referring firstly to fig1 to 4 of the drawings , an instrument ( 1 ) in accordance with a first embodiment of the invention comprises a straight hollow tubular shaft ( 2 ) of circular cross - section , made of any suitably sturdy electrically insulated or insulating material . the shaft is not drawn to scale but in reality would have an exemplary diameter of about 5 mm and a length of about 120 mm . the shaft has a distal end portion ( 3 ) of a material that can withstand the high temperatures experienced during excision . the distal end portion tapers at its end to terminate at the distal end in a point defining a narrow central hole ( 4 ) whose purpose will be explained . otherwise , the walls of the shaft are generally parallel and symmetrical about a central longitudinal axis of the shaft . an electrode ( 5 ) fits snugly within the proximal end ( 6 ) of the tubular shaft . the exposed outer or proximal end of the electrode ( 5 ) can be conductively connected to a blend cutting diathermy machine of known type , for example as is used with the fischer cone . an annular carriage ( 7 ) is slidable longitudinally in stepless manner along the outside of the shaft ( 2 ). a locking means ( 8 ) locks the carriage ( 7 ) to the shaft ( 2 ) in a desired longitudinal position , using a mechanism that will be explained below with reference to fig4 . graduations ( 9 ) marked externally on the distal portion of the shaft ( 3 ), in the example shown at 10 mm intervals from the distal end , allow the user readily to gauge the longitudinal position of the carriage ( 7 ) with respect to the distal end . the carriage ( 7 ) supports two mutually - opposed arms ( 10 ) that extend laterally about the shaft ( 2 ) in a diametrically - opposed , 180 °- spaced arrangement when viewed from an end of the shaft ( 2 ). each arm ( 10 ) has an inner portion ( 11 ) extending distally from the carriage ( 7 ) a short distance , for example 10 mm , substantially parallel to the longitudinal axis of the shaft ( 2 ). the inner portions ( 11 ) are spaced from the shaft to define a recess ( 12 ) around the shaft ( 2 ), whose purpose will be explained , the recess ( 12 ) being , for example , about 10 mm wide . each arm ( 10 ) also has an outer portion ( 13 ) extending orthogonally outwardly with respect to the longitudinal axis from the distal end of the inner portion ( 11 ), the outer portion ( 13 ) terminating in a free end ( 14 ). the outer portions ( 13 ) of the arms ( 10 ) appear straight in the side view of fig1 but as will be clear from the sectional view of fig2 the outer portions ( 13 ) are oppositely curved in end or plan view . the curvature is opposed in the sense that one outer portion ( 13 a ) is curved to one side of a line joining the free ends ( 14 ) of the outer portions ( 13 ) and extending through inner portions of the arms ( 11 ) and the central longitudinal axis of the shaft ( 2 ), and the other outer portion ( 13 b ) is curved to the other side of that line . the curvature of the outer portions of the arms ( 13 ) is semi - circular in the illustration , but may be varied at will . in this respect , it will be noted that the cross - section of each outer portion ( 13 ) is somewhat flattened so that the thickness of the outer portions ( 13 ) is greater when viewed from the side than it is in plan or end view . this facilitates a useful optional feature of the invention , which is that the outer portions of the arms ( 13 ) can be bent in plan or end view to vary and set their length . the curvature of the outer portions ( 13 ) is variable from straighter , to lengthen the arms ( 10 ), to more acutely curved , to shorten the arms ( 10 ). for example , the outer portions ( 13 ) may each be 30 mm long around the curve , meaning that the maximum length of each arm ( 10 ), when the outer portion is straightened , is 30 mm from the distal end of the inner portion ( 11 ). a typical length when the arm ( 10 ) is curved would be say 20 mm , within a possible range of perhaps 5 mm to 30 mm . to enable this feature , the outer portions of the arms ( 13 ) are made of a plastically - deformable and preferably manually - bendable material such as thick insulated wire that will not be fatigued by