The effect of changing mediolateral center of pressure on rearfoot eversion during treadmill running

INTRODUCTION: Atypical rearfoot eversion is an important kinematic risk factor in running-related injuries. Prominent interventions for atypical rearfoot eversion include foot orthoses, footwear, and taping, yet a running gait retraining is lacking. Therefore, the aim was to investigate the effects of changing mediolateral center of pressure (COP) on rearfoot eversion, subtalar pronation, medial longitudinal arch angle (MLAA), hip kinematics and vertical ground reaction force (vGRF). METHODS: Fifteen healthy female runners underwent gait retraining under three conditions. Participants were instructed to run normally, on the lateral (COP lateral) and medial (COP medial) side of the foot. Foot progression angle (FPA) was controlled using real-time visual feedback. 3D measurements of rearfoot eversion, subtalar pronation, MLAA, FPA, hip kinematics, vGRF and COP were analyzed. A repeated-measures ANOVA followed by pairwise comparisons was used to analyze changes in outcome between three conditions. Data were also analyzed using statistic parameter mapping. RESULTS: Running on the lateral side of the foot compared to normal running and running on the medial side of the foot reduced peak rearfoot eversion (mean difference (MD) with normal 3.3°, p < 0.001, MD with COP medial 6°, p < 0.001), peak pronation (MD with normal 5°, p < 0.001, MD with COP medial 9.6°, p=<0.001), peak MLAA (MD with normal 2.3°, p < 0.001, MD with COP medial 4.1°, p < 0.001), peak hip internal rotation (MD with normal 1.8°, p < 0.001), and peak hip adduction (MD with normal running 1°, p = 0.011). Running on the medial side of the foot significantly increased peak rearfoot eversion, pronation and MLAA compared to normal running. SIGNIFICANCE: This study demonstrated that COP translation along the mediolateral foot axis significantly influences rearfoot eversion, MLAA, and subtalar pronation during running. Running with either more lateral or medial COP reduced or increased peak rearfoot eversion, peak subtalar pronation, and peak MLAA, respectively, compared to normal running. These results might use as a basis to help clinicians and researchers prescribe running gait retraining by changing mediolateral COP for runners with atypical rearfoot eversion or MLAA

Algorithm for the prediction of the reactive forces developed in the socket of transfemoral amputees

Based on a mathematical model of the human gait, a Matlab 2010a algorithm is presented to predict the reaction forces and moments in a particular point along the socket linked to the lower limb of a transfemoral amputee. The model takes the inertia developed due the swing of the limb during the gait into consideration. A validation of the results is made with the data obtained in a gait lab, and the model results are consistent with those obtained in the gait lab

Centre of pressure estimation during walking using only inertial-measurement units and end-to-end statistical modelling

Estimation of the centre of pressure (COP) is an important part of the gait analysis, for example, when evaluating the functional capacity of individuals affected by motor impairment. Inertial measurement units (IMUs) and force sensors are commonly used to measure gait characteristic of healthy and impaired subjects. We present a methodology for estimating the COP solely from raw gyroscope, accelerometer, and magnetometer data from IMUs using statistical modelling. We demonstrate the viability of the method using an example of two models: a linear model and a non-linear Long-Short-Term Memory (LSTM) neural network model. Models were trained on the COP ground truth data measured using an instrumented treadmill and achieved the average intra-subject root mean square (RMS) error between estimated and ground truth COP of 12.3mm and the average inter-subject RMS error of 23.7mm which is comparable or better than similar studies so far. We show that the calibration procedure in the instrumented treadmill can be as short as a couple of minutes without the decrease in our model performance. We also show that the magnetic component of the recorded IMU signal, which is most sensitive to environmental changes, can be safely dropped without a significant decrease in model performance. Finally, we show that the number of IMUs can be reduced to five without deterioration in the model performance.Comment: 21 page

Desarrollo de un algoritmo computacional para la predicción de fuerzas y momentos en la interfaz socket-extensión femoral durante el ciclo completo de la marcha para amputados transfemorales

