Modeling foot rockers via functional calibration for use in clinical gait analysis.

BACKGROUND: Goal of this work is a quantitative description of Jacquelin Perry's rocker concept by locating the position of the heel rocker and the forefoot rocker within segments of the foot via functional calibration. METHODS: Two functional calibration tasks with the foot in ground contact were performed by ten typical developed adults and foot marker motion was captured. After applying a least-square method for constructing foot segments, their motion relative to the floor was analyzed via a functional algorithm. Resulting reference positions - namely the heel rotation center and the metatarsal rotation axis - were calculated. Further, the repeatability of the method and variability of outcome within the cohort was tested. RESULTS: The heel rotation center is located substantially posterior (25 mm) and slightly more inferior (5 mm). to the midpoint of the two markers placed medially and laterally on the calcaneus. Repeated measures reveal a variation of this location around 5 mm. The forefoot center is slightly more medial to the "toe marker" (DMT2) and substantially more inferior (19 mm). The metatarsal rotation axis is slightly tilted in the frontal and transverse plane against the metatarsal line given between markers on MT1 and MT5 with small variation in repeated measures (1-2°). SIGNIFICANCE: The determination of heel rotation center and the metatarsal rotation axis relative to foot segments can be determined with good repeatability and their location meet the intuitive expectation. Since they have a direct biomechanical meaning in the foot roll-over process in gait, they may be used for a more functionally oriented definition of foot segments potentially improving the calculation of foot kinematics and kinetics in future work.

Identification and interpretation of gait analysis features and foot conditions by explainable AI.

Clinical gait analysis is a crucial step for identifying foot disorders and planning surgery. Automating this process is essential for efficiently assessing the substantial amount of gait data. In this study, we explored the potential of state-of-the-art machine learning (ML) and explainable artificial intelligence (XAI) algorithms to automate all various steps involved in gait analysis for six specific foot conditions. To address the complexity of gait data, we manually created new features, followed by recursive feature elimination using Support Vector Machines (SVM) and Random Forests (RF) to eliminate low-variance features. SVM, RF, K-nearest Neighbor (KNN), and Logistic Regression (LREGR) were compared for classification, with a Majority Voting (MV) model combining trained models. KNN and MV achieved mean balanced accuracy, recall, precision, and F1 score of 0.87. All models were interpreted using Local Interpretable Model-agnostic Explanation (LIME) method and the five most relevant features were identified for each foot condition. High success scores indicate a strong relationship between selected features and foot conditions, potentially indicating clinical relevance. The proposed ML pipeline, adaptable for other foot conditions, showcases its potential in aiding experts in foot condition identification and planning surgeries.

Functional knee joint axis calibration and outcome after femoral derotation in patients with cerebral palsy.

BACKGROUND: Patients with cerebral palsy and increased femoral anteversion frequently show disturbing internal rotation gait which may be treated via femoral derotation osteotomy (FDO). A recent study monitored that hip rotation in gait may heavily depend on the procedure by which it is being determined. Traditional measures using the femoral epicondyles as reference for the knee axis (CONV) resulted in more severe transverse plane deviations compared to those using a functional method (FUNC) with relevant implications for treatment indication of FDO. RESEARCH QUESTION: Is mean hip rotation in stance (mHipRotSt) as obtained via FUNC the more sensitive measure for explaining functional changes after FDO compared to CONV method taking the femoral epicondyles as reference for the knee axis? METHODS: 3D-gait analysis before and one year after FDO was performed in fourteen patients including functional joint axis determination of the knee of which MR imaging was available in eight patients both pre- and postoperatively. Transverse plane gait parameters were calculated using both approaches (CONV, FUNC). Differences between examinations as well as between methods were determined. RESULTS: Changes in femoral anteversion as measured by MR reasonably well confirm the structural changes as measured clinically and intraoperatively. The average change in mHipRotSt across the group was substantially smaller than the structural change implies. Further, using the FUNC approach led to much smaller values compared to when using the CONV approach. We address this to a mismatch between the axes determined in each method. SIGNIFICANCE: In the presence of femoral deformity, the knee joint axis as determined via a functional method together with the conventional method (femoral epicondyles for the knee axis) allows to quantify knee rotation independent of torsional parameters of the tibia. It may therefore help to better quantify rotational malalignments in gait and improve decision making of FDO.

