GB2465631A

GB2465631A - Arthroscope with depth gauge

Info

Publication number: GB2465631A
Application number: GB0821765A
Authority: GB
Inventors: Tim Mead; Grant Timothy Lewis Smetham; Mark Anthony Di Cioccio; Stuart Brian William Kay
Original assignee: ORTHOMIMETICS Ltd; Tigenix Ltd
Current assignee: ORTHOMIMETICS Ltd; Tigenix Ltd
Priority date: 2008-11-28
Filing date: 2008-11-28
Publication date: 2010-06-02
Also published as: GB0821765D0

Abstract

An instrument kit and method for preparing a defect site in a tissue of a patient, comprising: a cutting instrument 20 and a depth guide assembly 30 , the cutting instrument comprising a tubular body 50 and a cutting blade 80 , positioned at the distal end of the tubular body & the depth guide assembly comprising an elongate depth guide 30 adapted to fit within the bore of the tubular body in a sliding relationship; characterised in that the kit further comprises a depth gauge comprising an aperture (100 fig 4) positioned within the body of the cutting instrument and at least one depth marker positioned on the depth guide (45) , the aperture allowing visualisation of a depth guide positioned within the bore of the cutting instrument, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualisation of a depth marker through the aperture indicates the depth of insertion of the cutting instrument.

Description

Defect site preparation kit This invention relates to a surgical instrument kit for preparing a defect site in a tissue of a patient prior to implantation with an implant.

Surgical treatment of defects in bone, cartilage or osteochondral surfaces is optimally carried out using an arthroscope. Arthroscopy is advantageous over open procedures because the surgery is minimally invasive -thereby reducing trauma -and it has reduced potential for infection and post-operative complications. The procedure for implanting an implant typically involves sizing the defect site and then preparing it for implantation by inserting a tubular guide instrument to a desired depth and using a drill within the guide instrument to remove a circular plug of tissue. A correspondingly sized implant must then be manipulated into place using an appropriate delivery device. Placing an implant into a defect site is more difficult and technically demanding using arthroscopic techniques relative to an open procedure because the small incisions employed with arthroscopic procedures reduce physical access to the defect site. This reduced access can limit the ability of the surgeon to fully visualise the guide instrument when it is inserted into the defect site to act as a guide for the drill bit. It is highly desirable to ensure that the guide instrument is inserted accurately to a planned depth to remove an exact amount of tissue. It is equally desirable to ensure that the guide instrument is inserted perpendicular to the surface being treated, to ensure that the prepared defect site after drilling is circular, ensuring an optimal fit with the implant, thereby promoting healing and minimising post-operative complications. The inability to fully visualise the guide instrument can lead to the instrument being inserted to the wrong depth and/or at an angle off the perpendicular, resulting in a poorly-sized prepared defect site, and complicating the insertion of the implant and its fit within the prepared defect site.

It is an object of the present invention to provide a kit of instruments which addresses the above-stated problems.

According to a first aspect of the present invention there is provided an instrument kit for preparing a defect site in a tissue of a patient, the kit comprising: a cutting instrument and a depth guide assembly, the cutting instrument comprising a tubular body and a cutting blade, the body defining a distal end, a proximal end and a bore extending longitudinally there between; the cutting blade being positioned at the distal end of the body and being suitable for insertion into a defect site; the depth guide assembly comprising an elongate depth guide having a proximal and distal end and being adapted to fit within the bore in a sliding relationship; characterised in that the kit further comprises a depth gauge, the depth gauge comprising an aperture positioned within the body of the cutting instrument and at least one depth marker positioned on the depth guide, the aperture allowing visualisation of a depth guide positioned within the bore of the cutting instrument, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualisation of a depth marker through the aperture indicates the depth of insertion of the cutting instrument.

There is provided a cutting instrument, adapted for use with a depth guide assembly and a surgical drill bit, the cutting instrument comprising a tubular body and a cutting blade, the body defining a distal end, a proximal end and a bore extending longitudinally there between; the cutting blade being positioned at the distal end of the body and being suitable for insertion into a defect site; the depth guide assembly comprising an elongate depth guide being adapted to fit within the bore in a sliding relationship and having a proximal and distal end, and a depth marker positioned toward the distal end, characterised in that the cutting instrument comprises an aperture positioned within the body, the aperture allowing visualisation of a depth guide positioned within the bore, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualisation of a depth marker through the aperture indicates the depth of insertion of the cutting instrument.

The body of the cutting instrument may further comprise an at least one first alignment marker for alignment with the depth marker, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualised alignment of a depth marker with a first alignment marker indicates a required depth of insertion of the cutting instrument into a defect site.

The cutting instrument may comprise an at least one first alignment marker, and an at least one second alignment marker. The alignment markers may comprise two separate scales.

One scale of markers may be marked from the distal end of the cutting instrument, The second scale may be offset in a proximal direction from the first scale, and marked at or about the aperture. The calibration of the first scale of alignment markers preferably correlates with the calibration of the second scale of alignment markers. The first and second scales may be offset by the distance that the most distal depth marker is marked from the distal end of the depth guide. The first and second scales may be calibrated up to 8mm, or 16mm. The most distal depth marker may be marked at a distance of 2mm, 4mm, 6mm, or 8mm from the distal end of the depth guide. The offset distance may be 2mm, 4mm, 6mm, or 8mm.

The combination of the depth marker and the alignment markers may be used to judge perpendicularity of insertion. Visualised alignment of a depth marker with the equivalent alignment markers may indicate an angle of insertion of the cutting instrument and preferably perpendicular insertion of the cutting instrument.

The cutting instrument may further comprise an at least one second alignment marker, the first alignment marker being offset from the second alignment marker by the distance the most distal depth marker is marked from the distal end of the depth guide, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, a correlation between the depth of insertion judged using visualised alignment of a depth marker with a first alignment marker and the depth of insertion judged using a second alignment marker indicates a perpendicular angle of insertion of the cutting instrument into a defect site.

In the event that the cutting instrument is inserted in a non-perpendicular angle the depth of insertion read using the depth marker and the offset second scale will not correlate with the depth of insertion read using the first scale of alignment markers. For example, in the event that a user leans the instrument away from them by a small angle, the depth of insertion read using the second offset scale and depth marker visualised in the aperture will exceed the depth of insertion read using the first scale of alignment markers. In the event that the two readings do not correlate with each other, a user knows that the angle of insertion is off the perpendicular, and can correct the angle of insertion before inserting the cutting instrument to its required depth.

