The rise of the longitudinal arch when sitting, standing, and walking: Contributions of the windlass mechanism

Effects of Plantar Fascia Release and the Use of Foot Orthoses Affect Biomechanics of the Medial Longitudinal Arch of the Foot: A Cadaveric Study

OBJECTIVE

The aim of the study is to evaluate the effect of minimally invasive ultrasound-guided fascial release and a foot orthoses with first metatarsal head cutout on the biomechanics of the medial longitudinal arch of the foot in cadaveric specimens.

DESIGN

A cross-sectional study was designed (20 body donors). Anthropometric measurements of the foot, foot posture index, and the windlass test and force were measured in different conditions: unloaded, loaded position, with foot orthoses, after a 25% plantar fascia release and after a 50% release.

RESULTS

For the anthropometric measurements of the foot, differences were found in foot length ( P = 0.009), arch height ( P < 0.001), and midfoot width ( P = 0.019) when comparing the unloaded versus foot orthoses condition. When foot orthoses were compared with 25% plantar fascial release, differences were found in foot length ( P = 0.014) and arch height ( P < 0.001). In the comparison with 50% plantar fascial release, differences were found in the arch height ( P < 0.001). A significant interaction between foot orthoses condition and grades was found in the arch height during the windlass test ( P = 0.021).

CONCLUSIONS

The results indicate that the presence of foot orthoses leads to a significant increase in arch height compared with other conditions. Furthermore, when plantar fascia release is performed, the arch does not exhibit any signs of collapse.

Effect of using a kinetic wedge during the hallux dorsiflexion resistance test in asymptomatic individuals

BACKGROUND

The hallux dorsiflexion resistance test is a frequently employed clinical maneuver for assessing the initiation of the windlass mechanism This maneuver involves dorsiflexion of the phalanx of the hallux, thereby evaluating plantarflexion of the first metatarsal, elevation of the medial longitudinal arch, and supination of the rearfoot. The windlass mechanism plays a crucial role in gait, and orthopedic devices, such as a kinetic wedge, which aims to facilitate its activation by increasing the hallux dorsiflexion. Although it is believed that facilitating the windlass mechanism with the kinetic wedge should be directly correlated with a decrease in hallux dorsiflexion resistance, its effects have yet to be characterized. Thus, this study aimed to determine the influence of a kinetic wedge on hallux dorsiflexion resistance in asymptomatic individuals.

METHODS

The sample comprised thirty participants (14 women and 16 men). A digital force gauge measured the force required to perform the hallux dorsiflexion resistance test during two conditions: barefoot and with a kinetic wedge. The Wilcoxon signed-rank test was used to compare the hallux dorsiflexion resistance between conditions.

RESULTS

A statistically significant reduction in force (10.54 ± 3.16N vs. 19.62 ± 5.18N, p < 0.001) was observed when using the kinetic wedge compared to the barefoot condition during the hallux dorsiflexion resistance test.

CONCLUSION

The use of a kinetic wedge reduces the required force for performing the passive hallux dorsiflexion resistance test in asymptomatic individuals. Future studies should determine to what extent the kinetic wedge can attenuate the required force to dorsiflex the hallux in individuals with musculoskeletal disorders such as plantar fasciopathy and functional hallux limitus.

Analysis of windlass mechanism according to one walking cycle

[Purpose] This study aimed to calculate the windlass mechanism in one walking cycle (WC) using the medial longitudinal arch (MLA) height and compare its mechanism with joint moments, angles, and center of gravity movement. [Participants and Methods] The study analyzed the gait of 20 healthy adults (14 males, six females) using a three-dimensional motion analyzer to calculate several parameters. [Results] In the terminal stance, the MLA height reached 20.6 ± 6.0 mm (minimum value) at 49% WC. Simultaneously, the ankle dorsiflexion angle, ankle internal plantarflexion moment, and forward shift of the center of gravity reached the maximum values. At 62% WC, the MLA height was 26.8 ± 4.8 mm and reached maximum during the stance phase, indicating a windlass mechanism. Additionally, the MLA height was 61.7 ± 22.7 mm at 69% WC, indicating an MLA spiking phenomenon. [Conclusion] The MLA height was lowest at 49% WC due to reverse windlass mechanism. Although the windlass mechanism was activated at 62% WC, it was functionally equivalent to the swing phase. Push-off was impossible during the swing phase. At 69% WC, the swing phase showed a second windlass mechanism.

