Ankle-foot orthosis

Abstract

To provide an ankle-foot orthosis with bilateral metal uprights, commonly used for patients with spastic lower limb paralysis exhibiting strong equinovarus, where the orthosis has: a function of adjustment of the ankle joint range of motion; an adjustable plantar flexion resistance function; a propulsion function by enabling rapid recovery from a plantarflexed position to a dorsiflexed position thereby pushing the lower leg forward; and an adjustable dorsiflexion resistance function aimed at preventing knee collapse in flaccid paralysis and avoiding localized loading due to forward shifting of the plantar load center.SOLUTION: An ankle-foot orthosis with bilateral metal uprights is provided, in which a flexible section having elasticity in the plantar flexion-dorsiflexion direction is provided in a portion 23, 23', 23" just above an ankle joint in a shape that does not compromise the rigidity of the orthosis, allowing adjustment of the elastic strength by selection and replacement of components and by a function of adjusting the free range of motion of the ankle joint.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] When paralysis occurs in the lower limbs due to stroke, cerebral palsy, spinal cord injury, etc., and it is difficult to walk barefoot, long leg braces up to the upper knee or short leg braces up to the lower knee are used during the recovery period, and short leg braces are often used during the life period.

[0002] The types of paralysis include spastic paralysis and flaccid paralysis. In the case of spastic paralysis, equinovarus deformity of the foot is likely to occur. When standing, the outer front part of the foot touches the ground, and there is knee hyperextension, making standing and walking unstable.

[0003] For short leg braces for spastic paralysis patients, braces with the following functions are used: 1. Correction of equinovarus deformity, 2. Correction of varus deformity, 3. Plantar flexion limitation or plantar flexion braking function of the ankle joint during the stance phase, 4. Propulsion function by rapid recovery of the ankle joint from plantar flexion to dorsiflexion, 5. Dorsiflexion holding function of the ankle joint during the swing phase.

[0004] In the case of flaccid paralysis, due to reduced muscle output, support and motility such as knee flexion and drop foot are reduced. Therefore, braces with the following functions are used: 6. Assistance for ankle dorsiflexion, 7. Prevention of knee flexion by limiting ankle dorsiflexion, 8. Function of expanding the range of motion of the ankle joint and shifting the center of foot load by braking ankle dorsiflexion.

[0005] In the case of severe equinovarus deformity, it is difficult to walk without strong corrective force, so short leg braces with bilateral metal struts are used.

[0006] Short leg braces with bilateral metal struts are composed of a lower leg cuff 10, struts 20, foot joints 30, 31 (Figure 1 shows a single Crenshaw foot joint, Figure 2 shows a double Crenshaw foot joint), shin guards 40, feet 60, and cuff belts 70 as shown in Figures 1 and 2. They are highly rigid and are used for spastic paralysis patients with severe equinovarus deformity.

[0007] For the foot joints, box-type, single Crenshaw, double Crenshaw foot joints, etc. are used, and the range of motion of plantar flexion and dorsiflexion of the ankle joint is set by adjusting screws 50, 51, 52 or by adjusting the gap between the shin guard 40 and the foot joint.

[0008] In the case of spastic paralysis where there is no risk of knee flexion, it is easier to perform the sitting and standing movements from a chair and to increase the step width if the ankle dorsiflexion limit angle is made free.

[0009] The ankle plantar flexion limit angle is set from a slightly dorsiflexed position to 0° so that the forefoot does not touch the floor during the swing phase of the leg.

[0010] In the case of flaccid paralysis where there is a high risk of knee flexion, the ankle dorsiflexion limit angle is set at a slightly dorsiflexed position to prevent knee flexion.

[0011] The ankle plantar flexion limit angle is set from a slightly dorsiflexed position to 0°, similar to spastic paralysis.

[0012] In addition to the function of restricting the free range of motion of plantar flexion and dorsiflexion by the box-type, single-crutch, and double-crutch ankle joints of the short lower limb orthosis with bilateral metal struts, the present invention has a function of moderately flexing beyond the limit angle by the flexure portions 23, 23', 23" provided at the proximal portion of the ankle joint.