The alignment marker(s) may be comprised within the depth gauge.

The at least one first alignment marker may be located at the position of the aperture. The alignment marker(s) may circumferentially extend around the body of the cutting instrument.

The alignment marker(s) preferably are graduations circling the body, running in parallel to each other and/or the distal end of the cutting instrument. The alignment marker(s) may comprise numerical indicators of depth, which may range from 1-16, or 2-8 at 0.5mm, or 1mm, or 2mm intervals. One or more markers may be emphasised to indicate certain depths, for example 4mm and 8mm, These two insertion depths are considered to be important during the surgical procedure. 4mm, represents the approximate maximum depth that still allows correction of the alignment of the cutting instrument without causing significant hole error or trauma. At this depth of insertion of the cutting instrument, insertion can be paused temporarily although the cutting instrument is not removed from the defect site. A user can check the alignment of the instrument in the defect site and either confirm that perpendicularity has been achieved, or observe that the cutting instrument has been inserted off the perpendicular, and move the cutting instrument to a perpendicular angle. The insertion of the instrument then continues, either maintaining the previous alignment, or where the alignment was off the perpendicular, using the corrected alignment. The cutting instrument can then be inserted to a desired depth -typically 8mm -which represents a depth of insertion that allows sufficient penetration into the bone to ensure a good blood supply.

As discussed previously, it is an object of the present invention to assist a user in maintaining perpendicularity when inserting the cutting instrument into a defect site. The instrument kit enables a user to assess the angle of insertion (i.e. if perpendicularity has been achieved) in two separate ways.

In the first way, the combination of the depth marker(s) and the alignment marker(s) may enable a user to assess the angle of insertion of the cutting instrument.

In the second way, the alignment markers can be used to assess the angle of insertion.

Where the alignment marker(s) extend at least partially circumferentially around the body, a non-perpendicular insertion of the cutting instrument may result in a portion of the most-distal visible marker disappearing below the surface of the tissue, with another portion being visible above the surface in a non-parallel orientation. A user can maintain perpendicularity of the cutting instrument by carefully monitoring the most distal or distal alignment markers as the cutting instrument is inserted into a defect site. Should a portion of one alignment marker move off the parallel relative to the surface of the tissue (indicating a loss of perpendicularity), corrective action can be taken by a user to move the cutting instrument back to a perpendicular position. The instrument can then be inserted to the require depth.

The alignment marker(s) may be used in combination with a depth marker(s) on the depth guide, thereby indicating the depth and/or angle of insertion of the cutting instrument into a defect site. The alignment marker(s) may be also be used used on their own to indicate the depth and/orangle of insertion of the cutting instrument as it is inserted to the required depth.

The kit thus comprises several ways to monitor perpendicularity and depth of insertion.

The depth marker(s) may be graduations, which may circumferentially extend around the depth guide at regular intervals marked from the distal end of the depth guide. One or more of the depth markers may be emphasised to indicate certain depths. For example, with an instrument kit designed for insertion and removal of 8mm depth of tissue within a defect, the alignment marker(s) and depth marker(s) may emphasise the 8mm depth, and optionally other depths, such as every 0.5mm, every 1mm, every 2mm, or every 4mm. The cutting instrument may be adapted to be inserted to a maximum depth of 6mm, 8mm, 10mm, 12mm, 14mm, or 16mm. The alignment marker(s) and/or depth marker(s) may be configured to mark any depth of insertion between 0.5 and 16mm.

The depth guide may comprise one depth marker marked at a known distance from the distal end. The depth marker may be marked at 4mm from the distal end of the depth guide.

The graduations may comprise continuous or discontinuous lines, dots, markings or other visual indicators.

The aperture may be positioned at or toward the distal end of the cutting instrument. The aperture may be positioned in the distal half, third, or quarter of the cutting instrument. The aperture may open into the distal end of the cutting instrument, or may be discrete within the body. The aperture may be open, allowing access to the bore, or sealed with a transparent material to enable visualisation of a depth guide positioned within the bore. The aperture may be a slot longitudinally extending along the body and/or extending circumferentially around the body. The body may comprise more than one aperture. The apertures may be spaced radially at regular intervals around the body, and/or spaced longitudinally.

The diameter of the bore of the cutting instrument may be larger at its proximal end. The bore of the cutting instrument may define a first bore diameter (bi) at its distal end and a second bore diameter (b2) at its proximal end, the second bore diameter being larger than the first bore diameter. The transition between the first and second bore diameters may be abrupt, defining a step, or it may be gradual, defining an inverted frustro-conical region, adapted to fir with an equivalent region on an anvil. The region of increased bore diameter is preferably adapted to house an anvil.

The depth guide assembly may be removably attachable or engageable with the cutting instrument. The depth guide assembly may comprise an anvil, the anvil being attachable or engageable to the cutting instrument and being adapted to transmit a striking force imposed thereon to the cutting blade.

The anvil is preferably adapted to fit within the bore of the cutting instrument, the anvil comprising a wall defining inner and outer surfaces, and having distal and proximal ends, with an anvil bore extending there between. The anvil is preferably adapted to fit within the bore at the proximal end of the cutting instrument, whereby, in use, with an anvil positioned within the bore, the bore of the cutting instrument and the anvil bore are coincident with each other. The diameter of the anvil bore may be substantially the same as the second bore diameter of the cutting instrument. The thickness of the anvil wall may be equal to the distance by which the second bore diameter exceeds the first bore diameter. Preferably the anvil bore provides a continuation of the cutting instrument bore by being coincident with and having the same diameter as the first bore diameter (bi).

The proximal end of the anvil may extend beyond the proximal end of the cutting instrument.

The anvil preferably comprises a flattened proximal end section, which may be adapted to be struck with a surgical hammer to transfer the forces applied to it to the cutting blade, thereby enabling a user to insert the cutting instrument into the defect site. The anvil, or at least a portion of it, and/or the proximal end section, may be manufactured from stainless steel or otherwise resilient material capable of withstanding the forces required to drive the cutting instrument into the defect site. The stainless steel is preferably surgical grade stainless steel.

