# Patent

## Title
Femoral guide for implanting a femoral knee prosthesis

## Abstract

Disclosed is a method of selecting a femoral prosthetic for implantation relative to a femur using a femoral sizing guide. An extension portion of the femoral sizing guide is placed adjacent to a posterior condyle surface of the femur. A stylus is located proximate to an interior condyle surface of the femur. A first actuator disposed between the extension portion and a base portion is moved to rotatably displace the extension portion with respect to the base portion until the stylus is centrally located on top of the interior condyle. A measurement of the femur is identified with the sizing guide based on a relative location of the stylus, the extension portion and the base portion. A femoral prosthesis is selected based on the measurement.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 12/367,903 filed on Feb. 9, 2009, which is a continuation of U.S. patent application Ser. No. 10/730,456 filed on Dec. 8, 2003, issued on Feb. 10, 2009 as U.S. Pat. No. 7,488,324. The entire disclosure of the above application is incorporated herein by reference.


FIELD
The present disclosure relates generally to the alignment hardware used in a surgical procedure and, more particularly, to an alignment hardware used in the implantation of a femoral prosthesis.
BACKGROUND
The implantation of knee prosthetics require the distal end of the femur to be prepared to receive a femoral component of the knee prosthetic. This preparation generally requires the resection of various surfaces of the femur to ensure the proper coupling of the knee prosthetic to the resected surfaces. Various guides are known to assist the surgeon in locating cutting blades used to resect the femur.
The location and size of cuts to the femur generally correspond to internal surfaces within the femoral prosthetics. The location of the surfaces may change depending on the size of the prosthetics used. To this end, a femoral sizing guide is used to determine the size of the femoral prosthetic which will be implanted at the implantation site of the particular patient.
Femoral knee prosthesis are made available in a range of standard sizes. A femoral sizing guide is used to assist the selection of a standard sized femoral knee prosthetic which will best fit the requirements of a particular implantation site. The size and orientation of the implant is a function of kinematic and biomechanical considerations. In this regard, the femoral sizing guide is used to measure the condyles of the patient's femur and specifies the proper location of guiding apertures within the femur. As such, it is necessary to provide a reliable femoral sizing guide which is configured to allow the surgeon to determine the size and proper orientation of the femoral implant.
SUMMARY
Disclosed is a method of selecting a femoral prosthetic for implantation relative to a femur using a femoral sizing guide. An extension portion of the femoral sizing guide can be placed adjacent to a posterior condyle surface of the femur. A stylus can be located proximate to an interior condyle surface of the femur. A first actuator disposed between the extension portion and a base portion can be moved to rotatably displace the extension portion with respect to the base portion until the stylus is centrally located on top of the interior condyle. A measurement of the femur can be identified with the sizing guide based on a relative location of the stylus, the extension portion and the base portion. A femoral prosthesis can be selected based on the measurement.
According to additional features, the stylus can be translated along an axis relative to the base portion. A superstructure associated with the stylus can be translated along the axis relative to the extension portion. Translating the stylus can include rotating a second actuator causing a threaded distal end of the second actuator to rotate within a threaded hole of the base portion. Moving the first actuator can include rotating a worm gear disposed between the extension portion and the base portion. Identifying the measurement can include identifying a first gradation of a plurality of indexing gradations provided on a worm gear mount of the worm gear. Identifying the measurement can further include identifying a second gradation of a series of gradations provided on the stylus. At least one retaining hole can be drilled into the femur while referencing drilling guides extending from the base portion.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.



BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
FIG. 1 represents a perspective view of the femoral sizing guide of the present disclosure;
FIG. 2 represents a front view of the femoral sizing guide shown in FIG. 1;
FIG. 3 represents a femoral sizing guide shown in FIG. 1 with the worm gear actuated;
FIG. 4 is a cross-sectional view of the worm gear mechanism shown in FIG. 2;
FIG. 5 represents a side view of the femoral sizing guide measuring a plurality of insert sizes;
FIG. 6 is a side view of the femoral sizing guide coupled to a resected femur;
FIGS. 7 and 8 are exploded views of a femoral measurement guide according to another embodiment of the present disclosure;
FIG. 9 is a modular adjustable foot portion shown in FIG. 7;
FIG. 10 is a base portion shown in FIG. 7; and
FIGS. 11 and 12 are modular superstructures shown in FIG. 7.



