Title:
CONNECTOR FOR FRACTURED BONES
United States Patent 3678925
Abstract:
A sleeve is to be inserted into a fractured bone bridging the fracture thereof. The leading end portion is then to be located in one bone fragment and the open trailing end portion is to communicate with the exterior of the other bone fragment. An expander screw is threaded into the sleeve and has a head which bears exclusively upon an annular shoulder provided on the sleeve. The front end of the expander screw serves, by its configuration or by cooperation with an expander element, for expanding the leading end of the sleeve so as to retain it in the bone fragment in which it is located. A cap screw is threadedly connected with and closes the trailing end portion of the sleeve, bearing upon the other bone fragment and thereby drawing the two fragments together via the intermediary of the sleeve.
US Patent References:
Fracture reducing device
Hardinge - August 1945 - 2381050
Bone pin locking device
Livingston - January 1955 - 2699774
Surgical device
Moreira - May 1941 - 2243717
Fracture clamping apparatus
Hanicke - June 1938 - 2121193
Bone pin
Livingston - December 1949 - 2490364
Fracture reducing device
Hardinge - August 1945 - 2381050
Bone pin locking device
Livingston - January 1955 - 2699774
Surgical device
Moreira - May 1941 - 2243717
Fracture clamping apparatus
Hanicke - June 1938 - 2121193
Bone pin
Livingston - December 1949 - 2490364
Inventors:
Fischer, Artur (Tumlingen, DT)
Muller, Jean-nicolas (Strassburg, FR)
Muller, Jean-nicolas (Strassburg, FR)
Application Number:
05/077267
Publication Date:
07/25/1972
Filing Date:
10/01/1970
View Patent Images:
Export Citation:
Primary Class:
International Classes:
A61B17/74; A61B17/72; A61B17/68; A61F5/04
Field of Search:
128/92BB,92R,92CA,92BC,92B,92D
Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Yasko J.
Claims:
We claim
1. A connector for fractured bones, comprising a sleeve adapted for inserting into a fractured bone bridging the fracture thereof, and having a leading portion adapted to be located in one bone fragment and an open trailing portion adapted to communicate with the exterior of the other bone fragment and provided with an endface and with internal threads inwardly of said endface; expander means for expanding said leading portion, and including an expander screw threaded through said sleeve and having a head portion located in said trailing portion axially bearing upon the same when said screw is rotated in a sense effecting expanding of said leading portion; and a cap screw having a stem threaded into said trailing portion of said sleeve and a cap screw head adapted to exteriorly engage and bear upon said other bone fragment, the threads of said screws being identical.
2. A connector as defined in claim 1, said sleeve having an inner annular shoulder in said trailing portion, and said head engaging and axially bearing upon said inner annular shoulder when said expander screw is rotated for expanding said leading portion.
3. A connector as defined in claim 1, wherein said sleeve, expander means and cap screw consist of rustfree steel and acid-resistant steel.
4. A connector as defined in claim 1, said sleeve having a radially inwardly extending flange at the leading open of said leading end portion.
5. A connector as defined in claim 1, said expander means including an expander element, and cooperating engaging means on said element and said expander screw for drawing the former into said sleeve in a sense expanding the same in response to rotation of said expander screw.
6. A connector as defined in claim 1, said expander means comprising an expander member, and an expander pin portion on said screw operative for expanding said expander member in response to advancement of said expander pin portion longitudinally of said sleeve due to rotation of said expander screw.
1. A connector for fractured bones, comprising a sleeve adapted for inserting into a fractured bone bridging the fracture thereof, and having a leading portion adapted to be located in one bone fragment and an open trailing portion adapted to communicate with the exterior of the other bone fragment and provided with an endface and with internal threads inwardly of said endface; expander means for expanding said leading portion, and including an expander screw threaded through said sleeve and having a head portion located in said trailing portion axially bearing upon the same when said screw is rotated in a sense effecting expanding of said leading portion; and a cap screw having a stem threaded into said trailing portion of said sleeve and a cap screw head adapted to exteriorly engage and bear upon said other bone fragment, the threads of said screws being identical.
