Effect of the dorsiflexion and plantarflexion angles of the foot on the fifth metatarsal bone: finite element analysis

Introduction

The foot is a complex system with multiple degrees of freedom that plays an essential role in sports. Healthy foot posture and function are essential for improving athletic performance and potential. This is because, during sports, stress levels in the feet, knees, and lower body are intensely high. A weak foot posture can further increase this stress, increasing the risk of developing conditions such as plantar fasciitis, Achilles tendonitis, knee injuries, or even fractures. Of the injuries that occur, stress fractures have a variable incidence ranging from 1% to 20%, considering common injuries in the athlete population (1-3).

A fifth metatarsal fracture is a common bone injury to the foot, which occurs when the fifth metatarsal bone is broken. It is an injury that can occur in people of all ages and levels of physical activity and can be caused by a variety of factors, such as direct trauma to the foot, a sprain, or a fall. This injury is classified based on the location of the fracture. In sports, this injury is quite common, especially in athletes who play high-impact sports that involve sudden changes of direction and repetitive movements of the foot, such as football, basketball, track and field, martial arts, and rugby (4). The incidence of this fracture varies depending on the sport and the age of the athletes. In recent studies, fracture of the fifth metatarsal accounts for 10% of all sports injuries and 25% of foot injuries, with a higher incidence in men than women, and occurring more frequently in the dominant leg (5,6).

In addition, soccer is one of the most practiced sports with the highest risk of injury. Most injuries are registered in the lower extremities; the incidence of injuries is from 2 to 9.4 per 1,000 hours of exposure, with a predominance of sprains, fractures, muscle strains, ligament tears, meniscus affectations, and contusions. Some authors conclude that injuries have a significant influence on the performance of athletes during men’s professional football league and cup competitions, making even more evident the need to carry out surveillance studies to identify the factors associated with the occurrence of injuries, especially in the musculoskeletal system (7-9).

Some authors have carried out research and surveillance studies to identify the prevalence of injuries in the musculoskeletal system. Proof of this is what was reported by Bjorneboe et al. (10), where they identified the risks associated with training for the appearance of injuries. On the other hand, authors such as Larruskain et al. (11) carried out a comparison of injuries in male and female professional soccer players to establish the differences between both groups. This makes it clear that the area of injury prevention has a lot of research potential, and it is necessary to continue conducting research in order to identify the associated factors and to be able to establish focused training sessions that minimize the risk of injury in the season. In addition, different studies have found that the morphology or type of foot could alter the distribution of plantar pressure, which would condition the increase of stress in different regions of the foot (12,13). The repetition of the technical gesture in football involves the appearance of loads on specific joint areas and muscle groups, being an important factor in the appearance of stress injuries due to the combination of anatomical, hormonal, and biomechanical factors (10,11,14,15).

In the case of stress injuries, metatarsal fractures, regardless of whether they are caused by chronic stress, low-energy trauma, or both, are the most common foot injury, particularly in young athletes with an estimated incidence of 1.8 per thousand individuals per year, in those with varus of the foot. Currently, the fracture of the fifth metatarsal continues to be a topic of interest for researchers; this is because it has not been possible to identify the causes or risk factors that can produce this fracture (16,17).

The fracture of the fifth metatarsal is a common injury in athletes; in many cases, it is associated with a sports gesture. Studies have shown that the sports gesture most associated with the fracture is the sudden change of direction in sports such as football, basketball, and volleyball. Athletes with flat feet are at a higher risk of this injury due to an increased load on the outside of the foot. A higher incidence has also been found in athletes with inadequate running technique, such as an excessive pronation pattern (18). However, there are no conclusive studies that can be directly related to a group of people before and after the fracture of the fifth metatarsal. This is because longitudinal prospective studies are required in most cases. This requires establishing follow-up with participants for extended periods. However, one of the important risks of these studies is the discontinuity or dropout of the participants, so the studies can hardly be carried out. One of the tools that can help determine risk factors without putting the physical integrity of athletes at risk is computer numerical simulation. A useful tool capable of modeling different scenarios of foot loading, without putting the physical integrity of the participant at risk.

