Drawings
The foregoing aspects of the invention and a better understanding of the invention will become apparent from the following detailed description of the exemplary embodiments and the claims when read in connection with all the accompanying drawings, which form a part of the disclosure of the invention. While the foregoing and following written and illustrated text focuses on several exemplary embodiments of the invention, it should be clearly understood that the same is by way of illustration and example only and that the invention is not limited thereto. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.
The following is a brief description of the drawings, in which:
fig. 1 is a perspective view of the right prosthetic foot according to the first exemplary embodiment of the present invention from just in front and slightly above.
Fig. 2 is a side view of the prosthetic foot of fig. 1 placed within a cosmetic covering of the foot shown in phantom lines, and the prosthetic foot of fig. 1 in position for attachment to an adjoining prosthetic limb on an amputee's leg also shown in phantom lines.
Fig. 3 is a side view of the interior of the prosthetic foot of fig. 1.
Fig. 4 is a top view of the interior of the prosthetic foot of fig. 1.
Fig. 5 is a bottom view of the interior of the prosthetic foot of fig. 1.
FIG. 6 is a schematic view of the ankle joint axis of the prosthetic foot projected on the frontal plane, wherein it can be seen that the ankle joint axis deviates from the cross-section by an angle β with the medial being more proximal than the lateral.
Figure 7 is a cross-sectional view of the ankle brace taken along section VII-VII in figure 3.
FIG. 8 is a schematic representation of the ankle joint axis of the prosthetic foot as projected on a sagittal plane, wherein the ankle joint axis is seen to diverge from the cross-section at an angle θ, with the anterior being more proximal than the posterior.
FIG. 9 is a schematic view of the subtalar joint axis of the prosthetic foot as projected on the sagittal plane showing the subtalar joint axis forming an angle ψ with the cross section more proximal anterior than posterior.
FIG. 10 is a schematic view of the subtalar joint of the prosthetic foot in frontal plane projection, with the medial axis forming an angle ω with the cross-section more proximal than the lateral axis.
Fig. 11 is an enlarged top dorsal view of the prosthetic foot of fig. 1 with hatching added to show the concavity and convexity of the dorsal surface of the foot body for performing foot gait motions.
FIG. 12 is an enlarged plantar bottom view of the body of the prosthetic foot of FIG. 1 with lines added to show the mid-stance (mid-stance) contact area of the foot in the horizontal plane in gait and with hatching to indicate the concavity in the plane of the body for accomplishing foot motion in gait.
FIG. 13 is a cross-sectional view through a lower portion of the midfoot portion of the main body of the prosthetic foot taken along line XIII-XIII in FIG. 2 showing the inclination of the longitudinal arch with the medial side more proximal than the lateral side forming an angle ε with the cross-section.
Fig. 14 is a side view of an integrally formed metal attachment means for a prosthetic foot.
Fig. 15 is a top view of the device of fig. 14.
Fig. 16 is a top view of the lower web of the device of fig. 14.
Fig. 17 is an ankle device of the invention with a bracket attached to its top surface for providing attachment to an existing low profile Seattle or similar prosthetic foot useful as a means for foot function enhancement, the combination forming another embodiment of the improved prosthetic foot according to the invention.
Figure 18 is a side view of the right side of the ankle apparatus of figure 17.
Figure 19 is a front view of the ankle device of figure 17.
Figure 20 is a side view of the left side of the ankle device of figure 19.
Figure 21 is a rear view of the ankle device of figure 17.
Figure 22 is a bottom view of the ankle device oriented as shown in figure 21.
FIG. 23 is a dorsal view of the ankle device similar to FIG. 21 but showing in phantom a T-nut embedded in the resilient body of the ankle device for attaching the ankle device to the prosthetic foot using a bolt.
Fig. 24 is a top view of the T-nut shown in phantom in fig. 23.
FIG. 25 is a side view of the T-nut of FIG. 24 and a bolt installed therein.
FIG. 26 is a top view of a conventional low profile Seattle or similar prosthetic foot cut longitudinally along line XXVII-XXVII.
Fig. 27 is a side view of the prosthetic foot of fig. 26.
Fig. 28 is a side view of a prosthetic foot according to another embodiment of the invention.
Fig. 29 is a perspective view of the left prosthetic foot of the invention from the medial, superior and toward the left.
Fig. 30 is a top view of the prosthetic foot of fig. 29.
Fig. 31 is a medial side view of the prosthetic foot of Figs. 29 and 30.
Detailed Description
Referring now to the drawings, the prosthetic foot 1 in the first exemplary embodiment of the invention comprises a body 2 of resilient, semi-rigid material (plastic in this embodiment) formed by a forefoot portion 2A, a midfoot portion 2B, and a hindfoot portion 2C, respectively. As shown in fig. 2, the foot trim cover 3 surrounds the body 2. The body 2 in the disclosed embodiment is manufactured by molding or pouring the material for manufacturing the body into a female mold. However, other methods may be used to manufacture the body 2, such as machining a solid resilient, semi-rigid body, or a combination of, for example, molding and machining. The plastic of the body 2 is in the described embodiment synthetic plastic polyurethane, but other plastics or synthetic materials may be used. The body 2 of the foot is sized and designed to facilitate an ability to mimic the smooth effects of the dynamic response of the human foot's hindfoot tri-planar, forefoot bi-planar, and hindfoot, midfoot and forefoot motions, as will be described further herein.
