Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to improvements in attachi~g
fibrous connective tissue to bone, and in particular to tendon
and ligament prostheses.
It has been proposed to replace a tendon by either
directly grafting in place a tendon ~rom a less important part
of the body or by employing an artificial tendon such as a cord
of an inert plastics material. To directly gra~t in place a
tendon from another part of the body can cause adhesions between
the grafted tendon and the surrounding tissue. This leads to a
consequent loss of mobility. Problems have also arisen over
securing tendon prostheses to the bone and the muscle (especially
the former) with sufficient strength to withstand long term use. .
One major problem is providing a sufficiently strong
securing means between the fibrous connective tissue and the bone.
Various methods have been devised for anchoring tendon prostheses: :~
~any of these methods have involved mesh-like materials which are
emplo~ed to enable tissue infiltration into the mesh to occur so
as to provide a strong bond These me~hods.arei~iscussed, for
example, in the U.S. Patent ~o. 3,805,300. It is also known to
20 construct certain bone implants using porous material, the pores
facilitating anchorage of the bone to the implant as a result o
bone growth into the pores (see U.S. Patent No. 3,808,606). At
present, however, there is still a need for improved means for
connecting fibrous connective tissue to bone. :
According to the present invention there is provided a
bone implant ~or attaching ~ibrous connective tissue (either
artificial or natural), such as a tendon or ligament, to bone,
: which implant comprises a tapered porous plug.
The reason for ta.pering the.plug is to provide intimate
contact o~ plug and bone by action of the tension in the ~ibrous . :.
tissue. During the healing process, this intimate contact will
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promote the ingrow~h of calcified bone rather than soft tissue
by restricting or stopping movement of the plug relative to the
surrounding bone.
In a preferred aspect of the invention there is
provided a tendon prosthesis provided at its distal end thereof
with a bone implant in accordance with the invention.
In use in a tendon prosthesis the plug is located in a
correspondin~ recess in the bone at the distal end o~ the tendon
prosthesis and the end o~ the prosthesis remote ~rom the plu~ is
laced to the proximal tendon or muscle. Since the plug is -
porous, in time, bone tissue grows into and through the voids in
the plug and this provides a very secure attachment ~or the
tendon prosthesis to the bone. The plug is tapered and attached
to t~e remainder of the prosthesis so that, in use, the plug is
held in tension in the direction of the taper. With this
arrangement the tapered plug is held firmly in its bone resection.
The plug may be formed of any biocompatible material, for example
; a suitable ceramic, metal, or plastics material. Since it is ' ,
porous, a convenient method for its manufacture is by sintering
ceramic, metal or plastics particles into a suitable tapered form.
Preferably the plug is of sintered metal, especially sintered
titanium, niobium, or tantalum,or an alloy containing one or more
thereof. In one preferred method of manufacture, titanium wlre
of 20 to 200 microns diameter is wound around on a fine mandrel
to provide a coil, pulled off the mandrel and extended so as to
produce a series of helical regions. This wire is then pacXed
into a suitably-shaped die, compacted, and heated in a vacu~m or
inert gas so as to sinter the wire into a compact body. Prefer-
- ably as many pores as possible in the sintered body should have
a diameter or width of 100 to 400 microns. Winding the wire on
the mandrel and extending it as described above avoids forming
dense regions in the structure.
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The fibrous connective tissue may be conn;ec~ed to the
plug by any suitable means. A ligament can be looped around and
tied to the plug, for example as described hereinafter. The
replacement for the original fibrous connective tissue in a
tendon prosthesis can be attached to the plug by adhesive or
it can be formed integrally therewith. Preferably, however,
specific means are provided for anchoring the fibrous connactive
tissue to the plug, for example by providing a pin which extends
transversely of the connective tissue and locates in a recess
10 the pl~g. For a tendon prosthesis, the plug is preferably
frusto-conical. The plug may be provided with a passageway to
receive an end of the fibrous connecti~e tissue.
The tendon prosthesis of the invention, in addition to
the bone implant described above, is preferably provided with a
cord member havin~ its central portion coated or sheathed with
a material to promote sliding movement of the cord member within
the bodyO
The cord member will generally be substantially non-
résilient and may be, for example, of braided form, a mono-
filament, or even strip-like. Preferably, it is an inert
synthetic plastics material, such as a polyester or a poLyamide
thread.
The sheath or coating for the cord member may be of
any appropriate inert material (such as synthetic plastics
material) and may be of any cross~section appropriate to the
cross-section of the cord member, for example, annular. A
sheath member may be, for example, a right cylindrical silicone ; -~
polymer or polyurethane tube. The sheath or coating acts as a
barrier against adhesions between the cord member and the
surrounding tissue and hence promotes sliding movement of the
cord member in the body~
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According to a broad aspect of the present invention
there is provided a prosthesis which comprises artificial
fibrous connective tissue and, at a dis-tal end of the tissue,
a bone implant comprising a tapered porous plug. The plug is
connected to the artificial tissue with the plug tapering in
the direction towards the artificial tissue.
Preferred features of the invention will now be
described, by way of example, with xeference to the accompany-
ing drawing in which:
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Figure 1 is a schematic representation of a tendon
prosthesis of the invention in place in the body between a
muscle and the distal phalallx of a finger in a hand.
Figure 2 is a cross-section of the plug shown in
- Figure 1 with the cord member and pin in place, and
Figure 3 is a schematic perspective view of a bone
implant according to the invention in use in securing a ligament
to bone.
Referring to Figure 1, the tendon prosthesis comprises
a polyurethane coating 1, a cord member 2 consisting of four
strands of polyethylene terephthalate filament, and a plug 3.
The tendon extends between a muscle-tendinous junction 4 and
the bone of the distal phalanx 5.
The plug 3 is formed by sintering together titanium
wires and is porous to the extent that approximately 50% of its
apparent volume is constituted by voids. The plug 3 is frusto-
conical and is provided with an axial bore 6 through which the -
cord member passes and a recess 7 in which is located a locking
pin 8. The locking pin 8 is transverse to the cord member and
the cord filaments double around the pin 8, so that the ends of ;~
the filaments are remote from the plug. This arrangement
prevents the cord member from pulling through the axial bore 6
in the direction of muscle 4 and provides an attachment between
the cord and the plug of great strength and small volume.
A resection 9 is provided in the distal phalanx 5 to
provide a close fit with the plug 3. The strands of the cord
member 2 remote from the plug are separated, are passed through
the musculo-tendinous junction 4, and are then laced thereto. -
Referring to Figure 2, it will:be seen that the axial ~-
bore 6 is counter-bored from the surface adjacent recess 7 so
as to accommodate the loop which is formed when the cord member
2 is doubled around the~pin 8.
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Figure 3 shows a plug 10 which is generally wedge-
shaped and whlch is inserted in the bone resection 11 with the
thin edge 12 of the wedge lying axially within the resection.
A bore 13 is provided through the bone adjacent the thin edge
12 so as to take the end of a ligament 14 which is looped and
tied around the plug 10. The bore is taken to the thin edge of
plug in such a manner that in use the tension on khe plug is in
the direction of the wedge-taper.
Since the bore implants and tendon prostheses of this
invention are placed in the body surgically, it is desirable that
they be supplied in sterile, sealed packages. It may be conve-
nient to include in each package an appropriate reamer for
resecting the bone to receive the plug.
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