Human in vivo midtarsal and subtalar joint kinematics during walking, running and hopping.

The interaction among joints of the midtarsal complex and subtalar joint is important for locomotor function; however, its complexity poses substantial challenges in quantifying the joints' motions. We determine the mobility of these joints across locomotion tasks and investigate the influence of individual talus morphology on their motion. Using highly accurate biplanar videoradiography, three-dimensional bone kinematics were captured during walking, running and hopping. We calculated the axis of rotation of the midtarsal complex and subtalar joint for the landing and push-off phases. A comparison was made between these rotation axes and the morphological subtalar axis. Measurement included total rotation about and the orientation of the rotation axes in the direction of the subtalar joint and its deviation via spatial angles for both phases. The rotation axes of all three bones relative to the talus closely align with the morphological subtalar axis. This suggests that the midtarsal and subtalar joints' motions might be described by one commonly oriented axis. Despite having such an axis, the location of the axes and ranges of motion differed among the bones. Our results provide a novel perspective of healthy foot function across different sagittal plane-dominant locomotion tasks underscoring the importance of quantifying midtarsal complex and subtalar motion while accounting for an individual's talus morphology.

Influence of Talar and Calcaneal Morphology on Subtalar Kinematics During Walking.

BACKGROUND: Cadaver biomechanical testing suggests that the morphology of articulating bones contributes to the stability of the joints and determines their kinematics; however, there are no studies examining the correlation between bone morphology and kinematics of the subtalar joint. The purpose of this study was to investigate the influence of talar and calcaneal morphology on subtalar kinematics during walking in healthy individuals. METHODS: Forty ankles (20 healthy subjects, 10 women/10 men) were included. Participants walked at a self-selected pace while synchronized biplane radiographs of the hindfoot were acquired at 100 images per second during stance. Motion of the talus and calcaneus was tracked using a validated volumetric model-based tracking process, and subtalar kinematics were calculated. Talar and calcaneal morphology were evaluated using statistical shape modeling. Pearson correlation coefficients were used to assess the relationship between subtalar kinematics and the morphology features of the talus and calcaneus. RESULTS: This study found that a shallower posterior facet of the talus was correlated with the subtalar joint being in more dorsiflexion, more inversion, and more internal rotation, and higher curvature in the posterior facet was correlated with more inversion and eversion range of motion during stance. In the calcaneus, a gentler slope of the middle facet was correlated with greater subtalar inversion. CONCLUSION: The morphology of the posterior facet of the talus was found to a primary factor driving multiplanar subtalar joint kinematics during the stance phase of gait. CLINICAL RELEVANCE: This new knowledge relating form and function in the hindfoot may assist in identifying individuals susceptible to subtalar instability and in improving implant design to achieve desired kinematics after surgery.

Difference in orientation of the talar articular facets between healthy ankle joints and ankle joints with chronic instability.

Since both the talocrural and subtalar joints can be involved in chronic ankle instability, the present study assessed the talar morphology as this bone is the key player between both joint levels. The 3D orientation and curvature of the superior and the posteroinferior facet between subjects with chronic ankle instability and healthy controls were compared. Hereto, the talus was segmented in the computed tomography images of a control group and a chronic ankle instability group, after which they were reconstructed to 3D surface models. A cylinder was fitted to the subchondral articulating surfaces. The axis of a cylinder represented the facet orientation, which was expressed by an inclination and deviation angle in a coordinate system based on the cylinder of the superior talar facet and the geometric principal axes of the subject's talus. The curvature of the surface was expressed as the radius of the cylinder. The results demonstrated no significant differences in the radius or deviation angle. However, the inclination angle of the posteroinferior talar facet was significantly more plantarly orientated (by 3.5°) in the chronic instability group (14.7 ± 3.1°) compared to the control group (11.2 ± 4.9°) (p < 0.05). In the coronal plane this corresponds to a valgus orientation of the posteroinferior talar facet relative to the talar dome. In conclusion, a more plantarly and valgus orientated posteroinferior talar facet may be associated to chronic ankle instability.

