GB2164855A - A trocar for forming an opening through the skin - Google Patents

Abstract

A trocar, which is used for forming an opening through the skin of a patient, and in some cases for distending the opening after it has been made has components which can be opened by a lever mechanism and which do not increase in cross-section towards the distal end even in the open condition. Consequently, after operation of the lever mechanism to distend an opening, it is still possible to slide the trocar out of the opening without tearing the skin. The lever mechanism is arranged so that there is a central opening through which it is possible to pass a tube when the trocar components are in the open condition. <IMAGE>

Description

SPECIFICATION A surgical appliance for forming an opening through the skin The present invention relates to a surgical appliance and to a method for forming an opening through the skin of a patient or animal.

The invention is applicable to the treatment of humans and will be so described hereinafter, but it should be understood that, with appropriate modifications, it could also be applied in veterinary practice. Whilst the method and apparatus can be used in a variety of surgical operations, it is particularly useful for introducing drainage tubing, scopes and instruments, wire or other surgical and exploratory apparatus into cavities, and it may be used for instance for introducing drainage tubing into the thoracic cavity.

Taking the insertion of a thoracic drain as an example, the current method of drain insertion requires initially the cleaning of the skin at the site of insertion under sterile conditions.

The commonly used sites are in the anterior axillary line through the fifth intercostal space; anteriorly in the mid clavicular line; the second intercostal space, or posteriorly through the first intercostal space. Local anaesthetic is infiltrated into the intercostal space, traversing the upper border of a rib. A two centimetres long incision is made at the site, and two sutures are inserted, one for securing the drain in place, and a second, more loosely applied, purse string suture for use in subsequent closure of the incision when the drain is removed. Dissection is made through the connective tissue and intercostal muscle to the pleura. The chest drain can be inserted by means of an Argyle-type assembly, in which the drain is placed over a long trocar and forced through the incision into the pleural space, and the central trocar then removed.

Alternatively, it can be introduced using the Tudor-Edwards assembly in which a trocar with surrounding cannula are pushed through the incision into the pleural space, the trochar withdrawn and the drainage tube is then passed through the cannula and the cannula removed over the drain leaving the drain alone in situ. Both the Argyle trocar, and the Tudor Edwards trocar and the cannula can be made to various sizes to accepted standard catheters, such as 24F and 28F of sizes 8 millimetres and 9.3 millimetres in diameter respectively. Once the drain is in situ it is secured with a suture and connected to the underwater arm of an underwater seal drain.

When the lung is fully expanded, the drain is withdrawn and the purse string suture tightened to occlude the aperture.

The disadvantages of the available methods of thoracic drain insertion mentioned above are: (i) Despite making a relatively large incision at the site of insertion, it is not possible to insert the drain and trochar, which is approximately 1 centimetre diameter, without exerting an appreciable force.

(ii) A large incision with adequate dissection and the insertion of the drain results in almost inevitable infection at the site of insertion and increased risk of haemorrhage.

(iii) A large incision may make chest drain insertion less hazardous as less force is required on insertion, but the chest drain will not function unless there is an airtight seal around its site of insertion in the chest wall.

Further, unless the chest wall grips the drain tightly, it is likely to fall out or exert undue tension on the securing suture.

(iv) The major danger of inserting the Argyle chest drain and trocar is that:- as the 1 centimetre diameter drain is forced through the intercostal muscles, there is a sudden yielding of the muscles as the trocar enters the chest cavity. Unless the forward motion is rapidly and expertly controlled, there is a great danger of perforating the lung, major vessels or the heart, all of which are recognised complications.

(v) On withdrawal of the chest drain, a channel up to 1 centimetre diameter may be left at the drain insertion site (this is between the chest cavity and the atmosphere). The equalisation of pressures can result in the recollapse of the lung unless the purse string suture is pulled tight simultaneously with withdrawal of the chest drain to occlude the aperture. This is a difficult procedure especially if done single handedly.

(vi) Purse string sutures, when tightened around a line incision give very poor approximation of wound edges with increased risk of infection, poor haemostasis, poor wound healing and result in an ugly scar.

(vii) The whole procedure is time consuming, dangerous and frightening, and often painful to the patient.

There have been proposals for expansible trocars which can be inserted through the patient's skin and intercostal muscles in a collapsed condition and then expanded to enlarge the opening for the entry of a drain tube.

