GB2458218A

GB2458218A - Co-moulded single-piece prosthetic finger joint made from liquid silicone rubber and polyether ether ketone

Info

Publication number: GB2458218A
Application number: GB0904350A
Authority: GB
Inventors: John Neil Devine; Marcus Jarman Smith; Joerg Shlegel; Irene Sinz
Original assignee: Invibio Ltd
Current assignee: Invibio Ltd
Priority date: 2008-03-14
Filing date: 2009-03-13
Publication date: 2009-09-16
Also published as: GB0804788D0; WO2009112865A1; GB0904350D0

Abstract

An implantable prosthesis made from first and second materials which may be polyetheretherketone (PEEK) and a silicone rubber. The materials may be injection moulded into unitary finger joints and craniomaxillofacial implants (100, figure 12) in a co-moulding process. An exemplary finger joint has a body 20 made of silicone rubber which defines intramedullary shafts 12, 14 and a hinge portion 22. Regions 24, 26 of the body on opposing sides of hinge 22 are over-moulded with a protective reinforcing sleeve of PEEK. The co-moulding process may utilize heat from the first injected material to cure the second injected material.

Description

Iinplantable Prosthesis This invention relates to an implantable prosthesis for implantation into a human or animal body, for example to replace or supplement a part which has become damaged, diseased or worn. Preferred embodiments relate to prosthetic joints, for example finger joints.

One of the best known and most widely used flexible finger joint implants is the SWANSON (Trade Mark) finger joint sold by Wright Medical Technology, Inc. The original prosthetic joint is described in a patent filed in 1967 (US 3462765; Inventor: Swanson) and comprises a one-piece joint of molded silicone rubber. The joint comprises an enlarged centre portion about which stem portions, which project from diametrically opposite sides of the centre portion, pivot. The original joint was improved according to a further patent (US3875594; Inventor: Swanson) which describes a one-piece silicone rubber joint comprising a large mid-section and a pair of oppositely projecting stem portions. The improvement described related to the provision of a channel in the mid-section to improve the * * * flexibility of the hinge of the joint.

S * I..

:25 A later patent (US4158893), also invented by Swanson, 5S5 addressed a problem encountered in use of SWANSON joint implants namely the fracture of the prosthesis due to a .** laceration or tear of the prosthesis, particularly in *..: regions adjacent the hinge. Referring to figure 1 herein which is a partial cross-section of a human hand, the solution according to the patent involves providing sleeves 2,4, for example of titanium, which are surgically implanted into each of the intramedullay canals 6, 8 prior to implantation of the flexible joint which includes stem portions 12, 14 of the implant. The sleeves then protect the stem portions from damage and, it is hoped, prevent premature failure of the joint. However, although the joint described in US4158893 is commercially available, it is not universally accepted because implantation of the sleeves into the intermedullay canals is difficult and time-consuming and often possible benefits of using the sleeves are outweighed by associated disadvantages.

It is an object of the present invention to address problems associated with implantable prostheses, for example prosthetic joints such as finger joints.

According to a first aspect of the invention, there is provided an implantable prosthesis for implantation in a human or animal body, the prosthesis comprising a first material and a second material which are integrally formed with each other.

Said first and second materials are preferably in intimate contact with each other. Said first and second materials * * S * preferably contact each other in an intimately adhering * S...

manner. S. * 25 S**

Preferably, at positions of contact between the first and second materials no adhesive made of a material which is S. * S * ** different from said first and second materials is * .

S

provided. Whilst the first and second materials may be adhered to one another any adhesive force is preferably due to the nature of the first and second materials themselves, rather than by inclusion of a separate adhesive between the first and second materials.

Preferably, one of said first and second materials is over-moulded on the other of said first or second materials.

Preferably, said first and second materials are co-moulded.

The ratio of the weight of the first material to the weight of the second material in the implantable prosthesis may be in the range 0.02 to 50, suitably in the range 0.025 to 40, preferably in the range 0.033 to 30, more preferably in the range 0.05 to 20, especially in the range 0.01 to 10.

Said implantable prosthesis is preferably articulated.

Said prosthesis suitably includes a first region which is movable, for example arranged to pivot, relative to a second region. The prosthesis suitably includes an intermediate region arranged between the first and second regions. The intermediate region suitably defines a joint which is arranged to replace a joint of a human or animal body into which the prosthesis may be implanted in use. * S..

The intermediate region is preferably more flexible than *..S the first region. It is preferably also more flexible than the second region. Thus, when implanted, the first V... and second regions may be relatively rigid and may be *..: arranged to replace relatively rigid body materials for example bone and the intermediate region is more flexible and is arranged to replace a relatively flexible region such as a joint.

Said implantable prosthesis preferably includes an artificial joint which is integral and/or unitary with other parts of the prosthesis.