2. A connector as defined in claim 1, said sleeve having an inner annular shoulder in said trailing portion, and said head engaging and axially bearing upon said inner annular shoulder when said expander screw is rotated for expanding said leading portion.
3. A connector as defined in claim 1, wherein said sleeve, expander means and cap screw consist of rustfree steel and acid-resistant steel.
4. A connector as defined in claim 1, said sleeve having a radially inwardly extending flange at the leading open of said leading end portion.
5. A connector as defined in claim 1, said expander means including an expander element, and cooperating engaging means on said element and said expander screw for drawing the former into said sleeve in a sense expanding the same in response to rotation of said expander screw.
6. A connector as defined in claim 1, said expander means comprising an expander member, and an expander pin portion on said screw operative for expanding said expander member in response to advancement of said expander pin portion longitudinally of said sleeve due to rotation of said expander screw.
Description:
BACKGROUND OF THE INVENTION
The present invention relates generally to a connector for fractured bones, and in particular to a connector for use in case of fractures of the neck of the femur, that is the upper thigh bone.
When a bone is fractured, that is when it is cracked and broken in two pieces-- a so-called "simple fracture" as opposed to a "compound fracture" where there is more than one break but in which case the general principle to be discussed here is also applicable-- it must be connected together in its normal position while it mends. In many instances, including where it is necessary to repair a fracture of the femur or upper thigh bone which hereafter will be used for purposes of explaining the background as well as the present invention, it is customary to drive a nail or pin under a requisite specific angle to the femur into the neck of the femur. This connects the broken-off neck with the remainder of the femur and locates the two bone fragments in their requisite relative position until such natural healing processes--i.e. the formation of callus --have permanently reunited the two bone fragments.
The problem with this prior-art approach is that while the two bone fragments can be located in proper position relative to one another, it is not possible to draw them together to such an extent as to eliminate the cap at the fracture line. This, however, is desirable because the smaller the cap is--meaning the closer the juxtaposed surfaces of the two bone fragments are--the more readily healing will occur and the formation of callus will take place. According to the prior art, however, it is not only not possible to reduce the gap but in fact the gap is somewhat increased as a result of driving the nail into the two bone fragments.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a connector for bone fragments, particularly but not exclusively for fractured femurs, which is not possessed of these disadvantages.
Still more specifically it is an object of the present invention to provide such a connector which will so connect the bone fragments as to speed the healing process which reconnects the fragments into a unitary bone.
A concomitant object of the invention is to provide such a connector which makes it possible to immediately put stress on the fractured bone without doing any damage.
In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention recites, briefly stated, in a connector for fractured bones which comprises a sleeve adapted for insertion into a fractured bone bridging the fracture thereof, and having a leading end portion adapted to be located in one bone fragment and an open trailing end portion adapted to communicate with the exterior of the other bone fragment. Expander means is provided for expanding the leading end portion and includes an expander screw threaded through the sleeve and having a head portion located within the trailing end portion engaging and bearing only upon the same when the screw is rotated in a sense effecting expanding of the leading end portion. A cap screw is threadedly connected with and closes the trailing end portion of the sleeve.
A connector constructed according to the present invention fulfills the requirements which have been outlined above. It can be readily installed in that a nail is first driven in conventional manner into the two bone fragments to be connected. In the case of a fractured femur the nail is driven centrally at the requisite angle into the neck of the femur. Now the sleeve of the connector according to the present invention is placed around the nail and driven into the bone, and subsequently the nail is withdrawn because it is no longer needed. The expander means is now utilized for expanding the leading end portion of the sleeve whereby the latter is anchored in the bone. According to the invention the head of the expanding screw bears only upon the sleeve itself so that the entire axial force necessary for effecting the expansion of the leading end portion of the sleeve acts only upon the latter, and not upon the bone. This prevents damage to the bone. Now the cap screw is threaded onto or into the trailing end of the sleeve and its cap screw head engages and bears upon the exterior of that bone fragment in which the end portion of the sleeve is embedded. Turning of the cap screw in a sense threading it more deeply onto the sleeve exerts pull upon the sleeve whereby the two bone fragments are drawn together and the gap at their fracture line is reduced or eliminated. Preferably the bone fragments should touch each other at the fracture line and in this manner the bone fracture will heal much more rapidly than heretofore possible. Moreover, the bone fragments now are in contact with one another rather than being spaced from one another as in the prior art, so that stress can immediately be placed on the fractured bone once it has been connected with the connector according to the present invention.
