WO1997030640A1

WO1997030640A1 - Distal femoral cutting guide apparatus

Info

Publication number: WO1997030640A1
Application number: PCT/US1997/002776
Authority: WO
Inventors: Scott Elliott; Jennifer J. Lackey; Gregory C. Marik; Brian Schumacher; Leonard J. Tokish, Jr.
Original assignee: Smith & Nephew, Inc.
Priority date: 1996-02-21
Filing date: 1997-02-21
Publication date: 1997-08-28
Also published as: US5720752A; AU1968997A

Abstract

A distal femoral sizing instrument (90) includes an intramedullary rod (19) for referencing the patient's intramedullary canal. A valgus module (95) mounts to the intramedullary rod at a bore (97) of the valgus. The bore of the module has a slant with respect to the flat reference surface of a valgus block. The module slidably connects to the block (91). The valgus block (91), referencing guide (92, 93), and stylus (94) (for connecting the valgus block and cutting together) are removed as a unit before shaping of the distal femur. An indexing system includes a gauge having a series of openings (110-115) corresponding to 'anterior' referencing and to 'posterior' referencing. During anterior referencing, the gauge allows the surgeon to select the smaller size prosthesis if the size falls in between available sizes. In posterior referencing, the gauge allows the surgeon to select the larger size prosthesis if the gauge measures a size that falls in between available sizes.

Description

PISTAL PgMORAL CUTTIMG GUIDE APPARATUS

The present invention relates to surgical orthopedic cutting instruments, and more particularly relates to an improved cutting block apparatus for shaping the distal femur of a patient prior to the placement of a knee joint prosthesis. Even more particularly, the present invention relates to a distal femoral cutting block apparatus that allows a surgeon to select a knee prosthesis using an anterior or a posterior referencing technique when the anterior/ posterior dimension tails In between available inventory sizes (typically one or more millimeters apart in size).

In knee joint replacement surgery, the surgeon often replaces the distal femoral surface of the patient's knee with a curved metallic prosthesis. The prosthesis has a generally smooth continuous outer curvature that faces a corresponding component that is attached to the patient's tibia. The posterior surface of the femoral component is typically provided with a number of intersecting flat surfaces. A common femoral component of a knee prosthesis provides five intersecting flat surfaces. One of the surfaces is adapted to engage the anterior cortical surface of the femur. Another of the flat surfaces is adapted to face the posterior surface of the femur. Yet another surface is adapted to engage the distal end of the patient's femur. Additionally, a pair of chamfer surfaces form diagonally extending

surfaces which form an interface between the distal surface and the respective anterior and posterior surfaces.

A surgeon forms five (5) separate cuts on the patieπfs distal

femur in order to prepare the distal femur to receive the femoral prosthesis. One of the problems facing the surgeon is the proper

orientation of the cuts so that the prosthesis will fit the femur with the

correct orientation. One method of orienting a cutting guide is to

reference that cutting guide to a rod that is placed In the patient's intramedullary canal.

A number of patents have issued which disclose medical cutting instruments for use by orthopedic surgeons. Some of these cutting instruments relate to shaping of the distal femur or adjacent bone structure.

U.S. Patent No. 4,474,177 is an example of a cutting block instrument that references a cutting guide to an intramedullary rod

that is positioned in the patients intramedullary canal of the femur.

The Whtteside Patent 4,467,6^*01, entitled "Method And Apparatus For Shaping A Proximal Tibial Surface", provides a method and apparatus for preparing the proximal surface of a tibia to receive a proximal tibial prosthesis employing a reamer/alignment guide which is used to internally locate the central long axis of the tibia and a plateau planar which cooperatively engages with a guide handle

attached to the reamer/alignment guide to accomplish the shaping of the proximal tibial surface. The reamer/alignment guide has a rod portion extending into the interior of the tibial shaft whose central long axis corresponds with the central long axis of the tibia. The guide

handle is concentric with that rod portion such that the plateau planar assumes the proper alignment with respect to the central long axis of the tibia such that the proximal tibial surface is shaped relative to that axis in a simple and accurate manner.

European Patent Application No. 0 122 669 discloses a guide

for femoral neck osteotomy that comprises a longitudinal rod having

attaching structure at the lower end thereof for securing the rod to a femur at the greater trochanter. A transversely extending support arm is secured to the rod adjacent the lower end thereof, and a guide bar is connected to the support arm. The guide bar has at least one elongate planar surface disposed at an angle of 45° to the axis of the

rod. in use, the rod is aligned with the long shaft axis of the femur and attached to the femur at the greater trochanter. The rod is manipulated until the support arm and the long shaft axis of the tibia are disposed in the same plane. This procedure properly positions the elongate planar surface of the guide bar whereby an instrument in

engagement with that surface traverses the femoral neck at an angle of 45° to the long shaft axis of the femur.