In a first embodiment, said prosthesis includes a first part which comprises (preferably consists essentially of) said first material, wherein a layer comprising (preferably consisting essentially of) said second material overlies said first material and is suitably in intimate contact therewith. Said second material may encapsulate an area of said first material. It may be positioned in a region or regions of said prosthesis which may be most likely to be susceptible to damage and/or wear in use. Said second material preferably does not encapsulate an area overlying a joint of said prosthesis.

In a second embodiment, said prosthesis includes a first part which comprises (preferably consists essentially of) said first material wherein a reinforcing means which comprises (preferably consists essentially of) said second material is preferably embedded in said first material.

Said reinforcing means is preferably arranged to reinforce * * * parts of said prosthesis adjacent a joint thereof. Said reinforcing means may extend across a joint of the *.r25 prosthesis. In this case, it suitably includes regions of different flexibilities. For example the reinforcing means may include a relatively flexible region positioned substantially centrally to the joint, thereby to allow the * *. joint to flex and a less flexible (e.g. more rigid) region adjacent, for example on opposing sides of, a central region of the joint. Such a reinforcing means may include a narrow stem which traverses the joint and on opposing sides thereof bulbous elements; or may include a hollow region arranged centrally to the joint and more solid regions on opposing sides thereof. Alternatively, the reinforcing means may not extend across a joint but may be defined on opposing sides of the joint. It may comprise elongate members which extend from positions adjacent the joint on opposing sides thereof along stem regions of the prosthesis; or it may comprise short reinforcing bodies which are positioned adjacent the joint and which do not substantially extend along stem regions of the prosthesis.

In a third embodiment, said prosthesis may include a first part which comprises (preferably consists essentially of) said first material wherein said first part is flexible and defines a joint of the prosthesis; a second part on one side of said first part which comprises (preferably consists essentially of) said second material; and a third part on an opposite side of said first part which comprises (preferably consists essentially of) said second material; wherein said second and third parts make face to face contact with said first part.

Said prosthesis preferably includes first and second * * * connection means for connecting the prosthesis to a body in which it is to be implanted. Said connection means preferably are in the form of elongate members, for example stems, which are arranged to be inserted into openings defined in a human or animal body.

Said prosthesis may be arranged to define an artificial joint. Said prosthesis may be a craniomaxillofacial implant or a finger joint.

When said prosthesis is a finger joint, said joint may comprise a said first region which is arranged to pivot relative to a said second region, a said intermediate region being defined between the first and second regions, wherein said first and second regions suitably define elongate stems, ends of which are arranged to be inserted into openings defined in a human or animal body in which the prosthesis is to be implanted in use. The elongate stems suitably taper inwardly towards their free ends.

Said intermediate region may be wider than said stems.

In one embodiment, said prosthesis include a first body which comprises said first material, wherein said first body defines said first and second regions and said intermediate region and wherein said second material encapsulates at least part of each of said first and second regions (e.g. stems) . The second material may encapsulate substantially the entirety of each stem; or may encapsulate a region of each stem adjacent the intermediate region, for example by respective bands comprising said second material being positioned adjacent said intermediate region. * * * * * * .** * *

In another embodiment, a said reinforcing means which comprises said second means may be embedded in the first **** material so that it is positioned within the first and second regions (e.g. stems) of the prosthesis. The reinforcing means may extend across the intermediate region in which case the flexibility of the reinforcing means within the intermediate region is suitably greater than its flexibility in regions adjacent said intermediate region. Alternatively, the.reinforcing means may not extend across the intermediate region but may be provided adjacent thereto.

Said first material preferably comprises an elastomer.

Said elastomer may have a Shore A hardness (ASTM, D2240) of at least 5, preferably at least 10, more preferably at least 20. The hardness may be less than 100, suitably less than 85.

Said elastomer may have a tensile strength (ASTM, D412) of at least 3MPa, more preferably at least 5MPa. The tensile strength may be less than 2OMPa, suitably less than 15MPa.

The elongation % (ASTM, D412) may be at least 200, preferably at least 400. The elongation % may be less than 1500, suitably less than 1200.

The tear strength of the elastomer (ASTM, D624) may be at least lOkN/m, suitably at least l5kN/m. The tear strength may be less than 6OkN/m.

Said elastomer may have a hardness, measured on the Shore * *** * * * * A scale, of less than 120, suitably less than 110, * *** preferably less than 90, more preferably less than 80, r25 especially 70 or less. The hardness on said Shore A scale * may be greater than 5, preferably 10 or greater.

Said first material may be non-self-adhesive. ** * * * * **

Said first material may comprise a thermoplastic elastomer.

Said first material may comprise a silicone elastorner. It may comprise a liquid silicone rubber or solid silicone rubber, with a liquid silicone rubber being preferred.

Said first material preferably includes at least 6Owt%, suitably at least 75wt%, preferably at least 9Owt%, more preferably at least 95wt% of said elastomer. Preferably, said first material consists essentially of said elastomer.

Said second material preferably comprises a polymeric material, for example a bio-compatible polymeric material.

