DE112012000673T5 - Lower leg prosthesis - Google Patents

Abstract

An ankle unit in a lower leg prosthesis comprises a combination of a hydraulic piston-cylinder arrangement, which ensures a continuously damped area of ankle flexion, and an elastic telescopic shock absorber. The damping resistance of the piston-cylinder arrangement is the predominant resistance to ankle flexion and is provided by a piston (28) which can move axially in a cylinder (26) centered on the shin axis. The wall (26W) of the cylinder has a cylindrical outer bearing surface for a sleeve (48) which can translate according to the axial load relative to the piston-cylinder arrangement, the sleeve being elastically mounted by a compression spring (52) which extends axially in the sleeve and has an integral end portion (52B) forming an upper bulkhead of the cylinder. The sleeve can also rotate on the cylinder wall, the spring (52) providing torsional resistance.

Description

The invention relates to a lower leg prosthesis comprising a tibial component, a foot element and an ankle joint element interconnecting the tibial and foot elements. The ankle joint mechanism is arranged to allow limited, damped pivotal movement of the tibial member relative to the foot member. The invention also includes a prosthetic ankle unit.

Current prosthetic foot and ankle systems are normally coordinated to act as fixed mechanical structures that include resilient and deformable elements designed to provide stability when walking and standing, and for propulsion into the swing phase of the gait cycle Return energy. For the user, however, such a device is often uncomfortable when standing, walking on slopes and stairs, and walking at different speeds. Users have also learned that the knee is unstable and that it is difficult to maintain the forward motion while standing and walking on slopes and stairs when rolling the foot, resulting in impaired function. These difficulties are particularly important for thigh amputees in whom stance phase activity is normally compromised by significantly reduced knee flexion and knee extension, which would otherwise assist shock absorption and propulsion in the stance phase.

An ankle joint mechanism that enables dynamic hydraulic control of the angular position of a prosthetic foot with respect to a tibial component is described in Mauch Laboratories, Inc., Hydraulic Ankle Unit Manual, March 1988. The tibial member is attached to a wing piston which is disposed in a fluid-filled chamber having a concave, part-circular wall. A gravity-controlled ball rolls back and forth along the wall according to the orientation of the foot to open or close a bypass passage in the piston. This prevents dorsiflexion of the mechanism when the tibial component is vertical, largely independent of whether the foot is horizontal or inclined down or up. Such a prosthesis also suffers partly from the disadvantages described above.

Another known prosthetic ankle system is, inter alia, that according to US3871032 (Karas). This system includes a damping device with a dual piston-and-cylinder arrangement wherein valve lifter return springs operate continuously to return the ankle to a neutral position. The document EP-A-0948947 (O'Byrne) describes a prosthetic ankle with a ball joint that has a chamber filled with a silicone-based hydraulic substance, the joint having viscoelastic response. In one embodiment, the chamber contains solid silicone rubber particles suspended in a silicone fluid matrix. The document US2004 / 0236435 (Chen) describes an hydraulic ankle assembly having adjustable hydraulic damping and resilient biasing members mounted anteriorly and posteriorly of an ankle joint rotational axis. In the document WO00 / 76429 (Gramtec) describes a leg prosthesis with an ankle joint, which allows a heel height adjustment by means of a hydraulic piston and a mechanical connection arrangement. Elastic components absorb impacts when walking. The document US2006 / 0235544 (Iversen et al) describes a hydraulic ankle mechanism with a rotary valve.

An ankle joint mechanism that provides a continuously hydraulically damped ankle flexion area and in which cushioning resistance is the predominant resistance to flexion is disclosed in the document WO2008 / 071975 (Moser et al.).

It is also known to incorporate into the tibial component of a lower leg prosthesis a shock absorbing unit such as that in the documents GB2234907 (Harn) and GB2305363 (Aulie et al).

According to a first aspect of the invention, a lower leg prosthesis includes a tibial member defining a tibial axis, a foot member, and an ankle joint mechanism connecting the tibial member to the foot member, the ankle joint mechanism providing a continuously hydraulically damped ankle flexion region and configured and arranged such that at least over a portion of the range the damping resistance is the predominant resistance to flexion, and wherein the tibial component has an upper portion and a lower portion which are resiliently interconnected so that they can translate relative to one another in accordance with the axial compressive loading of the tibial component; wherein the direction of relative movement is substantially vertical when the foot member rests unloaded on a horizontal support surface. The mechanism preferably comprises a hydraulic linear piston-cylinder arrangement. The piston may have distal connection means for a pivotal connection with a foot member, wherein the Cylinder has proximal connection means for connection to a tibial component. Normally, the piston-and-cylinder arrangement has a central axis which is oriented so that, when the mechanism is connected to a prosthetic tibial component, it is substantially aligned with or parallel to the tibial axis defined by the tibial component.

