The 5th IEEE International Conference on E-Health and Bioengineering - EHB 2015 Grigore T. Popa University of Medicine and Pharmacy, Iaşi, Romania, November 19-21, 2015
Flat foot composite dynamic clamp as a 24 hours correction device for children Dimitriu Bogdan1, Lungu Elena2, Prisecariu Bogdan3 Affiliation 1: P&O laboratory, Ortobiomek, Iasi, Romania,
[email protected] Affiliation 2: Statistics and management, Ortobiomek, Iasi,Romania,
[email protected] Affiliation 3: Sport departement, UMF “Gr.T.Popa” Iasi, Iasi, Romania
Abstract — Flat foot correction is achieved with two types of medical devices, inserts or orthotics. Insoles are medical devices that give results only with footwear. Flat foot correction approaches focuses on repositioning the arch of the foot rather than correcting the heel deviation and forefoot abduction. We consider repositioning flat foot heel and forefoot by using a composite clamp that allows to worn throughout the entirely day with or without shoes. The clamp allows movement of all the foot joints without restrictions and can be use even for the night correction. Correction of the subtalar joint position in relation with the forefoot allows reposition of the functional arch. Keywords—flat foot, composite, design, clamp
I.
INTRODUCTION
Flat foot is a very common pathology of the foot for childrens. During treatment, it is important to know for how much time the device acts on the problem. Normally, a child wear shoe for a period up to 6 hours. From this time, only for a period of 2-3 hours we can say that the child is really walking or running. In walking, 40% of time represents the maximum period for heel contact. Thus, only for a maximum of 72 minutes it is consider that an insert correction occurs on a flat foot. For this reason, we created a clam that allows ankle correction and posture correction for foot bones for a maximum of gait phase but also for sleeping time. Correction of the flat foot considers correction of the calcaneovalgus, calcaneoretroposition, posturing of navicular bone, talus bone plantarflexion and forefoot abduction. Actual devices do not solve the degree of overpronation. The design of the clamp allows correction during sleeping time and gait time (with or without shoes). This period of weariness is increased, and so, the effectivness of the correction increases. Thirty patients for trials for the device were performing test. A number of 1100 static and dynamic analyses were recorded with Biomech2011 software.
The solution is possible using a combination of materials like CTC (carbon thermoformable composites) that allows fast modifications of the orthotics. This deformation of the subtalar joint under weight means a deformation in two direction – valgisation of the calcaneous in frontal plane and posterior movement of the calcaneous in sagital plane; the abduction of the forefoot and talus flexion complement and follows. In genereal, insole tends to support the arch of the foot relying on shape and compression resistance of the insole arch shape. Applying a force on the arch area can determine inversion without any significant correction in the subtalar joint. A dynamic evolution of the flatfoot is valgus of the calcaneous, followed by the talus plantar flexion, followed by the navicular bone down movement or dislocation. It is normal to start the correction of the flatfoot with reposition of the calcaneum. The reposition using a wedge on the medial side of the heel is not the best choice if we consider the soft tissue movement. The height difference that occurs between the two feet become a problem to consider (the technician has to reconsider the intervention for height equilibrium on the opposite foot). In addiction, it is necessary to consider the movement up and down of the heel in the shoe during the gait. Each movement considers reposition of the heel. This is possible only when a high collar around the heel is used. Physics show that for the correction of the joint, pushing on a point needs two others fixes points. Applying a wedge on the medial side of the calcaneum will tend to roll the surface rather then aligning with the talus. If a force is applied lateral inferior and a counter force medial superior, than, an aligniament phenomenon occurs. The correction of the flat foot needs to consider also the reposition of the medial foot. This means that an adduction intervention is necessary. An insole is not capable of this, and a three points system that continues the heel clamp is necessary.
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The clamp proposed allow correction for the heel and allow realigniment for the medial foot. II.