repeated bending and that can retain its set during the loading of normal use . the inner portions of the arms ( 11 ) are made of a relatively rigid insulated wire that will not bend as the outer portions are bent . first and second wires ( 15 a , 15 b ) are conductively connected at spaced locations to the distal or inner end of the electrode ( 5 ) and extend distally from the electrode within the hollow shaft ( 2 ), lying beside each other and extending to the tapered distal end ( 3 ). the wires ( 15 ) taper towards each other as they approach the distal end ( 3 ), being supported at the distal end by the rim of the hole ( 4 ) whose diameter is smaller than the spacing between the wires ( 15 ) where they are connected to the electrode ( 5 ). the wires ( 15 ) exit the shaft ( 2 ) through the hole ( 4 ) at the distal end ( 3 ), from where the wires ( 15 ) then sweep back oppositely , proximally and outwardly , defining straight cutting portions ( 16 ) that are inclined relative to the longitudinal axis of the shaft ( 2 ). each cutting portion ( 16 ) extends to , and is anchored at , the free end ( 14 ) of the outer portion of a respective arm ( 13 ). the cutting portions ( 16 ) are therefore coplanar with each other and with the distal end of the shaft ( 3 ) and define a generally triangular cutting head ( 26 ) about the shaft ( 2 ). within the shaft ( 2 ), the first and second wires ( 15 ) comprise respective proximal wire portions ( 17 ) and distal wire portions ( 18 ) joined by respective coil springs ( 19 ). the springs ( 19 ) act in tension at all times to keep the wires ( 15 ) and hence the cutting portions ( 16 ) taut and straight however the arms ( 10 ) may be adjusted . when adjustment of the arms ( 10 ) makes the cutting portions ( 16 ) shorter , the excess wire ( 15 ) is retracted into the shaft ( 2 ) by the tension of the springs ( 19 ). by shortening under their own tension , the springs ( 19 ) also store the excess wire ( 15 ) within the shaft ( 2 ). conversely , when adjustment of the arms ( 10 ) makes the cutting portions ( 16 ) longer , the springs ( 19 ) lengthen to release or pay out stored wire ( 15 ) to the cutting portions ( 16 ). each of the proximal wire portions ( 17 ) is conductively connected at a proximal end to the electrode ( 5 ) and at a distal end to a respective spring ( 19 ). each of the distal wire portions ( 18 ) is conductively connected at a proximal end to a respective spring ( 19 ) and extends distally from there to the distal end of the shaft ( 3 ). the springs ( 19 ) conduct current from the electrode ( 5 ) to the distal wire portions ( 18 ) for supply to the cutting portions ( 16 ) in use and so , for the purposes of this description , the springs ( 19 ) can be taken to be part of the first and second wires ( 15 ). it will be noted that the spring of the first wire ( 19 a ) is located near the middle of the shaft ( 2 ) and hence distally with respect to the spring of the second wire ( 19 b ), which spring is located near the proximal end of the shaft ( 2 ). this longitudinally offset spring arrangement is advantageous because it allows the shaft ( 2 ) to accommodate two springs ( 19 ) whose aggregate diameter is potentially wider than the internal diameter of the shaft ( 2 ). the degree of offset between the springs ( 19 ) is such that each can extend to its maximum length , which is when the cutting portions ( 16 ) are at their longest , without interfering with the other spring ( 19 ) also at its maximum length . in the preferred embodiments illustrated , a centering means takes the form of a collar ( 20 ) made of any suitable material such as rubber , plastics or a combination thereof . the collar ( 20 ) fits snugly around the shaft ( 2 ), having a central longitudinal bore to match the outer diameter of the shaft and thus having a diameter of about 5 mm in the example shown . the collar ( 20 ) is about 10 mm in length in the example shown , and tapers from a proximal base about 10 mm wide to a distal tip that is barely wider than the shaft ( 2 ). the tapered frusto - conical surface of the collar ( 20 ) is shaped to fit snugly within the openings of patulous cervical canals of various diameters . it will be noted that the collar ( 20 ) is dimensioned to rest as illustrated in a parked position within the aforementioned recess ( 12 ) between the inner portions of the arms ( 11 ) and hence proximally behind the outer portions of the arms ( 13 ). there , the collar ( 20 ) will not interfere with insertion of the instrument ( 1 ) into a normal cervix or a tightly - closed , i . e . stenosed cervix up to a cutting depth at which the outer portions of the arms ( 13 ) bear against the ectocervix ( 21 ). in these instances , the shaft ( 2 ) is received snugly enough within the cervical canal ( 22 ) to center itself accurately . however , when required to aid centering within a patulous cervix , the collar ( 20 ) is advanced towards the distal end of the shaft ( 3 ), moving out of the parked position and into a cervix - engaging position distally in front of the outer portions of the arms ( 13 ). in that position , the collar ( 20 ) will engage snugly within the opening of the cervical canal ( 22 ) when the cutting portions ( 16 ) reach their cutting depth in use and the outer portions of the arms ( 13 ) bear against the ectocervix ( 21 ), ready for the instrument ( 1 ) to be pivoted in an excision movement . in the embodiment shown , the fit between collar ( 20 ) and shaft ( 2 ) is such that the collar ( 20 ) can be moved comfortably by the user &# 39 ; s fingers along the shaft ( 2 ) but without being loose , the preferred resilience of the collar ( 20 ) gripping the shaft ( 2 ) in any position to prevent slippage of the collar ( 20 ) under the normal longitudinal loads of use . other arrangements are possible , as will be explained at the end of this description . the aforementioned graduations ( 9 ) marked on the distal portion of the shaft ( 3 ) have the primary purpose of aiding setting of the longitudinal position of the arms ( 10 ), but it will be noted that the graduations ( 9 ) also allow the user readily to gauge the longitudinal position of the collar ( 20 ) with respect to the distal end of the shaft ( 3 ). returning now to the locking means ( 8 ), this could be made of any suitable shape and of any suitable material , and can employ any of a variety of mechanisms . a simple and therefore preferred locking arrangement is illustrated and comprises a circular - section tubular housing ( 23 ) that supports the arms ( 10 ) and therefore doubles as the main structural part of the carriage ( 7 ). as best shown in the sectional view of fig4 the central axis of the housing ( 23 ) is oriented orthogonally with respect to the longitudinal axis of the shaft ( 2 ). the housing ( 23 ) has a blind end , an open end and aligned holes penetrating its cylindrical wall to admit the shaft ( 2 ) as a sliding fit in said orthogonal orientation . the housing ( 23 ) further contains a plunger ( 24 ) in the form of a short snug - fitting piece of round bar aligned with the central axis of the housing ( 23 ). the plunger ( 24 ) is penetrated by a transverse bore that is orthogonal to the central axis of the housing ( 23 ) and can be aligned with the holes in the housing , the bore similarly receiving the shaft ( 2 ) as a sliding fit when so aligned . the outer end of the plunger ( 24 ) extends slightly outside the housing ( 23 ). a coil spring ( 25 ) within the housing ( 23 ) acts in compression between the blind end of the housing and the inner end of the plunger ( 24 ), biasing the bore in the plunger ( 24 ) out of alignment with the holes in the housing ( 23 ) and so applying friction to the shaft ( 2 ) where the housing ( 23 ) and the plunger ( 24 ) are in contact with the shaft ( 2 ). this friction locks the housing ( 23 ) with respect to the shaft ( 2 ), to the extent that longitudinal or angular movement of the arms ( 10 ) with respect to the shaft ( 2 ) is prevented under the normal loading of use . however , when it is desired to move the arms ( 10 ) longitudinally during adjustment of the instrument ( 1 ) before use , it will be noted that the outer end of the plunger ( 24 ) presents a button surface that can be depressed against the biasing force of the spring ( 25 ) to align the bore of the plunger ( 24 ) with the holes of the housing ( 23 ) and thus to release the housing ( 23 ) for easy sliding