In the preferred embodiment of the invention, the tibial element is provided in the form of a telescopic unit in which the upper part of the tibial member and the lower part of the tibial element each comprise an outer sleeve and a cylindrical housing slidably received in the sleeve. The ankle joint mechanism includes a hydraulic piston and cylinder assembly contained in the cylindrical housing so as to lie within the cylindrical enclosure defined by the cylindrical housing. As a result, the sleeve can cover at least part of the piston-cylinder arrangement when the telescopic unit is completely compressed. The result is a particularly compact unit, especially with regard to the overall extension of the combination of the telescopic unit and the ankle joint mechanism in the superior inferior direction. In an ankle joint mechanism with a linear piston-cylinder arrangement, it is preferred that the cylinder of the assembly include an upper divider wall and a lower divider wall, with a cylinder wall joining the upper and lower divider walls. The cylinder is subdivided into a variable volume lower and upper chamber portion, the chamber portions being separated by a piston and interconnected by at least one bypass passage containing a valve, for compactness the or each valve being in the lower divider wall. Each bypass passage is enclosed in the cylindrical enclosure and normally each has a bore in the cylinder wall parallel to the central axis of the piston-and-cylinder arrangement.

A particularly simple and compact arrangement according to the invention has as an elastic connection in the telescopic unit an axial compression spring, wherein an end portion thereof comprises the upper partition wall of the cylinder of the piston-cylinder arrangement. Accordingly, the coil spring and the upper cylinder partition wall may be constituted by a monolithic member received in the cylindrical housing of the lower tibial member. Conveniently, the spring is not only effective to withstand a translational relative movement of the parts of the tibial element, but it also acts as a torsion spring, which withstands a rotational relative movement. In this case, the coil spring has first and second ends secured against rotation in the upper and lower parts of the tibial member, respectively.

In the preferred telescopic unit, the parts of the tibial member may slide relative to each other in the direction of the centerline of the telescopic unit, which centerline is also substantially aligned with or parallel to the tibial axis. Typically, the ankle joint mechanism defines a medial-lateral ankle joint flexion axis which is positioned such that the midline of the telescopic unit extends within 30 mm of the ankle joint flexion axis, preferably posterior to the latter. With regard to the relationship between the telescopic unit and the foot member, the unit is preferably such that the center line passes through the foot member at an interval of between 0.2 L and 0.4 L anterior to the posterior end point of the foot member, where L is the total length of the foot element between its anterior and posterior end points.

The ankle joint mechanism defines an ankle joint flexion area extending from a dorsiflexion border to a plantar flexion border. These flexion limits are usually each between 2 ° and 5 ° and between 5 ° and 8 ° with respect to a state of stance phase of the ankle joint mechanism. Between these dorsal and plantar flexion boundaries, the ankle joint mechanism is substantially inelastic in the sense that it is not elastically biased. As a result, reaction forces around the ankle are largely dissipated throughout substantial portions of the gait cycle, with the result that desired control and proprioception are improved by the amputee. Applicants have found that such an ankle joint ankle mechanism generally allows the prosthesis to be loaded more axially, the angular yield of the mechanism allowing alignment of the foot at various tibial orientations, with the result that the additional loads on the prosthesis are the knee moments do not amplify to the extent that is the case with an ankle joint mechanism which is rigid over wide sections of the gait cycle. As a result, the elastic, shock-absorbing tibial component provides improved energy storage in the tibia, resulting in a more natural gait and comfort for the amputee. In addition, the amputee is encouraged by such factors to put more strain on the prosthetic limb, thereby relieving the burden on the other, natural leg.

To allow for individual adjustment of dorsal and plantar flexion damping resistance, the ankle joint mechanism may be provided with a valve assembly which controls hydraulic fluid flow between the chambers of the piston and cylinder on opposite sides of the piston, the valve assembly preferably comprising first and second adjustable valves for includes the respective damping control of dorsiflexion and plantarflexion. The ankle joint mechanism accordingly provides for a continuously hydraulically damped variable resistance ankle flexion region, the mechanism being configured and arranged such that movement over at least a portion of the region is dorsal and plantar over at least a portion of the region substantially without elastic bias.

The ankle joint mechanism preferably includes a mechanical end stop that limits dorsiflexion of the ankle joint mechanism, resulting in the tibial component having an anterior inclination of at least 3 ° with respect to the vertical upon flexion of the joint mechanism to the dorsiflexion limit. The mechanical end stop is effective when a part of the prosthesis connected to the tibial element abuts the other part of the prosthesis connected to the foot element. Conveniently, the end stop is defined by the piston of the piston-cylinder assembly abutting an end wall of the cylinder.

In the preferred embodiment of the invention, described below, the range of attenuated ankle flexion is fixed. Nevertheless, the aforementioned dorsiflexion limit may be adjustable over at least a range of anterior-posterior tilt angles of 3 ° to 5 °. In another embodiment, the range of attenuated flexion may change when the dorsiflexion limit is adjusted, but once the adjustment is made, the range of attenuated flexion is also determined step by step.

