Feature Extraction of Foot Movement Based on Plantar Pressure Distributions / 医用生物力学

Objective To analyze the statistical behavior of plantar pressure distribution, extract the characteristics of foot movement, and provide references for application of gait recognition in medical clinical diagnosis, rehabilitation training and public health. Methods The collected foot pressure data were prepossessed, statistical analysis on the data was performed, the footprint reconstruction was realized, and the pressure distribution rates of the footprints, segmented regions and each region were compared and analyzed, so as to decompose the foot motion characteristics. Results Based on the cross point of pressure peak curve in different regions, the plantar region was divided into toe region, metatarsal region, arch region and heel region, which could accurately extract the foot movement characteristics. Conclusions The peak plantar pressure is used to extract the characteristics of foot movement, which is divided into landing stage, whole foot contact stage, heel tiptoe stage and ground off stage.

System and Function Study of Limb Compression after Total Knee Replacement / 医用生物力学

Objective A three-dimensional （3D） printing precise pressure device was designed specifically targeted at cambered limbs according to the requirement of postoperative rehabilitation of total knee replacement(TKR), and its effectiveness and safety was verified by finite element analysis. Methods Based on gastrocnemius muscle of lower limbs as the pressurized objects, the precise pressure device was designed, which contained an air pressure generating module, an inflatable airbag and a 3D printing brace. Through the closed loop control algorithm, the device stably supplied different pressures in the airbag. Distributed pressure data of the airbag-skin within contact surface were collected under different experimental conditions and imported into biomechanical simulation software which combined CT images to reconstruct 3D model of the lower limb mechanics. Finally, the effective compression area fraction and the joint micro-motion angle under each condition were obtained, to verify the effectiveness and safety of the system. Results Using generally preferred 4 cm-size offset and 4-barrel airbag configurations, under different intracapsular pressure of 5.32，6.65，7.98，9.31，10.64 kPa, the simulated knee joint micro-motion angles were 5.3°, 6.1°, 7.2°, 9.5°, 10.6°， respectively, and the effective compression area fraction could be up to 90-8%-95-2%. Conclusions For the optimized scheme, the dynamic range of joint micro-motion angle and the effective compression area fraction caused by different airbag pressure values were the best and met the design requirements of effectiveness and safety. The research findings can contribute to analyzing the influence of compression system on limb biomechanics, which are of great significance for effective and safe rehabilitation training after TKR.

Plantar Pressure Asymmetry in Patients Six Months after Surgical Treatment of Calcaneal Fractures in Adults.

Aim: To compare plantar pressure distribution and contact time in patients in month 6 following operative treatment of calcaneal fractures. Study Design: Walking on the tensometric platform. Place and Duration of Study: Regional Hospital, Trauma Centrum, between September 2014 and October 2015. Methodology: Gait analysis was carried out on seven patients (38±9 years; 1.79±0.05 m; 83±8 kg). Measurements were made using a pedobarography platform. The factors observed comprised: total contact time (CT), peak pressure (PP), maximum vertical force (Fz), heel contact time (CT-heel), peak pressure under the heel (PP-heel), and the force-time integral (FTI). The analysis was based on the data from both the healthy and the affected lower limb; values for symmetry index (SI) were computed. Results: Out of 7 patients, all patients with a longer contact time on the healthy feet were documented. The healthy limbs demonstrated peak pressure values that were predominantly higher beneath the heel, and under the first metatarsus head and under the big toe. On the affected limbs centre of pressure line shifted laterally. Foot contact was applied more often on the outer side of the foot. Not a clear trend was found in the contact time beneath the heel with the ground when 4 patients shortened the duration of the heel contact on the affected limb. Conclusion: The observed patients still show significant lateral changes in dynamic parameters, which is also reflected in the duration of the individual phases of the gait cycle. The calculation of the index of symmetry for the tracked variables showed significant differences between healthy and affected limbs, although all the patients had returned to their working environments at the time of the measurement. This pilot study is a starting point for future work and co-operation between the University and the Trauma Centrum.

