Endoprosthesis for the hipjoint
United States Patent 3896505
An endoprosthesis for the hip joint includes a head portion, or artificial femoral head, and a substantially elbow-shaped member of polyethylene resiliently supporting said head portion. The elbow-shaped member includes a relatively short upper portion and a relatively long lower portion and defines at the junction of these two portions on one side a concave bent and on the other side a convex bent. Each of both portions is provided with an internal channel. One of these channels is substantially coaxial with the upper portion of said elbow-shaped member and has an entrance or opening situated at the convex bent of said elbow-shaped member. The other of these channels is substantially coaxial with said lower portion of said elbow-shaped member and has an entrance or opening situated at the upper portion of said elbow-shaped member. The aforementioned channels intersect at an obtuse angle and each of the aforementioned channels receives one of a pair of pins or studs. The upper head portion or artificial femoral head defines a slanting channel into which said upper portion of said elbow-shaped member of polyethylene projects.
US Patent References:
Prosthesis for femoral heads
Timmermans - May 1954 - 2679245
Articular replacement
Hudack - October 1955 - 2719522
Artificial femoral head
Chevalier - February 1957 - 2781758
Damped prosthesis forming a substitute for the coxo-femoral articulation
Ficat et al. - November 1962 - 3064645
HIP-JOINT PROSTHESIS
Christiansen - September 1969 - 3466670
Prosthesis for femoral heads
Timmermans - May 1954 - 2679245
Articular replacement
Hudack - October 1955 - 2719522
Artificial femoral head
Chevalier - February 1957 - 2781758
Damped prosthesis forming a substitute for the coxo-femoral articulation
Ficat et al. - November 1962 - 3064645
HIP-JOINT PROSTHESIS
Christiansen - September 1969 - 3466670
Application Number:
05/390138
Publication Date:
07/29/1975
Filing Date:
08/20/1973
View Patent Images:
Export Citation:
Primary Class:
International Classes:
A61F2/36; A61L27/04; A61L27/18; A61L27/56; A61B17/72; A61B17/74; A61B17/78; A61F2/00; A61F2/30; A61L27/00; A61B17/68; A61F1/24
Field of Search:
3/1,1.913,1.912,1.91 128/92CA,92C,92R
Primary Examiner:
Frinks, Ronald L.
Attorney, Agent or Firm:
Salzer, Erwin
Parent Case Data:
This application is a continuation of application Ser. No. 124,431, filed Aug. 23, 1971, now abandoned.
Claims:
I claim as my invention
1. A femoral head prosthesis including
2. A femoral head prosthesis as specified in claim 1 wherein said head portion (a) is of a plastic material and supports a metallic substantially spherical shell (b), wherein a body (o) of a resilient substance is arranged at the end of said first channel of said head portion adjacent said spherical shell, and wherein said upper portion (h) of said elbow-shaped member (g,h) is loosely inserted into said first channel of said head portion and abuts with one end surface thereof against said body of said resilient substance.
1. A femoral head prosthesis including
2. A femoral head prosthesis as specified in claim 1 wherein said head portion (a) is of a plastic material and supports a metallic substantially spherical shell (b), wherein a body (o) of a resilient substance is arranged at the end of said first channel of said head portion adjacent said spherical shell, and wherein said upper portion (h) of said elbow-shaped member (g,h) is loosely inserted into said first channel of said head portion and abuts with one end surface thereof against said body of said resilient substance.
Description:
BACKGROUND OF THE INVENTION
This invention relates to a femoral endoprosthesis. This endoprosthesis calls for but a relatively simple resection of the natural femoral head which it replaces, allows a ready adaptation of it by the surgeon to the particular anatomy of his patient, and has a great dimensional stability, as a result of which it maintains the correct positional relationship to the femur and is in particular capable of withstanding the torsional forces tending to rotate any endoprosthesis relative to the femur.
SUMMARY OF THE INVENTION
An endoprosthesis embodying this invention includes a head portion or artificial femoral head which is at least in part of spherical shape and defines a first internal slanting channel. It further includes an elbow-shaped member intended to perform the function of an intra-medullary nail. This substantially elbow-shaped member is of polyethylene and includes a relatively short upper portion projecting into said first slanting channel of said head portion and a relatively long lower portion enclosing an obtuse angle with said upper portion. Both portions of said elbow-shaped member define at the junction thereof at one side a convex bent and on the other side a concave bent. The aforementioned upper portion defines a second internal channel coaxial with said first internal channel of said head portion and having an entrance or opening situated at the region of said convex bent. The aforementioned lower portion of said substantially elbow-shaped member defines a third internal channel extending in a direction longitudinally thereof, intersecting with said second channel and having an entrance or opening situated at said upper portion of said elbow-shaped member. The prosthesis further includes a first pin and a second pin. The first pin has an end situated outside said elbow-shaped member and projecting through said entrance or opening at said region of said convex bent of said elbow-shaped member into said upper portion thereof. The aforementioned second pin is arranged inside said third channel and inside said lower portion of said elbow-shaped member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a femoral endoprosthesis embodying the present invention;
FIG. 2 shows in side elevation a detail of the structure of FIG. 1; and
FIG. 3 is substantially a longitudinal section of the structure of FIG. 1, showing some parts thereof in elevation rather than in section.