METHODS AND COMPARISONS
For the correction of the flexible flat foot, the device is designed for two purposes: the reposition of the heel and reposition of the midfoot. The foot is evaluated using a Biomech2011 software and a capacitive sensor force plate with a matrix of 50x50 sensors. The evaluation is static and dynamic. The recording shows the degree of abduction of the midfoot and the maximum pressure for the heel area. For the construction of the clamp we used a hybrid composite sheet from LPET and bidirectional weaved carbon fiber (3k) covered with 1mm rtv silicone 20 shore. Three stages cast is used as reference shape of the clamp. The composite sheet is modeled at 160 degree Celsius. To form the clamp, a precut composite is thermoformed using a heat gun. A termic treatment is used before and after the forming for a uniform distribution of the LPET. Certain areas of the clamp are reinforced with CTC stripes for dynamic resistance during gate. For the medial maleolli side, a silicone cushion material is used.
the step size, so the contact point between the heel and the wedge varies. The heel is a specialized structure for damping and one of its structure – the fat layer – play an important role in its positioning under load. The fat layer is mobile and slips under the weight of the heel. The wedge amplifies the phenomenon of the calcaneum deviation because of the fat layer sliding to the medial side. Considering the connective tissue, the only element that opposes the heel bone to move in valgus position is the skin. On the other side, tension in the skin will relax its structure in time and no opposition for the heel will be. Three-point correction system based on the push to the lateral side of the heel with two other counter force points on the retronavicular medial and tuberosity of the fifth metatarsal, laterally. Lateral support surface area of the fifth metatarsal play a role in correcting foot abduction. We emphasize that the support in the medial plantar vault is not all over the medial arch but only retronavicular. According to the principle of constant volume of a rigid body, applying a pressure in one area of the body determine the expansion in other area of the same body. For this reason, pressures areas for foot correction are not on the same direction and plane of forces. The foot is a dynamic structure and so his volume shape.
Fig.1. A. 3 points correction versus B. wedge correction
Classical technical correction in valgus deviation of the calcareous using a wedge is effective in orthostatic position and landing heel does not guarantee the same point of contact. The wedge tends to roll the heel under the weight, requesting a form of shock in the subtalar joint. Ideally, the subtalar joint is to be already positioned before heel contact with the ground. Correction using the wedge does not take into account that when walking there is an alternation, physiological, crossing the position of the heel from valgus in the varus depending on the degree of flexion of the knees and thighs or function of
Fig.2 A – dorsal view of clamp draw lines, B – plantar view of clamp draw lines, C – lateral view of clamp draw lines, D – posterior view of clamp draw line.
The major tests for the clamp are: - functional capacity for correction - stability during gait - comfort - capacity to be remodeled - cost of production - technique of production
III.
ORTHOTICS COMPARISON TREATMENT TIMES
Using classical correction inserts involves using a pair of proper shoes. One insert without proper shoe may not exercise effect. In general, the best possible correction using insoles is a biomechanical trick, namely heightening the heel area so as, to have a slight plantar flexion. is well know that in plantar flexion an inversion of the heel follow. The major problem that arises is that once the center of gravity moves forward the pressure on the forefoot increase and accentuates forefoot abduction by increasing pressure on the metatarsal head of the big toe. An analysis of time a child carries insoles, so is wearing shoes, shows that the average time is around eight hours. From these eight hours, a maximum of two hours represent the time spent in upright position. Insoles take effect only under weight. It can be consider an average time of one hour for walking or running, from which only 40% of stress lay on the heel. Overall, is deducted an average of 31% of the effective time of eight hours of maximum correction. If we consider the lift of the heel for a more efficient correction that implies a reduction of mobility of the heel, than, the effectivness of the insole is less than 30%. The flat foot orthosis are AFO types. A characteristic of them is that locks the foot and ankle after a correction model. The joint is in a fixed position anatomically correct. The foot can perform flexion in the ankle joint or phalango-metatarsal joints, but do not allow mobilization in the remaining joints. The foot is a growing dynamic element that requires mobilization of ligaments