Segmental foot and ankle kinematic differences between rectus, planus, and cavus foot types

Ability of a multi-segment foot model to measure kinematic differences in cavus, neutrally aligned, asymptomatic planus, and symptomatic planus foot types

BACKGROUND

Multi-segment foot models (MFMs) provide a better understanding of the intricate biomechanics of the foot, yet it is unclear if they accurately differentiate foot type function during locomotion.

RESEARCH QUESTION

We employed an MFM to detect subtle kinematic differences between foot types, including: pes cavus, neutrally aligned, and asymptomatic and symptomatic pes planus. The study investigates how variable the results of this MFM are and if it can detect kinematic differences between pathologic and non-pathologic foot types during the stance phase of gait.

METHODS

Independently, three raters instrumented three subjects on three days to assess variability. In a separate cohort, each foot type was statically quantified for ten subjects per group. Each subject walked while instrumented with a four-segment foot model to assess static alignment and foot motion during the stance phase of gait. Statistical analysis performed with a linear mixed effects regression.

RESULTS

Model variability was highest for between-day and lowest for between-rater, with all variability measures being within the true sample variance. Almost all static measures (radiographic, digital scan, and kinematic markers) differed significantly by foot type. Sagittal hindfoot to leg and forefoot to leg kinematics differed between foot types during late stance, as well as coronal hallux to forefoot range of motion. The MFM had low between-rater variability and may be suitable for multiple raters to apply to a single study sample without introducing significant error. The model, however, only detected a few dynamic differences, with the most dramatic being the hallux to forefoot coronal plane range of motion.

SIGNIFICANCE

Results only somewhat aligned with previous work. It remains unclear if the MFM is sensitive enough to accurately detect different motion between foot types (pathologic and non-pathologic). A more accurate method of tracking foot bone motion (e.g., biplane fluoroscopy) may be needed to address this question.

The importance of foot posture when recording lower leg electromyography when walking in non-textured and textured foot orthoses

Foot posture describes the anatomical variance in an individual's overall foot shape, an important consideration in the provision of foot orthoses. Current orthoses designs could be optimized by considering the topographical organization of cutaneous mechanoreceptors. Currently, the effect of foot orthoses designs to enhance skin stimulation across different anatomical foot posture remains unknown. Thus, the purpose of this study was to investigate how foot posture variance modulates lower leg muscle activity when walking in non-textured orthoses and in textured orthoses which facilitates cutaneous mechanoreceptors under five different regions of the foot sole. Fifty-one (51) healthy young adults were subdivided by the Foot Posture Index and completed level walking trials wearing non-textured and textured foot orthoses. Surface and fine-wire electromyography (EMG) recorded muscle activity in 8 lower leg muscles. Statistically significant interactions were observed in each muscle's average EMG across textured location and Foot Posture Index score. For example, in pes cavus compared to pes planus feet, texture under the calcaneus generated greater aEMG of the tibialis anterior (44.9 mV ± 22.7 mV to 30.9 mV ± 11.4 mV) medial gastrocnemius (26.1 mV ± 16.7 mV to 17.5 mV ± 6.0 mV), and tibialis posterior (84.4 mV ± 77.1 mV to 64.4 mV ± 44.5 mV) muscles. This study demonstrates that lower leg muscle activity is modulated across the foot posture spectrum wearing non-textured and textured foot orthoses. Furthermore, in the development of new orthoses designs, specifically with texture, foot posture remains an important consideration when clinicians interpret EMG results and academics are designing new experimental protocols.

Three-dimensional gait analysis of orthopaedic common foot and ankle joint diseases

Walking is an indispensable mode of transportation for human survival. Gait is a characteristic of walking. In the clinic, patients with different diseases exhibit different gait characteristics. Gait analysis describes the specific situation of human gait abnormalities by observing and studying the kinematics and dynamics of limbs and joints during human walking and depicting the corresponding geometric curves and values. In foot and ankle diseases, gait analysis can evaluate the degree and nature of gait abnormalities in patients and provide an important basis for the diagnosis of patients' diseases, the correction of abnormal gait and related treatment methods. This article reviews the relevant literature, expounds on the clinical consensus on gait, and summarizes the gait characteristics of patients with common ankle and foot diseases. Starting from the gait characteristics of individuals with different diseases, we hope to provide support and reference for the diagnosis, treatment and rehabilitation of clinically related diseases.

