Ornella Sizzi – Alfonso Rosseti
Introductions. One of the main drawbacks of the laparoscopic myomectomy is the length of the procedure which mostly depends on the size of myoma and type of morcellation.
Usually the suture and the myoma retrieval are the most time consuming parts of the entire procedure. The proposed posterior colpotomy is not suitable and does not correspond to the requirements of minimally invasive surgery. Furthermore, an infectious risk is involved which can lead to a delayed postoperative healing with intraabdominal adhesions. For this reasons, over the years, several instruments for tissue morcellation have been designed.
The first hand-activated morcellator was developed by Semm in 1973, but with this device morcellation of even small myomas required a very long time.
Later on, the design has been simplified: the SEMM Serrated Edged Macro Morcellator consists of a serrated edged cutting tube through which a myoma drill or a claw forceps are inserted. Tissue cylinders punched out of the myoma can thus be removed by manual rotation of the morcellator. Despite the progress, the morcellation part of the procedure continued to be time-consuming and tiring for the surgeon in case of big or multiple myomas. Cases of epicondylitis as severe “tennis elbow” have been reported from using the manual morcellator.
The morcellator knife is a classic lancet with an interchangeable blade, transformed into an endoscopic instrument that can be inserted easily through a 10-mm-diameter trocar. The blade can have an automatic retraction system which, if is set in the standby position, ensures security. The mass to be cut is held between two grasping forceps for easy cutting with the blade, under permanent visual control. After morcellation, extraction of the masses is performed through a posterior culdotomy or through an enlarged port. The system, even though inexpensive, is obviously time consuming and a more invasive extraction is necessary.
Of course, the removed tissue has to be suitable for histological examination. These systems are useful for myoma removal or for removal of the entire uterus after supracervical hysterectomy. It has to be point out that the task of the morcellator is to transform an ellipsoid form such as a myoma into a cylindrical one in order to be removed from the abdominal cavity through a trocar sleeve. In practise this process is influenced by several conditions.
Factors Influecing the Myoma Morcellation
- Tissue resistance
- Myoma volume
- Cannula diameter
- Torsional stres
The first variable factor is due to the consistency and tissue resistance of each myoma. This resistance depends on the proportion between connective component of the myoma and myometrial component and on the presence of calcifications. The resistance to cutting strength varies inside the myoma itself and mostly from myoma and myoma. It is obvious that another important factor is the myoma diameter. Considering the myoma as a spheroid, its volume will exponentially increase while increasing its diameter (Graphic 1).
Another factor influencing the speed of tissue removal is the diameter of the cutting cannula. The Graphic 2 shows that the volume of the cylinders of removed tissue varies with the diameter of the blade, being constant the length.
Moreover, it has to be stressed that, increasing the cannula diameter the length of the skin incision ( and especially of the fascial incision) will increase. Furthermore, the skin incision will be about 20% wider than the cannula diameter , resulting in greater postoperative discomfort. Obviously, the cutting strength is strictly connected to the rotating speed of the blade. On the other hand, an increasing of the torsional stress applied to the specimen together with a not constant tissue resistance can lead to tearing of the cylinder inside the cannula thus increasing the time of myoma removal.
In Table I the technical specifications of the electromechanical morcellators nowadays available are compared.
Both the Storz Systems use an engine developed from the otorhinolaryngologic surgery and the cutting blades of three different diameter allow a clock-wise or oscillating rotation.
The two Systems differ from each other because the Sawalhe Model is the only one system provided with a shielding sheath which is released as soon as the myoma gets loose from the cut tissue inside the cannula. This protection is intended for a greater safety in order to reduce the risks of damages to surrounding organs (iliac vessels, bowel) although no injuries have been reported so far from the use of electromechanical morcellators.
The two Wisap Models (Power and Moto- Drive) differ for the power supply, that for the Moto-Drive is provided with rechargeable batteries, and for the different idling speeds.
Moreover, the system is equipped with the wider range of diameters of the cutting tube (from 10 to 24 mm) with a dilation set for cannulas with Ø > 18 cm and the choice among toothed, serrated or plane edges depending on different tissue resistibility to morcellation.
The “Morce-Power 2306” distributed by Wolf, offers the choice between 10 and 15 mm cutting tube with toothed edge. The control switch of the drive unit is located on the handle, so that no footswitch is necessary.
The X-tractThe X-Tract Morcellator, distributed by Gynecare, consists of a motor drive and of a disposable morcellator with a cutting blade 15 mm in diameter. The operator can rotate the external sheath to allow an extension or retraction of the inner bladder, improving, even if not automatically, the safety of the device. The direction of rotation of the motor is user-selectable (clockwise or counter clockwise). The idling speed rotation can reach 1000 RPM. But the peculiarity that makes this device very efficient is the presence of an inner stationary sheath which stabilizes the torsional output of the motor at all speeds as the outer blade cuts the myoma with a coring action, reducing the risk of torsional stress and consequent tearing and allowing the removal of longer cylinders of tissue.
Analyzing the costs (Table II) , it is evident that the reusable systems in their entry-level version with a single blade of only one diameter are equivalent. On the other hand, the Wisap models when fully equipped with three different kinds of blades ranging from 10 to 24 mm in diameter reaches very high costs. In our opinion, these differences are justifiable only if the operator is able to choose the blade (toothed, serrated or plane) depending on the different consistency of the tissue to be morcellated.
Regarding the disposable instrument (Gynecare) it has to be pointed out that, despite a noticeably lower cost of the motor drive, it asks for a extra cost for each patient of € 413, quite higher than the cost of a spare blade of the other systems. Nevertheless, it has to be considered that, being equal the diameter of the blade, the X-Tract Morcellator (thanks to the inner stationary sheath) is the quickest system, providing a significant savings in operating room time of about 20%. In conclusion, considering a mean of operating room charges of € 12,9 per minute, the increased cost due to the disposable device will be justified by the reduced time for extraction only when the myoma is at least 7 centimeters in diameter.