WO2006073374A1

WO2006073374A1 - Exomuscular orthosis

Info

Publication number: WO2006073374A1
Application number: PCT/SI2005/000039
Authority: WO
Inventors: Zlatko Matjacic
Original assignee: INSTITUT RS ZA REHABILITACIJO
Current assignee: INSTITUT RS ZA REHABILITACIJO
Priority date: 2005-01-07
Filing date: 2005-12-12
Publication date: 2006-07-13
Anticipated expiration: 2007-07-07

Abstract

Exomuscular orthosis according to the invention acts in a way that counteracts pathological functioning of particular muscle groups by enabling restoration of lower limb segments posture and by enabling selection of mechanical stiffness of the orthosis elements. Exomuscular orthosis comprising cuffs (1,2,3) and shoe fixation framework (4) mutual connected with elastic elements (5 -14), where each elastic element (5-14) consist rigid parts (17,19) with intermedia elastic band (18) or bands (22,23). Rigid part (17) is attached on a hook element (15) of upper cuff (1,2,3) and rigid part (19) is attached with fixation element (21) to a lower cuff (2, 3) or shoe fixation framework (4) through desirable hole (20, 24,25).

Description

EXOMUSCULAR ORTHOSIS

State of the art

Current designs of lower limb orthosis focus predominantly upon joint management. They are in general constituted of artificial mechanical segments articulated by mechanical joints, thereby representing exoskeleton construction, that functions in a way that locks movement of a given joint in selected posture. Possibly such an exoskeleton may also serve as carrying framework for elastic elements that alter dynamical characteristics of a given joint. This is completely satisfying solution in orthopedic conditions when the primary aim of orthosis is to stabilize joint where the mechanical loading on the particular joint should be avoided, i.e. when replacing mechanical action of sprained ligaments or ruptured muscles or tendons. Frequently the same type of orthoses is used also to alter posture or dynamic characteristics of particular joint also in neurological conditions where the objective of orthotic management is different from orthopedic conditions. In neurological conditions the primary aim is to facilitate re-learning of sensory-motor patterns. Since lower limb is a multi-segmental and multi-muscular biomechanical system the described exoskeleton-type orthotic systems, although stabilizing given joint, will inevitably induce kinematic and kinetic alterations in other joints, which induces re-learning of inappropriate motor patterns. For example AFO (ankle foot orthosis) is a very popular orthosis that is used either in drop-foot condition or when a correction of foot posture is needed due to spastic or contractured plantarflexor muscle group. The application of solid AFO will stabilize ankle joint, however it will preclude motion in the ankle joint, thereby changing significantly biomechanical requirements at the knee and hip joints. It would be more beneficial if the correction of AFO was more dynamic, i.e. such that the posture of the ankle joint is corrected, while simultaneously also movement around ankle joint is still possible; this may have beside orthotic effect, also therapeutic effect, which in time can render decrease of plantarflexor spasticity. While the application of AFO is clinically viable, the application of similar orthosis at the knee and hip considerably limits the overall mobility of the lower limb and is therefore used only when all other means of bracing are exhausted.

The above description of the current state of the art highlights the predominant feature of existing orthotic systems, which serve as exoskeletal framework. Very different approach would be a design of exomuscular framework. The key difference is that exoskeletal systems inevitably comprises of artificial joints, which are used to stabilize biological joints and by doing that significantly limit mobility of these joints. On a contrary exomuscular framework conceptually consists of mechanical cuffs that firmly adhere to pelvis and lower extremities segments that serve as mechanical base for elastic strings of various lengths and mechanical stiffness that are used for correction of joints postures and mechanical stiffness of multi-jointed system.

We propose an innovative orthotic system that seeks to overcome limitations of the existing systems by focusing onto alteration/restoration of biomechanical functioning of the major lower leg muscle groups that are either spastic and thereby contractured or weakened. We propose orthotic system that acts in a way that counteracts pathological functioning of particular muscle groups by enabling restoration of lower limb segments posture and by enabling selection of mechanical stiffness of the orthosis elements.