The effect of varus rearfoot wedges on hallux dorsiflexion resistance

BACKGROUND

The first metatarsophalangeal joint (MTPJ), which includes the first metatarsal and proximal phalanx, plays a crucial role in gait and impacts the windlass mechanism. Disruptions to this mechanism are implicated in various foot pathologies. Jack's Test serves as a valuable tool for clinicians to assess the functionality of the MTPJ. Varus rearfoot wedges (VRFWs) are a common treatment employed in the management of lower limb pathologies. The impact of VRFWs on the resistance of the first MTPJ during Jack´s Test is currently unknown. This study aimed to measure the influence of VRFWs on the resistance of the first MTPJ during Jack´s Test. The secondary objective was to validate a new measurement method using a digital force gauge.

METHODS

Thirty participants (17 women and 13 men) were enrolled. A digital force gauge measured the weight-bearing force needed for Jack's Test, thereby evaluating the effects of VRFWs of different angulations. The Kolmogorov-Smirnov test confirmed that the data followed a normal distribution (p > 0.05). The nonparametric Friedman test (p < 0.001) showed that there were significant differences among all VRFWs, while the Wilcoxon test (p < 0.001) showed that there were differences between barefoot conditions and 3°, 5°, and 8° VRFWs.

RESULTS

The use of 8° VRFWs yielded a statistically significant reduction in the passive dorsiflexion force of hallux during Jack's Test (12.51 N ± 4.12, p < 0.001).

CONCLUSIONS

The use of VRFWs has been observed to reduce dorsiflexion resistance in the proximal phalanx of the first MTPJ during Jack's Test. Additionally, the digital force gauge was proven to be a valid tool for conducting Jack's Test, thus offering a reliable measurement method.

Chasing footprints in time - reframing our understanding of human foot function in the context of current evidence and emerging insights

In this narrative review we evaluate foundational biomechanical theories of human foot function in light of new data acquired with technology that was not available to early researchers. The formulation and perpetuation of early theories about foot function largely involved scientists who were medically trained with an interest in palaeoanthropology, driven by a desire to understand human foot pathologies. Early observations of people with flat feet and foot pain were analogized to those of our primate ancestors, with the concept of flat feet being a primitive trait, which was a driving influence in early foot biomechanics research. We describe the early emergence of the mobile adaptor-rigid lever theory, which was central to most biomechanical theories of human foot function. Many of these theories attempt to explain how a presumed stiffening behaviour of the foot enables forward propulsion. Interestingly, none of the subsequent theories have been able to explain how the foot stiffens for propulsion. Within this review we highlight the key omission that the mobile adaptor-rigid lever paradigm was never experimentally tested. We show based on current evidence that foot (quasi-)stiffness does not actually increase prior to, nor during propulsion. Based on current evidence, it is clear that the mechanical function of the foot is highly versatile. This function is adaptively controlled by the central nervous system to allow the foot to meet the wide variety of demands necessary for human locomotion. Importantly, it seems that substantial joint mobility is essential for this function. We suggest refraining from using simple, mechanical analogies to explain holistic foot function. We urge the scientific community to abandon the long-held mobile adaptor-rigid lever paradigm, and instead to acknowledge the versatile and non-linear mechanical behaviour of a foot that is adapted to meet constantly varying locomotory demands.

A Bio-Inspired Arched Foot with Individual Toe Joints and Plantar Fascia

This paper presents the design and testing of an arched foot with several biomimetic features, including five individual MTP (toe) joints, four individual midfoot joints, and plantar fascia. The creation of a triple-arched foot represents a step further in bio-inspired design compared to other published designs. The arched structure creates flexibility that is similar to human feet with a vertical deflection of up to 12 mm. The individual toe joints enable abduction-adduction in the forefoot and therefore a natural pronation motion. Adult female bone data was obtained and converted into a CAD model to accurately identify the location of bones, joints, and arches. An analytical model is presented that gives the relationship between the vertical stiffness and horizontal stiffness of the longitudinal arches and therefore allows the optimization of stiffness elements. Experimental tests have demonstrated a vertical arch stiffness of 76 N/mm which is similar to adult human feet. The range of movement of the foot is similar to human feet with the following values: dorsi-plantarflexion (28°/37°), inversion-eversion (30°/15°), and abduction-adduction (30°/39°). Tests have also demonstrated a three-point contact with the ground that is similar to human feet.

Kinetic coupling in distal foot joints during walking

BACKGROUND

Kinematic coupling between the first metatarsophalangeal (MTP) and midtarsal joints is evident during gait and other movement tasks, however kinetic foot coupling during walking has not been examined. Furthermore, contributing factors to foot coupling are still unclear. Therefore, the purpose of this study was to investigate kinematic and kinetic coupling within the foot by restricting MTP motion during overground walking. We hypothesized that when the MTP joint was prevented from fully extending, the midtarsal joint would achieve less peak motion and generate less positive work compared to walking with normal MTP motion.