The hindfoot triplanar motion function is achieved by a hindfoot portion 2C that includes a first joint 4 and a second joint 5 that allow closed kinetic chain motion of the prosthetic foot in gait. The first joint 4 serves as an ankle joint. The second joint 5 serves as a subtalar joint (subtalar joint). The ankle joint axis of rotation 4A is oriented to permit motion of the hindfoot portion 2C about the joint axis 4A at least substantially in the sagittal plane. More specifically, referring to FIG. 4, the ankle joint axis 4A is preferably rotated outwardly from a normal to the long axis X-X of the foot by an angle α of 8-30. Referring to fig. 6, the ankle joint axis 4A deviates from the cross-section by an angle β of 8 ° with the medial being closer to the body center than the lateral. This orientation of the ankle joint axis of rotation allows the prosthetic foot to mimic the ability of the human foot to move in the sagittal and frontal planes of the ankle joint.
The prosthetic foot is unable to perform movements in an open loop (open chain) because there is no muscle control. However, in closed kinetic chain motion, dorsiflexion with abduction is manifested as a forward motion of the leg on the foot with inward rotation of the leg. Plantar flexion with adduction is represented by a posterior movement of the leg on the foot with outward rotation of the leg. The ground reaction forces produce these motions as the prosthetic foot 1.
The ankle joint 4 and the subtalar joint 5 are provided integrally with the hindfoot portion 2C by struts 4B and 5B, respectively, of resilient material of the hindfoot portion. Each strut extends in the direction of its respective joint axis. The anterior and posterior side surfaces of the ankle joint strut 4B and the medial and lateral side surfaces of the subtalar joint strut 5B are concavely curved to transfer and absorb forces in the motion of the hindfoot portion about the ankle joint axis and the subtalar joint axis. Concave curved shape of the pillar 4BThe front side surface of the shape is formed by the periphery of a hole 6 extending through the hindfoot portion 2C along the front side of the strut 4B. Diameter d of hole 6 of foot 11Is 5/8 inches, but it may vary depending on the overall size of the body 2 of the foot 1.
Anterior to the hole 6 is a slot 7 that allows the hindfoot portion 2C to move about the joint axis 4A. The height 8 of the gap 7 is selected so that the lower surface of the body 2 adjacent the gap 7 acts as a stop against the opposing upper surface defining the gap, thereby limiting the amount of motion of the hindfoot portion 2C in dorsiflexion of the foot about the ankle joint axis 4A. The wider the anterior gap, the greater the potential for range of dorsiflexion motion. The hole 6 in the embodiment described extends in a direction parallel to the joint axis 4A.
The posterior portion of the ankle strut 4B of the hindfoot portion 2C in this exemplary embodiment is 11/2-2 inches in diameter d2But it may be varied and determined according to the overall size of the body 2. For example, diameter d for a baby or child's foot2And may be smaller. The most central surface of the concavity 9 preferably extends in a direction parallel to the ankle joint axis 4A. The distal surface of the concavity 9 may extend in a direction parallel to the ankle joint axis 4A or in a direction parallel to the frontal plane. This curvature is necessary to absorb shock and allow free plantar flexion range of motion around the ankle joint. Referring to fig. 7, the width w and thickness t of the plastic ankle brace 4B may vary depending on the density, hardness, and other characteristics of the material used in order to provide ankle joint motion capability. For example, a prosthetic foot that exceeds (i.e., includes) the knee requires different motion characteristics than a prosthetic foot that is below (i.e., does not include) the knee.
It is known in the field of prostheses that the heel lever generates a bending moment and the toe lever generates a stretching moment. As a result, there are different motion requirements for the over the knee prosthetic foot and the under the knee prosthetic foot. Thus, a prosthetic foot above the knee may have a different radius of curvature for the posterior ankle concavity and may be made of a lower density material. This effectively reduces the heel lever and the bending moment associated therewith. Referring to FIG. 8, the ankle joint axis 4A projection in the sagittal plane is inclined from the transverse plane by an angle θ with the anterior portion closer to the center of the body than the posterior portion. In the disclosed embodiment the angle theta, like the angle beta in fig. 6, is 8 deg..
The subtalar joint 5 of the prosthetic foot 1 is spaced below the ankle joint 4 and extends in a different direction than the ankle joint 4. The subtalar joint axis 5A extends along the subtalar joint strut 5B and is oriented to allow motion of the hindfoot portion 2C about the joint axis 5A in three planes, the frontal, cross and sagittal planes, although primarily in the frontal and cross planes. The joint axis 5A enters the hindfoot portion 2C from the posterior, plantar, and lateral sides and is directed toward the anterior, dorsal, and medial sides. Preferably, the projection of the joint axis 5A in cross section is inclined by an angle Δ of 9 to 23 with respect to the longitudinal axis of the foot X-X in fig. 41. This angle Δ in the exemplary embodiment1Is 23. Referring to fig. 9, the projection of the joint axis 5A in the sagittal plane (the oblique axis of the joint 5) forms an angle ψ of 29 ° to 45 ° with the cross section, as seen in the direction of the arrow B in fig. 1. In the embodiment of the present disclosure, the angle ψ is 30 °.