Design of a flexible sensor array for pulse diagnosis in traditional Chinese medicine / 国际生物医学工程杂志

Objective To acquire high spatial resolution two-dimension pulse pressure distribution for objectifying research of pulse diagnosis in traditional Chinese medicine.Methods A sensor array with flexible packing was designed and implemented.The array was formed on a circle substrate with 37 silicon piezoresistive pressure sensors,which were distributed as equilateral triangles with 1.95 mm pitch.The diameter of the substrate was 15 mm.By using flexible packing,the array had the hardness similar to that of human finger,which made this method closer to the traditional Chinese diagnosis.After differential amplifying,37-way pulse pressure signals were digitalized and reconstructed to obtain the pulse pressure distribution.Results With the application of the sensor array,the pulse pressure signals were measured and transformed into pulse pressure distribution.Conclusions The experimental result contains the relevant characteristics of traditional Chinese pulse diagnosis' description,providing a new way for objective study of traditional Chinese pulse diagnosis and further study.

Evaluation of Pressure Reduction of Pressure-control Ulcer Cushion / 中国康复理论与实践

@#Objective To evaluate the decompression performance of anti pressure ulcer cushions with different materials and structures. Methods The common cotton cushion, sponge cushion, 3D fabric cushion, and upper 3D fabric and lower sponge cushion were analyzed by XSensor pressure sensor testing system. The pressure distribution, the pressure peak and the average pressure were analyzed to compare the decompression performance and the comfortable capability. Results and Conclusion The upper 3D fabric and lower sponge cushion can en-sure the decompression performance with excellent permeability. Both decompression and air comfort permeability should be the future di-rection of ulcer cushions research and production.

Assessment of Three Alternating Pressure Sequences Applied to a Dynamic Cushion to Relieve Pressure on Seating Areas / Evaluación de tres secuencias de inflado alternantes aplicadas a un cojín dinámico para la liberación de presión en el área de sentado

Pressure ulcers are injuries to the skin and/or underlying tissues caused by prolonged high pressures on supporting body areas, they affect mainly people with poor mobility that have stayed in seating position for a long time. Reducing the amount and duration of pressure has been widely accepted for minimizing the risk of formation of pressure ulcers. Recently, dynamic cushions have been developed to relieve pressure on supporting areas; nevertheless, there is no sufficient information about the adequate characteristics of alternating sequences for pressure ulcers prevention. Therefore, the aim of this work is to explore three sequences of alternating movements designed for an air cell cushion by comparing pressure redistribution on supporting areas when applied on healthy volunteers. The purpose of these sequences is to redistribute the pressure over a larger contact area. To evaluate the effect of the alternating sequences, eight healthy volunteers were asked to sit on the air cell cushion, and to try the three alternating sequences for 12 minutes, 2 minutes on static mode and 10 minutes on alternating mode. A parameter for quantitative assessment of alternating sequences was proposed in this work by determining the coefficient of variation of interface pressure. Furthermore, the percentage of relative change of coefficient of variation was computed for evaluating performance of the alternating sequences comparing to the static mode. It was found that the three proposed strategies maintained values of interface pressure lower than previous work. Additionally, the relative change allowed to differentiate the effects of alternation of each sequence showing the second strategy as the most effective. The results are encouraging for further studies in subjects who require a wheelchair for mobility.