METHODS

Twenty-six individuals participated in this randomized cross-over study. Using motion capture to track motion, participants walked at 1.3 m/s while wearing a brace that restricted MTP motion in a neutral (BR_NT) or extended (BR_EX) position. Additionally, participants walked while wearing the brace in a freely moveable setting (BR_UN) and with no brace (CON). A pressure/shear sensing device was used to capture forces under each foot segment. During stance, peak joint motion and work were calculated for the MTP and midtarsal joints using inverse dynamics. A series of ANOVAs and Holm post hoc tests were performed for all metrics (alpha = 0.05).

RESULTS

The brace successfully decreased peak MTP motion by 19% compared to BR_UN and CON. This was coupled with 9.8% less midtarsal motion. Kinetically, the work absorbed by the MTP joint (26-51%) and generated by the midtarsal joint (30-38%) were both less in BR_EX and BR_NT compared to BR_UN.

CONCLUSION

Implications and sources of coupling between the MTP and midtarsal joints are discussed within the context of center of pressure shifts and changes to segmental foot forces. Our results suggest that interventions aimed at modulating MTP negative work (such as footwear or assistive device design) should not ignore the midtarsal joint.

Three-Dimensional Analysis of the Windlass Mechanism Using Weightbearing Computed Tomography in Healthy Volunteers

BACKGROUND

The windlass mechanism (WM) increases the longitudinal arch of the foot via tension of the plantar aponeurosis during dorsiflexion of the metatarsophalangeal (MTP) joint. The purpose of this study was to perform a 3-dimensional evaluation of the displacement of each joint and the height of the navicular during dorsiflexion of the first MTP joint by using weightbearing computed tomography (CT).

METHODS

Participants were 6 men and 8 women with 23 healthy feet. CT of the foot with a load equivalent to the participant's body weight was performed. The first MTP joint was in the neutral position and dorsiflexed 30 degrees. Between the conditions, we measured the (1) rotation of each bone, (2) rotation of the distal bone with respect to the proximal bone at each joint, and (3) height of the navicular.

RESULTS

With respect to the tibia, the calcaneus was at 0.8 ± 0.7 degrees dorsiflexion and 1.4 ± 0.9 degrees inversion, while the talus was at 2.0 ± 1.2 degrees dorsiflexion and 0.1 ± 0.8 degrees eversion. The navicular was at 1.3 ± 1.2 degrees dorsiflexion and 3.2 ± 2.1 degrees inversion, whereas the medial cuneiform was at 0.3 ± 0.6 degrees plantarflexion and 1.3 ± 1.1 degrees inversion. At the talonavicular joint, the navicular was at 0.7 ± 1.3 degrees plantarflexion, whereas at the cuneonavicular joint, the medial cuneiform bone was at 1.4 ± 1.4 degrees plantarflexion. The height of the navicular increased by 1.1 ± 0.6 mm.

CONCLUSION

We 3-dimensionally confirmed the dynamics of WM and found that the calcaneus, navicular, and medial cuneiform moved in all 3 planes. The results suggest that the cuneonavicular joint has the greatest movement among the joints. We believe that these findings will help to elucidate the pathogenesis of WM-related diseases and lead to advances in treatments for pathologies involving the longitudinal arch.

LEVEL OF EVIDENCE

Level IV, case series.

An exploratory study of dynamic foot shape measurements with 4D scanning system

Accurate and reliable foot measurements at different stances offer comprehensive geometrical information on foot, thus enabling a more comfortable insole/footwear for practical use and daily activities. However, there lacks investigations on continuous deformation of foot shape during the roll-over process. This study analyses the foot deformation of 19 female diabetic patients during half weight bearing standing and self-selected walking speed by using a novel 4D foot scanning system. The scanning system has good repeatability and accuracy in both static and dynamic scanning situations. Point cloud registration for scanned image reorientation and algorithms to automatically extract foot measurements is developed. During the foot roll-over process, maximum deformation of length and girth dimensions are found at first toe contact. Width dimensions have maximum deformation at heel take off. The findings provide a new understanding of foot shape changes in dynamic situations, thus providing an optimal solution for foot comfort, function and protection.

Using surface markers to describe the kinematics of the medial longitudinal arch

BACKGROUND

Static and dynamic assessment of the medial longitudinal arch (MLA) is an essential aspect for measuring foot function in both clinical and research fields. Despite this, most multi-segment foot models lack the ability to directly track the MLA. This study aimed to assess various methods of MLA assessment, through motion capture of surface markers on the foot during various activities.