Another Whiteβlde Patent No. 4,474,177 provides a method

and apparatus for preparing the distal surface of a femur to receive a distal femoral prosthesis employing an intramedullary reamer which is used to internally locate the central long axis of the femur, an

intramedullary alignment guide which is inserted into the space left in

the intramedullary canal upon removal of the reamer and at least one femoral surface modifying instrument which cooperatively engages with a guide handle attached to the intramedullary alignment guide to accomplish the shaping of the distal femoral surface. The intramedullary alignment guide has a rod portion extending Into the femoral intramedullary canal whose central long axis corresponds with

the central long axis of the femur. The guide handle is attached to

that rod portion at a preselected angle such that the shaping

instruments fixed thereto assume the proper alignment with respect to the central long axis of the femur such that the distal femoral surface

is shaped relative to that axis in a simple and accurate manner.

An improved triplanar knee resection system, disclosed in U.S. Patent 4,487,203, provides a system for preparing a knee joint for a prosthesis. The apparatus of the triplanar knee system includes a single guide member for use in resecting the distal femoral condyles, the proximal tibia, and the distal femur. The guide member

cooperates with a simplified set of instruments, including femur and

tibia guide rods, a tibia adaptor, a tibia bar, and a femur bar, for establishing equal flexion and extension gaps and triplanar resections. U.S. Patent No. 4,567,885 also provides an improved

triplanar knee resection system for preparing a knee joint for a prosthesis.

The Petersen Patent No. 4,567,886 discloses a spacer guide

for utilization in total knee surgery for establishing size of prosthesis and position of cuts for total knee replacement surgery includes a

generally L-shaped base member for attachment to the anterior femoral cortex of a prepared femur with a generally L-shaped adjustable support member adjustably secured to the base support member and a vertically positionable indicator slide having a squaring

jig for cooperative engagement and alignment with the cutting head of a tibia alignment and resection guide for squaring the tibia and femur and including indicator means for indicating the position of a tibia plateau cut and indicating the size and positioning for a distal femoral cut for indicating the sizing of the both the tibial and femoral

prostheses. The Kenna et a!. Patent No. 4,464,729 discloses a prosthetic

knee implanted after cutting the femur and tibia with the aid of instruments which include axial alignment guides and a series of

cutting jigs.

A method and apparatus for resecting a distal femoral surface

is disclosed in U.S. Patent No. 4,703,751 in which an intramedullary

rod is inserted through the distal surface of the femur and along the

femoral shaft access, leaving a protruding end; a jig is attached to the protruding end, the gig having a shaft for receiving the rod end and a

support plate attached to an end of the shaft and extending parallel to

the rod; attaching a reference bar to the shaft, the bar having a pair of opposing flanges and a central opening which receives tiie shaft therethrough, and adjusting the bar on the shaft such that the flanges

contact condylar apices of the femur; fixing the jig relative to the

femur, attaching a cutting plate to the jig, the cutting plate having

blade guides thereon, pivoting the cutting plate relative to the jig such that the blade guides made a predetermined angle with the rod, and securing ti e cutting plate to tiie jig; and inserting a saw blade through the blade guides to make a resection of the distal femoral surface. In the preferred embodiment, the shaft includes a plurality of bores along its length, each sized to receive the rod therethrough so that the distance between the rod and the support plate may be adjusted to accept different sized anterior femur portions. Also in the preferred embodiment, the apparatus includes a plurality of guide bars, each

sized to space the blade guides a predetermined distance from the condylar apices.

The Kaufman et al. Patent No. 4,721,104 relates to a surgical

apparatus for providing an accurately recess in a distal femoral

surface for the intercondylar stabilizing housing of a posterior- stabilized knee implant prosthesis which apparatus comprises a template having a bottom surface which is adapted to be placed in an

aligning relationship with the flat surface of a distal femur which has been partially shaped to receive the femoral component of a posterior-stabilized knee implant prosthesis and a U-shaped slot passing through the template where the slot is of substantially the

same size and shape as the outer periphery of the intercondylar stabilizing housing present on the femoral component to be implanted

and a drilling means, preferably in the form of an endmill cutter, having a stop means thereon and the drilling means closely engages

tiie sides of the U-shaped slot in the template so that the drilling means can be passed through the U-shaped slot until the stop means contacts a surface of the guide and is then drawn along the slot to

create a precisely shaped and aligned recess in the femur for receipt of the intercondylar stabilizing housing, in a more preferred

embodiment, the template is composed of a drilling means guide which fits over a femoral trial prosthesis which is used for trial reductions after the drill guide is used and removed.