Human foot form and function: variable and versatile, yet sufficiently related to predict function from form

The human foot is a complex structure that plays an important role in our capacity for upright locomotion. Comparisons of our feet with those of our closest extinct and extant relatives have linked shape features (e.g. the longitudinal and transverse arches, heel size and toe length) to specific mechanical functions. However, foot shape varies widely across the human population, so it remains unclear if and how specific shape variants are related to locomotor mechanics. Here we constructed a statistical shape-function model (SFM) from 100 healthy participants to directly explore the relationship between the shape and function of our feet. We also examined if we could predict the joint motion and moments occurring within a person's foot during locomotion based purely on shape features. The SFM revealed that the longitudinal and transverse arches, relative foot proportions and toe shape along with their associated joint mechanics were most variable. However, each of these only accounted for small proportions of the overall variation in shape, deformation and joint mechanics, most likely owing to the high structural complexity of the foot. Nevertheless, a leave-one-out analysis showed that the SFM can accurately predict joint mechanics of a novel foot, based on its shape and deformation.

A new alignment device for standardization of marker placement on the hindfoot

BACKGROUND

For multi-segment foot models, next to a (dorsal) heel marker, further markers are typically placed medially (MCL) and laterally (LCL) on the calcaneus. However, there is a lack of easily identifiable landmarks on the hindfoot limiting the repeatability of measurements. For a more consistent placement of these markers, an improved Hindfoot Alignment Device (HiAD) was developed.

METHODS

With the HiAD, the position of the MCL and LCL can be individually scaled. Flexible bars allow the adaptation to foot deformities. Three rater placed markers with the HiAD four times on ten typical developed subjects (20 feet). Rigid segment residuals of the hindfoot were calculated and compared with the residuals when using the device of Simon et al. (2006) [12]. The variability of the placement of MCL, LCL and the clinical parameter medial arch were determined. For assessing the inter- and intra-rater reliability, intraclass correlation coefficient (ICC) and the standard error of measurement (SEM) were calculated.

RESULTS

Rigid segment residuals of the hindfoot could be reduced by 70 % by using the HiAD. Largest inter-rater variability in the MCL and LCL placement was found in z-direction with less than 3.2 ± 2.7 mm and 3.8 ± 2.8 mm, respectively. Correspondingly, largest intra-rater variability was 3.4 ± 2.3 mm for LCL and 2.4 ± 1.9 mm for MCL, respectively. Regarding reliability ICC showed good to excellent results for the medial arch (interrater ICC 0.471-0.811).

SIGNIFICANCE

The application of HiAD to place MCL and LCL appear to be a reliable method with robust marker positions and could be implemented in any multi segment foot model. However, further investigation would be helpful to determine the sensitivity of the marker positions in detecting hindfoot deformities.

Biomechanical Implications of Congenital Conditions of the Foot/Ankle

Segmental foot and ankle models are often used as part of instrumented gait analysis when planning interventions for complex congenital foot conditions. More than 40 models have been used for clinical analysis, and it is important to understand the technical differences among models. These models have been used to improve clinical planning of pediatric foot conditions including clubfoot, planovalgus, and equinovarus. They have also been used to identify clinically relevant subgroups among pediatric populations, quantify postoperative outcomes, and explain variability in healthy populations.

Clinical and multi-segment kinematic analysis of a modified Grice arthrodesis to correct type II adult-acquired flat-foot

BACKGROUND

Adult acquired flat foot (AAFF) is a symptomatic postural alteration of the foot due to modifications in bony structures and/or soft tissues supporting the medial longitudinal arch. For the most severe cases, when orthotic solutions do not provide enough pain relief, surgery may be necessary.

