Surgery – Instruments – Cutting – puncturing or piercing
Reexamination Certificate
1999-03-09
2002-09-17
Thaler, Michael H. (Department: 3731)
Surgery
Instruments
Cutting, puncturing or piercing
C604S164040
Reexamination Certificate
active
06451041
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a medical apparatus and procedure. The present invention particularly relates to an apparatus and procedure for protecting a port site opening in the wall of a body cavity and preventing electrosurgical injuries caused by capactive coupling.
Minimally invasive surgical techniques, such as laparoscopic surgery, typically include the use of a trocar assembly. A trocar assembly includes a trocar (sometimes referred to as an “obturator”) positioned within the lumen of a cannula. The trocar and cannula are advanced through a body cavity wall so as to create a small hole or a port site wound therein. The trocar is then completely removed from the lumen of the cannula such that the cannula's lumen provides an entrance for laparoscopic instruments into the interior of the body cavity. The body cavity is then insufflated with an inert gas, such as CO
2
, to provide easier access to the organs contained therein. Once the surgery is complete the cannula is completely removed from the port site wound to rapidly desufflate the body cavity.
Surgery performed by using minimally invasive techniques is generally associated with lower postoperative morbidity, shorter postoperative stay, less postoperative pain, decreased cost, and quicker recovery as compared to “open” or conventional surgical techniques
(1,2,3,4)
. Because of the aforementioned advantages, these minimally invasive techniques are being applied to an increasing variety of all surgical procedures. For example, laparoscopic procedures for the resection of malignancies have emerged. In particular, laparoscopic colectomy for carcinoma of the colon has been developed, and it has been reported that the initial results of these procedures have advantages over operations performed in the traditional open manner
(5,6,15)
. Moreover, it is hoped that the long term results of these procedures will be comparable, or better than, those performed in the traditional open manner.
However, the development of laparoscopic surgery for cancer has been hindered because of the major concern regarding the implantation of tumor cells in the port site wound
(2,3,6,7)
. In fact, numerous port site recurrences have been documented in the medical literature heretofore, and subcutaneous metastases after laparoscopic resection of malignant tissue is associated with a decreased survival rate for patients who may have had a curative cancer
(2,3,6,7)
. Specifically, the medical literature reports that the incidence of tumor cell implantation ranges from as high as 20% to as low as 0%
(8)
, The studies generating the aforementioned data utilized highly skilled and experienced laparoscopic surgeons practicing at major university programs. However, in spite of utilizing highly skilled and experienced laparoscopic surgeons, the data indicates that the incidence of tumor cell implantation in the surgical wound is greater when employing laparoscopic techniques as compared to when conventional surgical techniques are used (i.e. 0.6% implantation incidence for conventional techniques
(9)
compared to 1% incidence for laparoscopic techniques
(10 )
).
Several mechanisms may be responsible for the above discussed implantation of tumor cells in the port site wound. For example, minimally invasive surgical techniques for treating cancer require the insertion and removal of laparoscopic instruments or cameras through the lumen of the cannula. In addition, these surgical techniques require that the cannula itself be moved relative to the port site wound such that the cannula is advanced further into, or withdrawn from, the body cavity
(11)
. Moving the cannula in the above described manner facilitates a surgeon's ability to optimally locate instruments within the body cavity thereby helping to ensure the successful completion of the medical procedure. However, the aforementioned manipulations of the laparoscopic instruments and cannula may result in the exposure of the port site wound to exfoliated cancer cells which creates a risk of implanting tumor cells in the walls of the port site wound
(11, 12)
. In particular, exfoliated cancer cells may adhere to and thus contaminate a portion of the exterior surface of the cannula
(11, 12)
. The contaminated portion of the exterior surface of the cannula may then be advanced into contact with the port site wound during insertion and removal from the port site wound
(11, 12)
. This contact may dislodge the exfoliated cancer cells from the exterior surface of the cannula and thus cause the exfoliated cancer cells to be implanted in the port site wound
(11,12)
.
Furthermore, studies have shown that a physician may undergo a significant learning curve before becoming proficient in the performance of laparoscopic surgery, such as cancer surgery
(3, 13)
. As a result, a relatively inexperienced surgeon may have a tendency to manipulate or handle a tumor to a greater degree during a surgical procedure than an experienced surgeon. In addition, an inexperienced surgeon may have a tendency to insert and withdraw an instrument through the lumen of the cannula a greater number of times than an experienced surgeon. The above described increased manipulation of the instrument or the tumor can result in a greater incidence of tumor cell implantation in the port site wound
(11,12)
.
Regardless of how these cells contaminate the wound, once implanted therein, viable tumor cells can cause a subcutaneous metastases or “port/extraction site recurrence” after the resection of malignant tissue. These “port/extraction site recurrences” have delayed the advancement of laparoscopic cancer surgery
(2, 6, 7, 8, 9, 10, 11, 12)
. Therefore, it is desirable to provide an apparatus which will protect a port site wound from tumor cell implantation while allowing a surgeon to optimally locate instruments within the body cavity for successful completion of the medical procedure.
Furthermore, laparoscopic surgery performed for general surgery, gynecological surgery, urological surgery, or any other intra-abdominal surgery is associated with a small but real incidence of port site wound infection
(1)
. The infecting bacteria causing these illnesses can contaminate the port site wound in the same manner as discussed above with regard to tumor cell contamination, and these infections can increase a patient's morbidity and consequently the length of a patient's hospital stay, thereby considerably increasing their hospital bill.
Moreover, the use of electrosurgical techniques are increasingly being used in conjunction with laparoscopic techniques. While the combination of electrosurgical and laparoscopic techniques has many advantages, it is recognized that potentially serious electrosurgical injuries can occur during these types of laparoscopic operations. In particular, the overall incidence of recognized electrosurgical injuries is between one and two patients per 1,000 operations
(16)
. However, the total incidence of these types of injuries (i.e. the sum of recognized and unrecognized injuries) may be significantly higher since the majority go unrecognized at the time of the electrical insult and commonly present three to seven days afterward with fever and pain in the abdomen. These injuries have significantly increased the cost of health care.
The pathophysiology of some of the electrosurgical injuries received during laparoscopic surgery appear to involve the property of capacitance
(16)
. A capacitor exists whenever a nonconductor separates two conductors. During minimally invasive surgery procedures a capacitor situation may be created by a surgical instrument. For example, the active electrode used in electrosurgical procedures is surrounded by nonconductive insulation, and the nonconductive insulation is surrounded by conductive metal cannula thereby creating a capacitor. The capacitor can create an electrostatic field between the two conductors (i.e. the active electrode and the metal cannula). As a result, a current in one conductor can, through the e
Castaneda Javier
Moenning Stephen P.
Palmer Matthew A.
Moenning Stephen P.
Thaler Michael H.
Wood Herron & Evans L.L.P.
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