The subtalar joint 5 is defined medially and laterally by respective holes 10 and 11 extending parallel to the joint axis 5A. Diameter d of the hole3May vary depending on the overall dimensions of the body 2. Which in the exemplary embodiment is 3/16 inches. Medial and lateral gaps 12 and 13 extend outward from holes 10 and 11, respectively, along the subtalar joint to the periphery of the main body 2 of the foot to permit motion of the hindfoot portion 2C about the joint axis 5A. The height 14 of the medial gap 12 and the height 15 of the lateral gap 13 are selected so that the lower surface of each gap forming the hindfoot portion 2C acts as a stop against the opposite upper surface forming the gap to limit the amount of flexion or rotational movement of the hindfoot portion about the joint axis 5A in eversion or inversion in gait. The height 14 of the middle slit is preferably greater than, such as twice the height 15 of the side slits. In the exemplary embodiment height 14 is 1/8 inches and height 15 is 1/16 inches. Referring to fig. 10, the projection of the joint axis 5A on the frontal plane is inclined at an angle ω from the cross-section, as seen in the direction of the arrow a in fig. 2, with the medial to lateral ratioThe lateral part is closer to the center of the body.
The subtalar joint axis of rotation 5A of the prosthetic foot 1 mimics the human foot's subtalar joint in function. The significance of the longitudinal axis of rotation 5A of the joint 5 being oriented 9-23 outward from the long axis of the foot is in the function of allowing motion of the medial, lateral or frontal plane. The amount of movement possible at the frontal plane of the prosthetic foot at the joint 5 is limited by the height of the medial and lateral subtalar joint gaps 14 and 15. Because the subtalar joint around the human foot generally functions with a range of motion of 20 inversion and 10 eversion, it is preferred that the width of the medial gap 14 of the prosthetic foot 1 be twice that of the lateral gap 15 to allow a greater range of inversion than eversion, as previously described.
The bent portions formed by the holes 10 and 11 at the middle and side of the pillar 5B prevent the plastic from being broken by reducing stress concentration. Referring to fig. 9, the oblique axis of rotation of the subtalar joint allows the joint to act as a mitered hinge. A simple moment transducer is formed and rotation of the leg or vertical section connected to the foot 1 will cause almost equal rotation of the horizontal section (when ψ is 45 °). This orientation will improve the cross-sectional and frontal plane motion capabilities. When the angle ψ of the oblique axis of the subtalar joint 5 is 30 instead of 45, this axis approaches the horizontal plane twice as much as the vertical plane and with a given rotation of the leg about its longitudinal axis the foot motion in the frontal plane is twice as much as the foot motion in the cross section. The importance of the cross-sectional motion function at the lower joint 5 is to absorb the moment of the cross-section, reduce shear forces on the socket surface from the residual limb, and avoid the need to add a separate moment absorber to the prosthetic foot.
The average cross-sectional rotation of the person's lower leg when walking is 19. The subtalar joint is the mechanism in the human foot that allows this 19 rotation to occur in the prosthetic foot 1 as well. The closed kinetic chain motion of the subtalar joint 5 in the foot 1 maintains varus in the frontal plane with supination (pronation) and valgus with pronation (pronation). The functional range of subtalar joint motion in gait is 6 ° total motion. In the case where only 6 of frontal plane motion is required in the prosthetic foot 1, it is possible to tilt the tilt axis of the joint 5 toward the upper end of the range of 30-45 to obtain comfort benefits.
The hindfoot portion 2C of the foot 1 is also formed by a heel 16 having a posterior lateral corner 17, the posterior lateral corner 17 being more posterior and lateral than the mid-heel corner to encourage hindfoot eversion during the initial contact phase of gait. As shown in FIGS. 4 and 5, the rear of the heel 16 is a duck-tail shaped torsion bar and its side rear corners 17 are offset more rearwardly than the middle corners by a distance 1 of 1/2-3/4 inches1. For example, a smaller angle Δ of 16, or positioning the subtalar joint strut 5B closer to the center as will be discussed later, will also cause the heel angle 17 to be offset laterally a distance 12 of 1/2 inches more than the projected axis of the subtalar joint. This 1/2 inch lateral offset predisposes the hindfoot to the heel strike to cause eversion of the subtalar joint. This initial contact subtalar joint eversion acts as a shock absorber to eliminate the effects of heel strike. In addition, referring to fig. 2 and 3, the shape of the posterior lateral corner of the foot in the sagittal plane is curved upward, with a radius of curvature of 11/2 to 3 inches in embodiments of the present disclosure. The radius of curvature may vary depending on the overall size of the foot. The large radius of curvature allows the posterior lateral corner to deflect paraxially at heel strike, which also acts as a shock absorber. The density of the plastic of the rear surface of the body 2 of the foot 1 can also be chosen to be lower than the density of the plastic of the rest of the foot body to create greater shock absorption capacity.
The top 23 of the hindfoot portion 2C of the prosthetic foot 1 is made flat and a metal connector 18 is embedded in the plastic. The metal component 18 in the foot 1 is made of stainless steel, but other high strength, light weight metal alloys, such as titanium alloys, may be used. As shown schematically in fig. 2, the device 18 allows the prosthetic foot to be attached to a prosthetic element 24 secured to a limb of a person positioned over the foot. The lower portion 19 of the connecting means 18 is embedded in the material of the hindfoot portion 2C when molded. Preferably, the lower portion 19 has a plurality of holes therethrough to assist in securing the device in the moulded elastomer of the body 2 during moulding. As shown in the figures, in an embodiment of the present disclosure, the connection means comprises an upper pyramid connection plate 20 connected in spaced relation to a lower connection plate 19 by a plurality of fasteners 21. Alternatively, the upper and lower connecting plates and connecting elements may be made as one piece, as shown in fig. 14. As shown in the figures, the attachment device 18 is positioned in the hindfoot portion 2C along the longitudinal axis X-X of the foot 1.
