Technical Field

This invention relates to an improved surgi- cal clip for clamping vascular tissue, for exampl e, to isolate a cerebral aneurysm.

Background __£ the invention

A cerebral aneurysm clip is a surgical instrument which clamps the base part of a cerebral aneurysm to temporarily or permanently isolate it from the cerebral artery. For this purpose, the clip must maintain the clamping pressure with high reliability

as long as desired without inj ury to the wall of the blood vessel. Possible causes of such injury are shearing of the clamping jaws resulting from improper jaw alignment, improper clamping pressure, introduction of foreign material trapped in cracks and crevices in the clip material, surface imperfections which can tear tissue and use of unsuitable material.

A number of different cerebral aneurysm clips are known in today's art. Generally, however, these clips have shortcomings which render them undesirable for the use for which they were designed.

In order to provide satisfactory and pro- longed service when properly implanted, a cerebral aneurysm clip should satisfy most, and preferably all , of the following criteria:

1. The clamping pressure of the jaws of the clip should be sufficient to isolate the aneurysm but not so high as to damage the blood vessel wall during either temporary or permanent implantation.

2. The clamping pressure of the clip should remain constant over time to prevent displacement or slipping of the clip.

3. The clip should be as small as possible for permanent implantation in the brain.

4. The material of construction of the clip should be nonmagnetic to prevent interference with magnetic resonance imaging.

5. The shape of the clip should not obstruct the surgeon's view during implantation.

6. The clip should be designed for ease of implantation with the appropriate application tool.

7. To prevent unintentional tears and pres¬ sure points, jagged edges should be absent from the surface of the clip.

8. The surface of the clip should be free from cracks and crevices which trap foreign matter and contamination and which are susceptible to propagation by stress corrosion.

9. Proper jaw alignment should be main¬ tained at all times to prevent shearing of the vascular tissue between the jaws.

Basic clips having no provision for maintaining jaw alignment, such as are described in U.S. Patent No. 3,827,438, U.S. Patent No. 4,024,868, or U.S. Patent No. 4,340,061, are not acceptable for implantation under the above-listed criteria.

A number of aneurysm clips having differently designed j aw guides to provide proper jaw alignment have been proposed and are availabl e. It is in these solutions to jaw alignment that problems with respect to the other criteria for an acceptabl e aneurysm clip arise. U.S. Patent No. 4,484,581 des¬ cribes one such clip wherein a window in one arm confines the movement of the other arm which passes through the window in an arrangement similar to an electrical clamp. The window is formed by a recess in one arm bridged by a plate-like piece which is attached to the arm with the recess.

Typically such clips are formed from wide strips of metal and such width both obstructs the surgeon's view and prevents precision clamping of the aneurysm base. When the size of such a clip is reduced to dimensions more typical of cerebral implants (1-2 mm wide, 0.5-2 cm long), it is made of stainless steel to provide adequate strength in the material forming the window frame and the thin portion of the arm passing through it. use of stainless steel can be undesirable for cerebral implantation because its magnetic properties interfere with magnetic resonance imaging diagnosis.

use of the highly desirable implant grade titanium 6-A1 4-V alloy circumvents this objection but presents an additional problem. Typically, the recess

in the "window" arm is formed by machining the width of the arm down to less than half of the full width of the arm. The "guided" arm is similarly machined to fit inside the window. This reduction in the width of the arms correspondingly weakens them and creates stress concentration sites. In addition, titanium metal and its alloys are notch sensitive and suscept¬ ible to phase separation when machined. The sharp corners of the recess and the machining process used

10 to form the guide means can result in the creation and propagation of microcracks in the metal surface, a possibility which renders this style of clip undesir¬ able for use as a cerebral implant.

1 ς

^■ -"' A wire guide means is described in U.S.

Patent No. 4,360,023. The wire restricts the movement of the arms in a manner similar to the window in the arm of the clip in U.S. Patent No. 4,484,581. The method of fixing the wire in the clip consists of

20 drilling two holes in one arm and subsequently riveting the wire ends into these holes. As with the machined regions of the previously described clip, this arrangement is susceptible to microcracks around the holes and also in the regions of riveting. The

²⁵ resultant potential for crack propagation and trapping of unwanted contaminants in the cracks render this type of clip unsuitable for safe implantation.

ϋ.S. Patent No. 4 ,192,315 discloses an aneurysm clip in which the clamping j aws of the clip are supported by arms which cross inside a ring loop. This clip suffers from a number of probl ems. First, the guide loop protrudes from the clip to create an undesirable obstruction to the surgeon's view and while the arms of the clip can be narrowed in the crossing region to permit the use of a smaller, less obstructive ring, such a solution compromises the strength of the clip and its ability to maintain a desired clamping pressure. In addition, the ring is necessarily loose to permit free movement of the arms crossing within it. The ring, therefore, can fail to precisely guide the clamping j aws to avoid shearing of tissue between them. Finally, if the clip is formed of highly desirable titanium metal or titanium alloys, welding of the ring poses probl ems of poor strength and surface irregularities.

