US 2692392 A
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Oct. 26, 1954 c. H. BENNINGTON ETAL 2,692,392
ARTIFICIAL LIMB Filed April 5, 1951 FIG. l.
Slwentor CHARLES H. BENN/NGTUN Mm n L L mf .0 E7 M Patented Oct. 26, 1954 UNITED STATS ATENT OFFICE ARTIFICIAL LIME Application April 5, 1951, Serial No. 219,386
7 Claims. l
This invention has to do with an artificial limb and in particular with an artificial limb having an ankle and foot capable of simulating many of the movements of a natural limb.
In normal walking the foot has at least six different movements: dorsal and plantar flexion, pronation and supination in the hind foot, and flexion in both directions of the metatarsals and toes in the forefoot. The problem of providing an artiicial limb capable of all these movements is an old one, and ball and socket joints, bearings, springs, connections of various resilient materials and many other suggestions have been made for simulating the natural movements. The commonest objections to prior artificial limbs have been their inability to perform in a manner comparable to a natural foot, and to stand up under the heavy wear and strain to which they are subjected.
An object of the present invention is to provide in an articial limb a rugged, simple connection between the parts representing the shin bone or tibia and the foot, permitting the foot to be moved in a manner closely resembling that of a natural foot. This object is attained by providing a block of resilient material having rigid plates embedded therein and flexibly connecting the tibia to the foot.
According to other features of the invention the metatarsal section is made flexible, and a heel cord is provided which can be readily adjusted to vary its tension.
rlihese and other features of the invention will be more fully described in connection with the drawings, in which:
Fig. l is a side elevation showing a limb according to the invention;
Fig. 2 is a side elevation of the limb partly in section; and
Fig. 3 is perspective of the pantala-r articulation according to the invention.
Referring to Fig. 2, a foot member lil is made from any suitable hard, relatively light material, such as wood. The anterior portion of the foot has two slots il and lia. Slot l is at a point in the foot corresponding to the break at the base of the metatarsal and slot lia corresponds to the break at the toe joint. Slot IIa is approximately 25% wider at its opening or top il than slot i I, thereby permitting the foot in walking to roll forward to approximate the natural fiexion at the respective joints. In an articial foot for the average male adult, slot II will be e across the opening and slot IIa wide. A cavity I3 in midtarsal section I4 and a cavity l in toe sec- 2 tion I'l register with a hollow portion metatarsal I2. An elongated resilient member I8, of rubber or the like, is loosely inserted in cavities I3 and I t and hollow portion I5. The portion of member I8 lying in metatarsal I2 has a con-cavity d8a to insure firm anchoring of rubber IS in cavities I3, I5 and l5 during walking. A pliable sole I9 recessed in the midtarsal section M and toe section il', is secured with the resilient member i8 to the midtarsal, metatarsal and toe sections lli, I2 and Il respectively by means of screws 2li or the like.
The pantalar articulation comprises a block ZI of resilient material, preferably natural or synthetic rubber, such as that used in first line automobile tires. While block 2l will here and in the claims be referred to as being made of rubber, it is understood that any other material having resilient characteristics such as rubber could be used. By pantalar is meant the joints and tissues surrounding the talus. The term pantalar articulation is used to describe an element which can be moved to simulate most of the movements of the talus and oscalcis. The resiliency of'rubbei' block 2| should be about the same throughout, but the resiliency of each block should preferably vary depending on the age, weight and activity of the wearer of the limb. For instance, in the case of a` normally active adult of 200 pounds for whom the limb being described will be considered, the block should have a durometer reading of 50.
Referring to Fig. 3, the upper surface of block 2l is V-shaped and consists of front portion 22 and rear portion 23 which slope towards the opposed lower horizontal surface. Preferably front portion 22 is slightly, about 12%, longer than. rear portion 23. By way of example some of the dimensions of block 2I are as follows:
(d) Narrowest distance between upper and lower` surfaces (e) Maximum distance between portion 22 and lower surface 115e- (f) Maximum distance between portion 23 andlower surface ha;
(g) Width at juncture of portions 22 and The angle which portions 22 and 23 (the legs of the V) make with one another is determined by the thickness of rubber required between the l5 in upper and lower surfaces of block 2|. This will vary as previously pointed out with the weight, age and activity of the wearer of the limb. However, in all cases it is desirable to keep this thickness to a minimum in order to insure that the pivoting point of the leg will be as close to the foot as possible as in the natural pantalar joints.