The depth gauge may comprise a second indicator of depth of insertion. The length of the depth guide may be adapted to indicate the required depth of insertion, whereby the combined length of the bore of the cutting instrument and the anvil bore exceeds the length of the depth guide by the required depth of insertion, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, alignment of the proximal end of the depth guide with the proximal end of the anvil indicates the required depth of insertion of the cutting instrument into the defect site. Alignment of the proximal end of the anvil and depth guide may be useful when the distal end of the device is obscured during a surgical procedure.

The depth gauge may thus indicate the depth of insertion via an aperture/depth marker system, and a proximal ends alignment system.

The required depth of insertion of the cutting instrument, as indicated by the depth marker(s) and alignment marker(s) may be from about 0.5 to about 16mm or about 1 to about 8 mm.

This distal end of the depth guide may comprise a flat surface, or it may be profiled to fit with a curved or otherwise shaped surface, for example the curvature of the condyle of the femur.

The surface may be convex.

The cutting instrument is preferably sized for use in arthroscopic surgical procedures and may be between 120-155mm in length. The body may comprise stainless steel which may be surgical grade. The body may be coated or plated with a surgically compatible material.

The kit is designed to enable precise alignment of the cutting blade with the surface of a defect site and precise removal of tissue to a required depth. Depending on the nature and size of any defect, the required depth of insertion may differ, either at the same defect site, between defect sites within the same patient, or between different patients. To cater for different required depths of insertion, the kit may comprise two or more depth guides, each having a different length corresponding to a different required depth of insertion and/or the depth markers being positioned differently on each to indicate different required depths of insertion. The length of the depth guide may be adjustable, thereby allowing one depth guide to cover a range of depths of insertion.

The depth guides may further vary according to their diameter. The presence of multiple depth guides within the instrument kit enables a user to select the most appropriate for the defect site being prepared. The kit may comprise multiple anvils and cutting instruments, each being adapted to fit depth guides differing in their diameter or other characteristics. The depth guide or other instruments of the kit may be marked to indicate their working specification, for example by using colour coding, writing, or combinations of both.

The depth guide assembly may comprise means to effect protrusion of the depth guide from the distal end of the cutting instrument. The depth guide may comprise dual-functionality. In addition to indicating depth of insertion of the cutting instrument at both distal and proximal ends, the depth guide is preferably adapted to function as an obturator. The depth guide, when protruding from the distal end of the cutting instrument may shield and protect tissue from the cutting blade. The depth guide thus enables the cutting instrument to be advanced toward, and positioned at, a defect site without damaging the soft tissue. The means to effect protrusion may comprise a projection adapted to fit in the anvil bore, wherein the combined length of the projection and a depth guide exceeds the combined length of the bore of the cutting instrument and the anvil bore. The projection may be attached to a cap or covering member, being adapted to fit over the proximal end of the anvil. The cap or covering member, and/or the projection, may comprise means to lock or snap the projection into place within the anvil bore, thereby forcing the projection to effect protrusion of the distal end of the depth guide out of the distal end of the cutting instrument. The projection may be a barbed peg, which may be attached to a locking cap. In a preferred embodiment, a user is able to place a locking cap over the proximal end of the anvil, the projection extending into the anvil bore, forcing the distal end of the depth guide to protrude from the distal end of the cutting instrument. In this way, a user can concentrate on manoeuvring the cutting instrument into position with the depth guide acting as an obturator. Upon removal of the projection from within the anvil bore, for example by removing the locking cap, the depth guide is free to move proximally within the bore of the cutting instrument. The position of the depth guide within the bore of the cutting instrument when being forced to protrude from the cutting instrument may represent the maximum distal movement of the depth guide.

The depth guide assembly may comprise biasing means, adapted to resiliently bias a depth guide positioned within the bore toward a rest position. With a depth guide positioned within the bore of the cutting instrument, the rest position of the biasing means may result in the distal end of the depth guide lying flush with the distal end of the cutting instrument.

Depending on the position of the depth guide within the bore, the biasing means may exert bias in both distal and proximal directions. The biasing means may comprise an elastic material or member, or a spring. The spring may be a tension/extension spring and/or a compression spring. The spring may be a helical spring. The spring preferably defines a rest position, where it is neither extended nor compressed. With a depth guide positioned within the bore of the cutting instrument this rest position may be when the distal end of the depth guide lies flush with the distal end of the cutting instrument, or alternatively when the distal end of the depth guide protrudes out of the distal end of the cutting instrument.

The cutting instrument and/or anvil may comprise means to anchor the biasing means. The inner surface of the anvil wall may comprise a neck region internally extending into the anvil bore to define a neck region bore. One end of the biasing means, for example a spring, may be mountable against the neck region, the other more distal end being adapted to engage with the depth guide. The depth guide may comprise a catch or other means to engage with the distal end of the biasing means. The depth guide may comprise a region having decreased diameter defining a shoulder for engagement with the biasing means. Where the biasing means is a helical spring, the region of decreased diameter preferably allows the spring to be positioned over the depth guide and not extend beyond the radial boundary defined by the portion of the depth guide having a non-decreased diameter. The spring may thus be positioned over the depth guide such that it does not interfere with the sliding movement of the depth guide within the bore of the cutting instrument. When the depth guide is forced to protrude from the distal end of the cutting instrument (i.e. is acting as an obturator), the spring may be extended beyond its rest position, thereby biasing the depth guide in a proximal direction back to the rest position, or the spring may be in its rest position, with no proximal bias being exerted on the depth guide. When the depth guide is being used to indicate depth of insertion of the cutting instrument, the proximal movement of the depth guide within the bore of the cutting instrument as the instrument is inserted into the defect site results in the spring being compressed. This compression force results in the depth guide being biased in the distal direction thereby ensuring that contact is maintained between the surface of the defect site and the distal end of the depth guide. This in turn ensures that any depth reading visualised through the aperture and/or by alignment of the proximal ends of the depth guide and the anvil, is accurate.

The diameter of the depth guide may be increased at its proximal end, the increased diameter exceeding the diameter of the neck region bore. The region of increased diameter essentially prevents (or renders more difficult) the passing of the proximal end of the depth guide through the narrower neck region bore. This prevents a depth guide positioned within the bore from egressing from the distal end of the cutting instrument when in use. The region of increased diameter does not prevent the assembly of a depth guide and an anvil, although it is preferred if an extra insertion/removal force is required to engage/disengage a depth guide with/from an anvil. The increased diameter may be effected through the use of an 0-ring or C-clip positioned at the proximal end of the depth guide. The depth guide may comprise a shoulder, collar, or other section suitable for mounting the 0-ring or C-clip.

