(12) United States Patent
`Schuster et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US006510334Bl
`US 6,510,334 Bl
`Jan.21,2003
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`(10) Patent No.:
`(45) Date of Patent:
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`(54) METHOD OF PRODUCING AN
`ENDOPROSTHESIS AS A JOINT
`SUBSTITUTE FOR A KNEE JOINT
`
`(76)
`
`Inventors: Luis Schuster, Miinchen (DE);
`Christoph Schuster, Miinchen (DE)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 231 days.
`
`(21) Appl. No.: 09/712,728
`
`(22) Filed:
`
`Nov. 14, 2000
`
`Int. CI.7 .............................. A61B 6/00; A61F 2/28
`(51)
`(52) U.S. Cl .
`........................ 600/407; 600/425; 128/920
`(58) Field of Search ................................. 600/407, 410,
`600/425; 128/920; 378/901
`
`( 56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,704,686 A
`5,370,692 A
`5,677,855 A
`5,682,886 A
`5,798,924 A
`5,824,085 A
`
`* 11/1987 Aldinger ..................... 700/163
`* 12/1994 Fink et al. . ... ... .. ...... ... 128/898
`10/1997 Skeeters et al.
`11/1997 Delp et al.
`* 8/1998 Enfinger et al.
`............ 700/117
`* 10/1998 Sahay et al. .. ..... ... ... ... 128/898
`
`5,871,018 A
`
`2/1999 Delp et al.
`
`FOREIGN PATENT DOCUMENTS
`
`DE
`DE
`DE
`DE
`DE
`DE
`DE
`DE
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`3213434
`3522196
`3626549
`4304572
`4341367
`4434539 Al
`4434539 C2
`19726618
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`10/1983
`2/1986
`2/1988
`8/1994
`6/1995
`4/1996
`6/1998
`12/1998
`
`* cited by examiner
`
`Primary Examiner-Joseph Pelham
`(74) Attorney, A.gent, or Firm---Ostrolenk, Faber, Gerb &
`Soffen, LLP
`
`(57)
`
`ABSTRACT
`
`In a method of producing an endoprosthesis as an joint
`substitute for knee joints three-dimensional femoral and
`tibial components of the endoprosthesis are prepared in
`combination with three-dimensional femoral and tibial com(cid:173)
`ponents of an associated implantation aid on the basis of
`respective visual patterns that are derived from virtually
`altering a preoperative tomographic image of a damaged
`knee joint.
`
`11 Claims, 5 Drawing Sheets
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`Smith & Nephew Ex. 1008
`IPR Petition - USP 8,377,129
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`1
`METHOD OF PRODUCING AN
`ENDOPROSTHESIS AS A JOINT
`SUBSTITUTE FOR A KNEE JOINT
`
`FIELD OF TIIE INVENTION
`
`This invention relates to a method of producing an
`endoprosthesis as a joint substitute for knee joint<>. The
`invention further also relates to an operative set for carrying
`out operations on damaged knee joints utilising an endopros(cid:173)
`thesis which is produced in accordance with the method of
`this invention.
`
`BACKGROUND OF THE INVENTION
`
`s
`
`2
`tomographic image for which the contours of at least the
`femoral bone and of the tibia of the damaged knee joint are
`approximated to those of a healthy knee joint. Afterwards a
`postoperative tomographic image of the damaged knee joint
`is prepared for enabling by comparison a determination of
`the differences between the contours of at least the femoral
`bone and of the tibia of the healthy knee joint tomographic
`image and the contours of at least the femoral bone and of
`the tibia of the postoperative tomographic image of the
`10 damaged knee joint. Such a comparison therefore allows a
`subsequent preparation of a tomographic reference image
`which accordingly represents those differences. This tomo(cid:173)
`graphic reference image finally forms the basis for preparing
`at least a femoral component and a tibial component of an
`15 endoprosthesis which may be used in connection with the
`factual surgical intervention on the damaged knee joint of
`which the preoperative tomographic image has been pre(cid:173)
`pared.