Description of invention

The invention is described following the content of 14 figures that schematically portrait the essential features, elements and technical principles of the proposed exomuscular orthosis. The invention will now be described by way of example and with reference to the accompanying drawings where :

Figure 1 shows a sagittal plane projection of a walking subject; Figure 2 shows a sagittal plane projection of a walking subject with addition of the elastic element (5);

Figure 3 shows a sagittal plane projection of a walking subject with addition of the elastic element (6); Figure 4 shows a sagittal plane projection of a walking subject with addition of the elastic element (7);

Figure 5 shows a sagittal plane projection of a walking subject with addition of the elastic element (8) and elastic element (9);

Figure 6 shows a sagittal plane projection of a walking subject with addition of the elastic element (10);

Figure 7 shows a sagittal plane projection of a walking subject with addition of the elastic element (11);

Figure 8 shows a sagittal plane projection of a walking subject with addition of the elastic element (12) and elastic element (13);

Figure 9 shows a sagittal plane projection of a walking subject with addition of the elastic element (14); Figure 10 shows a sagittal plane projection of a walking subject with addition of the elastic element (5); Figure 11 shows a sagittal plane projection of a walking subject with addition of the elastic element (8);

Figure 12A conceptual design of elastic elements (5-14); Figure 12B the fixation of elastic elements (5-14) to a designated cuff (1-3);

Figure 13A typical requirement when designing mechanical characteristics of elastic elements (5-14); Figure 13B shows force-length graph for two possible stiffness values; Figure 13C shows both possible solutions within single mechanical design of elastic element (8); Figure 14 shows possible addition to the elastic elements (5-

14).

According to the Fig. 1 cuff elements embracing the pelvis cuff 1 , thigh cuff 2, shank cuff 3 and shoe fixation framework 4 provide firm base for the remaining of the exomuscular orthosis disclosed in the following figures. Cuff elements 1-3 can be made of appropriate material normally used in orthotics such as polypropylene, while shoe fixation framework 4 can be made of aluminum or other appropriate material that can be shaped in a way to provide firm base. Shoe fixation framework 4 can be conveniently attached to the shoe through the shoe heel. Cuff element 1 can be equipped with straps that can be placed over person shoulder's to enable more even distribution and partially relief of loading forces on the pelvis.

Left side of Figure 2 is similar to Figure 1 with addition of the elastic element 5 which connects anteriorly to pelvis cuff 1 on one end and thigh cuff 2 on the other end. This elastic element 5 should be used to compensate the force of contracture of gluteus maximus muscle (hip extensor) or in case of iliacus muscle weakness (hip flexor). On the right side of Figure 2 schematic action of the stretched elastic element 5, which acts to increase hip flexion angle, is shown. Schematics drawn in figures 2 - 8 are all organized in the above described way.

Left side of Figure 3 shows the application of elastic element 6, which connects, anteriorly to pelvis cuff 1 on one end and shank cuff 3 on the other end. In this way elastic element 6 mimics the action of biarticular muscle rectus femoris and should be used to compensate the force of contracture of hamstring muscle group (hip extensor, knee flexor) or in case of rectus femoris weakness (hip flexor, knee extensor). The right side of Figure 3 shows action of the strecthed elastic element 6, which acts to increase hip flexion and knee extension angles.

Left side of Figure 4 shows the application of elastic element 7, which connects, anteriorly to thigh cuff 2 on one end and shank cuff 3 on the other end. In this way elastic element 7 mimics the action of vastus muscle group and should be used in case of vastus muscle group weakness (knee extensor). The right side of Figure 4 shows action of the stretched elastic element 7, which acts to increase knee extension angle.

Left side of Figure 5 shows the application of elastic element 8, which connects, anteriorly to shank cuff 3 on one end and shoe fixation framework 4 on the other end. In this way elastic element 8 mimics the action of tibialis anterior muscle and should be used to compensate the force of contracture of soleus muscle (ankle plantarflexor) or in case of tibialis anterior weakness (ankle dorsiflexor). Additionally, the application of elastic element 9 which connects anteriorly to thigh cuff 2 on one end and shoe fixation framework 4 on the other end, is shown. In this way elastic element 9 mimics the action of nonexistent human muscle and should be used to compensate contracture of biarticular gastrocnemius muscle (ankle plantarflexor, knee flexor). The middle graph of Figure 5 shows action of the strecthed elastic element 8, which acts to increase ankle dorsiflexion angle. The right side of Figure 5 shows action of the strecthed elastic element 9, which acts to increase knee extension and ankle dorsiflexion angles. Left side of Figure 6 shows the application of the elastic element 10 which connects posteriorly to pelvis cuff 1 on one end and thigh cuff 2 on the other end. This elastic element 10 should be used to compensate the force of contracture of iliacus muscle (hip flexor) or in case of gluteus maximus muscle weakness (hip extensor). On the right side of Figure 6 schematic action of the stretched elastic element 10, which acts to increase hip extension angle, is shown.