The outer surface of the anvil wall may comprise means to reversibly engage with an inner surface of the wall of the cutting instrument. The means to engage may comprise one or more projections, or one or more regions having increased diameter. The means may comprise an attachable 0-ring circumferentially extending around the anvil. The 0-ring may be adapted to fir within a collar region, itself circumferentially extending around the anvil. The means are adapted to enable the depth guide assembly to be positioned and held in place within the bore of the cutting instrument, preferably with the distal end of the anvil contacting the step or other surface at the transition between the first and second bore diameters.

The instruments of the kit may be fully or partially assembled. The depth guide assembly may be fully or partially assembled. In preferred embodiments, the depth guide and other components (biasing means, projection, etc.) are assembled with the anvil, enabling a user to insert the pre-assembled depth guide assembly into the bore of the cutting instrument at its proximal end. The depth guide may be held in position within the anvil bore, with the biasing means in its rest position. The projection may be located in the anvil bore, and may be held in place with a cap or covering member positioned over the proximal end of the anvil.

Alternatively, where a number of depth guides are present within the kit of instruments, each may be partially assembled with its biasing means and 0-ring or C-clip. A user can select the required depth guide, which may vary according to its indications of depth or diameter, and insert the depth guide into an appropriately sized anvil, and then into an appropriately sized cutting instrument.

The assembled depth guide assembly may be positioned within the bore of the cutting instrument.

The cutting instrument preferably comprises a handle, the handle partially covering the body leaving at least the distal end exposed. The handle may be between 70-95 mm in length. The handle may comprise a surgically compatible material selected from the group consisting of: nylon, polytetrafluoroethylene (PTFE), acrylonitrile butadiene styrene (ABS), polycarbonate, polymethylmethacrylate, glass, carbon fibre, and latex.

The cutting blade may extend circumferentially around the distal end of the body. The cutting blade may comprise a continuous cutting edge, or a discontinuous cutting edge, for example serrations. The cutting blade may comprise a metallic material, for example stainless steel.

The kit may further comprise a surgical drill bit adapted to fit within the bore of the cutting instrument in a sliding relationship. The drill bit is preferably rotatable about its longitudinal axis. The length of the surgical drill bit may be the substantially the same as the length of the bore of the cutting instrument. The drill bit is preferably adapted to only remove tissue positioned within the bore of the cutting instrument when inserted into a defect site. The surgical drill bit may comprise a flange toward its proximal end to prevent the surgical drill bit from protruding through the distal end of the cutting instrument. The surgical drill bit may comprise means for attachment to, or an interlace with a rotation device. The drill bit may be adapted for manual or power assisted rotation.

The kit may comprise at least one selected from the group consisting of: a plurality of cutting instruments having various dimensions; a plurality of depth guide assemblies having various depth guide dimensions; a plurality of surgical drill bits having various drill bit dimensions.

According to a second aspect of the present invention, there is provided use of the kit according to a first aspect of the present invention to prepare a defect site in a patient.

According to a third aspect of the present invention, there is provided a method of preparing a defect site in a tissue of a patient, the method comprising: * providing access to a defect site through a surgical incision in the body of the patient; * with an instrument kit according to a first aspect of the present invention, effecting the protrusion of the distal end of the depth guide from the distal end of the cutting instrument, * advancing the cutting instrument toward the defect site, the protruding distal end of the depth guide shielding soft tissues from the cutting blade as the cutting instrument advances; * positioning the cutting instrument to touch a surface of the defect site, the depth guide moving proximally within the bore until the distal end of the depth guide lies flush with the distal end of the cutting instrument; * applying an insertion force to the cutting instrument to insert the cutting instrument into the defect site to the required depth, the depth guide moving proximally within the bore until a depth marker visible through the aperture indicates that the required depth of insertion has been obtained, and/or the proximal end of the depth marker lies flush with the proximal end of an anvil positioned within the bore of the cutting instrument; * removing the depth guide assembly from the bore of the cutting instrument; * inserting a surgical drill bit into the bore of the cutting instrument and drilling tissue within the bore of the cutting instrument.

The method may comprise achieving perpendicularity during the insertion step by ensuring that the depth of insertion as judged using visualised alignment of a depth marker with a first alignment marker is the same as the depth of insertion judged using a second alignment marker.

There is provided a method of preparing a defect site in a tissue of a patient, the method comprising: * providing access to a defect site through a surgical incision in the body of the patient; * with an instrument kit according to a first aspect of the present invention, effecting the protrusion of the distal end of the depth guide from the distal end of the cutting instrument, * advancing the cutting instrument toward the defect site, the protruding distal end of the depth guide shielding soft tissues from the cutting blade as the cutting instrument advances; * positioning the cutting instrument to touch a surface of the defect site, the depth guide moving proximally within the bore until the distal end of the depth guide lies flush with the distal end of the cutting instrument; * applying an insertion force to the cutting instrument to insert the cutting instrument into the defect site to the required depth, wherein perpendicularity is achieved by ensuring that the depth of insertion as judged using visualised alignment of a depth marker with a first alignment marker is the same as the depth of insertion judged using a second alignment marker; * removing the depth guide assembly from the bore of the cutting instrument; * inserting a surgical drill bit into the bore of the cutting instrument and drilling tissue within the bore of the cutting instrument, The method may initially comprise assessing a defect site to determine a required depth of insertion of the cutting instrument. The method may comprise assembling a depth guide assembly, and/or inserting same into the bore of a cutting instrument.

The drilling step may comprise drilling until the flange contacts the proximal end of the cutting instrument, thereby preventing further distal movement of the drill bit within the bore.

After drilling the tissue, the method may comprise removing the drill bit from the bore of the cutting instrument.

According to a fourth aspect of the present invention, there is provided a method of delivering an implant into a defect site in a tissue of a patient, the method comprising preparing the defect according to a third aspect of the present invention, and delivering an implant into the prepared defect site.

The tissue may be selected from the group consisting of: cartilage, bone, ligament, tendon, meniscus, periodontal tissue, dentine, enamel, intervertebral discs, annulus fibrosus, and nucleus pulposus.

The patient may be a mammal. The patient may be a non-human mammal such as a dog, camel, or horse. The patient may be selected from the group consisting of: human, dog, camel, and horse.

