Joint moments and contact forces in the foot during walking

Development and validation of a fully automated tool to quantify 3D foot and ankle alignment using weight-bearing CT

INTRODUCTION

Foot and ankle alignment plays a pivotal role in human gait and posture. Traditional assessment methods, relying on 2D standing radiographs, present limitations in capturing the dynamic 3D nature of foot alignment during weight-bearing and are prone to observer error. This study aims to integrate weight-bearing CT (WBCT) imaging and advanced deep learning (DL) techniques to automate and enhance quantification of the 3D foot and ankle alignment.

METHODS

Thirty-two patients who underwent a WBCT of the foot and ankle were retrospectively included. After training and validation of a 3D nnU-Net model on 45 cases to automate the segmentation into bony models, 35 clinically relevant 3D measurements were automatically computed using a custom-made tool. Automated measurements were assessed for accuracy against manual measurements, while the latter were analyzed for inter-observer reliability.

RESULTS

DL-segmentation results showed a mean dice coefficient of 0.95 and mean Hausdorff distance of 1.41 mm. A good to excellent reliability and mean prediction error of under 2 degrees was found for all angles except the talonavicular coverage angle and distal metatarsal articular angle.

CONCLUSION

In summary, this study introduces a fully automated framework for quantifying foot and ankle alignment, showcasing reliability comparable to current clinical practice measurements. This operator-friendly and time-efficient tool holds promise for implementation in clinical settings, benefiting both radiologists and surgeons. Future studies are encouraged to assess the tool's impact on streamlining image assessment workflows in a clinical environment.

Quantifying walking speeds in relation to ankle biomechanics on a real-time interactive gait platform: a musculoskeletal modeling approach in healthy adults

Background: Given the inherent variability in walking speeds encountered in day-to-day activities, understanding the corresponding alterations in ankle biomechanics would provide valuable clinical insights. Therefore, the objective of this study was to examine the influence of different walking speeds on biomechanical parameters, utilizing gait analysis and musculoskeletal modelling. Methods: Twenty healthy volunteers without any lower limb medical history were included in this study. Treadmill-assisted gait-analysis with walking speeds of 0.8 m/s and 1.1 m/s was performed using the Gait Real-time Analysis Interactive Lab (GRAIL®). Collected kinematic data and ground reaction forces were processed via the AnyBody® modeling system to determine ankle kinetics and muscle forces of the lower leg. Data were statistically analyzed using statistical parametric mapping to reveal both spatiotemporal and magnitude significant differences. Results: Significant differences were found for both magnitude and spatiotemporal curves between 0.8 m/s and 1.1 m/s for the ankle flexion (p < 0.001), subtalar force (p < 0.001), ankle joint reaction force and muscles forces of the M. gastrocnemius, M. soleus and M. peroneus longus (α = 0.05). No significant spatiotemporal differences were found between 0.8 m/s and 1.1 m/s for the M. tibialis anterior and posterior. Discussion: A significant impact on ankle joint kinematics and kinetics was observed when comparing walking speeds of 0.8 m/s and 1.1 m/s. The findings of this study underscore the influence of walking speed on the biomechanics of the ankle. Such insights may provide a biomechanical rationale for several therapeutic and preventative strategies for ankle conditions.

Increase in lateral contact force in the tibiotalar joint during walking in flatfoot patients with reduced stiffness of the spring ligament

Foot deformities in patients with flexible flatfeet, such as the flattened medial arch and hindfoot valgus, affect the force distribution around the tibiotalar joint during walking and increase the risk of secondary injuries. In this study, we developed a multi-segment foot model that could calculate the dynamics around the tibiotalar joint and investigated the difference in the kinetics between normal feet and feet with flatfoot. Ten participants with normal feet and ten with flexible flatfoot were enrolled in the study. The body kinematics, ground reaction force, and foot pressure of the participants were recorded during walking. A five-segment foot model was developed to calculate contact forces in the tibiotalar joint. A flatfoot model was developed by modifying the stiffness of the spring ligaments of a normal foot model. Ground reaction force was applied to the plantar surface of the foot models. The foot models were attached to a full-body musculoskeletal model to conduct inverse dynamic simulations of walking. Participants with flatfoot had significantly greater lateral contact force (1.19 BW vs. 0.80 BW) and more posteriorly located center of pressure (33.7 % vs. 46.6 %) in the tibiotalar joint than those with normal feet (p < 0.05). The average and peak posterior tibialis muscle forces were significantly larger in participants with flatfoot than in those with normal feet (3.06 BW vs. 2.22 BW; 4.52 BW vs. 3.33 BW). The altered mechanics may influence the risk of arthritis.

