Vanderbilt University researchers have created magnetically-driven laparoscopic instruments.
The local magnetic actuation (LMA) approach requires two components: an external unit that is placed on a patient’s abdomen and an internal unit small enough to fit through the ¼ to ½ inch ports that are used in minimally invasive surgery. Each component carries a set of two strong permanent magnets. One pair anchors the internal unit to the inside of the abdominal wall, while the other pair provides the mechanical force that powers the device.
The new instruments deliver between 10 to 100 times more mechanical power than the electrical motors can provide. Compared to devices connected to sticks and wires, the magnetic devices can also be easily placed at optimal positions within the body.
A fountain-pen-sized magnetic organ retractor embodies the LMA principle. The device is designed to move organs out of the way when needed to perform an operation. For instance, the liver, which lies on top of the gall bladder, must be moved aside before the gall bladder can be removed.
The device consists of two parts: a fountain-pen-sized unit that is inserted into the body and a larger external unit that is placed on the patient’s stomach.
Both units contain powerful permanent magnets that are oriented so they attract one another. The magnetic force is strong enough to firmly anchor the internal unit against the inside of the abdominal wall directly below the external unit. The magnetic attraction between the two allows the user to accurately position the inside unit by rotating and sliding the external unit.
Both units also contain a second set of magnets that transmit the power. The magnet in the external unit is attached to the shaft of a powerful electric motor that causes it to spin. The magnet in the internal unit is also attached to a shaft, but one that drives a two-inch lever.
To retract an organ, the surgeon picks up the internal unit with a laparoscopic grasper and inserts it through the port into the body. When the surgeon maneuvers the internal unit close enough to the external unit, it snaps into position against the inner surface of the abdominal wall. The motor on the external unit is engaged, lowering the lever. Using standard laparoscopic instruments, the surgeon attaches one end of a line to the tip of the lever and the other end to a clip or suction cup fastened to the organ that must be moved. The electric motor is run in reverse and the lever retracts, pulling the organ into the desired position.
In the future, the team intends to apply the same principle to creating more complex instruments, such as laser and radio-frequency scalpels.