US3024785A - Femoral head prosthesis - Google Patents

Description

March 13, 1962 M. DOBELLE FEMORAL HEAD PROSTHESIS 2 Sheets-Sheet 1 Filed June 10, 1959 IN VENTOR Mar/in Dobe/le lam/W143) M w fimi ATTORNEYS March 13, 1962 M. DOBELLE 3,024,785

FEMORAL HEAD PROSTHESIS Filed June 10, 1959 2 Sheets-$heet 2 I NV EN TOI Q Marl/n Dobel/e BY M, m @Mm ATTORNEYS United States Patent 3,024,785 FEMORAL HEAD PROSTHESIS Martin Dobelie, Pittsfieid, Mass. (1 Ocean Lane, Cocoa Beach, Fla.) Filed June 10, 1959, Ser. No. 819,340 6 Claims. (Cl. 128--92) The present invention relates to an improved femoral head prosthesis.

In my United States Patent No. 2,685,877, there is disclosed a femoral head prosthesis which generallycomprises a femoral head simulating the natural head of the femur. The head has a shank thereon by which the device is driven into a hole which has been reamed in the neck of the femur. There are a plurality of locking keys carried in the shank, and there is a screw in the shank for moving the locking keys into engagement with bone portion of the femur which surrounds the shank.

While this device is satisfactory in many instances, it is not completely satisfactory for all cases. There has been found that in some cases the shank of the device may even become loose in the head of the femur, and in other cases, the head of the femur by itself is not sufficiently strong to take the stress to which the device is subject. In addition, the only part of the device to which force can be applied to drive the shank into the head of the channel is the plastic head itself. There is therefore the possibility, which in some cases has been an actuality, that the plastic head is damaged during the installation of the device, considerable force having to be exerted on it to drive the device sufficiently far into the head of the femur. Finally, there has been experienced considerable difficulty in extracting the device. This is often desirable during an autopsy, and with my prior device even when the screw for operating the locking keys is retracted, the locking keys are not retracted, and there is considerable difficulty in removing the device because of the fact that the bone may have grown around the device sufficiently to hold it securely in the head of the femur.

It is accordingly the object of the present invention to provide an improved femoral head prosthesis which can be driven into position without exerting force on the plastic head of the device and which can be relatively easily be extracted from the femur.

Other and further objects of the invention will become apparent from the following specification and claims, taken together with the accompanying drawings in which:

FIG. 1 is a side elevation view of the upper part of the femur in which the head of the femur has been removed and replaced with a femoral head prosthesis according to the present invention, the dotted lines indicating the initial position of the parts in retracted position;

FIG. 2 is a view similar to FIG. 1, but showing the femoral head prosthesis as it is finally positioned, the dotted lines indicating the relative position of the parts;

FIG. 3 is an axial view, partly in section, of the femoral head prosthesis according to the present invention, the anchors being shown in the retracted position;

FIG. 4 is a view similar to that of FIG. 3 but with the anchors in the extended position;

FIG. 5 is an enlarged detailed sectional elevation view of the anchor actuating means;

FIG. 6 is a sectional view, partly in section, taken on line VIVI of FIG. 5;

FIG. 7 is a sectional view taken on line VII-VH of FIG. 5;

FIG. 8 is a sectional view taken on line VIII-VIII of FIG. 5;

FIG. 9 is a sectional view taken on line IX-IX of FIG. 5.

3,024,785 Patented Mar. 13, 1962 The femoral head prosthesis according to the present invention comprises a shank 10, having an upper shank portion 11 and a lower shank portion 12. The lower shank portion has a generally pointed lower end and a hollow threaded extension 12a on the upper end. The upper shank portion 11 has a threaded bore 13 therethrough into the lower end of which the hollow threaded extension 12a is threaded. The hollow threaded extension 12a on the lower shank portion 12 where it is threaded into the axial bore 13 and has two diametrically opposed slots 14 extending out through the sides thereof. The bottoms 14a of the slots 14 slope outwardly and away from the upper shank portion 11 and away from the lower shank portion 12. A plastic prosthesis head 16 is mounted on the free end of an angle member 15 on the upper shank portion 11.