The prosthesis may be arranged to define the relative position of the connection of the foot member and the tibia to the dorsiflexion boundary independent of the spatial orientation of the assembly.

Adjustment of the tibial axis orientation with respect to the foot member in the anterior-posterior direction may be accomplished through the use of at least one common alignment bonding pyramid, preferably at the upper portion of the tibial component.

The combination of the aforementioned ankle joint mechanism and the elastically compressible tibial component works particularly well with an energy storing foot member having, for example, a fiber reinforced plastic leaf spring which is elastically deformable to permit dorsiflexion of at least an anterior portion of the foot member relative to an ankle attachment region of the foot. The foot spring is arranged to deflect when a dorsiflexion force is applied to the anterior portion of the foot and the ankle joint mechanism has reached its dorsiflexion limit. The ankle joint mechanism and the foot member together form a Maxwell model of a damper / spring combination whose damper element is the ankle joint mechanism and whose spring element is a spring member arranged in series with the ankle joint.

As mentioned above, the tibial component preferably comprises a telescopic unit which not only provides for elastic compression of the tibial member under load, but which also rotates the lower portion of the tibial member relative to the upper portion about a substantially vertical axis, e.g. , H. the midline of the unit and the tibial axis, allowed. A single coil spring provides both axial and torsional elasticity. However, it is also possible that the spring provides only axial elasticity, with one end of the spring in the lower part and the other end sitting in the upper part and one end of the spring or both relative to the part in which they are received, can rotate freely. The torsional elasticity can be provided separately by using an elastic rod made, for example, of a resilient thermoplastic material such as nylon-based plastic (e.g., Delrin) and positioned at the centerline of the telescopic unit, with each end of the rod is secured against rotation in the respective part of the tibial element, but can move freely in at least one of these parts longitudinally and axially.

A tibial prosthesis is described below which includes an elastically compressible tibial member defining a tibial axis, a foot member, and an ankle joint mechanism interconnecting the tibial member and the foot member and arranged to provide limited damped pivotal movement of the tibial member relative to the tibial component Foot member about a medial-lateral flexion axis of the joint, wherein the ankle joint mechanism comprises: a piston-cylinder assembly, the piston of which can move so as to define a volume variable fluid-filled chamber of the arrangement, wherein the fluid through at least one damping opening may flow into the chamber or be expelled from the chamber, while the relative orientation of the tibial member and the foot member varies with a flexion of the hinge mechanism; and flexion limiting means for limiting dorsiflexion of the hinge mechanism to a dorsiflexion limit corresponding to an orientation of the tibial member having a tibial axis anteriorly inclined at least 3 degrees to the vertical. The ankle joint mechanism is preferably arranged to allow for muted relative pivoting of the tibial component and the foot member over an angular range between the dorsal and plantar flexion limits, with various adjustments of the anterior inclination of the tibial axis with respect to the ankle being possible with respect to the dorsiflexion limit. In particular, the angular range includes a flat-footed and tibial-axis vertical condition, wherein the degree of tibial axis allowable anterior of the vertical is adjustable to various values.

In the preferred embodiment of the invention, the hinge mechanism has a first part connected to the tibial element and a second part connected to the foot element, these two parts being pivotally connected together and such interconnection defining a flexion axis of the joint , One of the two parts comprises the chamber of the piston-and-cylinder arrangement, and the other part is pivotally connected to the piston, the mechanism being arranged such that the dorsiflexion limit is defined by a mechanical stop which controls the rotation of the first and second Partially limited. This mechanical stop may be the abutment of the piston with an end face of the chamber. A bounce spring or bouncing pad may be provided on the surface of the piston or on the opposite chamber surface to increase resistance to dorsiflexion as the dorsiflexion margin approaches.

The limit of dorsiflexion is usually fixed, i. H. she is not adjustable. Alternatively, the limit may be preset. For example, the border may be defined by a connection with adjustable orientation of the anterior-posterior slope. The compound may be formed as described above in the form of a sufficiently known inverted pyramid. Another possibility is a lockable pivot joint for the connection of the foot member to the hinge mechanism, wherein an adjustment axis extends in the medial-lateral direction. As a further alternative, an adjustable end stop may be provided in the piston-cylinder assembly, or the connection between the piston and one of the elements of the mechanism for mounting the foot member or tibial member may be adjustable to the range of displacement of the piston in the chamber the arrangement with respect to the angular range of movement of the foot member relative to the tibial component to change.

The preferred hinge mechanism includes two channels communicating with the aforesaid chamber of the piston-and-cylinder assembly, each including a respective one-way valve, one of which is oriented to allow fluid to pass through its respective channel from the chamber and the other being oriented so as to prevent the flow of fluid through the other channel into the chamber so that one channel allows fluid flow when the hinge mechanism is flexed in the dorsiflexion direction while the other channel allows fluid flow, when the joint is flexed in the direction of plantarflexion. Preferably, both channels have respective damping openings with adjustable cross-section to allow a user-friendly adjustment of the degree of damping.