Footloose: Articular surface morphology and joint movement potential in the ankles of lorisids and cheirogaleids.

OBJECTIVES: The competing functional demands of diarthrodial joints, permitting mobility while retaining enough stability to transmit forces across the joint, have been linked with the shape and size of the joint's articular surfaces. A clear understanding of the relationship between joint morphology and joint movement potential is important for reconstructing locomotor behaviors in fossil taxa. METHODS: In a sample of matched tali and calcanei of lorisids (n = 28) and cheirogaleids (n = 38), we quantify the surface areas of the talar and calcaneal ectal (=posterior talocalcaneal) articular surfaces and model the principal curvatures of these surfaces with quadric formulas. These two taxonomic groups have similar body masses, but differ substantially in positional behavior, so that differences in joint surface morphology should reflect adaptive demands of their locomotor behavior. RESULTS: Compared with cheirogaleids, lorisids exhibit: (a) a significantly greater area difference between their paired joint surfaces; and (b) a more pronounced saddle shape for the talar ectal facet. CONCLUSION: The increased subtalar joint mobility observed in lorisids may be achieved by increasing the amount of sliding and rolling that can occur at the subtalar joint. The subtalar joint morphology observed in two fossil euarchontans, the plesiadapiforms Purgatorius sp. and Plesiadapis cookei, compares favorably with the morphology observed among lorisids, potentially suggesting antipronograde postures within these extinct taxa.

The posterior talocalcaneal ligament: an MRI evaluation.

PURPOSE: A wide inter-individual variability in terms of size, orientation and insertion is observed regarding ankle ligaments. The aim of this study is to identify and describe the anatomical features of the posterior talocalcaneal ligament (PTCL) observed through the use of magnetic resonance imaging (MRI) of the ankle. METHODS: The study was retrospectively carried out on 893 ankle MRI's exams. The exams have all been performed using a 1.5-T (T) MRI. The same scanning protocols and scan planes were carried out in all the exams. The first evaluated parameter was the recognition of the PTCL. Subsequently, in all those cases where the ligament was present, its features such as insertion sites, length, and thickness were evaluated. RESULTS: The PTCL identification was possible in 77 exams (8.6% of the total number). Among these, we were able to identify some variants regarding insertion sites, length, and thickness. The PTCL could be further classified into four categories based on the most common characteristics observed. CONCLUSIONS: Our study has identified different characteristics of the PTCL that allow us to further understand the characteristics of the ligament itself. In conclusion, the need for further studies focused on the biomechanical role of the PTCL in the ankle joint appears mandatory.

The Influence of Radiograph Obliquity on Böhler's and Gissane's Angles in Calcanei.

In calcaneal fractures, Böhler's and Gissane's angles are considered important parameters to guide treatment strategy and provide prognostic information during follow-up visits. Therefore, lateral radiographs have to be accurate. The aim of this study was to evaluate the effect of craniocaudal and posteroanterior angular variations (i.e., simulate lower leg malposition) from the true lateral radiograph on Böhler's and Gissane's angles. In this radioanatomical study, 15 embalmed, skeletally mature, human anatomic lower limb specimens were used. Using predefined criteria, a true lateral radiograph (i.e., 0° angular variation) was obtained. Angular variations from this true lateral radiograph were made from -30° to +30° deviation in the craniocaudal and posteroanterior direction at 5° intervals. Böhler's and Gissane angles were independently assessed by 2 experienced trauma surgeons. Böhler's angle decreased with increasing caudal angular variations (maximum -4.3° deviation at -30°). With increasing of the posterior angular variations, Böhler's angle increased (maximum 5.0° deviation at +30°) from the true lateral radiograph, but all deviations were within the measurement error. The deviation of the angle of Gissane was most pronounced in the cranial direction, with the mean angle decreasing by -8.8° at +30° angular variation. Varying angular obliquity in the caudal and posteroanterior direction hardly affected Gissane's angle. Foot malpositioning during the making of a lateral radiograph has little influence on Böhler's and Gissane's angles. If used for clinical decision-making in initial treatment and during follow-up of calcaneal fractures, these parameters can reliably be obtained from any lateral radiograph.

