Multiple bias surgical fastener

#The present invention relates to surgical fasteners for connecting body tissues, tissue and prostheses, tissue and graft or any combination thereof.

#Minimally invasive surgery has allowed physicians to carry out many surgical procedures with less pain and disability than conventional, open surgery. In performing minimally invasive surgery, the surgeon makes a number of small incisions through the body wall to obtain access to the tissues requiring treatment. Typically, a trocar is delivered into the body with a cannula. After the trocar pierces into the body cavity, it is removed and the cannula is left with one end in the body cavity.

#When a minimally invasive procedure is done in the abdominal cavity, the retroperitoneal space, or chest, the space in which the operation is performed is more limited, and the exposure to the involved organs is more restricted, than with open surgery. Moreover, in a minimally invasive procedure, the instruments used to assist with the operation are passed into the surgical field through cannulae. When manipulating instruments through cannulae, it is extremely difficult to position tissues in their proper alignment with respect to each other, pass a needle through the tissues, form a knot with the suture material once the tissues are aligned, and prevent the suture material from becoming tangled.

#FIG. 1A is a view of a surgical fastener according to the present invention;

#FIGS. 1B and 1C show a variation of the fastener of FIG. 1A;

#FIG. 2 is a view of a clip, absent of any biasing member, in a closed configuration;

#Tissue connectors such as those discussed in PCT publication nos. WO 99/62406 and WO 99/62409, as described above are also disclosed in currently copending and commonly assigned application Ser. No. 09/090,305, filed Jun. 3, 1998, which is incorporated herein, by reference thereto, in its entirety. Referring to FIG. 4, a fastener (e.g., fastener 20) such as that described in application Ser. No. 09/090,305 comprises a deformable wire 34 made of a shape memory alloy. A nickel titanium (e.g., Nitinol) based alloy may be used, for example. The Nitinol may include additional elements which affect the yield strength of the material or the temperature at which particular pseudoelastic or shape transformation characteristics occur. The transformation temperature may be defined as the temperature at which a shape memory alloy finishes transforming from martensite to austenite upon heating (i.e., Aftemperature). The shape memory alloy preferably exhibits pseudoelastic (superelastic) behavior when deformed at a temperature slightly above its transformation temperature. At least a portion of the shape memory alloy is converted from its austenitic phase to its martensitic phase when the wire is in its deformed configuration. As the stress is removed, the material undergoes a martensitic to austenitic conversion and springs back to its original undeformed configuration. When the wire is positioned within the tissue in its undeformed configuration, a residual stress is present to maintain the tissue tightly together. In order for the pseudoelastic wire to retain sufficient compression force in its undeformed configuration, the wire should not be stressed past its yield point in its deformed configuration to allow complete recovery of the wire to its undeformed configuration. The shape memory alloy is preferably selected with a transformation temperature suitable for use with a stopped heart condition where cold cardioplegia has been injected for temporary paralysis of the heart tissue (e.g., temperatures as low as 8-10 degrees Celsius).

#It is to be understood that the shape memory alloy may also be heat activated, or a combination of heat activation and pseudoelastic properties may be used, as is well known by those skilled in the art.

#The cross-sectional diameter of the wire and length of the wire will vary depending on the specific application. The diameter “d” of wire 34 may be, for example, between 0.001 and 0.015 inch. For coronary bypass applications, the diameter is preferably between 0.001 and 0.008 inch with a diameter D1 of the loop (FIG. 5) being between 0.0125 and 0.0875 inch. As shown in FIGS. 2 and 5, the wire 34 may have a circular cross-sectional shape and a generally spiral shaped configuration when in a closed position. The diameter D1 of the loop of the fastener 20, with coil 26, in its closed position is preferably sized to prevent movement between adjacent tissues. It is to be understood, however, that the wire may have other cross-sectional shapes such as rectangular, or may be formed from multiple strands. One end of wire 34, may include an enlarged portion 36 having a cross-sectional area greater than the cross-sectional area of the wire and diameter of the coil to resist the coil from passing thereover. Alternatively, enlarged portion 36 may have a cross-section that allows the coil to be pulled over the enlarged portion. For example, the cross sectional diameter of the enlarged portion may be about equal to the inside diameter of the coil. The enlarged portion 36 also may be provided to cooperate with a release mechanism, which is described in further detail with reference to the present invention below.