movement along the shaft ( 2 ). freeing the mechanism in this way is a simple and wholly intuitive movement for the user wishing to move the carriage ( 7 ). the shape of the triangular cutting head ( 26 ) and the extent to which the instrument ( 1 ) is turned in use about the longitudinal axis of the shaft ( 2 ) defines the shape and extent of the cervical excision . the shape of the triangle ( 26 ) is determined by the longitudinal position of the carriage ( 7 ) and hence of the arms ( 10 ) with respect to the distal end ( 3 ), and also by the shape and hence the length of the arms ( 10 ) themselves . for example , moving the carriage ( 7 ) proximally along the shaft ( 2 ) will make the excision biopsy longer and deeper . in another mode of adjustment , straightening or increasing the curvature of the outer portions of the arms ( 13 ) will respectively widen or narrow the base of the excision biopsy . such manoeuvres allow excision biopsies to be taken from even the most distorted cervices . fig5 and 7 are intended to illustrate how the instrument of fig1 to 4 might be adjusted in use and the illustrative situation contemplated therein is deliberately unusual but not impossible . in this situation , the cervix ( 22 ) shown in fig7 is patulous to the extent that the endocervical opening is wider than the distal end portion ( 3 ) of the instrument ( 1 ), and the cervix ( 22 ) bears a heavily asymmetric lesion ( 27 ) requiring a wider cut to one side of the cervical canal ( 22 ) and a narrower cut to the other side . nevertheless , the lesion ( 27 ) does not extend far into cervical canal ( 22 ) and so a relatively shallow cut is called for . with this difficult cervical configuration in mind , the physician has adjusted the instrument ( 1 ) as best shown in fig5 and 6 . firstly , it will be noted that one arm ( 10 a ) has been extended and the other arm ( 10 b ) has been shortened to reflect the asymmetry of the lesion ( 27 ). the carriage ( 7 ) has been set closer to the distal end ( 3 ) to take a shallower cut , and the centering collar ( 20 ) has been advanced into a cervix - engaging position intermediate its parked position and the distal end of the shaft ( 3 ). fig7 shows the interaction of the instrument ( 1 ) as adjusted in fig5 and 6 with the cervix ( 22 ) that the adjustment was intended to suit . the instrument ( 1 ) shown in fig7 has been connected to an electrosurgical generator ( not shown ) and has been inserted into the cervix ( 22 ) through the vaginal canal , the vaginal canal being held open by a suitable speculum ( not shown ). the angular orientation of the instrument ( 1 ) about the longitudinal axis of the shaft ( 2 ) has been selected and controlled by the physician to bring the appropriate cutting portion ( 16 ) ( i . e . that supported by the extended arm ) into position to cut the lesion ( 27 ). the instrument ( 1 ) is shown in fig7 before being turned through 180 ° about its longitudinal axis to excise the lesion ( 27 ), but after the distal end portion ( 3 ) has been inserted into the cervical canal ( 22 ) and the arms ( 10 ) have contacted the ectocervix ( 21 ). the arms ( 10 ) thus prevent deeper insertion and signal to the physician by feel that the correct depth of insertion has been achieved . it is to be noted that the cutting portions ( 16 ) were energised since first contact with the endocervix ( 28 ) and so , in fig7 they have already cut through the ectocervix ( 21 ) the cutting depth predetermined by the adjusted disposition of the cutting portions ( 16 ). it will be evident from fig7 that the collar ( 20 ) has done its job by filling the patulous cervical canal ( 22 ) and so providing a reliable pivot point about which the instrument ( 1 ) can be turned during the forthcoming cutting operation . both cutting portions ( 16 ) have gone in deeply enough to excise all of the cin tissue that forms the lesion ( 27 ), but the cutting portion ( 16 a ) supported by the longer arm ( 10 a ) will produce a cut of greater radius during the cutting operation than will be cut by the other cutting portion ( 16 b ). in this way , all of the asymmetric lesion ( 27 ) will be removed but minimal damage will be caused to relatively unaffected areas of