The metal connecting device 18 in fig. 14 includes an integrally formed lower connecting plate 19 ', upper pyramid connecting plate 20 ' and connecting strut 21 '. The lower disk 19' is formed with an 1/8 inch proximal offset 41 on the front blade and with medial and lateral offsets 42 and 43, respectively. The central and lateral apertures 44 and 45 and the front and rear apertures 46 and 47 are used to secure the device in the plastic body 2 when moulded. Line C-C through holes 44 and 45 is rotated 8 to 30 outward from normal to the sagittal plane X-X with the medial being more anterior than the lateral. Preferably, this line C-C is offset posteriorly by a distance X' from the middle or equal orientation D-D such that the holes 44 and 45 are located at the middle of the ankle joint axis strut 4B. The rearward offset of holes 44 and 45, along with rear hole 47, can be counted as the length of the toe lever. These features may also be used for device 18 where fastening elements connect separate upper and lower connection pads 19 and 20.
The dorsal surface of the midfoot portion 2B anterior to the gap 7 is formed with a dorsal concavity 25 to allow dorsiflexion of the foot between the midfoot portion 2B and the forefoot portion 2A as weight is transferred to the anterior portion of the prosthetic foot in gait. A metatarsal arch convexity 26 is formed on the dorsal surface of the midfoot portion 2B and from the middle of the dorsal concavity 25. In addition, a concavity 27 is formed on the dorsal surface of midfoot portion 2B and forefoot portion 2A for functionally mimicking a fifth optical axis of human foot motion. See figure 11 for different shades illustrating the position of the concavities 25 and 27 and of the convexity 26 on the back surface of the body 2. The longitudinal axis Y-Y of the concavity 27 is oriented at an angle Y of 35 to the longitudinal axis X-X of the foot with the fifth optical axis of the medial being more anterior than the lateral to functionally mimic gait motion as the lower gear axis (lower gear axis) of the incline of the second to fifth metatarsals of the human foot. The angle Y may be less than 35 °, but is preferably in the range of 15 ° to 35 °.
Referring to fig. 12, the plantar (plantar) surface of the body 2 of the foot 1 has a longitudinal arch 28 which includes a concavity 29 near the position corresponding medially to the base of the navicular and the fourth metatarsal on the side of the human foot, the longitudinal axis of which is oriented perpendicular to the Z-Z axis, the first optical axis of motion of the human foot, so as to mimic its function, see fig. 12, where the position of the concavity is indicated by shading attached to the plantar view of the body 2 of the foot 1. The Z-Z axis in the exemplary embodiment makes an angle Σ of 45 with the longitudinal axis X-X of the foot, with the medial portion being more posterior than the lateral portion. The angle Σ may be less than 45 °, but is preferably between 30 ° and 45 °. Using a lower value for a particular range of angles Y and Z will reduce the difference between high-speed (high gear) and low-speed (low gear) operating methods. The latter may be used, for example, for high amputees. As shown in fig. 12, the plantar surface of the foot 1 at the front of the longitudinal arch concavity further includes a cupped region 30 of the posterior surface of the forefoot plantar surface contact area which is generally the annular metatarsal arch concavity or is contoured by 31. The outline of the contact area of the hindfoot is indicated by 31'.
Referring to fig. 12, the longitudinal arch 28 itself is formed with a concavity having a longitudinal axis a-a that is offset in projection at the frontal plane by an angle Σ of 25 ° to 42 °, with the medial being higher than the lateral to produce frontal and sagittal plane motion functions such as the midtarsal bones of a human foot, see fig. 13. The medial surface 32 of the longitudinal arch concavity is of larger radius and closer to the center of the body than the lateral surfaces 33 of the concavity. The longitudinal axis B-B of the anterior surface of the longitudinal arch concavity is oriented at an angle η of 35 to the longitudinal axis X-X of the foot with the medial being more anterior than the lateral. The longitudinal axis A-A of the medial surface of the longitudinal arch concavity is oriented perpendicular to the longitudinal axis X-X of the foot.
The longitudinal arch 28 is provided with the three-dimensional sector to create a specific motion effect of the foot in gait. The anterior longitudinal arch concavity is engaged by the first optic and metatarsal arch concavities 29 and 30. This combination of profiles enables the anterior longitudinal arch concavity to be more anteriorly and medially oriented to enhance the high speed dynamic response capability of the body 2. Referring to fig. 12, the longitudinal axis C-C of the posterior surface of the longitudinal arch concavity is offset from the frontal plane by an angle k of 30 deg. with the medial side more posterior than the lateral side.
The midfoot portion 2B is made of a semi-rigid material as described above and forms the longitudinal arch 28 of the resilient body 2 to create a dynamic response function of the foot in gait such that the medial aspect 32 of the longitudinal arch has a relatively higher dynamic response capability than the lateral aspect 33 of the longitudinal arch. As a result of these and the foregoing features of the foot 1, there is a biplanar motion potential in the midfoot portion 2B corresponding to the midtarsal region of the human foot where motion occurring in the frontal and sagittal planes when adapting to the distal foot position in gait enables the forefoot portion to maintain plantar grade. The oblique medial axis of the midfoot portion 2B is supinated during the propulsive phase of gait. The smooth effect of the plantar aponeurosis acting with the heel cortex during propulsion helps the supination of these oblique medial axes. Only 4-6 of frontal plane motion is required to maintain plantar grade in gait. The physical properties of the prosthetic foot, as well as its surface shape, dictate the motor potential results. The longitudinal arch area of the prosthetic foot 1 is shaped specifically to achieve a better functional motion result. The deviation of the longitudinal arch from the sagittal plane as described above enhances the frontal plane motion and dynamic response characteristics of the foot 1.
