Fig. 3.22. Firing concept similar to low gearing concept.
were not embraced by most surgeons, as they were cumbersome to use, and required trocars up to 18mm in diameter. This was due to the limits of standard tissue compression technology. The diameter of the clamping mechanism was proportional to the linear length of the staple line. The Endo GIA™ Universal utilized a unique tissue compression technology. To avoid the need for a large aggressive clamping mechanism, a tissue gap control mechanism, similar to an I-beam, is employed (Fig. 3.21). This mechanism physically connects the staple cartridge and anvil. As the instrument is fired, the tissue gap mechanism gradually compresses the tissues and brings the staple cartridge and anvil into proper apposition for precise staple formation along the entire length of the staple line. To reduce excessive force when firing on thick tissue, the firing mechanism gains a mechanical advantage using a low gearing concept. This simple concept is similar to the lower gearing of a bicycle, which makes climbing a steep incline possible. (Fig. 3.22).
Some surgeons utilize a circular stapler for the creation of the gastro-jejunal anastomosis in gastric bypass surgery. Several modifications to standard devices have been made to facilitate laparoscopic use. The Premium Plus Curved EEA™ stapler (Fig. 3.23) is an example of such a device. Seals have been added to prevent leaking of CO2 though the instrument body. To improve access to the operative site in laparoscopic procedures, a streamlined body was designed, increasing the working length of the instrument. A suture hole was added to the removable trocar to facilitate removal from the instrument and withdrawal from an access port. An additional suture hole was added to the center rod of the anvil. This enables the surgeon to guide the anvil into position utilizing a suture lead. Additional modifications facilitate mating the instrument and anvil during laparoscopy. A grasping notch was added to the center rod allowing the surgeon to control the anvil with standard laparoscopic forceps. Obtaining the proper angles to mate the anvil and stapler head is challenging in laparoscopy due to the fixed perspective of the access ports. A new geometry to the center rod has been employed to aid the surgeon in this task.
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