3,906,550
`1111
`1191
`United States Patent
`
`Rostoker et al. 1451 Sept. 23, 1975
`
`[76]
`
`[54] PROSTHETIC DEVICE HAVING A POROUS
`FIBER METAL STRUCTURE
`Inventors: William Rostoker, 2052 w. 108th
`P1,, Chicago, 111. 60643; Jorge
`Galante, One Brighton Ln.,
`Oakbrook, 111. 60521
`
`[22]
`
`Filed:
`
`Dec. 27, 1973
`
`[21] Appl. N0.: 428,763
`
`[52] U'S' C112892C12852/1E9C1'2323/1109A'323/119;
`51
`I
`t Cl 2
`/
`’
`/A61F 1' 24/_ A61C 1/3433
`£55 F'ieid oi‘ sééréii """"""
`/ 3;]
`1 9 1 9/13.
`128/92 C, 92 CA, 92 BC, 92 R; 32/10 A
`
`[56]
`
`References Cited
`UNITED STATES PATENTS
`4/1964
`Troy """""""""""""""""" 128/92 C UX
`$13368
`
`3:33:
`£203,231"""""""""12.82.92.842
`329033:
`’
`’
`‘ """""""""""""
`FOREIGN PATENTS 0R APPLICATIONS
`1,042,834
`11/1958 Germany ........................... 128/92 C
`OTHER PUBLICATIONS
`
`tachment of Implants to Bone." by J. Galante et 111..
`The Journal ofBane and Joint Surgery, Vol. 53—A, No.
`1’ January 1971’ pp' 101‘] 14’ Ma“ 1'
`
`Primary Examiner-Ronald L. Frinks
`Attorney, Agent. or Firm—Albert Siegel
`
`[57]
`
`.
`ABSTRACT
`
`Prosthetic devices for replacement, attachment and
`reconstruction of bone structure in the skeletal sys-
`tems of humans and animals. The prosthetic devices
`may be a fiber metal structure of sufficient section to
`support loads adequately or may include a solid load
`carrying member having a fiber metal structure se-
`cured to the surface thereof. The fiber metal structure
`is sintered and open-pored so that the bone and tissue
`into which the prosthetic device is implanted will grow
`into such fiber metal structure.
`the
`To provide the proper interlock between fibers.
`individual fiber strands are prekinked prior to cutting
`into the desired length. The kink pattern should be
`substantially sinusoidal. Preferably such kink pattern
`should have
`an amplitude
`(H)
`to period (W)
`relationsh1p, H/W of 0.24 or greater.
`
`“Sintered Fiber Metal Composites as a Basis for At-
`
`10 Claims, 6 Drawing Figures
`
`
`
`30
`
`Page 1 of 6
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`ZIMMER EXHIBIT 1010
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`ZIMMER EXHIBIT 1010
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`Page 1 of 6
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`

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`

`

`US Patent
`
`Sept. 23,1975
`
`Sheet 2
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`0f2
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`399%9559
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`’
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`Page 3 of 6
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`Page 3 of 6
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`

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`1
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`35,906,550
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`2
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`PROSTHETIC DEVICE HAVING A POROUS FIBER
`'
`METAL STRUCTURE
`,
`There is reserved to the government of the United,
`Statesof America a non-exclusive, irrevocable and roy—
`alty-free license to make and use, and to sell as: pro—
`vided by law, embodiments of the invention. as herein-
`after described and claims, with the power to sub—
`license for all governmental purposes.
`
`10
`
`_
`
`.15
`
`.20 :
`
`BACKGROUND OF THE INVENTION
`This invention relates to prosthetic devices forre-
`placement reconstruction and attachment1nthe skelc-
`tal system of humans and animals, and.more particu-
`larly1s directed to a prosthetic device including a po-
`rous fiber metal structure.
`Prosthetic devices are used to partially or completely
`replace joints or bone segments in the skeletal structure
`of humans or animals. One of the major problems in—
`volved in the use of prostheticdevicesis the attach—
`ment of the prosthetic implant, to the adjacent bone.
`There are four principal methods by which the device.
`~ can be attached to the bone. These methods include:
`(1). lmpaction of the prosthetic stem into. the medul-
`lary cavity of the bone; (2). Mechanical internalfixa-
`tion, e.g.,,screWs; (3). Methyl methacrylatepolymeriz» '
`ing “in situ” used as a cement or. filler between the
`prosthesis and the bone; and (4,). Porous materials into _
`which the bone can grew. Each of these methods pres-
`ents problems that can cause .failure of the prosthetic
`implant.