Resumen: Con el fin de predecir las fuerzas y momentos en la interface socket-extensión femoral de amputados transfemorales sin necesidad de procedimientos experimentales complejos o extensos en el tiempo, se propone un flujo para el modelado y simulación de la marcha humana. La metodología consiste en un modelo matemático de la geometría del cuerpo humano que puede generar las medidas antropométricas básicas necesarias para escalar un modelo músculo esquelético modificado en Opensim. Un algoritmo es implementado para este modelo en el cual solo el peso, la altura, el género y la longitud del miembro residual son necesarios. El modelo escalado en Opensim es usado para calcular un análisis de contacto articular a partir del cual las fuerzas musculares presentes en el modelo y las fuerzas y momentos resultantes en la interfaz socket-extensión femoral son obtenidas.Abstract: In order to predict the forces and moments in the interface socket-femoral extension of transfemoral amputees without complex or time consuming experimental setups, a frame work for the modelling and simulation of the biomechanics of the human gait is proposed. The methodology consists in a mathematical model of the human geometry that can generate the basic anthropometric measurements necessary to scale a custom made musculo squeletal Opensim model. An algorithm is implemented for this model in which only the weight, stature, gender and residual limb length are necessary. The scaled model in Opensim is used to perform a joint contact analysis from which the muscular forces present in the modeland the resultant forces and moments in the interface socket-femoral extension is extractedMaestrí

Sapato instrumentado para análise e caraterização do andar humano

O presente Relatório do Trabalho de Projeto tem como objetivo a descrição de todo o processo realizado no desenvolvimento de um protótipo de um sapato instrumentado desenhado para adquirir e caraterizar o andar humano. São várias as patologias que afetam o andar humano, uma das tarefas mais importantes do dia-a-dia de uma pessoa. O primeiro passo a ser dado no tratamento de perturbações do andar é o reconhecimento da patologia em causa. Daí a criação deste protótipo para atuar na primeira linha de combate contra a imobilidade, protótipo este, que servirá para analisar e caraterizar o andar humano com base nas forças de reação do solo. Ao longo do documento é apresentado todo o processo levado a cabo no desenvolvimento de toda a arquitetura do sistema. É explicada a criação do protótipo do sapato e as considerações teóricas tidas em conta na orientação dessa mesma construção, o desenvolvimento do hardware e toda a rotina envolvida no firmware para a aquisição dos valores dos sensores de força, o protocolo de comunicação entre o hardware e a estação de tratamento e análise dos dados, e o software desenvolvido para controlo de todo o sistema e análise dos dados. Por fim, são descritas as experiências realizadas, os resultados obtidos a partir do sistema desenvolvido são analisados, seguindo-se uma conclusão e reflexão sobre trabalhos futuros

Joint friction estimation and slip prediction of biped walking robots

Friction is a nonlinear and complex phenomenon. It is unwanted at the biped joints since it deteriorates the robot’s walking performance in terms of speed and dynamic behavior. On the other hand, it is desired and required between the biped feet and the walking surface to facilitate locomotion. Further, friction forces between the feet and the ground determine the maximum acceleration and deceleration that the robot can afford without foot slip. Although several friction models are developed, there is no exact model that represents the friction behavior. This is why online friction estimation and compensation enter the picture. However, when online model-free estimation is difficult, a model-based method of online identification can prove useful. This thesis proposes a new approach for the joint friction estimation and slip prediction of walking biped robots. The joint friction estimation approach is based on the combination of a measurementbased strategy and a model-based method. The former is used to estimate the joint friction online when the foot is in contact with the ground, it utilizes the force and acceleration measurements in a reduced dynamical model of the biped. The latter adopts a friction model to represent the joint friction when the leg is swinging. The model parameters are identified adaptively using the estimated online friction whenever the foot is in contact. Then the estimated joint friction contributes to joint torque control signals to improve the control performance. The slip prediction is a model-free friction-behavior-inspired approach. A measurement-based online algorithm is designed to estimate the Coulomb friction which is regarded as a slip threshold. To predict the slip, a safety margin is introduced in the negative vicinity of the estimated Coulomb friction. The estimation algorithm concludes that if the applied force is outside the safety margin, then the foot tends to slip. The proposed estimation approaches are validated by experiments on SURALP (Sabanci University Robotics Research Laboratory Platform) and simulations on its model. The results demonstrate the effectiveness of these methods