the cervix ( 22 ). referring now to fig8 the second embodiment illustrated therein is similar in principle to the first embodiment . to that extent , like numerals are used for like parts and the drawing is abbreviated to show only the internal features of the tubular shaft ( 2 ) that are different to the first embodiment . it will be seen that the shaft is divided by a central longitudinal partition ( 29 ) into two compartments that extend beside each other from the electrode ( 5 ) at the proximal end ( 6 ) all the way to the distal end ( 3 ). however , it would be possible for the partition ( 29 ) to be shortened , interrupted or dispensed with . otherwise , the distal portion of the shaft ( 3 ) is very much narrower than the proximal portion ( 6 ), being just wide enough internally to allow the first and second wires ( 15 ) to pass through to the distal end ( 3 ) within their respective compartments . the proximal portion ( 6 ) is much wider to allow free movement of springs ( 19 ) disposed beside each other in their respective compartments , effectively in parallel to one another . the springs ( 19 ) are anchored at their proximal ends directly to the distal end of the electrode ( 5 ). another spring arrangement for the second embodiment is shown in fig9 . instead of having two springs ( 19 ), one in each compartment , there is just one spring ( 19 ) that serves both compartments . the spring ( 19 ) is conductively connected to the electrode ( 5 ) at its mid point ( 30 ), and its ends are conductively connected to the respective wires ( 15 a , 15 b ). to enable this , the ends of the spring ( 19 ) extend into the respective compartments through an opening in the proximal end of the partition ( 29 ). an optional addition to either embodiment is illustrated in fig1 in relation to the first embodiment . this addition is a ruler ( 31 ) providing graduations ( 9 ) to assist in setting the length of the arms ( 10 ). in the illustrated embodiment , the ruler ( 31 ) is a flat narrow strip about 30 mm long , one end of which is pivotally attached to the carriage ( 7 ) by a pin ( 32 ) extending through the ruler ( 31 ) and into the blind end of the housing ( 23 ) of the locking means ( 8 ). when not in use , the ruler ( 31 ) lies against and parallel to the shaft ( 2 ) with the free end of the ruler pointing proximally . when moved angularly in either direction around its pivot ( 32 ), the ruler ( 31 ) can be oriented in parallel with the outer portions of the arms ( 13 ) to allow direct and exact measurement of the cutting radius of each arm ( 10 ). it is also possible that the arms ( 10 ) themselves could be graduated to give the desired radius . another locking means explained now by way of example is illustrated in fig1 . the locking means ( 8 ) therein comprises a c - section part - cylindrical sleeve ( 33 ) that partially surrounds the shaft ( not shown ), leaving a longitudinal slit ( 34 ) defined between parallel outwardly - extending oblong flaps that in use are parallel to the longitudinal axis of the shaft . each flap ( 35 ) contains an offset hole ( 36 ) near one end and terminates in a triangular radially - extending wing ( 36 ) at the other end , the wings of the respective flaps ( 36 ) facing away from each other . an edge of each wing ( 36 ) defines a ramp ( 37 ) that tapers towards the flap ( 35 ) moving away from the sleeve ( 33 ). a clip ( 38 ) in the form of a generally oblong piece of strong spring wire is pivotally received at one end by the holes ( 36 ) so that its long sides can engage the ramps ( 37 ) of the opposed wings ( 36 ). when the free end of the clip ( 39 ) is pressed towards the sleeve ( 33 ) in use , the long sides of the clip ( 40 ) move up the ramps ( 37 ), pressing the triangular wings ( 36 ) towards each other and thus tightening the sleeve ( 33 ) about the shaft ( 2 ). the sleeve ( 33 ) is tightened until the long sides ( 40 ) engage with respective notches ( 41 ) at the end of the ramps ( 37 ) to secure the clip ( 38 ) with the sleeve ( 33 ) locked to the shaft ( 2 ). to release the grip , the clip ( 38 ) is pulled in a reverse direction to disengage from the notches ( 41 ). as before , this locking means ( 8 ) is preferably integral