Said polymeric material may have a Notched Izod Impact Strength (specimen 80mm x 10mm x 4mm with a cut 0.25mm notch (Type A), tested at 23°c, in accordance with 1S0180) of at least 4KJm2, preferably at least 5KJm2, more preferably at least 6KJm2. Said Notched Izod Impact Strength, measured as aforesaid, may be less than 1OKJm2, suitably less than 8KJm2.

The Notched Izod Impact Strength, measured as aforesaid, * * 0 may be at least 3KJnI2, suitably at least 4KJm2, * *0* preferably at least 5KJm2. Said impact strength may be *:** 25 less than 50 KJm2, suitably less than 30KJm2.

Said polymeric material suitably has a melt viscosity (MV) of at least 0.06 kNsrn2, preferably has a MV of at least 0.09 kNsm2, more preferably at least 0.12 kNsm2, especially at least 0.15 kNsm2.

MV is suitably measured using capillary rheometry operating at 400°C at a shear rate of 1000s' using a tungsten carbide die, 0.5x3.175mm.

Said polymeric material may have a MV of less than 1.00 kNsm2, preferably less than 0.5 kNsm2.

Said polymeric material may have a MV in the range 0.09 to 0.5 kNsm2, preferably in the range 0.14 to 0.5 kNsm2.

Said polymeric material may have a tensile strength, measured in accordance with 1S0527 (specimen type ib) tested at 23°C at a rate of 50mm/minute of at least 20 MPa, preferably at least 60 MPa, more preferably at least 80 MPa. The tensile strength is preferably in the range 80-110 MPa, more preferably in the range 80-100 MPa.

Said polymeric material may have a flexural strength, measured in accordance with 1S0178 (80mm x 10mm x 4mm specimen, tested in three-point-bend at 23°C at a rate of 2mm/minute) of at least 50 MPa, preferably at least 100 MPa, more preferably at least 145 MPa. The flexural * S * strength is preferably in the range 145-18OMPa, more S.-'.

preferably in the range 145-164 MPa.

S *IS*

* Said polymeric material may have a flexural modulus, *.I measured in accordance with 1S0178 (80mm x 10mm x 4mm specimen, tested in three-point-bend at 23°C at a rate of 2mm/minute) of at least 1 GPa, suitably at least 2 GPa, preferably at least 3 GPa, more preferably at least 3.5 GPa. The flexural modulus is preferably in the range 3.5- 4.5 GPa, more preferably in the range 3.5-4.1 GPa.

Said polymeric material may be amorphous or semi-crystalline. It is preferably semi-crystalline.

The level and extent of crystallinity in a polymer is preferably measured by wide angle X-ray diffraction (also referred to as Wide Angle X-ray Scattering or WAXS), for example as described by Blundell and Osborn (Polymer 24, 953, 1983) . Alternatively, crystallinity may be assessed by Differential Scanning Calerimetry (DSC) The level of crystallinity of said polymeric material may be at least 1%, suitably at least 3%, preferably at least 5% and more preferably at least 10%. In especially preferred embodiments, the crystallinity may be greater than 25%.

The main peak of the melting endotherm (Tm) of said polymeric material (if crystalline) may be at least 300°C.

Said polymeric material may include a repeat unit of general formula -f f-E _f Ar-f E-)_(-1_ CO -1E_G f(i)_ co or a repeat unit of general formula *... * * S... *.** **.. S.. S. * . * *.. S* * *.

-f f-E _f Ar-E.)_f@J_ so2_163)_ G f(i'j)-2_c6J-]4} wherein A, B, C and D independently represent 0 or 1, E and E' independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a -O--Ph-O-moiety where Ph represents a phenyl group, rn, r, s, t, v, w, and z represent zero or 1 and Ar is selected from one of the following moieties (i) to (v) which is bonded via one or more of its phenyl moieties to adjacent moieties * S * S* S S... * . *SSS 5..

S 55..

S S.

S S. * S * .*. S. I S5 55

(ii) O___co__O_co (iii) (iv) Q (3 Unless otherwise stated in this specification, a phenyl moiety has 1,4-, linkages to moieties to which it is bonded. * S S

Said polymeric material may be a homopolymer which includes a repeat unit of IV or V or may be a random or block r copolymer of at least two different units of IV and/or V. * **.

S *. * * * *S. S* S * S * * S.

As an alternative to a polymeric material comprising units IV and/or V discussed above, said polymeric material may include a repeat unit of general formula G f(E6 COia E _f Ar)-(-1J--)--E' or a homopolymer having a repeat unit of general formula So2-_-1)_G f(13). so2_16})_.f E -f Ar--E.)] wherein A, B, C, and D independently represent 0 or 1 and E, E', G, Ar, m, r, s, t, v, w and z are as described in

any statement herein.

Said polymeric material may be a homopolymer which includes a repeat unit of IV or V or a random or block copolymer of at least two different units of IV* and/or V. Preferably, said polymeric material is a homopolymer having a repeat unit of general formula IV.

