CA2179262A1

CA2179262A1 - Tissue cutting die

Info

Publication number: CA2179262A1
Application number: CA002179262A
Authority: CA
Inventors: Steven Karl Lemp; Philip John Hudak; Charles S. Love
Original assignee: Individual
Current assignee: Autogenics Inc
Priority date: 1993-12-17
Filing date: 1994-12-16
Publication date: 1995-06-22
Also published as: US5609600A; ATE182771T1; US5588967A; WO1995016409A1; JPH09507771A; DE69419938D1; EP0732901A1; EP0732901B1; DE69419938T2; US5425741A

Abstract

The present invention provides a novel tissue cutting device for autologous tissue heart valves which accurately cuts the tissue to a predetermined configuration in a minimal amount of time. The disposable tissue cutting die of the present invention is comprised of a cover, a base member, a continuous blade enclosing a desired spatial configuration and an actuator for forcing said tissue against the entire perimeter of the blade.

Description

WO 95/lC409 2 ~ 7 9 2 6 2 PCr~US94/14699 TISSUE CUTTING DIE
Field of the Invention This invention relates to cutting devices and is particularly directed to tissue cutting dies used to precisely and accurately cut various tissues to a particular predetermined configuration, particularly in the fashioning of an autologous tissue heart valve.
Backqround of the Invention Heart valves are typically replaced due to birth deects, stenosis (narrowing) of the valve (in which case the heart must exert a great deal of force to pump the blood through the valve) or insufficiency or incompetence of the valve, whereby the heart is unable to prevent backf low of the blood . The diseased or damaged heart valve is removed rom the patient and replaced with some type of artificial or prosthetic valve.
The three main types of prosthetic heart valves are mF.rh::n;r~l, biological and homograft. A detailed description and background of these three types of prosthetic heart valves may be found in U.S. Patent 5,163,955, assigned to Autogenics, assignee of the present application and incorporated herein by reference. These valves, however, have proven to be costly and present an increased risk to the patient with respect to durability and acceptability.
Most recently, ~ loro~~q tissue valves, i.e. valves constructed with the patient' 8 own tissue, have been investigated. However, since this type of valve utilizes the patient~s own tissue, the valve must usually be assembled during the same surgical, procedure in which the patient ' 8 diseased or damaged valve is removed. Therefore, valve assembly must be completed in a rapid and efficient manner to avoid urther risk to the patient.
- To construct an autologous heart valve, one typically fits or mounts the patient's tissue onto a stent or some other type of valve frame. This can be accomplished by several methods. In one conventional method, the individual valve lea1ets are cut rom a rouqhly sized piece of tissue and ~ndividually sewn or attached onto the rame. In another Wo 95/16409 2 1 79~ 6 ~ PCT/US94114699 ~
_ z _ method, a single piece of roughly sized tis6ue is attached to the valve frame and the excess tissue is trimmed away. soth of these metho.ds, however, have proven to be time-con3uming and unreliable .
The above referenced ' g55 patent ,1; ~1 n3~ a novel and substantially improved cutting die for ~uickly and precisely cutting autologous tissue into the desired configuration.
This die, however, does not provide the major 1 ~v~ ts and advantages which have been incorporated into the cutting die of the present invention. These advantages will become apparent from the r\et~ Description of the Invention, considered together with the drawings and claims.
Summarv of the Invention The present invention provides a new tissue cutting device for autologous tissue heart valves which is a rnn~ ation of the die disclosed in the ' 955 patent.
The pref erred embodiment of the tissue cutting die of the present invention comprises a cover, a base member, a slide or actuator, and wing nuts.
The cover is comprised of a top member which is generally rectangular i~ shape. Pour separate blades ~it within and slightly extend above the top surf ace of the top member . The blades are arranged in the top member 80 that they form a precise outline of the desired cut piece of tissue. In addition, the ends o~ two o~ the blades abut against the r~-~; n; ng two blades, 80 that there are no gaps between the blades. This advantageously ensures that the entire piece o~
tissue is cut in one step, including the four corners where the blades meet. Thus, no ar~ t jnn~ manual cutting steps are required to separate the two pieces of tissue.