When the bone fragments are reunited, that is when the fracture is healed, the connector is no longer needed. At that time, therefore, the cap screw is unthreaded from the sleeve, and the expanding screw is similarly unthreaded and removed. The expander member, if a separate one has been employed which of course is located at the leading end of the sleeve, is dislodged in suitable manner, for instance by exerting a brief blow upon the screw before the latter is unthreaded, so that the expander member returns to its original position and permits the leading end of the sleeve to resiliently return to its original configuration, making it possible to subsequently remove the sleeve also.
According to one embodiment of the invention the rear or trailing portion of the sleeve has a stepped outer diameter, meaning that its outer diameter is less than that of the remainder of the sleeve. This portion of reduced outer diameter is provided with external screw threads which mesh with internal screw threads in the tubular stem of the cap screw whose outer diameter corresponds to the outer diameter of the remainder of the sleeve. Thus the hole which is formed in the bone as the sleeve is driven into it, will already have sufficient diameter to accommodate the cap screw when the latter is to be threaded onto the trailing end portion of the sleeve.
It is also possible in accordance with a further embodiment of the invention to provide the leading end portion of the sleeve at its open leading end with an inwardly directed flange which prevents the undesired emergence from this leading end of the expander member, and consequently prevents the expander member from becoming dislodged from the sleeve.
According to still another embodiment of the invention the leading end portion of the sleeve which is to be expanded may be surrounded with an elastic jacket. The reason for this is that it has been found that the formation of callus during healing takes place not only at the fracture but also between the segments of the leading end portion of the sleeve, it being understood that this leading end portion will normally be axially slotted to subdivide it into a plurality of segments or tongues in order to permit more ready expansion when needed. The formation of callus between the segments, however, would prevent proper elastic return of the segments to their original position when it is desired to dislodge the sleeve after healing. In fact, it might make such return impossible and would then force the sleeve to remain in the bone. The use of an elastic jacket, however, makes the formation of callus in and around the segments impossible so that they can return to their original undeflected position when the expander member is dislodged, and the sleeve can then be properly removed.
It is also possible to construct the front portion of the expander screw as a pin having a conical or otherwise configurated leading end which, when the screw is threaded deeper into the sleeve, serves to expand the expander member itself rather than drawing the latter into the sleeve for expanding the same. In such a construction it is possible not only to obtain good expanding action but also to make all components involved, including the outer diameter of the sleeve, very small so that the connector according to the present invention can be successfully used even for repairing bone fractures in children without unduly weakening the bones of children--which are not yet very large--with a large hole driven into them.
Also, it is possible to configurate the cap screw in such a manner that its stem does not exteriorly surround the trailing or rear end portion of the sleeve, but instead fits into the interior of the latter. In this case of course the stem of the cap screw must be exteriorly threaded to mesh with interior threads of the sleeve, and according to the invention the threads on the stem and the threads on the expander screw, or on the screw portion of the expander pin, will be identical whereby a simple and inexpensive manufacture of the various components is further facilitated.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagrammatic sectioned illustration showing one embodiment of the invention connecting the fragments of a fractured femur; and
FIG. 2 is a view similar to FIG. 1 but showing another embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Discussing now firstly the embodiment illustrated in FIG. 1 it will be seen that reference numerals 6 and 6' identify the two bone fragments into which a femur has become separated due to a fracture. In the drawing these two bone fragments have been properly aligned with reference to one another in the manner in which they were originally positioned when the bone was not yet fractured.
In this manner they are connected by means of the illustrated connector according to one embodiment of the invention. Reference numeral 1 identifies the connector in toto and it is to be understood that preferably the components of the connector are manufactured of rust-free steel, for instance of steel known under the designation V2A or that known under the designation V4A. The connector 1 comprises an expansion sleeve 2, whose front end portion is driven into the bone fragment 6, whereas its rear end portion is located in the bone fragment 6' through which the front end portion was originally driven. The rear end of the trailing or rear end portion of the sleeve 2 is open to the exterior of the bone fragment 6', as illustrated.