Implications of obesity in patients with foot and ankle pathology

Obesity is a growing problem defined as a body mass index of greater than 30 kg/m². It is predicted that by 2030, 48.9% of adults will be classified as obese which expands surgical risk factors to a broad population while increasing healthcare costs at the same time in different socioeconomic groups. This specific population has been widely studied in multiple surgical fields and published studies have shown the implications in each of these fields. The impact of obesity on orthopedic surgical outcomes has been previously reported in several total hip and knee arthroscopy studies, with evidence indicating that obesity is strongly associated with an increased risk of post operative complications together with higher revision rates. In line with increasing interest on the impact of obesity in orthopedics, there has been a similar output of publications in the foot and ankle literature. This review article evaluates several foot and ankle pathologies, their risk factors associated with obesity and subsequent management. It provides an updated, comprehensive analysis of the effects of obesity on foot and ankle surgical outcomes, with the ultimate aim of educating both surgeons and allied health professionals about the risks, benefits, and modifiable factors of operating on obese patients.

Prediction of ground reaction forces and moments during walking in children with cerebral palsy

Introduction

Gait analysis is increasingly used to support clinical decision-making regarding diagnosis and treatment planning for movement disorders. As a key part of gait analysis, inverse dynamics can be applied to estimate internal loading conditions during movement, which is essential for understanding pathological gait patterns. The inverse dynamics calculation uses external kinetic information, normally collected using force plates. However, collection of external ground reaction forces (GRFs) and moments (GRMs) can be challenging, especially in subjects with movement disorders. In recent years, a musculoskeletal modeling-based approach has been developed to predict external kinetics from kinematic data, but its performance has not yet been evaluated for altered locomotor patterns such as toe-walking. Therefore, the goal of this study was to investigate how well this prediction method performs for gait in children with cerebral palsy.

Methods

The method was applied to 25 subjects with various forms of hemiplegic spastic locomotor patterns. Predicted GRFs and GRMs, in addition to associated joint kinetics derived using inverse dynamics, were statistically compared against those based on force plate measurements.

Results

The results showed that the performance of the predictive method was similar for the affected and unaffected limbs, with Pearson correlation coefficients between predicted and measured GRFs of 0.71–0.96, similar to those previously reported for healthy adults, despite the motor pathology and the inclusion of toes-walkers within our cohort. However, errors were amplified when calculating the resulting joint moments to an extent that could influence clinical interpretation.

Conclusion

To conclude, the musculoskeletal modeling-based approach for estimating external kinetics is promising for pathological gait, offering the possibility of estimating GRFs and GRMs without the need for force plate data. However, further development is needed before implementation within clinical settings becomes possible.

Ankle joint contact force profiles differ between those with and without chronic ankle instability during walking

BACKGROUND

Individuals with chronic ankle instability (CAI) exhibit aberrant gait biomechanics relative to uninjured controls. Altered gait biomechanics likely contribute aberrant joint loading and subsequent early onset ankle joint degeneration. Joint (i.e. cartilage) loading cannot be directly measured without invasive procedures but can be estimated via joint contact forces (JCF) generated from musculoskeletal modeling. However, no investigation has quantified JCF in those with CAI during walking despite the link between ligamentous injury and ankle post-traumatic ankle osteoarthritis.

RESEARCH QUESTION

Do patients with CAI exhibit altered ankle compressive and shear JCF profiles during the stance phase of walking compared to those without CAI?

METHODS

Ten individuals with CAI and 10 individuals without a history of ankle sprain completed a gait assessment at their self-selected speed on an instrumented treadmill. Musculoskeletal modeling was applied to estimate ankle JCF variables within a generic model. Variables included the peak, impulse, and loading rates for compressive, anteroposterior shear, and mediolateral shear JCF.

RESULTS

Those with CAI had significantly different JCF forces, relative to uninjured controls, in all directions. More specifically, lower compressive peak and impulse values were noted while higher anteroposterior shearing forces (1 st peak, impulse, loading late) were observed in those with CAI. Those with CAI also demonstrated higher mediolateral shearing forces (1 st peak and impulse).