For detecting the hinge mechanism against pivotal movement in a number of positions of the foot member relative to the tibial member, a locking device may also be provided. Usually, this is done by using a manually or electromechanically actuated valve which interrupts fluid flow through the bypass passage into or out of the aforementioned chamber of the piston-and-cylinder arrangement. The locking device comprises a control with two positions in which one of the hinge mechanism operates in a yielding mode and in the other of which the hinge mechanism operates in a locking mode. Holding means are provided to hold the operating element in one of the two positions, e.g. B. a spring that biases the control in one position, and a detent, a latch or a fuse to hold the control in the other position.

According to a second aspect of the invention, there is provided a prosthetic ankle unit comprising the combination of a hydraulic linear piston-cylinder arrangement providing a continuously damped area of ankle flexion and defining a central axis, the assembly having a cylinder wall connected to the axis centered and includes a fluid-filled chamber whose volume varies with the movement of a piston in the chamber, and a telescopic shock absorber disposed coaxially with the piston-cylinder assembly and having an outer sleeve slidably received on the outside of the cylindrical wall is and with this is elastically connected so that it is translationally movable according to the force exerted on the sleeve axial force relative to the cylinder wall, wherein the sleeve covers at least a portion of the fluid-filled chamber when the shock absorber is fully compressed.

The invention will now be described by way of example, with reference to the drawings. In the drawings shows:

1 a side view of a prosthetic arrangement for a lower leg prosthesis according to the invention, comprising a tibial component with an upper and a lower part, an ankle unit and an energy-storing foot member;

2 a posterior sectional view of the parts of the tibial component and the ankle joint mechanism taken along a plane containing the axis of the parts of the tibial component; and

3 a transverse sectional view of the arrangement, the 1 and 2 when viewed from below and along a plane through the lower part of the tibial component.

It will be on the 1 to 3 Referenced. A lower leg prosthesis according to the invention has a foot element 10 with a foot keel 12 who is a rigid bearer 12A includes, and a toe spring 12B and a heel spring 12C as fiber-reinforced plastic leaf springs, which are independent of each other with the carrier 12A are connected. The keel 12 is with a foamed cosmetics 14 dressed.

At the Fußkiel 12 An ankle unit is mounted which has an ankle joint mechanism 18 includes, on which a shin element 20 is mounted. The shin element 20 defines a tibial longitudinal axis 22 , The shin element 20 forms part of a longer prosthetic tibia in the usual way, with the remainder of the tibia, not shown in the drawing, passing through a conventional alignment-connecting pyramid 201 with the shin element 20 connected is. The attachment of the ankle unit 18 on the Fußkiel 12 takes place by means of an ankle flexion pivot shaft 24 that have an ankle joint flexion axis 24A defined in a medial-lateral direction to the anterior region of the tibial element axis 22 runs.

The body 18A the ankle unit forms the cylinder wall 26W and the lower partition 26L of the cylinder 26 ( 2 ) of a piston-cylinder arrangement. The arrangement has a piston 28 with an upper and a lower piston rod 28A . 28B wherein the lower piston rod at a second pivotal connection in the form of a pivot shaft 30 in a journal 28C on the lower piston rod 28B is attached, with the Fußkiel 12 is connected, wherein this second pivot connection, a second medial-lateral axis 30A Defined, in this case, posterior to the flexion axis 24A is spaced. It can be seen that the piston 28 while panning the body 18A the ankle unit around the flexion axis 24A in the cylinder 26 moved essentially linearly.

The cylinder 26 the piston-cylinder arrangement has an upper partition wall 26U which is fixed in the cylindrical housing that passes through the body 18A the ankle unit is formed. The piston 28 divides the interior of the cylinder into an upper and a lower chamber 26A . 26B , These chambers are through two bypass channels 31 ( 3 ), the essential part of each in the longitudinal direction in the cylinder wall 26W extends. cross holes 31C in the cylinder wall 26W complete the connections with the upper cylinder chamber 26A , These two bypass channels 31 . 31C are via respective damping resistor control valves 36 . 38 each having an adjustable opening cross-section and a check valve 36N . 38N contains, with the lower chamber 26B of the cylinder. Each control valve 36 . 38 has a manually rotatable plug 36P . 38P wherein each plug has an axial inner blind bore and a plurality of radial channels 36R . 38R has different cross-sectional areas. When the stopper 36P . 38P in the partition 26L is rotated, get different radial channels 40 to cover with a respective opening 42 in the lower chamber 26B of the cylinder 26 empties. The check valves 36N . 38N are biased in the opposite direction, so that the one control valve 36 the damping of the piston-cylinder assembly in the direction of dorsiflexion and the other control valve 38 controls the damping of the assembly in the direction of plantarflexion. In particular, the check valve 36N of the control valve 36 oriented so that there is hydraulic fluid from the lower chamber 26B in the upper chamber 26A to flow. The check valve 38N of the other control valve 38 is oriented in the opposite direction, giving it hydraulic fluid from the upper chamber 26A into the lower chamber 26B to flow. Accordingly, the opening area of the one, 36 , the control valves effective during dorsiflexion, and the opening area of the other, 38 , the control valves are effective during plantar flexion. (At every valve 36 . 38 are the opening with adjustable opening area and the check valve in the bypass channel, the upper and the lower chamber section 26A . 26B interconnected, arranged in series.) The piston-cylinder arrangement allows a damped continuous yielding movement of the foot element 10 relative to the ankle unit 16 around the flexion axis 24A between the dorsiflexion limit and the plantar flexion limit, due to the abutment of the piston on the lower bulkhead and on the upper bulkhead of the cylinder 26 To be defined. The degree of damping can be independently and manually preset through the respective apertures with adjustable dorsiflexion and plantar flexion opening range, as described above.