Εμβιομηχανική ανάλυση ασθενών που έχουν υποβληθεί σε δύο διαφορετικούς τύπους ολικής αρθροπλαστικής ισχίου: Ceramic on Ceramic vs Ceramic on XLPE

Η ολική αρθροπλαστική ισχίου (ΤΗΑ) θεωρείται μια εξαιρετικά επιτυχημένη ορθοπεδική επέμβαση που παρέχει εξαιρετικά κλινικά αποτελέσματα, υψηλή ικανοποίηση του ασθενούς, ακολουθούμενη από πολύ ικανοποιητικό προσδόκιμο ζωής. Σύμφωνα με πρόσφατα στοιχεία του βρετανικού εθνικού μητρώου αρθρώσεων (British National Joint Registry), η σωρευτική επιβίωση της THA στα 13 χρόνια είναι 93,2%, με το 80% των εμφυτευμάτων να επιβιώνει έως και 20 χρόνια. Η φθορά του πολυαιθυλενίου θεωρήθηκε ως ο αδύναμος κρίκος της ολικής αρθροπλαστικής ισχίου. Κατά την τελευταία δεκαετία, έχει καταβληθεί σημαντική προσπάθεια για τη βελτιστοποίηση των χαρακτηριστικών φθοράς και την εισαγωγή εναλλακτικών επιφανειών έδρασης. Η εισαγωγή πολυαιθυλενίου με υψηλή διασταύρωση (XLPE) με εξαιρετικά χαρακτηριστικά φθοράς έχει επιφέρει σημαντικές αλλαγές στον τομέα αυτό παγκοσμίως. Οι κεραμικές μηριαίες κεφαλές αντιπροσωπεύουν την τρέχουσα τάση σε πολλά εθνικά μητρώα. Πειράματα in vitro που προσομοιώνουν την κινηματική και την κινητική του βαδίσματος έδειξαν πλεονεκτήματα των προθέσεων Κεραμικό σε Κεραμικό (CoC) σε σύγκριση με τις προθέσεις Κεραμικά σε Πολυαιθυλένιο (CoP) όσον αφορά τον βαθμό φθοράς και την πιθανότητα οστεόλυσης. Τα μειονεκτήματά τους, ωστόσο, περιλαμβάνουν ήχους τριξίματος και αυξημένη ευθραυστότητα. Επιπλέον, στις αρθρούμενες επιφάνειες CoC (σκληρό-σκληρό), δεν υπάρχει η δυνατότητα απόσβεσης ενός μαλακού υλικού, και ως εκ τούτου οι δυνάμεις μετάβασης μεταξύ πρόθεσης και οστού θα μπορούσαν να αυξηθούν. Διάφοροι παράγοντες σχετίζονται με τη φθορά, όπως μεταβλητές σχεδιασμού εμφυτεύματος, (γεωμετρικές ιδιότητες και χαρακτηριστικά υλικού) μεταβλητές χειρουργικής τεχνικής, (χειρουργική προσπέλαση και τοποθέτηση πρόθεσης) και παράγοντες που σχετίζονται με τον ασθενή. Στο τελευταίο, η δύναμη επαφής του ισχίου, που καθορίζεται από την ανθρώπινη κίνηση, επηρεάζει σημαντικά τη φθορά του πολυαιθυλενίου. Οι ροπές του ισχίου στο οβελιαίο επίπεδο εξηγούν μεταξύ 42% και 60% του βαθμού φθοράς, συνδέοντας άμεσα το κινηματικό μοτίβο βάδισης με τη φθορά των εμφυτευμάτων. Παρόλο που οι κλινικές δοκιμές συσχετίζουν άμεσα το κινηματικό μοτίβο βάδισης με τη φθορά του πολυαιθυλενίου σε ολικές αρθροπλαστικές γόνατος, εξ’ όσων μας είναι γνωστά, καμία in vivo έρευνα δεν εξέτασε την κινηματική των ΟΑΙ και τη σχέση της με τη φθορά των εμφυτευμάτων. Όπως ορίζεται από τον Οργανισμό ISO, η φθορά στις ΟΑΙ αναφέρεται στην απώλεια υλικού από τα εξαρτήματα της προσθετικής άρθρωσης λόγω του συνδυασμού κίνησης και φόρτισης και επηρεάζεται από διάφορους παράγοντες. Ένας από τους πιο σημαντικούς είναι η κινηματική και η κινητική των αρθρώσεων κατά τη βάδιση. Αυτός είναι ο λόγος για τον οποίο η κινηματική και η κινητική κατά τη βάδιση χρησιμοποιούνται σε πρωτόκολλα δοκιμών &quot;in vitro&quot;, τα οποία είναι ευρέως αποδεκτές μέθοδοι για την πρόβλεψη της φθοράς των ΟΑΙ. Εάν η πρόβλεψη δεν επιβεβαιωθεί με την αντίστοιχη κλινική απόδοση, τίθεται ένας προβληματισμός σχετικά με οποιοδήποτε νέο υλικό ή σχέδιο. Είναι γεγονός ότι όλα τα εμφυτεύματα εξετάζονται με το ίδιο κινηματικό πρωτόκολλο in vitro, και όπως προαναφέρθηκε οι προθέσεις CoC δείχνουν πλεονεκτήματα στον βαθμό φθοράς σε σύγκριση με τις