Preferably Ar is selected from the following moieties (vi) to (x) * * * ** * S... * . S... *..S S... S.. S. * . * **. S* S S S* * SS (vi)

(vii) ------co ___co__Q___ (viii) (ix) In (vii), the middle phenyl may be 1,4-or 1,3-substituted.

Suitable moieties Ar are moieties (ii), (iii), (iv) and (v) and, of these, moieties, (ii), (iii) and (v) are preferred.

Other preferred moieties Ar are moieties (vii), (viii), (ix) and (x) and, of these, moieties (vii), (viii) and (x) *...

are especially preferred. * * * *.* ** * * S * * S.

An especially preferred class of polymeric materials are polymers (or copolymers) which consist essentially of phenyl moieties in conjunction with ketone and/or ether moieties. That is, in the preferred class, the polymer material does not include repeat units which include -S-, - SO2-or aromatic groups other than phenyl. Preferred bio-compatible polymeric materials of the type described include: (a) a polymer consisting essentially of units of formula IV wherein Ar represents moiety (v), E and E' represent oxygen atoms, m represents 0, w represents 1, G represents a direct link, s represents 0, and A and B represent 1 (i.e. polyetheretherketone) (b) a polymer consisting essentially of units of formula IV wherein E represents an oxygen atom, E' represents a direct link, Ar represents a moiety of structure (ii), m represents 0, A represents 1, B represents 0 (i.e. polyetherketone); (c) a polymer consisting essentially of units of formula IV wherein E represents an oxygen atom, Ar represents moiety (ii), m represents 0, E' represents a direct link, A represents 1, B represents 0, (i.e. polyetherketoneketone) (d) a polymer consisting essentially of units of 30 formula IV wherein Ar represents moiety (ii), E and E' represent oxygen atoms, G represents a direct link, m represents 0, w represents 1, r * * * *** S. S S * * S *S represents 0, s represents 1 and A and B represent 1. (i.e. polyetherketoneetherketoneketone) (e) a polymer consisting essentially of units of formula IV, wherein Ar represents moiety (v), E and E' represents oxygen atoms, G represents a direct link, m represents 0, w represents 0, s, r, A and B represent 1 (i.e. polyetheretherketoneketone).

(f) a polymer comprising units of formula IV, wherein Ar represents moiety (v), E and E' represent oxygen atoms, m represents 1, w represents 1, A represents 1, B represents 1, r and s represent 0 and G represents a direct link (i.e. polyether-diphenyl-ether-phenyl_ketone_phenyl.) Said polymeric material may consist essentially of one of units (a) to (f) defined above. Alternatively, said polymeric material may comprise a copolymer comprising at least two units selected from (a) to (f) defined above.

Preferred copolymers include units (a) . For example, a copolymer may comprise units (a) and (f) ; or may comprise units (a) and (e) Said polymeric material preferably comprises, more preferably consists essentially of, a repeat unit of formula (XX) * . * *** ***.

---****

** 30 -o / ° / 1C0 / / Co / vi *. * * * SS* ** S * S * * I.

where ti, and wi independently represent 0 or 1 and vi represents 0, 1 or 2. Preferred polymeric materials have a said repeat unit wherein ti=l, vl=0 and wl=O; tl=0, vl=0 and wl=0; ti=0, wl=1, vl=2; or tl=O, vl=i and wl=0. More preferred have ti=1, vi=0 and wl=0; or tl=0, vl=0 and wl=0. The most preferred has ti=1, vl=0 and w10.

In preferred embodiments, said polymeric material is selected from polyetheretherketone, polyetherketone, polyetherketoneetherketoneketone and polyetherketoneketone. In a more preferred embodiment, said polymeric material is selected from polyetherketone and polyetheretherketone. In an especially preferred embodiment, said polymeric material is polyetheretherketone.

Said polymeric material may have a hardness on the Rockwell R Scale of greater than 70, suitably greater than 90, preferably greater than 100, more preferably greater than 110, especially greater than 120. Preferably said first polymeric material has a hardness on the Rockwell R scale in the range 120 to 130.

Said second material preferably includes at least 6Owt%, suitably at least 75wt%, preferably at least 9Owt%, more preferably at least 95wt% of said polymeric material.

Preferably, said second material consists essentially of said second material. S... * S * *..

30 The sum of the wt% of said first and second materials in S...

said prosthesis may be at least 6Owt%, is suitably at least 75wt%, is preferably at least 85wt%, is more preferably at least 9Owt% and is especially at least 95wt%. In a preferred embodiment, said prosthesis Consists essentially of said first and second materials.

The prosthesis may include at least lOwt%, preferably at least 2Owt% of said second material. The prosthesis may include less than 9Owt%, preferably less than 8Owt%, more preferably less than 7Owt% of said first material.

The ratio of the wt% of said first material to the second material may be in the range 0.1 to 9.