The base member, similar to the cover, is comprised of a base piece which i8 generally rectangular in shape, with a tunnel running down its center length. Another component o~
the tissue cutting die is the slide or actuator. At the first end of the slide there is a raised portion or "bump~. The second end of the slide is flat and, therefore, does not have a bump. The height of the bump is slightly greater than the ~ Wo95/16409 21 79262 PCr/US94/14699 height of the tunnel in the base member The tissue cutting die of the present invention is used in the following manner. Pirst, a roughly sized piece o~
tissue is laid flat across the top surface of the base member Next, the top surface of the cover is positioned onto the top surface of the base member and the tissue. The cover and the base member are aligned and secured together, thereby slightly '^~l~lirl~ the blades into the piece of tissue The actual cutting of the tissue occurs as the slide is pulled through the tunnel of the base member. The second end of the slide not having the bump is pushed through one end of the tunnel until the second end of the slide emerges out the other end of the tunnel. Next, the user of the tissue cutting die pulls the second end of the slide until the first end of the slide is pulled along the entire length of the tunnel and emerges from the other end of the tunnel. During this procedure, the bump, located on the first end of the slide, pushes against the thin, flexible sheet. This, in turn, causes the tissue to be pushed against the blades of the cover. Thus, a uniform and consistent cutting force, independent of the force applied by the operator, is applied to the tissue so that the tissue is completely and automatically cut along the perimeter of the desired conf iguration of cut tissue .
After the tissue is cut, the cover is removed from the base member Flnally, the resultant, pre-configured cut piece of tissue is mounted onto the heart valve stent.
Brief De~cri~tion of the Drawinqs FIGURE 1 is an exploded perspective view of the tissue 3 0 cutting die of the present invention FIGIJRE 2 is an exploded perspective view of the cover of the tissue cutting die of FIGURE 1 ~IGURE 3 is a front view of an alternate embodiment of the cover of the tissue cutting die with a one piece blade FIGI~RE 4 is an exploded perspective view of the base member of the tissue cutting die of ~IGURE 1 FIGURE 5 i8 a top view of the slide of the tissue cutting 21 7~6~
.
: ~ ~ 4 die of FIGURE 1.
FIGURE 6 i8 a side view of the partially assembled tissue cutting die of PIGURE: 1, with one wing nut screwed onto a threaded screw.
Detailed Descri~tion of the Invention FIGURE 1 illustrates an exploded view of the disposable tissue cutting die 10 of ~he present invention for precisely and accurately cutting tissue to a predetermined configuration for use in a medical prosthetic device such as an autologous heart Yalve. As discussed in detail below, the tissue to be precisely cut is placed onto the base member 14 and contacts the cutting blade 24 supported by the cover 12 when the tissue is locked between the cover 12 and the base member 14. The slide 16 i8 then translated through a tunnel 50 of the base member 14 to force the tissue between ridge 56 of slide 16 and the cutting blade 24 SO a3 to precisely cut the tissue to conform to the space defined by the cutting blade 24.
Ref erring to FIGURE 2, the cover 12 includes top member 20, insert 22, cutting blade 24 and four pairs of ferrules 26.
In the preferred embodiment, the top member 20 is made of a translucent polycarbonate material, preferably of b;nm~
grade. This top member 20 is generally rectangular in shape and has four through holes 28 located at the four corners of the top member 20. The holes are used to align and attach the cover 12 to the base member 14.
A channel 30 run9 the length of top member 20 and projects into the channel 30 to form an island 32 ila the middle of the top member 20. The outer periphery this island 32 is an outline of the desired cut tissue piece.
The preferred Amhn~limc.n~ of the heart valve disclosed and claimed in the ' 955 patent provides an inner gtent having tissue alignment members. Accordingly, the preferred embodiment of this invention includes four pairs of ferrules 26 F-mh~ r1 within the polycarbonate material of the island 32, the location of these ferrules 26 corresponding to tL~e location of the tissue alignment members of the heart valve inner stent . Ferrules 26 typically extend approximately o . a89 A~.~,EN5E0 SltEEt - : ; : . . .