[0013] In the case of spastic paralysis, this function enables the plantar flexion braking movement of the ankle joint by the strut flexing from the plantar flexion limit angle to plantar flexion during the heel strike phase of the walking cycle, acting as an ankle rocker function.

[0014] In the case of flaccid paralysis, this function causes the strut to flex from the dorsiflexion limit angle to dorsiflexion, moving the center of foot load forward, increasing the step width, and avoiding load concentration on a part of the sole of the foot.

[0015] The present invention can be adjusted to an appropriate elasticity by selecting and replacing the shapes and materials of the flexure portions 23, 23', 23" according to the degree of spasticity, the weight of the flaccid paralysis patient, the walking posture, etc.

Prior Art Documents

Patent Documents

[0016] Patent Document 1 has a compact and powerful plantar flexion braking function using hydraulic pressure at the ankle joint part.

[0017] Although it is miniaturized by using hydraulic pressure, the hydraulic pressure acts as a plantar flexion braking function for the ankle joint but does not have a function to return from the plantar flexion position. Since a dorsiflexion assist spring is used, in the case of severe spastic equinovarus, it cannot return sufficiently from the plantar flexion position to the dorsiflexion position, so it is difficult to use.

[0018] Patent Document 2 enables plantar flexion braking, propulsion function, and dorsiflexion braking by making one rear strut elastic, but the lateral stability is not sufficient and it is not suitable for severe varus.

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0019] While maintaining the adjustment function of the ankle joint plantar dorsiflexion limit angle of the short lower limb orthosis with bilateral metal struts used by spastic paralysis patients with severe varus, it has an ankle joint plantar flexion braking function and a propulsion function due to a quick recovery from the ankle joint plantar flexion position to the dorsiflexion position.

[0020] To provide a dorsiflexion braking function for the purpose of preventing knee flexion in flaccid paralysis and avoiding partial load concentration by moving the center of foot load forward.

[0021] The braking force of the ankle joint plantar flexion braking function and the dorsiflexion braking function can be adjusted to an optimal state according to the degree of spasticity, the weight of flaccid paralysis patients, and their gait.

Means for Solving the Problems

[0022] Since the struts of the short lower limb orthosis with bilateral metal struts are wide in the front-rear direction and difficult to bend in the front-rear direction, by making them partially easy to bend in the front-rear direction, a plantar flexion braking function and a dorsiflexion braking function are provided for the struts.

Effects of the Invention

[0023] It has been difficult to select an appliance with plantar flexion braking that can be used by spastic paralysis patients with severe internal inversion and equinovarus, but by providing a highly elastic leaf spring function to the struts of a short lower limb appliance with rigid bilateral metal struts, the ankle joint flexes moderately during heel contact, and a plantar flexion braking function can be obtained.

[0024] Due to the elastic force of a strong leaf spring, after the ankle joint has plantar flexed, a rapid restoring force causes a force that pushes the lower leg forward to act on the lower leg cuff part, and a propulsive force for walking can be obtained.

[0025] In the case of flaccid complete paralysis of both lower limbs such as split spine, since the motor functions of both plantar flexion and dorsiflexion of the ankle joint are lost, an appliance that restricts the mobility of the ankle joint is used. However, since the center of load concentrates on the heel and the sensation is also lost, pressure sores are likely to occur, and it is also difficult to utilize the ankle rocker function during walking.

[0026] In order to move the center of load forward to the front of the foot, it is necessary to strongly brake the dorsiflexion of the ankle joint, which has been difficult with conventional appliances. With the present invention that utilizes the elastic force of a strong leaf spring, strong dorsiflexion braking becomes possible, an ankle rocker function can be obtained, partial load concentration is avoided by moving the center of foot load forward, and a pressure sore prevention effect can be obtained.

[0027] The short lower limb appliance, which is a prosthetic appliance manufactured according to individual physical conditions and usage conditions, determines the shape of the sole of the foot, the necessity of heel lift, and the degree of lift, and selects and manufactures the type of appliance and each component.

[0028] Even after the short lower limb appliance is completed, there are changes in physical conditions and usage conditions, and various modifications and adjustments are necessary.