DETAILED DESCRIPTION
The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses.
Referring generally to FIGS. 1 and 2, a femoral sizing guide 10 according to the teachings of the present disclosure is shown. The femoral sizing guide 10 is generally formed of an extension portion 12, a base portion 14, a superstructure portion 16 having a corresponding graduated stylus 18, an actuator 20 disposed between the superstructure 16 and the base portion 14, and a worm gear 22. The femoral sizing guide 10 is configured to measure the size and general angular orientation of the condyles of a femur to allow a treating physician to interoperatively select a proper femoral prosthetic.
The feet 25 of the extension portion 12 use the posterior sides of the condylar surfaces as a reference. As the surfaces of the condyles can be degraded due to natural causes, their ability to function as a reference surface and, therefore, indexing plane can be degraded. As such, adjustability of the feet 25 can assist in the alignment of the sizing guide.
As best seen in FIGS. 2 and 3, the extension portion has a pair of feet 25 coupled to a central member 26. The extension portion 12 is pivotally coupled to the base portion 14 at a central pivot point 28 through a pivot axis 30. Further disposed between the extension portion 12 and the base portion 14 is a worm gear 22 which functions to rotate the extension portion 12 and corresponding feet 25 about the pivot axis 30 in a predetermined and repeatable fashion. The extension portion 12 further has a depending pin or flange 32 which defines a first portion of the worm gear 22.
The base portion 14 has a body 34 having a body pivot point 35 which corresponds to the pivot axis 30. A body 34 defines a support flange 38 having a support flange track 40 which is configured to interface with a superstructure track 41. Defined on a first side 36 of the body 34 is a threaded coupling portion 37. The threaded coupling portion 37 is configured to be coupled to the actuator 20. A second side 45 of the body 34 defines a worm gear mount 39. The worm gear mount 39 defines an aperture 43 and further has a plurality of indexing gradations which will be used by a treating physician to determine the amount of rotation of the feet 25 with respect to the base portion 14 about pivot axis 30. It should be noted that the pivot axis 30 is offset a predetermined distance from the transepicondylar axis of the femur.
The superstructure 16 has a pair of depending side flanges 42 and 44 which define drilling guides 46 and 48. The first depending side flange 42 further defines a coupling mechanism 50 which is shown in the form of an aperture to rotatably support and guide the second actuator 20. The superstructure 16 further has a holding mechanism 52 which defines an indexed slot 54 which slidably receives the graduated stylus 18. The holding mechanism 52 further defines a window 56 which displays graduations 58 of the graduated stylus 18.
As best seen in FIG. 3, the extension portion 12 can be rotated about the pivot axis 30 by the rotation of the first actuator or worm gear 22. In this regard, the worm gear 22 defines an arcuate slot 60 which is rotatable about a gear pivot point 62. The arcuate slot 60 slidably holds the fixed worm gear pin 32. The rotation of the arcuate slot 60 about the coupling point 62 causes the rotation of the extension portion 12 with respect to the base portion 14. Similarly, it causes rotation with respect to the superstructure 16 and the stylus 18. The worm gear has a system of associated graduations which allow a treating physician to categorize the necessary rotation of the measurement guide about the central pivot axis 30.
The actuator 20 functions to translate the superstructure portion 16 with respect to the extension portion 12 or the base portion 14. In this regard, the rotation of the actuator 20 causes a threaded distal end 64 of the actuator 20 to rotate within a threaded hole 66 in the coupling portion 37 of the base portion 14. This causes the superstructure portion 16 and stylus 18 to translate in a second axis 67 away from or toward the base portion 14 and associated feet 25 of the extension portion 12. The movement causes translation of the drill guides 46 and 48 with respect to the feet 25 and the resected femur.
FIG. 4 represents a cross-sectional view of the worm gear 22. As seen, the extension portion 12 has a depending pin 32 which interfaces with the arcuate slot 60 defined in a first rotating member 61. The rotating member 61 and associated handle portion 63 are rotatably coupled to the worm gear mount 39 of the base portion 14. The worm gear mount 39 has a plurality of gradations which indicate the relative rotations of the extension portion 12 with respect to the base portion 14 and associated superstructure 16.
