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Background: Patellar height is a valuable measure to evaluate the effect of patellar tendon advancement (PTA) on knee function. In the literature, there is no validated procedure to measure the patellar height. In this study we aimed to (1) determine the patella position through musculoskeletal modeling, (2) investigate the effects of two surgical procedures applied for PTA, and (3) assess the effect of PTA in combination with single-event multilevel surgery (SEMLS) on the knee kinematics of patients with cerebral palsy (CP) and crouch gait. Method: Three-dimensional gait and X-ray data of children with CP and crouch gait were retrospectively analyzed if they had received a SEMLS in combination with PTA (PTA group, n = 18) or without PTA (NoPTA group, n = 18). A computational musculoskeletal model was used to quantify patella position, knee extension moment arm, and knee kinematics pre and postoperatively. Results: Patellar height significantly decreased in the PTA group (P = 0.004), while there was no difference in the NoPTA group (P > 0.05). The bony procedure for PTA provided a better Insall-Salvati ratio than the soft tissue procedure. The peak knee extension moment arm significantly increased in the PTA group (P = 0.008). In terms of postoperative knee joint kinematics, the PTA group was closer to typically developed children than the NoPTA group. Conclusion: Musculoskeletal modeling was found to be an effective tool for the determination of the patellar height. PTA improved the patella position, knee extension moment arm, and knee kinematics and was an effective procedure for the surgical management of crouch gait in patients with CP. (c) 2021 Elsevier B.V. All rights reserved.

Background Although functional methods determining the hip joint center (HJC) are becoming increasingly popular, no systematic investigation has been conducted yet to assess the reliability of functional hip joint calibration in patients with cerebral palsy (CP). Research question What is the most reliable way to conduct functional calibration motions for estimating HJC location in children with CP and movement disorders? Methods Twenty-two patients with CP were included in the study. A marker set for Plug-in Gait with additional cluster markers was used. Two functional calibration movements, including a new movement, were proposed and tested with one and three repetitions each. Functional HJCs were determined using the SCoRE approach and compared to results obtained by applying the conventional regression method for assessing face validity. Results The choice of calibration movement had significant impact on SCoRE residuals and HJC location. Increasingly repeating calibration movements did not improve results. A modified star movement by allowing the toes to tip the ground provided the most reliable data and is feasible for children with GMFCS level I-III. The feasibility of the method is further improved by analyzing hip motion in the contralateral stance limb and, among the calibration movements, gave the most precise HJC estimation. Significance Type and performance of the functional calibration movement is one key factor for determining a robust HJC. Analyzing the data in the stance leg via the modified star motion yielded robust and reasonable results for the HJC location, which should be validated in further studies that include imaging methods. Using one repetition instead of three seems promising in terms of feasibility for patients with movement disorder.

Background Clinical gait analysis is a crucial step for identifying foot disorders and surgery planning. However, a large amount of gait data makes this assessment difficult and time-consuming. There are separate efforts to reduce its complexity by manually or automatically finding features (e.g. minimum of a joint angle in a specific axis), identifying the foot condition by Machine Learning (ML), and interpreting the outcome by explainable artificial intelligence (xAI). Methods In this article, we explore the potential of state-of-the-art ML algorithms to automate all these steps for a set of 6 foot conditions. New features are created manually and then recursive feature elimination is employed based on Support Vector Machines (SVM) and Random Forest (RF) to eliminate the features with low variance. SVM, RF, K-nearest Neighbor (KNN), Logistic Regression (LREGR), and Majority Voting (MV) algorithms are compared for classification and Local Interpretable Model-agnostic Explanation (LIME) is used for the interpretation of the outcome of the ML models. 40 features are eliminated and 334 features are given to the classifier models as inputs. Results The foot conditions are classified with a maximum average accuracy of 0.86 by KNN and MV, maximum average recall of 0.97 by KNN, and max average F1 score of 0.86 by KNN and MV. Conclusions High success scores indicate that the relation between the selected features and foot conditions should be strong and meaningful, potentially indicating clinical relevance. All models are interpreted for each foot condition for random 20 patients and the most contributing features are graphically demonstrated. The proposed ML pipeline can be easily extended for other foot conditions and retrained as new data arrives. It can help experts and physicians in the identification of foot conditions and the planning of potential surgeries.

