Femoral head prosthesis

Aug. 10, 1954 μ. dobelle 2,685,877

FEMORAL HEAD PROSTHESIS

Filed March 20, 1952

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INVENTOR

Martin Do belle,

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ATTORNEY

Patented Aug. 10, 1954

2,685,877

UNITED STATES PATENT OFFICE

2,685,877

FEMORAL HEAD PROSTHESIS

Martin Dobelle, Pittsfield, Mass.

Application March 20,1952, Serial No. 277,658

Claims.

The object of the invention is to provide means for obtaining a functional hip which would otherwise be non-functional when the head of the thigh bone was destroyed, impaired, or injured beyond repair, or where injury or disease has destroyed the hip joint and stiffened the latter so that motion is greatly limited, if not impossible; to provide a femoral head prosthesis which, when in position in the neck of the femur, will be retained in position without danger of loosening except under such conditions, as would fracture a strong or healthy bone; and to provide an appliance of the kind indicated which is of simple form and therefore, simple of application with ordinary skill on the part of the surgeon.

With this object in view, the invention consists of a construction and combination of parts of which a preferred embodiment is illustrated in the accompanying drawing wherein:

Figure 1 is a side elevational view of the upper part of a femur in which the head or proximal fragment has been removed and replaced with the improved femoral head, the dotted lines indicating the initial position of the parts in placement.

Figure 2 is a view similar to Figure 1 but shows the femoral head finally positioned, the dotted lines indicating the relative positions of the parts;

Figure 3 is an axial sectional view of the improved femoral prosthesis, the keys being shown in extended position;

Figure 4 is a sectional view similar to Figure 3 but with the locking keys in retracted position;

Figure 5 is an elevational view of the key actuator screw;

Figure 6 is an elevational view of the lock screw; and

Figure 7 is an elevational view of one of the locking keys, detached from the device.

In the use of the invention where the head of the femur is pathologically impaired beyond the point where normality can be restored, it is removed and in old injury or disease the socket of the attendant acetabulum is reamed out for the reception of the prosthetic head which is applied into the neck of the femur to replace the head removed therefrom.

The operation of applying the prosthetic head consists of boring the neck of the femur along its axis beyond a straight line passing through the great and lesser trochanters. The bore having been prepared, there is then applied the prosthetic head JO which is of plastic and stainless steel insert and which is formed with a shank ί i, which enters the bore, the lower end of the shank (Cl. 128—92) tapering as indicated at 12. The bore, of course, is made with a suitable reamer (or with a drill followed with a reamer), so that there will be a snug fit between the shank ί i and the wall of 5 the bore, the latter, of course, being in the medulla.

But the head must be securely anchored to the femur and to this end the shank i ί is moulded around and has incorporated with it a core (3 10 which is formed with a longitudinal bore ii, this bore being of a diameter corresponding to and registering with the bore 15 in the lower end of the shank 11.

The shank ! 1 is formed with lateral slots ί 6 15 and the core with lateral slots Π and adjacent these slots IT, the core carries the locking keys (8^a which are pivotally mounted, as indicated at 28. By reason of this arrangement, the key may be swung downwardly to nested positions within 20 the periphery of the core 13, or they may be swung outwardly to engage the medullary cortex, the former position being shown in Figure 4 and the latter in Figure 3..

But the keys must be actuated to extended posi25 tion and to this end there is provided a screw ! 9 formed with a pilot 20'» the latter engaging the heel ends of the keys when the screw is advanced, the screw threadingly engaging the bore of the core and the pilot moving axially there3Q along.

A prosthesis is applied, after the preparation of the receiving bore in the neck of the femur, by gently driving on the head with a cupped mallet until the shank is fully seated. When this has 35 been accomplished, the screw 19 is advanced and the pilot then engaging the shoulders 21 on the locking keys, will raise the latter, causing them to penetrate or engage the medullary cortex and thus lock the shank and with it the head in the 40 desired position on the femur.

The screw 19 is actuated with an ordinary screw driver of which the bit is inserted in the kerf of the head 22 of the screw.

When the locking keys have been fully ad45 vanced, the position of the actuating screw ί 9 is retained through the instrumentality of a lock screw 23 threadingly engaged with the upper end of the bore of the post.

It will be noted that the core is terminated just ₅0 short of the dome of the head, thus forming a shoulder on which the head of the set screw 23 may set, with the head of the screw below the femoral head. Thus there is no projecting metallic part. It will also be noted that the opera55 tion of setting the locking keys results in their

2,685,877 being raised from a pendant position from their axes to positions normal to the axis of the shank. Thus the slots which they cut in the femur are below them, and the upper hinges have firm; bearings tthroughout their· lengths within the neck of the femur, thereby providing a firm anchorage to keep the prosthetic head in place.

With the socket of the attendant acetabulum reamed out* with-a. standard cupped-· reamer or adequate otherwise, the acetabulum· is then* in condition to receive the new head with the result that a new hip joint is formed. Because of the inertness of the material used in the prosthesis, further bony growth, which would defeat its* purpose, is avoided, thus giving an otherw-isescrippledi individual a painless weight-bearing functioning hip.