[0029] In addition to selecting struts with a flexural part and adjusting the elastic force by replacement, the short lower limb appliance of the present invention can adjust the bending moment force at the plantar flexion and dorsiflexion angles to be adjusted by adjusting the plantar flexion limiting angle and dorsiflexion limiting angle of the ankle joint, which is effective for adjustment after completion.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0031] By replacing the struts of a conventional short-leg brace with bilateral metal struts with the struts in FIG. 5, FIG. 6, or FIG. 7, a short-leg brace can obtain a plantar flexion braking function, a propulsion function due to a quick recovery from the plantar flexion position to the dorsiflexion position of the ankle joint, and a dorsiflexion braking function.

Example

[0032] FIG. 11 shows a measurement diagram of the ankle joint plantar flexion moment during walking of a spastic hemiplegic.

[0033] The maximum bottom buckling moment is approximately 48 Nm.

[0034] Fig. 9 shows a side view of a short lower limb orthosis using the support column 20' of the present invention for a single cleancrack foot joint.

[0035] The dorsiflexion direction of the ankle joint is almost freely movable, making it easy to sit down and stand up from a chair.

[0036] Arrow A in Fig. 9 represents the ankle joint plantar flexion moment that occurs during walking of a spastic hemiplegic, and arrow B shows the dorsiflexion moment generated by the flexure portion 23 of the support column 20'.

[0037] The flexure portion 23 deforms until the plantar flexion moment A caused by spastic paralysis and the dorsiflexion moment caused by the elastic force of the flexure portion 23 of the support column balance each other.

[0038] By selecting the bending moment characteristics of the flexure portion 23 according to the maximum ankle joint plantar flexion moment and the allowable plantar flexion angle during walking caused by spastic paralysis, an appropriate plantar flexion braking function can be obtained.

[0039] The maximum plantar flexion moment in Fig. 11 is 48 Nm. When allowing 5° of plantar flexion due to plantar flexion braking, one side of the support column requires a bending moment characteristic of 24 Nm when flexed at 5° of plantar flexion.

[0040] When calculating the shape of the flexure portion that can obtain a bending moment of approximately 24 Nm at 5° of plantar flexion from the bending moment and the radius of curvature, when using steel, it is L = 50 mm, W = 10 mm, T = 4.3 mm in Fig. 8.

[0041] As can be seen in Fig. 11, since the plantar flexion moment of a spastic hemiplegic decreases after reaching the maximum value, the propulsive force of arrow C can be obtained by the elastic restoring force of the flexure portion 23.

[0042] The material used for the flexure portion is a material with a high Young's modulus such as steel, titanium alloy, and carbon fiber.

[0043] According to the present invention, it is possible to manufacture a short lower limb orthosis having a plantar flexion braking function even for a person with severe spastic paralysis.

Example

[0044] In a person with flaccid paralysis of the lower limbs, drop foot occurs due to a decrease or loss of the dorsiflexion muscle strength of the ankle joint, and the plantar flexion muscle strength of the ankle joint decreases or is lost, resulting in genu recurvatum because the dorsiflexion of the ankle joint cannot be restricted.

[0045] For the purpose of suppressing these, short lower limb orthoses or shoe-type orthoses that bring the ankle joint into a state close to fixation are used.

[0046] When the movement of the ankle joint is restricted, the center of load concentrates near the heel of the sole, and since the sensation is also lost, pressure sores are likely to occur.

[0047] In order to avoid the concentration of load near the heel, an orthosis that allows the ankle joint to move dorsally without causing genu recurvatum is required.

[0048] For this purpose, a function to supplement the weakened plantar flexor of the ankle joint is required. The main agonist muscle of the plantar flexor of the ankle joint is the triceps surae muscle, which is also the muscle that generates a strong plantar flexion force in a person with spastic hemiplegia.

[0049] Therefore, for an orthosis that allows the ankle joint of a person with flaccid paralysis of the lower limbs to move dorsally without causing genu recurvatum, a dorsiflexion braking force equivalent to the plantar flexion braking force in a person with severe spastic paralysis is required.

[0050] Fig. 10 shows an example of using the double cleancut ankle joint short lower limb orthosis of the present invention for a person with flaccid paralysis of the lower limbs.

[0051] Restrict from plantar flexion of 0° to a mild dorsiflexion position with the plantar flexion adjustment screw 52 of the double cleancut ankle joint to suppress drop foot.