`The devices which are impacted into the medullary
`cavity are heldIn place by a compressive residualstress
`interaction which may be more commonly—referredto
`as a force fit. If this stress interaction is relaxed in the
`surrounding bone, due to physicalor .biological pro-
`cesses, the attachment is lost and the device becomes
`loose, thereby requiring surgical removal and refitting
`of the prosthesis.
`-
`.
`_
`1
`Mechanical
`internal
`fixation produces acceptable
`limited term attachments. ,However in long term use
`the device may become loose and thereby require re-
`placement...
`.
`Polymethyl methaerylate has also produced accept-
`able limited term attachments. However, doubtsstill
`exist as to the overallrsafety of itsuse from a biological
`point of view partly from damage to surrounding tissue
`from monomer and heat interaction, and partly that the
`plastics may age in the body fluid thereby becoming
`brittle and tending to crack or crumble.
`50
`An open-pore material into which bone could grow ,
`should provide ideal skeletal fixation. Numerous mate-
`rials and processes for producing porous aggregates
`have been disclosed which serve- this purpose. Fer ex-
`ample, see U S. Pat. No. 3,314,420. Typically these ag—
`gregates are powder metals or powder ceramics Which
`are compressed and sintered to produce a porous but
`relatively strong body. In order to obtain the high level
`of porosity and acceptable greenestrength; rather fine
`powders are required,"the use ofirwhidhg'substantially
`limits the size of theip‘oreeruri’n‘g sintering ‘much of
`the porosity ceases tobecome interCOnnecting and thus
`a high proportion of the pores at the sdrfa’ce bécbme
`isolated from the interior of the body. This isolation
`limits bone ingrowthand results1n a situation similar to
`the roughened surface of a solid. Furthermore, theme-
`chanical properties of sintered powders are not ideal;
`for example, porous consolidated ceramicsare Very
`
`weak and brittle,
`.and;, cracks propagate 5' quickly
`throughout the whole body of the porous aggregate at
`low stresses or with smallimpact energies. Consoli-
`dated metal powders with porosities in the range of
`40—60% void are stronger than the consolidated ce-
`ramics but still are very brittle and have poor tough-
`ness. Moreover, sintered metal powders are susceptible
`to fatigue failure Both sintered ceramics and metal
`powders have compliances which more closely approx-
`imate the pore free material. ComplianceIS defined as
`.the change1n elasticstrain per unit change1n stress.
`.lThe subject invention, provides a‘prosthetic device
`which is non-toxic, compatible and‘ not subject to loos-
`ening or movement after implantation, and furtherin-
`cludes the provision of an open-pore attachment for
`bone ingrowth which attachment is highly compliant
`not brittle, resistant to crack propagation and has a
`broad range of readily controllable pore sizes.
`SUMMARY OF THE INVENTION
`There15 provided by this invention a prosthetic dc-
`' vice including a porous aggregate produced by molding
`and sintering short metal fibers. The sintering process
`creates metallurgical bonds at the points of contact of
`the fibers. Thus, the fiber metal aggregate has consider-
`able mechanical strength due to mechanical interlock
`of the fibers and the sintered bonds.
`The degree of mechanical interlock and mechanical
`strength of the porous aggregate is appreciably im-
`proved if the wire is kinked prior to being cut into the
`short metal fibers The kinking pattern should be sinu-
`soidal. Preferably,,the ratio of amplitude and period of
`the sine wave should be 0.24 or greater. After the kink-
`ing is formed, the wire is cut into the desired lengths:
`By using fiber metals the range. of pore sizes can bc
`‘ readily controlled and the attachment is not subject to
`the crack propagation and low strength problems asso-
`' ciated with ceramics or powdered metal attachments.
`and. provides a highly compliant non-brittle connec—
`tion. Moreover in view of the use of fiber metals the
`poresareinterconnecting and remain so after sintering.
`Thus bone growth can penetrate for a substantial dis—
`tance into the fiber metal structure and thereby provide
`a very secure connection. By the appropriate selection
`of the fiber metal composition“ an essentiallyincrt at-
`tachment can be achieved; hence, the fiber metal at-
`tachment is not subject to the aging problems or reac-.
`tion problems of the plastics of the prior art. Since the
`pore size can; be readily controlled by the pressing and
`forming parameters, the density of the sintered com-
`posite can approximate the density of the bone to
`which the prosthetic device is implanted.