The proximal portion of midfoot portion 2B is made planar to receive the force of the anterior ankle joint dorsiflexion stop adjacent gap 7. The midfoot portion 2B is thicker than the forefoot portion 2A. The midfoot medial surfaces 32 and 26 are thicker than the lateral surfaces 33 and 27. The bottom of the foot 1 is formed to accommodate a heel height of 3/8 inches or 3/4 inches. As mentioned above, the plantar surface of the body 2 in the forefoot and midfoot junction areas has a metatarsal concave cupping area 30. The cup-shaped area is used to make contact at the outer rim of the cup. The rise region 31 extends parallel to the axis of motion, Y-Y in fig. 11 of the fifth leg.
The forefoot portion 2A of the main body 2 has two expansion joints 34 and 35 inserted into the rear end of the forefoot portion. The medial expansion joint 34 extends longitudinally to pass right through the posterior point of contact of the ground with the plantar surface of the midfoot into the cupped depression area 30 where it terminates in an expansion joint hole 36. The side expansion seams 35 extend further back into the forefoot than the middle expansion seam, where they terminate in an expansion seam hole 37. As a result, the two expansion joints function as if they were a high gear and a low gear in the human foot. As shown in FIG. 12, the line B-B connecting the two expansion joint holes 36 and 37 is offset outwardly from the long axis of the foot by an angle η of 35. Because the ankle joint is located a shorter distance from tilt axis B-B on the lateral side than the medial side, this axis is first used to lift the heel before switching to the high gear function. The function of passing through the top gear or medial side and exiting results in pronation of the forefoot toward the rearfoot position and increases the weight load under the medial aspect of the forefoot. Thus, forefoot portion 2A functions to allow biplanar forefoot motion to occur.
More specifically, expansion seams 34 and 35 allow dorsiflexion, inversion, plantar flexion, and eversion, respectively, of the forefoot. This two-plane motion capability maintains the slope of the forefoot plantar surface on uneven plantar surfaces. In this regard, foot 1 mimics a human foot. When the hindfoot portion 2C changes position, the forefoot and midfoot portions also need to change positions in opposite directions. This opposing twist maintains the slope of the sole.
The prosthetic foot 1 worn by the amputee acts as a closed loop prosthetic device that responds to the ground forces generated in human gait. In the initial contact phase of gait, the heel strike the ground laterally. The design of the posterior heel area deviates from that discussed above to transfer weight through the upwardly biased duck tail expansion to absorb the heel lever forces that create the calf bone bending moment. Further enhancement of the moment absorbing characteristics and further improvement of the shock absorbing characteristics in the foot 1 are obtained by the posterior concavity 9 and the lateral deviation 1 of the heel towards the rotation axis of the subtalar joint 52To achieve that eversion of the subtalar joint occurs as force is applied. The eversion acts as a shock absorber to dampen the initial contact weight during the transfer phase of gait. Further, applying force posteriorly to the axis of rotation 4A of the prosthetic ankle joint 4 causes the ankle joint to plantar flex and the midfoot portion 2B and forefoot portion 2C of the foot to be closer to the ground.
As shown in FIG. 12, with respect to the plantar weight bearing surfaces 31 and 31' of the foot, the ground reaction forces push the plantar surface of the prosthetic foot 1 forward as weight is transferred from the heel portion to the forefoot portion throughout the stance phase of gait. The subtalar joint 5 allows the foot 1 to generate motion in three cardinal planes, i.e., the transverse, frontal, and sagittal planes, corresponding to human motion when weight is transferred through the hindfoot portion 2C. This triplanar motion capability is obtained due to the orientation of the prosthetic foot's subtalar joint axis of rotation 5A which is offset from the transverse, frontal and sagittal planes as described above. This orientation allows for motion capability in these three planes. The composition in the sagittal plane is less than in the frontal and cross-sectional planes. The reduced motion of the subtalar joint 5 in the sagittal plane is compensated for by the ankle joint 4 being located just proximal to the subtalar joint.
The ability of the subtalar joint to allow motion to occur in the cross-section is important because in the stance phase of gait, the lower extremity, which passes primarily through the subtalar joint, must absorb 19 ° of the cross-sectional motion transmitted through the tibia and fibula, to the ankle joint, and then to the subtalar joint. The subtalar joint 5 acts as a mitered hinge and transfers this motion to the hindfoot portion 2C and midfoot portion 2B. This motion is absorbed in the midfoot dynamic response properties and the midfoot-forefoot biplanar motion function. As a result, improved plantar surface weight bearing characteristics are obtained. As the weight transfer line moves forward in the foot and approaches the ankle joint 4, the ground reaction forces cause the ankle joint to plantar flex until the entire foot strikes the ground, before the foot flattens in the stance phase of gait. This plantar flexion motion is achieved by the expansion or further opening of the ankle joint anterior slot 7 and the compression of the posterior ankle joint concavity 9.
