GB2254256A - Sonic scalpel - Google Patents

Abstract

A sonic scalpel comprises a handpiece incorporating a compressed gas driven vibrator and carrying a tip. A base unit which controls the gas supply to the handpiece, is connected to the hand piece by a flexible tube. The tube has a first internal channel for the supply of gas under pressure to the handpiece, a second internal channel for the return of exhaust gas to the base unit, and a third internal channel for the supply of a sterile liquid to the tip. An adapter is provided for releasably connecting the tube to the base unit and a source of the sterile liquid so as to permit the handpiece and tube to be sterilised.

Description

Title Surgical Implement Field of the invention The present invention relates to a surgical implement suitable for use as a scalpel when operating on certain types of body tissues, including the liver and kidneys.

Description of Prior Art During the last fifteen years hepatic resection for the removal of liver tumours has become more commonplace. There is evidence of significantly increased survival times after resections of single metastases for colon cancer. Despite this, resectional operations are usually carried out in specialist centres, although methods of surgical treatment are well established. The problem is that blunt dissection of the liver causes haemorrhage which is difficult to control. Liver sutures are difficult to retain and can cause problems with necrosis. Omantal patches may still lead to haematoma and abscess formation. Blood loss, necessitating large transfusions, adds to peri-operative and post-operative problems. All of these factors lead to high mortality rates.

The use of an ultrasonic tissue scalpel/aspirator has been recognised as a major advance in simplifying and increasing the safety of liver surgery. During 1987 it was used for 10% of the 7,000 liver resections performed in the United States.

The ultrasonic surgical aspirator is the most familiar machine. It was developed initially for neurosurgical procedures, and consists of a vibrating suction device which oscillates at an ultrasonic frequency of 23kHz. It fragments tissue in a radius of 1-2mm, preferentially destroying parenchymal tissue, and preserving collagen and elastic tissue in vessels and bile ducts. This allows clean dissection of blood vessels before precise ligation.

Instruments operating at ultrasonic frequencies generate heat either in the production of mechanical oscillations or by friction at the junction of tip and tissue. A coolant is therefore required. The destruction of tissue is aided by the principle of cavitation (bubble formation) that occurs within the fluid coolant. Selective effects occur in that the higher the water content of the target tissue the more easily it is fragmented. Blood vessels due to their high collagen content are relatively easily spared, especially as they provide tactile feedback to the surgeon.

In prior art instruments, the vibrations at the tip of the handpiece have been produced by using the magnetostrictive and piezo-electric effects.

In the first case the active tip is attached to a laminated ferromagnetic rod. This rod is placed into a handpiece in which an electrical coil is situated. The rod is initially magnetised by the passage of a direct current through the coil. A voltage alternating at an ultrasonic frequency is then superimposed on the direct voltage, causing the rod to undergo an alternating shape change, This is transferred to the working tip which then oscillates at an ultrasonic frequency.

Piezo-electric designs use the fact that crystals, such as quartz, change their shape if a voltage is placed across them. This has the advantage of making the units much smaller and compact. However they are more easily damaged.

The known surgical scalpels described above have certain disadvantages which stem from the fact that they require an electrical supply. Extensive safeguards need to be put in place to minimise the risk to the patient, especially if the patient has been fitted with a pacemaker. These precautions render the equipment very costly.

Object of the invention The invention seeks to provide a surgical implement which cuts through certain types of body tissue without causing extensive bleeding and which does not expose the patient to danger from electrical shock.

Summary of the invention According to the present invention there is provided a surgical implement comprising a handpiece incorporating a compressed gas driven vibrator and carrying a tip, and a base unit for controlling the gas supply to the handpiece, and flexible tubing connecting the handpiece to the base unit and having a first internal channel for the supply of gas under pressure to the handpiece, a second internal channel for the return of exhaust gas to the control unit, and a third internal channel for the supply of a sterile liquid to the tip, an adapter being provided for releasably connecting the tubing to the control unit and a source of the sterile liquid so as to permit the handpiece and tubing to be sterilised.