SIGNIFICANCE

Our finding suggests that those with CAI exhibit different ankle joint loading patterns than uninjured controls. Directionality of the identified differences depends on the axis of movement.

Association of Elevated Body Mass Index and Outcomes of Arthroscopic Treatment for Osteochondral Lesions of the Talus

Background:

Osteochondral lesions of the talus (OLTs) are a common condition found in patients with chronic ankle pain after previous ankle sprains. Surgical management is indicated after conservative management has failed.

Hypothesis/Purpose:

This study evaluates the influence of body mass index (BMI) on the early clinical outcomes of arthroscopic debridement and microfracture of OLTs.

Methods:

A total of 252 patients with symptomatic OLTs who failed conservative management underwent arthroscopic debridement and microfracture of OLTs over the affected ankle between 2007 and 2017. Patients from this cohort were divided into 2 groups based on BMI: the normal BMI group (NB Group) (BMI 18.5-25.0) and overweight and obese BMI group (OB Group) (BMI ≥25). Visual analogue scale (VAS), American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score, and the physical and mental component summaries of the 36-Item Short-Form Health Survey (PCS and MCS, respectively) were prospectively collected from the cohort during their standard postoperative outpatient follow-up.

Results:

The NB Group (n=105) and OB Group (n=147) were well matched demographically. The operative duration was significantly shorter for the NB Group compared to the OB Group. Patients from both groups had significant improvements in VAS, AOFAS, and PCS scores postoperatively at 6 and 24 months after surgery ( P < .05). Between both groups, patients had comparable VAS, AOFAS, and PCS scores at preoperation, 6 months postoperation, and 24 months postoperation ( P > .05). However, MCS in the OB Group was lower at 24 months postoperatively compared with the NB Group ( P < .05). The OB Group reported better satisfaction scores (82.4% vs 72.6%, P < .05), and a greater proportion had their expectations met (88.2% vs 77.9%, P < .05).

Conclusion:

A BMI ≥25 was not associated with worse postoperative pain and functional outcomes, but rather was found to be associated with greater satisfaction and fulfillment. However, patients with BMI ≥25 required longer procedure duration and had poorer MCS scores at 24 months after surgery. Level of Evidence: Level III, retrospective cohort study.

Low-Dose Radiotherapy Leads to a Systemic Anti-Inflammatory Shift in the Pre-Clinical K/BxN Serum Transfer Model and Reduces Osteoarthritic Pain in Patients

Osteoarthritis (OA) is the leading degenerative joint disease in the western world and leads, if left untreated, to a progressive deterioration of joint functionality, ultimately reducing quality of life. Recent data has shown, that especially OA of the ankle and foot are among the most frequently affected regions. Current research in OA points towards a complex involvement of various cell and tissue types, often accompanied by inflammation. Low-dose radiotherapy (LDRT) is widely used for the treatment of degenerative and inflammatory diseases. While the reported analgesic effects are well known, the underlying molecular mechanisms are only poorly understood. We therefore correlated a clinical approach, looking at pain reduction in 196 patients treated with LDRT with a pre-clinical approach, utilizing the K/BxN serum transfer mouse model using flow cytometry and multiplex ELISA for analysis. While an improvement of symptoms in the majority of patients was found, patients suffering from symptoms within the tarsi transversa show a significantly lower level of improvement. Further, a significant impact of therapy success was detected depending on whether only one or both feet were affected. Further, patients of younger age showed a significantly better outcome than older ones while needing fewer treatment series. When looking on a cellular level within the mouse model, a systemic alteration of immune cells namely a shift from CD8+ to CD4+ T cells and reduced numbers of DCs was observed. A general reduction of inflammatory cytokines was detected, with significant alterations in IL-4 and IL-17 levels, all of which could potentially be responsible for the highly effective clinical improvement in patients. Taken together our data indicate that LDRT can be regarded as a highly effective treatment option for patients suffering from OA of the foot and ankle, in terms of analgesic effects, especially in younger patients. Furthermore, the observed effects are mediated by an interplay of cellular and soluble immune factors, as observed in the K/BxN serum transfer model. With this interdisciplinary approach we aim to encourage the usage of LDRT as an additive treatment strategy not only as a last resort, but also earlier in the course of disease.