However, these proposals have not resulted in practical surgical apparatus, probably because they were too complicated and in some cases would cause tearing of the skin tissue. It is one of the objects of the present invention to provide an expansible introducer which is of simple construction and which has various clinical advantages in use over the commonly used Argyle and Tudor-Edwards apparatus.

According to this invention a surgical appliance for forming an opening through the skin of a patient or animal comprises a trocar having a distal end intended to penetrate the skin; the trocar comprising at least two component parts or portions adapted to move relatively to each other between a closed con dition and an open condition, and in which, when the trocar components are in the open condition there is no substantial increase in the cross-section of the trocar towards the distal end, a lever mechanism being connected to the trocar component parts or portions for producing the movement from the closed to the open condition.

The trocar is inserted through the skin of the patient with its component parts or portions in the closed condition, which facilitates entry of the trocar through the incision. Once it has been inserted, the trocar components are opened by operation of the lever mechanism, and this distends the skin around the incision to form an opening of a required shape and size which will be determined by the shape and sixe of the trocar when its components are in the open condition. Thus the reference to forming an opening as used herein includes the distending of the incision to the required shape and dimensions.

Preferably the arrangement is such that the trocar does not increase in cross-section towards its distal end at any position from its closed to open conditions. It is further preferred that the trocar tapers towards its distal end in the closed condition. In fact, the trocar may taper towards its distal end even in the open condition, though it may be substantially parallel-sided in the open condition.

According to another preferred feature the arrangement is such that there is a channel through the trocar components when they are in the open condition.

Preferably the lever mechanism is so arranged that there is a central opening through it which when the trocar components are opened, is in continuation of the central channel through those components, whereby it is possible to pass a tube through the entire appliance when the trocar components are open.

It is an important feature of the invention that there is no significant increase in any cross-sectional dimension of the trocar towards the distal end when it is in the open condition because this means that it is possible to withdraw the trocar without having to close it (which will be impossible if a tube of the largest size with which the appliance may be used is passed through it) and without tearing the skin of the patient. United Kingdom Patent No: 1 401 026 describes a trocar which can be opened when it has been inserted, but in the open condition, the distal end of the trocar is splayed and it could not be withdrawn from the patient in this condition without tearing the skin.

It is further preferred that the lever mechanism is adapted to hold the trocar components in a substantially parallel relationship with each other throughout the opening movement. In the preferred construction, there are two trocar components and the lever mechanism is adapted to produce movement of one of these components relatively to the other.

According to another preferred feature of the invention, each trocar component has a blade-like configuration, the blades being bowed outwardly as seen in lateral cross-section, so that in their closed position, the components contact each other only along the longitudinal edges, and in the open position, they approximate in cross-section to parts of an annulus, the internal diameter of which is large enough for the passage of a drain tube.

The trocar components may be detachable so that they can be replaced if required.

According to another preferred feature of the invention the distal extremities of the trocar components are sharpened and formed with a cutting edge or edges which extend across substantially the full width of the trocar.

One construction comprises: a body to which a handle is attached; a stationary trocar component attached to the body; a movable trocar component having a block slidable in a radial slot in the body; a lever pivoted on the body, and a mechanical connection between the lever and the block for converting the turning motion of the lever into radial motion of the block. Preferably the mechanical connection comprises a pin-and-slot arrangement.

It is further preferred to provide a latching device adapted to hold the trocar components in the fully open and/or fully closed position.

In an alternative construction, there is a stationary trocar component and a movable trocar component connected by a pair of links forming a parallelogram arrangement. Preferably a hand grip is connected to one of the links for the purpose of moving the trocar components apart. There may also be a pressure pad connected to one of the links for the purpose of applying pressure to close the trocar components one on the other. In the preferred construction a hand grip extends from one of the links and can be gripped by the user in the same hand as the appliance handle to provide a gripping arrangement for opening the trocar components and a thumb pressure pad extends from the other link so that thumb pressure on it closes the trocar components.

Two constructions of surgical appliance in accordance with the invention, will now be described by way of examples only, with reference to the accompanying drawings, in which: Figure 1 is a side view of an appliance in the closed condition, Figure 2 is a section on the line Il-Il in Figure 1, Figure 3 is a section on the line Ill-Ill in Figure 1, Figure 4 is a section on the line IV-IV in Figure 1, Figure 5 is a section on the line V-V in Figure 1, Figure 6 is a longitudinal section through the appliance in an open condition, Figure 7 is a view similar to Figure 2 but showing the open position, Figure 8 is a view similar to Figure 3 but showing the open position, Figure 9 is a view similar to Figure 4 but showing the open position, Figure 10 is a view similar to Figure 5 but showing the open position, Figure 11 is a side view of a second appliance in the closed position, Figure 12 is a plan view of the appliance shown in Figure 11, Figure 13 is an end view looking in the direction of the arrow XIII in Figure 11, and Figure 14 is a longitudinal section through the appliance shown in Figures 11 to 13, but with the appliance in the open condition.

