Intramedullary hip pin
United States Patent 3918441
To receive the weight of the body from the pelvis and distribute it evenly to the shaft of a fractured femur while bracing the fractured femur, an intramedullary hip pin includes a head and a shank with the head including in its bottom surface a groove which receives a tongue from the top of the shank and is held thereto by a set screw. The head of the hip pin has a concave-downward saddle portion positionable beneath the neck of the femur to receive and distribute forces from the pelvis and has a blunt nose to impede its protrusion through the head of the femur. The shank extends downwardly within the shaft of the femur, being wedged therein by a shim plate.
US Patent References:
Articular replacement
Hudack - October 1955 - 2719522
Artificial femoral head
Chevalier - February 1957 - 2781758
Adjustable nail plate joint
Haboush - June 1966 - 3256877
INTRAMEDULLARY ROD AND CROSS-NAIL ASSEMBLY FOR TREATING FEMUR FRACTURES
Zickel - March 1969 - 3433220
/3623164.html
Bokros - November 1971 - 3623164
Articular replacement
Hudack - October 1955 - 2719522
Artificial femoral head
Chevalier - February 1957 - 2781758
Adjustable nail plate joint
Haboush - June 1966 - 3256877
INTRAMEDULLARY ROD AND CROSS-NAIL ASSEMBLY FOR TREATING FEMUR FRACTURES
Zickel - March 1969 - 3433220
/3623164.html
Bokros - November 1971 - 3623164
Application Number:
05/506694
Publication Date:
11/11/1975
Filing Date:
09/17/1974
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
606/67
International Classes:
A61B17/72; A61F2/36; A61F2/00; A61F2/30; A61B17/68; A61F5/04
Field of Search:
128/92,83 3/1
US Patent References:
Primary Examiner:
Michell, Robert W.
Assistant Examiner:
Yasko J.
Attorney, Agent or Firm:
Carney, Vincent L.
Claims:
What is claimed is
1. An intramedullary hip pin for supporting a fractured femur comprising:
2. An intramedullary hip pin according to claim 1 in which said head portion includes a blunt nose surface substantially orthogonal to said saddle, whereby said blunt nose surface resists penetrating the head of the femur.
3. An intramedullary hip pin according to claim 2 in which said shank portion has a longitudinal axis and exterior walls, said exterior walls being curved around the longitudinal axis with the lower end of the shank portion being of smaller diameter than the upper end of the shank portion so as to conform smoothly to a reamed out portion of the femur.
4. An intramedullary hip pin according to claim 3 in which said coupling means includes a groove in one of said head and shank portions and a tongue in the other of said head and shank portions.
5. An intramedullary hip pin according to claim 4 in which said coupling means further includes a set screw and a tapped hole adapted to connect said tongue to said other member.
6. An intramedullary hip pin according to claim 5 in which said coupling means further includes a brace extending downwardly from and being integrally formed with said head portion, said brace being adjacent to said shank portion.
7. An intramedullary hip pin according to claim 6 in which said pin comprises stainless steel.
8. An intramedullary hip pin for supporting a fractured femur comprising:
9. An intramedullary hip pin according to claim 8 in which said coupling means includes a groove in said bottom wall and a brace extending from said bottom wall adjacent to said groove.
10. An intramedullary hip pin according to claim 9 in which said coupling means includes:
1. An intramedullary hip pin for supporting a fractured femur comprising:
2. An intramedullary hip pin according to claim 1 in which said head portion includes a blunt nose surface substantially orthogonal to said saddle, whereby said blunt nose surface resists penetrating the head of the femur.
3. An intramedullary hip pin according to claim 2 in which said shank portion has a longitudinal axis and exterior walls, said exterior walls being curved around the longitudinal axis with the lower end of the shank portion being of smaller diameter than the upper end of the shank portion so as to conform smoothly to a reamed out portion of the femur.
4. An intramedullary hip pin according to claim 3 in which said coupling means includes a groove in one of said head and shank portions and a tongue in the other of said head and shank portions.
5. An intramedullary hip pin according to claim 4 in which said coupling means further includes a set screw and a tapped hole adapted to connect said tongue to said other member.