In conjunction with the ankle joint mechanism 18 includes the tibial component 20 a telescopic unit that allows elastic axial and rotational movement. The telescopic unit is generally cylindrical with its central axis being the axis 22 of the tibial element, which also coincides with the central axis of the cylinder 26 coincides. Details of the telescopic unit will be described below. In terms of flexion of the ankle joint, the limit corresponds to the dorsiflexion of the ankle joint mechanism caused by the abutment of the piston 28 on the lower partition 26L of the cylinder 26 is defined, an anterior inclination of the axis 22 of the tibial member relative to the vertical when the user is standing on a horizontal surface. The limit of plantarflexion caused by the plant of the piston 28 on the upper partition 26U of the cylinder 26 is defined corresponds to an inclination of the axis 22 of the tibial component posteriorly.

In this embodiment, the anterior and posterior tilt angles are the axis 22 of the tibial component with respect to the vertical at the border of dorsiflexion and plantar flexion, respectively 4 degrees (anterior) and 7 degrees (posterior). The mechanical end stops caused by the installation of the piston 28 at the upper and lower dividing walls of the cylinder define a compliance range over which the ankle-foot prosthesis flexes freely during locomotion and standing.

In this embodiment, the tibial component has 20 an adjustable shin connection 201 in the form of an inverted pyramid shaped to be received in a known pyramidal annular receptacle with alignment screws to adjust the orientation of the interconnected elements. In such an embodiment, in a neutral alignment position, the axis of the remainder of the prosthetic tibia (not shown) coincides with the axis 22 of the tibial element 20 together. Changing the tibial canal orientation at such a junction does not alter the angular size of the yielding area of the ankle as it is controlled by the piston stroke, but it changes the position of the limit of ankle joint flexion with respect to the vertical.

Therefore, it is understood that the size of the angle range is determined by the construction and geometry of the prosthesis and its hydraulic link mechanism.

The ankle joint mechanism 18 and its connection to the foot element 10 are similar to the ankle and ankle prosthesis in the aforementioned WO 2008/071975 and co-pending U.S. Patent Application No. 11 / 956,391 (filed on Dec. 14, 2007). In these earlier applications, further details of an ankle joint mechanism are described which functions in the same manner as the ankle joint mechanism disclosed in the present application. The contents of these earlier applications are hereby expressly referenced. The present prosthesis shares a number of advantages with the prosthetic assembly described in earlier applications. For example, because the ankle joint mechanism allows dorsal-plantar flexion over a limited range of motion with resistance largely damped as opposed to elastic resistance, the ankle can easily flex under a load corresponding to changing activity requirements without generating high reaction forces otherwise cause discomfort and affect the function of the prosthesis. Allowing for movement that is damped and substantially without preload means that the ankle will function in a way that it stays in its last loaded orientation and has no way to reorient itself as the foot is relieved. This feature is advantageous to support foot freedom during the swing phase.

Since it is envisaged that the position of the foot member relative to the tibial member at the dorsiflexion boundary will be defined regardless of the orientation of the assembly in space, and as a gravity dependent determination of the dorsiflexion limit is used, the necessity of a gravity-dependent valve system with an end stop corresponding to the vertical orientation the shin axis avoided. The flexibility of adjustment of this prosthesis allows a change in the rolling dynamics by choosing different stiffness of the toe spring. The range of yielding motion can be changed by changing the relative orientation of the foot member and the tibial member. Allowing movement of the tibial axis anterior to the vertical position is particularly advantageous when climbing stairs and when walking on slopes.

The usual approach of maximizing energy storage and energy recovery has resulted in constructions in which the ankle always has high elastic stiffness. The reduction in stiffness in the proposed manner improves comfort for the user and also helps to maintain the forward momentum of the upper body and thus the mobility ability. Reaction forces around the ankle are largely dissipated, with the result that in particular the desired control and proprioception of the knee and hip in (lower leg) amputated persons are improved.

