Use of three-dimensional digital image correlation to evaluate mechanical response of prosthetic systems.

BACKGROUND AND AIM: The need of comfortable and safe prosthetic systems is an important challenge for both prosthetists and engineers. The aim of this technical note is to demonstrate the use of three-dimensional digital image correlation to evaluate mechanical response of two prosthetic systems under real patient dynamic loads. TECHNIQUE: This note describes the use of three-dimensional digital image correlation method to obtain full-field strain and displacement measurements on the surface of two lower limb prostheses for Chopart amputation. It outlines key points of the measurement protocol and illustrates the analysis of critical regions using data obtained on specific points of interest. DISCUSSION: The results show that the use of three-dimensional digital image correlation can be a tool for the prosthetist to optimize the prosthesis considering features related to the material and design, in order to bear with real patient-specific load conditions. Clinical relevance Three-dimensional digital image correlation can support decision-making on new designs and materials for prosthetics based on quantitative data. Better understanding of mechanical response could also assist prescription for appropriate prosthetic systems.

[Device to assess in-socket pressure distribution for partial foot amputation]. / Dispositivo para medir la distribución de presión en el encaje de prótesis para amputación parcial de pie.

A device for dynamic acquisition and distribution analysis of in-socket pressure for patients with partial foot amputation is presented in this work. By using the developed system, we measured and generated pressure distribution graphs, obtained maximal pressure, and calculated pressure-time integral (PTI) of three subjects with partial foot amputation and of a group of Healthy subjects (Hs) (n = 10). Average maximal pressure in the healthy group was 19.4 ± 4.11 PSI, while for the three amputated patients, this was 27.8 ± 1.38, 17.6 ± 1.15, 29.10 ± 3.9 PSI, respectively. Maximal pressure-time integral for healthy subjects was 11.56 ± 2.83 PSI*s, and for study subjects was 19.54 ± 1.9, 12.35 ± 1.48, and 13.17 ± 1.31 PSI*s, respectively. The results of the control group agree with those previously reported in the literature. The pressure distribution pattern showed clear differences between study subjects and those of the control group; these graphs allowed us to identify the pressure in regions-of-interest that could be critical, such as surgical scars. The system presented in this work will aid to assess the effectiveness with which prosthetic systems distribute load, given that the formation of ulcers is highly linked to the pressure exercised at the point of contact; in addition, these results will help to investigate the comfort perception of the prosthesis, a factor directly influenced by the stump's pressure distribution.

[Familiarization to treadmill walking in unimpaired Parkinson's disease patients]. / Familiarización de la marcha en banda sinfin de individuos con enfermedad de Parkinson.

Familiarization to treadmill walking in unimpaired Parkinson's disease (PD) patients is assessed, across multiple treadmill walking sessions. Thirteen PD subjects were enrolled into the study (Eight were in a moderate stage of the disease, and 5 in an advanced stage). PD subjects attended a progressive program consisting of 12 sessions of 20 min. Walking speed, cadence, step length and coefficient of variation were assessed. ANOVA test were used to evaluate progression of disease and time influence over familiarization. PD Subjects baseline characteristics did not differ significantly between both groups and typical dependencies over progression of disease and velocity were found for cadence, step length and coefficient of variation. However, we showed that some PD subjects may require longer familiarization times and that familiarization is an adaptation process which involves parameters as velocity, cadence and gait stability. A better definition of familiarization to treadmill is needed since some parameters such as step length does not change significantly while others such as cadence, coefficient of variation and intraclass correlation coefficient does. Therefore familiarization to treadmill walking should remain on measures of velocity, cadence, reliability and variability. However, a bigger sample size is needed in order to improve the results of the present study.

[Feasibility of the construction of a magnetorheological joint for a lower limb orthosis in valve configuration]. / Viabilidad de la construcción de articulación magnetoreológica para ortesis de miembro inferior en configuración de válvula.

