(12) United States Patent
`Robie et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,575,980 B1
`Jun. 10, 2003
`
`US006575980B1
`
`(54)
`
`(75)
`
`METHOD AND APPARATUS FOR FEMORAL
`RESECTION
`
`Inventors: Bruce Robie, New York, NY (US);
`Jordan Ryalls, New York, NY (US);
`Joseph Lipman, New York, NY (US);
`Albert H. Burstein, Longboat Key, FL
`(US); Thomas P. Sculco, New York,
`NY (US)
`
`(73)
`
`Assignee: New York Society for the Ruptured
`and Crippled Maintaining the
`Hospital for Special Surgery, New
`York, NY (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`(22)
`
`Appl. No.: 09/362,599
`Filed:
`Jul. 28, 1999
`
`(63)
`(60)
`
`(51)
`(52)
`
`(58)
`
`(56)
`
`Related US. Application Data
`
`Continuation-in-part of application No. PCT/US98/01655,
`?led on Jan. 27, 1998.
`Provisional application No. 60/036,220, ?led on Jan. 28,
`1997.
`
`Int. Cl.7 .............................................. .. A61B 17/58
`
`US. Cl. ........................... .. 606/88; 606/82; 606/86;
`606/88
`Field of Search ............................. .. 606/79, 86—88,
`606/80, 82, 90
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2,794,253 A
`4,424,035 A
`5,098,436 A
`5,258,032 A
`5,454,816 A
`
`6/1957
`1/1984
`3/1992
`11/1993
`* 10/1995
`
`FitZsimmons
`Hansen
`Ferrante et al.
`Bertin
`Ashby ....................... .. 606/88
`
`5,458,645 A 10/1995 Bertin
`5,474,559 A 12/1995 Bertin et al.
`5,514,139 A
`5/1996 Goldstein et al.
`5,571,197 A 11/1996 Insall
`5,601,563 A
`2/1997 Burke et al.
`5,649,929 A * 7/1997 CallaWay ................... .. 606/88
`5,665,090 A
`9/1997 Rockwood et al.
`5,688,282 A * 11/1997 Baron et al. ................ .. 606/87
`5,702,460 A 12/1997 Carls et al.
`5,716,361 A
`2/1998 Masini
`5,800,438 A
`9/1998 Tuke et al. ................. .. 606/90
`5,830,216 A * 11/1998 lnsall et al. ..
`606/87
`5,860,981 A * 1/1999 Bertin et al. ................ .. 606/88
`5,879,393 A
`3/1999 Whiteside et al.
`6,077,270 A * 6/2000 KatZ ......................... .. 606/88
`
`FOREIGN PATENT DOCUMENTS
`
`SU
`W0
`
`1600749
`WO 98/52499
`
`10/1990
`11/1998
`
`* cited by examiner
`
`Primary Examiner—Gary Jackson
`(74) Attorney, Agent, or Firm—Darby & Darby
`(57)
`ABSTRACT
`
`An instrument is provided for use in shaping a femur
`preparatory to implantation of a knee prosthesis. A gap
`checking device is ?xed to the distal end of the patient’s
`femur and referenced to the epicondyles of the femur. The
`gap checking device includes slots through which a cutting
`instrument can be passed to shape the femur so that it can
`receive the femoral component of the prosthesis. One of the
`slots enables the distal femoral cut to be made. The thickness
`of the gap checking device is selected so that the distance
`between the distal femoral cut and the distal surface of the
`gap checking device plus the thickness of a shim resting on
`the cut proximal tibia surface is equal to the combined
`thickness of the tibial and femoral components of the
`prosthesis. This enables balancing of the ligaments to be
`checked before the femoral cuts are made, but while the gap
`checking device is secured to the femur.
`
`36 Claims, 13 Drawing Sheets
`
`-1-
`
`Smith & Nephew Ex. 1012
`IPR Petition - USP 7,534,263
`
`

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`U.S. Patent
`U.S. Patent
`
`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 1 0f 13
`Sheet 1 of 13
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`US 6,575,980 B1
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`FIG. I
`FIG.