There are detailed findings on hip and knee joint parameters determined via functional calibration methods for use in instrumented 3D-gait analysis but these methods have not yet been addressed to the foot.Are functional calibration methods feasible for determining foot joint parameters and may they help for clinical interpretation of foot deformities?Rigid segments were formed by markers on forefoot and hindfoot via a least square method. The position of the midfoot joint articulating both foot segments was then determined via a functional calibration motion. This two-stage procedure was applied on a cohort of 17 typically developed adults and one subject with severe planovalgus foot deformity for determining the location of the midfoot joint and kinematics of hindfoot and forefoot.The position of the midfoot joint center could be estimated in the typically developed cohort and also in the demonstration case with planovalgus foot deformity. Depending on the choice of marker set for hindfoot and forefoot, the position of the joint center varied in the anatomic midfoot region with most robust results when addressing the marker on the navicular to the hindfoot.The presented method for joint center determination within the foot and the characteristic results of the foot joint angles appear promising for typically developed feet. However, further validation of the method is needed for application in clinical context.

Background Despite of many attempts to determine or correct hip and knee joint parameters via non-invasive techniques such as regression or functional methods, in conventional gait models the position of the ankle joint center still is assumed at the center point between malleoli. Research question The aim of this study was to estimate the ankle joint parameters using a functional approach. Methods To this aim, we used data of 23 typically developed adults performing two different calibration motions. Subsequently, we applied functional approaches to determine the functional joint center and axis. Results The results show significant differences for ankle joint parameters in all directions for both calibration motions applied with respect to the malleoli line. Most prominently, we find a shift of the ankle joint center of 7 % of the foot length anteriorly to the malleoli mid-point when applying functional calibration. Conclusion These significant alterations of the ankle joint center and axis indicate the importance of accurate determination of ankle joint parameters and consequently their influence on the clinical outcome.

Individuals with trans-tibial amputation show a greater peak prosthetic ankle power (push- off) when using energy storing and returning (ESAR) prosthetic feet as compared to solid-ankle cushion-heel feet. ESAR feet further contribute to the users' body support and thus limit prosthetic ankle motion. To improve ankle motion, articulating prosthetic feet have been introduced. However, articulating feet may diminish push-off.Does a novel prosthetic foot, with a serial layout of carbon fibre leaf springs, connected by a multi-centre joint construction, have advantages in kinematics and kinetics over a conventional ESAR prosthetic foot?METHODS: Eleven individuals with unilateral trans-tibial amputation were fitted with the novel foot (NF) and a conventional ESAR Foot (CF) and underwent 3D gait analysis. As an additional power estimate of the prosthetic ankle, a unified, deformable, segment model approach was applied. Eleven matched individuals without impairments served as a reference.The NF shows an effective prosthetic ankle range of motion that is closer to a physiologic ankle range of motion, at 31.6° as compared to 15.2° with CF (CF vs. NF p = 0.003/NF vs. Reference p = 0.171) without reducing the maximum prosthetic ankle joint moment. Furthermore, the NF showed a great increase in prosthetic ankle power (NF 2.89 W/kg vs. CF 1.48 W/kg CF vs. NF p = 0.001) and a reduction of 19% in the peak knee varus moment and 13% in vertical ground reaction forces on the sound side for NF in comparison to CF.The NF shows that serial carbon fibre leaf springs, connected by a multi-centre joint construction gives a larger ankle joint range of motion and higher ankle power than a conventional carbon fibre structure alone. Consequently load is taken off the contralateral limb, as measured by the decrease in vertical ground reaction forces and peak knee varus moment.

