Invention (Patent Application Publication): Romagnoli
S. Corrective element for the articulation between the femur and the pelvis. ITMI20030274A1 (2004).
Current Assignee: Individual
Worldwide applications 2003 IT 2004 AU EP CA US WO
Status: Abandoned
Corrective element for the articulation between
the femur and the pelvis
Sergio Romagnoli
Abstract
A corrective element
for the articulation between the femur and the pelvis, comprising a contoured
body that can be inserted, without dislocation of the head of the femur, in the
iliac acetabular region after incision of the articular capsule; the contoured
body has a smooth outer surface that is substantially adapted to the iliac
acetabular region and an inner surface that forms a seat for accommodating the
femur head.
Description
TECHNICAL FIELD
[0001]
The present invention relates to a corrective element
or implant for the articulation between the femur and the pelvis.
BACKGROUND ART
[0002]
As is known, when problems in the articulation between
the femur and the pelvis arise, currently the head of the femur is extracted
from the acetabular seat and a prosthesis is inserted, by way of the most
disparate technologies, recreating in practice the seat for accommodating the
head of the femur.
[0003]
This approach is particularly traumatic, since
dislocation of the head of the femur causes considerable problems and further
entails performing long and complex surgery.
DISCLOSURE OF THE INVENTION
[0004]
The aim of the invention is to eliminate the drawbacks
noted above, by providing a corrective element for the articulation between the
femur and the pelvis that allows to restore correct articulation without having
to dislocate the head of the femur.
[0005]
Within this aim, an object of the invention is to
provide a corrective element that can be positioned in situ rapidly and easily,
allowing to use a surgical method that is not invasive and reduces all the
negative side effects linked to conventional surgery.
[0006]
Another object of the present invention is to provide
a corrective element for the articulation between the femur and the pelvis that
thanks to its particular constructive characteristics is capable of giving the
greatest assurances of reliability and safety in use.
[0007]
Another object of the present invention is to provide
a corrective element for the articulation between the femur and the pelvis that
can be obtained easily starting from commonly commercially available elements
and materials and is advantageously competitive from a merely economical
standpoint.
[0008]
This aim and these and other objects that will become
better apparent hereinafter are achieved by a corrective element for the
articulation between the femur and the pelvis, according to the invention,
characterized in that it comprises a contoured body that can be inserted,
without dislocation of the head of the femur, in the iliac acetabular region
after incision of the articular capsule, said contoured body having a convex
smooth outer surface that reproduces the acetabular shape and a concave smooth
inner surface that forms the seat for accommodating said femur head.
[0009]
This implant remains free and is not fixed by primary
or secondary fixation. Its shape utilizes the load resultant and self-centers
and is kept stable by the contact surfaces (head-femur-acetabulum) by muscle
tension and by the articular capsule.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
Further characteristics and advantages of the
invention will become better apparent from the description of a preferred but
not exclusive embodiment of a corrective element for the articulation between
the femur and the pelvis, illustrated by way of nonlimiting example in the
accompanying drawings, wherein:
[0011]
FIG. 1 is a schematic perspective view of the
corrective element according to the invention;
[0012]
FIG. 2 is a sectional perspective view of the
corrective element, taken from the other side;
[0013]
FIG. 3 is a schematic side view of the step for
the movement of the muscle bundles at the articulation between the femur and
the pelvis;
[0014]
FIG. 4 is a view of the initial step of insertion
of the contoured body between the head of the femur and the acetabulum;
[0015]
FIG. 5 is a schematic view of the contoured body
after its insertion;
[0016]
FIG. 6 is an enlarged-scale view of the contoured
body arranged in the acetabulum and of the repositioned muscle bundles;
[0017]
FIG. 7 is a plan view of the corrective element
according to a further embodiment;
[0018]
FIG. 8 is an elevation view of the corrective
element of FIG. 7;
[0019]
FIG. 9 is a sectional view of FIG.
7 taken along a median plane;
[0020]
FIG. 10 is a plan view of the corrective element according
to still another embodiment;
[0021]
FIG. 11 is a sectional view of FIG.
10 taken along a median plane.
WAYS OF CARRYING OUT THE INVENTION
[0022]
With reference to the figures, the corrective element
for the articulation between the femur and the pelvis, according to the
invention, comprises a contoured body 1, which is preferably made of
steel and has a shape that approximate a spherical portion.
[0023]
The contoured body 1 has a beveled
insertion edge 2, in which the thickness decreases to zero, and has, in a
central portion, a central recess 3 for the reason explained
hereinafter.
