Foot flexibility confounds the assessment of triceps surae extensibility in children with spastic paresis during typical physical examinations

• Published in: Journal of biomechanics 2020-01, Vol.99, p.109532-109532, Article 109532
• Main Authors: Weide, Guido, Huijing, Peter A., Becher, Jules G., Jaspers, Richard T., Harlaar, Jaap
• Format: Article
• Language: English
• Subjects: Ankle; Assessments; Cerebral palsy; Children; Electromyography; Extensibility; Feet; Flexibility; Foot deformation; Joint range of motion; Joints (anatomy); Muscles; Paresis; Physical examinations; Plantar flexion; Spastic paresis; Spasticity; Typical development
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2019.109532

•Foot flexibility confounds foot sole based estimates of muscle-tendon complex lengths.•No difference in Foot flexibility between groups of children with and without SCP.•Thirty percent of foot sole rotation was related to foot flexibility. Accurate assessment of the talo-crural (ankle) joint angle at physical examination is important for assessing extensibility of m. triceps surae (TS) in children with spastic cerebral paresis (SCP). The main aim of this study was to quantify foot flexibility during standardized measurements of TS muscle-tendon complex extensibility (i.e. based on foot-sole rotation) in SCP children, and typical developed (TD) ones. Additionally, we aim to define a method that minimizes the confounding effects of foot flexibility on estimates of talo-crural joint angles and TS extensibility. Children, aged 6–13 years, with SCP (GMFCS I-III, n = 13) and TD children (n = 14) participated in this study. Externally applied −1 Nm, 0 Nm, 1 Nm and 4 Nm dorsal flexion foot plate moments were imposed. Resulting TS origin-insertion lengths, foot sole (φFoSo) rotations, and changes in talo-crural joint angle (φTaCr) were measured. Foot flexibility was quantified as Δ(φTaCr -φFoSo) between the 0 Nm and 4 Nm dorsal flexion conditions. In both groups, φFoSo rotations of approximately 20° were observed between 0 Nm and 4 Nm dorsal flexion, of which about 6° (≈30%) was related to foot flexibility. Foot flexibility correlated to φFoSo (r = 0.69) but not to φTaCr (r = 0.11). For φFoSo no significant differences were found between groups at 4 Nm. However, for SCP children the mean estimate of φTaCr was 4.3° more towards plantar flexion compared to the TD group (p