The appliance shown in Figures 1 to 10 of the drawings is intended for use in introducing items such as drain tubes, through the skin tissue of a patient. Perhaps the most common application of an appliance of this nature is as a a thoracic drain introducer, in those instances where an intercostal catheter (drain tube) has to be introduced into the thoracic cavity, for example to enable a collapsed or partially collapsed lung to be re-expanded by removing trapped intra-thoracic air or fluid. As will hereinafter appear however, the appliance is not limited to use in thoracic invasion procedures.

The appliance has a body 10 with which there is combined a handle 12, a pair of trocar components 14 and 16, and an operating lever 18. All the major components are made in stainless steel, or other noncorrosive material.

The whole apparatus is small enough to be gripped by the handle 18 in the hand of a person (usually a hospital house doctor) who is using the appliance. The lower trocar component 16 is fixed to and extends cantilever fashion from the front end of the body 10.

The upper trocar component 14 extends cantilever fashion from a block 22, at what will be regarded as the rear end of the trocar component. The block 12 is located in a slot 24 formed in the body 10, and has a pair of depending lugs 26 and 28 which are received in rebates 30 and 32 of the body 10. A thickened proximal part 34 of the upper trocar component 14 extends through a slot 36 formed in the forward end of the body 10, and as is clear from Figure 3, the slot 36 is open at the top and closed at the bottom. By virtue of this arrangement, the block 22 is able to move vertically in the slot 24 in the body 10, but is constrained by that slot, and by the engagement of the thickened proximal part 34 with the sides of the slot 36, so that it can only make a radial motion. Hence, the upper trocar component 14 can move towards and away from the lower component 16 (i.e.

in a radial direction having regard to the longitudinal axis passing through the appliance), but during any such movement, the two components 14 and 16 will always remain in a parallel arrangement. It will be apparent from Figure 1, that the outsides of the components 14 and 16 are parallel-i.e. there is no increase in diameter towards the pointed distal end.

Because the upper component 14 remains in parallel relationship with the lower components through any movement it may make, the parallel relationship of the outside is maintained in the open condition. This is a significant feature of the construction, as will hereinafter appear.

The lever 18 has a bifurcated forward portion 38 pivoted on a fulcrum pin 40, and formed with kidney-shaped slots 42, which engage on pins 44 projecting from the block 22. By virtue of this arrangement, when the lever 18 is pulled upwardly towards the handle 12, from the position shown in Figure 1 to that shown in Figure 6, the pin-and-slot connection causes the block to be moved radially upwardly, thus opening the trocar components 14,16 away from the position shown in Figure 2 to that shown in Figure 7.

Each of the blade-like sections of the trocar components 14 and 16 is bowed outwardly, as shown in Figures 2 and 7, the arrangement providing that when the appliance is closed as shown in Figures 1 and 2, the trocar components engage with each other only along their longitudinal edges, and the composite trocar then has a minimum depth. However, the arrangement of the blade-like portions of the trocar components is also such, that in the opened position shown in Figure 7, they form parts of an annulus, the bore of which is large enough to accept a drain tube (not shown).The distal extremities of the components 14 and 16 are backed-off and sharply tapered, so that as seen in plan they form a point (when in the closed condition) and they have two cutting edges, which together extend across the full width of the trocar.It will also be observed, that when the block 22 is moved to the open position shown in Figure 9, there is a bore 46 through the body 10, aligned with the space between the then open trocar components 14 and 16, through which the drain tube can be passed. This bore 46 is continued through the handle 12, so that in the open condition, it is possible to thread a drain tube through the appliance from the handle end and out at the trocar end. The bore 46 is of such a diameter that a drain tube of the size the appliance is adapted to receive is a sliding fit within it. This means that once a drain tube has been inserted in the hole 46, it will remain there unless deliberately removed.

Each of the components 14 and 16 could be made as a detachable unit fitted into its proximal part 34, so that the components can be changed if required.