The shin element 20 , which is formed as a telescopic unit will now be with reference to 2 described.

The shin element 20 consists of two parts: an upper part, which is the alignment connection pyramid 201 contains, and a lower part, by the body 18A of the ankle joint mechanism 18 is formed.

The lower part of the tibial element passing through the body 18A of the ankle joint mechanism 18 is formed, has a hollow upper cylindrical extension 26E the cylinder wall 26W the piston-cylinder arrangement 26 . 28 , In fact, the outer diameter of the upper extension 26E the same as the outer diameter of the cylindrical wall 26W and the ankle body 18A in the area of the piston-cylinder arrangement. The cylindrical extension 26E has an opening on one side 46 in the form of a slot. The cylindrical extension 26E is from a cylindrical outer sleeve 48 and an integral upper cap 48C enclosed in the the alignment-connecting pyramid 201 is included. On the inner surface of the outer sleeve 48 is a cylindrical bearing bush attached, the two parts 50A . 50B has and on the inner cylindrical extension 26E slides. In the outer sleeve 48 is an inwardly projecting pin 50 arranged, with the opening 46 in the cylindrical extension 26E covers, with the attachment of the pin 50 at the edges of the opening to restrict the freedom of movement of the outer sleeve 48 on the inner cylindrical extension 26E serves. The outer sleeve 48 not only can move freely axially (ie a translational movement parallel to the axis 22 but it can also move around the axis 22 of the shin element.

In the cylindrical extension 26E is an axially oriented coil spring 52 arranged, whose upper end portion 52A against rotation in the cap 48C the outer sleeve is secured. The spring also has a tubular lower end portion 52B which is sufficiently large to form a rigid ring which is in the cylindrical extension 26E and the cylinder wall 26W is rigidly fixed, so he has an upper partition 26U of the cylinder 26 the piston-cylinder arrangement forms. In this embodiment of the invention, the upper cylinder partition wall 26U and the rest of the spring 52 including the upper end portion 52A integrally formed from a single metal blank. The feather 52 thus forms a compact elastic component, which is the outer sleeve 48 relative to the cylindrical extension 26E both biased against translational and rotational displacement from an unloaded position. The lower end section 52B the feather 52 which is the upper partition 26U of the cylinder has a central bore with a diameter for receiving the upper piston rod 28A so that it can slide axially and make a slight back and forth movement, if required by the geometry of the ankle joint mechanism.

In this embodiment, the range R ( 1 ) of the relative translational movement allowed by the telescopic unit is about 5 mm. Generally, a range of translational motion between 4mm and 8mm is common. In the unloaded state are the outer sleeve 48 and the body 18A the ankle unit by the spring 52 biased away from each other, leaving the pin 50 to an upper edge of the opening 46 borders.

The feather 52 stops a rotation of the outer sleeve 48 relative to the body 18A the ankle unit elastically stood from a neutral, unloaded position in both directions.

It can be seen in the drawing that the centerline of the telescopic unit defined by the tibial component is substantially vertical when the foot 10 resting on a horizontal surface when the ankle joint mechanism is in a neutral position, ie at an intermediate position between dorsiflexion and plantar flexion, this being the stance phase and the amputated person standing normally on a horizontal surface. The bottom vector and the load line run posterior to the flexion axis 24A of the ankle joint and approximately parallel to the midline of the telescopic unit, here through the axis 22 of the tibial element is shown.

In this embodiment, the centerline of the telescopic unit is about 22 mm behind the flexion axis of the ankle joint (and the load line is about 10 mm behind the axis in the rest position).

Because of the way in which the ankle joint mechanism is self-aligning in that it undergoes dorsiflexion and plantarflexion within In accordance with the above-described limits without elastic bias, the amputee is able to apply significantly higher vertical loads to the prosthesis, and indeed, this increase in stress during flexion of the ankle joint mechanism in the dorsal and plantar directions may extend over substantial portions of the gait cycle, regardless of whether the axis 22 of the shin element (and the center line of the telescopic unit) is vertical or not, with the result that more energy in the spring 52 stored in order to be released on repulsion. The self-alignment of the ankle joint mechanism 18 results in that the center line of the telescopic unit over a majority of the gait cycle is more nearly parallel to the ground reaction vector than is achieved with a rigid ankle or ankle, which is predominantly elastic rather than damped.

In the drawings it can be seen that the center line of the telescopic unit, in this case the axis 22 of the tibial component through which the foot member extends, anterior to the posterior end point of the foot member (ie, the back of the heel) which is about one third of the total length of the foot member.

