RU2055549C1 - Frame of artificial foot - Google Patents

Abstract

FIELD: medical facilities. SUBSTANCE: frame of artificial foot has ankle 1, wavy spring 4 with two troughs of wave in calcanel and metatarsophalangeal regions and wave tops in talocrural region, damper 3 located between ankle and spring. EFFECT: provision of artificial foot whose operation precisely conform to operation of normal foot. 6 cl, 2 dwg, 1 tbl

Description

 The invention relates to medical equipment, namely to lower limb prostheses.

 Known artificial foot containing the ankle, metatarsophalangeal hinge, heel, front, shock absorber and fasteners. At the same time, a hinge is installed on the ankle, the axis of which coincides with the physiological axis of the Shoparovsky joint. A two-arm lever is located on the hinge axis, one shoulder of which is connected to the metatarsophalangeal hinge, and a coil spring is located under the other shoulder in the heel of the foot. The disadvantages of the known prosthesis are the relative complexity of the design, low manufacturability in manufacturing, the inability to simulate the rear elastic shock.

 Also known is a shin prosthesis on a truncated limb containing a foot and an elastic membrane, in which an ankle with a movably articulated skeleton of the foot is enclosed. The disadvantage of this prosthesis is poor depreciation capabilities, lack of stability when walking.

 The closest in technical essence to the claimed artificial foot frame is the construction of a known frame containing a shell with a filler, ankle and spring, which is made of two branches, one of which repeats the curvature of the natural arch, and the free end of the other branch is in contact with the first in the metatarsus region phalanx joint. The disadvantages of the prototype include the difficulty in manufacturing, the impossibility of the most accurate modeling of the functions of the natural human foot, the absence of the effect of resistance to spreading, which leads to lameness, shortening of the step and instability when walking.

 The invention is aimed at solving the problem of creating an artificial human foot, the functionality of which would most accurately correspond to the functionality of the foot to normal.

 The aim of the invention is to create a design that, in contrast to the known one, is able to simulate the spring function, the effect of flattening and resistance to destruction of the foot is normal, to accumulate the deformation energy of the prosthesis elements necessary for the prosthesis to perform a back push in order to bring the patient's energy level when walking to normal.

 The problem is solved by that, and the goal is achieved by the fact that the skeleton of the artificial foot contains an ankle, a wave-shaped spring with two troughs of the wave in the heel and metatarsophalangeal region and the tops of the wave in the gelled part of the foot, a damper located between the ankle and the spring.

 A distinctive design feature is the following. The spring is made with stiffness varying in length, decreasing to its ends. A cantilever element located under the ankle and attached to its ends is introduced into the artificial foot frame. A cantilever element located under the ankle and attached to it is introduced into the artificial foot frame. The spring is attached by the top of the wave to the cantilever element, which is made with stiffness variable in length, decreasing to the metatarsophalangeal region. The damper is made wedge-shaped and its thickened part is located between the cantilever element and the spring in the place of the spring wave to the heel part.

According to the second claim, the cantilever element is inclined to the vertical axis of the ankle at an angle β = 92-97 ^about . The range of the angle of inclination of the cantilever element is determined on the basis of calculations, modeling and experiments.

 According to the third claim, the ankle and cantilever element are in the form of a single L-shaped element.

≥ 0,01 где σ_в предел прочности материала;
Е модуль упругости материала в продольном направлении.According to the fourth claim, the cantilever element and the spring are made of a polymer composite material, the mechanical characteristics of which are related by the ratios:
σ _in ≥ 270 MPa

≥ 0.01 where σ _{is the} tensile strength of the material;
E is the modulus of elasticity of the material in the longitudinal direction.

 The indicated rational values of the physicomechanical characteristics of the material and their ratio are determined based on the calculation results and confirmed experimentally. The material for the cantilever element and the spring can serve, for example, carbon fiber, fiberglass organoplastic and their combinations in the product.

According to the fifth claim, the plane of the location of the troughs of the spring waves to the vertical axis at an angle of 84-87 ^about . The optimal range of values for this angle is determined by the results of modeling and experiments.