This study aims to obtain a three-dimensional (3D) model of the foot from a computed tomography (CT) scan that allows numerical simulations to be carried out to evaluate the effect and variation of tensions in the area of the fifth metatarsal and, consequently, find the most relevant cases that can be considered as risk factors for this type of injury.

Methods

Model description and mesh characteristics

The 3D geometry of the foot was reconstructed from CT scans of an adult male subject. The data were obtained from the Universidade da Coruña. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of research from the Universidade da Coruña (No. 2019-0017) in November 2019. Informed consent was not required as the participant was not involved in the measurements. The CT images were processed using 3D Slicer software to segment and extract the cortical and trabecular bone structures. These structures were exported in STL (stereolithography) format and later smoothed and converted into solid geometries using Autodesk Fusion 360. The final geometry, composed of 106 components (28 cortical bones, 28 trabecular bones, and 50 cartilage segments), was imported into ANSYS in IGES (Initial Graphics Exchange Specification) format for finite element simulation.

Figure 1 shows CT scans of the foot in 3D-Slicer software (version 4.11.20200930 R29402/002BE18). Different masks were created for each cortical and trabecular bone. Cartilage was created from cortical bones. The thickness of the CT scans was 2.5 mm. The bones are modeled in STL format. This format does not allow you to run finite element simulations, as they are shell elements. Next, it is necessary to export the bone geometries to Autodesk Fusion 360 software. There, the bones and cartilage are smoothed and become solid parts. Once the bones are smoothed and transformed into solid geometries, they are imported into ANSYS software in IGES format.

Figure 1 Foot image segmentation in 3D Slicer software. 3D, three-dimensional.

The final geometry of the foot is presented in Figure 2. From this figure, it is clear to see each bone and cartilage assembled. The final model of the foot consists of 106 parts, 28 cortical bones, 28 trabecular bones, and 50 cartilages that make up the total structure of the foot.

Figure 2 Final foot geometry: cortical bones, trabecular bones, and cartilage.

To ensure computational efficiency and accuracy, a mesh sensitivity analysis was conducted. Element sizes ranging from 10 mm to 1 mm were tested (Figure 3). The final model used a high-resolution tetrahedral mesh with 1,456,251 elements and 2,607,963 nodes, offering a mesh resolution of 1 mm. The mesh quality was deemed acceptable, with an error margin below 6% balancing precision and computational cost.

Figure 3 Foot mesh sensitivity analysis: element size from 10 mm to 1 mm.

In Figure 4, the average stress is presented with the different number of elements that are in the foot after being meshed. After a sensitivity analysis of the model mesh, a high-resolution mesh composed of 1,456,251 elements and 2,607,963 nodes was used. This tetrahedral mesh offers a resolution of 1 mm, allowing for a more detailed and accurate approximation of the model simulation. The error difference was less than 6%, an acceptable margin of error in relation to the calculation time, since a finer mesh tends to exponentially increase the simulation solution time.

Figure 4 Mesh sensitivity analysis.

Tissues’ modeling and conditions

The foot model included three types of tissues: cortical bone, trabecular bone, and cartilage. Material properties for each tissue were assigned based on literature values and are summarized in Table 1. Cortical and trabecular bones were modeled using isotropic, homogeneous, linear elastic properties, with cortical bone exhibiting the highest stiffness (Young’s modulus =17,000 MPa). Cartilage was modeled with a lower modulus (12 MPa) and a higher Poisson’s ratio (0.4) to reflect its viscoelastic behavior under compression.

Each tissue was modeled as a solid element, and anatomical assemblies were constructed to maintain structural continuity. Cartilage layers were created from the smoothed cortical bone surface to simulate joint interfaces. All components were assumed to be perfectly bonded, without sliding or separation, simulating rigid anatomical articulation.