`BRIEF DESCRIPTION OF THE DRAWINGS
`Referring to the drawings1n .which the same charac-
`ters of reference are employed to indicate correspond-
`ing similar parts throughout the several figures of the
`:drawings:
`60.’ . FIG..1 is a vertical sectional view illustrating an ex-
`emplary hip joint prosthesis;
`,
`,
`FIG 2IS a stress-strain diagram for a molded and sin-
`tered Co-Cr-W alloy fiber aggregate
`FIG. 3 illustrates a sinusoidal kinking pattern of a
`65
`' wire length prior to being cut into the fiber strands used
`in the fiber metal structure of FIG 1;
`‘
`FIG 4 illustrates an enlargement of a portion of a
`_. molded fiber metal structure;
`
`30
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`35
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`3
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`3,906,550
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`4
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`FIG. 5 is a vertical sectional View depicting a femur
`having a bone segment reconstruction prosthesis; and
`FIG. 6 is a vertical view of a mountingfor a dental
`prosthesis.
`'
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`1 of the drawings. the refer-
`Referring now to FIG.
`ence numeral 10 indicates generally a hip joint prosthe-
`sis which is exemplary of the prosthetic devices em-
`bodying the principles of the subject invention. The
`joint prosthesis 10 comprises two individual prosthesis.
`a femur prosthesis 12 and a acetabulum prosthesis 14.
`The femur prosthesis 12 comprises a load carrying
`means 16 of solid construction and a sintered fiber
`
`metal attachment structure indicated generally by the
`reference numeral 18.
`
`The solid load carrying means 16 includes a ball 20
`carried on a flange 22, which in turn is mounted to a
`rod 24 having a cup-shaped bottom end member 26.
`The fiber metal attachment structure 18 includes a plu—
`rality‘ of tubular fiber metal segments 28a. 28b. 28c.
`28d. and 28a.
`f
`The rod 24 and segments 281! through 286 are in-
`serted into the medullary cavity of the femur 30 which
`is appropriately reamed and is thus fixed in place so
`that the ball 20 is properly orientated with respect to
`the hip socket 32. As the healing process takes place.
`the bone which is adjacent the fiber metal segments
`28a through 286 grows into the attachment 18. It has
`been observed that after the bone ingrowth has pro—
`ceeded to a substantial degree, a seCure fixation is pro—
`duced between the ingrown bone and the fiber metal
`implant.
`The attachment segments 2811 through 286 can be se-
`cured to the rod 24 in a number of ways. The most ef-
`fective way is to metallurgically bond the fibers con—
`tacting the surface of the rod thereto; however. it will
`be appreciated that the flange 22 and end member 26
`when tightened also act to hold the attachment seg-
`ments 28 in place. Other methods by which the seg-
`ments 28 are mounted to the rod 24, include cementing
`or the like or mechnical fixation; however. as indicated
`above metallurgical attachment is preferred.
`The solid load carrying rod 24 or a similar member
`is normally used when tension and bending loads may
`be anticipated. However. where only compressive loads
`are experienced. the fiber metal structure 18 may be
`used without such rod 24. However. in some situations
`where stresses and strains are realized. a fiber metal
`structure of substantial area may be used without the
`rod 24.
`.
`_
`The acetabulum prosthesis 14 includes fiber metal
`attachment component 34 and a solid wear insert 36.
`The fiber metal attachment is molded into the proper
`shape and then fitted into a cavity formed in the ace-
`tabulum during surgery. Bone ingrowth'will hold the
`fiber component 34 rigidly in place. Since a fiber metal.
`surface is probably not particularly wear resistant. the
`wear insert 36 is molded integral with the fiber compo—
`nent 34. Furthermore. the insert 36 not subject to bone
`ingrowth can be held in place mechanically so that it
`can be subsequently removed and replaced if neces—
`sary.
`‘
`In another prosthetic system. a union may be accom-
`plished between the upper and lower portions 38 and
`40 ofa severed femur 30 generally as shown in FIG. 5.
`
`U]
`
`10
`
`Id ’.JI
`
`40
`
`As is seen, the severance space 41 is filled with a cylin-
`drical sintered fiber metal member 42 having a center
`core hole 44 through which a sintered fiber-sleeved
`shaft 46 is passed. to provide fixation to the extremities '
`of the femur 30. The shaft 46'includes a solid center
`member 48, sintered fiber metal sleeves 50a, 50b. 50(‘,
`50¢! and 506, and end members 52 and 54. Shaft 46 is
`fitted into the medullary cavity 56 of the femur 30
`which is appropriately reamed.