According to a fifth aspect of the present invention, there is provided a method of assembling a cutting tube and a depth guide assembly, comprising, with a cutting tube and depth guide assembly according to a first aspect of the present invention, inserting an assembled depth guide assembly into the proximal end of the cutting instrument.

The invention will now be described with reference to the following drawings, in which: Figure 1 is an exploded view of a defect site preparation kit according to the present invention; Figure 2 shows the assembled cutting instrument and depth guide assembly; Figures 3 shows the distal end of the cutting instrument with the depth guide positioned within the bore, the distal end of the depth guide protruding therefrom; Figure 4 shows the alignment markers of the cutting instrument; and Figures 5a-5f depict various stages in preparing a defect site using the kit of the present invention prior to implantation.

Referring initially to Figure 1 of the drawings, a defect site preparation kit (10) comprises a cutting instrument (20), a depth guide assembly (30), surgical drill bit (40) and depth gauge (45).

The cutting instrument (20) comprises a hollow tubular body (50) defining a distal end (60) and proximal end (70). A bore (72, see Figure 5) extends longitudinally from the distal end (60) to the proximal end (70). Distal end (60) of the instrument (20) comprises a circumferential cutting blade (80) suitable for insertion into a defect site. In the embodiment shown, the blade comprise a continuous cutting edge, although discontinuous edges (not shown) can be employed if required. The cutting instrument is between 120-155mm in length and sized for arthroscopic procedures.

Handle (90) surrounds the proximal end (70) of the body (50). The cutting instrument (20) further comprises an aperture (100) in the form of a vertically extending slot (100) located toward its distal end (60). The slot (100) allows for visualisation of other instruments positioned within the bore of the cutting instrument. Alignment markers (110), in the form of regularly spaced apart graduations (112) extend around the body, perpendicular to the longitudinal axis of the bore (72) and parallel to the cutting blade (80).

Depth guide assembly (30) comprises an elongate depth guide (120), anvil (150), biasing means in the form of a helical spring (160), cap assembly (170), anvil 0-ring (180) and C-clip (190).

Depth guide (120) defines a distal end (130) and a proximal end (140) and comprises a depth marker (144) located toward its distal end at a required depth of insertion, which is typically 4mm. Anvil (150) is adapted to fit within the bore (72) at the proximal end (70) of cutting instrument (20), the anvil (150) itself comprising an anvil wall (152) and defining an anvil bore (154) sized to align with the bore (72) of cutting instrument (20). The depth guide (120) is adapted to fit within bore (72) and anvil bore (154) in a sliding relationship. Depth guide (120) comprises shoulder (147) toward its proximal end (140) adapted to engage with biasing means (160). Collar (189) located at the proximal end (140) of the depth guide (120) is adapted to engage with C-clip (190). Cap assembly (170) comprises cap (174) and attached projection (178), adapted to fit over the proximal end of the anvil (150), with the projection extending into the anvil bore (154).

Surgical drill bit (40) is adapted to fit within the bore of the cutting instrument in a sliding relationship. The drill bit (40) comprises a drill tip (190) at its distal end and flange (200) at its proximal end. The drill bit is adapted to attach to rotation means, such as a surgical drill unit (not shown).

Depth gauge (45) comprises the aperture (100) within the body (50) of cutting instrument (20) and depth marker (144) on the depth guide (120).

The cutting instrument (20) and depth guide assembly (30) are shown assembled in Figure 2, where the distal end (130) of depth guide (120) protrudes from the distal end (60) of the cutting instrument (20) because cap assembly (170) is positioned in place in the anvil bore (154), the projection (not shown) contacting the proximal end of the depth guide and forcing the distal end to protrude out of the cutting instrument.

Referring now to Figures 3 and 4, depth guide (120), positioned within the bore of the cutting instrument (20), is visible through slot (100). The distal end (60) of the cutting instrument (20) further comprises a series of alignment markers (110), representing a first scale, marked at regular 1mm spaced intervals (112), each extending circumferentially around the body (50) and perpendicular to the longitudinal axis of the bore. The graduations (112) are comprised of alternating continuous and discontinuous lines marked to a distance of 8mm from the distal end of the cutting instrument (20). The alignment markers (110,112) serve to indicate the depth of insertion of the cutting instrument into a defect site, and can also be used to monitor perpendicularity. The most proximal alignment markers extend around the body at the height of the slot (100). Beyond the alignment markers (110,112), the slot itself comprises separate alignment markers (114), representing a second scale, marked numerically, the most distal of which are aligned with the most proximal of alignment markers (110,112). The most proximal alignment markers (114) extend proximally beyond the last circumferentially extending graduation (110, 112). The most proximal alignment marker (114) is marked at 16mm from the distal end (60) of the cutting instrument (20). Depth marker (144) on the depth guide (120) is marked to align with alignment markers (110,122) and/or alignment markers (114) when the cutting instrument is inserted into a defect site to a desired depth. The second scale of alignment markers (114) are offset from the first scale of alignment markers (110, 112) by the same distance that depth marker (144) is marked from the distal end of the depth guide. In the embodiment shown, depth marker (144) is marked at 4mm from the distal end of the depth guide. When the cutting instrument is in contact with a defect site, with the distal end of the depth guide lying flush with the distal end of the cutting instrument (not shown), depth marker (144) aligns with the alignment marker on the second scale (114) which reads zero.

As the instrument is inserted, the depth guide slides proximally in the bore, with depth marker (144) indicating the depth of insertion. Thus, if the instrument is inserted to a depth of 4mm, this can be judged using the first scale of alignment markers (110, 112) and the second scale of alignment markers (114). The combination of the depth marker and the alignment markers can also be used to judge perpendicularity. In the event that the cutting instrument is inserted in a non-perpendicular angle -a common problem encountered due to the restricted view offered during arthroscopic procedures -the depth of insertion read using the depth marker and the second scale of alignment markers will not correlate with the depth of insertion read using the first scale of alignment markers. For example, in the event that a user leans the instrument away from them by a small angle, the depth of insertion read using the depth marker and the second scale will exceed the depth of insertion read using the first scale of alignment markers alone. In the event that the two readings do not correlate with each other, a user knows that the angle of insertion is off the perpendicular, and can correct the angle of insertion before inserting the cutting instrument to its required depth. Where the depth of insertion read using the depth marker and the second scale is the same as the depth of insertion read using the first scale of alignment markers alone, a user knows that the cutting instrument has been inserted at the required perpendicular angle.