In the sonic scalpel of the invention vibration is caused by a compressed gas driven motor and this tends to place an upper limit of around 17KHz on the frequency of vibration, which is still within the range audible by humans.

Surprisingly, however, it has been found that the mode of vibration of a compressed air driven tool results in increased oscillation at the cutting tip and the different path of movement of the tip means there is no loss of destructive power despite decreased frequency as compared with prior art ultrasonic implements.

The term "cutting" is used herein somewhat loosely to refer to the separation of the tissue in certain organs. The instrument scalpel not in fact cut like a knife and indeed its main advantage is that unlike a knife it will pass through certain types of tissue but will have no effect on obstructions such as those presented by a nerve or a blood vessel.

It should be mentioned that handpieces with built-in compresses air motors causing a tip to vibrate at sonic frequencies are known and used in dentistry for descaling teeth. In the case of equipment intended for dental use, the compressed air a motor is driven by air from a compressor and the fluid supply is tap water. The equipment cannot therefore be used within a sterile environment.

Furthermore, it should be noted that when operated for descaling teeth, the tip vibration is responsible for breaking up of the scale on the teeth and the fluid supply is required only to cool the tip. By contrast, in the present invention, the vibration of the tip is not itself responsible for separation of the tissue and in the absence of a fluid supply would not be able to act as a scalpel.

The cutting action stems from the cavitation of the fluid at the tip.

As compared with the known ultrasonic instruments, the scalpel of the invention does not risk interference with monitoring devices or pacemakers because the energy for vibration is derived from a compressed gas rather than electrically.

The source of compressed gas is preferably a gas cylinder.

This has the advantage that the gas can itself be sterile and no risk is presented to the patient in the event of any leakage of gas from the handpiece. Furthermore, the equipment can continue to operate even in the event of a power cut.

The sonic surgical scalpel of the invention permits the construction of a small, light, and easily manoeuvrable handpiece of a similar shape, and slightly larger than a fountain pen, with a variety of interchangeable tip designs. The curve of the tip is useful in cleaning larger vessels along their length prior to ligation. The degree of hand control available gives tactile feedback to the surgeon, an advantage which is not achieved with prior art ultrasonic instruments.

The source of sterile liquid is advantageously a saline bag from which the saline solution is fed to the handpiece under pressure. This enables a readily available sterile supply of liquid to be used. Because of the adapter at the end of the handpiece tubing, the saline can be fed to the vibrating tip via the same tubing as supplies the compres sed gas to the motor. As a result of this construction, the handpiece, the tubing connecting it to the base unit and the saline supply can all be removed to ensure their sterility. The base unit need not itself be sterile.

The saline can be pumped to the handpiece by means of a peristaltic pump driven only when compressed air is supplied to the tip. Apart from generally simplifying the ability to sterilise the handpiece, the use of a standard saline bag adds safety in that the scalpel can continue to operate in the event of a power failure. The compressed air, being derived from a cylinder, does not of course depend on the mains supply and if the peristaltic pump should fail on account of a power cut then a blood pressure may be placed around the saline bag to pressurise it and maintain the flow of saline to the cutting tip.

The sonic surgical scalpel of the invention, with suitable tip design, has the ability to cut, rather than obliterate, tissue. There is less detritus produced and there is therefore no need for a built in aspirator. This avoids blockages and enables finer dissection.

Detailed description of the preferred embodiment The surgical scalpel of the preferred embodiment comprises a base unit having a housing containing various valves as described below, a battery, a mains transformer for maintaining the battery in a state of change and a motor powered by the battery for driving a peristaltic pump.

The pump is formed by a rotor driven by the battery powered electric motor but arranged outside the housing of the base unit. The rotor has rollers which roll around a hollow cylinder and a tube from a saline bag is placed in the space between the rollers and the cylinder wall to be squeezed between the two as the rotor is turned. As the rotor turns saline solution is pumped along the tube by the peristaltic action.