[0024]
On the opposite side, the body 1 has a
pushing and positioning edge 4, provided with multiple
holes 5 for manipulation by means of a suitable instrument
or lever 10 that facilitates insertion operations.
[0025]
The instrument 10 has a push
plate 11 that is provided with coupling pins 12 that
enter the holes 5 located on the pushing edge 4, and
there is also a complementary jaw 14, which is actuated by a suitable lever
mechanism and engages the edge 4 on the opposite side, so as to
practically clamp the edge 4 on
the instrument 10 in order to allow to apply the force required
for insertion. The edge 4 lies substantially at right angles to
the surface of the body 1.
[0026]
In practical use, in order to insert the corrective
element, first the articular capsule is cut and optionally an osteotomy of
the upper part 20 of the greater trochanter is performed, moving
the muscle bundles, generally designated by the reference numeral 21.
[0027]
This exposes the iliac acetabular region, and after
cutting into the articular capsule, as shown schematically in FIG. 4, it
is possible to begin the insertion of the contoured body, which in practice is
fitted over the head of the femur, designated by the reference
numeral 30, and is inserted in the acetabulum.
[0028]
As insertion continues, the contoured
body 1 is arranged so that it lies in close contact with the iliac
acetabular region, since the contoured body has an outer surface that is shaped
substantially complementarily to the iliac acetabular region and has an
internal surface that forms a seat for accommodating the head of
the femur 30.
[0029]
This coupling in practice achieves self-positioning
and self-centering of the corrective element in the acetabulum, accordingly
achieving the possibility to restore the correct articulation without having to
first dislocate the head of the femur.
[0030]
Once positioning of the contoured body has been
performed, the muscle bundles are repositioned and any portion of the greater
trochanter that had been osteotomized is reconnected by using
conventional surgical pins 40. Another surgical technique can also be
carried out, i.e. without greater trochanter osteotomy and only with posterior
or anterior capsulotomy.
[0031]
With reference to FIGS. 7,
8 and 9 an outer spherical surface 22 and an
inner spherical surface 23 of the contoured
(shell-like) spacer 1 terminate in an
approximately equatorial plane 15 in correspondence with a
pushing and positioning edge 4, which extends in
the plane 15 only over a part of the periphery. If referred to
a pole axis 24 of the pushing and positioning edge, the same
extends through an angle β with a
value from 130° to 180°. For the overall rigidity it is even more suitable for
the value of β to be
above 150°. Clear of the pushing and positioning edge 4 the
outer and the inner spherical surfaces 23 and 22 are
connected by an insertion edge 2, which in relation to
the positioning edge 4 constitutes a central
recess 3 around the pole region. In plan view (FIG. 7) it can be seen
that the spherical surfaces 22 and 23, when related to
the pole axis 24, describe an angle a larger than 180°. The angle a
can exceed 210°. In the bisector of the angle β the contoured body or spacer 1 has a plane
of symmetry 25, which divides the spacer into a left half and a right
half. The pole axis 24 forms, as seen in the plan view,
simultaneously a center 7 for the largest radius R2 of the
inner spherical face 23. With respect to the pole
axis 24 the recess 3 possesses a minimum radius R3,
which, in comparison to the largest internal radius, corresponds to a
percentage of 27% to 37%. In the left and right halves the insertion
edge 2 extends a distance d past the pole axis 24 in
the form of projecting ears 6, the distance d corresponding to 25% to
30% of the maximum inner radius R2 of the inner spherical
surface 23.
[0032]
If referred to the pole axis the pushing and
positioning edge 4 has an outer radius R1 which corresponds
to 120 to 140% of the radius R2. The positioning edge 4 can have
a thickness 16 from 1 to 5 mm. The
two ears 6 are, as shown in FIG. 7, smoothly rounded. The
actual edge between the inner and the outer spherical surfaces has a radius of
at least 0.5 mm. The wall thickness 17 becomes smaller between
the inner and outer spherical surfaces 23 and 22. In the
remaining portion the wall thickness 17 may have values from 1
to 3.5 mm.
[0033]
As shown in FIG. 8 the insertion
edge 2, when considered in a projection perpendicular to
the plane 25 of symmetry, extends away from the pushing and
positioning edge 4 along a straight line 19, extending
at an angle γ from
the plane 15. The angle γ can be
from 35 to 50°. If the angle γ is
selected to be from 40° to 45°, insertion of the implant is still possible and
furthermore a relatively large support surface is formed with
the ears 6.