[0052] Adjust to a mild dorsiflexion position with the dorsiflexion adjustment screw 51 to easily adjust the dorsiflexion of the ankle joint from the initial to the middle stage of stance.

[0053] At the initial stage of stance in Fig. 10, the center of gravity is located at arrow F, but from the middle to the late stage of stance, as the ankle joint becomes dorsiflexed, the center of gravity moves to arrow G.

[0054] The ankle joint dorsiflexion can move freely up to the limit angle of the dorsiflexion adjustment screw 51, but after that, it is dorsally braked by the flexure part 23’, and the ankle joint dorsiflexion moment (arrow D) generated to support the body weight by the forward tilt of the lower leg and the plantar flexion moment (arrow E) generated by the elasticity of the flexure part 23’ are braked at an angle where they balance, and no knee flexion occurs.

[0055] From the late stance phase to the double-leg support phase, the ankle joint dorsiflexion moment force due to body weight decreases, and due to the elasticity of the flexure part 23’, the kicking force of arrow H can be obtained.

Explanation of Signs

[0056] 10 Lower leg cuff 20 Strut for conventional single-crank clevis ankle joint 20’ Strut for single-crank clevis ankle joint of the present invention 21 Strut for conventional double-crank clevis ankle joint 21’ Strut for double-crank clevis ankle joint of the present invention 22 Body of the strut for single-crank clevis ankle joint of the present invention 22’ Body of the strut for double-crank clevis ankle joint of the present invention 22” Body of the dividable strut in Fig. 7 23 Flexure part of the strut for single-crank clevis ankle joint of the present invention 23’ Flexure part of the strut for double-crank clevis ankle joint of the present invention 23” Flexure part of the dividable strut in Fig. 7 24 Ankle joint part of the strut for single-crank clevis ankle joint of the present invention 25 Ankle joint fixing part of the conventional double-crank clevis ankle joint strut 25’ Ankle joint fixing part of the double-crank clevis ankle joint strut of the present invention 25” Ankle joint fixing part of the dividable strut in Fig. 7 30 Single-crank clevis ankle joint 31 Double-crank clevis ankle joint 40 tibia 50 single clevis leg joint plantar flexion adjustment screw 51 double clevis leg joint dorsiflexion adjustment screw 52 double clevis leg joint plantar flexion adjustment screw 60 foot part 70 lower leg cuff belt

Claims

1. By providing a bending portion at the proximal part of the ankle joint of the bilateral struts of the short lower limb orthosis with bilateral metal struts, the ankle joint undertakes the function of adjusting the free movement range, and the bending portion undertakes the functions of plantar flexion braking, dorsiflexion braking, and propulsion function, so that the short lower limb orthosis has both functions without impairing the rigidity of the short lower limb orthosis with bilateral metal struts.

2. The short lower limb orthosis is composed of strut body parts 20', 21' provided on both sides, a lower leg cuff 10 connecting the strut body parts 20', 21' at the upper ends of the strut body parts 20', 21', a lower leg cuff belt 70, ankle joints 30', 31 provided at the lower ends of the strut body parts 20', 21', a shin 40 connected to the upper ends of the ankle joints 30', 31, and a foot part 60 integrated with the lower ends of the shin 40. The short lower limb orthosis according to claim 1, characterized in that bending portions 23, 23', 23" are provided on a part of the strut body parts 20', 21'.

3. The bending portions 23, 23', 23" are characterized in that they smoothly change the shape on a part of the strut body parts 20', 21' and are provided with a shape portion that bends in the front-rear direction. The short lower limb orthosis according to claims 1 to 2.

4. The short lower limb orthosis according to any one of claims 1 to 3, characterized in that the bending portions 23, 23', 23" are arranged close to the ankle joints 30', 31.

5. When the strut body parts 20', 21' are made of steel, the bending portions 23, 23' are only quenched, and the other parts are not quenched so as to be easily processed during the manufacture of the orthosis. The short lower limb orthosis according to any one of claims 1 to 5.

6. The bending portions 23, 23' of the strut body parts 20', 21' are divided, and one or a plurality of leaf springs of 23" are used to make it easily replaceable, so that the elastic force can be easily adjusted. The short lower limb orthosis according to any one of claims 1 to 5.

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