with or synonymous with the carriage ( 7 ). for example , the arms ( 10 ) may be attached directly to the sleeve ( 33 ) in a manner analogous to the direct attachment of the arms ( 10 ) to the housing ( 23 ) in the first embodiment . many variations are possible without departing from the inventive concept . for example , it is possible for the or each spring ( 19 ) to be formed integrally with the wires ( 15 ) inside the shaft ( 2 ), and it is not essential that the or each spring ( 19 ) is a coil spring . in an alternative arrangement for advancing the centering collar ( 20 ) into a cervix - engaging position , the external surface of the distal portion of the shaft ( 3 ) and the bore of the collar ( 20 ) have complementary threads so that the collar ( 20 ) can be screwed along the shaft ( 20 ) simply by turning it about the shaft ( 2 ). the pitch of the thread can be selected so that the collar ( 20 ) will stay put under the normal conditions of use , once screwed into the desired cervix - engaging position . to recap , the excision instrument of the present invention has numerous advantages . it is simple and quick to use . the instrument described can take out any shape of cin of any depth up to 30 mm and any diameter up to more than 60 mm . excision biopsies could be taken even from the smallest cervices because the tapering distal end allows excision of cin to be taken even from stenosed ( narrowed ) cervical canals . the arms ( 10 ) can work independently of each other so that , for example , half the excised cin could be of 30 mm radius while the other half could be of 10 mm radius . this facility allows cin excision to be taken from completely distorted cervices , which are quite commonly encountered . in all cases , there is better exposure of the cervix , and blood loss is usually minimal . the collar ( 20 ) can be moved towards the distal end of the shaft ( 3 ) when used in patulous ( stretched open ) cervices , thus filling the cervical canal to control symmetrical cin excision . for all cervices , the need to rotate the instrument through only 180 ° makes excision simple , and the ability to pre - set the height and the base of the triangular cutting head ( 26 ) produces a predictable mirror image of the piece of tissue that is to be excised . by use of the invention , cin excision could be taken under local anaesthesia as an outpatient procedure . indeed , the present invention is believed to realise the cheapest and most efficient universally applicable instrument for treating pre - cancerous conditions of the cervix . these advantages can be gained in other specific ways within the inventive concept , and many other variations are possible . accordingly , reference should be made to the appended claims and to other conceptual statements herein rather than to the foregoing specific description when defining the inventive concept . in particular , whilst the instrument of this invention has been described for the treatment of uterine cervical conditions , it is envisaged that aspects of the invention could be used with benefit in the investigation or treatment of other lesions and other conditions , whether external or internal .
a cervical biopsy instrument comprises a shaft defining a longitudinal axis and having a proximal end and a distal end ; an arm extending laterally from the shaft ; a cutting portion of cutting wire being supported at an outer end by the arm and being inclined relative to the longitudinal axis ; and means for adjusting and setting the inclination and / or length of the cutting portion . this enables a single instrument to deal effectively with differently - sized , shaped and positioned cervical lesions , while tailoring the profile of the excision to the lesion concerned . in the embodiments described , two opposed arms support two cutting portions , requiring 180 ° of angular movement during excision as opposed to the 360 ° movement of the prior art . the arms are mounted on a carriage for longitudinal adjustment , and can be bent individually to vary their length and hence the width of cut , which may be asymmetric . a centering means such as a collar is provided to ensure accurate centering within patulous cervical canals .