[0034]
In accordance with the natural shape of a femur head
it is advantageous for the inner spherical face 23 to have a
flattened area in the eventual working direction. One form of such a flattened
area is illustrated in FIG. 9. In the plane of the drawing
two centers 9 are shown, which are arranged at a small distance ε apart and which respectively define (starting
with the outer border), based on a radius R4 the outline of the
inner spherical face 23. In the median portion, which is
characterized by an angle δ the
outline is continued, on the basis of a larger radius R5, to bridge over the
distance ε, which
may amount to 1 to 3 mm. The angle δ can
lie from 40 to 70°. It is important that the transition from one curvature to
the other curvature takes place continuously so that there is no irregularity
in the curvature. Another possibility of providing a flattened area in the
eventual working direction would be to provide smaller radiuses of curvature
toward the pole. The spherical surface would then correspond to a section, cut
in a very weak ellipsoid.
[0035]
If it is assumed that the pushing and positioning
edge 4 limits movements in relation to the acetabulum, then at least
the inner spherical surface 23 should have a roughness of less
than 0.1 μm.
[0036]
The embodiment of FIGS. 10 and 11, which in its
structure corresponds to the embodiment of FIGS. 7, 8 and 9,
includes as a further feature a bead 18 projecting in the middle
part of the central recess 3 toward the pole axis 24,
and such bead may constitute a further security means to prevent accidental
slipping out of place from the acetabulum. This could be an advantage in the
case of a spacer 1 of a rubber-like material.
[0037]
An application of the implant is in one case
conceivable for elderly patients with local damage of the femur head cartilage
or of the acetabulum cartilage. The implant would practically bridge over the
defective area. A further application is merely as a placekeeper with the
purpose of reducing pain. Elderly patients, who owing to the risk of a
thrombosis, cannot be subjected to a major operation like the complete
replacement of the hip joint could—more particularly if tied to a wheel
chair—be freed of part of their pain, since the operation would rather be
considered to be a minor one.
[0038]
The selection of the material for the implant is
therefore not limited at the outset. Rigid shells of a physiologically
compatible metal alloy are conceivable, which have a low roughness Ra of less
than 0.1 μm on their
load bearing surfaces 23 and 22. The implant may also consist of
a somewhat elastic physiologically compatible material. In the case of a merely
placekeeper function with small movements without a load elastic, rubber-like
but dimensionally stable plastics are conceivable.
[0039]
Moreover plastics in the form of a hydrogel could be
employed to provide inserts with a small wall thickness.
[0040]
Coating of the load bearing
surfaces 23 and 22 with a physiologically compatible
anti-friction layer with the body is conceivable as well.
[0041]
A further possibility is to endow the load bearing
surfaces with a porosity like that of the natural meniscus in order to favor colonization
with the own body cells.
[0042]
From the above description it is therefore evident
that the invention achieves the intended aim and objects, and in particular the
fact is stressed that a contoured body is provided which has, in its front
portion, a hollow that allows to preserve the round ligament and its
vascularization, accordingly maintaining optimum conditions for its integration
in the articulation without removing functional connections.
[0043]
The contoured body can be manufactured in different
sizes, depending on the anatomy of the patient, and can have various thickness,
depending on the defect to be corrected; one should bear in mind that the inner
and outer surfaces of the contoured body must be smooth, so as to allow its
insertion without particular traumas, and that the beveled penetration edge
must have a limited thickness both to facilitate its insertion and to avoid
producing a dangerous discontinuity in the seat for accommodating the head of
the femur.
[0044]
The invention thus conceived is susceptible of
numerous modifications and variations, all of which are within the scope of the
appended claims.
[0045]
All the details may further be replaced with other
technically equivalent elements.
[0046]
In practice, the materials used, so long as they are
compatible with the specific use, as well as the contingent shapes and
dimensions, may be any according to requirements.
[0047]
The disclosures in Italian Patent Application No. MI2003A000274
from which this application claims priority are incorporated herein by
reference.
What is claimed is:
1-23. (canceled)
24. A shell-like implant which is adapted to be inserted
between a natural femur head and a natural acetabulum as a spacer, comprising
an outer spherical surface, an inner spherical surface and a pushing and
positioning edge lying in one plane and extending over a part of the periphery,
and furthermore an insertion edge connecting the spherical surfaces, said edge,
in relation to the positioning edge, constituting an open recess around the
pole region.
