Abstract:
A trocar cannula is disclosed. The trocar cannula comprises a cannula having at least one tab member formed therein. Each tab member is configured to provide a retention force between the cannula and tissue when the tab member is placed in a deformed position. The tab member is selectively moveable between a relaxed position, in which the cannula may be moved with respect to the tissue, and the deformed position, wherein the tab member frictionally engages the tissue.

Description:
TECHNICAL FIELD 
     The present disclosure generally pertains to microsurgical instruments. More particularly, but not by way of limitation, the present disclosure relates to microsurgical instruments used in posterior segment ophthalmic surgery. 
     BACKGROUND 
     Many microsurgical procedures require precision cutting and/or removal of various body tissues. For example, vitreoretinal surgery often requires the cutting, removal, dissection, delamination, coagulation, or other manipulation of delicate tissues such as the vitreous humor, traction bands, membranes, or the retina. The vitreous humor, or vitreous, is composed of numerous microscopic fibers that are often attached to the retina. Therefore, cutting, removal, or other manipulation of the vitreous must be done with great care to avoid traction on the retina, the separation of the retina from the choroid, a retinal tear, or, in the worst case, cutting and removal of the retina itself. 
     Microsurgical instruments, such as vitrectomy probes, fiber optic illuminators, infusion cannulas, aspiration probes, scissors, forceps, and lasers are typically utilized during vitreoretinal surgery. These devices are generally inserted through one or more surgical incisions in the sclera near the pars plana, which are called sclerotomies. To establish an entry through the sclera into the posterior segment of the eye, trocar cannulas are typically used. The trocar cannula generally serves as a pathway through which various microsurgical instruments may be delivered to the posterior segment of the eye. 
     Typically, a surgeon relies upon friction between an outer surface of the trocar cannula and the sclera of the eye to maintain the trocar cannula&#39;s position within the eye. However, during an exchange of the microsurgical instruments, there is a risk that the trocar cannula may be inadvertently moved, which may cause injury to the patient. To insure against inadvertent movement of the trocar cannula, in prior art systems a surgeon grasps a cannula hub with a pair of forceps during the instrument exchange to maintain the position of the trocar cannula. Such a practice requires an extra step in the surgical procedure, thereby increasing the length of surgery. In addition, this practice also requires an extra hand to hold the forceps. Therefore, a need remains for an improved retention mechanism for a trocar cannula. 
     BRIEF SUMMARY 
     A trocar cannula is disclosed. The trocar cannula comprises a cannula having a tab member formed therein. The tab member is configured to provide a retention force between the cannula and tissue when the tab member is placed in a deformed position. The tab member is selectively moveable between a relaxed position, in which the cannula may be moved with respect to the tissue, and the deformed position, wherein the tab member frictionally engages the tissue. 
     In one exemplary arrangement, the tab member is biased into the relaxed position, but may be selectively moved into the deformed position by introduction of a medical instrument into the cannula. Once in the deformed position, the tab member frictionally engages tissue to retain the cannula with respect to the tissue. Upon withdrawal of the medical instrument from the cannula, the tab member is automatically returned to the relaxed position whereby the cannula may be moved with respect to the tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure will now by described by way of example in greater detail with reference to the attached figures, in which: 
         FIG. 1  is a cross-sectional view of an embodiment of a trocar cannula device; 
         FIG. 2  is a is an enlarged cross-sectional view of area  2  of the trocar cannula device of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the trocar cannula device of  FIG. 1  with a medical instrument positioned therein. 
         FIG. 4  is an end view of the trocar cannula device and medical instrument of  FIG. 3 . 
         FIG. 5  is a top view of the trocar cannula device and medical instrument of  FIG. 3 . 
         FIG. 6  is an enlarged cross-sectional view of area  6  of the trocar cannula device and medical instrument of  FIG. 3 . 
         FIG. 7  is an enlarged top view of area  7  of the trocar cannula device of  FIG. 5 . 
         FIG. 8  is an enlarged cross-sectional view of a portion of the trocar cannula device and medical instrument of  FIG. 3 , with a retaining tab engaged with tissue. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed devices and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
       FIG. 1  illustrates an exemplary embodiment of a trocar cannula device  10 . Trocar cannula device  10  is generally defined by an open proximal end  12  and an open distal end  14  and comprises a cannula section  16  and an introduction section  18 . Cannula section  16  includes a generally hollow bore  20  defined by an internal surface  22 . Cannula section  16  opens into introduction section  18 . In one exemplary arrangement, a transition section  24  connects cannula section  16  to introduction section  18 . 