Located at the front end portion of the sleeve 2 is an expander portion 3, and the rear end portion which is stepped, that is which has a lesser outer diameter than the remainder of the sleeve 2, is identified with reference numeral 4. It is also exteriorly threaded and an interiorly threaded tubular stem of a cap screw 5 can be threaded onto it as shown in FIG. 1.
Located within the expander portion 3, which is for instance created by providing the leading end portion of the sleeve 2 with axially extending circumferentially spaced slots to subdivide it into individual tongues or sections, is an expander element 7 which can mesh with the expander screw 8 threaded into the interior of the sleeve 2. The head 9 of the expander screw 8 is of such dimensions that it engages the rear end face at the rear end of the sleeve 2 as shown in the drawing, or else it can actually be located within the sleeve and engage an inner annular shoulder provided for this purpose. In any case, as the screw 8 is threaded into the sleeve 2 in a sense drawing the expander element 7 rearwardly into the sleeve and thereby expanding the expander portion 3 due to the entry of the divergent expander element 7, the axial forces necessary to effect such expansion are transmitted exclusively into the sleeve 2 by virtue of the fact that the head 9 of the screw 8 bears only upon the sleeve 2.
Preferably, although not necessarily, the sleeve 2 is exteriorly provided with projections 10 or other similar means for preventing its rotation with reference to the bone fragments 6, 6'.
Once the expander portion 3 has been expanded, the cap screw is threaded onto the trailing end portion 4 of the sleeve 2. In order to be able to transmit the necessary torque required for drawing the bone fragments 6, 6' together until they abut at the fracture line, the cap screw 5 is provided with a cap screw head or flange 11 which bears upon the exterior of the bone fragment 6'. To increase the surface with which the flange 11 can bear upon the bone fragment 6' it is possible to provide a washer 12 as illustrated.
To increase the elasticity and ability for radially outward deflection of the expander portion 3, an annular groove 13 is provided on the sleeve 2 exteriorly encircling the same at the junction with the expander portion 3. An elastically deflectable jacket 14 is pushed onto and surrounds the expander portion 3 and is expanded together with the latter, the purpose being to prevent the growth of callus between the sections of the expander portion 3. The jacket 14 is removed together with the sleeve 2 when the fracture is healed.
In the embodiment of FIG. 2 like elements are identified with like reference numerals. Here, however, the expansion of the expander portion 3 is effected by constructing the expander member 7a as an actual portion of the screw serving for expanding purposes, or, putting it conversely, to construct the screw in a pin-shaped configuration having a tapering leading end 17 as illustrated and an exteriorly threaded head 15 which meshes with the interior threads in the sleeve 2. In this case the expander portion 3, having a bore corresponding to the tapering configuration of the leading end portion 17, is expanded by threading the screw head 15 deeper into the sleeve 2 in a sense advancing the pin 7a forwardly, that is towards the left in FIG. 2.
Once anchoring is accomplished, the bone fragments 6 and 6' are drawn together into abutment by threading the cap screw 5a into the interior threads of the sleeve 2 as illustrated. Of course, in this case the stem of the cap screw is exteriorly threaded as will be appreciated. Reference numeral 16 identifies a slot in the head 15 of the pin 7a for facilitating turning of the latter. As the head of the cap screw 5a bears upon the exterior of the bone fragment 6', the sleeve 2 is drawn in the direction towards this head and thereby the bone fragment 6 is drawn into tight abutment with the bone fragment 6'. FIG. 2 also shows that the washer 12a can be configurated in such a manner--compare the single or plural projections 12b--that it will serve not only to increase the abutment surface between the head of the cap screw 5a and the bone fragment 6', but also will serve as a retaining element for preventing undesired loosening of the cap screw 5a for which purpose it is provided--in addition to the projections 12b--with a tongue 12c engaging and preventing turning of the head of the cap screw 5a.
In addition to the advantages which already have been outlined as afforded by the present invention, a further advantage is the fact that the connector according to the present invention has an identical diameter over its entire exterior--this being true in FIG. 1 also when the cap screw is connected with the sleeve--and thereby can be produced in a simple and relatively inexpensive manner, and also can be very readily and simply inserted into the bone fragments.