Boundary and loading conditions

Boundary conditions were applied by fully constraining the calcaneus and the first and fifth metatarsal heads in all degrees of freedom, simulating the foot’s stable contact points during loading. This assumption was made based on the classical biomechanical representation of the foot as a complex structural system forming a plantar vault supported by three primary load-bearing regions: the calcaneus, the head of the first metatarsal, and the head of the fifth metatarsal. These three points constitute the so-called tripod support of the foot and are commonly used in simplified biomechanical and finite element models to represent ground contact during stance and impact conditions (19). The load of 1,926.19 Newton (N) was selected to represent the peak vertical ground reaction force transmitted through the tibia during a unilateral landing task. This force was estimated based on preliminary biomechanical observations from a countermovement jump task, and it was applied to the tibia to approximate impact loading during high-intensity sport maneuvers. This value corresponds to approximately 2.8–3.0 times body weight for a subject with a mass of ≈70 kg. The angle of joint motion of the ankle is shown in Figure 5, which was obtained from a previous experiment with the motion capture technique. In the figure, it can be seen that the angle of joint movement ranges between 0 and 20° for dorsiflexion and between 0 and 30° for plantar flexion.

Figure 5 Ankle joint range of motion (dorsiflexion and plantarflexion).

Six different load conditions were then established in the simulation (Figure 6). The load rotated in the sagittal plane (Z and Y axes) of the foot, starting at 40 degrees. This posture was considered the most critical scenario (I1) for the forefoot region. The least critical scenario for the forefoot was when the load was applied vertically, on the z-axis (I6). Rotation represents the dorsal and plantar flexion of the foot. This rotation will produce a concentration of stress in the metatarsal bones.

Figure 6 Foot load and boundary conditions.

The load vector was rotated in the sagittal plane across six angles (40° to 90°) as shown in Table 2, to represent varying degrees of dorsiflexion and plantar flexion. In addition, the magnitude of the load (1,926.19 N) was decomposed in the Y and Z axes. Contact conditions between cartilage elements were defined using junction constraints to replicate anatomical interactions during joint movement.

About model validation

Model validation was performed through a qualitative comparison of the stress distribution patterns obtained in the present finite element model with previously published finite element studies and experimentally reported plantar pressure distributions. The stress concentration observed in the first and fifth metatarsals across all loading conditions is consistent with earlier finite element investigations analyzing forefoot loading during sports-related movements. Gu et al. reported increased stress levels in the metatarsal region during inclined landing conditions, particularly under dorsiflexion and inversion postures, which are comparable to the loading scenarios simulated in the present study (20). Similarly, Li et al. demonstrated that forefoot-dominant loading patterns result in higher stress concentrations in the metatarsals, supporting the trends observed in our simulations (21).

Moreover, finite element studies specifically focused on the fifth metatarsal have reported elevated stress levels in this bone under non-neutral loading conditions, reinforcing the relevance of the stress magnitudes and spatial distributions observed in the current model (22,23). In addition, the lateralized stress distribution identified in the fifth metatarsal agrees with plantar pressure studies conducted in athletic populations. Experimental investigations using plantar pressure analysis have consistently reported higher pressure values in the lateral forefoot region, particularly in soccer players with a history of proximal fifth metatarsal fractures (24,25). These findings support the biomechanical plausibility of the stress patterns predicted by the present finite element model.

Although direct experimental validation using subject-specific plantar pressure or in vivo strain measurements was beyond the scope of this study, the consistency between the present numerical results and previously reported computational and experimental evidence supports the validity of the proposed finite element model for analyzing stress behavior in the fifth metatarsal under varying ankle kinematic conditions.

Simulation and evaluation criteria

The simulation was conducted using ANSYS software with transient static analysis settings. Each scenario simulated a different angle of load application corresponding to dorsiflexion and plantar flexion postures, with six iterations in total. The primary evaluation criteria included von Mises stress (MPa) in the fifth metatarsal bone, strain (mm/mm), and deformation (mm) in the same region, overall stress distribution across the entire foot model, and displacement and deformation of the global structure. The results were analyzed to identify the iteration with the highest critical stress and strain in the fifth metatarsal bone, which was used as a reference for determining injury conditions.

Results

In Figure 7, it can be observed that the first and fifth metatarsal bones have a higher concentration of stress than the other bones. From a mechanical point of view, this behavior makes sense since the first and fifth metatarsal bones are two of the main supports of the forefoot. This pattern can be observed under different loading conditions (different angles of dorsiflexion and plantar flexion). The stress exerted on the standing bone structure, on average, is 2.10 MPa, where the maximum stress point is 1,971.80 MPa located in the tibial part of the model. On the other hand, the minimum stress 1.96E−10 MPa is located in the distal phalanx of the first toe. The average displacement was 135.34 mm, and the average deformation of the structure was 2.14E−2 mm/mm. The results are shown in greater detail in Table 3.