Acute Vibration Feedback During Gait Reduces Mechanical Ankle Joint Loading in Chronic Ankle Instability Patients

BACKGROUND

Individuals with chronic ankle instability (CAI) exhibit altered vertical ground reaction forces (vGRF), a laterally shifted center of pressure, and an inverted foot position during walking. These neuromechanical alterations are linked with altered ankle joint loading in this population. Vibration-based gait retraining improves center of pressure positioning but effects on neuromechanical variables influencing joint loading remains unknown.

RESEARCH QUESTION

Do patients with CAI exhibit altered vGRF and ankle joint contact forces (JCF) after receiving a single session of vibration-based gait retraining?

METHODS

Ten individuals with CAI underwent a single session of vibration-based gait retraining. Kinematic and kinetic data were collected during walking on an instrumental treadmill with force plates embedded in it. Following a baseline gait assessment without feedback, participants walked at a self-selected speed for 10 minutes while receiving feedback. Data was collected during an early (1 st and 2 nd minute) and late adaptation phase (9 th and 10 th minute) and, compared to baseline values. Impact and propulsive vGRF variables (i.e. peak, time to peak, and loading rate) were obtained. Musculoskeletal modeling was used to calculate ankle JCF variables (peak, impulse, and loading rate) during stance phase.

RESULTS

Propulsive vGRF and ankle JCF outcomes were significantly reduced during the early and late adaptation phases (p ≤ 0.039).

SIGNIFICANCE

These results indicate that vibration-based gait retraining can immediately reduce propulsive vGRF and ankle JCF and may represent a modality that could help restore appropriate ankle joint loading patterns in those with CAI.

Predicting ground reaction and tibiotalar contact forces after total ankle arthroplasty during walking

The motion capture and force plates data are essential inputs for musculoskeletal multibody dynamics models to predict in vivo tibiotalar contact forces. However, it could be almost impossible to obtain valid force plates data in old patients undergoing total ankle arthroplasty under some circumstances, such as smaller gait strides and inconsistent walking speeds during gait analysis. To remove the dependence of force plates, this study has established a patient-specific musculoskeletal multibody dynamics model with total ankle arthroplasty by combining a foot-ground contact model based on elastic contact elements. And the established model could predict ground reaction forces, ground reaction moments and tibiotalar contact forces simultaneously. Three patients' motion capture and force plates data during their normal walking were used to establish the patient-specific musculoskeletal models and evaluate the predicted ground reaction forces and ground reaction moments. Reasonable accuracies were achieved for the predicted and measured ground reaction forces and ground reaction moments. The predicted tibiotalar contact forces for all patients using the foot-ground contact model had good consistency with those using force plates data. These findings suggested that the foot-ground contact model could take the place of the force plates data for predicting the tibiotalar contact forces in other total ankle arthroplasty patients, thus providing a simplified and valid platform for further study of the patient-specific prosthetic designs and clinical problems of total ankle arthroplasty in the absence of force plates data.

The increase of joint contact forces in foot joints with simulated subtalar fusion in healthy subjects

BACKGROUND

Subtalar fusion usually leads to a satisfactory clinical outcome by eliminating the motion of the subtalar joint but can cause an aggravation of osteoarthritis after the subtalar fusion. Previous studies have investigated the effect of subtalar fusion in static testing using cadaver limbs, but there was no evidence of an aggravation of osteoarthritis.

RESEARCH QUESTION

The objective was to investigate the differences in foot joint kinematics and kinetics during a standing pose and walking with and without subtalar fusion, using a musculoskeletal simulation.

METHODS

Full-body joint kinematics, ground reaction force, and foot pressure of the healthy subjects were recorded during walking using an optical motion capture system. The models with and without subtalar fusion were constructed using the AnyBody Modeling System (AnyBody Technology, Aalborg, Denmark). The range of motion and contact forces in the individual foot joints with and without simulated subtalar fusion in healthy subjects were estimated using computational simulation and compared using the Wilcoxon signed-rank test. The change of motion in the Chopart's joint was observed.

RESULTS

Normalized to the subject's body weight (BW), the average maximum contact forces in the tibiotalar and Lisfranc joints during walking were significantly increased by 2.6 and 0.9 BW with the simulated subtalar joint fusion, respectively. The simulated subtalar joint fusion increased joint contact forces significantly during walking, which can increase the risks of secondary arthritis in the adjacent joints.

SIGNIFICANCE

The subtalar joint fusion increased the joint contact forces in adjacent joints during walking implying that the fusion can increase the risk of secondary injuries in adjacent joints in the foot.