Bilateral symmetry of the subtalar joint facets and the relationship between the morphology and osteoarthritic changes.

There is a paucity in the literature regarding bilateral symmetry between the facets of the subtalar joint. Often surgeons use the contralateral side as a reference when dealing with a fracture or other joint pathology. Moreover, the presence of osteoarthritic (OA) changes in the subtalar joint is suggested to have a relation with its morphology. In this study, we addressed both these issues. Forty pairs of cadaveric tali and calcanei were analyzed by dissection and measurement. Twenty pairs of asymptomatic calcanei were morphologically analyzed by computer tomography imaging. In the cadaveric feet, the length and width of the facets, the number and interfacet connections, the intersection angle, and the presence of OA changes were registered. In the healthy feet, the orientation and curvature of the posterior facet were analyzed based on cylinder fittings. Bilateral symmetry was tested with paired Student's t tests. Significant associations between morphometric parameters and the presence of OA changes were tested with generalized estimating equation logistic regression models. The morphometric data demonstrated a high degree of bilateral symmetry. The types of tali and calcanei between left and right differed in about one-fifth of the individuals. No significant interactions were found between morphological parameters and the presence of OA changes. Only age had a significant association. There was a high degree of symmetry in the subtalar joints facets. No significant associations were found between OA changes and morphological features, whereas other studies did. Further research is needed to explore this relationship in further detail. Clin. Anat., 33:997-1006, 2020. © 2019 Wiley Periodicals, Inc.

Morphological features of the cervical ligament.

PURPOSE: The purpose of this study was to clarify the morphological characteristics of the cervical ligament (CL). METHODS: This study examined 80 legs from 40 Japanese cadavers. The CL was classified by the number of fiber bundles. The morphological features measured were fiber bundle length, width, thickness, and angle with the sagittal plane. RESULTS: The CL was classified as follows: Type I, the CL is a single fiber; Type II, the CL consists of a superficial fiber and an inferior fiber; and Type III, the CL consists of a superficial fiber, intermediate fiber, and inferior fiber. Type I was seen in 15 feet, Type II in 57 feet, and Type III in 8 feet. In comparisons of morphological features within each type, significant differences were seen in fiber bundle length, width, and angle between superior fiber bundles and inferior fiber bundles of Type II and Type III. In comparison among types, the total fiber bundle width was significantly wider in Type II and Type III than in Type I, and the angle was significantly smaller in Type III than in Type I. CONCLUSION: The results of this study suggested that each type may have different sub-talar joint control functions.

El Índice de Postura del Pie: revisión de la literatura / Foot Posture Index: a literature review / Índice de postura: revisão de literatura

OBJETIVO: Realizar una revisión sobre la herramienta clínica de clasificación de la postura del pie en estática, Índice de Postura del Pie, para una mejor comprensión de su uso y aplicabilidad. MÉTODO: Revisión bibliográfica sobre el "Foot Posture Index". Fueron consultados un total de 48 trabajos entre artículos de revista, libros y tesis doctorales. Se descartaron 18, por no cumplir los criterios de inclusión propuestos. RESULTADOS: Se han utilizado 30 textos en castellano e inglés, en los que se relaciona el Índice de Postura del Pie, su fiabilidad en poblaciones diversas y su uso en el mundo de las Ciencias del Deporte. CONCLUSIONES: El Índice de Postura del Pie es una herramienta fácil, fiable, y validada científicamente. Queda demostrada su aplicabilidad en todo tipo de poblaciones, sin existir limitaciones ante situaciones patológicas del miembro inferior. Existen datos que avalan su uso como predictor de lesiones, así como, para la mejora de las aptitudes del deportista