The Russell et al. Patent No, 4,722,330 relates to distal femoral surface shaping guide for mounting on a intramedullary alignment guide which references the central long axis of the femur in

shaping the distal femoral surface and a method for shaping the distal

femur using the shaping guide. The alignment is adjustable relative to the surface of the anterior femoral cortex to insure that the anterior aspect of the distal femoral condyles is resected relative to that surface and, preferably, at the same level as that surface. The

alignment guide provides a main body which remains attached to the intramedullary alignment guide throughout the entire shaping of the

distal femur.

An improved tibial cutting jig is disclosed in U.S. Patent No. 4,736,737, provided for use in obtaining accurate tibial resection in the course of a total knee prosthesis implantation procedure. The tibial cutting jig includes a base for sliding reception onto an intramedullary alignment rod preiπβtalied generally along the longitudinal axis of the tibia. The base Includes laterally extending θ outriggers carrying removable measurement keys of selected size for

spacing the base above the tibial plateau by a selected dimension. An anterior saw guide depends from the base and is thus positioned relative to the tibial plateau in accordance with the sizes of the measurement keys.

The Buechel et al. Patent No. 4,738,253 discloses a guide for a cutting device used to make a surgical cut in a first bone in desired

spatial relationship with a pre-existing cut in a second bone is

disclosed to include a means for contacting the pre-existing cut to

establish a reference for the desired spatial relationship and a body member engaging the means for contacting and including a guide

surface for establishing the desired spatial relationship and guiding a surgical cutting tool to cut the first bone in a plane which is not normally inclined with respect to the long axis of the first bone.

Another Buechel et al. Patent No. 4,738,254 discloses a positioner for positioning a surgical instrument which acts as a guide for a cutting instrument which produces a surgical cut in an anatomical structure; in one embodiment the positioner positions a

surgical instrument which acts as a guide for the cutting instrument at a predetermined position with respect to a previously resected surface whereby a further resection is made at a predetermined position wit respect to the previously resected surface; and in a further embodiment the positioner acts as a adaptor for a surgical instrument

which aids in producing surgical sections thereby allowing the surgical

instrument to produce surgical cuts at various predetermined positions relative to a previous surgical cut made at one of several levels.

The Dunn et al. Patent No. 4,759,350 provides a system of instruments for shaping the distal femur and proximal tibia surfaces to receive components of a knee prosthesis for knee replacement surgery. The system references the femur intramedullary channel with a femoral alignment guide to prepare the distal femur that, in turn, is a reference for several cutting guides for sequential attachment to

the femoral alignment guide and prepared bone surfaces whereby the

prepared distal femur is prepared to a fiat surface that is perpendicular to the patients mechanical axis with bone surfaces adjacent thereto sectioned to surfaces that are at right angles to that distal femur surface with chamfers therebetween to receive the femur

component of a knee prosthesis. A tibial cutting guide is provided for preparing the proximal tibia that consists of a sleeve, with a tube telescoped therein, the ends thereof including pin arrangements for connecting them into the tibia, between the ankle and near the proximal tibia, an open tube end of the tibial cutting guide to receive a rod telescoped therein that mounts a cutting guide platform and includes a screw arrangement for reieasably maintaining the road and tube together. The cutting guide platform includes a body with a saw guide slot formed therethrough to receive a saw blade to cut across the proximal tibia to form a surface for accommodating a tibial component of the knee prosthesis, the cutting guide platform body further including an arrangement for securing it to the tibia, slightly below the proximal tibia, and a tibial resection guide for setting a depth of cut across the proximal tibia.

U.S. Patent No. 4,773,407 issued to Petereen discloses a method and instruments for resection of the distal femur. The instruments include a distal femoral resector and a femoral alignment guide rod. The distal femoral resector is designed to be attached to the distal femur on a plane filed on the anterior femoral cortex. The distal femoral resector includes a feeler gauge laterally adjustable to adapt to the intercondylar notch of the particular patient and further includes a rotating rod having openings therethrough for fastening pins, which rotating rod is designed to facilitate the placement of the resector on the anterior femoral cortex in a flush manner. The femoral alignment guide rod includes a plate Insertable within a slot in the resector designed for the insertion of the cutting tool and further includes a pivotable rod which may be utilized to align tiie resector with the mechanical axis of the leg. The rod may then be pivoted to a position facilitating the insertion of a fastening pin through the resector. The method of operation using these instruments is also

disclosed.

U.S. Patent No. 4,892,093 issued to Zarnowski et al. discloses

a cutting guide for guiding a saw blade during the preparation of a femur for the implant of the femoral component of a knee prothesrβ indudes guide surfaces for enabling the cutting of all four of the anterior femoral cut, the posterior femoral cut, the anterior chamfer

and the posterior chamfer, fully and compieteiy, with certitude and

accuracy, while the cutting guide remains located and secured to the femur in a single position on a transverse surface located along the

distal femur.