Duchenne gait is characterized by trunk lean towards the affected stance limb with the pelvis stable or elevated on the swinging limb side during single limb stance phase. We assessed the relationship between hip abduction moments and trunk kinetics in patients with cerebral palsy showing excessive lateral trunk motion. Data of 18 subjects with bilateral spastic cerebral palsy (CP) and 20 aged matched typically developing subjects (TD) were collected retrospectively. Criteria for patient selection were barefoot walking without aid presenting with excessive lateral trunk motion. Subjects had been monitored by conventional 3D gait analysis of the lower extremity including four markers for monitoring trunk motion. Post-hoc, a generic musculoskeletal full body model (OpenSim 3.3) assuming a rigid trunk articulated to the pelvis by a single ball joint was applied for analyzing joint kinematics and kinetics of the lower limb joints including this spine joint. Joint angle ranges of motion, maximum joint moments and powers in the frontal plane as well as mechanical work were calculated and averaged within groups showing prominent differences between groups in all parameters. To the best of our knowledge, this is the first work explicitly looking into the kinetics of Duchenne gait in patients with CP, clinically known as compensation for unloading hip abductor muscles. The results show that excessive lateral trunk motion may indeed be an extremely effective compensation mechanism to unload the hip abductors in single limb stance but for the price of a drastic increase in demand on trunk muscle effort and work.

Background Attempts to improve protocol standards of marker-based clinical gait analysis (CGA) have been one of the main focuses of research to enhance robustness and reliability outcomes since the 1990s. Determining joint centres and axes constitutes an important aspect of those protocols. Although the hip joint is more prominent in such studies, knee joint center (KJC) and axis (KJA) directly affect all outcomes. Research question What recommendations arise from the study of the scientific literature for determining knee joint parameters (KJP) for protocols of CGA? Methods A systematic, electronic search was conducted on November 2018 using three databases with the keyword combination (“functional approach” OR “functional method” OR “functional calibration”) AND (“hip joint” OR “knee joint” OR “ankle joint”) and analyzed by four reviewers. Given the existence of a recent review about the hip joint and the lack of material about the ankle joint, only papers about the knee joint were kept. The references cited in the selected papers were also screened in the final round of the search for these publications. The quality of the selected papers was assessed and aspects regarding accuracy, repeatability, and feasibility were thoroughly considered to allow for a comparison between studies. Technical aspects, such as marker set choice, KJP determination techniques, demographics, and functional movements, were also included. Results Thirty-one papers were included and on average received a rating of about 75 % according to the quality scale used. The results showed that functional methods are superior or equivalent to predictive methods to estimate the KJA, while a regression method was slightly better for KJC prediction. Significance Calibration methods should be applied to CGA whenever feasibility is reached. No study to date has focused on evaluating the in vivo RoM required to obtain reliable and repeatable results and future work should aim in this direction.