Once the foot 1 is flattened on the ground, the weight is transferred to the ankle joint 4. As weight is transferred more forward in the foot, the anterior dorsiflexion gap 7 engages and inhibits further dorsiflexion motion. That is, the motion is inhibited by the opposed surfaces forming the anterior ankle joint gap coming together. The larger the gap 7, the greater the potential for dorsiflexion motion. It is important to prevent weight transfer to the anterior ankle joint adjacent to gap 7. Where the weight is transferred to the midfoot portion 2B of the foot 1. As a result, the longitudinal arch 28 area of the foot 1 is loaded and it responds by expanding and absorbing these vertical forces through its concavity. The result is more shock absorbing properties and dynamic response capability.
The medial longitudinal arch region of the proximal axis has a much larger radius than the lateral ends. As a result, the medial has increased expansion potential and higher dynamic response than the distal lateral longitudinal concavity of the arch. As weight is transferred even more anteriorly in the prosthetic foot 1, near the medial aspect of the first ray longitudinal axis of rotation (Z-Z in FIG. 12), the weight is transferred near the medial frontal plane of the foot.
The plantar and dorsal surfaces of the prosthetic foot 1 are designed to allow or encourage specific motion. In particular, the first ray axis of rotation Z-Z and the motion capabilities associated with that axis in the human foot are mimicked in the prosthetic foot 1 by the plantar surface of the forefoot 2A being formed as a concavity 29. The longitudinal axis Z-Z of the concavity 29 is oriented parallel to the longitudinal axis of rotation of the first ray in the human foot. This direction is rotated 45 ° inwards towards the long axis of the foot, see angle Σ in fig. 12.
The result of the motion from the application of force to the concavity and its particular direction of angulation is vertical shock absorption and improved dynamic response capability. The first ray concavity 29 and the longitudinal arch concavity 28 create a dynamic response capability. These dynamic response capabilities are demonstrated by the ground forces and the concavity extension that transfer weight to the side of the concavity. Accordingly, concavity expansion occurs in the prosthetic foot 1 during gait and once the force is removed, the foot 1 springs back to its original shape to release the stored energy.
The ankle joint 4 and the subtalar joint 5 of the prosthetic foot 1 also have the potential to generate a dynamic response capability. For example, as the ankle joint 4 plantar flexes and the anterior dorsiflexion gap 7 expands and the posterior concavity 9 compresses, energy is stored in the ankle joint strut 4B. Once the vertical force is removed, the strut 4B will return to its normal position.
Thus, the dynamic response of the prosthetic foot 1 in response to ground reaction forces is associated with expansion and compression of the concavity and convexity, and to a lesser extent with the motion that occurs and the design characteristics of the particular joint strut. Struts 4B and 5B form the middle pivot point of the class 1 leverage in hindfoot portion 2C. Each of the ankle and subtalar joint struts has an energy storage function. The physical characteristics and design features produce the dynamic response capability. The application of force will cause the generation of motion. Once the force is removed, the physical properties of the strut return it to its original resting configuration, and a dynamic response occurs as a result. Although the first and fifth axes of the prosthetic foot are not distinct joint axes, the design of the morphology and surface characteristics of the body 2 of the prosthetic foot dictate the mechanical energy motion capabilities so that these specific motions are encouraged to occur as described above.
The interrelationship between the midfoot plantar and dorsal aspects is important in understanding the dynamic response capabilities that exist. In this area of the prosthetic foot 1, the surfaces of the medial and lateral portions are formed into specific shapes and these shapes provide the mechanical energy motion results. In gait, the dorsal fifth ray concavity 27 is compressed, allowing less resisted motion potential. This relates to the low gear principle. The medial midfoot plantar and dorsal surface areas respond to the application of force by expanding as previously described (functionally, the first ray). The expansion improves the impedance properties and as a result, the dynamic response capability is enhanced. This enhanced dynamic response capability is associated with the high gear principle.
The high and low gear principles relate to gait acceleration, deceleration and speed components. The enhanced dynamic response capability of the high gear may be used in gait acceleration and deceleration phases. The low gear principle relates more to the speed of gait than to the aforementioned acceleration and deceleration. The low gear component of the prosthetic foot 1 will allow the amputee to ambulate with low energy consumption while walking at low speeds. This reduction in energy expenditure is associated with two principles, namely the length of the toe leverage system since the length of these toe levers relates to the lengthening moment of the calf shank and to the dynamic response characteristics of the medial and lateral regions of the prosthetic foot.
The high gear has a longer toe lever than the low gear. Less momentum and inertia is generated when the amputee walks slowly. The ability to effectively overcome a long toe lever is less. The center of gravity of the body moves more laterally during a slow walk in the stance phase of gait. With the increased frontal plane motion capabilities of the prosthetic foot 1, the patient's calf shank can be positioned to move into either the low or high gear portions of the midfoot and forefoot areas. If the patient wearing the foot 1 accelerates or decelerates, he will use the higher speed function once a comfortable gait speed is reached. The amputee will seek a region of the forefoot 2A that will maintain the comfortable gait speed. If the amputee wants more dynamic response characteristics, the force transfer will occur closer to the middle, and if less dynamic response characteristics are desired, the force transfer will occur closer to the sides. With the prosthetic foot 1, the amputee has a choice of functional motion outcomes.