6. An intramedullary hip pin according to claim 5 in which said coupling means further includes a brace extending downwardly from and being integrally formed with said head portion, said brace being adjacent to said shank portion.
7. An intramedullary hip pin according to claim 6 in which said pin comprises stainless steel.
8. An intramedullary hip pin for supporting a fractured femur comprising:
9. An intramedullary hip pin according to claim 8 in which said coupling means includes a groove in said bottom wall and a brace extending from said bottom wall adjacent to said groove.
10. An intramedullary hip pin according to claim 9 in which said coupling means includes:
Description:
This invention relates to hip pins.
One class of hip pin includes a head portion that is anchored within the head and neck of the femur and a shank portion in the shaft of the femur to brace the femur across the fracture with the head and shank portions being fastened together. In a prior art type of this class of hip pin, the head of the hip pin is a narrow cone which extends through the neck of the femur on one end to a location adjacent to the head and extends from the other end of the femur, with the shank extending along the femur and being fastened thereto on the outside. The prior art type of hip pin has several disadvantages such as: (1) the head and neck of the femur tend to be forced down by the weight of the pelvis causing the head of the hip pin to be forced through the head of the femur into the hip joint; (2) the forces are poorly distributed from the pelvis onto the femur and require a relatively strong and large hip pin; and (3) weight cannot be placed on the fractured femur for an excessive period of time after the hip pin is implanted.
Accordingly, it is an object of the invention to provide a novel hip pin.
It is a further object of the invention to provide an intramedullary hip pin.
It is a still further object of the invention to provide a hip pin in which the forces from the pelvis are distributed along the center of the shaft of the femur through the shank of the hip pin.
It is a still further object of the invention to provide a hip pin which resists being forced through the head of the femur.
It is a still further object of the invention to provide a hip pin which includes a saddle that receives forces from the neck of the femur.
In accordance with the above and further objects of the invention, an intramedullary hip pin includes a head portion, a shank portion and a shim plate which fit together to hold the head and neck of the femur above the fractured portion to the shaft of the femur below the fractured portion.
The shank of the intramedullary hip pin is shaped to fit along the medulla of the femur shaft, being formed substantially like a cone which is bent and having its pointed end downward, the upper end including a tongue which mates with a groove in the head portion, being held thereto by a set screw. The shim plate is wedged between the wall of the femur shaft and the shank of the hip pin, mating with the hip pin with a tongue and groove connection to prevent rubbing of the shank of the hip pin against the wall of the femur.
The upper portion of the head has a saddle which corresponds substantially in shape to the neck of the femur so as to receive forces from the pelvis and distribute them relatively evenly along the shank of the hip pin downwardly through the medulla of the shaft of the femur. The head also includes a blunt nose facing the hip joint which resists movement of the head of the hip pin through the head of the femur and a downwardly extending brace that fits along the shank when the hip pin is assembled.
To insert the hip pin, holes are cut in the wall of the femur and portions of the head and shaft of the medulla of the femur are reamed to accommodate the hip pin. The shank of the hip pin is then inserted with its point entering first, the center of the curve of the hip pin being outwardly until the shank is inserted. The shank is then turned around so that the outer portion of its curvature faces the lateral wall of the femur.
After the shank of the hip pin has been inserted, the head is inserted with the brace of the head being inserted first, then the outer end and finally the nose, after which it is turned around so that the nose faces the hip joint and the bottom groove receives a tongue on the upper portion of the shank. A set screw then holds the shank to the head. In this position, the saddle of the head rests beneath the concave neck of the femur to receive forces from the pelvis and distribute them through the shank along the medulla of the femur shaft.
Because the weight from the pelvis is distributed from the neck of the femur to the saddle on the head of the hip pin, from the head of the hip pin to its shank and from the shank to the medulla of the femur shaft, the hip pin of this invention has several advantages, such as: (1) there is no strong tendency for the head of the femur to be shifted downwardly with respect to the pelvis; (2) the nose of the femur does not tend to move through the head of the femur; (3) a relatively small hip pin is sufficient to brace a fractured femur; and (4) the fractured femur can bear weight in a relatively short time after implanting of the hip pin.