Referring generally to Figure 5 of the drawings, anvil (150), when positioned within the bore (72) of the cutting instrument (20) rests on step (75), which represents the transition from a first bore diameter (bi) to a second, wider, bore diameter (b2) (shown clearly in Figure Sd).

The anvil (150), when positioned within the bore (72) of cutting instrument (20) protrudes out of the proximal end (70). Anvil 0-ring (180) sits in anvil collar (157) which extends circumferentially around the outer surface of the anvil, the 0-ring (180) providing a friction fit between the outer surface of the anvil (150) and the wall of the cutting instrument, minimising movement of the anvil (150) within the bore. The anvil (150) comprises neck region (158, shown in Figure Saii) inwardly extending into the anvil bore (154), defining neck region bore (ni). The neck region (158) is adapted to prevent (or render more difficult) the passing of the widened proximal end of the depth guide (120). In the embodiment shown, C-clip (190) is employed to increase the diameter of the depth guide beyond the distance ni. The neck region (158) is positioned to allow the depth guide (120) to protrude a few millimetres out of the distal end of the cutting instrument (20). The neck region (158) and C-clip (190) arrangement allows sliding movement of the depth guide (120) within the aligned bores (72, 154) but prevents the depth guide (120) from completely sliding out of the distal end of the instrument when in use. The depth guide assembly (30) is removable from the bore (72) of the cutting instrument (20) upon a user applying sufficient removal force to the anvil (150).

Similarly, if sufficient force is applied to the depth guide, the C-clip (190) can be forced through the neck region bore (160), allowing removal of the depth guide from the anvil. The force required to do this typically exceeds the forces placed upon the depth guide when in use during a surgical procedure.

In preferred embodiments the anvil (150) is made of a metal such as surgical grade stainless steel. The protruding end of anvil (150) is flattened and reinforced, providing a proximal end section (184) to which a force can be imparted, for example with a surgical hammer. The anvil (150) transfers forces applied to the cutting instrument (20), facilitating insertion of the distal end (60) of the cutting instrument into a defect site, such as bone, cartilage or an osteochondral surface, to a required depth.

Cap (174) comprises projection (178) adapted to fit within the anvil bore (154) and contact the proximal end of the depth guide (120). The length of the projection (178) is greater than the distance by which the combined length of bores (72, 154) exceed the length of the depth guide (120). Thus, cap assembly (170), when positioned within the anvil bore (154), forces the distal end (130) of depth guide (120) out of the distal end (60) of the cutting instrument (20), to a distance of a few millimetres. The depth guide (120) when protruding from the cutting instrument (20) in this way can act as an obturator, thereby allowing the cutting instrument (20) to be inserted percutaneously and advanced toward a defect site without the cutting blade (80) causing unwanted damage to soft tissues.

Biasing means (160) comprises a helical spring (160) adapted to be mounted on a shoulder region (188) positioned at the proximal end (140) of depth guide (120). When the depth guide is positioned within the anvil bore (154), the proximal end of the spring (160) is braced against the distal surface of neck region (158). The spring defines a rest position where no extension/compression forces are acting on it. The spring can be compressed and extended, thereby biasing the depth guide in proximal and distal directions. In one embodiment, the rest position is defined when the distal end of the depth guide lies substantially flush with the distal end of the cutting instrument (20). When the distal end of the depth guide protrudes from the distal end of the cutting instrument, the spring will be extended, thereby biasing the depth guide proximally, toward the rest position. Should the distal end of the depth guide lie proximal to the distal end of the cutting device the spring will be compressed, biasing the depth guide distally toward the rest position. In other embodiments the biasing means can be calibrated differently, resulting in a different position of the depth guide when the spring is in its rest position. In a preferred embodiment, the rest position is defined when the distal end of the depth guide is protruding out of the distal end of the cutting instrument. In this configuration, any movement of the depth guide in a proximal direction -as the cutting instrument is inserted into the defect site -applies a compression force to the spring, which biases the depth guide distally toward the rest position.

Figure 5ai depicts the cutting instrument (20) assembled with the depth guide assembly (30).

Cap assembly (170) is positioned within the anvil bore (154). As can be seen from Figure 5aii, projection (178) is contacting the proximal end (70) of the depth guide (120) and C-clip (190) is contacting the neck region (158), which prevents the depth guide (120) from moving any further in a distal direction. Spring (160) is either in its rest position, or is extended, biasing the depth guide proximally toward its rest position. In this configuration, the distal end (130) of depth guide (120) protrudes out of the distal end (60) of the cutting instrument (20), shielding the cutting blade (80) and allowing the device to be inserted through the skin and advanced toward a defect site, with the depth guide (120) effectively acting as an obturator.

As the cutting instrument (20) approaches the defect site, the protruding distal end (130) of depth guide (120) initially contacts the surface to be treated. At this stage (depicted in Figure Sbi) cap assembly (170) is removed from the anvil bore (154), thereby allowing the depth guide (120) to move proximally and fully retract into the cutting instrument. If the biasing means is extended beyond its rest position, the removal of the cap assembly (170) may allow the extended spring to move toward its rest position, retracting the depth guide in a proximal direction. In the embodiment shown, the spring is in its rest position with the depth guide protruding from the distal end of the cutting instrument. In order to contact the cutting blade (80) with the surface, the instrument is advanced further toward the surface resulting in the depth guide (120) sliding proximally within the instrument bore, compressing spring (160).

The biasing of the depth guide in a distal direction ensures that the distal end of the depth guide maintains contact with the surface of the defect. In Figure Sbi, the instrument (20) is shown positioned at the surface of a defect site, with cutting blade (80) contacting the surface to be treated. Cap assembly (170) has been removed because the obturator function of the depth guide (120) is no longer required. Figure Sbii shows the resulting proximal movement of the depth guide (120) in greater detail, where C-clip (190) is no longer contacting the neck region (158), and spring (160) is partially compressed.

In the next step, the cutting instrument is inserted into the defect site. This can be done by a user pushing the cutting instrument into the surface, for example using a screwing, rotational movement, and/or by applying a downward insertion force onto the proximal end section (184) of anvil (150), for example through the use of a surgical hammer. Controlling the angle of insertion to maintain perpendicularity of the instrument relative to the surface of the defect site is critical, and the angle of insertion can be monitored using the combination of the depth marker and the alignment markers. As discussed previously, a perpendicular insertion is achieved when the depth of insertion read using the depth marker and the second scale of alignment markers is equivalent to the depth of insertion read using the first scale of alignment markers. In the event that the two readings do not correlate with each other, a user knows that the angle of insertion is off the perpendicular, and can correct the angle of insertion before inserting the cutting instrument to its required depth. The alignment markers can also be used to assess perpendicularity, although this is a less accurate indicator that the combination of the depth marker and the alignment markers.