U.S. Patent No. 4,907,578 relates to an improved method and

instruments for a resection of the distal femur. The parent application disdoβes a femoral alignment guide/rod induding a plate insertable within a guide slot in the resector which is also used for the guided

insertion of a cutting tool.

The Whiteside et al. U.S. Patent No. 4,935,023 relates to a

distal femoral surface shaping guide for mounting on an intramedullary alignment which references the central long axis of the femur in shaping the distal femoral surface and a method for shaping the distal femur using that shaping guide with particular applicability

for shaping one condyie for attachment of a unicoπdylar prosthesis.

The Bowman et al. U.S. Patent No. 4,952,213 disdoses an apparatus for placing a bone cutting saw cutting guide adjacent a

proximal surface of a human tibia bone having an elongated rod inserted Into the tibia for clampingly supporting a rotating bar on the

central longitudinal axis of the tibia bone. The bar being extended from the rod and connected to a pivot device which in turn is

connected to a support arm that holds a saw cutting guide against a proximal portion of the tibia bone. The rotation angle of the rod

determining the medial-lateral iπdination of the saw cutting guide and the pivot device determining the anterior-posterior iπdination of the

saw cutting guide. The support ami is adjustable in length to determine the height of the saw cutting guide.

The Dunn et al. U.S. Patent No. 4,959,066 provides an

osteotomy guide assembly for femoral neck osteotomy and includes a saddle locator assembly and a saw guide attachment. The saddle locator assembly indudes a barrel-shaped locating device that locates the saddle region of the proximal femur. The barrel further indudes a transverse support bar extending from the barrel. The barrel is positioned over an intramedullary shaft which is temporarily positioned in and extends from the medullary canal of the femur. A saw guide is

used in conjunction with a saddle locator assembly. The saw guide is

attached to the support bar by a single locking means which provides for positional adjustment of the saw guide relative tot he support bar in

two directions, iπduding adjustment in the anterior-posterior direction

along the transverse support bar and axially along the femur via a

post which extends from the saw guide.

The Whiteside et al. U.S. Patent No. 5,002,545 provides a

shaping guide to permit accurate shaping of the tibial plateau while saving the anterior cruciate ligament. An alignment rod is located anterior to the anterior cruciate ligament and along the anterior cortex of the intramedullary canal of the tibia provides points of reference for

all shaping operations. The shaping guide is adjustable with respect to the handle portion of the rod so that the amount of resection of the tibial plateau can be controlled readily by the surgeon by raising or

lowering of the cutting guide surfaces for resection of the tibia.

WO95/13034 describes a distal femoral cutting guide which in udes a gauge for measuring the size of prosthesis using either anterior or posterior referencing. The cutting guide indudes a valgus module which is fitted onto an intramedullary guide rod and the remaining parts of the cutting guide and sizing apparatus are

subsequently fitted as required.

The present invention provides an improved method and

apparatus for combined anterior and posterior referendng in the

shaping of a patients distal femur using a cutting and sizing apparatus.

According to the invention, an orthopaedic surgical instrument

for preparing a patient's distal femur to receive a femoral prostiiesis comprises: a) an intramedullary rod which is adapted to be inserted at one end into the patients intrameduilariy canal; b) a valgus block member having posterior paddles for engaging the posterior condyles of a patient's distal femur and a

surface for engaging the patient's distal femur, c) a valgus collet which indudes a bore which is

sized and shaped to receive the intramedullary rod. d) valgus attachment means for removably securing said valgus collet to said valgus block member. e) a guide member which is adapted to engage said

valgus block and to slide in relation thereto, said guide member comprising attachment means for removably attaching either a sizing

instrument or a cutting guide to said guide member.

f) wherein indicia are provided upon tiie assembly of valgus block and guide member for measuring the distal femur to

enable a suitable prosthesis size to be selected by reading the indicia.

The valgus block preferably indudes a flat surface for engaging the distal end of a patient's femur. Preferably at least one

bone spike extends from the flat surface for insertion into the distal

surface of the femur.

The bore in the valgus coRet is, in use, i.e. when secured to the

valgus block, preferably angled with respect to the anatomical axis of the femur. In order to achieve this, the bore in the valgus collet is preferably angled with respect to the longtudinal axis of the valgus collet. Since the valgus collet is removably securable to the valgus block, several interchangeable valgus collets may be provided each having a bore which is angled at a different angle so that a valgus collet which has a suitable angle may be selected to suit each patient.

A preferred form of valgus collet indudes a pair of grooves which slidably engage a part of the valgus block for attachment thereto. The valgus block preferaby includes a slot into which the valgus collet may slide with the sides of the slot engaging the collet or grooves in the collet.