Said implantable prosthesis is preferably a moulded part and more preferably is produced substantially entirely in a moulding process.

In a variation of the invention of the first aspect, a second material, for example in the form of fibres, may be embedded in a matrix defined by a said first material.

The fibres, for example of polyetheretherketone, may reinforce the first material, for example silicone and prevent its premature failure.

According to a second aspect of the invention, there is provided a method of making an implantable prosthesis, the method comprising co-moulding a first material and a second material to define at least part of (preferably substantially the whole of) said prosthesis. *.**

The method preferably comprises moulding, for example : 30 injection moulding, a first part of the prosthesis from said first or second material and then co-moulding the other one of said first or second material to define a second part of the prosthesis.

The method may comprise: a) moulding the second material; b) contacting the second material with the first material (or one or more precursors thereof) whilst the second material is at a temperature of greater than 100°C and/or whilst the second material is at a sufficiently high temperature that it retains sufficient latent heat to cure the first material (or one or more precursors), whereby the temperature of the first material aids curing of the first material.

The temperature of the second material may be at least 120°C, preferably at least 130°C, more preferably at least 140°C, especially at least 150°C when it is contacted with said first material (or one or more precursors thereof) In some cases, the temperature may be at least 160°C or at least 170°C when said second material is contacted with said first material (or one or more precursors thereof) Said second material may be injection moulded. Suitably said second material is at a temperature in excess of 300°C, preferably in excess of 350°C, more preferably in excess of 400°C, prior to contact with a mould.

Prior to contact with said second material, the surface temperature of a surface of said mould which contacts said S...

. . second material may be at a temperature in the range 160°c : 30 to 200°C, preferably 160°C to 190°C. U...

S *5*

Said second material is preferably moulded in a first : ... mould. Contact of said second material with said first * S.

S

material (or one or more precursors thereof) may take place whilst said second material is in said first mould.

Thus, the method may comprise injecting said first material (or one or more precursors thereof) into said second mould, suitably so that said first material (or one or more precursors thereof) contacts said second material in selected positions so that said first material may define a moulded component which is intimately contacted with said second material.

Contact of said first material (or one or more precursors thereof) with said second material may take place substantially immediately after moulding of said second polymeric material. For example, the time elapsing between the completion of injection of said second material into the first mould and contact of said second material with first material (or one or more precursors thereof) may be less than 30 minutes, suitably less than minutes, preferably less than 5 minutes, more preferably less than 3 minutes, especially less than 1 minute.

In some (preferred) embodiments, the first material may be formed by reaction of a first precursor and a second precursor. In this case, said first and second precursors, which may be intimately mixed, may be contacted with said second material, for example in said first mould. In this case, after moulding of said second *** material, said first and second precursors may be IS..

introduced into the first mould and contacted with the S...

*..: second material. The first and second precursors may be caused to cure to define said first material, suitably by * the latent heat contained in said second material. * . * S.. S. S. * *.

In an alternative, less preferred embodiment, said second material may be rnoulded in a first mould. Contact of said second polymeric material with said first polymeric material (or one or more precursors thereof) may take place in a second mould. In this case, moulded second polymeric material may be transferred from said first mould to a second mould prior to contact with said first material (or one or more precursors thereof) . Any such transfer is suitably effected so that when the moulded second polymeric material is in said second mould and is contacted with said first polymeric material (or one or more precursors thereof) it contains sufficient latent heat and/or is at a sufficient temperature as described herein to effect curing of said first polymeric material (or one or more precursors thereof) In the method, said second material is preferably over-moulded with said first material.

After the first material (or one or more precursors thereof) has/have been intimately contacted with said second material, the combination may be allowed to cool, suitably passively, to ambient temperature. Thereafter, the combination of first and second materials may be removed from the mould.

*:. Said first material (or one or more precursors thereof) *. . is/are suitably curable at a temperature in the range 100 **s.

to 250°C, preferably 150 to 250°C, more preferably 160 to *S*.

220°C, especially 170 to 210°C. Preferably, said first materials (or one or more precursors thereof) is/are subjected to a temperature in said ranges in the method. *

S * S.

S

Immediately prior to introduction into a mould to contact said second polymeric material, said first polymeric material (or one or more precursors thereof) may be at a temperature of less than 100°C, preferably less than 75°C, more preferably less than 50°C, especially less than 35°C.

Said first polymeric material (or one or more precursors thereof) may be at ambient temperature prior to said

introduction.

Said first material preferably comprises a silicone rubber. Such a silicone rubber may have methyl and/or vinyl substitutions on the polymer chain. Said first polymeric material (or one or more precursors thereof) is/are preferably flowable at a temperature of less than 50°C, more preferably less than 30°C.

Suitably, said first material (or one or more precursors thereof) is/are arranged to cure in less than 1 minute, preferably in less than 50 seconds, more preferably in less than 40 seconds, especially in less than 30 seconds, after contact with said second polymeric material.