Summary oL £h≤ Invention

A surgical clip, constructed in accordance with the present invention, is formed from a contin¬ uous, resilient member and includes two arms and a coil spring between the arms. The first arm has (i) a flex section extending along an axis extending along the length of the clip and (ii) a clamping jaw extending from the flex section at one free end of the resilient member. The second arm has (i) a flex section

disposed on the opposite side of the clip axis from the fl ex secti on of the first arm and extends al ong the clip axis, (ii) a guide loop extending from the fl ex section of the second arm and through whi ch the first arm extends, and (iii) a clamping j aw extending f rom the guide loop at a second f ree end of the resilient member. The two flex sections are resiliently deformable from their positions with respect to the clip axis. The coil spring, located between the first and second flex sections, urges the clamping jaws together.

In the preferred embodiment of the invention, the clip is formed from a material which is nonmagnetic and compatibl e with body tissue, such as titanium metal or a titanium alloy.

E JL≤f escrip ion Δ £i_£ Drawings

Figures 1 and 2 are top and bottom views of a first embodiment of a surgical clip constructed in accordance with the present invention;

Figures 3 and 4 are top and side views of a resilient member fromwhich the Figures 1 and 2 can be formed;

Figure 5 is a perspective view of a second embodiment of a surgical clip constructed in accordance with the present invention; and

Figure 6 is a top view of the surgical clip shown in Figure 5.

Detailed Description nl ϋu≥ Invention

Referring to the drawings, a surgical clip 10, constructed in accordance with the present inven¬ tion and shown in Figures 1 and 2, is formed from a continuous, resilient member 12 such as shown in Fig¬ ures 3 and 4. The clip 10 includes a first arm 14, a second arm 16 and a coil spring 18.

Arm 14 comprises a flex section 20 and a clamping jaw 22. Flex section 20 extends along an axis 24 which extends along the length of the clip 10. For the embodiment of the invention shown in Figure 1, flex section 20 extends away from axis 24 and includes a first straight length 26 which extends away from one end of coil spring 18, an inwardly bent elbow 28 and a second straight length 30 which extends across axis 24 to elbow 31 and then to clamping jaw 22 at one free end of resilient member 12.

The second arm 16 comprises a flex section 32, a guide loop 34 and a clamping jaw 36. Flex sec-

tion 32, identical to flex section 20, extends along axis 24 symmetrically with respect to flex section 20 about axis 24 and includes a first straight length 38, an inwardly bent elbow 40 and a second straight length 42 which extends toward axis 24 and terminates at an elbow 44 prior to crossing axis 24. Guide loop 34 extends from flex section 32 generally perpendicular to axis 24 across axis 24 and around arm 14. Specifically, guide loop 34 extends from elbow 44

10 across axis 24 and has a reverse bend 46 leading to another elbow 48 from which clamping jaw 36 extends. The parts of guide loop 34 preferably are shaped and dimensioned so that arm 14, extending through the guide loop, is in contact with the guide loop but can - ¹ - ⁵ slide within the guide loop. Also, reverse bend 46 is located so that jaws 22 and 36, when urged toward each other, will come into contact before arm 14 would come into contact with the inside surface of the reverse bend. For the embodiment of the- invention which is

20 illustrated, guide loop 34 is an open loop in that it does not completely encircle arm 14.

Coil spring 18, located between lengths 26 and 38 of arms 14 and 16, respectively, urges flex

25 sections 20 and 32 apart and clamping jaws 22 and 36 together with a predetermined force. For the embodi¬ ment of the invention illustrated, clamping jaws 22 and 36 are disposed on opposite sides of axis 24. Clamping jaws 22 and ^~ 36 are separated and moved away

from axis 24 by application of a force, using an appropriate tool, which draws elbows 28 and 40 toward one another against the action of spring 18. When the separated clamping jaws 22 and 36 are properly posi¬ tioned around the tissue to be clamped, the force applied to elbows 28 and 40 is released and coil spring 18 urges jaws 22 and 36 together with the tissue clamped between them.