RESEARCH QUESTION

Is it possible to restore a normal medial longitudinal arch and to correct the static and dynamic frontal plane alignment of the rearfoot via a modified Grice surgical procedure in AAFF patients?

METHODS

Eleven patients with stage II AAFF were recruited in the study and underwent the Grice procedure. Patients were assessed via gait analysis using a validated multi-segment foot protocol. Double-leg standing static posture and foot joint kinematics during barefoot walking were measured before surgery and at a mean follow-up of 15 ± 8 months. Twenty-seven age-matched healthy subjects without foot morphological alterations were used as control. Patients' feet were clinically assessed via the Foot Function Index and the Foot Posture Index. Wilcoxon signed rank test was used to assess differences in kinematic and spatio-temporal parameters between pre-op and follow-up evaluations. 1D statistical parametric mapping was used to assess differences in temporal profiles of foot joint rotations.

RESULTS

The clinical indexes significantly improved at post-op (p < 0.05). No differences in sagittal plane static and dynamic joint rotations were observed between pre-op and post-op. In the frontal plane, metatarsus to calcaneus and midfoot to calcaneus rotation angles significantly improved from pre-op to post-op, with the latter resulting consistent with control data. Range of motion and maximum value of the medial longitudinal arch angle were reduced following surgery.

SIGNIFICANCE

The modified Grice procedure restored a good frontal-plane alignment of rearfoot and midfoot, and the clinical scores provided evidence of its effectiveness in significantly reducing pain and improving the quality of daily activities.

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.

Gait Characteristics in Youth With Transverse Myelitis

Background

Transverse myelitis (TM) in childhood is a rare disorder characterized by the presence of spinal cord inflammation. Gait difficulty in children with TM is common; however, there is a paucity of literature regarding quantitative assessment of gait in children and adolescents with TM.

Objectives

To characterize gait patterns in a cohort of ambulatory children with TM and age-matched, typically developing peers in order to better understand the functional mobility of patients diagnosed with childhood TM.

Methods

This was a retrospective study of 26 ambulatory pediatric patients with a confirmed diagnosis of TM who had undergone three-dimensional, instrumented gait analysis (3D-IGA) at 3 years of age or older. A group of 38 typically developing children served as a control group.

Results

Gait in children with TM was characterized by moderate kinematic deviations as measured by the Gait Deviation Index (GDI) and a crouched gait pattern (p < .001), increased anterior pelvic tilt (p < .001), decreased motion at the knees (p < .001), and a wider base of support (foot progression angle, p < .001). The TM group had a slower walking speed (p < .001), shorter strides (p < .001), and an increased stance phase compared to controls.

Conclusion

Our study results showed moderate kinematic deviations quantified by the GDI. Overall, the gait pattern in the TM population tested had greater hip and knee flexion with wider foot progression angle. Identification of gait characteristics in children with TM is the first step in predicting changes in gait pattern as they mature over time, which may ultimately allow for targeted intervention to maintain their ambulatory function.

ISB recommendations for skin-marker-based multi-segment foot kinematics

The foot is anatomically and functionally complex, and thus an accurate description of intrinsic kinematics for clinical or sports applications requires multiple segments. This has led to the development of many multi-segment foot models for both kinematic and kinetic analyses. These models differ in the number of segments analyzed, bony landmarks identified, required marker set, defined anatomical axes and frames, the convention used to calculate joint rotations and the determination of neutral positions or other offsets from neutral. Many of these models lack validation. The terminology used is inconsistent and frequently confusing. Biomechanical and clinical studies using these models should use established references and describe how results are obtained and reported. The International Society of Biomechanics has previously published proposals for standards regarding kinematic and kinetic measurements in biomechanical research, and in this paper also addresses multi-segment foot kinematics modeling. The scope of this work is not to prescribe a particular set of standard definitions to be used in all applications, but rather to recommend a set of standards for collecting, calculating and reporting relevant data. The present paper includes recommendations for the overall modeling and grouping of the foot bones, for defining landmarks and other anatomical references, for addressing the many experimental issues in motion data collection, for analysing and reporting relevant results and finally for designing clinical and biomechanical studies in large populations by selecting the most suitable protocol for the specific application. These recommendations should also be applied when writing manuscripts and abstracts.