Preferably, said first polymeric material need not be subjected to post-curing.

Said first polymeric material (or one or more precursors thereof) preferably comprise(s) a liquid silicone rubber.

*:, Such a rubber may be formed from first and second *.

components which may be introduced into a mould (suitably at a weight ratio of first to second components in the ***.

*..: range 0.3 to 3, preferably 0.75 to 1.3) in which said second polymeric material is arranged. The components may :. then cure as they are heated to the curing temperature by * **. S. * ** * *.

transfer of latent heat from said second polymeric material. The curing process may involve a hydrosilylation reaction.

The implantable prosthesis of the second aspect may have any feature of the Jmplantable prosthesis of the first aspect.

According to a third aspect of the invention, there is provided a method of implanting an implantable prosthesis according to the first aspect, the method comprising preparing a human or animal body to receive the prosthesis; and arranging the prosthesis in position in the body.

According to a fourth aspect of the invention, there is provided the use of an implantable prosthesis of the first aspect for replacing or supplementing a part of a human or animal body.

Said implantable prosthesis may be a finger joint.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.

*:. Specific embodiments of the invention will now be

S

described, by way of example, with reference to the * S..

accompanying drawings, in which: S... *SS. S.. * . *S. *. . S * * S *.

Figure 1 is a partial cross-section of a human hand which includes a prosthetic finger joint as described in 0S4 158893; Figures 2 and 3 are perspective views of a first and second prosthetic finger joints respectively; Figures 4 to 8 are perspective views, partly in cross-section, of third to seventh prosthetic finger joints respectively; Figure 9 shows an anatomically shaped implant; Figure 10 shows an implant which includes a spherical hinge; Figure lla shows a hinge arrangement having two narrow stems; and figure lib shows the stems in perspective view; Figure 12 shows craniomaxilliofacial implant; Figure 13 shows a further finger joint implant.

The following material is referred to hereinafter PEEK-OPTIMA (Trade Mark) -polyetheretherketone obtained from Invibio Ltd, UK. Grades LT1 or LT3 may be selected according to the particular application. * * * * *. .

In the figures, the same or similar parts are annotated *.S.

with the same reference numerals. ***. * *..*

Figures 2 to 13 show various different designs of figure :. joints, each of which may be implanted in the manner * **. S. * S *

described generally in tJS4l58893. Advantageously, however, each joint can be implanted as a single piece into intermedullary canals without the need to initially locate separate sleeves in the canals.

Referring to figure 2, the finger joint 18 comprises a body 20 made of silicone rubber which defines stem portions 12, 14 and hinge portion 22. Regions 24, 26 of the body 20 on opposing sides of hinge 22 are over-moulded with a sleeve made from PEEK-OPTIMA. With this design, the joint 18 can readily pivot about hinge 22, but the body 20 is protected in regions 24, 26, which are susceptible to damage and/or premature failure, by the PEEK-OPTIMA which is a significantly harder wearing material compared to the silicone rubber of body 20.

Since the joint is formed in one piece, it can readily be implanted.

Referring to figure 3, the finger joint 26 includes a body 28 made of silicone rubber which defines stem portions 12, 14 and hinge portion 22. However, except for the hinge portion 22, the body 28 is over-moulded with PEEK-OPTIMA.

With this design, the joint 18 can readily pivot and the entire body 20 (except in the region of the hinge) is protected from damage and/or premature failure. In a variation on the aforesaid, the stem portions 12, 14 could comprise solid PEEK-OPTIMA parts. * * * S.

Referring to figure 4, a finger joint 30 comprises a S...

reinforcing member 32 made from PEEK-OPTIMA which is *...

encapsulated in silicone rubber which defines stem portions 12, 14 and hinge portion 22. The member 32 includes a thin central stem 34 which is sufficiently thin *S. * * S * * *

and flexible to pivot when acting as a finger joint.

Bulbous heads 36 are connected to the stem 34 and are positioned adjacent the hinge to reinforce the finger joint 30 in regions of it which are particularly susceptible to damage and/or premature failure in use.

Referring to figure 5, a finger joint 38 comprises a reinforcing member 40 made from PEEK-OPTIMA which is encapsulated in silicone rubber as described for the figure 4 embodiment. The member 40 is generally cylindrical in shape with a hollow weakened portion 42 being positioned centrally adjacent a hinge portion 22 and being arranged to be sufficiently flexible to pivot in use. Ends 44 of the member 40 are positioned adjacent the hinge portion to reinforce the finger joint in regions particularly susceptible to damage and/or premature failure.

Referring to figure 6, a finger joint 46 includes spaced apart reinforcement members 48, 50 made from PEEK-OPTIMA which are encapsulated in silicone rubber 52. A space between ends of members 48, 50 defines a flexible hinge region 54. The members 48, 50 include bulbous heads 56 and tapered stems 58 provide significant reinforcement for the finger joint, particularly in the region adjacent the hinge region 54.