Finally, the appliance includes a latching collar 48 which is rotatable on the body 10, and has a finger 50 (see Figure 5) whereby the operative can rotate it using the thumb of the hand which is gripping the handle 12 and the lever 18. The latching collar 18 has a cam portion 52 which is adapted to engage with the lever 18 when the latter is in the "closed" position shown in Figure 1, for the purpose of preventing opening of the trocar components 14 and 16. Hence, if the handle 12 is gripped, the thumb pressure applied to the finger 50, to hold the cam in engagement with the lever 18, the trocar components are held securely in the closed condition, in which they can be introduced readily through an incision made in the skin tissue of the patient.If it is required to expand the trocar components 14 and 16 after insertion, then the latching collar 48 must be rotated, to release the cam portion from the lever 18, so that it is then possible for the operative to move the lever 18 towards the handle 12, opening the trochar components as previously described. In the fully open position, the collar 48 can be turned to the position shown in Figure 10, where a lip 54 on the lever 18 is received in a recess 56 in the collar 48. This then prevents closing of the trocar components, until the collar 48 is deliberately unlatched from the lever 18.

A short rubber sleeve 35 is provided, for fitting over the enlarged portions 34 of the trocar components. The bore of the sleeve is such that it fits tightly around the thickened portions 34 in the closed condition. When the components 14 and 16 are opened to the position shown in Figure 6, the sleeve is distended by the thickened portions 34. Hence the sleeve provides a constraining force urging the components 14 and 16 into the closed condition. However, the sleeve 35 is completely removable and will not always be used in practice.

Prior to insertion of the drain, the site of insertion is cleaned under sterile conditions and local anaesthetic is injected into the intercostal space. The appliance is adjusted to close the components 14 and 16 on to each other, and one end of a drain tube (not shown) is pushed into the bore 46. The trocar is then pushed through the skin and intercostal muscles into the thoracic cavity. This insertion is facilitated because the distal end of the trocar is acutely sharpened, and the thickness of the trocar is quite small in comparison to the currently available trocars used forthoracic drain insertion. As the pointed end of the trocar penetrates the skin, its cutting edges cut a hole as wide as the trocar.This means that the periphery of the hole formed through the skin is twice as long as the width of the trocar-which is of assistance when that hole is distended. The trocar is prevented from being inserted beyond the desirable length by engagement of the enlarged portions 34 (or the rubber sleeve fitted on those portions) with the skin. After insertion, the components 14 and 16 are separated radially by operation of the lever 18 as previously described. In separating the components 14 and 16, the skin and intercostal muscles are stretched, creating a channel into the intercostal space.

This channel must be large enough to accept the drain tube, and the components 14 and 16 are in fact opened until it is possible to slide the tube through the space between them. The drain tube previously pushed into the bore 46, can then be slid through that bore and through the space between the components 14 and 16, so that it passes into the thoracic cavity. The expansion of the trocar causes the incision to be distended, but if, for example, the distance around the periphery of the distended incision is equal to three times the width of the trocar components, then the periphery of the hole is increased by 50%, which in most instances can be accommodated without tearing the skin. When the drain tube has been inserted the appliance itself can be withdrawn around the drain tube, leaving the drain tube alone in situ.Since the components 14 and 16 are parallel sided even in the opened condition, there should be no tearing of the skin during withdrawal. The skin and the intercostal muscles which have been stretched will then contract on to the drain tube gripping it firmly. The exposed part of the drain may then be further secured to the chest wall with adhesive tape, or other known means, and connected to the underwater arm of an underwater seal drain.

The rubber sleeve 35 has been described as providing a constraining force for the trocar components 14 and 16, and also in some instances it provides a location for the trocar during insertion. Another feature of the sleeve 35 is to seal against the skin around the incision (when the trocar is fully inserted) and then to cover the opening sides of the trocar when the components 14 and 16 are expanded to prevent ingress of air through the open sides into the pleural space. For some purposes, the sleeve 35, could project further towards the distal end than the enlarged portions 34.

In the above specific description, reference has been made to the introduction of a thoracic drain. As has been pointed out however, the use of the appliance is not restricted to the insertion of thoracic drains, and indeed it can be used to introduce other surgical items besides drain tubes. For instance, a guide wire may be passed through the patient's skin to an organ on which an operation is to be performed, and the appliance (in the closed condition) threaded over this wire. The trocar can then be used as previously described and once it has penetrated the tissue and intercostal muscles the trocar and any tube or other item fed through it will follow the guide wire to the organ concerned. In one method of use, the trocar portion of the appliance may be guided into the renal pelvis for the introduction of a tube, and extraction of a stone.

