen Hayes marker set was used and the data was then processed in Visual 3d (C-motion, Sweden). Data fromVisual 3d, in a c3Dfile format was then input to AnyBodymusculoskeletal modelling system (AnyBody Technology, Aalborg, DEN). Kinematic, kinetic and muscle forcedatawas thennormalised to100%of thegait cycle.Analysis was performed at key phases in the gait cycle; namely: initial contact, double support,mid-stance, toe off, pre-swing,mid-swing and end-swing. Results: Kinematic results revealed adult-like patterns in all ages, all fallingwithin a normative range. JRF (Fig. 1)were shown to vary between ages quite dramatically, with, values of 537% bodyweight and 613% bodyweight observed in the threee and six year old, respectively at single stance phase (20% gait cycle). Hip abductor muscle forces, specifically the semitendinosus (Fig. 2), were ∼50% lower in the adult at the end of stance phase compared to the three year old. Further results will be presented detailing muscle activity during gait. Discussion and conclusions: The musculoskeletal modelling revealed a much higher JRF in the juvenile models, which may be related to an immature gait pattern, showing less control over the gait cycle. However, walking speed was much higher in the children, and this would directly influence the JRF. The activity of the muscles articulating the hip and the anklewill be discussed to identify anymaturation developments in the attainment of an adult gait pattern. One hypothesis is that a decreased dependency on the hip Fig. 1. Resulting forces at the femoral head for the five ages and the adult over 100% gait cycle.