25. The implant according to claim 24, wherein the
pushing and positioning edge, as considered from above in the direction of a
pole axis, describes an angle β from 130 to 180°.
26. The implant according to claim 24, wherein the
pushing and positioning edge, as considered from above and in the direction of
the pole axis, describes an angle β from 150 to 180°.
27. The implant according to claim 26, wherein the
spherical surfaces, as considered from above in the direction of the pole axis,
describe an angle α larger than 180°.
28. The implant according to claim 26, wherein the
spherical surfaces, as considered from above in the direction of the pole axis,
describe an angle α larger than 210°.
29. The implant according to claim 26, having, as
considered from above in the direction of the pole axis, a plane of symmetry in
a bisector of the angle β.
30. The implant according to claim 29, wherein the
insertion edge, considered in its projection perpendicularly to the plane of
symmetry, extends away from the pushing and positioning flange in a straight
line with an angle γ from 35° to 50°.
31. The implant according to claim 29, wherein the
insertion edge, considered in its projection perpendicularly to the plane of
symmetry, extends away with an angle γ from 40° to 45°.
32. The implant according to claim 24, wherein the
insertion edge has a minimum radius of 0.5 mm adjacent to a transition from the
inner to the outer spherical surfaces.
33. The implant according to claim 25, wherein, as
considered from above in the direction of the pole with the pole axis as the
center, the recess has a minimum radius R3, which corresponds to 27 to
37% of the maximum inner radius R2 of the inner spherical surface.
34. The implant according to claim 33, wherein
apart from the transition in the direction of the insertion edge a mean wall
thickness between the inner and outer spherical surfaces in a range from 1 to
3.5 mm is kept.
35. The implant according to claim 33, wherein, as
considered from above in the direction of the pole axis, an outer radius R1 of
the pushing and positioning flange is corresponding to 120 to 140% of the
radius R2 of the inner spherical surface.
36. The implant according to claim 33, wherein, as
considered from above in the direction of the pole axis, the recess is enlarged
by two ears projecting past the center, such ears projecting past the center by
a distance d, the distance d having a size from 25 to 30% of the maximum inner
radius R2 of the inner spherical surface.
37. The implant according to claim 24, wherein the
pushing and positioning edge has a thickness from 1 to 5 mm.
38. The implant according to claim 33, wherein the
inner spherical surface has a flattened area near the pole.
39. The implant according to claim 33, wherein in a
plane perpendicular to the straight line the radius R5 of curvature
of the inner spherical surface in the median region extending by an angle of δ is larger than the radiuses R4 of curvature in the two
laterally adjacent regions, the centers of the two laterally adjacent regions
differing by an amount of ε.
40. The implant according to claim 39, wherein the
angle δ is from 40 to 70° and that the amount ε is from 1 to 3 mm.
41. The implant according to claim 33, wherein at
least the inner spherical surface has a roughness Ra of less than 0.1 82 m.
42. The implant according to claim 24, made of a
physiologically compatible metal alloy, or a physiologically compatible
plastics, or of an elastic, rubber-like but dimensionally stable plastics.
43. The implant according to claim 42, consisting
of a hydrogel.
44. The implant according to claim 43, wherein the
bead consists of a hydrogel.
45. The implant according to claim 44, wherein at least
the inner spherical surface is coated with an anti-friction layer.
46. The implant according to claim 24, wherein at
least the inner spherical surface is porous and has pores which favor
colonization with cartilage cells from the own body.
External links
Romagnoli S. Corrective element for the articulation
between the femur and the pelvis. ITMI20030274A1 February 14, 2003. 2004. worldwide.espacenet
Romagnoli S. Corrective element for the articulation
between the femur and the pelvis. US20060149389A1
February 14, 2003. 2006. patents.google
Publications
of invention
AU2004212316 (A1)
CA2515920 (A1)
EP1592368 (A2)
ITMI20030274 (A1)
WO2004071331 (A2)
WO2004071331 (A3)
US2006149389 (A1)
2004RomagnoliS
Authors & Affiliations
Sergio Romagnoli – Vezzi Portio (IT).
Keywords:
ligamentum capitis femoris, ligamentum teres, ligament
of head of femur, endoprosthesis, prosthesis,
invention, unipolar, subtotal
NB! Fair practice / use: copied for the purposes of criticism, review, comment, research and private study in accordance with Copyright Laws of the US: 17 U.S.C. §107; Copyright Law of the EU: Dir. 2001/29/EC, art.5/3a,d; Copyright Law of the RU: ГК РФ ст.1274/1.1-2,7
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