AU617009B2

AU617009B2 - Apparatus and procedure for verifying prosthetic implant seating

Info

Publication number: AU617009B2
Application number: AU42759/89A
Authority: AU
Inventors: Harold K. Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-10-10
Filing date: 1989-10-10
Publication date: 1991-11-14
Anticipated expiration: 2009-10-10
Also published as: AU4275989A

Description

7 S F Ref: 109641 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION 617009

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Published: Priority: Related Art: Q00 0 0 *0 00 0 004 $4 .4 C 4 0i 4r 40 $4,,r Name and Address of Applicant: Harold K. Dunn 1231 Chandler Circle Salt Lake City Utah 84103 UNITED STATES OF AMERICA Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: Apparatus and Seating Procedure for Verifying Prosthetic Implant The following statement is a full description of this invention, including the best method"'f performing it known to me/us rit 5845/4

I~

IA BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention relates generally to surgical procedures and more particularly to apparatus and proper femoral intramedullary channel preparation prosthetic femoral hip implant.

instruments and a procedure for verifying and seating therein of a PRIOR ART In a hip replacement surgical procedure where the head and neck of the posterior femur are removed and replaced with a prosthetic implant it is required that, once installed, this prosthetic device remain stationary for proper healing and prosthesis functioning. In practice, if a prosthetic implant is loose such that rotational micromovement of the implant within the bone will occur, particularly for a prosthesis that is secured by means of friction or porous ingrowth coatings, that rotational movement will loosen the fit, shearing away the ingrowth, and prohibiting healing.

A patent to Boland, U.S. Patent No. 4,576,158, shows a torsional o testing device for testing bone stability; with a patent to Cordey, U.S. Patent No. 4,359,906, showing a device for tightening a screw into a :o 20 bone material to a pre-set force; and a patent to Daniel, et al., 0 U.S. Patent No. 4,712,542, that shows a device nd procedure for verifying ligament isometric positioning and tensioning. Where tooling for placing and positioning of certain hip prosthesis are shown in patents to McKee, U.S. Patent No. 3,801,989; Amstutz, U.S. Patent No. 3,857,389; and Kaufer, et al., U.S. Patent No. 3,868,730; these patents do not consider torsional testing of a seated hip femoral prosthesis.

0 0000 0 0 00 4 40 o 40 4 4 TMS/27521 0$FFK.

2 SUMMARY OF THE INVENTION It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

There is disclosed herein a process for verifying proper friction coupling of a prosthetic hip implant in a prepared femoral intramedullary channel comprising the steps of, to a proximal femur that has had the head and neck thereof removed along a diagonal above the greater and lesser trochanter, preparing the intramedullary channel to receive a prosthetic hip implant; seating a rasp tool means in the prepared intramedullary channel; applying a torsional force to said rasp tool means for a period of seconds where, if said rasp tool means does not experience rotational micromovement, the intramedullary channel preparation is deemed to be correct; installing a prosthetic hip implant in friction fitting engagement in said prepared intramedullary channel; testing the friction fit of said prosthetic hip implant by applying a torsional force for a period of seconds on said prosthetic hip implant, with the fit determined to be correct if said prosthetic hip implant does not experience rotational micromovement.

There is further disclosed herein apparatus when used to carry out the above process comprising, a torque wrench means for operation by a surgeon to generate a certain torsional force through a drive; a U-shaped adapter that includes means for releasably coupling to said torque wrench drive at a web and parallel legs that are appropriately open therebetween to span and fit closely along opposite faces of a prosthetic hip implant.

Ti TMS/27521 mri i :rnin -n m<MI* I- W ~w -3- BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 shows a profile perspective view of the proximal femur wherefrom the head and neck areas, above the lesser trochanter, have been removed and the intramedullary channel A I 4b 'IS/27521 4 prepared to receive a prosthetic implant, which preparation is shown being tested by application of a torsional force through an adapter to a rasp that is shown inserted in that prepared intramedullary channel.