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.

Machine learning-based prediction of joint moments based on kinematics in patients with cerebral palsy.

Joint moments during gait provide valuable information for clinical decision-making in patients with cerebral palsy (CP). Joint moments are calculated based on ground reaction forces (GRF) using inverse dynamics models. Obtaining GRF from patients with CP is challenging. Typically developed (TD) individuals' joint moments were predicted from joint angles using machine learning, but no such study has been conducted on patients with CP. Accordingly, we aimed to predict the dorsi-plantar flexion, knee flexion-extension, hip flexion-extension, and hip adduction-abduction moments based on the trunk, pelvis, hip, knee, and ankle kinematics during gait in patients with CP and TD individuals using one-dimensional convolutional neural networks (CNN). The anonymized retrospective gait data of 329 TD (26 years ± 14, mass: 70 kg ± 15, height: 167 cm ± 89) and 917 CP (17 years ± 9, mass:47 kg ± 19, height:153 cm ± 36) individuals were evaluated and after applying inclusion-exclusion criteria, 132 TD and 622 CP patients with spastic diplegia were selected. We trained specific CNN models and evaluated their performance using isolated test subject groups based on normalized root mean square error (nRMSE) and Pearson correlation coefficient (PCC). Joint moments were predicted with nRMSE between 18.02% and 13.58% for the CP and between 12.55% and 8.58% for the TD groups, whereas with PCC between 0.85 and 0.93 for the CP and between 0.94 and 0.98 for the TD groups. Machine learning-based joint moment prediction from kinematics could replace conventional moment calculation in CP patients in the future, but the current level of prediction errors restricts its use for clinical decision-making today.

Are we overestimating internal rotation gait by conventional modelling?

BACKGROUND: The determination of the knee joint axis (KJA) via specific calibration movements has become a promising alternative to the conventional approach to determine this axis based on regression equations or directly via marker placement on bony landmarks of the knee. Since the orientation of the KJA may differ between methods, it has direct influence on hip rotation and may therefore influence clinical decision making in context of transverse plane gait deviations. RESEARCH QUESTION: Does a functional KJA calibration lead to clinically relevant differences in hip rotation estimates during gait compared to the conventional method? METHODS: 95 subjects (age: 19.9 years; BMI: 21.1 kg/m2), including 71 patients with potential rotation malalignment, were prospectively examined and underwent 3D gait analysis. For the conventional approach the KJA was determined by applying a knee alignment device, for the functional approach subjects were asked to perform two different calibration movements. Each procedure was performed twice. Mean hip rotation in stance (mHipRotSt) was determined following the conventional and the functional KJA calibration. RESULTS: Deming regression analysis for the comparison of conventional and functionally measured hip rotation revealed a systematic and substantial difference between methods (slope: 0.63; intercept: 0.31°). Measurement repetition with the knee alignment device revealed typical errors around 5°, whereas the functional methods lead to profoundly smaller errors around 1-2° with slightly inferior results for SQUAT compared to FLEX. However, when compared to conventional frontal plane video-taping, the conventional method seemed to reflect the more consistent results. SIGNIFICANCE: The systematic linear discrepancy in mHipRotSt obtained by a functional approach as compared to the conventional approach appears critical since patients with severe internal or external rotation gait may be misjudged in function when receiving corrective procedures such as femoral derotation osteotomy.

Estimation of a midfoot joint center in typically developed adults using functional calibration methods.

BACKGROUND: 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. RESEARCH QUESTION: Are functional calibration methods feasible for determining foot joint parameters and may they help for clinical interpretation of foot deformities? METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Functional hip joint centre determination in children with cerebral palsy.

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.

Biomechanical assessment of patellar tendon advancement in patients with cerebral palsy and crouch gait.