While it has been pointed out that the constituent components of the connector are advantageously made of rustfree or stainless steel, such as V2A or V4A, it will be appreciated that other materials may also be suitable and are intended to be included in the scope and concept of this disclosure. Sleeve 14 may be of synthetic plastic, elastically deflectable steel, or the like.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in a connecting element for bone fragments, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.
The present invention relates generally to a connector for fractured bones, and in particular to a connector for use in case of fractures of the neck of the femur, that is the upper thigh bone.
When a bone is fractured, that is when it is cracked and broken in two pieces-- a so-called "simple fracture" as opposed to a "compound fracture" where there is more than one break but in which case the general principle to be discussed here is also applicable-- it must be connected together in its normal position while it mends. In many instances, including where it is necessary to repair a fracture of the femur or upper thigh bone which hereafter will be used for purposes of explaining the background as well as the present invention, it is customary to drive a nail or pin under a requisite specific angle to the femur into the neck of the femur. This connects the broken-off neck with the remainder of the femur and locates the two bone fragments in their requisite relative position until such natural healing processes--i.e. the formation of callus --have permanently reunited the two bone fragments.
The problem with this prior-art approach is that while the two bone fragments can be located in proper position relative to one another, it is not possible to draw them together to such an extent as to eliminate the cap at the fracture line. This, however, is desirable because the smaller the cap is--meaning the closer the juxtaposed surfaces of the two bone fragments are--the more readily healing will occur and the formation of callus will take place. According to the prior art, however, it is not only not possible to reduce the gap but in fact the gap is somewhat increased as a result of driving the nail into the two bone fragments.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a connector for bone fragments, particularly but not exclusively for fractured femurs, which is not possessed of these disadvantages.
Still more specifically it is an object of the present invention to provide such a connector which will so connect the bone fragments as to speed the healing process which reconnects the fragments into a unitary bone.
A concomitant object of the invention is to provide such a connector which makes it possible to immediately put stress on the fractured bone without doing any damage.
In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention recites, briefly stated, in a connector for fractured bones which comprises a sleeve adapted for insertion into a fractured bone bridging the fracture thereof, and having a leading end portion adapted to be located in one bone fragment and an open trailing end portion adapted to communicate with the exterior of the other bone fragment. Expander means is provided for expanding the leading end portion and includes an expander screw threaded through the sleeve and having a head portion located within the trailing end portion engaging and bearing only upon the same when the screw is rotated in a sense effecting expanding of the leading end portion. A cap screw is threadedly connected with and closes the trailing end portion of the sleeve.
A connector constructed according to the present invention fulfills the requirements which have been outlined above. It can be readily installed in that a nail is first driven in conventional manner into the two bone fragments to be connected. In the case of a fractured femur the nail is driven centrally at the requisite angle into the neck of the femur. Now the sleeve of the connector according to the present invention is placed around the nail and driven into the bone, and subsequently the nail is withdrawn because it is no longer needed. The expander means is now utilized for expanding the leading end portion of the sleeve whereby the latter is anchored in the bone. According to the invention the head of the expanding screw bears only upon the sleeve itself so that the entire axial force necessary for effecting the expansion of the leading end portion of the sleeve acts only upon the latter, and not upon the bone. This prevents damage to the bone. Now the cap screw is threaded onto or into the trailing end of the sleeve and its cap screw head engages and bears upon the exterior of that bone fragment in which the end portion of the sleeve is embedded. Turning of the cap screw in a sense threading it more deeply onto the sleeve exerts pull upon the sleeve whereby the two bone fragments are drawn together and the gap at their fracture line is reduced or eliminated. Preferably the bone fragments should touch each other at the fracture line and in this manner the bone fracture will heal much more rapidly than heretofore possible. Moreover, the bone fragments now are in contact with one another rather than being spaced from one another as in the prior art, so that stress can immediately be placed on the fractured bone once it has been connected with the connector according to the present invention.