Figure 7 Stress and strain results for each iteration performed according to the angle of dorsiflexion and plantar flexion of the foot. (A) Model with defined boundary conditions. (B) Resulting stress patterns. (C) Resulting strain patterns obtained from each iteration performed at varying foot dorsiflexion and plantarflexion angles.

From the results obtained, Figures 7,8 show the stress distribution and the strain of the foot for the six different load conditions.

Figure 8 Stress behavior in the fifth metatarsal bone as a function of angular load variation.

Discussion

The objective of this study was to determine the effect produced by the application of the load on the foot under different conditions or degrees of inclination; this was to simulate the conditions of dorsiflexion and plantar flexion of the foot. The load conditions and the degrees of application were obtained from a preliminary study of countermovement jump, where the reaction forces in participants under different conditions were measured. Through numerical simulation, it is possible to have a model that emulates the technical gesture of jumping. This is a critical condition of the technical gesture that is present in some sports, such as soccer, where similar maneuvers occur, and which are the ones in which the greatest reports of this type of injury have been presented (24,25).

The results found in this research are consistent with the results found by Shudong Li [2017] and Gu Y. [2010], who found that the metatarsals are the region most stressed during the stance phase (20,21). Although different research has been carried out to determine which are the critical conditions that lead to the fracture of the fifth metatarsal bone, it is still not clear which are the ones that contribute most to this phenomenon. This may be because the fracture of the fifth metatarsal bone is an event that occurs under the interaction of different variables, such as the technical gesture executed, the anthropometry of the athlete, the load applied, the type of footwear used, among others (20-23).

In this study, it was found that the most critical condition, where the fifth metatarsal bone is most stressed, is when the foot is in dorsiflexion at 60° concerning the horizontal plane (I3, 3.18 MPa), and the least critical is when the foot is in a neutral position (I6, 0.66 MPa).

This work has several limitations that should be acknowledged. First, caution is required when generalizing the results, as the analysis focused exclusively on the effect of the inclination angle of the applied force at the foot joint. Other biomechanical factors that may significantly influence stress distribution, such as dynamic loading conditions, interindividual anatomical variability, and neuromuscular control, were not considered. Future studies should therefore incorporate different foot morphologies and pathological conditions, including flat feet, cavus feet, pronated and supinated feet, hallux valgus, claw toes, and varus heel alignment, in order to enhance the clinical relevance of the findings.

Second, the computational numerical model represents an idealized configuration and does not include several key anatomical structures involved in force transmission, such as ligaments, tendons, muscles, the plantar fascia, and surrounding soft tissues. Consequently, the results reflect isolated bone-cartilage loading conditions and cannot be directly extrapolated to real physiological or in vivo scenarios. The absence of these structures may affect load redistribution mechanisms and joint stability, potentially altering stress magnitudes and patterns. Future work will focus on developing a more comprehensive biomechanical model that integrates soft tissues and active muscular contributions to more accurately replicate physiological foot mechanics. Although the present computational numerical model has some limitations, it can be observed that the anterior region of the foot, especially the first and fifth metatarsal bones, is the most stressed region. This is mainly because they are the two main points of support for the plantar vault in the anterior part of the foot.

Conclusions

The present computational numerical simulation model of the foot allows us to conclude that one of the critical or risk conditions for the metatarsal region may be when the foot is in dorsiflexion movement. That is, during the movement of the jump, in the landing phase, the metatarsal region is subjected to extreme load conditions that make it a vulnerable part of a fracture or injury. Therefore, all those sports activities that require this sporting gesture must be executed with extreme caution.

Acknowledgments

We would like to thank the Centro de Innonvación Aplicada en Tecnologías Competitivas (CIATEC) and the Universidade da Coruña for supporting the postgraduate student involved in the research.

Footnote

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1744/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1744/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Ethics Committee of research from the Universidade da Coruña (No. 2019-0017) in November 2019. Informed consent was not required as the participant was not involved in the measurements.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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