OBJECTIVE: To carry out a review on the clinical tool of classification of the position of the foot in static, Foot Posture Index, for a better understanding of its use and applicability. METHOD: Bibliographical review on the Foot Posture Index. A total of 48 papers were consulted among journal articles, books and doctoral theses. 18 were discarded because they did not meet the inclusion criteria proposed. RESULTS: 30 texts have been used in Spanish and English, in which the classification of the foot has been related to the Foot Posture Index, its reliability in diverse populations and its use in the world of Sport Sciences. CONCLUSIONS: The Foot Posture Index is an easy, reliable and scientifically validated tool. Its applicability has been demonstrated in all types of populations, without specific limitations to altered or pathological situations of the lower limb. Data have been obtained that support its use as a predictor of injuries, as well as for the improvement of the athlete's abilities

OBJETIVO: Realizar uma revisão sobre a ferramenta de classificação clínica Índice de Postura do Pé, para uma melhor compreensão do seu uso e aplicabilidade. MÉTODO: Revisão bibliográfica sobre o "Foot Posture Index". Foram consultados um total de 48 trabalhos entre artigos de revistas, livros e teses de doutorado. Foram descartadas 18, por não cumprir os critérios de inclusão propostos. RESULTADOS: Foram utilizados 30 textos em castelhano e inglês que se relacionaram com o Índice de Postura do Pé, sua fiabilidade em populações diversas e sua utilização no mundo das Ciências do Esporte. CONCLUSÕES: O Índice de Postura do Pé é uma ferramenta fácil, fiável e com validade científica. Sua aplicabilidade é demostrada em todos os tipos de populações, sem existir limitações ante a situações patológicas do membro inferior. Existem dados que avaliam o seu uso como preditor de lesões, assim como, para a melhora da performance desportiva

Typical Shape Differences in the Subtalar Joint Bones Between Subjects with Chronic Ankle Instability and Controls.

Bone shapes, particularly those defining the subtalar joint (STJ), have not received much attention yet as a risk factor for developing chronic ankle instability (CAI) after sustaining a lateral ankle sprain (LAS). This study aimed to compare three-dimensional (3D) shape variations in the STJ bones within individuals with CAI and healthy controls. 3D statistical shape models (SSMs) of the STJ bones were built to describe the bone shape variations observed within a population consisting of 26 individuals with unilateral CAI and 26 healthy controls. Using the SSMs and analysis of covariance test, age- and gender-adjusted shape variations in the bones were compared within individuals with CAI and healthy controls. The mean age of the CAI patients (14 males and 12 females) and healthy controls (12 males and 14 females) was 29 (standard deviation [SD] = 11) and 36 years (SD = 11), respectively. Tali and calcanei did not significantly vary between ipsilateral CAI and their contralateral ankle. Two shape modes, one for the talus (p = 0.015, variations in the curvature of the talar lateral process and the inclination angle of the talar neck relative to the body) and one for the calcaneus (p = 0.003, variations in the medial and lateral tuberosities, and the contour of the anterior articular surface), described significant shape differences between the CAI patients and healthy controls. The CAI patients generally had flatter talar joint surfaces and a flattened calcaneal ground-contact surface. These findings suggest that specific bone shapes may increase the risk of developing CAI after sustaining a LAS. © 2019 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:1892-1902, 2019.