Distance mapping of the foot and ankle joints using weightbearing CT: The cavovarus configuration

INTRODUCTION

The goal of this study was to characterize the abnormal joint surface interaction at the ankle, hindfoot and midfoot joints of the cavovarus foot using distance mapping on weightbearing computed tomography (WBCT) images by comparing a series of cavovarus feet to a series of normally-aligned feet.

METHODS

In this case-control study, ten feet (10 patients) with asymptomatic cavovarus shape (cases; N = 10) were compared to 10 matched-paired (by age, gender and body mass index) normally-aligned feet (10 patients) (controls; N = 10). Three-dimensional models were produced from the images and distance maps representing joint surface configuration were generated for the ankle, hindfoot and midfoot joints. The distance maps for each joint were then compared between the two groups and between regions in the same group.

RESULTS

In the cavovarus group there was a significant increase in surface-to-surface distance at the posterior tibiotalar joint and a reduced distance at the anterior part, together with a greater distance at the posterior half of the medial gutter. Also, a decrease in surface-to-surface distance on the anterior half of the anterior facet and an increased distance on the posterior quadrants of the posterior facet of the subtalar joint were found. At the sinus tarsi, the lateral aspect of the talonavicular joint, the naviculocuneiform and the tarsometatarsal joints there was a statistically significant increase in surface-to-surface distance in cavovarus patients as compared to controls.

CONCLUSION

Distance mapping analysis on WBCT images identified significant differences in surface-to-surface interaction at the foot and ankle joints between cavovarus and normally-aligned feet.

LEVEL OF EVIDENCE

Level III, case-control study.

Assignment of local coordinate systems and methods to calculate tibiotalar and subtalar kinematics: A systematic review

The introduction of biplane fluoroscopy has created the ability to evaluate in vivo motion, enabling six degree-of-freedom measurement of the tibiotalar and subtalar joints. Although the International Society of Biomechanics defines a standard method of assigning local coordinate systems for the ankle joint complex, standards for the tibiotalar and subtalar joints are lacking. The objective of this systematic review was to summarize and appraise the existing literature that (1) defined coordinate systems for the tibia, talus, and/or calcaneus or (2) assigned kinematic definitions for the tibiotalar and/or subtalar joints. A systematic literature search was developed with search results limited to English Language from 2006 through 2020. Articles were screened by two independent reviewers based on title and abstract. Methodological quality was evaluated using a modified assessment tool. Following screening, 52 articles were identified as having met inclusion criteria. Methodological assessment of these articles varied in quality from 61 to 97. Included articles adopted primary methods for defining coordinate systems that included: (1) anatomical coordinate system (ACS) based on individual bone landmarks and/or geometric shapes, (2) orthogonal principal axes, and (3) interactive closest point (ICP) registration. Common methods for calculating kinematics included: (1) joint coordinate system (JCS) to calculate rotation and translation, (2) Cardan/Euler sequences, and (3) inclination and deviation angles for helical angles. The methods each have strengths and weaknesses. This summarized knowledge should provide the basis for the foot and ankle biomechanics community to create an accepted standard for calculating and reporting tibiotalar and subtalar kinematics.