1,2-1,7 где h₁ толщина рессоры в пяточной и плюсне-фаланговой частях;
h₂ толщина рессоры в геленочной части стопы.According to the sixth claim, the ratio of the thicknesses of the springs (assuming that the modulus of elasticity of the material and the width of the springs are constant in length) will be presented in the form:

1,2-1,7 where h _{1 the} thickness of the spring in the heel and metatarsophalangeal parts;
h _{2 the} thickness of the spring in the gel part of the foot.

 It has been experimentally confirmed that this range of the ratio of the indicated thicknesses of the springs provides the optimal rigidity of the gel section of the foot.

≥ 0,01 где σ_в предел прочности материала;
Е модуль упругости материала в продольном направлении.The frame is equipped with a cantilever element designed to obtain a zone of resistance to destruction, the rigidity of which decreases to the metatarsophalangeal region of the foot, which contributes to its smooth inclusion in the work. The damper is made wedge-shaped and its thickened part is located between the cantilever element and the spring at the spring wave runaway to the heel part in order to normalize the stiffness of the heel of the artificial foot and tilt the plane of the spring wave troughs to the vertical axis at an angle α = 84-87 ^о , which would allow lifting the forefoot of the prosthesis by 1-1.5 cm when relieving the load on the foot at the time of transfer to avoid collision of the toe with the walking surface. The cantilever element is inclined to the vertical axis of the ankle at an angle β = 92-97 ^about to ensure its timely inclusion in the simulation of the zone of resistance to fracture. The ankle and cantilever element can be made integrally, which will lead to the accumulation of more internal energy. This can be used to create a special prosthetic foot for patients leading an active physical lifestyle, for example, an artificial foot for athletes. The cantilever element and the spring are made of a polymer composite material, for which the inequalities are true:
σ _in ≥ 270 MPa

≥ 0.01 where σ _{is the} tensile strength of the material;
E is the modulus of elasticity of the material in the longitudinal direction.

 This allows you to increase the elasticity of parts without reducing their strength characteristics, thereby 2-3 times increase their fatigue properties.

 The implementation of the design in this way allows you to simulate the spring function. The effect of flattening and flattening resistance of the foot is normal, to accumulate the deformation energy of the prosthesis elements necessary for the prosthesis to perform the back push in order to bring the patient's energy consumption level when walking to normal, to create highly effective prosthetic feet for sports, increase the step and speed of walking, and even out the patient’s gait .

 In FIG. 1 shows a General view of the frame of an artificial foot; in FIG. 2 is a general view of an artificial foot frame with an ankle and cantilever element made in the form of a single L-shaped element.

 The artificial foot frame contains an ankle 1, a cantilever element 2, a damper 3 and a spring 4. The spring 4 is made wavy with two wave troughs, one of which is located in the heel 5. The spring 4 is attached to the top of the wave of the gel part 7 of the foot to to the cantilever element 2. The second wave trough of the spring 4 is located in the metatarsophalangeal region 8. The spring 4 is made with variable stiffness along the heel, decreasing to the heel part 5 and metatarsophalangeal part 8. A variable stiffness is provided along the length through the implementation of its variable along the length of the cross section. The cantilever element 2 is made with variable stiffness along the length, decreasing towards the metatarsophalangeal part 8 of the spring 4, which is achieved by sequentially reducing the cross section of the cantilever element, at least starting from its point of contact with the gel part 7 of the spring 4 in its direction metatarsophalangeal part 8. The damper 3 is made wedge-shaped and its thickened part is located under the ankle 1 between the cantilever element 2 and the spring 4 at the bend of the spring wave to the heel part 5.

The cantilever element 2, it is advisable to tilt to the vertical axis O ₁ -O ₁ ankles at an angle, for example, 95 ^about .

 In some cases, the ankle 1 and the cantilever element 2, it is advisable to integrally in the form of an L-shaped element (see Fig. 2).

The cantilever element 2 and the spring 4 is expediently made of a polymer composite material, for example carbon fiber, for which the tensile strength σ _is 400 MPa and the elastic modulus in the longitudinal direction is E 40,000 MPa.

The plane O ₂ -O ₂ location of the troughs of the waves of the spring 4, it is advisable to tilt to the vertical axis O ₁ -O ₁ ankles 1 at an angle, for example, 87 ^about .