The dynamic action of the prosthesis during walking will now be briefly explained. When on the heel, the ankle is in a state of dorsiflexion from the rolling movements of the previous step. With increasing load on the prosthesis, the floor reaction force on the heel spring causes 12C in that the telescopic unit is compressed and the heel spring is deflected simultaneously, so that both in the latter and in the axial spring 54 Energy is stored. Simultaneously, the ankle joint rotates toward plantarflexion due to leverage of the floor reaction force applied to the heel spring and the foot moves toward a flat footed condition. The combination of a hydraulic damping resistance against such rotation and the resistance of the heel spring 12C and the axial spring 54 Provides a smooth and progressive load transfer to the prosthesis at the beginning of the stance phase. In general, ankle plantarflexion does not reach the plantar flexion limit set by the prosthetic joint mechanism at this stage. When unrolling and towards the toe repulsion, the main leaf spring begins 12B to bend. This happens as soon as the load on the leaf spring 12B and the resulting movement on the ankle causes a hydraulically damped dorsiflexion of the ankle and ensures smooth rolling while maintaining the body's momentum and improving knee function. Towards the end of the unwinding phase, the dorsiflexion limit set by the ankle joint mechanism is reached. As this happens, mechanical energy increasingly becomes the main leaf spring 12B of the foot member to provide energy return for the butt and the telescoping unit of the tibial component 20 is expanded when in the axial spring 52 stored energy is released, and contributes to the repulsion. The swing phase is initiated with an oriented foot at the endstop of the dorsiflexion to provide toe freedom during the swing phase. At the beginning of the swing phase is the telescopic unit of the tibial component 20 completely expanded. While the compliant components of the prosthesis, ie, the springs and the ankle joint mechanism, reach their respective travel limits during the prosthetic function described above, the relative size ratios of their displacements vary in overall motion of the upper portion of the tibial component.

In summary, the lower leg prosthesis described above is a prosthetic system that allows continuous yielding over a limited range of plantar and dorsiflexion. This yielding is achieved by a hydraulic damper connected to conventional foot elements (i.e., the keel, the beam, and independent carbon fiber composite heel and toe springs). This allows free flexion of the ankle continuously over a limited plantar and dorsiflexion area by means of the hydraulic damper and with minimal interference from the elastic elements during walking and standing. During standing, the relative positions of the hip, knee and knee centers are such that a substantially normal posture can be maintained while standing, automatically balancing the forces around each joint thereby providing stability to the limbs. In addition, the self-alignment action of the foot-ankle system facilitates better control of energy transfer between limb segments during locomotion, with the user's hip joint as the main driver and the knee joint as the main mechanical energy transfer tug, thereby facilitating energy transfer to and from the telescopic unit of the Shin element is further facilitated. This biomimetic method of stabilizing stability and equilibrium control has another advantage in that, due to the yielding function of the hydraulic components when standing on slopes, there are no significant moments of reaction around the ankle that cause misbalance between the joints and discomfort can. Because the ankle can move freely due to the limited range of hydraulic compliance, the adjustment for walking and standing on slopes and footwear with different heel heights is done automatically. Another advantage of the system is a smoother and more progressive transition when unrolling on different terrains.

In view of achieving a wide applicability of the above-described prosthetic arrangement compactness and in particular a minimization of the overall height by incorporating the hydraulic bypass channels of the piston-cylinder assembly in the diameter of the cylindrical inner part of the telescopic unit are achieved, so that the outer diameter of the inner part at least can be maintained at the level of the lower partition wall of the cylinder, thereby allowing the outer sleeve to cover the cylinder when the telescopic unit is fully compressed. A minimization of the height and simplicity are supported by the integral design of the coil spring and the upper cylinder partition of the piston-cylinder assembly. The location of the control valves 36 . 38 in the lower partition wall of the piston-cylinder arrangement also ensures a compact solution. Another advantageous feature is the integral, one-piece construction of the body 18A the ankle unit and the cylindrical housing passing through the upper extension 26E the cylinder wall 26W is formed. In this way, the cylinder wall forms 26W a portion of the lower portion of the tibial member having an outwardly facing cylindrical bearing surface which extends downwardly and coincides with the cylinder chamber of the piston-cylinder assembly. Another space saving results from the elimination of the separate torsion bar spring, which provides torsional elasticity, as well as the associated housing by the coil spring is used for both the translational and rotational movement as an elastic biasing means.

Claims (22)

