BACKGROUND: Short foot exercise (SFE) can be combined with dynamic functional tasks such as squats; however, it is unclear whether this combination increases intrinsic foot muscle activity.
OBJECTIVE: This study aimed to investigate and compare the abductor hallucis muscle (AbdH) activity during SFE in static and dynamic functional tasks.
METHODS: The AbdH electromyography data of 17 healthy participants with and without SFE were analyzed during static tasks (sitting, double-leg standing, and single-leg standing) and dynamic tasks (double-leg squat, single-leg squat, split squat, and heel-raise). The static tasks were performed with SFE for 5 seconds, and the dynamic tasks were performed while performing SFE. AbdH activity with or without SFE during the task was compared using the Friedman and Wilcoxon signed-rank tests.
RESULTS: AbdH activity was significantly greater in conditions with SFE than in those without SFE for all tasks (P < 0.01) except for heel-raise (P = 0.163). AbdH activity during SFE in single-leg standing was significantly higher than that in sitting, double-leg standing, and double-leg squats (P < 0.05). AbdH activity during SFE in the single-leg squat was also significantly greater than that in the sitting position (P = 0.024). No significant differences were found in any other between-task comparisons of AbdH activity during SFE. AbdH activity during tasks without SFE revealed significantly lower levels for sitting and double-leg standing compared to single-leg squat, split squat, and heel-raise (P < 0.001). Additionally, the activity in double-leg squat was significantly lower than in both single-leg squat and heel-raise (P < 0.05).
CONCLUSIONS: Combining dynamic tasks, except for the heel-raise task, with SFE can increase AbdH activity more than dynamic tasks without SFE. However, clinicians should note that combining dynamic tasks with the SFE may not increase AbdH activity compared to combining static tasks with the SFE.

This study aimed to develop and evaluate a deep learning-based system for the automatic measurement of angles (specifically, Meary\'s angle and calcaneal pitch) in weight-bearing lateral radiographs of the foot for flatfoot diagnosis. We utilized 3960 lateral radiographs, either from the left or right foot, sourced from a pool of 4000 patients to construct and evaluate a deep learning-based model. These radiographs were captured between June and November 2021, and patients who had undergone total ankle replacement surgery or ankle arthrodesis surgery were excluded. Various methods, including correlation analysis, Bland-Altman plots, and paired T-tests, were employed to assess the concordance between the angles automatically measured using the system and those assessed by clinical experts. The evaluation dataset comprised 150 weight-bearing radiographs from 150 patients. In all test cases, the angles automatically computed using the deep learning-based system were in good agreement with the reference standards (Meary\'s angle: Pearson correlation coefficient (PCC) = 0.964, intraclass correlation coefficient (ICC) = 0.963, concordance correlation coefficient (CCC) = 0.963, p-value = 0.632, mean absolute error (MAE) = 1.59°; calcaneal pitch: PCC = 0.988, ICC = 0.987, CCC = 0.987, p-value = 0.055, MAE = 0.63°). The average time required for angle measurement using only the CPU to execute the deep learning-based system was 11 ± 1 s. The deep learning-based automatic angle measurement system, a tool for diagnosing flatfoot, demonstrated comparable accuracy and reliability with the results obtained by medical professionals for patients without internal fixation devices.

Background: Adult-acquired flatfoot deformity (AAFD) is characterized by partial or complete flattening of the longitudinal medial arch, which develops after maturity. AAFD secondary to posterior tibialis tendon dysfunction (PTTD) is one of professional athletes\' most common foot and ankle pathologies. Different modalities and procedures can be used to establish the diagnosis of AAFD and PTTD. However, imaging measurements such as the calcaneal inclination index and ultrasonography (US) of the posterior tibialis tendon (PTT) in professional athletes with medial ankle and focal pain along the PTT have yet to be widely studied. This study investigates the correlation of PTT ultrasound for evaluating PTTD with calcaneal inclination angle (CIA) for evaluating AAFD in professional athletes with medial ankle and focal pain along the PTT. Through this study, clinicians and radiologists may benefit from considering AAFD in athletes with PTTD. Methods: 112 Indonesian professional athletes with medial ankle or foot pain and focal pain along the direction of the PTT underwent foot radiography using the CIA and ankle ultrasound to observe PTT abnormalities. Results: A negative correlation between fluid thickness surrounding the PTT and the CIA (p<0.001; 95% CI - 0.945, - 0.885), as well as a negative correlation between PTT thickness and CIA (p<0.001, 95% CI - 0.926, - 0.845), with a correlation coefficient (r) of - 0.921 and - 0.892, respectively. No significant correlation was found between PTT tear and CIA (p = 0.728; 95% CI -0.223, - 0.159; r - 0.033). Conclusion: This study showed a negative correlation between PTTD and AAFD via ultrasound and CIA in professional athletes with medial ankle and focal pain along the PTT. A better understanding of PTTD and AAFD imaging will lead to more effective management and prompt treatment.