The valgus collet may optionally indude means to attach an instrument for removing the valgus block from the patients femur. These means may comprise grooves for engaging the removing

instrument.

The valgus block and guide member are slidable with respect to each other and together form a sizing instrument to measure the thickness of the patients distal femur so that the correct size of

femoral prosthesis may be selected. The assembly of guide member and valgus block indude indicia which indicate the correct size of

prosthesis to be selected. Sliding the guide member towards or away from the valgus block indicates different sizes of prosthesis which

correspond to the distance between the posterior paddles and a sizing instrument which attaches to the guide member and which indudes a surface for engaging the anterior surface of the patient's femur. The sizing instrument preferably comprises a stylus which is arranged to engage the anterior cortical surface of the femur. The guide member may be either an anterior referencing guide

or a posterior referendng guide. The anterior and posterior referencing guides differ from each other in that the gauge is arranged

to indicate different sizes if the thickness of the femur corresponds to a size which is between the standard sizes of the prosthesis available.

For an anterior referencing technique, the surgeon reads the size of the femoral prosthesis that is needed from the assembly of

components that are available. If the size however falls between sizes, the block is pinned into place in the hole of indida referring to the smallest component.

If a posterior referendng technique is used, the surgeon reads

the size of the component needed from the assembly of components. If the size falls between sizes, the surgeon slides the posterior

reference guide anteriorly until the indicia indicate the larger size.

When using anterior referendng, the surgeon makes the cut on the anterior surface. More tissue will be removed from the posterior surface when anterior referendng because the surgeon selected the

smaller prosthesis size.

The guide member preferably includes holes which correspond to the size iπdidas which may be aligned with a hole in the valgus block so that a pin may be inserted through holes in both the valgus block and guide member when a particular size has been indicated.

The pin serves to secure the block and guide together and to the bone so that the guide may be used to make a cut on the distal femur.

The guide member preferably includes a cutting guide slot for

guiding a cutting blade when making such a cut. The slot is preferably arranged such that it is perpendicular to the surface of the

valgus block which engages the patient's distal femur when in use. This arrangement provides a slot which is an anterior cutting guide slot to assist a surgeon in making an anterior cut to the distal femur which is generally parallel to the axis of the intramedullary alignment

rod.

The guide member comprises attachment means for

removably attaching a sizing instrument (e.g. a stylus as mentioned above) or a cutting guide instrument such as a distal cutting block to guide the surgeon's blade in making a distal cut to the femur. Preferably the attachment means comprises a quick-release means to

enable the attached instrument to be released from the guide member quickly and easily. The attachment means may comprise a detent means in which a protrusion or latch located on either the guide member or the instrument can engage a groove or recess on the other part. The protrusion or latch may be reieasable from the groove

or recess by an operating cam or button. Preferably the protrusion or latch is sprung Into its groove-engaging position.

The instrument may comprise a cutting guide which is

attachable to the guide member and which includes a cutting guide slot for guiding a blade making the distal cut to the patients femur.

The cutting guide preferably includes attachment means which cooperate with the attachment means of the guide member to provide a quickly reieasable attachment between the guide member and the cutting guide. The cutting guide Is preferably βlidable proxlmally and/or distally with respect to the guide member.

A further cutting guide may be provided which has a flat

surface to be placed upon the cut distal surface of the patient's distal

femur and which indudes slots for guiding the surgeon in making

anterior, posterior, anterior chamfer and/or posterior chamfer cuts to

the femur. The anterior and posterior slots are preferably angled at between 90 and 95° to the flat distal surface whilst the anterior and

posterbr chamfer guide slots are angled diagonally with respect to the

flat distal surface. One form of invention will now be further described, by way of

example only, with reference to the accompanying drawings.

FIGURE 1 is a perspective exploded view of one embodiment

of the apparatus of the present invention showing a sizing and cutting

guide;

FIGURE 2 is a partial perspective view of the sizing and cutting

guide of Figure 1;

FIGURE 3 is a perspective view of the valgus block and valgus

module portions of the guide of Figure 1 ;

FIGURE 4 Is a plan view of the posterior referencing sizing

guide portion of the embodiment of Figure 1;

FIGURE 5 Is a partial view of an embodiment of the apparatus of the present invention illustrating the valgus module portion thereof, FIGURE 6 is an end view of the valgus module of Figure 5;

FIGURE 7 is another end view of tiie valgus module of Figure

5;

FIGURE 8 is a side elevational view of the valgus module of Figure 5; FIGURE 9 is a top view of the valgus module of Figure 5; and

FIGURE 10 is a bottom view of the valgus module of Figure 5. plan view FIGURE 11 shows a distal cutting guide for use with the instrument of fig 1.

FIGURE 12 is a perspective view of the distal cutting guide of fig 10 shown in a different position.