Fiabilidad del ángulo astrágalo-calcáneo para la evaluación de la alineación del retropié / Reliability of the talocalcaneal angle for the evaluation of hindfoot alignment

Introducción: Estudios recientes sugieren que en el tratamiento quirúrgico de las coaliciones tarsianas debería considerarse la deformidad del retropié. El ángulo entre el astrágalo y el calcáneo (AAC) es comúnmente utilizado para la toma de decisiones. Sin embargo, no se ha demostrado su fiabilidad ni se ha normalizado la forma de emplearlo. El objetivo de este estudio fue estandarizar la técnica de medición del AAC y evaluar la reproducibilidad inter- e intraobservador de la técnica propuesta. Métodos: Se analizaron 30 tomografías de pie de 27 pacientes de entre 10 y 17 años de edad. Diez presentaban coaliciones calcáneo-escafoideas, 10 coaliciones astrágalo-escafoideas y 10 sin coaliciones. La reproducibilidad inter- e intraobservador del AAC fue evaluada mediante el coeficiente de correlación intraclase (ICC). Utilizamos un modelo de ANOVA de efectos mixtos para calcular los ICC para acuerdo ICC2(A,1). Este procedimiento se aplicó a los tres observadores (variabilidad interobservador) y a la prueba-reprueba del observador 1 (variabilidad intraobservador). Un valor de p a dos colas ≤0,05 fue considerado como significativo. Resultados: Los acuerdos interobservador e intraobservador fueron excelentes para el AAC. Acuerdo interobservador: ICC2(A,1)=0,95 (p<0,001, IC 95%: 0,77-0,93). Acuerdo intraobservador: ICC2(A,1)=0,99 (p<0,001, IC 95%: 0,97-0,99). Conclusión: El AAC representa un medio fiable para evaluar la alineación del retropié. Este método de medición, tal cual se describe en este estudio, puede ser utilizado de forma segura para el planeamiento quirúrgico en pacientes con coaliciones tarsianas

Introduction: Recent studies suggest that hindfoot deformity should be considered in the surgical treatment of tarsal coalitions. Many authors have used the angle between the talus and the calcaneus (TCA) for decision-making. However, its reliability has not been demonstrated and the measurement technique has not been standardized. The objective of this study was to standardize the TCA measurement technique, and to evaluate the inter and intra-observer reproducibility of the proposed technique. Methods: The foot CT scans of a group of 30 patients between 10 and 17 years of age were analysed. Ten patients had talocalcaneal coalitions, ten calcaneonavicular coalitions and ten had no coalitions. The inter and intra-observer reproducibility of the TCA was evaluated by the intraclass correlation coefficient (ICCs). A mixed-effects ANOVA model was used to calculate the ICCs for ICC2 agreement (A, 1). This procedure was applied to the three observers (inter-observer variability), and to the test-retest of observer 1 (intra-observer variability). A two-tailed p value of ≤.05 was considered significant. Results: The inter-observer and intra-observer agreements were excellent for the TCA. Inter-observer agreement: ICC2 (A, 1)=.95 (p<.001, CI 95%: .77-.93). Intra-observer agreement: ICC2 (A, 1)=.99 (p<.001, CI 95%: .97-.99). Conclusion: The TCA is a reliable way to evaluate hindfoot alignment. This method of measurement, as described in this study, can be safely used for surgical planning in patients with tarsal coalitions

Morphometric analysis of talus and calcaneus.

PURPOSE: The variations in the subtalar joint regarding its morphology and articulation of bones are common worldwide. This study aimed to analyze the morphometric variations in articulating facets of talus and calcaneum in South Indian population. METHODS: For this study, the morphometric parameters of 92 dry tali and 49 dry calcanei of unknown gender were analyzed. The pattern of articulating facets was classified based on Boyan et al. as Type A (A1-A4), Type B (B1 and B2), and Type C. RESULTS: Type B was found to be the most common pattern in the study population (talus-97.8%; calcaneus-80.2%). The morphometric parameters were expressed as mean ± 2 SD. The anteroposterior length of the left talus was more than right talus, while the transverse width of right and left talus is almost equal. The length of right sulcus tali appears to be more than left sulcus tali, whereas the width and depth of right and left sulcus tali was almost equal. The transverse width of the right calcaneus was greater than left calcaneus. Width and depth of right and left sulcus calcanei were almost equal, but the length of right sulcus calcanei was more than the left sulcus calcanei (p value - 0.036). CONCLUSION: Analysis of the pattern of articulating facets of talus and calcaneum and establishing the common types and their morphometric parameters will be helpful as an important tool for reconstruction surgeries of hind-foot deformities and foot rehabilitation procedures.