`I
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`-2-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 2 0f 13
`Sheet 2 of 13
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`US 6,575,980 B1
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`..
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`r.
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`.2 7
`l __
`
`w
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`-3-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 3 0f 13
`Sheet 3 of 13
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`FIG. 4
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`-4-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 4 0f 13
`Sheet 4 of 13
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 5 0f 13
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`FIG. 70
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`-6-
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`Jun. 10, 2003
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`Sheet 6 0f 13
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`FIG. 70
`
`205
`
`200
`
`I M
`
`220
`
`,,
`
`(
`
`am b
`
`FIG- 7d
`
`200?
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`I
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`I
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`200
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`2:5
`
`a‘
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`I GUI *
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`WI’)
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`x]
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`v
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`I
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`K
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`-7-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 7 0f 13
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`-8-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`Sheet 8 0f 13
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`Jun. 10, 2003
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`Sheet 9 0f 13
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`FIG. 8d
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`Olb
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`-10-
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`Jun. 10, 2003
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`Sheet 10 0f 13
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`US 6,575,980 B1
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`CUT I
`(SLOT 9s‘)
`
`CUT 5
`
`CUT e‘ (SLOT 84')
`
`(SLOT 83')
`
`\' CUT4 (SLOT 92 )
`CUT 2
`,
`(SLOT 96 R
`CUT 3 (SLOT 94)
`
`FIG. 9b
`
`km]?
`
`42 b'
`
`-11-
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`U.S. Patent
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`Jun. 10, 2003
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`Sheet 11 0f 13
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`US 6,575,980 B1
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`SIO
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`Hlllh,
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`500
`
`51o
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`‘i=1. 5%
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`' 5l5
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`-12-
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`Jun. 10, 2003
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`Sheet 12 0f 13
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`FIG. IOc
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`-13-
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`U.S. Patent
`U.S. Patent
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`Jun. 10, 2003
`Jun. 10, 2003
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`US 6,575,980 B1
`
`1
`METHOD AND APPARATUS FOR FEMORAL
`RESECTION
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application claims priority pursuant to 35 U.S.C. 119
`based upon US. Provisional Application Ser. No. 60/036,
`220 ?led Jan. 28, 1997, the entire disclosure of Which is
`incorporated herein by reference.
`This application further is a continuation-in-part of Inter
`national Application No. PCT/US98/01655 ?led Jan. 27,
`1998, the entire disclosure of Which is also incorporated
`herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to an instrument and method
`for shaping a femur preparatory to implanting a knee pros
`thesis.
`2. Description of Related Art
`A total knee replacement or prosthesis, substitutes for a
`patient’s arthritic or otherWise dysfunctional natural knee
`joint. The prosthesis offers the patient an alternative treat
`ment for the chronic pain and discomfort often associated
`With such problems.
`Burstein et al. US. Pat. No. 4,298,992 illustrates a popu
`lar total knee joint prosthesis knoWn as the Insall-Burstein
`(I/B) knee. Such prostheses comprise a femoral component
`attached to the patient’s femur, a tibial component attached
`to the patient’s tibia, and a patellar component attached to
`the patient’s patella. To use this prosthesis, it is necessary to
`shape by resection the patient’s femur, tibia and patella. The
`tibia and patella are shaped by a ?at cut. In the case of the
`I/B prosthesis, the femoral component requires ?ve cuts
`about the periphery of the femur and three cuts in the
`intercondylar notch in the distal end of the femur. These cuts
`conform to complementary portions of the femoral compo
`nent Which engage the bone. It is important that these
`femoral cuts be made precisely and located so that the
`position of the femoral component and the tibial component
`Will closely approximate the positions of their anatomical
`counterparts. Proper positioning of the femoral and tibial
`components is required to insure the patient’s natural ana
`tomic limb alignment and normal anatomical movement.