Fig. 2 is an enlarged profile perspective view of the rasp of Fig. 1, removed from the intramedullary channel; Fig. 3 is an enlarged profile perspective view of the adapter of Fig. 1 rotated to the vertical; Fig. 4 is a profile perspective view showing the proximal femur of Fig. 1 with a prosthetic hip femoral implant aligned for installation in the prepared intramedullary channel, the adapter of Fig. 3 shown straddling the prosthesis neck with a torque wrench aligned for attachment to that adapter; and Fig. 5 is the assembled view of the components of Fig. 4.

DETAILED DESCRIPTION In hip replacement surgery the proximal femur 10, as shown in Fig. 1, is prepared to receive a prosthetic femoral hip implant by cutting the bone along a diagonal across the femur neck, above the lesser and greater trochanter, as shown j at 11. The proximal end of the femur intramedullary channel is thereby exposed for enlargement to receive a prosthetic hip femoral implant utilizing a rasp 12. Rasp 12 is shown in Fig.

2 as including, below a flat head end 14 and narrow rectangular portion a body 13, a round cross-section that is tapered inwardly to a blunt lower end. Below the head end 14, iu

F'

in the rectangular portion, the rasp body is holed laterally at 15 to receive a rod or like tool, not shown, that is f itted therethrough for applying a torsional force to the rasp.

Fig. 1 shows the rasp 12 seated in the prepared intramedullary channel end. In that intramedullary channel preparation the rasp is moved up, down and turned therein such that cutting ridges 16, as shown in Fig. 2, will file away the channel wall, appropriately enlarging it to a suitable diameter and depth to accommodate a prosthetic implant like the prosthetic hip implant 33, that is shown in Figs. 4 and In this filing process, as shown in Figs. 1 and 2, a force may be applied to the rasp as by tapping it with a hammer, on the Srasp head end 14. Which rasp 12, as set out above, can be turned by fitting a rod, not shown, through rasp hole 15, and manually turning it. For preparing the intramedullary channel, the rasp 12 provides, as an arrangement for sizing the channel to a certain opening that will fit a particular size of prosthetic hip implant as determined by the surgeon, lines, shown as A, B and C that are scribed around the rasp mid-portion, as shown in Figs. 1 and 2. The lines A, B and C represent different sizes~ of prosthetic hip femoral implants.

In practice, the rasp 12 is urged into the intramedullary4 channel until a select line A, B or C is aligned with the lowest edge of the in'tramedullary channel, which positioning indicates that the intramedullary channel is appropriately prepared for the particular size of prosthesis.

With the rasp 12 fitted in the intramedullary channel, as set out above, the seating thereof is then torsionally tested. This testing is preferably accomplished utilizing a 6 torque wrench 18 that, as shown in Figs. 1, 4 and 5, includes a dial 21 for indicating force in points that is applied through a square drive 19. The square drive 19 is operated through an arm, not shown, that is connected to turn a pointer that is pivoted over scale graduations formed around the face of dial 21. The square drive 19, that is journaled in an under surface of housing 22, is arranged to transmit a torque therethrough as applied at a handle end 23 of the torque wrench, which force is displayed as pointer 20 travel over the dial 21 scale graduations. So arranged, the pointer positioning over a scale graduation is indicative of a torquing force being applied through square drive 19. In practice, a dial indicating torque wrench, model "DA", manufactured by Utica Toll Company, Inc., has been used successfully as the torque wrench i8.

Shown in Fig. 1, the torque wrench square drive 19 is aligned to fit into a square opening 28 that is formed in a necJk end 26 of an adapter 25. Shown best in Fig. 3, the adapter 25 is preferably formed to have a U-shape with coplanar parallel legs 29 that extend from the ends of a web portion 28. The parallel legs 29 are shown stepped apart from a first narrow opening 30 adjacent to the web portion 28, to second opening 31.

Fig. 1 shows the square drive 19 aligned to enter the adapter square opening 27, which adapter 25 straddles the rectangular cross-section end of the rasp 12. The rasp end is shown seated between the parallel legs 29, and have traveled therein to the first opening 30. So arrangetd, after the rasp i 12 has been used to prepare the bone intramedullary channel for seating a prosthetic implant, a torsional force is applied thereto to verify proper intramedullary channel preparation.