The above noted and other features of the invention will be better understood from the following detailed description when considered with reference to the accompanying drawings in which:
FIG. 1 is an exploded perspective view of a hip pin in accordance with an embodiment of the invention;
FIG. 2 is an elevational side view of the hip pin of FIG. 1;
FIG. 3 is an elevational rear view of the hip pin of FIG. 1; and
FIG. 4 is a fragmentary perspective view of a portion of a pelvis and fractured femur held together by a hip pin in accordance with an embodiment of the invention.
In FIGS. 1-3, there is shown an intramedullary hip pin 10 having a shank portion 12, a head portion 14 and a shim plate 16, with the head portion 14 and shim plate 16 being shaped to mate with the shank 12 when assembled within a femur of a subject to hold the fractured portions of the femur together.
To provide an intramedullary anchor within the portion of the femur below the fractured section, the shank portion 12 includes a body section 18 having a general shape of a cone bent in a slight arc and flattened slightly on two opposite sides so as to fit within a reamed opening in the medulla of the femur with the outer side of the arc facing the lateral side of the femur and the flattened sides facing the anterior and posterior sides of the femur. The outer side of the body portion 18 has a longitudinally extending groove 20 along a portion of its length to mate with a tongue 44 extending from the shim plate 16 as will be explained hereinafter.
To mount the body portion 18 to the head portion 14, a tongue 22 is formed in the upper end of the body portion 18 to be received within a corresponding groove in the head 14.
While the body portion 18 in the preferred embodiment resembles a cone inverted and bent outwardly, its shape and size is adapted to the center of a femur and is of a size suitable for a particular femur. In practice, several different sizes of body portions 18 are available for selection to fit the particular size femur into which it is to be inserted. A typical hip pin is approximately six inches long from the bottom of the saddle to the bottom of the shank, with the saddle being 2 inches long and one-quarter of an inch deep. The shank has curved walls with an approximately elliptical cross section at the tip and is substantially cone shaped at the bottom where it forms a rounded point. The top has a major axis of approximately five-eighths of an inch and a minor axis of approximately one-half inch. The shank is curved lengthwise, having approximately a 6 inch radius of curvature and bends inwardly about three-eights of an inch.
To form a connecting anchor within the neck of the femur and the femur shaft of the upper side of the fracture, the head portion 14 includes a body 24 having on its top surface a saddle 26 and on its bottom surface a horizontal longitudinal groove 28 bounded by a downwardly extending brace 20, with the inner end of the body 24 ending in a blunt nose 32, which faces the pelvis when inserted, and the outer end having a flat supporting surface 34 facing the lateral side of the femur.
The groove 28 is of sufficient size to tightly receive the tongue 22 on the top of the shank 12 and the downwardly extending brace 20 has a surface 36 shaped to abut the inner side of the tongue 22 and body portion 12. The flat supporting surface 34 includes a tapped hole 40 adapted to receive a set screw 42 for fastening the tongue 22 within the groove 28, with the tapped hole 40 including a counterbore on its outer surface adapted to receive the head of the set screw 42.
To support the weight of the body, the saddle 26 has a downward curved surface which conforms substantially to the outer surface of the neck of the femur thus enabling it to bear the weight of the body and direct that weight downwardly through the medulla of the femur shank 12. The blunt nose 32 on the inner end on the head 14 is shaped to prevent it from extending through the head of the femur and a curved surface 38 extends from the lower end of the blunt nose 32 to the bottom end of the brace 30 to form an additional supporting surface against the head of the femur.
The shim plate 16 is a generally flat plate having a tongue 44 extending longitudinally from one flat surface of such a size as to fit within the groove 20 in the body portion 18 of the shank 12 to prevent sliding motion between the shank 12 and the shim plate 16. The flat shim plate 16 is inserted between the forward surface of the body portion 18 of the shank 12 and the bone wall to prevent movement of the body portion 18 within the center of the femur, with the flat plate 46 being shaped to fit against the femur wall.