`Since with this known method a tomographic reference
`image representing differences between a preoperative
`tomographic image and a postoperative tomographic image
`of the damaged knee joint is used as a basis for preparing the
`components of an endoprosthesis this method could include
`a multiple error rate in respect to the preparation of such a
`reference image as caused, e.g., by the preparation of the
`postoperative tomographic image and further by the deter(cid:173)
`mination of the differences that will exist between the
`postoperative tomographic image and the tomographic
`image of a healthy knee joint which, e.g., will be prepared
`by either manually altering the preoperative tomographic
`image or by preparing a mirror image of a healthy knee joint
`of the patient. The preparation of such a tomographic
`reference image of course also raises the computer-oriented
`assistance for the preparation of an endoprosthesis in accor(cid:173)
`dance with this known method.
`
`A surgical intervention on a knee joint is usually taken
`into consideration by the attending physician when the
`patient complains about severe pains in the knee and dis(cid:173)
`abilities as a consequence of, e.g., rheumatoid arthritis or
`other joint diseases. The surgical intervention convention- 20
`ally takes place in a plurality of steps for obtaining an
`adaption to the shape of industrially manufactured joint
`moldings. Such moldings are presented in different gradu(cid:173)
`ated sizes and with different designs for being ultimately
`fitted to surfaces of the knee joint as prepared, e.g., by using 25
`an oscillating sawing blade and mainly provided for the
`anterior femoral condyle, the distal femur, the proximal tibia
`and the patella. The surfaces are provided in such a way that
`a vertical alignment is achieved for the multiple components
`of the associated endoprosthesis in relation to an axis which 30
`is obtained, e.g., by means of a preoperative X-ray image
`and an intramedullary pin align system for the straight line
`connecting the center of the hip, the knee and the malleolus.
`An illustrative representation of such a surgical procedure is
`described, e.g., in U.S. Pat. No. 4,759,350 (incorporated by 35
`referenece) by a reference also to a specific intramedullary
`pin system.
`The implantation of such multiple knee joint endopros(cid:173)
`theses is very time consuming and often results only in an
`approximate toration of the conditions of a healthy knee 40
`joint when taking into consideration existing differences in
`the patient's growth. Complications therefore often occur
`which must be attributed to the mechanics of the implanted
`components of the endoprosthesis whereby such complica(cid:173)
`tions may lead, e.g., to an anterior knee joint pain syndrome 45
`which is caused by an incorrect gliding of the patella with a
`nonphysiological loading of the femur-patella gliding joint.
`Irritations also frequently develop, occasionally with con(cid:173)
`siderable hypertrophy of the joint mucosa and pronounced
`effusions in the knee joint as a consequence of a massive 50
`abrasion of the implanted endoprosthesis components, some
`of which may consist of polyethylene and will then lead to
`an unfavourable gliding behaviour if such abrasion becomes
`excessive. Loosening of the bone anchoring of these com(cid:173)
`ponents may also occur so that it is frequently necessary to 55
`implant a new endoprosthesis.
`For avoiding such complications as often accompanied by
`a repeated implantation of a new endoprosthesis with the
`requirement for a resection of further bone parts there has
`already been proposed by one of the present inventors a
`method as described in U.S. Pat. No. 5, 735, 277
`(incorporated by reference) according to which still prior to
`a surgical intervention on a knee joint a preoperative tomo(cid:173)
`graphic image of the damaged knee joint is prepared by
`means either of a computed tomography or by means of a 65
`nuclear spin resonance tomography. In accordance with this
`known method there is further prepared a healthy knee joint
`
`SUMMARY OF TIIE INVENTION
`
`An object of the present invention is therefore to provide
`a method of producing an endoprosthesis as a joint substitute
`for knee joints which minimises the error rate in connection
`with a surgical intervention on a damaged knee joint and
`which further optimizes the surgical intervention in respect
`of the possibility to allow a very close adaption at least of the
`femoral and tibial components of an endoprosthesis to the
`contours of the bone joints as specifically prepared on
`respective surfaces during a surgical intervention for snugly
`fitting thereto the components of the endoprosthesis.
`A further object of the present invention relates to the
`provision of an operative set for carrying out operations on
`damaged knee joints which will allow a practically ready(cid:173)
`made surgical intervention on a damaged knee joint as
`accompanied with less pain for the patient.
`
`DESCRIPTION OF TIIE INVENTION
`
`In accordance with a preferred embodiment of the present
`invention a method of producing an endoprosthesis as a joint
`substitute for knee joints is started by preparing a preopera(cid:173)
`tive tomographic image of the damaged knee joint. The
`60 tomographic image could be prepared either by a computed
`tomography or by a nuclear spin resonance tomography
`which allows to define very sharp contours of the damaged
`knee joint as a correspondingly optimal precondition for all
`of the subsequent steps of this method.