Las úlceras por presión son lesiones en la piel y tejidos subyacentes, causadas por presiones excesivas y prolongadas en las superficies de apoyo del cuerpo. Estas lesiones afectan principalmente a personas con poca movilidad física, como aquellas que permanecen sentados por largos periodos. Para disminuir el riesgo del padecimiento de estas lesiones, se ha recomendado como punto de partida reducir la magnitud y el tiempo de acción de las presiones en las zonas de apoyo. Se han desarrollado cojines dinámicos para sillas de ruedas, los cuales generan movimientos alternantes en las diferentes zonas de apoyo, producido por la inyección de aire, con el fin de disminuir las presiones en esas zonas. Sin embargo, no se han encontrado referencias de las características adecuadas de las secuencias de movimientos alternantes para prevenir la aparición de esas lesiones. El propósito de este trabajo es evaluar tres secuencias de movimientos alternantes diseñadas para un cojín de aire. La evaluación se realizó comparando la distribución de presiones en zonas de apoyo antes y durante la aplicación de estas secuencias alternantes en personas sanas. Las secuencias propuestas se aplican para el inflado y desinflado de celdas que forman el cojín y fueron diseñadas con el objetivo de distribuir las presiones en un área mayor de apoyo. La prueba se realizó en 8 sujetos sanos, con un tiempo de estudio de 12 minutos para cada secuencia diseñada; 2 minutos en modo estático y 10 minutos en modo alternante. Se propuso determinar el coeficiente de variación para evaluar de forma cuantitativa el efecto de las secuencias alternantes sobre la presión de interfaz. Además se calculó el porcentaje de variación relativa del coeficiente de variabilidad entre los modos basal (estático) y alternante como una herramienta para evaluar el desempeño de las secuencias propuestas en relación a la presión de interfaz. Se encontró que las tres estrategias mantuvieron presiones de interfaz por debajo de los valores reportados en trabajos previos. El porcentaje de variación relativa permitió diferenciar el efecto de la alternancia de cada una de las secuencias propuestas, mostrando la segunda estrategia como la más efectiva. Los resultados obtenidos son alentadores para continuar el estudio en sujetos que requieren una silla de ruedas para su movilidad.

Simulation for internal structure of proximal tibia in both normal and valgus knees / 医用生物力学

Objective To simulate the internal structure of proximal tibia in both normal and valgus knees. Methods The internal structure of proximal tibia under normal mechanical environment was simulated using quantitative bone remodeling theory combined with finite element method. Based on this structure as the initial model and the changing pattern of pressure distributions on tibial plateau in valgus knee, the internal structure of proximal tibia in valgus knee was simulated with the action point of resultant force on the lateral tibial plateau. Results The simulated distributions of bone mineral density (BMD) were compared with the real tibia, and found the simulated results highly consistent with the actual ones both under normal mechanical environment and in valgus cases. Conclusions The method and the load distributions adopted in this study can accurately simulate and predict the internal structure of proximal tibia, thus could be served as the basis for further study on periprosthetic bone remodeling behavior after the total knee arthroplasty.

Contact mechanics of non-spherical hip joint replacements / 医用生物力学

Objective Due to the limitation of manufacturing techniques, possible design optimization selecting and influence of its wearing in clinical application, the bearing surface of hip joint replacements is presented as non-spherical geometry, and the finite element method can be used to study the contact mechanics behavior in such kind of non-spherical hip joint replacement. MethodsThe reconstructing of non-spherical articular surface based on spherical-grid-data model (SGDM) was developed to investigate the effect of contact mechanics of an ellipsoidal head against a spherical cup in a typical metal-on-metal hip joint replacement. Results The maximum contact pressure of the non-spherical bearing was decreased effectively, and meanwhile the contact area was increased when curvature radius of the ellipsoidal head around the centre of the contact zone was increased, while the effects of the cup inclination angle on the maximum contact pressure and contact area of the non spherical bearing under the same load showed relatively small, but the contact pressure distributions were different. Conclusions A well-controlled non-sphericity can improve the magnitude and distribution of contact pressures on metal-on-metal hip joint replacements. In addition, the developed model and evaluation method in this paper can be used for simulation of dynamic contact and wear prediction of non-spherical hip joint replacements.

Comparação da distribuição de pressão plantar em sujeitos com pés normais e com pés planos durante a marcha / Comparison of plantar pressure distribution in subjects with normal and flat feet during gait