and tendons or else secondary complications arise. Foot joints need to mobilize synovial fluid during motion. The increase in volume of the foot during walking or running, inside the shoe or orthotic, create an increase in pressure on the area between the foot and the shoe/orthotic that lead to circulatory deficiency. The efficiency of AFO orthotics over time is considerably higher than the efficency of insoles. The main problems are the difficulty to fit the orthotic inside the shoe when they are made from thick plastic, the rigidity of the material in the heel area that need to be covered with soft material on the outside area and modified in order to copy the anatomical heel roll on impact. A rigid plastic heel affects the ankle and knee joints response during gait. Because the foot orthotics embed the foot, a period of six hours of wearing require at least three hours of rest without orthotics for rebalance of blood circulation. AFO orthotic allow correction during the sleep time. One of the drawbacks of the AFO is the immobilizations of rear and midfoot movements. The clamp we proposed, intend to solve this problems by correcting the foot posture dynamically without movement restrictions. That means an increase for mobility, comfort and efficiency. It is important to offer to a child with flat foot,
during the growing period, a medical device that correct but that is comfortable also. The clamp is a device that encircles or grasps the surface of the foot or any other anatomical region, in order to realign the joint position. In orthodontic practice, the clamp is a metal wire device with memory of shape. In orthotics, because of the large amount of force encountered, the composite materials are the most recommanded because of them capacity to return the energy after a deformation. In addition, the contact with the skin is of great importance. That is why a cotton socket, a well-accepted material for the skin, is a good choice as a liner between the skin and clamp. The thickness of the clamp do not exceed the value of 1mm. That is why the clamp fit without problems in the shoe. The value of the thickness offers a good degree of acceptance in both conditions, shoeless and with shoe. The surface of the clamp is covered with a very thin layer of silicon or polyurethane for better contact. The elastomers increase the friction and by this the stability of the device on the anatomical part. Additional velcro may be attached to control the stability of the clamp for very difficult cases. The silicone needs to be high temperature resistance because thermoforming modification may appear with time. IV.
MAKING STAGES OF THE CLAMP
The production of the clip starts with an evaluation of the patient foot. The heel is aligning in neutral subtalar position using a laser beam. The areas of tissues that not deform or wrinkle during mobilization the ankle are point with a felt pen. These areas are those that will not change dimensionally during walking. For a small force to shift medially the heel, a big surface is necessary. That is why all the lateral area of the heel is necessary. The deformation of the tissue is checked. This is necessary for the mold modification. The posterior side of the heel is covered and used to push the heel anteriorly. In flat foot, the heel move backward because of the triceps predominance over the tibialis muscle. The navicular bone is identified and used as reference for arch height and for heel containment in normal anteroposterior position. For this reason, a small recess in the plantar anterior limit of the heel is used. Once these first lines are identified, the first cast procedure start with patient positioned in orthostatism. When the cast is dry and hard enough, the lateral fifth metatarsus head is identified and pushed using a counter force on the navicular bone to correct the forefoot abduction. The laser beam is used to identify the aligniament of the anatomical line that pass from the midle of the anterior face
of the ankle through the space between the first and second rays. This part of the procedure is more difficult if the reconstruction of anterior arch is necessary. When the positive and negative cast steps are over, a sheet of 0.7mm precut CTC is drawn over the model. The CTC model goes in an oven for curing for about six hours. Once the curing process is finished, the ctc is cooled and checked for flexibility on the patient. The final step is to cover the clam with silicone or polyurethane resin for better acceptability and resistance.
V.
DISCUSSIONS
The clam represents a new approach for flat foot treatment. The effective form is distinguished by a high level of acceptance and comfort and by the opportunity to remodel by heat treatment according to the evolution of correction. The clam offer the posibillity for correction during the night when growing process is most active and during the day period when ligaments modify in structure according to joint mobilization.
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