The improved total amputee gait pattern is the result of this selective control. As the weight transfer moves further anteriorly in the prosthetic foot 1, the fifth ray axis is replicated by the arrangement of the two expansion joint holes 36 and 37 and the topography and design of the plantar and dorsal surfaces of the body 2 of the foot. That is, the dorsal aspect of the body 2 about the axis of rotation Y-Y of the fifth ray is formed as a concavity 27. The concave excitation motion occurs perpendicular to the long axis direction Y-Y. It is known that the calf bone, tibia and fibula do not progress independently in the sagittal plane in normal gait. It is known that in a mid-stance, the knee or the lower leg bones move laterally while frontal plane motion occurs. This is shown in the human knee by the large surface area of the medial femoral condyle.
The function of the fifth axis of rotation Y-Y in the foot 1 is important. The fifth ray longitudinal axis Y-Y allows motion to occur perpendicular to its longitudinal axis as weight is transferred to the anterior and lateral portions of the prosthetic foot 1. In addition, the two expansion joint holes 36 and 37 are positioned to stimulate forefoot motion on the longitudinal axis of rotation of the fifth ray and, as a result, produce improved biplanar motion capability. The above-mentioned high and low gear effects are also enhanced. As a result, the prosthetic foot gait characteristics are improved and mimic human gait.
The forefoot biplanar features of the prosthetic foot 1 are enhanced by the expansion gaps and expansion gap holes described above. Two expansion slots are strategically placed to create a particular motion capability. That is, referring to FIG. 2, the longitudinal projection of the two apertures onto the sagittal plane is oriented at an angle B of 45 with respect to a line B-B parallel to the frontal plane. This orientation acts as a miter hinge more like a miter hinge of a subtalar joint. The result is an improved two-plane motion capability.
The plantar weight bearing surface 31 of the forefoot 2A and the surface 31 of the hindfoot 2C are also specially designed and shaped. The plantar surface expansion joint holes 36 and 37 are located in the metatarsal arch area 30. As a result, when weight is transferred to the area of the foot 1 corresponding to the metatarsal heads, the weight is loaded on the expansion joint supports 38, 39 and 40. When the weight bearing surface on the plantar surface of the foot 1 contacts the ground, weight is carried by the expansion support, creating a suspension web effect. This allows for a large amount of molding capacity while maintaining the structural stability required for a sufficiently stable foot. Human gait is improved with improved biplanar forefoot motion capabilities of the prosthetic foot.
As the weight transfer moves even further anteriorly into the expansion joint strut area and the ray area in gait, the prosthetic foot 1 is shaped and designed to produce a specific motion effect. The instep and sole surfaces of the above-described region of the main body 2 are formed in an upwardly elongated arch, see fig. 2. The back concave surface is directed to merge into the fifth ray concave surface 27. This combination of shapes, one into the other, facilitates a smooth transition between the latter stance phase and the swing phase of gait. The upwardly formed branch portion functions to evert the toe of the foot during the gait sequence described above.
Although the prosthetic foot of the invention has been described in connection with the first exemplary embodiment, alternate embodiments are possible. For example, there is a spatial relationship between the height of the ankle joint in the prosthetic foot and how this height affects the direction of potential energy at the subtalar joint skew axis. In an embodiment of the present disclosure, the height of the hindfoot portion (surface of the sole to the pyramid attachment surface) is 3-31/2 inches. This height may be greater and the ankle joint location moved closer together. This alternative orientation of the ankle joint allows the oblique axes of the subtalar joints to approach and vary from angles such as 29-30 to 42-45. The 30 orientation of the disclosed embodiment provides increased inversion and eversion (frontal plane motion) and reduced abduction and adduction (cross-sectional motion). Alternate embodiments have the ankle joint located more closely, with a 45 oblique subtalar joint axis allowing equivalent cross-sectional and frontal plane motion. The net effect of the latter orientation will be to reduce varus/valgus frontal plane motion and increase abduction and adduction of the foot compared to the foot of this embodiment. The increase in abduction and adduction will be resisted by ground reaction forces and therefore will result in a decrease in the varus and valgus capacity and an increase in cross-sectional motion.
Another possible variation would be to move the subtalar joint strut further medially in the foot 1 and thus increase the lateral offset 1 in FIG. 41. This will cause the subtalar joint to tend to increase eversion in the initial contact state of gait. The net effect would be to improve the impact absorption capacity. Further, the two expansion joint holes sagittal plane directions may vary from the first illustrated embodiment. These apertures may be offset medially or laterally within the frontal plane. The result of the two holes being non-sagittal is that the expansion joint and expansion struts move more medially and laterally. For example, if the dorsal ends of the two expansion joint holes are laterally offset from the sagittal plane by 20-30 °, the three expansion joint struts tend to encourage dorsally bending and adduction when subjected to ground reaction forces. Deviation from the sagittal plane at 20-30 deg. to the midline in the direction of the dorsal aspect of the expansion joint hole will encourage dorsally bending and abduction of the strut. In addition, it is possible to orient two expansion joint holes so that one hole is offset toward the midline and the other hole is offset laterally. For example, the dorsal direction of the lateral expansion joint hole may be 35 off-set from the sagittal plane toward the midline. This orientation will tend to make the outboard expansion joint struts easier to move toward dorsiflexion and abduction-an improved low gear effect. The medial expansion joint hole dorsal direction may deviate laterally from the sagittal plane by 45 °. This orientation will cause the medial expansion struts to tend to move toward dorsiflexion and to adduct. The net effect will improve the ability of the inboard expansion joint struts to move in relation to the high gear effect.