The insertion procedure can be paused to check for perpendicularity at a set depth, for example 4mm. Should one side of the cutting instrument be inserted too deeply (as judged using the combination of the depth marker and alignment markers), a user can apply a corrective force to the instrument to bring it back to a perpendicular position, this being evident when the depth reading shown by the depth marker correlates with the depth reading obtained using the alignment markers. When a user is satisfied that perpendicularity has been achieved, the instrument can be inserted to its required depth.

The depth of insertion of the cutting instrument into the defect site also needs to be tightly controlled. As the cutting instrument (20) is inserted into the defect site in a perpendicular orientation, depth guide (120) slides proximally within the bore (72), further compressing spring (160) as it does so. The proximal sliding movement of depth guide (120) is visible through slot (100). As the cutting instrument (20) is inserted deeper into the defect site, depth marker (144) of depth guide (120) becomes visible within slot (100) of the cutting instrument.

When depth marker (144) aligns with the equivalent graduation (112), the user knows that the cutting instrument is inserted at the exact required depth This exact insertion depth is also indicated at the proximal end of the cutting instrument, where proximal end (140) of the depth guide (120) lies exactly flush with proximal end of anvil (150). This position is depicted in Figure Sci, and in greater detail in Figure Scii. When the cutting instrument is inserted to the correct depth (as indicated at both the distal and proximal ends), spring (160) is maximally, or near maximally compressed. In this position, the cutting instrument is stable within the defect site, and the anvil (150), depth guide (120) (and the associated C-clip (190), spring (160), and 0-ring (180)) can be removed from the cutting instrument, as shown in Figure Sd. At this stage, the cutting instrument provides a conduit for surgical drill bit (40).

In the next stage, as shown in Figure Se, surgical drill bit (40) is introduced into the bore of the cutting instrument (20). The diameter of flange (200) is wider than the diameter of the anvil bore (154). A user can drill to a point where the drill bit (40) is inserted to its maximum depth within the anvil bore (as shown in Figure Sf) with flange (200) contacting the proximal end (70) of the cutting instrument (20). At this point, the distal end of drill tip (190) lies exactly flush with the distal edge of the cutting blade (80), resulting in only the required depth of target tissue being drilled. This above-described method relates to a required depth of insertion of 8mm. This depth can vary, and should the cutting instrument be inserted at a more shallow or deeper depth, the surgical drill bit will only drill away the tissue residing within the bore of the cutting instrument.

In an alternative embodiment (not shown), the cutting instrument is adapted to perform its function without requiring an anvil. In this embodiment, the cutting instrument is preferably adapted to transfer insertion forces applied to the proximal end by a user through to the cutting blade. The depth gauge functions in a similar way to that previously described, where the depth of insertion can be gauged by visualising the depth marker within the aperture, and/or by alignment of the proximal end of the depth guide with the proximal end of the cutting instrument. The bore of the cutting instrument comprises a means to anchor the biasing means. The instrument preferably comprises a means by which a user can force the protrusion of the distal end of the depth guide from the distal end of the cutting instrument.

This can be a cap assembly, adapted to fit in the proximal end of the cutting instrument.

As can be appreciated from the above description, the kit of instruments allows a user to (i) accurately insert a cutting instrument to a required depth and at the required perpendicular angle and (ii) accurately and confidently drill away the exact amount of tissue to prepare the defect site for receipt of an implant. The resulting prepared defect site is perfectly shaped for an optimal fit with a circular shaped implant, which can be delivered through the bore of the cutting instrument, or more preferably using a separate delivery device.