`The tomographic image of the damaged knee joint is then
`virtually altered for approximating the contours of at least
`the femoral bone and of the tibia of the damaged knee joint
`
`-7-
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`US 6,510,334 Bl
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`4
`templates and therefore also their corresponding implanta(cid:173)
`tion aids, e.g., in the form of caps for obtaining an envel(cid:173)
`oping of the severing areas which therefore identify negative
`imacres of the resection areas as provided by the sawing
`s blade on the associated joint bones.
`The visual patterns of both the femoral and tibial com(cid:173)
`ponents of the endoprosthesis and the femoral and tibial
`components of the associated implantation aid are then used
`for preparing corresponding three-dimensional parts. Such a
`10 conversion could be exemplified by means of the so-called
`"Rapid Prototyping" (incorporated by reference) accord~ng
`to which there are obtained so-called STL patterns which
`may be used for the preparation of the three-dimensional
`components as mouldings in a casting process. The tibial
`15 component of the endoprosthesis could be produced as a
`metallic part for being arranged on its associated joint bone
`and further of a separate plastic part which \\rill receive an
`arrangement between this metallic part of the tibial compo(cid:173)
`nent and an also metallic part defining the femoral compo-
`20 nent of the endoprosthesis. The same "Rapid Prototyping"
`may also be used for the preparation of corresponding STL
`patterns made, e.g., of epoxy resin and provided with those
`guiding slots at the marked severing areas which have been
`virtually transferred during the preceding step.
`When an attending physician is held to consider a surgical
`intervention on a damaged knee joint the physician could
`then be provided with an operative set as oriented on the
`damaged knee joint and comprising femoral and tibial
`components of an endoprosthesis and femoral and tibial
`30 components of an associated implantation aid as prepared in
`accordance v.rith the method according to the present inven(cid:173)
`tion. The operation of the patient will be carried out by first
`opening the knee joint and by subsequently severing the
`damaged components first at the tibia and then on the
`35 femoral bone. This particular severing v.rill be carried out by
`using the implantation aid as a guide aid for guiding an
`oscillating sawing blade along the guiding slots of the
`implantation aid. The joint bones will thereby receive resec(cid:173)
`tion areas which exactly correspond with the severing areas
`40 as provided on the tibial and femoral components of the
`endoprosthesis of the particular operative set. These com(cid:173)
`ponents may therefore be snugly fitted to the resection areas
`by means of the anchoring pegs which will be anchored in
`associated peg holes of the resection areas. When no anchor-
`45 ing means as e.g., such pegs coresponding peg holes are
`provided the components of the endoprosthrsis could then
`also be put together by any knows comenting method which
`v.rill allow a correct seating of the components of the
`endoprosthesis prior to a final closing of the knee joint.
`The preparation of the endoprosthesis could also include
`the preparation of a component which will be used for the
`patella of the damage knee joint. The method could further
`be also applied to surgical interventions of other joints such
`as for example of the ankle joint or of finger and toe joints
`and it could also be used for the reconstruction of bone and
`cartilage tissues as well as soft tissues.
`
`55
`
`3
`to the contours of a healthy knee joint. This virtual alteration
`should preferably exemplified with a stretched condition of
`the knee allowing a precise plotting of the rear and lower
`joint surface of the femoral bone and .of the entire shin?one
`surface of the tibia to thereby obtam more or less ideal
`contours for the fitting of the endoprosthesis during the
`factual surgical intervention as later carried out. This step of
`virtually altering the preoperative tomographic image may
`be exen=iplified manually or may alternatively be exemplified
`by the preparation of a mirror image of a healthy knee joint
`of the patient. It may also be prepared by identifying an
`image of a healthy knee joint having contours of the femoral
`bone and of the tibia comparable to the contours of the
`preoperative image of the damaged knee joint.