προθέσεις Κεραμικό σε Υψηλής Διασταύρωσης Πολυαιθυλαίνιο (CoXLPE) σε αυτές τις δοκιμές. Ένα σημαντικό ερώτημα που τίθεται είναι &quot;Προσφέρουν τα υπό εξέταση εμφυτεύματα την ίδια εμβιομηχανική συμπεριφορά και στην κλινική πρακτική;&quot; Ο σκοπός αυτής της μελέτης είναι να εξετάσει την επίδραση της κινηματικής και της κινητικής βάδισης στη φθορά των ΟΑΙ κατά τη διάρκεια του βαδίσματος, την πιο ουσιαστική ανθρώπινη λειτουργική δραστηριότητα, συγκρίνοντας δεδομένα βάδισης in vivo με αποτελέσματα in vitro. Αυτά τα δεδομένα θα είναι πολύτιμα όταν συνδυαστούν με όλους τους προαναφερθέντες παράγοντες που επηρεάζουν τη φθορά στις ΟΑΙ για να αντιμετωπίσουν με πιο λεπτομερή και ολοκληρωμένο τρόπο τη φθορά των CoC και CoXLPE, των πιο ευρέως χρησιμοποιούμενων προθετικών τύπων. Η μηδενική υπόθεση της παρούσας μελέτη είναι ότι και οι δύο τύποι εμφυτευμάτων θα παρουσιάζουν την ίδια αρθρική κινηματική και κινητική συμπεριφορά κατά τη διάρκεια της βάδισης, επιβεβαιώνοντας έτσι τα προαναφερθέντα in vitro αποτελέσματα, επίσης in vivo. Χρησιμοποιήθηκαν ανεξάρτητα t-tests για την στατιστική ανάλυση των κινητικών και κινηματικών δεδομένων που εξήχθησαν από την τρισδιάστατη ανάλυση βάδισης. Δεν παρατηρήθηκαν στατιστικά σημαντικές διαφορές στη μέση ροπή απαγωγής, κάμψης και έκτασης μεταξύ των ομάδων CoC και CoXLPE (P.abduction = 0,125, P.flexion = 0,218, P.extension = 0,082). Οι κινηματικές μετρήσεις δεν δείχνουν επίσης στατιστικά σημαντικές διαφορές. Η κινηματική των ΟΑΙ και η κινητική κατά τη βάδιση είναι σημαντικές βιομηχανικές παράμετροι που σχετίζονται άμεσα με τη φθορά των εμφυτευμάτων. Μελέτες in vitro αναφέρουν μικρότερη φθορά στο CoC από το CoXLPE όταν δοκιμάζονται με το ίδιο κινηματικό πρωτόκολλο κύκλου βάδισης. Τα ευρήματά μας επιβεβαιώνουν ότι και τα δύο εμφυτεύματα συμπεριφέρονται πανομοιότυπα όσον αφορά την κινηματική στο κλινικό περιβάλλον, ενισχύοντας έτσι τα αποτελέσματα in vitro του CoC πλεονεκτήματος. Σε συσχέτιση με όλους τους άλλους σημαντικούς παράγοντες που επηρεάζουν τη φθορά στις ΟΑΙ θα μπορούσε να προσφέρει μια πιο ολοκληρωμένη αξιολόγηση στη φθορά των CoC και CoXLPE.Total hip arthroplasty (THA) is considered an extremely successful orthopedic surgery that provides excellent clinical results, high patient satisfaction, followed by a very satisfactory life expectancy. According to recent data from the British National Joint Registry, the cumulative survival of THA at 13 years is 93.2%, with 80% of implants surviving for up to 20 years. Polyethylene wear was considered the weak link of total hip arthroplasty. Over the last decade, considerable effort has been made to optimize wear characteristics and introduce alternative bearing surfaces. The introduction of high cross-linked polyethylene (XLPE) with excellent wear characteristics has brought about significant changes in this field worldwide. Ceramic femoral heads represent the current trend in many national registries. In vitro experiments simulating kinematics and gait kinetics showed advantages of Ceramic to Ceramic (CoC) prostheses compared to Polyethylene Ceramic (CoP) prostheses in terms of the degree of wear and the possibility of osteolysis. Disadvantages, however, include squeaking sounds and increased fragility. In addition, in CoC (hard-on-hard) articulated surfaces, it is impossible to dampen a soft material, and