`As part of the installation of a knee joint prosthesis, it is
`important to balance the ligaments crossing the joint. Bal
`ancing the ligaments means performing soft tissue releases,
`as necessary, so as to ensure that When the femur is lifted off
`of the tibia by a force directed along the long axis of the
`tibia, and the tibia is positioned in natural anatomic limb
`alignment, the tension in the medial and lateral ligamentous
`support is nearly equal. In order for the ligamentous tension
`to be nearly equal, the distance betWeen the medial aspect of
`the femur and tibia, and the lateral aspect of the femur and
`tibia must be nearly equal When the tibia is in natural
`anatomic limb alignment. The distance betWeen the femur
`and tibia should also be approximately equal throughout the
`range-of-motion of the tibia from full extension to approxi
`mately 90 degrees of ?exion. The distance betWeen the
`femur and tibia is commonly called “the gap”, and the
`process of lifting the femur, and measuring the distance
`betWeen the femur and tibia is commonly called “checking
`the gap”. Heretofore, gap checking has been done after the
`femur has been shaped and only at full extension, and 90
`degrees ?exion. If proper balancing can not be achieved,
`
`2
`then it may be necessary to reshape the femur, Which is
`obviously undesirable, or to use a more constrained total
`knee design, thus limiting knee motion.
`An object of the invention is to provide an instrument for
`use in shaping the distal surface of a femur preparatory to
`implantation of a knee prosthesis in Which the gaps can be
`checked and adjusted prior to shaping the femur. This
`eliminates the need to recut the femur and reduces the time
`required for surgery. Moreover, since it is easier to check the
`gaps With the invention, it is likely that more surgeons Will
`take the time to check the gaps and, therefore, the quality of
`the surgery Will improve.
`A further object of the invention is to provide a device for
`shaping the distal surface of a femur preparatory to implant
`ing a knee prosthesis Wherein all of the cuts required to
`shape the femur can be made using a single instrument.
`Yet another object of the present invention, is the ability
`to check the gaps continuously throughout the range-of
`motion of the knee, not just at full extension and 90 degrees
`?exion, as With conventional devices.
`The most popular types of instruments used to shape the
`femur are intramedullary devices in Which a cutting guide is
`positioned at the distal end of the femur relative to a rod
`Which is driven into the intramedullary canal of the femur.
`Historically, surgeons have also used extramedullary align
`ment to orient the instruments to cut the distal femur. The
`present invention may be used With intramedullary or
`extramedullary alignment techniques.
`SUMMARY OF THE INVENTION
`The principal component of the knee instrument accord
`ing to the invention comprises a gap checking device Which
`includes a curved base adapted to engage the distal end of
`the patient’s femur. Aplurality of slots are de?ned in the gap
`checking device for guiding the cutting instrument used to
`shape the femur. The gap checking device can be referenced
`to the patient’s femur using conventional intramedullary or
`extramedullary locator techniques.
`The thickness of the gap checking device is such that the
`distance betWeen the distal cut in the femur to the distal
`surface of the gap checking device plus the thickness of a
`shim corresponds in a predetermined Way to the thickness of
`the femoral and tibial components of the prosthesis.
`Accordingly, the gaps can be checked With the gap checking
`device after placing the shim on the cut surface of the tibia.
`The shim also protects the cut surface of the tibia to prevent
`bone damage. After the knee has been properly balanced,
`bone cuts are made by passing a cutting instrument through
`the slots in the gap checking device. If necessary, a slot
`extender may be attached to the gap checking device to
`extend or increase the length of the slots.