A still further alternative embodiment of the prosthetic foot has a single expansion joint and expansion joint hole to form only the medial and laterally expanding articular struts. This will increase the stiffness of the forefoot and reduce its biplanar motion capabilities. As discussed previously, the design of this single expansion joint hole may deviate from the sagittal plane as described above. An expansion joint or knuckle may also be provided in the heel area of the foot to improve the plantar surface of the heel supporting the plantar grade over a rough surface. The ankle joint may also be moved below the subtalar joint in the prosthetic foot. This will allow the inclination of the subtalar joint to be increased without affecting the overall height of the foot-a benefit in the version of the low profile of the prosthetic foot.
The main body 2 of the prosthetic foot 1 may also be molded into a hybrid foot using materials of different densities and hardnesses (durometers) in the forefoot and midfoot portions 2A and 2B and in the hindfoot portion 2C. The physical properties of the foot as well as the design characteristics produce its dynamic response capabilities.
A prosthetic foot 50 according to a second embodiment of the invention is shown in FIG. 28. The prosthetic foot 50 includes an ankle device, such as an ankle strut member, 51, which is attached to a conventional low profile Seattle or similar prosthetic foot 52 in accordance with the present invention to improve the hindfoot functional characteristics of the foot. The ankle strut member has a T-nut 53 (see Figs. 23-25) embedded in its top for attaching the member to the foot keel 54 of the foot 52 via a screw 55. The screw extends through a stepped hole 56 in the foot keel and a cosmetic covering 57 of the foot 52.
The shape and functional features of the ankle pylon component are as described for the hindfoot portion 2C of the prosthetic foot 1 of the first exemplary embodiment. Once attached to the top of the prosthetic foot, a posterior concavity 58 is formed. A concave surface 59 with smooth flow lines in the front is also formed as shown in the drawing. As a result of the foregoing description of the first exemplary embodiment in relation to the features of the posterior prosthetic foot 2C, the strut member 51 has a tri-planar (triplanar) posterior foot motion capability. These features include the presence of first and second joints 60 and 61, which act as ankle and subtalar joints, respectively. The T-nut or similar fastener is embedded into the mistal surface of the resilient plastic of the component 51 at the time of manufacture.
The prosthetic foot 60 according to the embodiment of the invention shown in Figs. 29-31 likewise comprises forefoot, midfoot and hindfoot portions as in the previous embodiment description, see for example fig. 3, parts 2A, 2B and 2C. The hindfoot portion of the prosthesis 60 includes an ankle joint 61 to allow closed kinetic chain motion of the prosthetic foot in gait. The ankle joint has a joint axis 61A oriented to permit motion of the hindfoot portion about the ankle joint axis which is at least substantially in the sagittal plane. As in the above-described embodiments, the ankle joint is integrally formed with the hindfoot portion by a strut of resilient material of the hindfoot portion. A hole 62 extends through the hindfoot portion and the periphery of the hole to form the anterior face of the strut. The hindfoot portion anterior to the hole includes a gap 63 to allow motion of the hindfoot portion about the ankle joint axis. The hole 62 is elongated upwardly as shown in the cross-section of the prosthetic foot in the sagittal plane so that the strut is upright and curves facing the anterior aspect of the projection, see fig. 31.
The strut is elongated in the direction of the ankle joint axis 61A and has an anterior face 64 and a posterior face 65 curved anteriorly toward the projection. As with the previously described embodiments, the height of the gap 63 is selected so that the lower surface forming the gap rests as a stop against the opposite upper surface forming the gap to limit the amount of dorsiflexion motion of the hindfoot portion about the ankle joint axis. The aperture 62 is elongated in a direction parallel to the ankle joint axis. The anterior convexly curved strut advantageously provides different characteristics of strut compression and expansion in gait, while the upwardly arched resilient foot of the prosthesis contributes to the dynamic response of the prosthesis, with transverse and vertical guide members to improve the efficiency of the prosthesis in use.
The prosthetic foot 60 has a known commercially available adapter 66 that is attached to the resilient integrally formed prosthetic body to form the foot and ankle by a threaded fastener 67. The adapter comprises a member 68 including a socket 69 for mounting a member, not shown, for detachably connecting the prosthetic foot to the amputee's leg stump. The base 70 of the adapter is located below the member 68. The threaded fastener 67 has an Allen socket 71 at the top for receiving an Allen wrench therein to allow the loosening of the member on the base, which can be rotated relative to the base and prosthetic foot when the threaded fastener 67 is loosened. These associated rotations are in cross section and allow easy access to the foot within critical limits, such as within 1/8 inches.
The socket 69 of member 68 is a square socket with rounded corners for fitting with clearance a square complementary shaped projection/member on a lower limb socket or other part on the amputee's leg stump. See dashed lines in fig. 31. Four unnumbered screws, one in each middle of each side wall of the square socket, can be screwed into and out of the engagement lugs to attach the prosthesis to the support structure of the amputee's leg stump. The clearance between the tab and the socket and the adjustability of the four screw positions of the adapter allow for anterior-posterior, medial-lateral, and angulation or tilt adjustment of the prosthesis and support structure. Instead of the adapter 66, the prosthesis 60 may be provided with another known, commercially available adapter, such as a cone-type adapter, for example as shown in fig. 1-3.
This concludes the description of the exemplary embodiments and possible variations or alternative embodiments. It should be understood, however, that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject arrangement within the scope of the foregoing description, the drawings and the appended claims, and without departing from the spirit of the invention.