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.

Estimation of ankle joint parameters in typically developed adults using functional calibration methods.

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.

Long-term muscle changes after hamstring lengthening in children with bilateral cerebral palsy.

AIM: 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). METHOD: 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. RESULTS: MTL increased from E0 to E1 (p=0.004) and decreased from E1 to E2 (p<0.020). Hamstring lengthening velocity did not change. In the subgroup with short, not slow hamstrings, the increase in MTL was maintained at E2. INTERPRETATION: 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. WHAT THIS PAPER ADDS: 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 (p<0,020). 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 20o no pré-operatório, e PC antes do alongamento bilateral dos isquiotibiais (E0), em E1 e E2. CTM dos isquiotibiais (normalizado pelo comprimento da perna) e a velocidade foram avaliados pelo OpenSim. RESULTADOS: CTM aumentou de E0 para E1 (p=0,004) e diminuiu de E1 para E2 (p<0,020). A velocidade de estiramento do isquiotibial não mudou. No subgrupo com isquiotibial encurtado e não lento, o aumento no CTM foi mantido em E2. INTERPRETAÇÃO: O alongamento do músculo isquiotibial é um procedimento eficiente para alongar isquitotibiais encurtados e/ou lentos a curto prazo. O resultado desejado com a manutenção das alterações no pós-operatório no CTM do isquiotibial é atingida somente para isquiotibial curto e não lento no pré-operatório.

Benefits of an increased prosthetic ankle range of motion for individuals with a trans-tibial amputation walking with a new prosthetic foot.

BACKGROUND: 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. RESEARCH QUESTION: 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. RESULTS: 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. SIGNIFICANCE: 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.

Mid-term development of hamstring tendon length and velocity after distal femoral extension osteotomy in children with bilateral cerebral palsy: a retrospective cohort study.

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<0.05), knee flexion in swing only improved after DFEO+PTA (p<0.05). The improved knee flexion in stance and swing was maintained at E2. INTERPRETATION: DFEO led to a significant improvement in knee kinematics at E1 which was maintained at E2. DFEO seems to prevent recurrent hamstring tightness but does not lead to lengthened or fastened hamstrings. WHAT THIS PAPER ADDS: Distal femoral extension osteotomy (DFEO) does not change hamstring muscle tendon length. DFEO does not change hamstring lengthening velocity. DFEO leads to a significant improvement in knee kinematics. Changes in knee kinematics after DFEO can be maintained at mid-term. DFEO seems to prevent recurrent hamstring tightness.

What is the price for the Duchenne gait pattern in patients with cerebral palsy?

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.

Sound side joint contact forces in below knee amputee gait with an ESAR prosthetic foot.

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.

Mechanical energy assessment of adult with Down syndrome during walking with obstacle avoidance.

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.

Differences in center of pressure trajectory between normal and steppage gait.

BACKGROUND: This pilot study aimed to assess the differences in center of pressure trajectory in neuropathic patients with steppage gait. Steppage gait has previously been evaluated by several biomechanical methods, but plantar pressure distribution has been much less studied. The purpose of this study was to analyze the changes in center of pressure trajectory using a force plate. METHODS: The steppage gait group was selected from the patients using drop foot brace (25 male) and the control group was selected from Isfahan university students (20 male). They walked at self- selected speed at a mean of ten trials (+2) to collect the center of pressure using a force plate. Center of pressure patterns were categorized into four patterns based on the center of pressure displacement magnitude (spatial features) through time (temporal features) when the longitudinal axis of the insole was plotted as the Y- axis and the transverse axis of the insole as X- axis during stance phase. RESULTS: The horizontal angle measured from center of pressure linear regression was positive in the control group (4.6 ± 2.4) (p < 0.005), but negative in the patient group (- 2.3 ± 1.6) (p < 0.005). CONCLUSIONS: The finding of this research measured center of pressure trajectory in steppage gait over time, which is useful for designing better shoe sole and also orthopaedic device and better understanding of stability in patients with drop foot.