Threaded into the thread-ed axial bore 13 in the upper shank portion is a threaded screw 17, which theaded screw has a slot 17a in the top thereof and a first transversely extending channel 18 therein in the end of the threaded screw 17 which is toward the lower shank portion. This channel extends only part of the way across threaded screw 17. A transversely extending opening 19 is provided in the threaded screw 17 which opens out of the said first channel 18 in the direction toward said lower shank portion.

An anchor support 20 is provided in the threaded axial bore 13. The anchor support has spherical head 21 thereon, the spherical head 21 being rotatably and slidably positioned in said first transversely extending channel 18. The anchor support 20 has a second transversely extending channel 23 in the end thereof opposite the spherical head 21, and has a second transversely extending opening 22 opening out of transversely extending channel 23.

There are provided two anchors 24 and 25 each of which has a spherical knob 26 on one end thereof and also has a curved leg 27 which is connected to the spherical knob 26 parallel to and offset from an axial plane through the knob 26. The knobs 26 are each rotatably positioned in the second transversely extending channel 23, with the legs 27 extending through the transversely extending opening 22. The curved legs of the anchors 24 and 25 are slidable in the slots 14.

A threaded cap 28 may be provided for closing the end of the threaded axial bore 13.

The free ends of the curved legs 27 of the anchors 24 and 25 are pointed and comprise a. sharp edge 30 which extends transversely into the end of the leg 27, the edge being at an angle to a perpendicular to the end of the leg and extending from the outside of the curvature of the leg to the inside of the curvature and toward the spherical knob on the end of the leg.

In operation, the shank 10, with the anchor 24 and 25 in the retracted position as shown in FIGS. 1 and 3, is driven into the end of the femur from which the femoral head has been removed. This is accomplished by applying the driving force to the threaded cap 28, thus avoiding the exertion of any force on the prosthesis head 16. When the desired position of the device has been reached, the threaded cap 28 is removed and the threaded screw 17 is threaded further into the threaded bore 13. This causes the anchors 24 and 25 to be moved downwardly until ends of the curved legs 27 contact the bottoms 14a of the slots 14. Upon further threading of the threaded screw 17 into the bore 13, the curved legs 27 are extended downwardly and outwardly through the slots 14 until they reach the position shown in FIGS. 2 and 4, at which piont the pointed ends are engaged in the bone portion of the femur. The threaded cap is then replaced, and positioning of the device is complete.

The reverse of the foregoing steps is carried out in order to retract the anchors 24 and 25 prior to the removal of the device. After the threaded cap 28 has been removed, the threaded screw 17 is backed out of the axial bore 13. The engagement of the spherical head 21 in the transversely extending channel 18 will cause the anchor support 20* to be carried along in this movement, and the engagement of the knobs 26 in the second transversely extending channel 23 will cause the curved legs of the anchors to be drawn inwardly and upwardly through the slots 14 into the threaded axial bore, because the curved legs 27 are attached to the spherical knobs in a position in which they are oifset from an axial plane through the knob and they may slide past each other in a direction transversely of the axis of the shank, as illustrated in FIGS. and 7. When the anchors have been thus removed the device may be withdrawn relatively easily, since the engagement of the anchors in the bone of the femur has been broken.

It will thus be seen that I have provided a femoral head prosthesis which not only can be driven into the femur without applying any force to the prothesis head itself, but also which can be relatively easily removed from the femur by reason of the fact that the anchors are positively actuated to withdraw them when the screw for extending them is retracted.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without depanting from the spirit and scope of the invention or sacrificing its material advantages, the form herein before described and illustrated being merely a preferred embodiment thereof.

I claim:

1. A femoral head prosthesis comprising a shank having an axial bore in one end thereof, said shank having diametrically opposed apertures therein opening out of the bottom of the said here, said apertures extending out through the sides of said shank, an angle member on the end of said shank which has said bore therein, said angle member extending at an angle outwardly therefrom and away from the other end of said shank, a prosthesis head on the end of said angle member, anchor support means in said bore movable axially along said bore, a plurality of anchors each having a leg thereon with a pointed end, said anchors being pivotally connected to said anchor support means with said legs extendable through and cooperable with the ends of said slots for extending downwardly and outwardly of said shank when said anchor support means moves along said bore, and a threaded cap in the end of said bore.