Shown in FIGS. 5 and 6, the graduated stylus 18 rests against the anterior cortex of the femur at an anterior/posterior location. Angular adjustment of the extension portion 12 with respect to the base portion 14 is made by rotating the worm gear 22 and adjusting the actuator 20 so as to allow for the proper standard size femoral implant to be used. In this regard, the adjustments allow the surgeon to properly position the drilling guides 46 and 48 so as to allow a proper positioning of the guide holes (not shown). The holes drilled using the drilling guides 46 and 48 are used to position a cutting guide (not shown) which is used to make cuts to form surfaces which correspond to internal planar surfaces on the interior surface of the femoral prosthetic 80.
As shown in FIGS. 3, 5, and 6, the feet 25 of the extension portion 12 are positioned adjacent to the posterior side of the femoral condyles. The location of the tip of the stylus 18 is adjusted by sliding the stylus 18 within the index slot 54 of the holding mechanism 52. Further adjustment can be made by adjusting the position of the superstructure 16 with respect to the extension portion by rotating the actuator 20.
At this point, the worm gear 22 is rotated so as to centrally locate the tip of the stylus 18 on top of the interior condyle surface. The treating physician reads values from the graduated stylus 18, actuator 20, and indexed worm gear 22 to select the appropriate femoral prosthetic. A pair of retaining holes are then bore into the resected femur using the drilling guides 46 and 48.
FIGS. 7-12 represent a second embodiment of the present disclosure. Shown is a modular system which allows a treating physician to interoperatively assemble the femoral sizing guide 10b. This allows the treating physician to use a rotatable foot portion 25a or a non-rotatable foot portion 25b. Additionally, the treating physician can utilize varying types of superstructure 16a or 16b. 
FIGS. 7 and 8 represent an exploded view of the femoral sizing guide 10b according to the teachings of a second embodiment of the disclosure. Shown is a base portion 14a which defines a coupling mechanism for coupling either the first or second superstructure 16a or 16b to the top surface 84 of the base portion 14a. As shown, the coupling mechanism can take the form of an aperture 86 defined in the top surface 84 which is configured to fixably receive a post 88 formed on the superstructure 16a or 16b. The post 88 can optionally have a locking feature 90 which allows the post to be non-rotatably and yet releasably coupled to the base 14a. 
Additionally, the base 14a defines a second coupling mechanism 91 which is configured to couple the base 14a to either one of the rotatable foot portion 25a or the non-rotatable foot portion 25b. The coupling mechanism 91 is shown as an elliptical bore defined in the base 14a. The elliptical bore 91 corresponds to an elliptical coupling structure defined on the foot portions 25a or 25b. 
Components which are coupled to base portion 14a can be removed by releasing a spring loaded locking mechanism 92 defined on the elliptical structure on the foot portion 25a. It is envisioned the spring loaded locking mechanism 92 can be positioned on the base 14a. 
As shown in FIGS. 7, 8, and 10, the base 14a is configured to allow translation of the drilling guides 46 and 48 with respect to the foot portion 25a. Shown is a knob 94, which is coupled to an internal gear (not shown) which causes the relative translation. It is envisioned that the actuator shown in FIG. 1 can additionally be used to adjust the relative location of the superstructure portion 16 with respect to the foot portion 25a. 
As best seen in FIG. 9, the adjustable foot portion 25a has a rotational mechanism which allows for rotation of the feet 25 with respect to the coupling mechanism 91. In this regard, the adjustable foot portion 25a has an oval post 96, about which the feet 25 are rotatably coupled. As described above with respect to the first embodiment, rotation of the worm gear 22 causes rotation of the feet with respect to the base portion 14a. 
FIGS. 11 and 12 represent modular superstructure 16a and 16b. The superstructures are configured to be adjusted in a fashion which allows the treating physician to measure anatomical features of a resected bone. The location of the tip of the stylus 18 can be measured by vertical and horizontal adjustment of the superstructure 16b or by angular movement shown in superstructure 16a. 
The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.