Similarly the appliance can be used for the insertion of a tube into the kidney pelvis for the extraction of a stone. Use of the appliance in this manner is likely to produce less complications than use of known apparatus for the removal of stones.

Further uses of the appliance in accordance with the invention include: ~introduction of drains into collections of pus or fluid in the abdomen, pelvis or under the diaphragm, ~introducing tubing into the abdomen for peritoneal dialysis, ~introducing laparoscopes for investigation inside the abdomen, and in some cases to treat lesions or take biopsies, ~introducing cystoscopes into the bladder suprapubically for viewing and treating bladder tumours, removing stones and the like, rather than introducing the scope through the urethra, which itself often results in damage to the urethra. Suprapubic catheters may simultaneously be introduced this way.

If the appliance has a blunt ended trocar (instead of the sharpened end described above) it may be used for the dilation of ducts, vessels or openings.

In Figures 11 to 14, there is illustrated an alternative construction, which employs a parallel motion linkage rather than the pin-and-slot method for actuating the trocar components.

The appliance has a combined body and handle 80, and the lower, stationary trocar component 82 forms a forward extension of the body 80, and is therefore rigid with the handle. In shape, the lower trocar component 82 is identical with the trocar component 16 with reference to Figures 1 to 10. There is also an upper trocar component 84, which in shape and construction is identical with the upper trocar component 14 illustrated in Figures 1 to 10, and the upper trocar component 84 extends forwardly from a block 86, which in the closed condition of the appliance (shown in Figure 11) rests on a part of the combined handle and body 80.

A bore 88 formed longitudinally through the handle 80, and the inside arcuate face 90 of the lower trocar 82 forms a continuation of part of the bore 88. When the upper trocar component 84, which is a movable component, is moved to the fully open position illustrated in Figure 14, the inside arcuate face 92 of that component forms a continuation of a part of the bore 88 diametrically opposite to that formed by the surface 90 on the lower trocar component 82.

An operating lever 94 takes the form of a bell cranked lever pivoted at 96 on part of the body 80, one arm of the operating lever 94 extending below the handle 80, and the other arm of the lever 94 being bifurcated, and extending on opposite sides of the block 86, and being connected to that block by a pivot 98. Another lever 100 has a pressure pad 102 at one end, and is pivoted at 104 on part of the body 80. This lever 100 is also bifurcated, and extends on opposite sides of the block 86, to which it is connected by a pivot 106. The distance between the pivots 104 and 106 is equal to the distance between the pivots 96 and 98, so that the bifurcated portions of the two levers 94 and 100 provide a parallel linkage motion between the lower trocar component 82, and the upper trocar component 84.

When the appliance is to be used, the trocar components are collapsed one upon the other, and when the user grips the handle 80, he applies thumb pressure on the pad 102.

This pressure is transmitted through the lever 100, to the block 86, and holds the movable upper trocar component 84 tightly on to the lower stationary trocar component 82. In this way, the two trocar components are held firmly in the closed position during insertion of the trocar through the skin of a patient.

Once the trocar has penetrated the skin, thumb pressure on the lever 100 is released, and the lever 94 is gripped in the fingers of the hand holding the handle 80, and the lever 94 squeezed towards the handle 80. This has the effect of operating the parallel motion linkage, to open the trocar components 82 and 84 away from each other by a parallel motion.

As in the construction shown in Figures 1 to 10, the trocar components are parallel sided in the closed condition and due to the parallel motion of the movable component 84, they remain parallel sided in the fully open condition. Hence, the trocar can be removed from the incision around the drain tube without tearing the skin.

It is unnecessary to describe the operation of the appliance shown in Figures 11 to 14 in great detail, since it is used in a similar manner to the appliance illustrated in Figures 1 to 10. It will be appreciated however, that in some ways, the construction illustrated in Figures 11 to 14 is simpler to manufacture and operate than that illustrated in Figures 1 to 10.

In ei#ther of the constructions described above, the trocar components could be tapered towards the distal end to assist in insertion. Due to the parallel motion of the movable component this will result in the components being tapered towards the distal end even in the open condition and this will assist in withdrawal of trocar. It should be understood however that the motion between the closed and open conditions need not be parallel so long as the components remain parallel sided or tapered towards the distal end in the open condition to allow removal of the trocar from the patient without tearing the skin. In fact, by changing the distances between the pivots 96 and 98, or 104 and 106, the mechanism ceases to be a parallel motion mechanism, and the components 82 and 84 can be angled towards each other during the opening movement.