' 792~2: : -mm (35 mils) above the top surface of the island 32. In addition, the diameter of the ferrules 26 corresponds to the diameter of the tissue alignment members.
Cover 12 further includes an insert 22, made of semi-translucent polycarbonate material, constructed 80 as to fit within the channel 30 and completely surround the island 32 of the top member 20. The gap between the edges of the island 32 and the insert 22 is large enough so as to accommodate and retain the cutting blade 24. In one embodiment, the insert 22 i3 precisely configured 50 that a gap of 0.0508 mm ~0.002 inch) or les5 exists between the edges of the insert 22 and the top member 20. In addition, the insert 22 has four through holes 34 located at the corrl~cr~n~;n~ locations of the f our corners of the island 3 2 .
- Cutting blade 24 is fixedly retained within the narrow gap between the island 32 and the insert 22. Cutting blade 24 is advantageously formed from four discrete blades 24a, 24b, 24c, 24d. These blades are advantageously formed from thin case hardened corrosion resistant steel having sufficient ~ ;h;l;ty to conform to the shape of the gap located hetween the island 32 and the insert 22. The blade thickness should, however, be s--f~ n~ to prevent deflection of the blade and, consequently, an inadequately cut piece of tissue. In the preferred '~o~ , the blades 24a-24d were made from a strip of 0.1524 mm (0.006 inch) thick 5~;nl~qc steel, supplied by American Safety Razor of West Virginia, having a razor-sharpened edge. That razor-sharpened edge extends 0.889 mm (35 mils) above the top surfaces of the island 32 and the insert 22.
A significant feature of the invention is that the ~our corners of the space defined by the island 32 and the cutout portion of insert 22 are relieved by ~our through holes 34 in the insert 22. As shown in FIGUR~ 1, the end of the blade 24a extends into a through hole 34 with the adjoining blade 24d abutted up against. Without this relief of this cutout portion, the precise juncture o~ the two blades 24a, 2~d would involve such tight tolerances that manufacturing l?ractices A~.',E!`~L,'-~ S~,EET

. .
typically dictate a slight gap between the blades. Die3 construCted with ga~s between adjoining blades leave a small segment of uncut tissue at the corners of the opening, requiring a manual cut af ter opening of the die to separate the two pieces of tissue. In contrast, the present invention merely involves making each blade 24a-24d slightly longer than the actual perimeter of the i81and 32, with the excess blade 24a extending into one of the holes 34.
In an alternate embodiment of the present invention, a flexible, one piece blade 25 is used to precisely cut the piece of tissue. As shown in FIGUR13 3, the four through holes 34 in the insert 22 provide an additional advantage in that they allow the cover 12 to e.~ cnmmn~te a flexible one piece blade 25. Thus, the relief provided by the radius of the through holes 34 allows a single continuous blade 25 to bend around each of the four corners of the island 32. Without the relief provided by these through holes 34, the otherwise close tolerances at the corners of the island 32 would make it difficult to ~ te a one piece blade 25. Thus, with the relief, a one piece blade 25 would have to be precisely bent to the angle formed at each of the four corners of the island 32 and still fit within the narrow gap between the island 32 and the insert 22. Therefore, the through holes 34 provide substantial additional space to allow the one piece blade 25 to bend around each of the four corners of the island 32 FIGURE 4 shows an exploded perspective view of the base member 14 of the tissue cutting die lO of the present invention, in~ ;n~ a base piece 36, a thin flexible sheet 38, four threaded screws 40 and four washers 42. The base piece 36 of the base member 14 is advantageously made of ~ a translucent polycarbonate material, preferably biomedical grade. The base piece 36 is generally rectangular in shape and has four threaded through holes 44 located at the four corners of the base piece 36.
A channel 46 is provided along the center length of the base piece 3 6 of the base member 14 . The width of the channel 46 in the base piece 36 of the base member 14 accommodate the A~ r ~3 5.~1E~T
, . , : ., .. , -, . - -~ - 2 i 79262 .