To evaluate short-term (1y postoperatively; E1) and long-term (at least 4y postoperatively; E2) changes in hamstring muscle-tendon length (MTL) and lengthening velocity after hamstring lengthening in children with bilateral cerebral palsy (CP).Three-dimensional gait analysis was performed in 19 children (16 males, 3 females; 36 limbs; mean age at surgery 9y [SD 3y]; range 6-10y) with flexed knee gait, preoperative ankle dorsiflexion lower than 20 degrees, and CP before bilateral hamstring lengthening (E0), at E1 and E2. Hamstring MTL (normalized by leg length) and velocity were assessed via OpenSim software.MTL increased from E0 to E1 (p=0.004) and decreased from E1 to E2 (p0.020). Hamstring lengthening velocity did not change. In the subgroup with short, not slow hamstrings, the increase in MTL was maintained at E2.Hamstring lengthening is an efficient procedure to lengthen short and/or slow hamstrings short-term. The desired outcome with maintenance of the postoperative changes in hamstring MTL is only achieved for preoperatively short, not slow hamstrings.Surgical hamstring lengthening can be confirmed via musculoskeletal modelling in OpenSim software. Surgical hamstring lengthening in cerebral palsy does not change hamstring lengthening velocity. Short, not slow hamstrings present a long-lasting muscle-tendon length (MTL) increase after hamstring lengthening. Changes in MTL after hamstring lengthening cannot be maintained for slow hamstrings. MTL does not change after hamstring lengthening for neither short nor slow hamstrings.CAMBIOS MUSCULARES A LARGO PLAZO DESPUÉS DEL ALARGAMIENTO DE LOS ISQUIOTIBIALES EN NIÑOS CON PARÁLISIS CEREBRAL BILATERAL: OBJETIVO: Evaluar los cambios a corto plazo (un año después de la operación; E1) y a largo plazo (al menos cuatro años después de la operación; E2) de la longitud del tendón muscular de los isquiotibiales (LT) y la velocidad de alargamiento después del estiramiento en niños con parálisis cerebral bilateral (PC). MÉTODO: Se realizó un análisis tridimensional de la marcha en 19 niños (16 varones, tres mujeres; 36 extremidades; edad media en la cirugía 9 años [DS 3 años]; rango 6-10 años) con la marcha en flexión de la rodilla, dorsiflexión preoperatoria del tobillo inferior a 20 grados, antes del alargamiento bilateral de los isquiotibiales (E0), en E1 y E2. El LT de los músculos isquiotibiales (normalizado por la longitud de la pierna) y la velocidad fueron evaluadas mediante el OpenSim. RESULTADOS: El LT aumentó de E0 a E1 (p = 0,004) y disminuyó de E1 a E2 (p0,020). La velocidad de alargamiento de los isquiotibiales no cambió. En el subgrupo con isquiotibiales cortos, pero no lentos, el aumento de la LT se mantuvo en E2. INTERPRETACIÓN: El alargamiento de los isquiotibiales es un procedimiento eficiente para los isquiotibiales cortos y/o lentos a corto plazo. El resultado deseado con el mantenimiento de los cambios postoperatorios en la longitud de los isquiotibiales solo se logra para los isquiotibiales cortos no lentos antes de la operación.ALTERAÇÕES MUSCULARES A LONGO PRAZO APÓS ALONGAMENTO DE ISQUIOTIBIAIS EM CRIANÇAS COM PARALISIA CEREBRAL BILATERAL: OBJETIVO: Avaliar a curto (um ano de pós-operatório; E1) e longo prazo (no mínimo quatro anos de pós-operatório; E2) alterações no comprimento do tendão do músculo (CTM) isquiotibial e a velocidade de estiramento após alongamento do isquiotibial em crianças com paralisia cerebral bilateral (PC). MÉTODO: Foi realizada a análise tridimensional da marcha em 19 crianças (16 meninos, três meninas; 36 membros; média de idade de cirurgia de 9 anos [DP 3 anos]; variação de 6-10 anos) com marcha com flexão de joelho, ângulo de dorsiflexão de tornozelo menor que 20

AIM Flexed knee gait can be treated with distal femoral extension osteotomy (DFEO) and additional patellar tendon advancement (PTA) in children with cerebral palsy (CP). This study assesses changes in hamstring muscle tendon length (MTL) and velocity after DFEO (+PTA). METHOD Nineteen children (mean age 13y [standard deviation 3y] at surgery) with CP and flexed knee gait who were treated with DFEO (15 limbs) or DFEO+PTA (10 limbs) were retrospectively included in this study. Gait analyses were performed preoperatively (E0), 1 year postoperatively (E1), and for 10 limbs additionally 2 to 5 years postoperatively (E2). Hamstring MTL and velocities were assessed at all examination dates using OpenSim. RESULTS Hamstring MTL and velocity did not change significantly over time. From E0 to E1, knee flexion in stance improved for both DFEO and DFEO+PTA (p

Modeling the socket and residual limb for trans femoral amputees using a virtual joint concept.

Assessment of angular momentum and harmonic ratio for children with cerebral palsy during walking.

The motion data of three patients with cerebral palsy were used to analyze velocity, stride length and stride time parameters during walk to run transition. The results showed that subjects were able to perform the transition while keeping their dynamic equilibrium.