BACKGROUND: A flatfoot has been believed to be closely associated with the development of hallux valgus; however, the association is still controversial. Abnormal foot kinematics has been identified as a possible risk factor for the development of hallux valgus, but it remains unclear whether foot posture contributes to abnormal foot kinematics. This is the first study to investigate the differences in foot kinematics during gait between individuals with and without hallux valgus, while controlling for foot posture.
METHODS: Twenty-five females with hallux valgus and 25 healthy females aged 18 to 22 were recruited. Foot posture was measured using normalized navicular height truncated and the leg-heel angle. Foot kinematic and kinetic data during gait were recorded by a three-dimensional motion capture system. To investigate the characteristics of foot kinematics in individuals with hallux valgus while controlling for foot posture, we used a propensity score matching method. The matching was obtained by using the 1:1 nearest-neighbor procedure and a caliper width of 0.2.
RESULTS: Twelve pairs were matched. Individuals with hallux valgus had significantly increased midfoot dorsiflexion from 56% to 80% during stance phase, rearfoot eversion from 53% to 71%, and forefoot abduction from 5% to 29% compared with control.
CONCLUSIONS: Individuals with hallux valgus have a flexible foot that cannot suppress the dynamic deformation of the rearfoot and midfoot during gait. To suppress the development of hallux valgus, interventions that aim to prevent dynamic deformations of the rearfoot and midfoot during gait may be necessary, regardless of their static foot posture.

METHODS: Three cases of inflammatory joint diseases (systemic lupus erythematosus and ongoing juvenile idiopathic arthritis) with painful flexible progressive collapsing foot deformity (PCFD) underwent flatfoot surgery. All cases maintained sufficient radiological correction and achieved good clinical condition at final follow-up.
CONCLUSIONS: Although the prospect for recurrence of the deformity is not clear, even in inflammatory joint diseases, flat foot surgery such as flexor digitorum longs transfer, spring ligament reconstruction, and lateral column lengthening could have a possibility to be indicated against PCFD, as long as disease activity could be well suppressed by drug therapy, subsequently subtalar and talonavicular joints could be preserved.

The importance of the transverse tarsal arch (TTA) has recently been extensively reevaluated and has even been considered to play a greater role in foot stability than the medial longitudinal arch (MLA). However, the relevance of this observation in the context of common clinical foot disorders, such as progressive collapsing foot deformity (PCFD), has not yet been fully clarified. In this biomechanical study, we examined ten pairs of human cadaveric feet by serial weight-bearing cone-beam computed tomography under controlled loading using a custom-designed testing machine. The MLA and TTA were transected separately, alternating the order in two study groups. A semiautomated three-dimensional evaluation of their influence on three components of PCFD, namely collapse of the longitudinal arch (sagittal Meary\'s angle), hindfoot alignment (sagittal talocalcaneal angle), and forefoot abduction (axial Meary\'s angle), was performed. Both arches had a relevant effect on collapse of the longitudinal arch, however the effect of transecting the MLA was stronger compared to the TTA (sagittal Meary\'s angle, 7.4° (95%CI 3.8° to 11.0°) vs. 3.2° (95%CI 0.5° to 5.9°); p = 0.021). Both arches had an equally pronounced effect on forefoot abduction (axial Meary\'s angle, 4.6° (95%CI 2.0° to 7.1°) vs. 3.0° (95%CI 0.6° to 5.3°); p = 0.239). Neither arch showed a consistent effect on hindfoot alignment. In conclusion, weakness of the TTA has a decisive influence on radiological components of PCFD, but not greater than that of the MLA. Our findings contribute to a deeper understanding and further development of treatment concepts for flatfoot disorders.

Flatfoot is characterized by the collapse of the medial longitudinal arch, eversion of the rearfoot and abduction of the loaded forefoot. Orthopedic insoles are the frequently recommended treatment to support the arch of the foot, adjust the structure of the foot, reduce pain, improve stability and new techniques have been applied to the design of orthopedic insoles in recent years. However, the effectiveness of orthopedic insoles in different motions is still debated from the perspective of biomechanics. Therefore, this study aimed to explore the impact of orthopedic insoles on the kinematics and kinetics of lower limb motion, and to verify effectiveness and propose possible future research directions. We conducted a literature search across three databases employing Boolean operations and filtered results based on eligibility criteria. A total of 671 relevant literature were searched in this review, and 19 literature meeting the requirements were finally included. The results showed that: 1) orthopedic insoles were effective when patients walk, run and jump from the perspective of biomechanics; 2) orthopedic insoles had different result on the change of ankle sagittal angle, moment and peak pressure in the metatarsal region; 3) Whether the effect of insoles, which uses new techniques such as different 3D printed technologies and adds various accessories, can be further improved remains to be further studied; 4) Follow-up studies can pay more attention to the differences between diverse populations, increase the breadth of running and jumping and other movements research and long-term intervention.