In FIG. 4, there is shown an intramedullary hip pin 10 positioned within a femur 48 having a fracture 50 with the head 14 of the pin being positioned within the neck of the femur, the shim 16 being positioned along the lateral left side of the femur and the outwardly curved side of the shank 12 being inwardly of and mating with the shim plate 16.
To insert the intramedullary hip pin an opening 52 is prepared in the lateral side of the femur near a fracture 50 by drilling two holes which overlap along the length of the femur. The neck of the femur and the upper portion of the shaft of the femur are then reamed to accommodate respectively the head 14 and the shank 12 of the intramedullary hip pin 10.
After the femur has been reamed, the shank 12 is inserted into the hole 52, with its pointed end going in first and the remainder following, its convex outer side facing the opening and its concave side facing laterally as it enters. In this position, the shank 12 is moved downwardly into the femur and then turned so that its convex outer side faces laterally or in the opposite direction from which it entered.
After the shank 12 is implanted, the head 14 is inserted through the same hole 52 and moved above the fracture. The head is inserted with its downwardly extending brace 30 entering first and its supporting surface 32 entering next so that its blunt nose 32 points outwardly or laterally. It is then turned around within the opening so that the blunt nose 32 faces upwardly into the head of the femur. With both the shank 12 and the head 14 within the femur, the tongue 22 is forced within the groove 28 with the brace 30 abutting one surface of the tongue 22. The set screw 42 is then threaded into the tapped hole 40 until its head is within the counterbore to hold the tongue 22 within the groove 28.
After the head 14 and shank 12 are within the femur, the shim plate 16 is inserted with its tongue 44 aligned with the groove 20 in the body portion 18 of the shank 12. It is moved downwardly to separate the body portion 18 of the shank 12 from the wall of the femur and wedge it in place to prevent excessive friction against the bone wall. The groove 14 aids in holding the shank 18 in place.
With the intramedullary hip pin in place, the weight of the pelvis and body is upon the saddle 26 and imparted to the shank 12 which is along the medulla of the femur shaft. There is no tendency for the blunt nose 32 to be forced through the head of the femur since the weight is moved directly downward. Moreover, greater support is provided by the same size material because of the central location of the pin and the fractured femur can bear weight in a relatively short period of time after the hip pin is implanted.
Although a preferred embodiment has been described with some particularity, many modifications and variations in the invention are possible within the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.
One class of hip pin includes a head portion that is anchored within the head and neck of the femur and a shank portion in the shaft of the femur to brace the femur across the fracture with the head and shank portions being fastened together. In a prior art type of this class of hip pin, the head of the hip pin is a narrow cone which extends through the neck of the femur on one end to a location adjacent to the head and extends from the other end of the femur, with the shank extending along the femur and being fastened thereto on the outside. The prior art type of hip pin has several disadvantages such as: (1) the head and neck of the femur tend to be forced down by the weight of the pelvis causing the head of the hip pin to be forced through the head of the femur into the hip joint; (2) the forces are poorly distributed from the pelvis onto the femur and require a relatively strong and large hip pin; and (3) weight cannot be placed on the fractured femur for an excessive period of time after the hip pin is implanted.
Accordingly, it is an object of the invention to provide a novel hip pin.
It is a further object of the invention to provide an intramedullary hip pin.
It is a still further object of the invention to provide a hip pin in which the forces from the pelvis are distributed along the center of the shaft of the femur through the shank of the hip pin.
It is a still further object of the invention to provide a hip pin which resists being forced through the head of the femur.
It is a still further object of the invention to provide a hip pin which includes a saddle that receives forces from the neck of the femur.
In accordance with the above and further objects of the invention, an intramedullary hip pin includes a head portion, a shank portion and a shim plate which fit together to hold the head and neck of the femur above the fractured portion to the shaft of the femur below the fractured portion.
The shank of the intramedullary hip pin is shaped to fit along the medulla of the femur shaft, being formed substantially like a cone which is bent and having its pointed end downward, the upper end including a tongue which mates with a groove in the head portion, being held thereto by a set screw. The shim plate is wedged between the wall of the femur shaft and the shank of the hip pin, mating with the hip pin with a tongue and groove connection to prevent rubbing of the shank of the hip pin against the wall of the femur.