The incidence of knee and hip joint osteoarthritis in subjects with below knee amputation (BK) appears significantly higher compared to unimpaired subjects, especially in the intact side. However, it is controversial if constant higher loads on the sound side are one of the major factors for an increased osteoarthritis (OA) incidence in subjects with BK, beside other risk factors, e.g. with respect to metabolism. The aim wasto investigate joint contact forces (JCF) calculated by a musculoskeletal model in the intact side and to compare it with those of unimpaired subjects and to further elucidate in how far increased knee JCF are associated with increased frontal plane knee moments. A group of seven subjects with BK amputation and a group of ten unimpaired subjects were recruited for this study. Gait data were measured by 3D motion capture and force plates. OpenSim software was applied to calculate JCF. Maximum joint angles, ground reaction forces, and moments as well as time distance parameters were determined and compared between groups showing no significant differences, with some JCF components of knee and hip even being slightly smaller in subjects with BK compared to the reference group. This positive finding may be due to the selected ESAR foot. However, other beneficial factors may also have influenced this positive result such as the general good health status of the subjects or the thorough and proper fitting and alignment of the prosthesis.

In this study, based on kinematics data in steppage gait, a finite element model of human gait with ankle-foot orthosis (AFO) has been proposed to optimize the role of AFO through minimizing stress in the patients' sole. The required kinetics data for the model were captured through a force plate and then analysed by 3D-DOCTOR and ANSYS software. In the proposed three-dimensional finite element model the transmitted tension in soft tissue and bones during gait was calculated. By changing the thickness and materials of different layers of sole in AFO the tension variations have been assessed. Unlike previous studies, the effect of orthosis on tension generated in bones and muscles has been dynamically and continuously modelled and the contact between AFO and sole has been considered in this model. By using the optimized sole the stress distribution has been changed by +50.38% in the forefoot, +15% in the midfoot and -37.79% in the hindfoot. The tension reduction in the sole can improve the effect of AFO during abnormal gait. It is possible to design each orthosis sole based on the kinetics data of each patient.

Background: This pilot study aimed to assess quantitative differences between normal and steppage gait by analyzing force plate data. Materials and Methods: We studied 25 subjects with drop foot, who were treated in the orthopedic center for drop foot brace. Twenty healthy students were included as a control group. There were no differences in the age, weight, height, and body mass index between the patients and the controls (p > 0.05). They walked at self-selected speed with a mean of 10 trials (+2) to collect their ground reaction forces data by force plate. Results: There were no significant differences between the groups in antero-posterior component of ground reaction force (p > 0.05). There was significant relationship between the time parameters in vertical and medio-lateral components of ground reaction forces (p < 0.05). We have found that the medio-lateral impulse in the patients group is negative (p < 0.05), which means instability in patients' gait. Conclusion: The result of this research reveals that the analysis of ground reaction force quantitatively describes steppage gait. The average stance time among patients is longer than control group. Further work with a larger database of subjects is required to confirm our findings.

The aim of this study is analyzing the differences between plane walking and stepping over an obstacle for two groups of healthy people and people with Down syndrome and then, evaluating the movement efficiency between the groups by comprising of their mechanical energy exchanges. 39 adults including two groups of 21 people with Down syndrome (age: 21.6 ± 7 years) and 18 healthy people (age: 25.1 ± 2.4 years) participated in this research. The test has been done in two conditions, first in plane walking and second in walking with an obstacle (10% of the subject's height). The gait data were acquired using quantitative movement analysis, composed of an optoelectronic system (Elite2002, BTS) with eight infrared cameras. Mechanical energy exchanges are computed by dedicated software and finally the data including spatiotemporal parameters, mechanical energy parameters and energy recovery of gait cycle are analyzed by statistical software to find significant differences. Regards to spatiotemporal parameters velocity and step length are lower in people with Down syndrome. Mechanical energy parameters particularly energy recovery does not change from healthy people to people with Down syndrome. However, there are some differences in inter-group through plane walking to obstacle avoidance and it means people with Down syndrome probably use their residual abilities in the most efficient way to achieve the main goal of an efficient energy recovery.

The mechanical energy exchanges of normal subjects during walking have been investigated. Two groups of subjects including healthy children and healthy adults participated in this study. Kinematic data have been captured by a motion analysis system composed of 8 TV-cameras with an acquisition frequency of 50 Hz and retro-reflective markers positioned on main reference points of the body. Based on the estimation of mass and centre of mass of the main anatomical segments the kinetic and potential energy were computed. The total mechanical energy along a stride was compared to the kinetic and potential energy excursions as to obtain an index of energy recovery. Preliminary results show that significant differences exist between children and adults and walking efficiency is higher in adults.