`
`10
`
`15
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`20
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`25
`
`30
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`35
`
`40
`
`45
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The foregoing and other features of the present invention
`Will be more readily apparent from the folloWing detailed
`description and draWings of illustrative embodiments of the
`invention Wherein like reference numbers refer to similar
`elements throughout the several vieWs and in Which:
`FIG. 1 is an exploded perspective vieW shoWing a 5-in-1
`gap checking device and slot extender according to a ?rst
`embodiment of the invention;
`FIG. 2 is an exploded perspective vieW of a ?rst embodi
`ment of a gap checking device and intramedullary locating
`device in accordance With the present invention;
`FIG. 3 is a perspective vieW from the front shoWing the
`assembled gap checking device and intramedullary locating
`device of FIG. 2;
`
`55
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`US 6,575,980 B1
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`3
`FIG. 4 is a side plan vieW of the assembled gap checking
`device and intramedullary locating device;
`FIG. 5 is a partial cross-sectional side plan vieW of the
`assembled gap checking device and slot extender of FIG. 1;
`FIG. 6 is a perspective vieW of the gap checking device
`of FIG. 1 positioned on the femur bone after the locating
`device has been removed;
`FIGS. 7a through 7d are different vieWs of an alternative
`embodiment of the intramedullary locating device in accor
`dance With the present invention;
`FIG. 8a is an exploded vieW of the alternative intramed
`ullary locating device and an 8-in-1 gap checking device in
`accordance With the present invention;
`FIGS. 8b through 8d are different vieWs of the alternative
`embodiment of the intramedullary locating device of FIGS.
`8a assembled to the 8-in-1 gap checking device;
`FIG. 9a is a side vieW of a femoral component and the
`8-in-1 gap checking device in accordance With the present
`invention;
`FIG. 9b is a bottom vieW of the femoral component and
`the 8-in-1 gap checking device of FIG. 9a;
`FIG. 10a is a side-by-side vieW of the 5-in-1 gap checking
`device in full extension before resection of the distal end of
`the femur and after resection With the knee prosthesis
`components;
`FIG. 10b is a side-by-side vieW of the 5-in-1 gap checking
`device in 90 degrees ?exion before resection of the distal
`end of the femur and after resection With the knee prosthesis
`components;
`FIG. 10c is a side-by-side vieW of the 5 -in-1 gap checking
`device at an angular position betWeen full extension and 90
`degrees ?exion before resection of the distal end of the
`femur and after resection With the knee prosthesis compo
`nents;
`FIG. 11 is an exploded vieW of the 8-in-1 gap checking
`device With angle extender attachments in accordance With
`the present invention; and
`FIG. 12 is bottom vieW of the intramedullary locating
`device of FIGS. 7a—7d oriented at an angle of 3 degrees in
`a clockWise direction.
`
`10
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`15
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`25
`
`35
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`45
`
`The instrumentation according to the invention includes a
`locating device, a gap checking device and a slot extender.
`A locating device is ?rst used to properly position the gap
`checking device on the distal end of the femur. The surgeon
`uses the gap checking device to balance the ligaments of the
`patient’s knee before any of the femoral cuts are made. Once
`properly positioned, a cutting instrument or blade is guided
`through slots in the gap checking device in order to make the
`appropriate cuts in the femur. Prior to making the cuts, the
`slot extender may be attached to the gap-checking device to
`extend the length of the slots.
`FIG. 1 is a ?rst embodiment of a 5-in-1 gap checking
`device 40‘ and slot extender 80‘ in accordance With the
`present invention. Gap checking device 40‘ has a curved
`base 42‘ forming tWo bifurcated portions 42a‘ and 42b‘,
`Which overlay the femoral condyles.
`As shoWn in the exploded vieW in FIG. 11, angle extender
`attachments 42a“, 42b“ may be secured, for example, by
`dovetail or tongue-and-groove, to the free end of the por
`tions 42a‘, 42b‘, respectively, to extend the base 42‘ around
`the femoral condyles in order to check the balance of the
`
`55
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`65
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`4
`ligaments over a Wider angular range, as explained in detail
`beloW. Outrigger arms 44‘ and 46‘ are immovably attached
`at one end to opposite sides of the base 42‘. One or more
`apertures 900 are de?ned in the outrigger arms 44‘ and 46‘
`through Which pins 108 are inserted to secure the gap
`checking device 40‘ to the femur.