Ortheses are devices that assist in the function of the limbs, contributing with stability and support to the involved joints. KAFOs (knee-ankle-foot orthosis) are mainly indicated for people with muscular or neural diseases that affect the lower limbs. The actual designs of knee hinges for KAFOs compromise the stability and mobility of the limb. In this work, it was tested the feasibility of a design for a knee hinge for KAFO that should be able to modify its mechanical resistance depending on the gait phase. Orthotics biomechanical criteria and gait biomechanical requirements were considered. It was proposed an electromagnetic system in order to modify the hinge damping. In the future, the system will be interacting with a magnetorheological fluid (MR) which can change its rheological properties when a magnetic field is applied, thus, reaching different damping constants with the designed hinge. The diameter of the internal pipes required for the MR fluid to freely circulate within the orthosis was established. It was observed that the original design of the proposed orthotic hinge is feasible; however, some proposals are presented in order to achieve a better performance of the orthosis.

[Dynamic plantar pressure distribution after percutaneous hallux valgus correction using the Reverdin-Isham osteotomy]. / Distribución de la presión plantar dinámica después del tratamiento corrective de hallux valgus mediante la ténica de Reverdin-Isham.

Percutaneous surgical techniques are suitable for the correction of the hallux valgus deformity. Satisfactory aesthetic and functional results obtained with the Reverdin- Isham osteotomy have been reported. The aim of this study was to describe dynamic plantar pressure redistribution after the correction of the deformity using this technique. A sample of 20 feet with mild or moderate hallux valgus was conformed and surgically treated using the Reverdin-Isham osteotomy. Clinical, radiological, surface and pressure assessments were performed pre and postoperatively. Postoperative mean (± SD) values of the American Orthopaedic Foot and Ankle Society (AOFAS) score, metatarsophalangeal, first intermetatarsal and proximal articular sect angles were 95.7 (3.3), 15.5° (5.4), 9.5° (1.5) y 5.3° (3.0), respectively. A significant decrease was observed in surface values of both lateral (P = 0.003) and medial (P = 0.001) masks of the forefoot. Mean pressure values of the lateral forefoot region denoted a significant increase (P < 0.001) while the medial forefoot region showed no change (P = 0.137). There is evidence that this particular surgical technique promotes a new plantar pressure pattern in the foot that might significantly favour the increase of the pressure observed under the lesser metatarsal heads and might not induce meaningful changes in the mean pressure registered under the first metatarsal head and hallux.

[Comparative study of the volume difference vs. healthy limb, morphological and population description in transfemoral amputees]. / Estudio comparativo de la diferencia del volume del munón vs. el miembro sano, descripción morfológica y poblacional en pacientes con amputación transfemoral.

Knowledge of the general characteristics and physical condition that keeps the transfemoral amputation stump to select and adapt appropriate type of prosthesis to restore a walking pattern amputee patient acceptable and useful design parameters set to propose new prosthetic systems. In this paper, the degree of difference between the volumes of the limb stump and healthy as well as morphological features occurred more frequently in the stumps of transfemoral amputees who were treated at the Laboratory of Orthotics and Prosthetics (LOP), Instituto Nacional de Rehabilitación (INR) in 2008. It captured all patients with unilateral transfemoral amputation left and right, over 18 years old, both sexes, use of hearing candidates were evaluated clinically and took three measurements of the circumferences at different wavelengths and the limb stump healthy, were calculated volumes of both sides using the mathematical model of the truncated cone and analyzed in three groups according to the level of amputation (proximal, middle and distal third). We obtained 49 patients, 39 men and 10 women, the difference stump volume compared to healthy limb volume per group were: 44.9% proximal third, middle third and distal 26.5%, 21.1%, the frequency of diagnostic data showed a stump right transfemoral amputees, due to metabolic, without use of prostheses, the most common morphological features indicate that the stump has a conical shape and size distal third, whose tissue is semi-flaccid consistency, the scar is not adhered to deep planes and shows a negative tinel, the mattress soft tissue is 2.15 ± 1.3 cm and physically presents a force level 4 in the clinical rating scale Daniels. The data are consistent with other studies comparing the percentage of the volume change with the percentages of reduced diameters transfemoral stump muscle, likewise agrees most amputees incidence of diabetes mellitus with other studies, cataloging it eat first cause amputation. The general description developed transfemoral stump-served in the INR will help in the process of manufacture of prostheses and prosthetic design new systems that you attend these needs.