O objetivo do estudo/pesquisa foi verificar possíveis relações entre a queda do arco longitudinal medial, mensurada em situação estática pela altura do osso navicular e um conjunto de variáveis relacionadas à distribuição de pressão plantar, mensuradas em situação dinâmica. Participaram do estudo 11 (onze) sujeitos do gênero masculino, comidade média de 21 anos ± 3 anos, massa corporal 74 kg ± 10 kg e estatura 175 cm ± 4 cm. Para aquisição dos dados de Distribuição de Pressão Plantar (Pico de Pressão, Pressão Média, Área de Contato e Carga Relativa), foi utilizado o Novel Emed-AT System com uma taxa de amostragem de 50 Hz e para análise da Altura do Navicular para classificação dos sujeitos em grupos, foi utilizado o protocolo Navicular Drop Test proposto por Brody (1982). Os dados foram comparados a partir dos resultados da aplicação da estatística não paramétrica através do teste U de Mann-Whitney com p ? 0,05. Os resultados demonstraramque os grupos foram significativamente diferentes entre si, na região do mediopé, em todas as variáveis analisadas, sendo que foram encontrados os maiores valores médios no grupo dos indivíduos com os Pés Planos. Também apresentaram diferenças significativas na variável Área de Contato, Carga Relativa, Pico de Pressão Plantar e Pressão PlantarMédia quando comparados os grupos. Os resultados demonstram a importância que se deve dar aos sujeitos com pés planos, pois alterações na Distribuição de Pressão Plantar estão associadas ao surgimento de desconforto e também de lesões.

The aim of this study was to determine the possible relationship between loss of the normal medial longitudinal arch measured by the height of the navicular bone in a static situation and variables related to plantar pressure distribution measured in a dynamic situation. Eleven men (21 ± 3 years, 74 ± 10 kg and 175 ± 4 cm) participated in the study. The Novel Emed-AT System was used for the acquisition of plantar pressure distribution data (peak pressure, mean pressure, contact area, and relative load) at a sampling rate of 50 Hz. The navicular drop testproposed by Brody (1982) was used to assess the height of the navicular bone for classification of the subjects. The results were compared by the Mann-Whitney U test, with the level of significanceset at p ? 0.05. Differences were observed between the two groups in the mid-foot regionfor all variables studied, with the observation of higher mean values in subjects with flat feet. There were also significant differences in contact area, relative load, peak pressure, and mean pressure between groups. The present study demonstrates the importance of paying attentionto subjects with flat feet because changes in plantar pressure distribution are associated with discomfort and injuries.

Fraturas intra-articulares do calcâneo: análise clínica e biomecânica / Intraarticular calcaneal fracture: a clinical and biomechanical analysis

OBJETIVO: Verificar as variáveis de distribuição da pressão plantar de pacientes submetidos a tratamento cirúrgico de fratura de calcâneo e correlacioná-las com duas diferentes vias de acesso cirúrgico. Métodos: Os autores estudaram 15 pacientes com idade entre 20 e 53 anos (média de 40,06 anos) que apresentaram fraturas intra-articulares do calcâneo, submetidos ao tratamento cirúrgico por duas vias de acesso cirúrgico, a via lateral e a via do seio do tarso. Avaliaram a distribuição da pressão plantar, correlacionando essas variáveis com as duas vias de acesso. A avaliação da distribuição da pressão plantar foi rea-lizada através do sistema Pedar (Novel, GmbH, Munique, Alemanha), verificando o pico máximo de pressão do retropé e do antepé do lado fraturado e do lado normal. RESULTADOS: A média das pressões máximas dos plantigramas do retropé dos pés operados pela via de acesso lateral e pela via curta não apresentou diferença estatística entre as duas vias de acesso (t = 0,11; p = 0,91), bem como a média das pressões máximas dos plantigramas do antepé também não mostrou diferença estatística significativa (t = -0,48; p = 0,64). CONCLUSÃO: Os autores concluíram que não houve diferença estatística entre as médias dos picos máximos de pressão do retropé e do antepé do lado operado, comparados com o lado normal, bem como não houve diferença estatística dessas variáveis comparadas com a via de acesso cirúrgico utilizada.