The base unit has an inlet connection for a cylinder of compressed oxygen and an output adapter onto which tubing leading to the handpiece used by the surgeon is connected.

The handpiece tubing is multi-channel tubing and has supply and return oxygen lines leading to the handpiece and a saline supply line. The oxygen supply and return lines are connected to the valves within the base unit and these valves are opened and closed under the control of the surgeon when the motor in the handpiece is to be driven. A pressure switch within the unit automatically responds to the oxygen supply to turn on the peristaltic pump so as to supply saline to the tip at the same time. The saline is fed into the adapter through a branch pipe and passes to the handpiece along the same tubing as the oxygen.

The tubing can thus be detached by disconnecting it and the adapter from the base unit and this allows the tubing, the adapter and the handpiece to be autoclaved. In this way, all the channels along which the saline can flow can be sterilised by autoclaving and the saline is itself pumped without coming into contact with non-sterile components.

The handpiece comprises a motor which consists of a central tube having tangentially directed holes to allow the compressed gas to escape. Surrounding the holes is a freely rotatable ring which is driven by the escaping gas through friction and spins about the tube at about 17 KHz. This induces vibration of the same frequency in a tip, the end of which undergoes a gyrating motion. The exhaust gas from the motor flows back down the flexible tube and is discharged by the base unit.

Saline at the same time is pumped onto the tip and flows towards the end of the tip. There the saline cavitates and is responsible for the selective cutting action of the instrument.

The instrument has been tested experimentally and found to have several important applications some of which are listed below.

In liver surgery, the scalpel has been successful is performing hepatic resections without any technique related problems. The operations were quick and involved minimal blood loss.

The scalpel has been found excellent for pancreatic dissection. The pancreas being an organ which ordinarily present severe difficulty.

In mesentery, the scalpel has proved useful in dissecting vessel arcades.

With the extensive work being done on minimally invasive surgical techniques at present, the scalpel is useful in laparoscopic surgery e. g gall bladder removal. In this context it should be mentioned that a rigid extension tubes can be fitted between handpiece and the flexible tubing to permit the entire handpiece, including the motor, to be inserted through a narrow opening in the body.

The sonic scalpel can also find application in the dissection of the terminal branches of the facial nerve as they pass through the gland, in neurosurgery and in surgery of the kidney and thyroid.

Claims (7)

1. A surgical implement comprising a handpiece incorporating a compressed gas driven vibrator and carrying a tip, and a base unit for controlling the gas supply to the handpiece, and flexible tubing connecting the handpiece to the base unit and having a first internal channel for the supply of gas under pressure to the handpiece, a second internal channel for the return of exhaust gas to the control unit, and a third internal channel for the supply of a sterile liquid to the tip, an adapter being provided for releasably connecting the tubing to the control unit and a source of the sterile liquid so as to permit the handpiece and tubing to be sterilised.

2. A surgical implement as claimed in claim 1, wherein the tubing and handpiece are autoclavable.

3. A surgical implement as claimed in claim 1 or 2, wherein the gas supply to the handpiece is derived from a pressurised container.

4. A surgical implement as claimed in any preceding claim, wherein the sterile liquid is saline contained in a flexible bag.

5. A surgical implement as claimed in claim 4, wherein the sterile fluid is pumped to the handpiece by means of a peristaltic pump acting on the outside of a tube connecting the bag to the adapter.

6. A surgical implement as claimed in claim 5, wherein the base unit comprises switching means for automatically operating the peristaltic pump when compressed gas is supplied to the motor in the handpiece.

7. A surgical implement as claimed in any preceding claim, further comprising rigid extension tubes insertable between the handpiece and the flexible tubing and having internal passages contiguous with the passages in the channels in the flexible tubing for the gas and liquid supplies to the handpiece.