`In still another prosthetic application, a device 58, as
`shown in FIG. 6, may be implanted in the jawbones 60
`of humans or animals as a, basis for mounting artificial
`teeth or dentures. The dental prosthesis 58 comprises
`a monolithic sintered fiber metal member 62, and a
`solid center shaft 64 passing centrally through the fiber
`member 62. Shaft 64 includes a flanged bottom 65.
`When bone or tissue grows into the fiber member 62,
`the upper end of the shaft 40 is securely held in place
`and an artificial tooth 66 can then be mounted thereon.
`
`The ingrowth of gingival
`seal.
`
`tissue provides a bacterial
`
`The fiber metal segments 28, and the fiber metal at-
`tachment component 34 shown in FIG. 1, and the fiber
`metal member 42 and sleeves 50 shown in FIG. 5, and
`the fiber metal member 62 shown in FIG. 6 are all po-
`rous aggregates produced by molding and sintering
`short metal fibers. The points of contact between fibers
`become metallurgical bonded during sintering. Thus,
`the fiber metal aggregate has considerable mechanical
`strength due to the sintered bonds and the mechanical
`interlocks.
`
`Short lengths of fine wire such as stainless steel, unal—
`loyed titanium or Co-Cr-W alloy. are mechanically
`molded into the desired precise shapes using constrain-
`ing dies and moving punches. When loading the wire
`charge of short metal fibers in the die during molding,
`the long axes thereof. should be on the most part coax-
`ial with the punch motion. Upon applying the proper
`pressure with
`the
`dies
`and punches.
`at
`three-
`dimensional mechanically interlocked network of fi-
`bers is formed.
`L
`The degree of interlock and unsintered or ‘green“
`strength of a pressing with the dies. is substantially in-
`creased if the original wire is prekinked prior to cutting
`the wire into the short fibers. The desired kinking can ‘
`be accomplished by passing the wire through a set of
`meshing gears.
`It has been found that the wire should be prekinked
`into a sinusoidal pattern to provide the greatest me—
`chanical interlock. as shown in FIG. 3. Thereafter, the
`kinked sinusoidal wire is cut into the desired short fiber
`lengths.
`To provide the optimum interlock the kink pattern
`should have an amplitude (H) to period relationship
`(W). H/W of 0.24 or greater.
`'
`The kinked short fiber strands of 316 L stainless
`
`6t)
`
`steel; unalloyed titanium and Co-Cr-W‘alloy wire. are
`molded into the precise shape for the fiber metal aggre-
`gate as aforestated. using constraining dies and moving
`punches. The choice of the wire size and the density of
`the fiber strands loaded in the dies will govern the final
`parameter dimensions of the fiber metal aggregate.
`The molding operation is followed by a sintering
`stage in which points of contact become actual metal-
`lurgical bonds. Adequate bonding has been obtained
`with oven temperatures within the range of [070° —
`1240° C for approximately 2 hours.
`
`Page 5 of 6
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`3,906,550
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`Repressing, using the same die and punch tooling, of
`the sintered metal fiber aggregate must be done to en-
`able the aggregate to be formed into precise and repro-
`dueible dimensions which are necessary fer good clini—
`cal responses.
`The sintered fiber metal aggregates shown in FIGS.
`1, 5 and 6 may be molded having void or a porosity of
`40 to 50 percent per unit area. A porosity of 60% could
`also be achieved, but the green strength is generally too
`fragile, and therefore, could effect
`the dimensional
`control because of elastic recovery. Also fiber metal
`aggregate having such greater porosities are not suffi-
`ciently firm at the edges and tend to crumble.
`Wire sizes as fine as 0.013 centimeters in diameter
`and as coarse as 0.030 centimeters in diameter have
`been satisfactorily molded. In the molded and sintered
`fiber metal aggregate, the metal fibers are completely
`interconnected. The pore shapes as may be seen from
`FIG. 4, which is a magnification of a portion of a sin-
`tered-molded fiber metal aggregate, cannot be de-
`scribed in any simple geometric shape. The largest
`. principal dimension of the pores is approximately equal
`to the wire diameter when the void content is about 50
`percent. However, pressing or molding to higher densi-
`ties would lead to more constricted pore sizes.
`Wire is cut to lengths ranging from 1.3 to 3.8 centi—
`meters. The longer the wire, the more difficult it is to
`feed into dies. On the other hand, long wire lengths give
`more interlock and better molded strengths.