`The altered femoral and tibial components defining there(cid:173)
`fore respective components of a healthy knee joint are
`subsequently virtually severed a'S respectively visual pat(cid:173)
`terns for the endoprosthesis. The severing is carried out on
`marked severing areas which later serve as thusly predeter(cid:173)
`mined severing areas for severing the associated compo(cid:173)
`nents of the damaged knee joint from the joint bones during
`the factual operation of the damaged knee joint. The sever(cid:173)
`ing is carried out on the femoral bone of the damaged knee
`joint preferably with three different severin? areas and on t~e
`tibia with one or with two different severmg areas. By this 25
`virtual severing visual patterns are therefore obtained which
`are directly oriented in respect to the damaged knee joint and
`thusly allow a preparation of femoral and tibial components
`of an· endoprosthesis which exactly correspond to the femo(cid:173)
`ral and tibia components as altered by the preceding step of
`virtually altering the preoperative tomographic image of the
`damaged knee joint. The different severing areas as marked
`for this virtual severing step could preferably also be supple(cid:173)
`mented virtually with anchoring means such as, e.g., pegs
`for the three-di~ensional components of the endoprosthesis
`when later fitted to the resection areas of the joint bones.
`Such pegs when exemplified would then be intended for
`being fitted snugly into associated peg holes of the corre(cid:173)
`sponding resection areas of the joint bones.
`This marking of severing areas is also used for virtually
`preparing tomographic images of femoral and tibial tem(cid:173)
`plates for the femoral and tibial components of the damaged
`knee joint as corresponding separate visual patterns of an
`impla~tation aid which by virtually transferring the mark~d
`severing areas for the preparation of such templates will
`therefore fit snugly to the damaged knee joint. As in case of
`the preparation of the femoral and tibial components of the
`endoprosthesis the virtually prepared tomographic image of
`such femoral and tibial templates may directly be used for
`the preparation of the associated implantation aid. The
`marked severing areas showing up on the templates are
`transferred to the corresponding components of the implan(cid:173)
`tation aid and serve as corresponding guiding slots of a guide
`aid for guiding, e.g., an oscillating sawing blade during the
`factual operation of the damaged knee joint when the
`damaged knee joint components are then factually severed
`from the joint bones. When preparing the virtual image of
`the femoral and tibial templates it is therefore essential that
`the implantation aid and therefore in the first place the
`femoral and tibial templates receive a very exact positioning 60
`on the damaged knee joint so that with the oscillating sav.ring
`blade correspondincrlv exact resection surfaces will be
`obtained on the join7 bones for fitting snugly to the associ(cid:173)
`ated surfaces of the femoral and tibial components of the
`endoprosthesis for which the marked severing areas have 65
`been virtually transferred for the preparation of such tem(cid:173)
`plates. It should therefore be preferred to design such
`
`50
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 illustrates schematically the step of preparing a
`preoparative tomographic image of a damaged kneejoin and
`the preparation of virtual severing areas for the damaged
`femoral and tibial components of the joint.
`FIG. 2 illustrates schematically the virtual preparation
`tomographic images of femoral and tibial templates as visual
`patterns of an implantation aid whereby the severing areas
`are virtually transferred as virtual guiding slots of a guide aid
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`US 6,510,334 Bl
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`for guiding an oscillating sawing blade during operation of
`the damaged knee joint.
`FIG. 3 illustrates schematically the virtual severing of
`femoral and tibial components of the damaged knee joint
`after having been virtually altered on the preoperative tomo-
`graphic image for approximating the contours of the femoral
`bone and of the tibia of the damaged knee joint to those of
`a healthy knee joint.
`FIG. 4 illustrates schematically the three-dimensional
`femoral and tibia components of the endoprosthesis as 10
`prepared on the basis of their respective visual patterns.
`FIG. 5 illustrates schematically the femoral and tibial
`components of the endoprosthesis in accordance with and
`alternative embodiment and inducing pegs and associated 15
`pegs holes for allowings the components to be snugly fitter
`to the femoral bone and the tibia of the knee joint after its
`operation by use of the femoral and tibial components of the
`implantation and.
`In the drawings, numerals 1 and 2 refer to the femoral
`bone and the tibia of a knee joint. Numerals 3 and 4 refer to
`the virtual severing areas as prepared on the preoperative
`tomographic image of a damaged knee joint which severing
`areas are virtualty transfered during a virtual preparation of
`tomographic images of femoral and tibia templates 5 and 6
`for which the severing areas are exemplified as virtual
`guiding slots 7 and 8 of a guide aid. Numeral 9 and 10 refer
`to the femoral and tibial components of the damaged knee
`joint when severed virtually from the preoperative tomo(cid:173)
`graphicc image of the damaged knee joint after it has been
`virtually altered for approximating the contours of the
`femoral bone and of the tibia of the damaged knee joint to
`those of a healthy knee joint whereby these femoral and
`tibial components serve as visual patterns for the preparation
`of thee-dimensional femoral and tibial components of the
`endoprosthesis. Numerals 11, 12 and 13 refer to the com(cid:173)
`ponents of the endoprosthesis which may be provided with
`pegs 14 that will fit snugly into peg holes 15 of the
`associated resection areas on the femoral bone 1 and of the
`tibia 2.