Morphological characteristics of the lateral talocalcaneal ligament: a large-scale anatomical study.

PURPOSE: The purpose of this study is to clarify the morphological characteristics of the lateral talocalcaneal ligament (LTCL). METHODS: This study examined 100 legs from 54 Japanese cadavers. The LTCL was classified into three types: Type I, the LTCL branches from the calcaneofibular ligament (CFL); Type II, the LTCL is independent of the CFL and runs parallel to the calcaneus; and Type III, the LTCL is absent. The morphological features measured were fiber bundle length, fiber bundle width, and fiber bundle thickness. RESULTS: The LTCL was classified as Type I in 18 feet (18%), Type II in 24 feet (24%), and Type III in 58 feet (58%). All LTCLs were associated with the anterior talofibular ligament at the talus. There was no significant difference in morphological characteristics by Type for each ligament. CONCLUSIONS: The LTCL was similar to the CFL in terms of fiber bundle width and fiber bundle thickness.

Anatomy of the Subtalar Joint.

The subtalar joint is divided into the talocalcaneonavicular and the talocalcaneal joint, separated by a conical interosseous tunnel (canalis and sinus tarsi). The talocalcaneonavicular joint is a ball-and-socket articulation (coxa pedis). An important part of the coxa pedis is the spring ligament. The canalis and sinus tarsi are occupied by the roots of the inferior extensor retinaculum, cervical ligament, interosseous talocalcaneal ligament, and anterior talocalcaneal ligament. Three-dimensional motion in the subtalar joint complex (eversion/inversion) is guided by the axial alignment of the talus, calcaneus, and navicular; the ligaments; and the shape of the articular surfaces.

Update on Subtalar Joint Instability.

Subtalar joint stability is ensured by the osseous geometry of the talocalcaneal joint and the complex array of the ligaments at the medial and lateral aspect of the ankle joint, the sinus and canalis tarsi, and the talocalcaneonavicular joint, respectively. There is still a substantial lack of knowledge about the interaction of the ankle and subtalar joint complex. Subtalar joint instability appears to be more frequent than is generally assumed. The diagnosis of chronic subtalar joint instability makes the application of a comprehensive algorithm necessary. There is ongoing debate about the preferable techniques for restoration of subtalar joint stability.

Simultaneous Intraoperative Measurement of Cadaver Ankle and Subtalar Joint Compression During Arthrodesis With Intramedullary Nail, Screws, and Tibiotalocalcaneal Plate.

BACKGROUND: Suboptimal tibiotalocalcaneal arthrodesis (TTCA) fusion rates may result from inadequate compression that increases motion and interferes with bony bridging. The aim of this study was to evaluate compressive forces at the ankle and subtalar joints with 3 contemporary TTCA constructs. METHODS: Thirty fresh-frozen cadaveric lower extremity specimens were divided into 3 groups of 10 each: 3 partially threaded cannulated screws, hindfoot nail, and lateral plate. Specimens were mounted to a testing apparatus, and compression was independently measured at the tibiotalar and talocalcaneal interfaces. Statistical analysis included paired Student t tests, analysis of variance, and Tukey post hoc tests. RESULTS: Mean forces at the ankle joint for the screws, nail, and plate constructs were 331 ± 86, 479 ± 137, and 548 ± 199 N, respectively, with plates providing significantly more compression than screws ( P < .01). Similarly, subtalar compressive forces demonstrated 319 ± 105 N in the screws group, 466 ± 125 N, in the nail group, and 513 ± 181 N in the plate group, with plate compression greater than that achieved with screws ( P < .01). No differences were identified in compression between ankle and subtalar joints within specimens in any group. CONCLUSIONS: Lateral TTCA plates provided increased compressive forces at the ankle and subtalar joint compared with screws-only constructs. Hindfoot nails did not demonstrate significant differences in either of these parameters compared with plates or screws in this study. CLINICAL RELEVANCE: Hindfoot nail and lateral plate options should be strongly considered when aiming to maximize compression in patients undergoing TTCA.

