Background: Total-contact orthosis (TCO) is one kind of foot orthosis (FO) that is used to adjust biomechanics in flexible flatfoot.
Objective: To determine the effects of a TCO on the MLA moment, MLA deformation angle and lower limb biomechanics.
Study design: Cross-sectional study.
Methods: Seven-flatfoot and thirteen-normal foot subjects were recruited by footprint and radiographs. The biomechanics of subjects with normal foot (NF), flatfoot with shoe only (FWOT) and flatfoot with TCO (FWT) were collected in a 3D motion analysis laboratory and force plates. The MLA and lower limb biomechanics in each condition during specific sub-phases of stance were analyzed.
Results: The NF had larger MLA eversion moment after shod walking ( p = 0.001). The FWT condition compared with the FWOT condition had a significantly larger peak MLA upward moment ( p = 0.035) during pre-swing, larger peak knee external rotation angle ( p = 0.040) during mid stance, smaller peak knee extension moment during terminal stance ( p = 0.035) and a larger ground reaction force in the anterior-posterior direction during early stance ( p < 0.05).
Conclusion: Our study found positive effects from the customized TCOs which included an increased TCO angle that led to a decreased peak MLA moment in the frontal plane in flexible flatfoot subjects during walking. Clinical relevance Lower limb biomechanics is different from normal in subjects with flexible flatfoot. The design of a TCO affects MLA, ankle and knee biomechanics and may be used to clinically correct biomechanical changes in flexible flatfoot.
Keywords: Medial longitudinal arch; biomechanics; flexible flatfoot; total-contact orthosis.