Comparison of tri-planar lower-limb kinematics and the association with tibial torsion in back-carried children. A statistical parametric mapping approach.

BACKGROUND

Lower-limb kinematic and temporospatial differences between back-carried (BC) and non-back-carried (NBC) children are expected based on previous static lower-limb relationships reported in BC children. Back-carrying of children is common among South Africans and becoming popular among Westerners. Establishing the potential effects of back-carrying on lower-limb development and gait is therefore important.

RESEARCH QUESTION

Does BC influence the tri-planar instantaneous lower-limb kinematics and temporospatial parameters of the full gait cycle in children, and is there an association between static tibial torsion and the lower-limb gait kinematics?

METHODS

Twelve NBC (age = 8.00 ± 0.95 years) and 12 BC (age = 8.08 ± 0.79 years) children were selected. Tri-planar kinematics of the hip, knee, and ankle were captured during gait using an eight-camera motion analysis system and Visual3D software to extract the kinematic data. All static tibial torsion were measured goniometrically. Statistical parametric mapping (SPM) was used to compare joint kinematics during the gait cycle and the association of tibial torsion throughout the gait cycle.

RESULTS

SPM revealed significant differences between BC and NBC participants in hip kinematics (mean difference = 2.49°, p = 0.016) at 52-66 % of the gait cycle and knee joint kinematics (mean difference = 3.00°, p = 0.026) at 34-41 % of the gait cycle. Temporospatial differences were non-significant for speed, stride length, stance time, and stride width (p = 0.80, g = 0.10). Significant correlations were evident between static tibial torsion and joint kinematics for the knee (r = -0.44 to -0.69, p = 0.041) for BC children and for the ankle (r = 0.74-0.75, p = 0.025) in NBC children. Larger internal tibial torsion is associated with more in-toeing and internal knee rotation during the swing phase in back-carried children.

SIGNIFICANCE

A discrete comparison of kinematics in BC versus NBC children did not yield significant differences, while differences were observed using the SPM. The observed differences are likely of limited clinical importance, implying that caregivers can continue to BC their children.