A Comparative Biomechanical Analysis during Planned and Unplanned Gait Termination in Individuals with Different Arch Stiffnesses

Although values of arch stiffness index (ASI) have been used to evaluate arch structure and injury susceptibility, investigations are limited regarding the influence of ASI on biomechanical characteristics during gait termination, which involves a challenging balance transition from walking to standing. This study aimed to explore plantar pressure distribution and lower extremity joint kinematic differences between individuals with both a stiff and flexible arch (SA and FA, respectively) during planned and unplanned gait termination (PGT and UGT, respectively). Following the calculation of ASI, sixty-five asymptomatic male subjects were classified and participated in two types of gait termination tests to acquire kinematic and plantar pressure data. Parameters were compared between SA and FA using a two-way ANOVA during PGT and UGT, respectively. UGT was found to have a larger range of motion on the hip joint in the sagittal plane and the knee joint in the transverse plane when compared with PGT. The differences in the kinematic characteristics of the lower limb joints caused by the difference in arch stiffness are mainly concentrated in the ankle and metatarsophalangeal joints. Plantar pressure data, represented by the maximum pressure, showed significant differences in the forefoot and rearfoot areas. These results suggest that ASI could change freedom of motion of the lower limb joints, and UGT tends to conduct a compensatory adjustment for the lower extremity kinetic chain. An understanding of the biomechanical characteristics of arch structures may provide additional insights into foot function and injury prediction during gait termination.

The effect of ankle and hindfoot malalignment on foot mechanics in patients suffering from post-traumatic ankle osteoarthritis

BACKGROUND

Ankle and hindfoot malalignment is a common finding in patients suffering from post-traumatic ankle osteoarthritis. However, no studies have addressed the effect of concomitant foot deformities on intrinsic foot kinematics and kinetics. Therefore, the objective of this study was to investigate the effect of ankle and hindfoot malalignment on the kinematics and kinetics of multiple joints in the foot and ankle complex in patients suffering from post-traumatic ankle osteoarthritis.

METHODS

Twenty-nine subjects with post-traumatic ankle osteoarthritis participated in this study. Standardized weight-bearing radiographs were obtained preoperatively to categorize patients as having cavus, planus or neutral ankle and hindfoot alignment, based on 4 X-ray measurements. All patients underwent standard gait assessment. A 4-segment foot model was used to estimate intrinsic foot joint kinematics and kinetics during gait. Statistical parametric mapping was used to compare foot kinematics and kinetics between groups.

FINDINGS

There were 3 key findings regarding overall foot function in the 3 groups of post-traumatic ankle osteoarthritis: (i) altered frontal and transverse plane inter-segmental angles and moments of the Shank-Calcaneus and Calcaneus-Midfoot joints in the cavus compared to the planus group; (ii) in cavus OA group, Midfoot-Metatarsus joint abduction sought to compensate the varus inclination of the ankle joint; (iii) there were no significant differences in inter-segmental angles and moments between the planus and neutral OA groups.

INTERPRETATION

Future studies should integrate assessment of concomitant foot and ankle deformities in post-traumatic ankle osteoarthritis, to provide additional insight into associated mechanical deficits and compensation mechanisms during gait.

Visual deprivation is met with active changes in ground reaction forces to minimize worsening balance and stability during walking

Previous studies suggest that visual information is essential for balance and stability of locomotion. We investigated whether visual deprivation is met with active reactions tending to minimize worsening balance and stability during walking in humans. We evaluated effects of vision on kinetic characteristics of walking on a treadmill-ground reaction forces (GRFs) and shifts in the center of mass (COM). Young adults (n = 10) walked on a treadmill at a comfortable speed. We measured three orthogonal components of GRFs and COM shifts during no-vision (NV) and full-vision (FV) conditions. We also computed the dynamic balance index (D_N)-the perpendicular distance from the projection of center of mass (pCOM) to the inter-foot line (IFL) normalized to half of the foot length. Locally weighted regression smoothing with alpha-adjusted serial T tests was used to compare GRFs and D_N between two conditions during the entire stance phase. Results showed significant differences in GRFs between FV and NV conditions in vertical and ML directions. Variability of peak forces of all three components of GRF increased in NV condition. We also observed significant increase in D_N for NV condition in eight out of ten subjects. The pCOM was kept within BOS during walking, in both conditions, suggesting that body stability was actively controlled by adjusting three components of GRFs during NV walking to minimize stability loss and preserve balance.