Referring to figure 7, a finger joint 60 includes spaced

S

apart solid reinforcement members 62, 64 made from PEEK-**..

OPTIMA which are encapsulated in silicone rubber 52. The ***.

members 62, 64 reinforce the joint 60 particularly in regions particularly susceptible to damage and/or premature failure. * S * S.. S. * * S5 S.

Figure 8 shows a finger joint which comprises elongate stem portions 70, 72 and hinge portion 74. Each stem includes a reinforcing member 76 (the reinforcing member within stem portion 72 has been omitted from the figure) made from PEEK-OPTIMA and comprising an elongate stem 78 and a curved head member 79. The reinforcing member 76 is overmoulded with a silicone member.

Finger joints (or other implants) may be anatomically shaped as shown in figure 9 wherein a silicone rubber body which defines a hinge region 80 is over-moulded with PEEK-OPTIMA regions 82 in a manner analogous to the figure 3 embodiment.

Referring to figure 10, a joint may include a spherical hinge 86 which may be bounded by stems 83, 85 which may be as described for the stems shown in the other figures.

Referring to figure ha and lib a finger joint 90 comprises two thin stems 92 attached to heads 94 and spaced apart by a silicone rubber hinge region 96.

Referring to figure 12, craniomaxihlofacial implant 100 may be made comprising a silicone hinge region and PEEK-OPTIMA regions to provide rigidity. The implant may include a PEEK-OPTIMA insert overmoulded with silicone rubber; or a silicone part may have its rigidity increased by co-moulding with PEEK-OPTIMA.

*..: Figure 13 includes hollow stems 120 made from PEEK-OPTIMA into which a silicone rubber central region 122 is moulded S. * . * *S. S. * *.

S

so that male elements 124 thereof (only one of which is shown in the figure) are received within the hollow stem.

Many of the aforementioned embodiments show silicone parts and PEEK-OPTIMA parts in intimate contact. The parts are suitably produced by means other than by application of an adhesive to cause the silicone and PEEK-OPTIMA to adhere.

Advantageously, parts may be produced by over-moulding or co-moulding either to form a PEEK-OPTIMA layer over a silicone base; or to form a silicone layer over a PEEK-OPTIMA base or component.

One embodiment for forming a silicone layer or part over a PEEK-OPTIMA part may be as follows: PEEK-OPTIMA is injection moulded in a first mould. The PEEK is injected at 400°C into the cavity of the injection moulding machine which is at a temperature in the range 160°C to 190°C. Consequently the PEEK contains a substantial about of heat energy. After some cooling of the PEEK, a liquid silicone rubber (LSR) may be injection moulded onto the PEEK in predetermined positions, without removal of the PEEK moulding from its mould. Provided the LSR is contacted with the PEEK when the PEEK is still at a high temperature (e.g. 180°C) the latent heat in the PEEK is sufficient to rapidly cure the LSR and, accordingly, additional heating of the LSR in the mould is not required.

U

S *1

In an alternative embodiment, the injection moulded PEEK * of the first embodiment may be removed from the mould whilst it is still hot (greater than 200°C) and placed in a second mould. Thereafter, LSR is injected into the * S. S * * second mould to contact the PEEK, which is still at a relatively high temperature (e.g. 180°C) and consequently the latent heat in the PEEK is sufficient to cure the LSR as before.

Silicone rubbers for uses described herein are suitably medical grade liquid silicone rubbers suitable for injection moulding such as ELASOSIL (Trade Mark), SILIBIONE (Trade Mark) or SILASTIC (Trade Mark) Alternatively, rigid silicone elastomers such as BIOPLEXUS, MEDISI or NUSIL could be used. Characteristics of commercially available materials are summarised below: Test Grade/Source Dow E Funda Nusil Nusil method Corning Website MED MED ASTM S70 4805 4880 D2240 Durometer 66 20-70 7 80 (Shore A) D412 Tensile 9.3 6-10 3.6 6.6 Strength MPa 0412 Elongation % 418 300-1000 1100 250 D624 Tear Strength 42.3 Not 10.6 15.9 kN/m Stated As an alternative to use of PEEK-OPTIMA other thermoplastics may be used as may blends of polymeric materials. Polyaryletherketones are preferred thermoplastics materials. *. . *.S.

When an implant includes an outer layer of PEEK-OPTIMA, the material may be coated with hydroxyapatite or titanium to encourage bone integration. Additionally, PEEK-OPTIMA * S.. S. *

S

may be arranged to be smooth or textured in order to provide good fixation to silicone and/or to provide low wear against cartilage if desired.

As an alternative to the aforesaid embodiments modifications may be made to define other implants for small joints, such as toe implants or for reinforcement/resurfacing of a trapezium prosthesis.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. ***s * . . I. * *IS. S * SI.. S...

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S S. S..