When the bone fragments are reunited, that is when the fracture is healed, the connector is no longer needed. At that time, therefore, the cap screw is unthreaded from the sleeve, and the expanding screw is similarly unthreaded and removed. The expander member, if a separate one has been employed which of course is located at the leading end of the sleeve, is dislodged in suitable manner, for instance by exerting a brief blow upon the screw before the latter is unthreaded, so that the expander member returns to its original position and permits the leading end of the sleeve to resiliently return to its original configuration, making it possible to subsequently remove the sleeve also.
According to one embodiment of the invention the rear or trailing portion of the sleeve has a stepped outer diameter, meaning that its outer diameter is less than that of the remainder of the sleeve. This portion of reduced outer diameter is provided with external screw threads which mesh with internal screw threads in the tubular stem of the cap screw whose outer diameter corresponds to the outer diameter of the remainder of the sleeve. Thus the hole which is formed in the bone as the sleeve is driven into it, will already have sufficient diameter to accommodate the cap screw when the latter is to be threaded onto the trailing end portion of the sleeve.
It is also possible in accordance with a further embodiment of the invention to provide the leading end portion of the sleeve at its open leading end with an inwardly directed flange which prevents the undesired emergence from this leading end of the expander member, and consequently prevents the expander member from becoming dislodged from the sleeve.
According to still another embodiment of the invention the leading end portion of the sleeve which is to be expanded may be surrounded with an elastic jacket. The reason for this is that it has been found that the formation of callus during healing takes place not only at the fracture but also between the segments of the leading end portion of the sleeve, it being understood that this leading end portion will normally be axially slotted to subdivide it into a plurality of segments or tongues in order to permit more ready expansion when needed. The formation of callus between the segments, however, would prevent proper elastic return of the segments to their original position when it is desired to dislodge the sleeve after healing. In fact, it might make such return impossible and would then force the sleeve to remain in the bone. The use of an elastic jacket, however, makes the formation of callus in and around the segments impossible so that they can return to their original undeflected position when the expander member is dislodged, and the sleeve can then be properly removed.
It is also possible to construct the front portion of the expander screw as a pin having a conical or otherwise configurated leading end which, when the screw is threaded deeper into the sleeve, serves to expand the expander member itself rather than drawing the latter into the sleeve for expanding the same. In such a construction it is possible not only to obtain good expanding action but also to make all components involved, including the outer diameter of the sleeve, very small so that the connector according to the present invention can be successfully used even for repairing bone fractures in children without unduly weakening the bones of children--which are not yet very large--with a large hole driven into them.
Also, it is possible to configurate the cap screw in such a manner that its stem does not exteriorly surround the trailing or rear end portion of the sleeve, but instead fits into the interior of the latter. In this case of course the stem of the cap screw must be exteriorly threaded to mesh with interior threads of the sleeve, and according to the invention the threads on the stem and the threads on the expander screw, or on the screw portion of the expander pin, will be identical whereby a simple and inexpensive manufacture of the various components is further facilitated.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagrammatic sectioned illustration showing one embodiment of the invention connecting the fragments of a fractured femur; and
FIG. 2 is a view similar to FIG. 1 but showing another embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Discussing now firstly the embodiment illustrated in FIG. 1 it will be seen that reference numerals 6 and 6' identify the two bone fragments into which a femur has become separated due to a fracture. In the drawing these two bone fragments have been properly aligned with reference to one another in the manner in which they were originally positioned when the bone was not yet fractured.
In this manner they are connected by means of the illustrated connector according to one embodiment of the invention. Reference numeral 1 identifies the connector in toto and it is to be understood that preferably the components of the connector are manufactured of rust-free steel, for instance of steel known under the designation V2A or that known under the designation V4A. The connector 1 comprises an expansion sleeve 2, whose front end portion is driven into the bone fragment 6, whereas its rear end portion is located in the bone fragment 6' through which the front end portion was originally driven. The rear end of the trailing or rear end portion of the sleeve 2 is open to the exterior of the bone fragment 6', as illustrated.
Located at the front end portion of the sleeve 2 is an expander portion 3, and the rear end portion which is stepped, that is which has a lesser outer diameter than the remainder of the sleeve 2, is identified with reference numeral 4. It is also exteriorly threaded and an interiorly threaded tubular stem of a cap screw 5 can be threaded onto it as shown in FIG. 1.