`Aball tip 66‘ is mounted to one end of the curved base 42‘,
`Which overlies the femur during the operation. TWo bores
`910 are de?ned through the ball tip 66‘ through Which pins
`108 are inserted to secure the gap checking device 40‘, When
`properly positioned, to the femur. As shoWn most clearly in
`FIGS. 3 and 5, the gap checking device 40‘ includes ?ve
`slots 70‘, 72‘, 74‘, 76‘ and 78‘ Which, as explained beloW,
`guide the blades used to shape the surface of the femur to
`receive the femoral component of the prosthesis.
`Once secured in its proper position, the gap checking
`device 40‘ is used to check the balance of the ligaments in
`extension, ?exion and any position therebetWeen prior to
`making any cuts in the femur bone. If the ligaments are not
`properly balanced, the surgeon may perform selected
`releases of soft tissue (ligaments, capsule, muscle) to adjust
`the gaps in the conventional manner, While the gap checking
`device is still attached to the femur. In order to be able to
`check the balance of the ligaments, the thickness of the
`curved base 42‘ and shim 500, Which protects the tibia bone,
`should be such that the patient’s femur and tibia Will be
`separated by the same distance that they Will be separated
`after the femoral and tibial components of the knee pros
`thesis are in place. FIGS. 10a through 10c shoW side-by-side
`vieWs of the gap checking device 40‘ and prosthesis com
`ponents in full extension, 90 degrees ?exion, and at an angle
`betWeen full extension and 90 degrees ?exion, respectively.
`FIG. 10a shoWs the femur bone 505, tibia bone 510 and
`prosthesis components including femoral component 525,
`tibial insert 520 and tibial tray 515. The distance denoted
`betWeen the arroWs is the same When the gap checking
`device 40‘ is properly positioned on the distal end of the
`femur prior to resection (left hand side of FIG. 10a) as it is
`after resection When the prosthesis components are put in
`place (right hand side of FIG. 10a). In other Words, the
`distance from the slot 70‘ (used to make the distal cut in the
`femur bone) at the distal surface of the base 42‘ to the surface
`of the cut tibia bone is the same as the distance from the
`surface of the distal cut of the femur bone to the surface of
`the cut tibia When the prosthesis components are in place. To
`accommodate different thicknesses of tibial inserts, match
`ing shims of different thicknesses are provided. The base 42‘
`of the gap checking device 40‘ is therefore con?gured so that
`the balance of the ligaments may be checked over a con
`tinuous range-of-motion While the gap checking device 40‘
`is secured to the distal end of the femur and prior to making
`cuts in the femur bone. This is advantageous over conven
`tional techniques in Which the cutting guide must ?rst be
`removed and the prosthesis components placed on the cut
`femur and tibia in order to check the balance of the liga
`ments. The kinematics of the knee, While the gap checking
`device is secured to the femur and prior to making any cuts,
`Will be substantially the same as the kinematics after the
`femoral and tibial components have been implanted,
`because the structure and outer surface of the gap checking
`device 40‘ is matched to the design of the prosthesis com
`ponents. This Way, balancing of the ligaments may be
`checked With the gap checking device While it is secured to
`the femur and before making any cuts to the femur, as if the
`femoral component itself Was being tested.
`After the gaps have been checked and the ligaments
`balanced, a slot extender 80‘ (FIG. 1) may be secured, if
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`5
`necessary, to the gap checking device 40‘ to lengthen the
`slots therein. To retain the gap checking device 40‘ and slot
`extender 80‘ together during the shaping operation, a thumb
`screW 150 is inserted through a hole 152 Within the slot
`extender 80‘ and into engagement With a threaded bore 154
`on the gap checking device 40‘. As shoWn in FIG. 5, slot
`extender 80‘ includes slots 90‘, 92‘, 94‘, 96‘ and 98‘, aligned
`With the corresponding slots 70‘, 72‘, 74‘, 76‘ and 78‘ of the
`gap checking device 40‘, thereby lengthening or extending
`the slots through Which a cutting blade can be inserted to
`shape the femur. The distal cut is made through slots 70‘ and
`90‘. The posterior cut is made through slots 78‘ and 98‘, and
`the anterior cut through slots 72‘ and 92‘. The anterior
`chamfer cut is made through slots 76‘ and 96‘, and the
`posterior chamfer cut is made through slots 74‘ and 94‘. It
`should be noted that the slot extender 80‘ is only used When
`the base is not suf?ciently thick so that it is necessary to
`extend the length of the slot.