A tibial prosthesis comprising a tibial member defining a tibial member axis, a foot member, and an ankle joint mechanism connecting the tibial member to the foot member, the ankle joint mechanism providing a continuously hydraulically damped portion of ankle flexure and being configured and arranged such that at least over part of the region Damping resistance is the predominant resistance to flexion, and wherein the tibial component has an upper part and a lower part, which are elastically connected to each other so that they can translate relative to each other according to the axial load of the tibial component, wherein the direction of relative movement is substantially vertical when the foot rest in an unloaded state on a horizontal support surface. The prosthesis of claim 1, wherein the tibial member is in the form of a telescopic unit, wherein the upper part of the tibial member and the lower part of the tibial member have an outer sleeve and a cylindrical housing slidably received in the sleeve, and wherein the ankle joint mechanism is a hydraulic piston and cylinder. Arrangement, which is contained in the cylindrical housing so that it lies within a cylindrical housing defined by the cylindrical casing, whereby the sleeve can cover at least a part of the piston-cylinder assembly when the telescopic unit is fully compressed. The prosthesis of claim 2, wherein the telescopic unit has a longitudinal axis and wherein the ankle joint mechanism comprises a hydraulic linear piston and cylinder assembly having a central axis substantially aligned with the longitudinal axis. The prosthesis of claim 3, wherein the piston-and-cylinder assembly has a cylinder with a lower divider wall and an upper divider wall and a cylinder wall connecting the upper and lower divider walls. A prosthesis according to claim 4, wherein the cylinder has a variable volume upper and lower chamber area and the chamber areas are separated by a piston and interconnected by at least one bypass passage containing a valve, the or each valve located in the lower dividing wall. A prosthesis according to any one of claims 2 and 4, wherein the piston-and-cylinder arrangement has a cylinder with first and second variable volume chamber areas and the chamber areas are separated by a piston and connected by at least one bypass passage enclosed in the cylindrical enclosure. A prosthesis according to claim 4 or claim 5, wherein the telescopic unit comprises an axial coil spring arranged to compress when the unit is subjected to an axial load, the coil spring and the piston-and-cylinder arrangement being in a superior condition. Inferior ratio are arranged. A prosthesis according to claim 7, wherein the coil spring and the upper partition wall of the cylinder are formed by a monolithic element received in the cylindrical housing. A prosthesis according to claim 7 or claim 8, wherein the coil spring has first and second ends respectively secured against rotation in the upper and lower parts of the tibial member, and configured to act both as a compression spring and a translational one Withstands relative movement of the parts of the tibial element, as well as a torsion spring that withstands a relative rotation of the parts of the tibial component. The prosthesis of claim 1, wherein the ankle joint mechanism defines a medial-lateral ankle joint flexion axis and the tibial component comprises a telescopic unit in which the portions of the tibial component are relative to the midline direction of the telescopic unit that is within 30 mm of the ankle joint flexion axis can slide to each other. The prosthesis of claim 10, wherein the midline of the telescopic unit is posterior to the ankle joint flexion axis. A prosthesis according to claim 10 or claim 11, wherein the centerline of the telescopic unit extends a distance between 0.2 L and 0.4 L anterior to the posterior end point of the foot member through the foot member, L being the total length of the foot member between its anterior and posterior End is. A prosthesis according to any one of the preceding claims, wherein the ankle joint mechanism defines an ankle joint flexion area extending from a dorsiflexion boundary between 2 ° and 5 ° with respect to the standing condition and a plantar flexion boundary between 5 ° and 8 ° with respect to the standing condition. The prosthesis of claim 1, wherein the cylindrical housing of the tibial member is pivotally connected to the foot member for pivoting about an ankle joint flexion axis. The prosthesis of claim 14, wherein the piston-and-cylinder assembly has a piston with a piston rod connected to the foot member to define a piston rod pivot axis spaced from the ankle joint flexion axis. The prosthesis of any one of the preceding claims, wherein the foot member comprises an energy-retaining fiber-reinforced plastic leaf spring extending from the ankle joint mechanism to a toe region of the foot member. Prosthetic ankle unit comprising the combination: a hydraulic linear piston and cylinder arrangement providing a continuously damped area of ankle flexion and defining a central axis, the assembly including a cylinder wall centered on the axis and enclosing a fluid filled chamber whose volume coincides with the piston movement in the piston Chamber varies, and a telescopic shock absorber, which is coaxial with the piston-cylinder assembly and has an outer sleeve which is slidably received on the outside of the cylinder wall and is elastically connected thereto, so that it is translationally movable according to the axial load acting on the sleeve relative to the cylinder wall wherein the sleeve covers at least a portion of the fluid filled chamber when the shock absorber is fully compressed. The prosthetic ankle assembly of claim 17, wherein the shock absorber comprises a compression spring coaxially mounted in the sleeve and resiliently interconnecting the sleeve and cylinder wall of the piston and cylinder assembly. The prosthetic ankle assembly of claim 17 or claim 18, wherein the sleeve is rotatable relative to the piston and cylinder assembly about the central axis. The prosthetic ankle assembly of claim 19, wherein the resilient connection between the sleeve and the cylinder wall comprises an elastic member that biases the sleeve both translationally and rotationally. The prosthetic ankle unit of claim 18, wherein the fluid-filled chamber is bounded by a transverse partition wall, and wherein the compression spring is a coil spring integrally formed with the partition wall. The prosthetic ankle unit of any of claims 17 to 21, comprising a foot member and a tibial member, the piston and the cylinder wall each being pivotally mounted to the foot member, and wherein the shock absorbing sleeve forms part of the tibial member.

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