2. A femoral head prosthesis comprising a shank having a threaded axial bore in one end thereof, said shank having diametrically opposed slots opening out of the bottom of said bore, said slots extending out through the sides of said shank, an angle member on the end of said shank which has said bore therein, said angle member extending at an angle outwardly therefrom and away from the other end of said shank, a prosthetic head on the end of said angle member, a threaded screw threaded into the threaded bore, an anchor support in said threaded bore pivotally connected to said threaded screw, two anchors each comprising a curved leg having a pointed end thereon, said anchors being pivotally connected to said anchor support with said legs extendable through said slots for making such legs curve downwardly and outwardly of said shank, and a threaded cap in the end of said threaded bore.

3. In a femoral head prosthesis, the combination comprising a shank having a threaded axial bore in one end thereof, and said shank having diametrically opposed slots therein opening out of the bottom of said bore, said slots extending out through the sides of said shank, said slots sloping outwardly and away from the said one end of said shank, an angle member on said one end of said shank, a threaded screw threaded into the threaded bore and having a first transversely extending channel in the end thereof toward the bottom of said bore, said threaded screw having a transversely extending opening therein opening out of said first channel, an anchor support in said threaded bore having a spherical head thereon rotatable and slidable in said first transversely extending channel in said threaded screw, said anchor support having a second transversely extending channel in the end thereof opposite the said spherical head, said anchor support having a transversely extending opening therein opening out of said channel, two anchors each comprising a spherical knob and a curved leg having a pointed end thereon, said curved leg being connected to said spherical knob parallel to and offset from an axial plane through said knob, said knobs being rotatably positioned in said second channel with said legs extendable through the transversely extending opening from said second channel and slidable in said slots for making said legs curve downwardly and outwardly of said shank, and a threaded cap in the end of said threaded bore.

4. A femoral head prosthesis comprising a shank having an upper shank portion and a lower shank portion secured to each other, said upper shank portion having a threaded bore axially therethrough, said lower shank portion having diametrically opposed slots in the end thereof which is secured to the upper shank portion, said slots extending out through the sides of said shank portion, said slots sloping outwardly and away from the upper shank portion, an angle member on said upper shank portion extending at an angle outwardly therefrom and away from said lower shank portion, a prosthetic head on the end of said angle member, a threaded screw threaded into the threaded bore and having a first transversely extending channel in the end thereof toward the lower shank portion, said threaded screw having a transversely extending opening therein opening out of said first channel, an anchor support having a spherical head thereon rotatable and slidable in said first transversely extending channel in said threaded screw, said anchor support having a second transversely extending channel in the end thereof opposite the said spherical head, said anchor support having a transversely extending opening therein opening out of said channel, two anchors each comprising a spherical knob and a curved leg having a pointed end thereon, said curved leg being connected to said spherical knob parallel to and offset from an axial plane through said knob, said knobs being rotatably positioned in said second channel with said legs extendable through the transversely extending opening from said second channel and slidable in said slots for making said legs curve downwardly and outwardly of said upper shank portion, and a threaded cap in the end of said threaded bore in said upper shank portion.

5. A femoral head prosthesis as claimed in claim 4 in which the pointed end of each of said anchor legs comprises a sharp edge extending transversely of the end of the anchor leg, said edge being at an angle to a perpendicular to the end of the leg and extending from the outside of the curvature of the leg to the inside of the curvature and toward the knob on the end of the leg.

6. In a hollow shank for use as a femoral head prosthesis, the shank having a threaded bore and having slots therein opening out of the bore, an anchoring device comprising a threaded screw having a first transversely extending channel in one end thereof, said threaded screw having a transversely extending opening therein opening out of said first channel, an anchor support having a spherical head thereon slidable in said first transversely extending channel in said threaded screw, said anchor support having a second transversely extending channel in the end thereof opposite the said spherical head, said anchor support 'having a transversely extending opening therein opening out of said channel, two anchors each comprising a spherical knob and a curved leg having a pointed end slots and will curve downwardly and outwardly from the shank.

References Cited in the file of this patent UNITED STATES PATENTS Morrison Apr. 20, 1937 Pontius Nov. 24, 1953 Dobelle Aug. 10, 1954 Pontius Nov. 9, 1954

Images