`The operation of the intramedullary locating device and
`gap checking device 40‘ shoWn in FIGS. 1—6 is as folloWs.
`Initially, an intramedullary rod 174 is inserted into the
`intramedullary canal of the femur and then used to align the
`gap checking device. The intramedullary locating device
`used to provide intramedullary alignment, as shoWn in
`FIGS. 2—4, includes a ?rst member 160 Which has a trian
`gular projection 161 that mates With the recess 77‘ of the gap
`checking device 40‘. A?rst member 160 is secured to the gap
`checking device 40‘ by a screW 164 Which engages a
`threaded hole 165 Within the recess 77‘. The ?rst member
`160 is shaped to form parallel tracks 166 and 168 in Which
`a slider 170 having a base and an upstanding collar 172
`projecting therefrom is displaceably positioned. The surgeon
`selects from among different upstanding collars 172 dis
`posed at different angles a, relative to a reference axis
`perpendicular to the horiZontal plane de?ned by the base in
`order to set the varus/valgus orientation angle. In a preferred
`embodiment, a is at an angle betWeen approximately 2
`degrees and approximately 7 degrees relative to a reference
`axis perpendicular to the horiZontal plane de?ned by the
`base. The assembled intramedullary locating device and gap
`checking device 40‘ are placed on to the distal end of the
`femur so that the intramedullary rod 174 passes through the
`upstanding collar 172. Gap checking device 40‘ is properly
`positioned by: (1) displacing the gap checking device 40‘
`along the axis of the intramedullary rod until the distal
`surface of the gap checking device 40‘ rests on the cartilage
`of the distal surface of the femur, (2) displacing the slider
`170 Within tracks 166, 168 of the ?rst member 160 until the
`ball tip 66‘ rests on the anterior surface of the femur; and (3)
`rotating the gap checking device 40‘ until the free end of the
`outrigger arms 44‘, 46‘ are substantially aligned With the
`center of the medial and lateral epicondyles, respectively, of
`the femur.
`If cartilage destruction is so signi?cant that the outrigger
`arms 44‘, 46‘ do not align With the epicondyles of the knee
`When the distal surface of the gap checking device 40‘ rests
`on the cartilage of the femur, Wedges 180 having the shape
`shoWn in FIGS. 3—5 may be used to ?ll in the space
`therebetWeen and ensure proper positioning of the gap
`checking device. Each Wedge 180 includes a support surface
`182 Which is adapted to contact the distal surface of the
`femur When the gap checking device is properly positioned
`on the distal end of the femur. The Wedges are preferably
`shaped so as to be supported in slots 76‘ of the gap checking
`device used to perform the anterior chamfer cut.
`Accordingly, the Wedges 180 ensure the proper positioning
`of the gap checking device 40‘ so that the distal cut is
`accurately made in the femur.
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`After the gap checking device 40‘ has been properly
`positioned on the femur, the surgeon tamps the pins 108
`through apertures 900, 910 into the epicondyles and the
`anterior surface of the femur, respectively. Once secured in
`its proper position, the surgeon removes the intramedullary
`locating device and rod from the femur, as shoWn in FIG. 6.