Left side of Figure 7 shows the application of elastic element 11 , which connects, posteriorly to pelvis cuff 1 on one end and shank cuff 3 on the other end. In this way elastic element 11 mimics the action of biarticular hamstring muscle and should be used to compensate the force of contracture of rectus femoris muscle group (hip flexor, knee extensor) or in case of hamstring muscle group weakness (hip extensor, knee flexor). The right side of Figure 11 shows action of the stretched elastic element 11 , which acts to increase hip extension and knee flexion angles.

Left side of Figure 8 shows the application of elastic element 12, which connects, posteriorly to shank cuff 3 on one end and shoe fixation framework 4 on the other end. In this way elastic element 12 mimics the action of soleus muscle and should be used in case of soleus muscle weakness (ankle plantarflexor). Additionally, the application of elastic element 13 which connects posteriorly to thigh cuff 2 on one end and shoe fixation framework 4 on the other end, is shown. In this way elastic element 13 mimics the action of gastrocnemius muscle and should be used in case of biarticular gastrocnemius muscle weakness (ankle plantarflexor, knee flexor). The middle graph of Figure 8 shows action of the stretched elastic element 12, which acts to increase ankle plantarflexion angle. The right side of Figure 5 shows action of the stretched elastic element 13, which acts to increase knee flexion and ankle dorsiflexion angles.

Figure 9 shows frontal plane view. Left side of Figure 9 shows the application of elastic element 14 which connects laterally to pelvis cuff 1 on one end and thigh cuff 2 on the other end. Elastic element 14 mimics the action of hip abductors and should be used in case of hip adductors contracture or in case of hip abductor weakness. The right side of Figure 9 shows action of stretched elastic element 14, which acts to increase hip abduction angle. Figure 10 shows possible attachment sites for elastic element 5, which can be used to provide additional action on the hip external rotation in case of hip internal rotators contracture. With shown positioning of elastic element 5 we simultaneously obtain corrective action of hip posture in the sagittal and transverse planes. The right side of Figure 10 shows action of stretched elastic element 5, which acts to increase hip external rotation angle.

Similarly to Figure 10, left side of Figure 11 shows possible attachment sites for elastic element 8, which can be used to provide additional action on the ankle external rotation in case ankle invertors contracture. With shown positioning of elastic element 8 we simultaneously obtain corrective action of ankle posture in the sagittal and frontal planes. The right side of Figure 11 shows action of stretched elastic element 8, which acts to increase ankle eversion angle. In principle all elastic elements 5-14 can be attached to designated cuffs 1-3 or shoe fixation framework 4 in such a way to act also in other planes of particular joint motion.

Figure 12A shows conceptual design of elastic elements 5 -14, which consists of three parts: rigid part 17, made of very stiff fabric or other suitable material, elastic band 18, made of stretchable fabric or other suitable material and rigid part 19 with holes 20, made of very stiff fabric or other suitable material. Figure 12B shows the fixation of elastic elements 5-14 to a designated cuff 1-3 or shoe fixation framework 4. Rigid part 19 with holes 20 is attached through one of the holes 20 to a designated cuff 1-3 or shoe fixation framework 4 by means of fixation element 21 while rigid part 17 is connected at the free end to a ski-boot type of clip 16, which consists of steel wire loop and solid handle. Clip 16 is used to attach and stretch elastic elements 5-14 on a hook element 15, which is imbedded into a designated cuff 1-3.