     Introduction section  18  has a generally hollow chamber  26  defined by an internal surface  28  and an opening  30  positioned at proximal end  12 . Surrounding opening  30  is an optional flange member  32 . Internal surface  28  may optionally be configured with a protrusion  31  (shown in phantom in  FIG. 1 ) that mates with a corresponding well (not shown) disposed on an external surface of  52 . Details of protrusion  31  are discussed in commonly owned U.S. patent application Ser. No. 11/624,485, the contents of which are incorporated by reference in its entirety. 
     Cannula section  16  is defined by a first internal diameter d 1 . Introduction section  18  is defined by a second internal diameter D 2 . In one exemplary arrangement, first internal diameter d 1  is less than second internal diameter D 2 . In one exemplary arrangement, trocar cannula device  10  is formed as a unitary member such that cannula section  16  and introduction section  18  are integrally connected together. Trocar cannula device  10  may be constructed from surgical stainless steel or other materials suitable for surgical applications. 
     As discussed above, during surgical procedures, trocar cannula device  10  is positioned within the patient&#39;s eye to provide a pathway for delivery of surgical instruments. To insure that trocar cannula device  10  is prevented from inadvertent dislodgement during a surgical procedure, trocar cannula device  10  is provided with at least one cantilever tab member  34 . In some embodiments, such as that shown in the accompanying drawing figures, trocar cannula device  10  is provided with multiple cantilever tab members  34 . Each cantilever tab member  34  is configured to increase a retention force required to remove trocar cannula device  10  from the sclera  36  (see  FIG. 8 ) of the eye. 
     Details of cantilever tab member  34  will now be discussed. Cantilever tab member  34  is formed from a portion of a sidewall  38  of cannula section  16  and comprises a mechanical finger  40  that includes an upwardly biased end  42 . Tab member  34  is formed by a generally U-shaped cut-out  44  that permits end  42  to move with respect to side wall  38 . As seen in  FIG. 2 , cantilever tab member  34  includes a crimp section  46  that separates mechanical finger  40  from the portion of sidewall  38 . Crimp section  46  is formed so as to pre-bias end  42  upwardly. Referring to  FIG. 5 , a bend area  48  is formed in sidewall  38 . Bend area  48  is configured to bias cantilever tab member  34  inwardly with respect to an outside surface  50  by a predetermined distance when trocar cannula member  10  is in a relaxed state (best seen in  FIG. 2 ). More specifically, in the relaxed state, cantilever tab member  34  (including biased end  42 ) sits below outer surface  50 , thereby permitting trocar cannula member  10  to be easily moved with respect to sclera  36 . In one embodiment, a slight clearance C is provided between an uppermost edge of biased end  42  and outside surface  50  (see  FIG. 2 ). 
     However, referring now to  FIGS. 3-8 , when an instrument  52  is positioned within trocar cannula device  10 , mechanical finger  40  is deflected outwardly from outside surface  50  in the radial direction such that biased end  42  extends outwardly from outside surface  50 . More specifically, instrument  52  contacts crimp section  46  as it is inserted into bore  20 , forcing crimp section  46  upwardly, and consequently forcing biased end  42  upward into a deformed position (seen best in  FIGS. 6 and 8 ) such that biased end  42  may grip sclera  36 . The radial deflection of mechanical finger  40  creates a mechanical mechanism for increasing the retention force between trocar cannula  10  and sclera  36  as compared to a simple frictional engagement of outside surface  50  of trocar cannula  10  and sclera  36 . The added retention force from mechanical finger  40  eliminates the need to have the surgeon retain trocar cannula  10  with forceps or other means during an instrument exchange. The elimination of this step serves to reduce procedure time, as well as provide the surgeon with a free hand for handling additional instruments. 
     Once a procedure is complete, and all instruments are removed from trocar cannula device  10 , cantilever tab member  34  automatically returns to the relaxed position whereby mechanical finger  40  (including biased end  42 ) is disposed below outer surface  50 . The return feature is due to the configuration of bend area  48 . Once in this position, trocar cannula device  10  may be easily removed from the patient. 
     In one exemplary arrangement, the instrument  52  is an infusion cannula that permits irrigating fluid to enter the posterior segment of the eye to maintain a suitable intraocular pressure. However, it is understood that other microsurgical instruments may also be used with trocar cannula device  10 . 
     It will be appreciated that the devices and methods described herein have broad applications. The foregoing embodiments were chosen and described in order to illustrate principles of the methods and apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize methods and apparatuses in various embodiments and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been explained and illustrated in exemplary embodiments. 
     It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that this invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims.