Does the sesamoid rotation angle change differently in subjects with hallux valgus considering foot position during assumed walking? A pilot study.

Hallux valgus (HV) entails changes in the alignment of the rotating sesamoids and a shift of the abductor hallucis muscle (ABH) in the plantar direction, decreasing the abductor force. Load on the foot while walking may change the sesamoid rotation angle (SRA). Nevertheless, no study has investigated the relationship between the change in SRA during assumed walking and ABH muscle size. The aim of our study was to examine the changes in SRA at different foot postures assumed to generate skeletal alignments during walking and muscle size of the ABH in participants with HV and to discuss the association between the change in the SRA and cross-sectional area (CSA) of the ABH. Thirteen female participants were recruited and divided into the HV and non-HV groups according to the HV angle. The SRA and cross-sectional area of the ABH were measured using B-mode ultrasound. The SRA was measured under four conditions; sitting, standing, mid-stance, and pre-swing posture. The CSA was assessed in the supine position. In all postures, the SRA increased more in the HV group than in the non-HV group (p < 0.05). The change in the SRA at the pre-swing posture was greater in the HV group than in the non-HV group (p < 0.05). The change in the SRA at pre-swing posture negatively correlated with the CSA of the ABH in the HV group (r = -0.554, p < 0.05). In the HV group, increasing the load on the forefoot enhanced the sesamoid rotation. Abductor torque on the ABH decreased with ABH displacement as the sesamoids moved laterally in the pre-swing. Repeated walking increased sesamoid rotation and led to HV progression. Therefore, it may be beneficial to use an orthosis or arch pad that corrects pronation of the metatarsal with the rotation of the sesamoids.

Contribution of Plantar Fascia and Intrinsic Foot Muscles in a Single-Leg Drop Landing and Repetitive Rebound Jumps: An Ultrasound-Based Study.

The plantar fascia and intrinsic foot muscles (IFM) modulate foot stiffness. However, it is unclear whether the corresponding ultrasonography findings reflect it. This study aimed to examine the effect of the plantar fascia and IFM morphologies on force attenuation during landing and reactivity when jumping in healthy adults (n = 21; age, 21-27 years). Thickness, cross-sectional area (CSA), and hardness of the plantar fascia, abductor hallucis (AbH), and flexor hallucis brevis (FHB) muscles were measured using ultrasonography. Single-leg drop landing and repetitive rebound jumping tests assessed the ground reaction force (GRF) and reactive jump index (RJI), respectively. The CSA of FHB was negatively correlated with maximum vertical GRF (r = -0.472, p = 0.031) in the single-leg drop landing test. The CSA of AbH was negatively correlated with contact time (r = -0.478, p = 0.028), and the plantar fascia thickness was positively correlated with jump height (r = 0.615, p = 0.003) and RJI (r = 0.645, p = 0.002) in the repetitive bound jump test. In multivariate regression analysis, only the plantar fascia thickness was associated with RJI (ß = 0.152, 95% confidence interval: 7.219-38.743, p = 0.007). The CSA of FHB may contribute to force attenuation during landing. The thickness of the plantar fascia and CSA of AbH may facilitate jumping high with minimal contact time.

Intrinsic foot muscle hardness is related to dynamic postural stability after landing in healthy young men.

BACKGROUND: The human foot has competent mechanisms for supporting weight and adapting movement to various surfaces; in particular, the toe flexor muscles aid in supporting the foot arches and may be important contributors to postural stability. However, the role of intrinsic foot muscle morphology and structure in the postural control system remains unclear, and the relationship between them is not well known. RESEARCH QUESTION: Are intrinsic foot muscle morphology and toe flexor strength related to static and dynamic postural stability in healthy young men?. METHODS: A total of 27 healthy men aged 19-27 years participated in this study. intrinsic foot muscle morphology included muscle hardness and thickness. Cross-sectional area was measured by ultrasonography at an ankle dorsiflexion angle of 0°. The hardness of the abductor hallucis (AbH), flexor hallucis brevis, and flexor digitorum brevis (FDB) muscles was measured using ultrasound real-time tissue elastography. Static postural stability during single-leg standing on a single force platform with closed eyes was assessed for the right leg. In the assessment of dynamic postural stability, the subjects jumped and landed on single-leg onto a force platform and the dynamic postural stability index (DPSI) was measured. RESULTS: FDB muscle thickness showed a positive correlation with anteroposterior stability index (APSI) (r = 0.398, p = 0.040). AbH muscle hardness was negatively correlated with APSI (r = -0.407, p = 0.035); whereas FDB muscle hardness was positively correlated with DPSI (r = 0.534, p = 0.004), vertical stability index (r = 0.545, p = 0.003), and maximum vertical ground reaction force (r = 0.447, p = 0.020). Multiple regression with forced entry revealed that only DPSI was significantly correlated with FDB muscle hardness (p = 0.003). SIGNIFICANCE: The results indicated that intrinsic foot muscle hardness plays an important role in dynamic postural control among healthy young men, which may enable a more rapid muscular response to changes in condition during jump landing and better performance in balance tasks.