The list of possible elastic elements 5-14 and their application presented in Figures 2 - 11 is not exhaustive but is rather demonstration of possible designs that will bring about corrective action. Figure 13A shows typical requirement when designing mechanical characteristics of elastic elements 5-14. This is done on the example of elastic element 8 characteristics when counteracting soleus muscle contracture in the ankle joint. In order to overcome resulting static force of soleus muscle contracture and positioning the ankle joint to a desired posture elastic element 8 have to be of length / and should sustain force F₀. Figure 13B shows force-length graph for two possible stiffness values. It is clear that required force F₀ can be obtained within lower stiffness K if it is stretched for length d₂ and also with higher stiffness 2K if stretched for lenght (J₁. Figure 13C shows both possible solutions within single mechanical design of elastic element 8. Left graph shows elastic element 8 in resting state. Elastic band 18 as shown in Figure 12A is composed from two elastic bands 22, 23, while rigid part 19 has two holes 24, 25 separated in the distance (J₂-Cl₁. The middle graph shows stretched elastic element 8 in such a way that both elastic bands 22, 23 are engaged and stretched, while the rigid part with holes 19 should be attached through lower hole 25. The right graph shows situation when only one elastic band 22 is engaged and stretched, while the rigid part 19 with holes 24, 25 should be attached through higher hole 24. In both cases we obtain required length / and required force F₀ of elastic element 8. However, in the first case the stiffness of the elastic element 8 is 2K, while in the second case the stiffness is only K. This principle can be extended to more elastic bands 22, 23 and more holes 24, 25 that can be more closely positioned. In such way we can easily change dynamic properties of each elastic element 5-14. With the described concept we can design orthosis that allow us much better selection of biomechanical characteristics of the lower limb - orthosis interaction.

Figure 14 shows a possible addition to the elastic elements 5-14. In comparison to schematics shown in Figure 13C (left side) there is added another element 26, which is longer than both elastic bands 22, 23 and as such slack and does not contribute to force generation when the whole structure is at resting length. When elastic element 5-14 is stretched it exhibits stiffness 2K as long as stretch is shorter than d_κ as displayed on the graph at the right side of Figure 14. When stretch exceeds d_κ element 26, which is much stiffer, becomes stretched and the stiffness of the whole system is dramatically increased to K_κ, which significantly impedes further stretching. By using elastic elements 5-14 as displayed and described in Figures 13 and 14 exomuscular orthosis become very versatile device with great capabilities to adopt to particular needs of particular person. Elastic elements 5-14 can be of two different lengths, one for uniarticular muscles and the other for Particular muscles. Since elastic elementsm 5 -14 are composed also from rigid part 19 with holes 20,24,25, which can be longer and have more holes than presented in Figure 13C, elastic elements 5-14 of same size can accommodate different heights and segment lengths. We can imagine that for example three different sizes would be sufficient to cover geometric requirements ranging from small children to adults. Due to the proposed conceptual design of elastic elements they can easily be adjusted to desired length /, providing required force F₀ and exhibiting dynamic stiffness depending on the needs of particular patient. The same physical system can be re-adjusted as the biomechanical requirements (due to reduced spasticity of particular muscles for example) change through course of training. Also it is not needed that each of presented elastic elements 5-14, cuffs 1-3 or shoe fixation framework 4 is used. Only selected parts of the exomuscular orthosis system can be used and the decision, which these parts are, will depend entirely on particular needs of a particular case.

Claims

CLAIMS:

1. Exomuscular orthosis, comprising cuffs (1 ,2,3) and shoe fixation framework (4) mutual connected with elastic elements (5 -14).

2. Exomuscular orthosis, according to Claim 1 , characterized in that, each elastic element (5-14) consist of rigid parts (17,19) with intermedia elastic band (18) or bands (22,23) where rigid part (17) is attached on a o hook element (15) of upper cuff (1 ,2,3) and rigid part (19) is attached with fixation element (21) to a lower cuff (2, 3) or shoe fixation framework (4) through desirable hole (20, 24,25).

3. Exomuscular orthosis, according to Claim 2, s characterized in that, rigid part (17) is connected at the free end to a ski-boot type of clip (16) which consists of steel wire loop and solid handle.

4. Exomuscular orthosis, according to Claims from 1 to 3, o characterized in that, another element (26) is added between rigid part (17) and rigid part (19) which is longer than elastic bands (22,23).

5. Exomuscular orthosis, according to claims from 1 to 4, characterized in that, cuff element (1) is equipped with straps.