A thin plate 24, of the order of 116 thick, of metal or other rigid material, e. g. bronze, is bonded into block 2| just below and parallel to the surfaces of portions 22 and 23. Plate 24 is preferably one piece which has been bent to conform the V-shaped upper surface of the block.
Another plate 25, similar to plate 24, is bonded into block 2| just above and parallel to its flat lower surface. Two bolts 26 are brazed to plate 25 and project therefrom. Two bolts 21 are brazed to the front of plate 24 and project therefrom as do two other bolts 28 brazed to the rear of plate 24.
Bolts 25, 21 and 28, respectively, serve as the means for fastening block 2| to the foot and leg, and plates 24 and 25 the means for anchoring the bolts in the block. While other fastening and anchoring means are possible according to the invention, it is important that the connection between the leg and foot be secure yet not rigid.
The bonding of plates 24 and 25, with their respective bolts extending therefrom, into block 2| may be done in any one of a number of well known ways.
In the embodiment of the invention here illustrated, plate 24 is about 11g" in thickness and plate 25, g3g thick. Plate 25 is preferably made of slightly heavier stock than plate 24 because it is fastened to the foot by only two bolts 26, whereas plate 24 is fastened to the leg by four bolts 21, 28. While both plates are substantially co-extensive with their parallel block surfaces and are embedded in the block about M3 from the nearest outside surface, they could be at a greater or a lesser distance therefrom. The plates could also be merely bonded or otherwise fastened to the upper and lower surfaces of the block. The important point is to guard against thefplates being torn away from the block as a result of the heavy strain to which they are subjected during use of the artificial leg. Embedding them is one good way of preventing this.
The leg, tibia or shin bone is divided into a hollow upper portion 3| and a lower portion 32 which telescopes into portion 3|. By means of bolts 33 and flange 34 on upper portion 3| the position of lower portion 32 may be adjusted therein to vary the length of the leg depending on the requirements of the wearer. Base 35 of portion 32 is V-shaped to correspond to upper surfaces 22 and 23 of block 2|. It will be noted' that edge 36 of front portion 22 extends beyond base 35 because front portion 22 is slightly, about 12%, longer than rear portion 23. The reason for making front portion 22 longer than rear portion 23 is that in plantar exion the front of block 2| undergoes greater strain and must stretch more than in dorsal flexion, because in the latter the heel cord acts as a restraint.
Suitable holes to accommodate bolts 26 extend through foot lil and terminate in cut-out 31 in the bottom of foot l0. Nuts 38 may be screwed onto the ends of bolts 26 and work against a plate 39 to hold the block securely on the foot. Similarly, holes extending through base 35 permit bolts 21 and 28 to extend therethrough and the block is securely held to the lower portion of the tibia by nuts 40.
It will be appreciated that an important feature of block 2| is that it provides in a single, relatively inexpensive unit a pantalar articulation where heretofore a plurality of complicated parts was necessary. Furthermore, block 2| may be easily replaced with another block by the wearer if it becomes Worn or breaks.
A heel cord 42 is connected between a hook 43 formed on bracket 44 secured to the posterior of tibia portion 32 and an adjustable screw mechanism in the heel of the foot. The adjustable screw mechanism operates in a hole 45 extending through the bottom of heel 46 and contains an internally threaded flanged bushing 41 having holes 4B in its flanged end whereby bushing 41 may be turned by means of a Spanner wrench or key (not shown). Ends 49 of cord 42 are secured in an externally threaded ferrule 50 and held therein by an anchored pin 5| which rests against shoulder 52 in pipe 55. Threaded members 41 and 50 cooperate so that when member 41 is turned the tension on heel cord 42 will be varied. It is important that the wearer of the artificial limb can easily adjust the tension of the heel cord himself without recourse to others.
While I have shown cord 42 as made from fibrous material with a leather covering 53, it may be made from any other suitable inelastic material.
It will be appreciated that the metatarsal section, pantalar articulation and heel cord here described combine to provide an artificial limb whose foot portions mechanically simulate many of the movements of a natural foot. While any one of the three above described improvements may be incorporated individually in an artificial limb, the combination of all three of these constitutes an important feature of the invention.
Terms such as tibia, foot, heel, etc. used in the claims designate mechanical simulations which perform some of the functions of the natural members.