Located within the expander portion 3, which is for instance created by providing the leading end portion of the sleeve 2 with axially extending circumferentially spaced slots to subdivide it into individual tongues or sections, is an expander element 7 which can mesh with the expander screw 8 threaded into the interior of the sleeve 2. The head 9 of the expander screw 8 is of such dimensions that it engages the rear end face at the rear end of the sleeve 2 as shown in the drawing, or else it can actually be located within the sleeve and engage an inner annular shoulder provided for this purpose. In any case, as the screw 8 is threaded into the sleeve 2 in a sense drawing the expander element 7 rearwardly into the sleeve and thereby expanding the expander portion 3 due to the entry of the divergent expander element 7, the axial forces necessary to effect such expansion are transmitted exclusively into the sleeve 2 by virtue of the fact that the head 9 of the screw 8 bears only upon the sleeve 2.
Preferably, although not necessarily, the sleeve 2 is exteriorly provided with projections 10 or other similar means for preventing its rotation with reference to the bone fragments 6, 6'.
Once the expander portion 3 has been expanded, the cap screw is threaded onto the trailing end portion 4 of the sleeve 2. In order to be able to transmit the necessary torque required for drawing the bone fragments 6, 6' together until they abut at the fracture line, the cap screw 5 is provided with a cap screw head or flange 11 which bears upon the exterior of the bone fragment 6'. To increase the surface with which the flange 11 can bear upon the bone fragment 6' it is possible to provide a washer 12 as illustrated.
To increase the elasticity and ability for radially outward deflection of the expander portion 3, an annular groove 13 is provided on the sleeve 2 exteriorly encircling the same at the junction with the expander portion 3. An elastically deflectable jacket 14 is pushed onto and surrounds the expander portion 3 and is expanded together with the latter, the purpose being to prevent the growth of callus between the sections of the expander portion 3. The jacket 14 is removed together with the sleeve 2 when the fracture is healed.
In the embodiment of FIG. 2 like elements are identified with like reference numerals. Here, however, the expansion of the expander portion 3 is effected by constructing the expander member 7a as an actual portion of the screw serving for expanding purposes, or, putting it conversely, to construct the screw in a pin-shaped configuration having a tapering leading end 17 as illustrated and an exteriorly threaded head 15 which meshes with the interior threads in the sleeve 2. In this case the expander portion 3, having a bore corresponding to the tapering configuration of the leading end portion 17, is expanded by threading the screw head 15 deeper into the sleeve 2 in a sense advancing the pin 7a forwardly, that is towards the left in FIG. 2.
Once anchoring is accomplished, the bone fragments 6 and 6' are drawn together into abutment by threading the cap screw 5a into the interior threads of the sleeve 2 as illustrated. Of course, in this case the stem of the cap screw is exteriorly threaded as will be appreciated. Reference numeral 16 identifies a slot in the head 15 of the pin 7a for facilitating turning of the latter. As the head of the cap screw 5a bears upon the exterior of the bone fragment 6', the sleeve 2 is drawn in the direction towards this head and thereby the bone fragment 6 is drawn into tight abutment with the bone fragment 6'. FIG. 2 also shows that the washer 12a can be configurated in such a manner--compare the single or plural projections 12b--that it will serve not only to increase the abutment surface between the head of the cap screw 5a and the bone fragment 6', but also will serve as a retaining element for preventing undesired loosening of the cap screw 5a for which purpose it is provided--in addition to the projections 12b--with a tongue 12c engaging and preventing turning of the head of the cap screw 5a.
In addition to the advantages which already have been outlined as afforded by the present invention, a further advantage is the fact that the connector according to the present invention has an identical diameter over its entire exterior--this being true in FIG. 1 also when the cap screw is connected with the sleeve--and thereby can be produced in a simple and relatively inexpensive manner, and also can be very readily and simply inserted into the bone fragments.
While it has been pointed out that the constituent components of the connector are advantageously made of rustfree or stainless steel, such as V2A or V4A, it will be appreciated that other materials may also be suitable and are intended to be included in the scope and concept of this disclosure. Sleeve 14 may be of synthetic plastic, elastically deflectable steel, or the like.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in a connecting element for bone fragments, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.