DESCRIPTION OF PREFERRED EMBODIMENT
In the drawings reference character a has been applied to generally indicate an artificial femoral head of a hip joint prosthesis. The member a is at least in part spherical and defines a first internal slanting channel, i.e., an internal channel slanting from the lower left to the upper right. The artificial femoral head a is supported by an intra-medullary nail g,h of polyethylene which is substantially elbow-shaped and includes the relatively short upper portion h and the relatively long lower portion g. Portion h projects into the aforementioned slanting channel in artificial femoral head a. Portions h and g of member g,h enclose an obtuse angle. The portions g,h define at the region of their junction at one side -- the right side in FIGS. 1 and 3 -- a concave bent and at the other side -- the left side in FIGS. 1 and 3 -- a concave bent and at the other side-- the left side in FIGS. 1 and 3 -- a convex bent. The upper portion h of the intra-medullary nail g,h defines a second internal channel to which reference character v has been applied. Channel v is arranged in coaxial relation to the aforementioned internal slanting channel in head a. Channel v has an entrance or opening situated at the region of the convex bent between portions g and h of member g,h. The lower portion g of member g,h defines a third internal channel to which reference character l has been applied. Channel l extends in a direction longitudinally of the portion g of intra-medullary nail g,h, intersects said second channel v and has an entrance situated at the aforementioned upper portion h of elbow-shaped member g,h. Reference character d has been applied to indicate a first pin having a pointed end situated outside member g,h and projecting through the region of the convex bent of member g,h into the upper portion h thereof. Reference character m has been applied to indicate a second pin arranged inside of channel l and inside the lower portion g of elbow-shaped member g,h. The head portion a is preferably of a plastic material and supports a metallic substantially spherical shell b shown in detail in FIG. 2. The body o of a resilient substance, e.g., rubber, is arranged at the end of said first channel of said head portion a adjacent said spherical shell b and is covered by the latter. The upper portion h of elbow-shaped member g,h is loosely inserted into said first channel in head portion a and abuts with one end surface thereof against said body o of said resilient substance. Reference character t has been applied to indicate the edge of metallic cap or shell b. The base c of head portion a has a rim u to which shell b is affixed. Reference character p has been applied to indicate cavities formed between shell b and body o of resilient material, which may be a rubberlike substance.
FIG. 2 shows cap or shell b as being a deep drawn metal part being spherical at the top or apex and including a cylindrical lower portion q bounded by dotted lines r and s. Shell b may be affixed to base c by pressing the cylindrical portion q thereof into rim u of head portion a.
The elbow-shaped member g,h of a thermoplastic material such as polyethylene is formed by machining a straight shaft, e.g., by means of a lathe, providing it with the above described channels and then imparting to it the desired elbow-shape upon heating thereof to about 80°-100° C. Channel v is drilled to its full diameter to receive stud d only following bending of part g,h to its elbow-shape.
While performing the hip joint operation the surgeon may re-heat and re-shape part g,h in accordance with particular requirements. The pin or stud d is conical at its end remote from head a as indicated at f. Portion f of stud d is provided with a plastic cover e. The intra-medullary nail g,h may be inserted in warm and softened condition upon resection of the natural femoral head. Rod m is inserted into part g,h after the latter has been inserted by the surgeon into place. Thereupon the surgeon drills a hole into the trachanter side of the femur to insert stem or pin d with its end e into the bone.
It will be apparent from the above that the present hip joint prosthesis can be implanted without massive resection and allows to propagate hip joint forces throughout the femur much as in the natural state. The dimensional stability of the present endoprosthesis is largely due to the presence of the two intersecting passages v,l and that of the two pins m and d. Part o of rubber or spongy material forms a particularly effective shock-absorber.
This invention relates to a femoral endoprosthesis. This endoprosthesis calls for but a relatively simple resection of the natural femoral head which it replaces, allows a ready adaptation of it by the surgeon to the particular anatomy of his patient, and has a great dimensional stability, as a result of which it maintains the correct positional relationship to the femur and is in particular capable of withstanding the torsional forces tending to rotate any endoprosthesis relative to the femur.