FIGURE 13 is a further perspective view of the distal cutting

guide of fig 10

FIGURE 14 is a plan view of an anterior-posterior cutting guide

FIGURE 15 is a plan view of an anterior-posterior cutting guide

from the tower surface FIGURE 16 is a side view of an anterior-posterior cutting guide

on the femur showing the cuts made.

FIGURE 17 is a view of the femur and intramedullary rod.

Figures 1-4 show generally an embodiment of the apparatus of

the present invention in the form of instalment 90. The sizing Instrument 90 indudes a valgus block 91 that forms a sliding connection with either of posterior or anterior referendng guide. In

Figure 1, the anterior referendng guide is designated as 92. In Figure 4, a posterbr referencing guide 93 is shown. Either the anterior 92 or

posterior 93 referendng guides can attach to stylus 94 that is used to engage the anterior femoral cortex during sizing. Valgus collet or module 95 slides into a slot 96 provided on valgus block 91 as shown in Figure 3. The module 95 provides a

bore 97 that registers upon an intramedullary rod mounted in the intramedullary canal of the patients femur F (see Figure 17 ). In the

embodiment of Figures 2-4, the bore 97 is angled with respect to the longitudinal or mechanical axis of the femur. In Figure 3, the axis 96

tracks the central longitudinal axis of bore 97. The reference line 99 is a line parallel to the longitudinal axis of the patients femur.

In Figures 1 and 2, there can be seen the combination of

valgus block 91 and anterior referendng guide 92. These two instruments 91 and 92 slide with respect to one another. The sliding connection between valgus btock 91 and either anterior 92 or posterior 93 referendng guide is made possible by a pair of parallel

flange portbns 116, 117 of the particular anterior 92 or posterior 93 referencing guide. The flanged portions 116, 117 slide in a pair of opposed slots 118, 119 respectively of block 91.

During anterior referencing, the assembly of block 91, valgus collet 95, guide 92, and stylus 94 are placed upon the patients distal

femur. Spikes 100, 101 can be used to affix the block 91 firmly to the distal femur F once the desired position of the block is fixed upon the

distal femur using paddles 102, 103 and valgus module 95 that fits upon rod 19. The paddies 102, 1 3 engage the posterior condyles of

the distal femur F. The surgeon engages the spikes 100, 101 into the distal femur F once the paddies 102, 103 have engaged at least one of the condyles of the femur F and the intramedullary rod 19 fits the bore 97 of valgus module 95.

Once the valgus block 91 has been firmly mounted to the distal

femur F using spikes 100, 101 , the surgeon then attaches stylus 94 to anterior referendng guide 92 at its socket 104. The stylus 94 provides a pointer 105 and a body or flange portion 106. The body portion 106 carries quick release connector 107 that attaches to socket 104 using a detent locking mechanism 108 for example. Once

the pointer 105 has engaged the anterior femoral cortex and the paddles 102, 103 have contacted the condylar portbns of the patients femur, the user can then read a size from the indicia 109

carried by the sizing guide 92.

The detent locking mechanism of the quick release connector

comprises a bail or latch within connector 107 which is arranged to extend through a hole 108 inthe sidewall of the connector. A spring urges the ball or latch towards this position. Push button 128 is connected to a release member extending within the connector which, on depression of button 128 moves the ball or latch away from hole 108 so that it no longer extends through the hole. Button 128 is also

sprung into Its non-operated position. When connector 107 is

inserted into socket 1 4, the part of the ball or latch which extends through hole 108 engages a groove or recess within socket 104 and Is urged into engagement therewith by its spring. When button 12B is depressed, the ball or latch is moved inwardly away from hole 108 and out of engagement with the groove within socket 104 so that styles 105 may be quickly released from guide member 92 or 93.

In Figure 2, the sizes 3, 4, 5, 6, 7, and 8 are provided adjacent

openings 110-115 in the anterior referendng guide 92. This set of indida 110-115 tell the surgeon the size prosthesis to select for the patient's distal femur. The holes 110-115 in flanges 116 and 117 line up in turn with slots 129 and 130 in the valgus block 91. Slot 129 is

arranged to align with holes 110, 112 or 114 while slot 130 may be aligned with holes 111 , 113 or 115. The provision of a slot 129 or 130 to align with indexing holes 110-115 enables the hole corresponding to the smaller size of prosthesis to be selected if the femur should fall

between two different sizes, which is desirable when the prosthesis is selected by the anterior referencing technique using anterior referencing guide 92. When the guide 92 has been slid into valgus block 91 until pointer 105 contacts the anterior cortex and paddles 102 and 103 contact at least one of the posterior femoral condyles, a bone pin may be inserted through one of holes 110-115 and either slot 129 or slot 130 to anchor the instrument to the bone and guide

member 92 to valgus bbck 91. The surgeon may then make a cut to the anterior part of the femur using slot 131 as a cutting guide slot

When the surgeon prefers to use posterior referencing, he

uses posterior reference guide 93, shown in fig 4, instead of anterior reference guide 92. Flanged portions 116 and 117 of posterior

reference guide 93 engage slots 118 and 119 of block 91 and are slidable therein. Posterior reference guide also indudes a socket 104 by means of which stylus 94 or a cutting guide may be connected to guide 93.