In practice, when the rasp 12 does not experience rotational micromovement at an applied torque of approximately sixty inch pounds applied for approximately fifteen (15) seconds it can be assumed that the intramedullary channel is properly prepared to receive the prosthetic hip femoral implant 33 seated therein.

Shown in Fig. 4, the prosthetic hip femoral implant 33, hereinafter referred to as implant, is aligned for installation in the prepared intramedullary channel and has the adapter 25 fitted over a neck 34 thereof. The preferred implant neck 34 is of a thickness to just fit between the parallel legs 29 at the second opening, the area between the second and first openings to butt against a top surface of that neck. As shown in Fig. i, the adapter parallel legs 29 has sloped ends 32 that butt against an upper edge of a compressed metal shavings matt 37 that is arranged as a midsection of the implant, below a dogleg bend, hereinafter referred to as matt 37. Matt 37 is to provide an area of multiple ridges and depressions for encouraging bone growth into the matt as will occur in the natural healing process.

Shown best in Fig. 4, the prosthetic implant edges, below matt 37 are curved to essentially a round cross-section, of a bottom portion 36. The implant bottom portion includes elongate depressions 36a that are formed in opposite surfaces thereof that are for receiving bone growth therein to further lock the implant in place.

,t

B

rl o I 9 r r r r I o i lot sca;e ;Iir i rio i

I

Fig. 4 shows the wrench square drive 19 aligned for fitting in a second square opening 35 of the adapter 25, which square opening 35 is longitudinally formed into the adapter neck 26, at a right angle to the square opening 27. In Fig. the torque wrench 18 is shown connected through adapter 25 to apply a torsional force to the implant 33, after which implant has been seated in the prepared intramedullary channel.

Whereafter a ball, not shown, of a ball and socket hip joint prosthesis can be secured to the implant head end shaft 38.

Fig. 5 shows the torque wrench 18 with its square drive 19 connected to the adapter 25 at the second square opening So arranged, the adapter parallel legs 29 straddle the oo implant 33 to impart a torsional force thereto as reflected by the positioning of pointer 20 over one of the scale graduations of dial 21. In practice, the implant 33 is o secured by its friction engagement in the prepared intramedullary channel. With bone growth to the implant as occurs in the healing process to further secure the implant in place. Should, however, that implant, after seating, b subject to rotational movement, that movement will tend to shear away the porous bone ingrowth, tending to loosen the friction fit, destabilizing the appliance. Accordingly, it is highly desirable to test implant seating prior to closure.

The present invention provides for such testing by the application of a torsional force of approximately sixty inch pounds for approximately fifteen (15) seconds thereto.

At such force application, if the appliance does not experience rotational micromovement, the implant friction fit can be judged to be secure. Providing, of course, the implant i ^i 9 i i 33 is otherwise stable. The applied force can vary for different sizes of implants and accordingly, for a full 'i range of sizes of a preferred prosthetic implant identified i; as an "Anatomic Hip", manufactured by Zimmer, Inc., the torsional force to be applied to confirm an acceptable friction fit is approximately sixty (60) inch pounds of torque, plus or minus ten (10) pounds for fifteen Sseconds, plus or minus five seconds. Of course, a greater Sp force application for a longer period of time can obviously be used within the scope of this disclosure.

Hereinabove has been set out a preferred system and NI apparatus of the present invention for practicing a torsional i a, testing process to verify a proper friction mounting of a hip Sprosthetic implant. It should, however, be understood that the present disclosure is made by way of example only and that the apparatus and process set out herein may be varied without i departing from the subject matter coming within the scope of the following claims, and any reasonable equivalency thereof, which claims I regard as my invention.

i i J

Claims

1. A process for verifying proper friction coupling of a prosthetic hip implant in a prepared femoral intramedullary channel comprising the steps of, to a proximal femur that has the head and neck thereof removed along a diagonal above the greater and lesser trochanter, preparing the intramedullary channel to receive a prosthetic hip implant; seating a rasp tool means in the prepared intramedullary channel; applying a torsional force to said rasp tool means for a period of seconds where, if said rasp tool means does not experience rotational micromovement, the intramedullary channel preparation is deemed to be correct; installing a prosthetic hip implant in friction fitting engagement in said prepared intramedullary channel; testing the friction fit of said prosthetic hip implant by applying a torsional force for a period of seconds on said prosthetic hip implant, with the fit determined 15 to be correct if said prosthetic hip implant does not experience rotational micromovement.