`Although several embodiments of the present invention
`and its advantages have been described in detail, it should be
`understood that mutations, changes, substitution,
`transformations, modifications, variations and alterations
`can be made without departing from the teachings of the
`present invention, the spirit and scope of the invention being
`set forth by the appended claims.
`We claim:
`1. A method of producing an endoprosthesis as a joint
`substitute for knee joints comprising
`preparing a preoperative tomographic image of the dam(cid:173)
`aged knee joint;
`virtually altering the preoperative tomographic image for
`approximating the contours of at least the femoral bone
`and of the tibia of the damaged knee joint to those of
`a healthy knee joint;
`virtually severing the altered femoral and tibial compo(cid:173)
`nents defining respective components of a healthy knee
`joint as respectively visual patterns for the endopros(cid:173)
`thesis whereby this severing is carried out on marked
`severing areas which later serve as thusly predeter(cid:173)
`mined severing areas for severing the associated soci(cid:173)
`ated components of the damaged knee joint from the
`joint bones during operation of the damaged knee joint;
`
`6
`virtually transferring the marked severing areas for vir(cid:173)
`tually preparing tomographic images of a femoral and
`of a tibial template for the femoral and the tibial
`components of the damaged knee joint as respectively
`separate visual patterns of an implantation aid which
`fits snugly to the damaged knee joint whereby the
`severing areas when virtually transferred to the implan(cid:173)
`tation aid are exemplified as virtual guiding slots of a
`guide aid for guiding an oscillating sawing blade during
`operation of the damaged knee joint when the damaged
`knee joint components are factually severed from the
`joint bones;
`preparing three-dimensional femoral and tibial compo(cid:173)
`nents of the endoprosthesis and three-dimensional
`femoral and tibial components of the associated
`implantation aid on the basis of their respective visual
`patterns.
`2. The method of claim 1, wherein the altered femoral and
`tibial components defining respective components of a
`healthy knee joint are virtually supplemented on the marked
`severing areas with snugly fitting anchoring means for the
`three-dimensional components of the endoprosthesis when
`later fitted to the resection areas of the joint bones.
`3. The method of claim 1, wherein the tomographic
`images are prepared by a computed tomography.
`4. The method of claim 1, wherein the tomographic
`images are prepared by a nuclear spin resonance tomogra(cid:173)
`phy.
`5. The method of claim 1, wherein the step of virtually
`30 altering the preoperative tomographic image for defining a
`healthy knee joint is exemplified manually.
`6. The method of claim 1, wherein the step of virtually
`altering the preoperative tomographic image for defining a
`healthy knee joint includes preparing a mirror image of a
`35 healthy knee joint of the patient.
`7. The method of claim 1, wherein the step of virtually
`altering the preoperative tomographic image for defining a
`healthy knee joint includes identifying an image of a healthy
`knee joint having contours of at least the femoral bone and
`40 of the tibia comparable to the contours of the preoperative
`image of the damaged knee joint.
`8. The method of claim 1, wherein the step of preparing
`the three-dimensional femoral and tibial components of the
`endoprosthesis and of the associated implantation aid
`45 includes digitizing the corresponding visual patterns and
`using the digitized visual patterns to prepare said compo(cid:173)
`nents according to a copying process.
`9. An operative set for carrying out operations on dam(cid:173)
`aged knee joints, comprising femoral and tibial components
`50 of an endoprosthesis and femoral and tibial components of
`an associated implantation aid as produced in accordance
`with the method of claim 1.
`10. The operative set of claim 9, wherein the femoral and
`tibial components of the endoprosthesis are provided with
`55 pegs which are intended for being fitted snugly into asso(cid:173)
`ciated peg holes of the associated resection areas of the joint
`bones.
`11. The operative set of claim 9, wherein the tibial
`component of the endoprosthesis comprises a plastic part
`and a metallic part of which the plastic part receives an
`arrangement between the metallic part of the tibial compo(cid:173)
`nent and a corresponding metallic femoral component of the
`endoprosthesis.
`
`20
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`25
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`60
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`* * * * *
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