When performing spring 4 with a variable cross section, successively decreasing on both sides of the gel part 7 of the foot, it is advisable to take the ratio of the thickness of the spring in the heel 5 and metatarsophalangeal 8 parts (h ₁ ) to the thickness of the spring in the gel part of the foot (h ₂ ), for example, 1.5.

 To take into account the anthropometric features of each patient when designing the skeleton of an artificial foot N. N. Litvin a stop program has been developed. The specific values of the design values of the elements of the artificial foot frame for a patient weighing 70 kg, whose height is 175 cm with a shoe size of 42, are summarized in table. 1 and 2.

 For the convenience of using the product by the patient and in order to give it a complete cosmetic appearance, the artificial foot frame is placed in an elastic shell.

In the process of walking, the artificial foot goes through four main phases: the front push phase, the rolling phase, the back push and the foot transfer. During the collision of the prosthesis with the walking surface, the heel section 5 of the spring 4 is deformed and internal energy is accumulated. In this case, the shock load on the product is compensated by the elastic damper 3. At this, the forward push phase ends and the roll phase begins, during which the load is gradually distributed between the calcaneal 5, gelenic 7, and then the metatarsophalangeal 8 sections of the artificial foot. In this case, the spring 4 is spread out and the spring function of the foot is performed. There is a further accumulation of internal energy by the spring 4. When the foot arch in the gel part 7 reaches its maximum value W _{max, the} cantilever element 2 is activated, interacting with its front part with the metatarsophalangeal part 8 of the spring 4, which allows you to simulate the biologically justified effect of resistance to spreading by increase the rigidity of the deformable system. Further, the load is transferred to the metatarsophalangeal part 8 of the artificial foot, which causes further deformation of the spring 4 and the cantilever element 2 and contributes to the continued accumulation of internal energy by the structure. During the passage of the center of gravity of the patient’s body through the equilibrium position, the accumulated internal energy is released and an elastic back push is performed. When removing the load on the foot, the transfer phase begins, damper 3 goes into an undeformed state, thereby squeezing the metatarsophalangeal part of the prosthesis up by an amount that avoids the collision of the toe of the prosthetic foot with the walking surface.

 The main technical property of the inventive artificial foot frame is the effect of accumulation of internal energy of the deformation of the prosthesis elements by interacting when walking the spring, damper and cantilever element, in order to simulate the elastic back push, the effect of flattening and resistance to flattening of the spring function of the foot.

Compared with the base object, which is selected as the prototype, the inventive artificial foot frame has the following advantages:
the level of energy consumption of the patient when walking is normalized;
spring function is modulated, the effect of flattening and resistance to flattening of the foot is normal;
the patient’s step is normalized;
increased stability when walking;
the product is designed in strict accordance with the anthropometric data of the patient;
the use of the product makes it possible to lead a physically active lifestyle, play sports;
significantly improves the manufacturability and reliability of the artificial foot.

Claims (5)

 1. CASE OF ARTIFICIAL FOOT, containing an ankle, undulating spring with two troughs of the wave - in the heel and metatarsophalangeal region and the top of the wave in the gel part of the foot, a damper located between the ankle and spring, characterized in that a cantilever element located under the ankle and attached to it, and the spring is made with a variable in length stiffness decreasing to its ends, and attached by the top of the wave to a cantilever element, which is made with a variable in length stiffness decreasing to plus non-phalanx region, and the damper is made wedge-shaped and its thickened part is located between the cantilever element and the spring in the place of the spring wave in the heel. 2. The frame according to claim 1, characterized in that the cantilever element is inclined to the vertical axis of the ankle at an angle of 92 - 97 ^o .  3. The frame according to claims 1 and 2, characterized in that the ankle and cantilever element are made in the form of a single L-shaped element. 4. The frame according to claims 1 to 3, characterized in that the cantilever element and the spring are made of a polymer composite material, tensile strength σ _{in the} material and elastic modulus E of which satisfy the following relationships:
σ _in ≥ 270 MPa;

5. The frame according to claim 1, characterized in that the plane of the location of the troughs of the spring waves is inclined to the vertical axis of the ankle at an angle of 84 - 87 ^o . 6. The frame according to claims 1 to 5, characterized in that the thickness h _{1 of the} spring in the metatarsophalangeal and heel of the foot is related to the thickness h _{2 of the} spring in the ankle by the ratio
h ₂ / h ₁ = 1.2 - 1.7.

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