OBJECTIVE: Verify the variables of plantar pressure distribution of patients submitted to surgical procedure for calcaneal fracture, and correlate them with two different surgical approaches. Method: The authors studied 15 patients between 20 and 53 years of age (average 40.06 yrs.) who had intra-joint calcaneal fractures, submitted to surgical treatment by means of two different approaches: the lateral and the sinus tarsi. The authors checked the plantar pressure distribution by correlating these variables with the two different surgical approaches. The plantar pressure distribution was assessed using the Pedar System (Novel, Gmbh, Munich, Germany), by checking the maximum peak of the hindfoot and forefoot pressure on the affected and the normal sides. RESULTS: the mean maximum pressure of the hindfoot plantigram in both approaches showed no statistical difference (t=0.11; p=0.91), as well as the mean maximum pressure of the forefoot plantigram (t=-0,48; p=0,64). CONCLUSION: The authors have concluded that there were no significant statistical differences between the average maximum peak of the hindfoot and forefoot pressure on the affected side as compared to the normal side, and these variables have showed no differences when compared to the surgical approach used.

The Changes of Foot Pressure Distribution in Spastic Cerebral Palsy with Equinus Deformity following Corrective Surgery

OBJECTIVE: The aim of this study was to identify the changes of pressure distribution on the foot after orthopaedic surgery for equinus deformity in spastic cerebral palsy using F-scan system. METHOD: Twenty-one children with spastic cerebral palsy were participated in this study. They had equinus deformity on foot and received soft tissue surgery. Pressure distribution on foot was measured before and after operation using F-scan system (Tekscan Inc., USA). Paired t-test was used in comparison of preoperative and postoperative measurements for statistical analysis. RESULTS: Total contact area, contact length, midfoot and hindfoot contact width were significantly increased after operation. Relative impulses of medial and lateral forefoot were significantly decreased and relative impulse of hindfoot significantly increased after operation (p<0.05). Anteroposterior distance of center of pressure (COP) and velocity of COP were significantly increased and mediolateral distance and slope of COP were significantly decreased after operation (p<0.05). CONCLUSION: This study revealed that patterns of foot pressure distribution during walking were significantly improved after operation. Therefore, these findings suggested that F- scan system might be useful for surgical outcome measurement for foot deformities in the children with spastic cerebral palsy.

Pressure Distribution on the Human Body Surface by Position Change under General Anesthesia: Preliminary report / 대한마취과학회지

BACKGROUND: While sleeping, humans frequently change their position; this is done to avoid direct and excessive pressure on the body surface, and is considered to be very important for the prevention of pressure sores. A patient who is under general anesthesia, however, cannot perform this reflex movement; maintaining the same position during an entire operation causes concentrated pressure on specific body surfaces, and this may result in complications such as allopecia, back pain, pressure sores and peripheral nerve damage. Because little is known about the relationship between surgical position and pressure on the body surface, position is in most clinical situations decided on the basis of experience and informed guesswork. In order to qualitatively and quantitatively determine weight-bearing areas, pressure on the body surface of patients was evaluated under general anesthesia. METHOD: Ten patients scheduled for elective surgery were selected for this study. They were all aged over 20 and ASA class 1. A mattress equipped with a force sensing resistor was placed on the operating table and used to determine pressure on the body surface. Pressure was measured before and after anesthesia was induced in the supine, lateral and prone position. The signal generated by this mattress was processed using an analogue-digital (AD) converter, then displayed as pressure distribution on a computer screen. Pressure points were compared qualitatively, and for quantitative measurement were digitally expressed. 'Pressure' here is mean pressure at each point calculated among ten patients. RESULTS: In the supine position, pressure was concentrated on the shoulder and sacral areas. Pressure distribution in these areas was 29.8% (shoulder) and 26.0% (sacral area) before anesthesia was induced, and 20.3% (shoulder) and 25.8% (sacral area) after induction. In the lateral position, the shoulder and trochanteric areas were identified as the main weight-bearing areas; pressure distribution was 11.2% and 8.1% before induction, and 21.6% and 15.3% after induction, respectively. In the prone position, the chest and abdomen were the main weight-bearing areas. Pressure distribution in the chest area was 30.8% before induction and 24.4% after. Operating table tilt in each surgical position also produced marked changes in pressure distribution. CONCLUSIONS: In each surgical position, weight-bearing areas were qualitatively and quantitatively determined before and after anesthesia.