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Claims

Claims 1. An implantable prosthesis for implantation in a human or animal body, the prosthesis comprising a first material and a second material which are integrally formed with each other.
2. A prosthesis according to claim 1, wherein said first and second materials are co-moulded.
3. A prosthesis according to claim 1 or claim 2, wherein said prosthesis is articulated and includes an intermediate region arranged between first and second regions, wherein the intermediate region defines a joint which is arranged to replace a joint of a human or animal body into which the prosthesis may be implanted in use.
4. A prosthesis according to any preceding claim, wherein said prosthesis includes a first part which comprises said first material, wherein a layer comprising said second material overlies said first material and is in intimate contact therewith; or said prosthesis includes a first part which comprises said first material wherein a reinforcing means which comprises said second material is embedded in said first material; or said prosthesis includes a first part which comprises said first material *..S wherein said first part is flexible and defines a joint of the prosthesis, a second part being provided on one side of said first part which comprises said second material *.S.and a third part being provided on an opposite side of *..said first part which comprises said second material, said second and third parts making face to face contact with *. : said first part.
5. A prosthesis according to any preceding claim, wherein said prosthesis is a craniomaxillofacial implant or a finger joint.
6. A prosthesis according to claim 5, wherein said prosthesis is a finger joint and comprises a first region which is arranged to pivot relative to a second region, an intermediate region being defined between the first and second regions, wherein said first and second regions define elongate stems, ends of which are arranged to be inserted into openings defined in a human or animal body in which the prosthesis is to be implanted in use, wherein the elongate stems taper inwardly towards their free end, and said intermediate region is wider than said stems.
7. A prosthesis according to any preceding claim, wherein said prosthesis includes a first body which comprises said first material, wherein said first body defines said first and second regions and said intermediate regions and wherein said second material encapsulates at least part of each of said first and second regions.
8. A prosthesis according to any of claims 1 to 6, wherein a reinforcing means which comprises said second material is embedded in the first material so that it is *S.S * S positioned within first and second regions of the * S..prosthesis. *. S.S *5S*
9. A prosthesis according to any preceding claim, wherein S..said first material comprises an elastomer having a Shore A hardness (ASTM, D2240) of at least 5 and of less than 55. * ** S.
10. A prosthesis according to any preceding claim, wherein said first material comprises a silicone elastomer.
11. A prosthesis according to any preceding claim, wherein said second material comprises a polymeric material which includes a repeat unit of general formula -f f-E -f Ar)-(-J-)_ E4-(-f'a_ -fJ)_ G C or a repeat unit of general formula or a repeat unit of general formula 4f53}.. Gf1)_-co-16J-J-)__-f-E -fAr-(-1aJ-)---)A] or a repeat unit of general formula * * * ** * *I.. * S *S.. )]wherein A, B, C and D independently represent 0 or 1, E and E' independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a -O-Ph-O-moiety where Ph represents a phenyl group, m, r, s, t, v, w, and z represent zero or 1 and Ar is selected from one of the following moieties (i) to (v) which is bonded via one or more of its phenyl moieties to adjacent moieties -CH3 -CH3 (ii) (iii) (iv) Q Q :.*::. 10 (v)S*
12. A prosthesis according to claim 11, wherein said polymeric material comprises a repeat unit of formula S. * a * S.. S. * * SI

IIwhere ti and wi independently represent 0 or 1 and vi represents 0, 1 or 2.
13. A prosthesis according to claim 11 or claim 12, wherein said polymeric material is polyetheretherketone.
14. A prosthesis according to any preceding claim, wherein the sum of the wt% of said first and second materials is at least 95wt% of the weight of the prosthesis.
15. A prosthesis according to any preceding claim, said prosthesis being a moulded part.
16. A method of making an implantable prosthesis, the method comprising co-moulding a first material and a second material to define at least part of said prosthesis.
17. A method according to claim 16, the method comprising moulding a first part of the prosthesis from said first or second material and then co-moulding the other one of said first or said second material to define a second part of the prosthesis. * * * S. * *S*s S * *S..
18. A method according to claim 16 to claim 17, which S...: comprisesSa) moulding the second material; ** b) contacting the second material with the first material a ** (or one or more precursors thereof) whilst the second material is at a temperature of greater than 100°C and/or whilst the second material is at a sufficiently high temperature that it retains sufficient latent heat to cure the first material (or one or more precursors), whereby the temperature of the first material aids curing of the first material.
19. A method according to any of claims 16 to 18, wherein the prosthesis has any feature of the prosthesis of any of claims 1 to 15.
20. A method of implanting an implantable prosthesis according to any of claims 1 to 15, the method comprising preparing a human or animal body to receive the prosthesis; and arranging the prosthesis in position in the body.
21. The use of an implaritable prosthesis according to any of claims 1 to 15 for replacing or supplementing a part of a human or animal body.
22. A use according to claim 21, wherein said prosthesis is a finger joint. **.. * * * ** * **** S * *S.. **S.S 55.S *S.S ** * * * .5S ** S * * * **