Lower limb development and gait kinematics of back-carried Setswana children

Abstract

Back-carrying (BC) of children is a common phenomenon among African mothers. Children are often back-carried (BC) by their mothers for long durations, well into their toddler years. Positive relationships between BC and hip development, particularly in the prevention of developmental hip dysplasia have been shown, but it is unknown how knee and lower limb (LL) development will be impacted. This study aimed to determine what possible relationships exist between static- and kinematic LL development in BC children, compared to their non-back-carried (non-BC) counterparts. Five objectives, of a cross-sectional design, were developed to address the aim. Firstly, LL development, in terms of the tibiofemoral angle (TFA), quadriceps-angle (Q-angle), hip anteversion angle (AVA) and the tibial torsion angle (TTA) of two- to nine-year-old Setswana-speaking children, were profiled. Goniometry was applied to determine LL angles. The second objective was to determine the relationships between BC and LL development in the frontal plane (objective two) and the transverse plane (objective three). A questionnaire was developed to determine whether children were BC, swaddled and/or pushed in a pram or stroller and the frequencies and durations they were BC or the alternative methods of carrying. A Classification and Regression Tree (CART) analysis was applied, grouping the participants according to their LL development and BC information, age and sex. The fourth objective aimed to determine the predictor factors for LL deviation in BC children. Predictor factors were obtained by applying the data from the first three objectives, in an Automatic Linear Modelling (ALM) analysis. The last objective aimed to determine what possible kinematic differences exist, specifically at the tibiofemoral joint (TFJ), between BC and non-BC children. Bayesian analysis of TFJ angles, observed in all three cardinal planes at heel-strike, mid-stance and toe-off was applied. General LL development progressions are similar in comparison to children of other ethnicities (Americans, Europeans, Asians and Nigerians), in terms of increases and decreases in angles with age. The TFA and Q-angles compares closest with those found in American- and Indian children respectively. Hip AVAs are far greater and greater internal TTAs are observed in Setswana-children, than in European children. The CART reveals children BC more frequently present with greater genu valgum, greater TTA and smaller AVA, than less frequently BC or non-BC children. Overall 11 significant predictors of LL alignment exist of which age is consistently the greatest predictor. For the TFA, longer swaddling durations and earlier independent walking age contributes to greater valgus TFAs. In the transverse plane, increased BC durations predicts lower AVAs. Due to the aforementioned relationships between static LL measures and BC, we expected dynamic, kinematic

differences. Bayesian comparison of angles of the TFJ during kinematic gait of BC with non-BC children, do not render any conclusive results. Based on all the results, BC of children do not seem to impact the development of the LL in a detrimental manner. Previously, other researchers hypothesised that BC prevents developmental hip dysplasia, thus we recommend mothers or primary caregivers to continue back-carry (BC) their young, but in moderate frequencies and durations, based on our LL development findings. Moderation is recommended based on the detrimental impact of long duration BC on cognitive function, as found by other researchers previously.