If It Doesn't Work, Why Do We Still Do It? The Continuing Use of Subtalar Joint Neutral Theory in the Face of Overpowering Critical Research.

The use of subtalar joint neutral (STJN) in the assessment and treatment of foot-related musculoskeletal symptomology is common in daily practice and still widely taught. The main pioneer of this theory was Dr Merton L. Root, and it has been labeled with a variety of names: "the foot morphology theory," "the subtalar joint neutral theory," or simply "Rootian theory" or "Root model." The theory's core concepts still underpin a common approach to musculoskeletal assessment of the foot, as well as the consequent design of foot orthoses. The available literature continues to point to Dr Root's theory as the most prevalently utilized. Concurrently, the worth of this theory has been challenged due to its poor reliability and limited external validity. This Viewpoint reviews the main clinical areas of the STJN theory, and concludes with a possible explanation and concerns for its ongoing use. To support our view, we will discuss (1) historical inaccuracies, (2) challenges with reliability, and (3) concerns with validity. J Orthop Sports Phys Ther 2018;48(3):130-132. doi:10.2519/jospt.2018.0604.

Sonographic and Anatomic Description of the Subtalar Joint.

Our study provides a detailed anatomic and sonographic description of the subtalar joint, a single joint that, anatomically, is divided into the anterior subtalar joint (ASTJ) and the posterior subtalar joint (PSTJ). Cadaver specimens of the ankle and foot were examined in detail by ultrasound (US), and the subtalar joints of all the specimens were injected with colored latex of a contrasting color under US guidance. Compatible with other studies, examination of the sections revealed lack of communication between the ASTJ and the PSTJ and communication between the PSTJ and the posterior recess of the tibiotalar joint. A recommended list of standardized ultrasound scans was developed using a Delphi consensus process, which allows sonographers to evaluate both the ASTJ and PSTJ from the medial, lateral and posterior aspects. The recommended ultrasound scans were found to be applicable based on a test of agreement between images acquired in cadaver specimens and images acquired in four centers using healthy patients.

Foot structure is significantly associated to subtalar joint kinetics and mechanical energetics.

INTRODUCTION/AIM: Foot structure has been implicated as a risk factor of numerous overuse injuries, however, the mechanism linking foot structure and the development of soft-tissue overuse injuries are not well understood. The aim of this study was to identify factors that could predict foot function during walking. METHODS: A total of eleven variables (including measures of foot structure, anthropometry and spatiotemporal gait characteristics) were investigated for their predictive ability on identifying kinematic, kinetic and energetic components of the foot. Three-dimensional motion capture and force data were collected at preferred walking speed on an instrumented treadmill. Mechanical measures were subsequently assessed using a custom multi-segment foot model in Opensim. Factors with significant univariate associations were entered into multiple linear regression models to identify a group of factors independently associated with the mechanical measures. RESULTS: Although no model could be created for any of the kinematic measures analysed, approximately 46% and 37% of the variance in the kinetic and energetic measures were associated with three or two factors respectively. Arch-height ratio, foot length and step width were associated with peak subtalar joint (STJ) moment, while greater STJ negative work was correlated to a low arch-height ratio and greater foot mobility. CONCLUSION: The models presented in this study suggest that the soft-tissue structures of a flat-arched, mobile foot are at a greater risk of injury as they have greater requirements to absorb energy and generate larger forces. However, as these associations are only moderate, other measures may also have an influence.