`The gap checking device 40‘ is used to check the balance of
`the ligaments in full extension, approximately 45 degrees
`?exion, and any position therebetWeen. If the ligaments are
`not properly balanced, the surgeon may perform selected
`releases of soft tissue (ligaments, capsule, muscle) to adjust
`the gaps. If angle extenders 42a“, 42b“ are attached to the
`gap checking device 40‘ the balance of the ligaments in
`extension and ?exion may be checked over a Wider angular
`range from full extension to approximately 90 degrees
`?exion, and any position therebetWeen. The length of the
`slots of the gap checking device 40‘ may be extended by
`attaching the slot extender 80‘ to the gap checking device 40‘
`via the thumb screW 150 received in the threaded apertures
`152 and 154. The cutting instrument is then passed through
`the slots of the gap checking device and the slot extender 80‘
`in order to make the cuts in the femur bone.
`An alternative embodiment of an intramedullary locating
`device 200 in accordance With the present invention is
`shoWn in FIGS. 7a through 7d. Intramedullary locating
`device 200 includes a ?rst member 205. A second member
`210, having a channel de?ned therein and slidably displace
`able in the direction indicated by the arroWs so that the ?rst
`member 205, is received in the channel of the second
`member and secured by a fastener 225. First member 205 is
`secured to the gap checking device 40‘ by a thumb screW 220
`received in the threaded aperture 154. Slider 216 having a
`base 217 and an upstanding collar 215 slides Within a track
`of the ?rst member 205. In a preferred embodiment, the
`surgeon selects from among several available sliders each
`With the upstanding collar 215 disposed relative to a refer
`ence axis perpendicular to the horiZontal plane de?ned by
`the base 217 at different ?xed angles 0t, preferably at an
`angle betWeen approximately 2 degrees and approximately
`7 degrees, in order to set the varus/valgus orientation angle.
`It is Within the intended scope of the invention to set the
`angle 0t, as desired. A free end of the second member 210
`terminates in a movable paddle 201a and a ?xed paddle
`201b.
`FIGS. 8a—8d shoW different embodiments of the alterna
`tive intramedullary locating device of FIGS. 7a—7d
`assembled to an alternative 8-in-1 gap checking device. In a
`preferred embodiment shoWn in FIG. 8a, movable paddle
`201a is positionable in one of tWo predetermined settings
`(denoted “R” and “L”), preferably set to approximately 3
`degrees rotation in a clockWise direction or approximately 3
`degrees rotation in a counterclockWise direction, to account
`for external rotation of the femoral component relative to the
`femur for the right versus the left knee. Movable paddle
`201a is secured in place by a fastener 230. By Way of
`example, FIG. 12 shoWs the movable paddle 201a posi
`tioned such that the locating device 200 is offset 3 degrees
`in a clockWise direction relative to the reference plane
`denoted by the solid line. It should be noted, hoWever, that
`the predetermined angular settings may be speci?ed as
`desired. FIGS. 8b through 8d shoW the intramedullary
`locating device 200 assembled to the 8-in-1 gap checking
`device 40“.
`The features and details of the 8-in-1 gap checking device
`40“ are the same as those described above With respect to the
`?rst embodiment, except for additional slots forming cuts 6
`through 8. FIGS. 9a and 9b shoW the 8-in-1 gap checking
`
`-17-
`
`

`
`US 6,575,980 B1
`
`7
`device 40“ and the femoral component 300 of the knee
`prosthesis. The solid lines represent the cuts made in the
`distal end of the femur bone by passing the cutting blade or
`instrument through each of the slots de?ned in the gap
`checking device 40“. The shape of the distal surface of the
`resected femur complements the distal surface of the femo
`ral component 300. Cuts 1 through 5 shoWn in FIG. 9a
`correspond to slots 98‘, 96‘, 94‘, 92‘, 90‘, respectively, in FIG.