SUMMARY OF THE INVENTION
An endoprosthesis embodying this invention includes a head portion or artificial femoral head which is at least in part of spherical shape and defines a first internal slanting channel. It further includes an elbow-shaped member intended to perform the function of an intra-medullary nail. This substantially elbow-shaped member is of polyethylene and includes a relatively short upper portion projecting into said first slanting channel of said head portion and a relatively long lower portion enclosing an obtuse angle with said upper portion. Both portions of said elbow-shaped member define at the junction thereof at one side a convex bent and on the other side a concave bent. The aforementioned upper portion defines a second internal channel coaxial with said first internal channel of said head portion and having an entrance or opening situated at the region of said convex bent. The aforementioned lower portion of said substantially elbow-shaped member defines a third internal channel extending in a direction longitudinally thereof, intersecting with said second channel and having an entrance or opening situated at said upper portion of said elbow-shaped member. The prosthesis further includes a first pin and a second pin. The first pin has an end situated outside said elbow-shaped member and projecting through said entrance or opening at said region of said convex bent of said elbow-shaped member into said upper portion thereof. The aforementioned second pin is arranged inside said third channel and inside said lower portion of said elbow-shaped member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a femoral endoprosthesis embodying the present invention;
FIG. 2 shows in side elevation a detail of the structure of FIG. 1; and
FIG. 3 is substantially a longitudinal section of the structure of FIG. 1, showing some parts thereof in elevation rather than in section.
DESCRIPTION OF PREFERRED EMBODIMENT
In the drawings reference character a has been applied to generally indicate an artificial femoral head of a hip joint prosthesis. The member a is at least in part spherical and defines a first internal slanting channel, i.e., an internal channel slanting from the lower left to the upper right. The artificial femoral head a is supported by an intra-medullary nail g,h of polyethylene which is substantially elbow-shaped and includes the relatively short upper portion h and the relatively long lower portion g. Portion h projects into the aforementioned slanting channel in artificial femoral head a. Portions h and g of member g,h enclose an obtuse angle. The portions g,h define at the region of their junction at one side -- the right side in FIGS. 1 and 3 -- a concave bent and at the other side -- the left side in FIGS. 1 and 3 -- a concave bent and at the other side-- the left side in FIGS. 1 and 3 -- a convex bent. The upper portion h of the intra-medullary nail g,h defines a second internal channel to which reference character v has been applied. Channel v is arranged in coaxial relation to the aforementioned internal slanting channel in head a. Channel v has an entrance or opening situated at the region of the convex bent between portions g and h of member g,h. The lower portion g of member g,h defines a third internal channel to which reference character l has been applied. Channel l extends in a direction longitudinally of the portion g of intra-medullary nail g,h, intersects said second channel v and has an entrance situated at the aforementioned upper portion h of elbow-shaped member g,h. Reference character d has been applied to indicate a first pin having a pointed end situated outside member g,h and projecting through the region of the convex bent of member g,h into the upper portion h thereof. Reference character m has been applied to indicate a second pin arranged inside of channel l and inside the lower portion g of elbow-shaped member g,h. The head portion a is preferably of a plastic material and supports a metallic substantially spherical shell b shown in detail in FIG. 2. The body o of a resilient substance, e.g., rubber, is arranged at the end of said first channel of said head portion a adjacent said spherical shell b and is covered by the latter. The upper portion h of elbow-shaped member g,h is loosely inserted into said first channel in head portion a and abuts with one end surface thereof against said body o of said resilient substance. Reference character t has been applied to indicate the edge of metallic cap or shell b. The base c of head portion a has a rim u to which shell b is affixed. Reference character p has been applied to indicate cavities formed between shell b and body o of resilient material, which may be a rubberlike substance.
FIG. 2 shows cap or shell b as being a deep drawn metal part being spherical at the top or apex and including a cylindrical lower portion q bounded by dotted lines r and s. Shell b may be affixed to base c by pressing the cylindrical portion q thereof into rim u of head portion a.
The elbow-shaped member g,h of a thermoplastic material such as polyethylene is formed by machining a straight shaft, e.g., by means of a lathe, providing it with the above described channels and then imparting to it the desired elbow-shape upon heating thereof to about 80°-100° C. Channel v is drilled to its full diameter to receive stud d only following bending of part g,h to its elbow-shape.
While performing the hip joint operation the surgeon may re-heat and re-shape part g,h in accordance with particular requirements. The pin or stud d is conical at its end remote from head a as indicated at f. Portion f of stud d is provided with a plastic cover e. The intra-medullary nail g,h may be inserted in warm and softened condition upon resection of the natural femoral head. Rod m is inserted into part g,h after the latter has been inserted by the surgeon into place. Thereupon the surgeon drills a hole into the trachanter side of the femur to insert stem or pin d with its end e into the bone.
It will be apparent from the above that the present hip joint prosthesis can be implanted without massive resection and allows to propagate hip joint forces throughout the femur much as in the natural state. The dimensional stability of the present endoprosthesis is largely due to the presence of the two intersecting passages v,l and that of the two pins m and d. Part o of rubber or spongy material forms a particularly effective shock-absorber.