Holes 135-137 and 138-140 are located along the right-hand side of flanged portions 116 and 117 respectively of the posterbr

referencing guide 93 to align with holes 141 and 142 in the base of

the valgus block 91. As the guide 93 and valgus block 91 are slid together until pointer 105 engages the anterior cortical bone and paddles 102 and 103 engage the femoral condyles, holes 135-137 and 138-140 line up in turn with holes 141 and 142 respectively. The

correct size of prosthesis is indicated by the hole which is aligned with a hole 141 or 142 such that a bone phi may be passed through both a

hole 135-140 and a hole 141 or 142. Because holes 141 and 142 are not slot-shaped, the surgeon must select the larger size prosthesis if the sizing indicates that the femur falls beiween two sizes.

Valgus module 95 is shown more particularly in Figures 5-10.

Valgus module 95 has opposed surfaces 120, 121 that define an acute angle therebetween. The module includes lower parallel grooved portions 122, 123 and upper parallel grooved portions 124. 125. These grooved portions 122 & 123 can be used to mount module 95 within slot 96 of block 91. The grooves 122, 123 engage the rails 126, 127 of block 91 as shown in Figure 3. Grooves 124 and 125 are provided to engage a removal instrument to remove the parts 91,92, 94, and 95 from femur F.

A distal cutting guide 145 is shown in figs 11 - 13. The cutting block

portion 146 of guide 145 is slidable upon a flange portion 147 of the cutting guide. The flange portion 147 of the cutting guide includes

connector 107 to connect to the socket 104 of guide member 92 or

93 by detent mechanism 108 as described previously. Push button 128 is operable to disconnect the cutting guide 145 from guide

member 92 or 93 as described previously. The guide 145 includes a slot 148 through which the surgeon may pass a cutting instrument to effect a distal cut on the patient's distal femur. When distal cutting guide 145 is assembled to the valgus block and guide member assembly, by connecting connector 107 into socket 1 4, the surface 149 of cutting guide 145 is brought into engagement with the cut anterior surface of the femur which has been formed by the cut made through the slot 131. The cutting bbck portion 146 may then be moved proximally or distally along flange portion 147 to its desired position and the surgeon then makes the distal cut through slot 148.

When the distal cut has been made, the whole assembly of block 91, guide member 92 or 93, valgus module 95 and cutting guide 145 is removed from the femur by means of grooves 124 and 125 of the valgus module 95.

An anterior-posterior cutting block may then be attached to the cut distal surface of the femur to guide the surgeon in making the posterior cut, the final anterior cut and the anterior and posterior chamfer cuts. A suitable cutting block is shown in figs 14 - 16. The block 76 indudes a fiat lower surface 80 which engages the cut distal surface of the femur. The block 76 is held In place on the femur by means of bone pins 85 inserted through holes 77 of the block 76. Block 76 includes four cutting guide slots 81 - 84. Slot 81 is used to

make the posterior cut on the femur. Slots 82 and 83 are used to make the anterior and posterior chamfer cuts respectively. Slot 84 is an anterior cutting guide slot which is angled usually between 90 and 95 degrees, (e.g. 93 degrees) to the flat surface 80 of the

cutting guide. This anterior slot may be used to make a final anterior cut to the surface to provide the correct alignment of the anterior surface with the other cut surfaces to fit the femoral prosthesis which is to be implanted on the femur. Fig 17 shows schematically the

cuts made made by a flat cutting saw blade 48.

The instrument described herein provides an Improved surgical sizing and cutting instrument which has fewer parts than some prior

instruments and which may be to some extent preassembled using a selected one of a variety of valgus modules. The quick release mechanism for attaching the sizing stylus or cutting guide also assists with the use of the instrument

Claims

1. An orthopaedic surgical instrument for preparing a patients distal femur to receive a femoral prosthesis, the femur having anterior and posterior distal femoral surfaces, comprising:

a) an intramedullary rod for referencing the patients intramedullary canal by aligning the rod with the patients intramedullary canal;

b) a valgus block member having posterior paddles for engaging the posterior condyles of a patient's distal femur and a surface for engaging the patients distal femur;

c) a valgus collet including a bore sized and shaped to receive the intramedullary rod;

d) valgus attachment means for removably securing said valgus collet in engagement with the valgus block;

e) a guide member which is adapted to engage said valgus block and to elide in relation thereto, said guide member comprising attachment means for removably attaching either a sizing instrument or a cutting guide to said guide member;

f) wherein indicia are provided upon the assembly of valgus block and guide member for measuring the distal femur to enable a suitable prosthesis size to be selected by reading the indicia.