`Turning now to FIG. 2, a graphical representation of
`a reversible (elastic) stress strain cycle is shown for Co—
`Cr-W alloy wire of 0.023 centimeters in diameter,
`molded to 50 percent porosity and sintered at 1240° C
`for 3 hours. Before testing and obtaining the data for
`FIG. 2, the sintered specimen was recompressed to a
`7% reduction in height.
`The elastic properties of Co-Cr-W alloy and other
`metal of the same class, such as stainless steel and tita—
`nium have elastic properties more like an elastomer
`than a metal. A sintered specimen shows a'purely plas-
`tic strain range of about 3—10 percent on the applica-
`tion of very small loads. Thereafter, there is an elastic
`strain range of about 3 percent in which the modulus
`is a continuous function of strain (FIG. 2). For the
`strain range of about 1 percent, the modulus is about
`10*kg/cm2 for the sintered fiber metal structure.
`The sintered porous fiber metal structure disclosed
`herein has an elastic modulus substantially less than the
`elastic modulus for porous metals produced by sintered
`powders. This enables the sintered porous fiber metal
`structure to be an effective interface between bone tis-
`sue and a load-bearing prosthesis; and it further pro-
`vides a very high compliance (large strains per unit ap-
`plied stress), which is a safeguard against high localized
`stresses at the prothesis—tissue interface.
`By repressing procedures the external dimensions of
`prostheses may be precisely regulated to the excavation
`so that a zero clearance fit exists. The zero clearance
`fit is vital to the clinical success of fixation by bone and
`soft tissue. In the absence of a zero clearance fit, the
`
`40
`
`45
`
`50
`
`55
`
`60
`
`5
`
`10
`
`15
`
`25
`
`30
`
`prothesis is isolated by fibrous or non-functional tissue.
`For a tooth root prosthesis this leads to loosening.
`Other porous materials cannot easily be sized to precise
`dimensions.
`
`The foregoing specification and description are in—
`tended as illustrative of the invention,
`the scope of
`which is defined in the following claims.
`We claim:
`
`1. A prosthetic device for incorporation into the skel-
`etal structure of a human or animal inciuding:
`a porous fiber metal structure formed from a plural-
`ity of substantially,
`sinusoidally shaped fiber
`strands, each of said fibers having a ratio of ampli—
`tude to period of substantially 0.24 or greater, said
`strands being metallurgicalfly bonded to each other
`at their points of contact, said fiber metal structure
`providing at least a portion of the surface of said
`prosthetic device adjacent said skeletal structure to
`enable bone and soft tissue growth into said metal
`structure, said period being substantially the length
`of a cycle of said sinusoidal fiber strand and said
`amplitude being substantially the height/2 between
`a positive peak and a negative peak of said sinusoi-
`dal fiber strand.
`
`2. The prosthetic device of claim 1, wherein said
`fiber metal structure is between 10% and 70% porous.
`3. The prosthetic device of claim 1, wherein the di—
`ameter of said fiber strands is. between about 0.013
`centimeters and 0.030 centimeters.
`4. The prosthetic device of claim 1, wherein the
`length of said fiber strands is between about 1.3 centi-
`meter and 3.8 centimeters.
`
`includes a non-
`5. The prosthetic device of claim 1
`compressible rod. said fiber metal structure being sc-
`eured to the outside of said rod.
`6. The prosthetic device of claim 1, wherein said
`fiber metal structure is selected from the group consist—
`ing of titanium, Co—CrAW altoy, stainless steel, tantalum
`and zirconium.
`
`7. The prosthetic device of claim 1, includes:
`a wear resistant member, said fiber metal structure
`being mounted on said wear member, said fiber
`metal structure adapted to be in contact with said
`skeletal structure when. implanted therein.
`8. The prosthetic device of claim 5, wherein said
`fiber metal structure comprises a plurality of cylindri-
`cal segments mounted on and surrounding said rod.
`9. The prosthetic device of claim 8 further includes:
`a second porous fiber metal structure having a bore
`therein, said bore being dimensioned to receive
`said rod with said segments thereon.
`10. The prosthetic device of claim I wherein said de-
`vice is a dental prosthesis.
`including an upstanding
`mounting member mounted in said fiber metal struc-
`ture and extending outward therefrom. said fiber metal
`structure extending around said upstanding member
`for operatively contacting the jaw bone to receive the
`growth of said jaw bone and gingival soft tissue.
`*
`3k
`*
`*
`*
`
`65
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