The upper portion of the head has a saddle which corresponds substantially in shape to the neck of the femur so as to receive forces from the pelvis and distribute them relatively evenly along the shank of the hip pin downwardly through the medulla of the shaft of the femur. The head also includes a blunt nose facing the hip joint which resists movement of the head of the hip pin through the head of the femur and a downwardly extending brace that fits along the shank when the hip pin is assembled.
To insert the hip pin, holes are cut in the wall of the femur and portions of the head and shaft of the medulla of the femur are reamed to accommodate the hip pin. The shank of the hip pin is then inserted with its point entering first, the center of the curve of the hip pin being outwardly until the shank is inserted. The shank is then turned around so that the outer portion of its curvature faces the lateral wall of the femur.
After the shank of the hip pin has been inserted, the head is inserted with the brace of the head being inserted first, then the outer end and finally the nose, after which it is turned around so that the nose faces the hip joint and the bottom groove receives a tongue on the upper portion of the shank. A set screw then holds the shank to the head. In this position, the saddle of the head rests beneath the concave neck of the femur to receive forces from the pelvis and distribute them through the shank along the medulla of the femur shaft.
Because the weight from the pelvis is distributed from the neck of the femur to the saddle on the head of the hip pin, from the head of the hip pin to its shank and from the shank to the medulla of the femur shaft, the hip pin of this invention has several advantages, such as: (1) there is no strong tendency for the head of the femur to be shifted downwardly with respect to the pelvis; (2) the nose of the femur does not tend to move through the head of the femur; (3) a relatively small hip pin is sufficient to brace a fractured femur; and (4) the fractured femur can bear weight in a relatively short time after implanting of the hip pin.
The above noted and other features of the invention will be better understood from the following detailed description when considered with reference to the accompanying drawings in which:
FIG. 1 is an exploded perspective view of a hip pin in accordance with an embodiment of the invention;
FIG. 2 is an elevational side view of the hip pin of FIG. 1;
FIG. 3 is an elevational rear view of the hip pin of FIG. 1; and
FIG. 4 is a fragmentary perspective view of a portion of a pelvis and fractured femur held together by a hip pin in accordance with an embodiment of the invention.
In FIGS. 1-3, there is shown an intramedullary hip pin 10 having a shank portion 12, a head portion 14 and a shim plate 16, with the head portion 14 and shim plate 16 being shaped to mate with the shank 12 when assembled within a femur of a subject to hold the fractured portions of the femur together.
To provide an intramedullary anchor within the portion of the femur below the fractured section, the shank portion 12 includes a body section 18 having a general shape of a cone bent in a slight arc and flattened slightly on two opposite sides so as to fit within a reamed opening in the medulla of the femur with the outer side of the arc facing the lateral side of the femur and the flattened sides facing the anterior and posterior sides of the femur. The outer side of the body portion 18 has a longitudinally extending groove 20 along a portion of its length to mate with a tongue 44 extending from the shim plate 16 as will be explained hereinafter.
To mount the body portion 18 to the head portion 14, a tongue 22 is formed in the upper end of the body portion 18 to be received within a corresponding groove in the head 14.
While the body portion 18 in the preferred embodiment resembles a cone inverted and bent outwardly, its shape and size is adapted to the center of a femur and is of a size suitable for a particular femur. In practice, several different sizes of body portions 18 are available for selection to fit the particular size femur into which it is to be inserted. A typical hip pin is approximately six inches long from the bottom of the saddle to the bottom of the shank, with the saddle being 2 inches long and one-quarter of an inch deep. The shank has curved walls with an approximately elliptical cross section at the tip and is substantially cone shaped at the bottom where it forms a rounded point. The top has a major axis of approximately five-eighths of an inch and a minor axis of approximately one-half inch. The shank is curved lengthwise, having approximately a 6 inch radius of curvature and bends inwardly about three-eights of an inch.