What is claimed is:
1. In an artificial foot, 'two slots of different widths in the front portion of said foot defining a metatarsal section, a hole through said metatarsal section and cavities registering therewith in the toe and midtarsal sections of the foot on either side of the metatarsal, and a p-iece of flexible material extending through said hole and cavities.
2. An artificial foot comprising a toe, a metatarsal and a midtarsal section, a first slot between said toe and metatarsal sections, a second slot narrower than said first slot between said metatarsal and midtarsal sections, a hole in said metatarsal registering with cavities in the toe and midtarsal sections, and a piece of flexible material extending through said hole and cavities whereby in walking the front portion of the foot simulates some of the movements of a natural foot.
3. In an artificial limb, a pantalar articulation connected between the tibia and the foot comprising a block of rubber having a V-shaped upper surface and a relatively fiat lower surface, the upper surface contacting the tibia member and divided into a front and a rear portion sloping towards the lower surface, the front portion being of the order of 12% longer than the rear portion, the lower surface of said block contacting the foot member, a first metal plate embedded in said block just below and parallel with the upper surface, a second metal plate embedded in the block just above and parallel with the lower surface, fastening means projecting from both said plates for fastening said block to the tibia and foot members, a heel cord connected between said tibia and the heel portion of said foot, and an adjustable screw in a hole in the bottom of the heel connecting said cord to the heel whereby the tension exerted by said cord may be Varied.
4. In an artificial limb, a leg member having an upper portion and a lower portion telescoping therein to adjust the length of said leg, a foot member, a pantalar articulation between said last two mentioned members comprising a block of automobile tire grade rubber having an upper surface contacting the lower leg member and divided into front and rear portions angularly disposed with respect to each other to resemble a V, said front portion being of the order of 12% longer than said rear portion and extending said amount free from said lower leg member when the upper surface of the block is in contact therewith, the lower surface of said block being substantially flat and contacting the foot member, a rst bronze plate embedded in said block just below and parallel with the upper surface, a second bronze plate embedded in the block just above and parallel with the lower surface, bolts extending from both of said plates for fastening said block to the leg and foot, a heel cord of relatively inelastic material connected between the lower rear portion of said leg and the heel of the foot, an adjustable screw mechanism in a hole in the bottom of the heel for connecting the cord to the heel whereby tension exerted by said cord may be varied, the front portion of said foot being divided by two slots into a metatarsal, a midtarsal and a toe section, the anterior of said slots being of the order of 25% wider at its top than Isaid posterior slot, a hollow portion extending through said metatarsal section and cavities corresponding therewith in said midtarsal and toe sections, a piece of rubber extending through said cavities and hollow portion and having a concavity in the portion in the metatarsal, and a sole of pliable material covering the bottom of said foot portions through which said piece of rubber extends.
5. An artificial foot comprising complementary toe, metatarsal and midtarsal sections having angular end faces disposed in spaced, end to end relation, each of said sections being recessed inwardly of its bottom face, a block of resilient material common to said sections disposed in said recesses in section spanning relation, a yieldable sole member recessed in said toe and midtarsal sections in overlying relation to said resilient material, and a plurality of screws securing said sole member and said block of resilient material to said toe, metatarsal and midtarsal sections.
6. The invention according to claim 5, and in which the surface juncture between said metatarsal section and said block of resilient material is at least in part concavo-convex.
7. In an artincial limb, the combination of a longitudinally adjustable leg member terminating in a il-shaped end portion, a foot member including a toe section and a metatarsal section yieldably connected thereto in spaced end to end relation, a pantalar connection between said V- shaped end portion and said foot member comprisms a block of resilient material having a horizontal bottom face and a complementary V- shaped upper face, a plurality of oppositely extending stud screws bonded in said block securing it to said V-shaped end portion and to said foot member, a rearwardly extending hook member secured to Said adjustable leg member, a shouldered, internally threaded bushing revolvably seated in the heel portion of said foot member ush therewith, and a looped cord having its free ends secured in an externally threaded ferrule adjustably connected to and between said hook member and said bushing.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 809,875 Wilkins Jan. 9, 1906 2,315,795 Johnson et al. Apr. 6, 1943 2,475,373 Catranis July 5, 1949 FOREIGN PATENTS Number Country Date 7,781 Great Britain Apr. 1, 1909 308,671 Germany Oct. 22, 1918 326,131 Germany Sept. 24, 1920 625,528 Great Britain June 29, 1949
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