## Claims

1. A method of selecting a femoral prosthetic for implantation relative to a femur using a femoral sizing guide, the method comprising:
placing an extension portion of the femoral sizing guide adjacent to a posterior condyle surface of the femur, the extension portion having a base portion pivotally connected thereto;
locating a stylus proximate to an interior condyle surface of the femur;
moving a first actuator disposed between the extension portion and the base portion to rotatably displace the extension portion with respect to the base portion until the stylus is centrally located on top of the interior condyle;
identifying a measurement of the femur with the sizing guide based on a relative location of the stylus, the extension portion and the base portion; and
selecting a femoral prosthesis based on the measurement;
wherein moving the first actuator comprises rotating a worm gear disposed between the extension portion and the base portion.

2. The method of claim 1, further comprising: translating the stylus along an axis relative to the base portion.

3. The method of claim 2 wherein translating the stylus further comprises translating a superstructure associated with the stylus along the axis and relative to the extension portion.

4. The method of claim 3 wherein translating the stylus comprises rotating a second actuator causing a threaded distal end of the second actuator to rotate within a threaded hole of the base portion.

5. The method of claim 2 wherein translating the stylus comprises translating the stylus relative to drill guides extending from the superstructure.

6. The method of claim 1 wherein identifying the measurement comprises identifying a first gradation of a plurality of indexing gradations provided on a worm gear mount of the worm gear.

7. The method of claim 6 wherein identifying the measurement further comprises identifying a second gradation of a series of gradations provided on the stylus.

8. The method of claim 1, further comprising:
drilling at least one retaining hole into the femur referencing drilling guides extending from the superstructure.

9. A method of selecting a femoral prosthetic for implantation relative to a femur using a femoral sizing guide, the method comprising:
placing an extension portion of the femoral sizing guide adjacent to a posterior condyle surface of the femur, the extension portion having a base portion pivotally connected thereto;
locating a stylus extending from a superstructure proximate to an interior condyle surface of the femur;
sliding the stylus within an index slot of the superstructure to position a tip of the stylus relative to the interior condyle surface of the femur;
rotatably displacing the extension portion with respect to the base portion until the stylus is centrally located on top of the interior condyle by moving a first actuator;
translating a superstructure associated with the stylus along an axis and relative to the extension portion by rotating a second actuator, the second actuator is laterally spaced apart from the axis;
identifying a measurement of the femur with the sizing guide based on a relative location of the stylus, the extension portion and the base portion; and
selecting a femoral prosthesis based on the measurement.

10. The method of claim 9 wherein rotatably displacing the extension portion comprises moving a first actuator disposed between the extension portion and the base portion.

11. The method of claim 10 wherein translating the superstructure comprises rotating the second actuator causing a threaded distal end of the second actuator to rotate within a threaded hole of the base portion.

12. The method of claim 10 wherein translating the superstructure moves drill guides relative to the base portion.

13. The method of claim 10 wherein rotatably displacing the extension portion comprises rotating a worm gear disposed between the extension portion and the base portion.

14. The method of claim 13 wherein identifying the measurement comprises identifying a first gradation of a plurality of indexing gradations provided on a worm gear mount of the worm gear.

15. The method of claim 14 wherein identifying the measurement further comprises identifying a second gradation of a series of gradations provided on the stylus.

16. The method of claim 8, further comprising:
drilling at least one retaining hole into the femur referencing drilling guides extending from the superstructure.

17. A method of selecting a femoral prosthetic for implantation relative to a femur using a femoral sizing guide, the method comprising:
placing an extension portion of the femoral sizing guide adjacent to a posterior condyle surface of the femur, the extension portion having a base portion pivotally connected thereto;
locating a stylus extending from a superstructure proximate to an interior condyle surface of the femur;
sliding the stylus within an index slot of the superstructure to position a tip of the stylus relative to the interior condyle surface of the femur;
rotating a worm gear disposed between the extension portion and the base portion to displace the extension portion with respect to the base portion until the stylus is centrally located on top of the interior condyle;
translating the stylus relative to the base portion;
identifying a measurement of the femur with the sizing guide based on a relative location of the stylus, the extension portion and the base portion; and
selecting a femoral prosthesis based on the measurement.

18. The method of claim 17 wherein translating the stylus comprises rotating an actuator causing a threaded distal end of the actuator to rotate within a threaded hole of the base portion.