To form a connecting anchor within the neck of the femur and the femur shaft of the upper side of the fracture, the head portion 14 includes a body 24 having on its top surface a saddle 26 and on its bottom surface a horizontal longitudinal groove 28 bounded by a downwardly extending brace 20, with the inner end of the body 24 ending in a blunt nose 32, which faces the pelvis when inserted, and the outer end having a flat supporting surface 34 facing the lateral side of the femur.
The groove 28 is of sufficient size to tightly receive the tongue 22 on the top of the shank 12 and the downwardly extending brace 20 has a surface 36 shaped to abut the inner side of the tongue 22 and body portion 12. The flat supporting surface 34 includes a tapped hole 40 adapted to receive a set screw 42 for fastening the tongue 22 within the groove 28, with the tapped hole 40 including a counterbore on its outer surface adapted to receive the head of the set screw 42.
To support the weight of the body, the saddle 26 has a downward curved surface which conforms substantially to the outer surface of the neck of the femur thus enabling it to bear the weight of the body and direct that weight downwardly through the medulla of the femur shank 12. The blunt nose 32 on the inner end on the head 14 is shaped to prevent it from extending through the head of the femur and a curved surface 38 extends from the lower end of the blunt nose 32 to the bottom end of the brace 30 to form an additional supporting surface against the head of the femur.
The shim plate 16 is a generally flat plate having a tongue 44 extending longitudinally from one flat surface of such a size as to fit within the groove 20 in the body portion 18 of the shank 12 to prevent sliding motion between the shank 12 and the shim plate 16. The flat shim plate 16 is inserted between the forward surface of the body portion 18 of the shank 12 and the bone wall to prevent movement of the body portion 18 within the center of the femur, with the flat plate 46 being shaped to fit against the femur wall.
In FIG. 4, there is shown an intramedullary hip pin 10 positioned within a femur 48 having a fracture 50 with the head 14 of the pin being positioned within the neck of the femur, the shim 16 being positioned along the lateral left side of the femur and the outwardly curved side of the shank 12 being inwardly of and mating with the shim plate 16.
To insert the intramedullary hip pin an opening 52 is prepared in the lateral side of the femur near a fracture 50 by drilling two holes which overlap along the length of the femur. The neck of the femur and the upper portion of the shaft of the femur are then reamed to accommodate respectively the head 14 and the shank 12 of the intramedullary hip pin 10.
After the femur has been reamed, the shank 12 is inserted into the hole 52, with its pointed end going in first and the remainder following, its convex outer side facing the opening and its concave side facing laterally as it enters. In this position, the shank 12 is moved downwardly into the femur and then turned so that its convex outer side faces laterally or in the opposite direction from which it entered.
After the shank 12 is implanted, the head 14 is inserted through the same hole 52 and moved above the fracture. The head is inserted with its downwardly extending brace 30 entering first and its supporting surface 32 entering next so that its blunt nose 32 points outwardly or laterally. It is then turned around within the opening so that the blunt nose 32 faces upwardly into the head of the femur. With both the shank 12 and the head 14 within the femur, the tongue 22 is forced within the groove 28 with the brace 30 abutting one surface of the tongue 22. The set screw 42 is then threaded into the tapped hole 40 until its head is within the counterbore to hold the tongue 22 within the groove 28.
After the head 14 and shank 12 are within the femur, the shim plate 16 is inserted with its tongue 44 aligned with the groove 20 in the body portion 18 of the shank 12. It is moved downwardly to separate the body portion 18 of the shank 12 from the wall of the femur and wedge it in place to prevent excessive friction against the bone wall. The groove 14 aids in holding the shank 18 in place.
With the intramedullary hip pin in place, the weight of the pelvis and body is upon the saddle 26 and imparted to the shank 12 which is along the medulla of the femur shaft. There is no tendency for the blunt nose 32 to be forced through the head of the femur since the weight is moved directly downward. Moreover, greater support is provided by the same size material because of the central location of the pin and the fractured femur can bear weight in a relatively short period of time after the hip pin is implanted.
Although a preferred embodiment has been described with some particularity, many modifications and variations in the invention are possible within the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.