The distal ends of the trocar components 14 and 16 or 82 and 84 could be flattened so that in the closed condition they lie on top of the other and there is no channel, such as that shown in Figure 2, between them. This further facilitates entry of the trocar through the skin of the patient.

Claims (21)

1. A surgical appliance for forming an opening through the skin of a patient or animal comprising a trocar having a distal end intended to penetrate the skin; the trocar comprising at least two component parts or portions adapted to move relatively to each other between a closed condition and an open condition, and in which, when the trocar components are in the open condition, there is no substantial increase in the cross-section of the trocar towards the distal end, a lever mechanism being connected to the trocar component parts or portions for producing the movement from the closed to the open condition.

2. A surgical appliance as claimed in Claim 1, in which the arrangement is such that the trocar does not increase in cross-section towards its distal end at any position from its closed to open condition.

3. A surgical appliance as claimed in Claim 1 or Claim 2, in which the trocar tapers towards its distal end in the closed condition.

4. A surgical appliance as clained in Clain 3, in which the trocar tapers towards its distal end in the open condition.

5. A surgical appliance as claimed in Claim 3, in which the trocar is substantially parallel sided in the open condition.

6. A surgical appliance as claimed in any one of Claims 1 to 5, in which the arrangement is such that there is a channel through the trocar components when they are in the open condition.

7. A surgical appliance as claimed in Claim 6, in which the lever mechanism is so arranged that there is a central opening through it which, when the trocar components are opened, is in continuation of the central chan nel through those components, whereby it is possible to pass a tube through the entire appliance when the trocar components are open.

8. A surgical appliance as claimed in any one of Claims 1 to 7, in which the lever mechanism is adapted to hold the trocar components substantially parallel with each other throughout the opening movement.

9. A surgical appliance as claimed in any one of Claims 1 to 8, in which there are two trocar components and the lever mechanism is adapted to produce movement of one of these components relatively to the other.

10. A surgical appliance as claimed in any one of Claims 1 to 9, in which each trocar component has a blade like configuration, the blades being bowed outwardly as seen in lateral cross-section, so that in their closed position, the components contact each other only along the longitudinal edges, and in the open position, they approximate in cross-section to parts of an annulus, the internal diameter of which is large enough for the passage of a drain tube.

11. A surgical appliance as claimed in any one of Claims 1 to 10, in which the trocar components are detachable so that they can be replaced if required.

12. A surgical appliance as claimed in any one of Claims 1 to 11, in which the distal extemities of the trocar conponents are sharpened and formed with a cutting edge or edges which extend across substantially the full width of the trocar.

13. A surgical appliance as claimed in any one of Claims 1 to 12, comprising; a body to which a handle is attach; a stationary trocar conponent attached to the body; a moveable trocar component having a block slideable in a radial slot in the body; a lever pivoted on the body, and a mechanical connection between the lever and the block for converting the turning motion of the lever into radial motion of the block.

14. A surgical appliance as claimed in Claim 13, in which the mechanical connection comprises a pin-and-slot arrangement.

15. A surgical appliance as claimed in any one of Claims 1 to 14, in which there is provided a latching device adapted to hold the trocar components in the fully open and/or fully closed position.

16. A surgical appliance as claimed in any one of Claims 1 to 12, in which there is a stationary trocar component and a moveable trocar component connected by a pair of links forming a parrallelogram arrangement.

17. A surgical appliance as claimed in Claim 16, in which a hand-grip is connected to one of the links for the purpose of moving the trocar components apart.

18. A surgical appliance as claimed in Claim 16 or Claim 17, in which a pressure pad is connected to one of the links for the purpose of applying pressure to close the trocar components one on the other.

19. A surgical appliance as claimed in any one of Claims 16 to 18, in which a hand-grip extends from one of the links and can be gripped by the user in the same hand as the appliance handle to provide a gripping arrangement for opening the trocar components and a thumb pressure pad extends from the other link so that thumb pressure on it closes the trocar components.

20. A surgical appliance for forming an opening through the skin of a patient or animal constructed and arranged substantially as herein described with reference to Figures 1 to 10 of the accompanying drawings.

21. A surgical appliance for forming an opening through the skin of a patient or animal constructed and arranged substantially as herein described with reference to Figures 11 to 14 of the accompanying drawings.