2. A process as recited in claim 1, wherein the torsional force applied to both the rasp tool means and prosthetic hip implant is approximately sixty (60) inch pounds, plus or minus ten (10) inch pounds.

3. A process as recited in claim 1, wherein the torsional force applied to both the rasp tool means and prosthetic hip implant is applied for approximately fifteen (15) seconds, plus or minus five seconds.

4. A process as recited in clalm 1, wherein the torsional force is applied through an adaptor by a torque wrench having a capability to visually display the force being applied therethrough.

A process for verifying adequate bone removal from a femur intramedullary channel in preparation for implantation of a femoral component of a hip prosthesis comprising the steps of, resecting a natural femoral head from a femur so as to expose the Intramedullary channel; fitting a selected rasp tool means into said intramedullary channel; attaching a means for applying a torque to said rasp tool means; and applying a torsional force to said rasp tool means through said attaching means of a magnitude to where an absence of rotational micromovement of said rasp tool means within said Intramedullary channel verifies adequate bone removal. 1 /TMS,27521 0~ 0i F1 11

6. A process as recited in claim 5, wherein the torsional force applied to said rasp tool means is sixty (60) inch pounds, plus or minus ten (10) inch pounds.

7. A process as recited in claim 5, wherein the torsional force is applied to said rasp tool means for fifteen (15) econds, plus or minus five seconds.

8. A process as recited in claim 5, wherein the torsional force is applied through an adaptor by a torque wrench that includes a visual display showing a force being applied therethrough.

9. A process as recited in claim 1, wherein the torsional force Is applied through an adapter by a torque wrench having a capability to visually display the force being applied therethrough.

Apparatus when used to carry out the process of any one of the preceding claims comprising, a torque wrench means for operation by a surgeon to generate a certain torsional force through a drive; a U-shaped adapter that includes means for releasably coupling to said torque wrench drive at a web and parallel legs that are appropriately open therebetween a to span and fit closely along opposite faces of a prosthetic hip implant.

11. Apparatus as recited in claim 10, wherein the torque wrench means Includes a body having hand engaging end that Is spaced apart from the drive that extends from the opposite body end; and an indicator means arranged in said body that includes a dial whereon are scribed scale 4graduations indicative of Inch pounds of force, which indicator means includes a pointer means that is connected to said drive such that a 25 torsional force applied therethrough moves the pointer means over said graduations responsive to a force applied at said drive.

12. Apparatus as recited in claim 10, wherein the drive is a square drive Lnd the means for coupling said square drive to the adapter is a square opening that is formed in the web of said adapter between the parallel legs, said square opening aligned with the opening between the parallel legs.

13. Apparatus as recited in claim 12, wherein the adapter parallel legs are equidistantly spaced with a first open area therebetween that is proximate to the web, which parallel legs are stepped outwardly to a second open area, which second open area is to closely accommodate the prosthetic hip implant fitted therebetween. TMS/275 c' -F ^7 b 12

14. Apparatus as recited in claim 13, further Including a second square opening formed in the web of the adapter at a right angle to the first square opening and to the opening between the parallel legs, said second square opening to accommodate the torque wrench square drive fitted therein; and the first open area between the adapter parallel legs just accommodates a neck area of a rasp means for removing bone material from a femur intramedullary channel.

Apparatus as recited in claim 14, wherein the ends of the adapter parallel legs are identically sloped on a diagonal from one face of the adapter to the other adapter face.

16. A process for verifying proper friction coupling of a prosthetic hip implant in a prepared femoral intramedullary channel, the process being substantially as hereinbefore described with reference to the accompanying drawings.

17. Apparatus when used to carry out the process of claim 16, the apparatus being substantially as hereinbefore described with reference to ;the accompanying drawings. DATED this FOURTEENTH day of AUGUST 1991 Harold K. Dunn Patent Attorneys for the Applicant S. SPRUSON FERGUSON 41 *L TMS/27521