width of the island 32 and, therefore, i8 slightly wider than the width of the island 32.
The thin f lexible sheet 3 8 of the base member 14 provides the cutting pad of the tissue cutting die 10. This thin flexible sheet 38 is generally 0.8128 mm (0.032 inch) thick or less. TEFIION is the preferred material for sheet 38 due to its smooth surface r~r~tPristiC which pro~ides the correct amount of adhesion for the tissue. The thin flexible sheet 38 is generally rectangular in shape and is similar in size (i.e.
length and width) to the top member 20 of=the cover 12 and the base piece 36 of the base member 14. ~ocated at the four corners of the thin flexible sheet 38 are four through holes 48. The location of the through holes 48 in the thin flexible sheet 38 corresponds to the location of the through ho~es 44 in the base piece 36 of the base member 14.
Four threaded screws 4 0, as shown in FIGURE 4, are used to attach the thin flexible sheet 38 to the surface of the base piece 3 6 of the base member 14 . Each screw 4 0 enters through the bottom surf ace of the base piece 3 6 of the base member 14 and extends through the top surface of the thi~
flexible sheet 38. Due to the channel 46 provided along the center length of the base piece 3 6 of the base member 14, the thin flexible sheet 38 creates a tunnel 50 in the base member 14, as shown in FIG~RE 1 A washer 42 is positioned onto each of the screws 40 and rests on the surface of the thin flexible sheet 38. The th; ~-knPq~l of the washers 42 is determined by the height by which the blades 24a-24d extend above the surfaces oi~ the island 32 and the in~ert 22. Thus, by way of specific example, if the blades 24a-24d extend 0 . 889 mm (35 mils) above the surfaces of the i~land 32 and the insert 22, then the washers 42 must be at least 0.889 mm (35 mils) in thickness.
This is to ensure that the blades 24a-24d are not damaged by the thin flexible sheet 38 during shipment of the assembled tissue cutting die 10. In addition, the washer~ enable the~
blades 24a-24d to securely hold the piece of tissue between the cover 12 and the base member 14, without actually cutting ', ' ~ ': - . ' , , : - - - - . , :

2i79262 the tissue. In thi8 specific example, the maximum thickness of the washers 42 is calculated by adding the blade height (35 mils) and half of the nominal average tissue thickness (15-20 mils) .
FIG~RE 5 shows one ~mho~ of the slide 16 of the tissue cutting die 10 of the present invention. The slide 16 is longer in length but slightly narrower in width than the channel 46 in the ba8e piece 36 of the base member 14. The slide 16 is advantageously made of thermoplastic a~d is similar in thirkn~R~ to that of the thin flexible sheet 38.
A "bump" 56 or raised portion is located on the top 8urface of the slide 16 near the end 52. The height of the bump 56 is equal to or slightly greater than the height of the tunnel 50 in the base member 14. The opposite end 54 o the slide 16 is generally flat. In the embodiment shown, slightly raised ~arrow" symbols 57 are located on the top surface of the slide 16 near its end 54. The middle or cut-out portion 58 of the slide 16 is cut out, in the ~ shown, 80 that the user' s finger can be inserted within the cutout portion proximate to arrows 5 7 to obtain a firmer grasp of the slide 16, and thereby facilitate ~he pulling of the slide 16. The use of the slide 16 will be described in detail below.
FIGU~B 6 illustrates a side view of the partially assembled tissue cutting die 10 of the present invention, with one o~ the four wing nuts 18 screwed onto one of the threaded screws 40. The wing nuts 18 are advantageously made of thermoplastic material and have a preformed in~ ni~l thread.
The wing nuts 18 are primarily used as a clamping means and, therefore, are of adequate size to allow one to easily and smoothly secure the wing nuts 18 onto=the screws 40.
The tissue cutting die 10 of the present invention is used in the :Eollowing manner. First, a roughly sized piece oE
tissue is laid i~lat across the top sur~ace of the thin ~lexible sheet 38 o~ the base member 14. Due to the slipperiness of the patient' s tissue and the a~hesion characteristics of a material such as TEFLON (TM), the tissue can be easily smoothed to lie flat~across the thin flexible A~.~,-tN~D SHEET
.