therefore the forces of transition between prosthesis and bone could be increased. Various factors are associated with wear, such as implant design variables (geometric properties and material characteristics), surgical technique variables (surgical approach and prosthesis placement), and patient-related factors. In the latter, the contact force of the hip, determined by human movement, significantly affects the wear of polyethylene. The hip torques at the sagittal level explain between 42% and 60% of the degree of wear, directly linking the kinematic gait pattern to the wear of the implants. Although clinical trials directly correlate the kinematic gait pattern with polyethylene wear in total knee arthroplasties, to the best of our knowledge, no in vivo research has examined OAI kinematics and its relationship to implant wear. The ISO Organization defines wear on OAIs as the loss of material from the prosthetic joint components due to the combination of movement and loading and is affected by various factors. One of the most important is the kinematics and the kinetics of the joints when walking. This is why kinematics and gait kinetics are used in &quot;in vitro&quot; test protocols, widely accepted methods for predicting OAI wear. Any new material or design is questioned if the corresponding clinical performance does not confirm the prediction. It is a fact that all implants are tested with the same kinematic protocol in vitro, and as mentioned above CoC prostheses show advantages in the degree of wear compared to Ceramics in High Cross Polyethylene (CoXLPE) prostheses in these tests. An important question that arises is, &quot;Do the implants in question offer the same biomechanical behavior in clinical practice?&quot; The purpose of this study is to examine the effect of kinematic and kinetic gait on OAI wear during gait, an essential human functional activity, comparing in vivo gait data with in vitro results. This data will be valuable when combined with all of the above factors that affect OAI wear to address in a more detailed and comprehensive manner the wear of CoC and CoXLPE, the most widely used prosthetic types. The null hypothesis of the present study is that both types of implants will exhibit the same joint kinematic and kinetic behavior during gait, thus confirming the aforementioned in vitro results, also in vivo. Independent t-tests were used for the statistical analysis of kinetic and kinematic data extracted from the three-dimensional gait analysis. No statistically significant differences were observed in the mean abduction, bending, and extension torque between the CoC and CoXLPE groups (P. abduction = 0.125, P. flexion = 0.218, P. extension = 0.082). Kinematic measurements also show no statistically significant differences. OAI kinematics and gait kinetics are important industrial parameters that are directly related to implant wear. In vitro studies report less CoC damage than CoXLPE when tested with the same kinematic gait cycle protocol. Our findings confirm that both implants behave identically in terms of kinematics in the clinical setting, thus enhancing the in vitro results of the CoC advantage. In conjunction with all the other essential factors influencing wear on OAIs, it could offer a more comprehensive CoC, and CoXLPE wear assessment