2. The instrument of claim 1 further comprising means for locking the valgus block and guide member together.

3. The instrument of either claim 1 or claim 2 wherein the block and guide member define a gauge for measuring the thickness of the patient's distal femur between the anterior and posterior surfaces thereof.

4. The instrument of any preceding claim, wherein said guide member comprises either an anterior or a posterior referencing sizing guide, each having indicia for enabling a surgeon to determine the thickness of the patient's distal femur, said indicia including independent anterior and posterior referencing indicia, allowing the surgeon to measure the distal femur by selecting theanterior or the posterior referencing indicia.

5. The instrument of any preceding claim further comprising a sizing instrument comprising a stylus member which is adapted to be removably connected to with the guide member, the stylus comprising a body with connection means thereon for removably attaching the stylus member to the guide member.

6. The instrument of any preceding claim wherein the valgus collet slideably affixes to the valgus block.

7. The instrument of claim 6 wherein said attachment means comprise a pair of grooves in said valgus collet for engaging a part of said valgus block for forming a sliding engagement therewith.

8. The instrument of any preceding claim wherein the valgus collet has an angled bore.

9. A surgical instrument as claimed in any preceding claim wherein said valgus collet comprises means for attaching a further instrument for removing said valgus block from the patient's femur.

10. A surgical instrument as claimed in claim 9 wherein said means comprises a pair of grooves for engaging a part of said further instrument.

11. The instrument of any preceding claim wherein the guide member attachment means comprises a socket and said further sizing instrument or cutting guide comprises a part which is adapted to fir into said socket to attach said instrument to said guide member.

12. A surgical instrument as claimed in any preceding claim wherein said attachment means on said guide member for attaching a sizing instrument or cutting guide comprises detent means.

13. A surgical instrument as claimed in any preceding claim wherein said attachment means comprise a quick - release mechanism for removing said sizing instrument or cutting guide from said guide member.

14. A surgical instrument as claimed in any preceding claim further comprising a distal cutting guide which is removably attachable to said guide member, said distal cutting guide including a surface for engaging the anterior surface of a patients distal femur and a slot extending perpendicular to said surface for guiding a blade to make a transverse cut on the distal femur which is at substantially ninety degrees to said anterior- engaging surface.

15. A surgical instrument as claimed in any preceding claim further comprising an anterior-posterior cutting guide including anterior and posterior guide slots for guiding a cutting blade to make anterior and posterior cuts on the patient's femur.

16. A surgical instrument as claimed in claim 15 wherein said anterior-posterior cutting guide includes guide slots which are angled with respect to said anterior and posterior guide slots for guiding a cutting block to make chamfer cuts on the patient's distal femur.

17. A surgical instrument kit for use in preparing a patient's distal femur to receive a femoral prosthesis comprising a) an intramedullary rod which is adapted to be inserted at one end into the patient's intramedullary canal;

b) a valgus block member having posterior paddles for engaging the posterior condyles of a patient's distal femur and a surface for engaging the patient's distal femur;

c) a plurality of valgus collets which each include a bore which is sized and shaped to receive the instramedullary rod.

d) valgus attachment means for removably securing one of said valgus collets to said valgus block member.

e) a guide member which is adapted to engage said valgus block and to slide in relation thereto, said guide member comprising attachment means for removably attaching either a sizing instrument or a cutting guide to said guide member.

18) A surgical instrument kit as claimed in claim 17 further comprising a distal cutting guide which is removably attachable to said guide member.

19) A surgical instrument kit as claimed in either claim 17 or claim 18 further comprising an anterior-posterior cutting guide comprising anterior and posterior guide slots for guiding a cutting blade to make anterior and posterior cuts on a patient's distal femur.

20) A surgical instrument kit as claimed in claim 19 wherein said anterior-posterior cutting guide includes guide slots which are angted with respect to said anterior and posterior guide slots for guiding a cutting blade to make chamfer cuts on the patients distal femur.

21) A surgical instrument kit as claimed in any of claims 17-20 further comprising a cutting guide having guide slots which are, in use, angled with respect to the axis of the femur for guiding a cutting blade to make chamfer cuts to the distal femur.

22) A surgical instrument kit as claimed in any of claims 17-21 wherein each said valgus collect includes a bore which is angled with respect to the axis of said valgus collet and wherein said plurality of valgus collets include at least two valgus collets wherein said bore is angled differently from each other.