.
~ . 21 79~2 .
... ., 9 sheet 3 8 . Next, the cover 12 i3 assembled onto the base member 14 so that the blades 24a-24d can contact the thin flexible sheet 38. This i5 accomplished by aligning the holes 28 located in the four corners of the cover 12 with the threaded ends o~ the screws 40 protruding out the top surface of the ba6e member 14. In addition, the cover 12 and tissue are aligned so that the blades 24a-24d will cut the desired portion of the tissue.
Once the cover 12 is ~CR~rnhl~l onto the base member 14, the tissue is clamped between the two assemblies 12, 14 with the wing nuts 18. During this step, the blades 24a-24d may become slightly embedded into the tissue. However, due to the strength or toughness of the tissue, the blades 24a-24d normally do not completely penetrate the tissue.
The actual cutting of the tissue is accomplished by pulling the slide 16 through the entire length of the tunnel 50 of the base member 14. The second end 54 of the slide is pushed through one end of the tunnel 50 until it emerges out the opposite end of the tunnel 50. Due to the symmetry o~ the cover 12 and base member 14, the slide ~6 may be pulled through either e~d of the tunnel 50, in the direction indicated by the "arrow" symbols 57 located on the second end 54 of the slide 16. The user of the tissue cutting die 10 pulls the second end 54 of the slide 16 until the first end 52 of the slide 16 is pulled along the entire length o~ the tunnel 50 and emerges out the other end of the tunnel 5D.
During this procedure, the bump 56, located on the firs~ end 52 of the slide 16, pushes against the bottom surface of the thin flexible sheet 38. This, in turn, forces the tissue to be pu~3hed against the blades 24a-24d and the ferrules 26 of the cover 12.
The bump 56 located on the first end 52 of the slide 16 produces a ~wave" in the tissue and the thin flexible sheet 38. This ~wave~ allows one to sequentially oush portions of the tissue into the blades 24a-24d, thereby enabling the blades 24a-24d to work in shear. Due to the angle between the 5~D SHEET
:.. - ,- . . . .

~ 1 o four blades 24a-24d and the bump 56, all the blades 24a-24d are able to cut the tissue in shear.
~fter the tissue is cut, the wing nuts 18 are unscrewed from the threaded screws 40 so that the cover 12 may be carefully removed from the base member 14. The resultant, pre-configured cut piece of tissue is removed from the base member 14 and mounted onto the valve stent. The remaining excess tissue may be discarded.
Obviously, numerous variations and modif ications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the f orms of the present invention described above and shown in the figures of the At't_ , -nying drawings are illustrative only and are not intended to limit the scope of the present i~vention .

3 ', - , .... : - -, .. . . . . -. . : . - . - . . - ~

Claims

What is claimed is:

1. An apparatus for quickly and precisely cutting a piece of autologous, homologous, or heterologous tissue to a desired spatial configuration, said apparatus applying a consistent cutting force substantially independent of the force applied by the operator so that the tissue is substantially completely and automatically cut along the perimeter of said desired spatial configuration, said apparatus comprising:
a cover (12) having a top member (20) with a center length and a channel (30) having a raised island portion (32) disposed along said center length, said cover (12) further including an insert (22) having a cutout conforming to said island (32) and one or more blades (24) disposed between said insert (22) and said island (32);
a base member (14) adapted to receive said cover (12), said base member (14) having a base piece (36) with a center length and a channel (46) disposed along said center length, said base piece further comprising a flexible sheet (38) secured to said base piece (36) over said channel (46) to form a tunnel (50) therebetween;
an actuator member (16) slidably mounted in said tunnel (50), said actuator member (16) having a raised portion (56) in contact with said flexible sheet (38), said raised portion (56) being adapted to force said flexible sheet (38) against said blades (24) as said actuator member (16) is translated through said tunnel (50) so that the tissue retained between said blades (24) and said flexible sheet (38) is automatically cut when said actuator member (16) is translated through said tunnel (50); and a plurality of attachments provided to secure said cover and said base member together.