`5. An additional three cuts 6, 7 and 8, are made in order to
`form a U-shaped notch in the distal end of the femur. Cuts
`7 and 8 are parallel to one another and de?ned by the
`confronting surfaces of the bifurcated portions 42a‘, 42b‘of
`the base 42‘, as shoWn in FIG. 9b. Cut 6 connects cuts 7 and
`8 to form a U-shaped notch in the femur. In one embodiment
`slot 83‘ is used to form cut 6. In another embodiment, slot
`84‘ may be used to form an alternate 6‘ cut to connect cuts
`7 and 8, that is deeper than that formed using slot 83‘. This
`alternative slot is suitable, for example, during revision
`When using a constrained condylar component. Although a
`single gap checking device 40“ having both slots 83‘ and 84‘
`is shoWn in FIGS. 8a—9b, since only one slot is used to form
`the 6th cut, it is also contemplated and Within the intended
`scope of the invention to use tWo gap checking devices 40“,
`one having slot 83‘ and the other having slot 84‘, from Which
`the surgeon selects one.
`In operation an intramedullary rod is inserted into the
`intramedullary canal of the femur bone. Movable paddle
`201a is set to one of the predetermined positions depending
`on Whether the left or right knee is being Worked on. The
`intramedullary locating device 200 is secured to the gap
`checking device 40‘ via the thumb screW 220 and the
`assembled device is placed on to the distal end of the femur
`so that the intramedullary rod passes through the collar 215.
`Then the surgeon positions the gap checking device 40‘ by
`(1) displacing the gap checking device 40‘ along the axis of
`the intramedullary rod until the distal surface of the gap
`checking device 40‘ rests on the cartilage of the distal surface
`of the femur; (2) displacing the slider 215 Within the tracks
`of the ?rst member 205 until the ball tip 66‘ rests on the
`anterior surface of the femur; and (3) displacing the second
`member 210 relative to the ?rst member 205 and rotating the
`gap checking device 40‘ until the paddles 201a, 201b contact
`the posterior condyles of the femur. As in the ?rst
`embodiment, if necessary, a Wedge may be inserted in slot
`76‘ if the distal surface of the gap checking device 40‘ does
`not contact the distal end of the femur. Once the gap
`checking device 40‘ is properly aligned it is secured to the
`femur using pins 108 inserted through apertures 900, 910
`and then the intramedullary locating device 200 is removed
`from the femur. A slot extender 80‘ may be attached to the
`gap checking device 40‘, as described in detail above With
`respect to the ?rst embodiment.
`Although the draWings and accompanying description
`only discuss an intramedullary locating technique, the gap
`checking device in accordance With the present invention is
`also suitable for extramedullary locating techniques.
`Thus, While there have been shoWn, described, and
`pointed out fundamental novel features of the invention as
`applied to a preferred embodiment thereof, it Will be under
`stood that various omissions, substitutions, and changes in
`the form and details of the devices illustrated, and in their
`operation, may be made by those skilled in the art Without
`departing from the spirit and scope of the invention. For
`example, it is expressly intended that all combinations of
`those elements and/or steps Which perform substantially the
`same function, in substantially the same Way, to achieve the
`same results are Within the scope of the invention. Substi
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`tutions of elements from one described embodiment to
`another are also fully intended and contemplated. It is also
`to be understood that the draWings are not necessarily draWn
`to scale, but that they are merely conceptual in nature. It is
`5 the intention, therefore, to be limited only as indicated by the
`scope of the claims appended hereto.
`What is claimed:
`1. A method of shaping a femur preparatory to implanting
`a knee prosthesis having respective femoral and tibial
`components, said method comprising the steps of:
`applying a gap checking device to the distal end of the
`femur prior to resection, the thickness of the device
`corresponding in a predetermined Way to the thickness
`of said femoral and tibial components;
`checking the gap; and
`shaping the distal end of the femur for the purpose of
`receiving the femoral component of said knee prosthe
`sis after the gap has been checked.
`2. A method according to claim 1, Wherein said gap
`checking device is referenced to epicondyles of the knee.
`3. A method according to claim 1, Wherein said shaping
`step comprises passing a cutting device through slots in said
`gap checking device.
`4. A method according to claim 3, further comprising the
`step of fastening a slot extender to said gap checking device.
`5. A method according to claim 4, Wherein said shaping
`step comprises passing a cutting device through slots in said
`gap checking device and said slot extender.
`6. A gap checking device for checking ligament balance
`prior to resec