As indicated above, misalignment of jaws 22 and 36, when cl osing the clip or with the clip in the clamped position, risks damage to the clamped tissue due to shearing by j aws 22 and 36 and incompl ete isolation of the clamped tissue due to reduced effective clamping force. Loop 34 functions to pre¬ vent misal ignment of j aws 22 and 36 by limiti ng arm 14 to two degrees of f reedom to move relative to arm 16. As l ength 30 of arm 14 extends through loop 34 , it tightly and resiliently contacts loop 34. This resilient contact is maintained as length 30 slides along the length of and through loop 34 during opening and closing of clip 10. Thus, arms 14 and 16 are permitted only two degrees of freedom to move, assuring alignment of jaws 22 and 36 during placement and implantation of clip 10.

Figures 5 and 6 are perspectiv e and top views, respecti ely, of a second embodiment of a surgical clip constructed in accordance with the

present invention. This embodiment of the invention is generally similar to the embodiment of the invention illustrated in Figures 1 through 4, except that the guide loop in the second embodiment is formed differently from the guide loop in the first embodiment.

As with the surgical clip illustrated in Figures 1 through 4, the surgical clip 60, shown in Figures 5 and 6, is formed from a continuous, resilient member, such as the one shown in Figures 3 and 4, and includes a first arm 64, a second arm 66 and a coil spring 68. Arm 64 comprises a flex section 70 and a clamping jaw 72. Flex section 70 extends along an axis 74 which extends along the length of clip 60. For the embodiment of the invention shown in Figs. 5 and 6, flex section 70 extends away from axis 74 and includes a first straight length 76 which extends away from one end of coil spring 68, an inwardly bent elbow 78 and a second straigth length 80 which extends across axis 74 to an elbow 82 and then to clamping jaw 72 at one free end of the continuous, resilient member from which the surgical clip is formed.

Arm 66 comprises a flex section 84, a guide loop 86 and a clamping jaw 88. Flex section 84 extends along axis 74 opposite flex section 70 and includes a first straight length 90 which extends away

f rom the second end of coil spring 68 , and inwardly bent elbow 92 and a second strai ght l ength 94 which extends across axis 74. Guide loop 86, which extends from flex section 84 and through which straight length 80 of flex section 70 extends, includes a reverse bend 96, a straight length 97 , a second reverse bend 98 and a second straight length 99 and terminates at an elbow 100 f rom which clamping j aw 88 extends at the second free end of the continuous, resilient member from which the surgical clip is formed.

For the embodiment of the invention il lustrated in Figures 5 and 6, guide loop 86 extends parall el to straight length 94 of flex section 84 and is in the form of a flattened oval which encircl es straight length 80 of flex section 70. The parts of guide loop 86 ar.e preferably shaped and dimensioned so that arm 64, extending through the loop, is in contact with the guide l oop but can sl ide within the guide loop. Rev erse bend 96 is located so that cl amping jaws 72 and 88 , when urged toward each other, will come into contact bef ore arm 64 contacts the inside surface of reverse bend 96.

Coil spring 68, located between lengths 76 and 90 of arms 64 and 66 , respectively, urges flex sections 70 and 84 apart and clamping j aws 72 and 88 together with a predetermined force. For the embodiment of the invention illustrated in Figures 5

and 6, clamping jaws 72 and 88 are disposed on opposite sides of axis 74. Clamping jaws 72 and 88 are separated and moved away from axis 74 by application of a force, using an appropriate tool, which draws elbows 78 and 92 toward one another against the action of spring 68. When the separated clamping jaws 72 and 88 are properly positioned around the tissue to be clamped, the force applied to elbows 78 and 92 is released and coil spring 68 urges clamping jaws 72 and 88 together with the tissue clamped between them.

Loop 86 functions to prevent misalignment of clamping jaws 72 and 88 by limiting arm 64 to two degrees of freedom to move relative to arm 66. As length 80 of arm 64 extends through loop 86, length 80, at its top and bottom, contacts lengths 97 and 99 of the loop between reverse bends 96 and 98. This contact is maintained as length 80 slides along the length of loop 86 during opening and closing of clip 60. Thus, arms 64 and 66 are permitted only two degrees of freedom to move, assuring alignment of clamping jaws 72 and 88 during placement and implantation of clip 60.

In the preferred embodiments of the present invention, resilient member 12 is made from titanium metal or a titanium alloy which are nonmagnetic and compatible with body -tissue and fluid. However, other

materials possessing the desired properties, can be used for a clip made in accordance with the present invention.

In addition, a surgical clip, constructed in accordance with the present invention, can take other forms from the ones described and illustrated to suit the particular needs of an application. For example, the clamping j aws can be oriented at an angl e or the j aws themselves can be curved or shaped to suit the shape and location of the tissue to be clamped.

The foregoing has set forth exemplary and preferred embodiments of the present invention. It will be understood, however, that various alternatives will occur to those of ordinary skill in the art with¬ out departure from the spirit and scope of the present invention.