2. The apparatus of Claim 1, wherein said island portion (32) has a shape corresponding to the spatial configuration into which the tissue will be cut.

3. The apparatus of Claims 1 or 2, wherein said island portion (32) includes a plurality of raised ferrules (26) positioned to cut holes into the tissue at predetermined locations.

4. The apparatus of any of Claims 1-3, wherein a narrow gap exists between said insert (22) and said raised island portion (32) when said insert (22) is inserted into said top member (20), and said blades (24) are positioned within said gap and extend above a plane of said top member (20) and said island (32).

5. The apparatus of any of Claims 1-4 wherein said insert of said cover further comprises:
a plurality of holes (34) formed at the corners of said cutout for receiving said island (32), said blades (24) extending into said holes (34) to allow the outline of said tissue to be continuous when said tissue is cut.

6. The apparatus of any of Claims 1-5 wherein said top member (20) is made of a translucent polycarbonate material.

7. The apparatus of Claims 1-6 wherein said insert (22) is made of a semi-translucent polycarbonate material.

8. The apparatus of any of Claims 1-7 wherein said island (32) and said top member (20) of said cover (12) form a gap of 0.0508 mm (0.002 inch) or less.

9. The apparatus of any of Claims 1-8 wherein said blades (24) are made of a high quality corrosion resistent material, such as stainless steel, with a razor sharpened edge.

10. The apparatus of any of Claims 1-9 wherein said blades (24) are 0.1524 mm (0.006 inch) thick.

11. The apparatus of any of Claims 1-10 wherein said blades (24) extend 0.889 mm (35 mils) above the top surfaces of said island and said insert.

12. The apparatus of any of Claims 1-11 wherein said ferrules (26) extend 0.889 mm (35 mils) above the top surface of said island.

13. The apparatus of any of Claims 1-12 wherein said base piece (36) of said base member (14) is made of a translucent polycarbonate material.

14. The apparatus of any of Claims 1-13 wherein said flexible sheet (38) is made of TEFLONTM.

15. The apparatus of any of Claims 1-14 wherein said actuator member (16) is made of a thermoplastic material.

16. A method for precisely, repeatably cutting a piece of tissue into a predetermined shape comprising the steps of:
providing a roughly sized piece of tissue;
providing a tissue cutting die having a cover (12) having raised blades (24) for cutting said piece of tissue and a base member (14) having a flexible sheet (38) with top and bottom surfaces, said flexible sheet (38) forming a tunnel (50) in said base member (14);
laying said roughly sized piece of tissue flat across said top surface of said flexible sheet (38);
assembling said cover (12) and base member (14) of said tissue cutting die together and securing said cover (12) and base member (14) to each other;
providing a slide (16) having a first end portion (52) including a raised portion (56) and a flat second end portion (54);
inserting said second end portion (54) of said slide (16) into said tunnel (50) formed by said flexible sheet (38);
pulling said second end portion (54) of said slide (16) through said tunnel (50), allowing said raised portion (56) of said slide (16) to push against said bottom surface of the flexible sheet (38), causing said tissue to be pushed against the blades (24) of said cover (12); and disassembling said cover (12) and base member (14) and removing said tissue therefrom.

17. The method of Claim 16 wherein said blades (24) cut said tissue by shearing.

18. The method of Claim 17 wherein said shearing is caused by said raised portion of said slide (16) producing a wave which sequentially pushes portions of said tissue into said blades (24).