METHODS

Thirty general population participants (mean age 20 years) without morphological alterations to their feet underwent gait analysis. Eight measures, each representing a unique definition of the MLA angle using either real only, or both real and floor-projected markers, were created. Participants performed tasks including standing, sitting, heel lift, Jack's test and walking, and had their Arch Height Index (AHI) measured using callipers. Multiple-criteria decision analysis (MCDA) with 10 criteria was utilised for selecting the optimal measure for dynamic and static MLA assessment.

RESULTS

In static tasks, the standing MLA angle was significantly greater in all measures but one when compared to sitting, Jack's test and heel lift. The MLA angle in Jack's test was significantly greater than in heel lift in all measures. Across the compared dynamic tasks, significant differences were noted in all measures except one for foot strike in comparison to 50% gait cycle. All MLA measures held significant inverse correlations with MLA measured from static and dynamic tasks. Based on MCDA criteria, a measure comprising the first metatarsal head, fifth metatarsal base, navicular and heel markers was deemed the best for MLA assessment.

SIGNIFICANCE

This study aligns with the current literature recommendations for the use of a navicular marker for characterising the MLA. It contrasts with previous recommendations and advocates against the use of projected markers in most situations.

Foot shape is related to load-induced shape deformations, but neither are good predictors of plantar soft tissue stiffness

Modern human feet are considered unique among primates in their capacity to transmit propulsive forces and re-use elastic energy. Considered central to both these capabilities are their arched configuration and the plantar aponeurosis (PA). However, recent evidence has shown that their interactions are not as simple as proposed by the theoretical and mechanical models that established their significance. Using three-dimensional foot scans and statistical shape and deformation modelling, we show that the shape of the longitudinal and transverse arches varies widely among the healthy adult population, and that the former is subject to load-induced arch flattening, whereas the latter is not. However, longitudinal arch shape and flattening are only one of the various foot shape-deformation relationships. PA stiffness was also found to vary widely. Yet only a small amount of this variability (approx. 10-18%) was explained by variations in foot shape, deformation and their combination. These findings add to the mounting evidence showing that foot mechanics are complex and cannot be accurately represented by simple models. Especially the interactions between longitudinal arch and PA appear to be far less constrained than originally proposed, most likely due to the many degrees of freedom provided by the structural complexity of our feet.

Immunopathogenesis, early Detection, current therapies and prevention of plantar Fasciitis: A concise review

Plantar fasciitis or the inflammation of the fascial lining on the plantar aspect of the foot continues to be the leading cause of heel pain for many Americans. Common causes can range from anatomical deformities such as pes planus or flat foot, biomechanical etiology such as excessive pronation of the subtalar joint, or chronic diseases such as obesity and diabetes mellitus. The pathophysiology of plantar fasciitis can be either inflammatory due to vasodilation and immune system activation or non-inflammatory involving fibroblastic hypertrophy. Worsening pain of the inferior and medial heel after periods of prolonged rest and late in the day after hours of ambulation and weight-bearing activities is the most common symptom of plantar fasciitis. Common treatments for plantar fasciitis include plantar fascia stretching, physical therapy, orthotics, corticosteroid injections, and even surgery. Despite these treatment strategies, fasciitis remains a clinical problem and better treatment modalities are warranted. Late diagnosis is a common issue for prolonged and equivocal treatment and early diagnostic measures might be beneficial. In this concise review, we discussed the etiology, immunopathogenesis, current treatments of plantar fasciitis and potentially preventative measures prior to the onset of chronic treatment resistant condition.

Contributions of Intrinsic and Extrinsic Foot Muscles during Functional Standing Postures

Purpose. Maintaining balance during static standing postures requires the coordination of many neuromuscular mechanisms. The role of the intrinsic and extrinsic foot muscles in this paradigm has yet to be clearly defined. The purpose of this study was to explore foot muscle activation during static phases on common weight-bearing tasks of varying loads and balance demands. Methods. Twenty healthy young adults performed 6 standing postures (single-limb and double-limb stand, squat, and heel raise) with one foot on a force plate. Muscle activity was recorded from the abductor hallucis, flexor hallucis longus and brevis, and tibialis posterior using intramuscular electrodes; surface electrodes were used to record activity from the peroneus longus and tibialis anterior. Two-way repeated measures ANOVA (2 loading conditions × 3 postures) were run to compare muscle activation and center of pressure velocity. Results. Intrinsic foot muscle activity increased as loading and postural demand increased; however, the specific effects varied for each of the extrinsic foot muscles. Conclusions. These results suggest that the intrinsic foot muscles play an important role in maintaining static balance. Strengthening intrinsic and extrinsic foot muscles may help increase stability in people who have weak toe flexors or who suffer from a variety of foot pathologies.

The influence of the windlass mechanism on kinematic and kinetic foot joint coupling

Background

Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study’s purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements.

Methods

After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics.

Results

Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling.

Conclusions

Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13047-022-00520-z.