BACKGROUND: Subtalar Arthroereisis (STA) is a surgical intervention for pediatric flexible flatfoot (PFF), primarily targeting hindfoot alignment by limiting excessive subtalar eversion. However, its effects on forefoot parameters remain underexplored. This study aims to investigate radiological changes following STA in pediatric patients.
METHODS: A retrospective analysis was conducted on consecutive patients treated with STA for PFF. First ray-related angles, including the Hallux Valgus Angle (HVA) and the Intermetatarsal Angle (IMA), alongside hindfoot radiological parameters such as the Meary, Calcaneal Pitch, and Costa Bartani angles, were assessed. Subgroup analysis by gender was performed, and correlations between demographic and preoperative radiological parameters were examined.
RESULTS: Forty-one patients (81 feet) with an average age of 11.6 years were included, with a mean follow-up duration of 6.4 months. No significant differences were observed in first ray-related angles pre-and postoperatively, with the mean IMA changing from 7.97° to 7.18° and the mean HV angles changing from 9.51° to 8.66°. Noteworthy improvements were seen in flat foot angles, including the Meary, Calcaneal Pitch, and Costa Bartani angles, postoperatively. The age subgroup analysis revealed similar trends in IMA and HVA changes between Group A (who underwent surgery before peak growth) and Group B (who underwent surgery after peak growth). Higher preoperative angles tended to improve, while lower preoperative IMAs and HVAs tended to worsen postoperatively, all remaining within normal ranges.
CONCLUSIONS: STA showed positive radiological outcomes for PFF treatment, while negligible changes in first ray-related angles were observed. The age subgroup analysis indicated similar trends regardless of operation timing. Higher preoperative angles tended to improve, while lower preoperative angles tended to worsen postoperatively, despite all falling within non-pathological ranges. Further research is warranted to confirm this correlation.

Flatfoot is a common foot deformity, causing foot pain, osteoarthritis of the midfoot, and even knee and hip dysfunction. The elastic modulus of foot soft tissues and its association with gait biomechanics still remain unclear. For this study, we recruited 20 young individuals with flatfoot and 22 age-matched individuals with normal foot arches. The elastic modulus of foot soft tissues (posterior tibial tendon, flexor digitorum brevis, plantar fascia, heel fat pad) was obtained via ultrasound elastography. Gait data were acquired using an optical motion capture system. The association between elastic modulus and gait data was analyzed via correlation analysis. The elastic modulus of the plantar fascia (PF) in individuals with flatfoot was higher than that in individuals with normal foot arches. There was no significant difference in the elastic modulus of the posterior tibial tendon (PTT), the flexor digitorum brevis (FDB), or the heel fat pad (HFD), or the thickness of the PF, PTT, FDB, and HFD. Individuals with flatfoot showed greater motion of the hip and pelvis in the coronal plane, longer double-support phase time, and greater maximum hip adduction moment during walking. The elastic modulus of the PF in individuals with flatfoot was positively correlated with the maximum hip extension angle (r = 0.352, p = 0.033) and the maximum hip adduction moment (r = 0.429, p = 0.039). The plantar fascia is an important plantar structure in flatfoot. The alteration of the plantar fascia\'s elastic modulus is likely a significant contributing factor to gait abnormalities in people with flatfoot. More attention should be given to the plantar fascia in the young population with flatfoot.

BACKGROUND: Improvements in muscle oxygenation and exercise posture can significantly impact muscle contraction. The aim of this study was to compare the effects of combined breathing and exercise posture (sitting or standing) on the muscle activity of the foot and ankle during short foot exercises (SFE) in individuals with pes planus.
METHODS: The study included 15 subjects aged 21.53 ± 1.06 years, diagnosed with pes planus. Short foot exercises were performed with and without breathing exercises (BE) in sitting and standing positions. Surface electromyography was used to measure the activity of the tibialis anterior (TA), peroneus longus (PL), and abductor hallucis longus (ABDH) muscles during four different SFE. Four-way repeated analyses of variance were used to assess the addition of BE to SFE and muscle activities of the foot and ankle.
RESULTS: Muscle activity in the TA, PL, and ABDH was significantly higher in the SFE with BE than without BE in the standing position than in the sitting position. The SFE performed with BE when standing significantly increased the ABDH and ankle muscle activity compared to without BE.
CONCLUSIONS: SFE with BE may represent a new strengthening program for ABDH and PL foot muscles in rehabilitation programs for individuals with pes planus.