Claims

Claims 1. An instrument kit for preparing a defect site in a tissue of a patient, the kit comprising: a cutting instrument and a depth guide assembly, the cutting instrument comprising a tubular body and a cutting blade, the body defining a distal end, a proximal end and a bore extending longitudinally there between; the cutting blade being positioned at the distal end of the body and being suitable for insertion into a defect site; the depth guide assembly comprising an elongate depth guide having a proximal and distal end and being adapted to fit within the bore in a sliding relationship; characterised in that the kit further comprises a depth gauge, the depth gauge comprising an aperture positioned within the body of the cutting instrument and at least one depth marker positioned on the depth guide, the aperture allowing visualisation of a depth guide positioned within the bore of the cutting instrument, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualisation of a depth marker through the aperture indicates the depth of insertion of the cutting instrument.
2. A kit as claimed in claim 1, the body of the cutting instrument further comprising an at least one first alignment marker for alignment with the depth marker, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, visualised alignment of a depth marker with a first alignment marker indicates a required depth of insertion of the cutting instrument into a defect site.
3. A kit as claimed in claim 2, wherein the at least one first alignment marker is located at the position of the aperture.
4. A kit as claimed in claim 3, the cutting instrument further comprising an at least one second alignment marker, the first alignment marker being offset from the second alignment marker by the distance the most distal depth marker is marked from the distal end of the depth guide, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, a correlation between the depth of insertion judged using visualised alignment of a depth marker with a first alignment marker and the depth of insertion judged using a second alignment marker indicates a perpendicular angle of insertion of the cutting instrument into a defect site.
5. A kit as claimed in any previous claim, wherein the aperture is positioned toward the distal end of the cutting instrument.
6. A kit as claimed in any previous claim, wherein the aperture is a slot longitudinally extending along the body.
7. A kit as claimed in any previous claim, wherein the bore of the cutting instrument defines a first bore diameter at its distal end and a second bore diameter at its proximal end, the second bore diameter being larger than the first bore diameter.
8. A kit as claimed in any previous claim, wherein the depth guide assembly further comprises an anvil, the anvil being attachable to the cutting instrument and being adapted to transmit a striking force imposed thereon to the cutting blade.
9. A kit as claimed in claim 8, wherein the anvil is adapted to fit within the bore of the cutting instrument, the anvil comprising a wall defining inner and outer surfaces, and having distal and proximal ends, with an anvil bore extending therebetween.
10. A kit as claimed in claim 9 wherein the anvil is adapted to fit within the bore at the proximal end of the cutting instrument, whereby, in use, with an anvil positioned within the bore, the bore of the cutting instrument and the anvil bore are coincident with each other.
11. A kit as claimed in claim 9 or claim 10 whereby the diameter of the anvil bore is substantially the same as the second bore diameter of the cutting instrument.
12. A kit as claimed in any one of claims 8-11, wherein the proximal end of the anvil extends beyond the proximal end of the cutting instrument.
13. A kit as claimed in any one of claims 8-12, wherein the anvil comprises a flattened proximal end section.
14. A kit as claimed in any previous claim, the depth gauge being further characterised in that the length of the depth guide is adapted to indicate the required depth of insertion, whereby the combined length of the bore of the cutting instrument and the anvil bore exceeds the length of the depth guide by the required depth of insertion, wherein, in use, with the cutting instrument inserted into a defect site and the depth guide positioned within the bore, alignment of the proximal end of the depth guide with the proximal end of the anvil indicates the required depth of insertion of the cutting instrument into the defect site.
15. A kit as claimed in any previous claim, wherein the length of the depth guide isadjustable.
16. A kit as claimed in any previous claim, comprising two or more depth guides, the at least one depth marker on each being positioned differently to indicate different required depths of insertion and/or each having a different length corresponding to a different required depth of insertion.
17. A kit as claimed in any one of claims 2-16 wherein the required depth of insertion of the cutting instrument is from 1 to 8 mm.
18. A kit as claimed in any one of claims 8-17, wherein at least a portion of the anvil is manufactured from stainless steel.
19. A kit as claimed in any previous claim, wherein the depth guide assembly comprises means to effect protrusion of a depth guide from the distal end of the cutting instrument.
20. A kit as claimed in claim 19, wherein the means comprise a projection adapted to fit in the anvil bore, wherein the combined length of the projection and a depth guide exceeds the combined length of the bore of the cutting instrument and the anvil bore.
21. A kit as claimed in claim 20, wherein the projection is attached to a cap, the cap being adapted to fit over the proximal end of the anvil.
22. A kit as claimed in any previous claim, wherein the depth guide assembly comprises biasing means, adapted to resiliently bias a depth guide positioned within the bore toward a rest position.
23. A kit as claimed in claim 22, wherein, with a depth guide positioned within the bore of the cutting instrument, the rest position of the biasing means results in the distal end of the depth guide lying flush with the distal end of the cutting instrument.
24. A kit as claimed in claim 22 or claim 23, wherein the biasing means comprises an elastic material, member, or spring.
25. A kit as claimed in claim 24 wherein the spring is a tension/extension spring and/or a compression spring and/or a helical spring.
26. A kit as claimed in claim 25, wherein the inner surface of the anvil comprises a neck region internally extending into the anvil bore to define a neck region bore, one end of the spring being mountable against the neck region, the other more distal end of the spring being adapted to engage with a depth guide.
27. A kit as claimed in claim 26, wherein the diameter of the depth guide is increased at its proximal end, the increased diameter exceeding the diameter of the neck region bore, thereby preventing a depth guide positioned within the bore from egressing from the distal end of the cutting instrument.
28. A kit as claimed in claim 27, wherein the increased diameter is effected by an 0-ring or C-clip being positioned at the proximal end of the depth guide.
29. A kit as claimed in any one of claims 8-28, wherein the outer surface of the anvil comprises means to reversibly engage with an inner surface of the cutting instrument.
30. A kit as claimed in claim 29, wherein the means to engage comprises one or more projections, or one or more regions having increased diameter.
31. A kit as claimed in any previous claim, wherein the cutting instrument further comprises a handle, the handle partially covering the body leaving at least the distal end exposed.
32. A kit as claimed in any previous claim, wherein the cutting blade extends circumferentially around the distal end of the body.
33. A kit as claimed in any previous claim, the kit further comprising a surgical drill bit adapted to fit within the bore of the cutting instrument in a sliding relationship and to be rotatable about its longitudinal axis.
34. A kit as claimed in claim 33, wherein the length of the surgical drill bit is the substantially the same as the length of bore of the cutting instrument.
35. A kit as claimed in claim 33 or claim 34, the surgical drill bit further comprising a flange to prevent the surgical drill bit from protruding through the distal end of the cutting instrument.
36. A kit as claimed in any one of claims 33-35, the surgical drill bit further comprising means for attachment to a rotation device.
37. A kit as claimed in any one of claims 4-36, wherein the depth guide assembly is assembled.
38. A kit as claimed in claim 37 wherein the assembled depth guide assembly is positioned within the bore of the cutting instrument.
39. Use of the kit as claimed in any previous claim to prepare a defect site in a patient.
40. A method of preparing a defect site in a tissue of a patient, the method comprising: o providing access to the defect site through a surgical incision in the body of the patient; o with an instrument kit as claimed in claim 37, effecting the protrusion of the distal end of the depth guide from the distal end of the cutting instrument, o advancing the cutting instrument toward the defect site, the protruding distal end of the depth guide shielding soft tissues from the cutting blade as the cutting instrument advances; o positioning the cutting instrument to touch a surface of the defect site, the depth guide moving proximally within the bore until the distal end of the depth guide lies flush with the distal end of the cutting instrument; o applying an insertion force to the cutting instrument to insert the cutting instrument into the defect site to the required depth, the depth guide moving proximally within the bore until a depth marker visible through the aperture indicates that the required depth of insertion has been obtained, and/or the proximal end of the depth marker lies flush with the proximal end of an anvil positioned within the bore of the cutting instrument; o removing the depth guide assembly from the bore of the cutting instrument; o inserting a surgical drill bit into the bore of the cutting instrument and (distally advancing the rotating drill bit to) drilling tissue within the defect site (until the flange contacts the proximal end of the cutting instrument, thereby preventing further distal movement of the drill bit within the bore.)
41. A method as claimed in claim 40, the method further comprising achieving perpendicularity during the insertion step by ensuring that the depth of insertion as judged using visualised alignment of a depth marker with a first alignment marker is the same as the depth of insertion judged using a second alignment marker.
42. A method as claimed in claim 40 or claim 41, further comprising removing the drill bit from the bore of the cutting instrument.
43. A method of delivering an implant into a defect site in a tissue of a patient, the method comprising preparing the defect as claimed in any one of claims 40-42, and delivering an implant into the prepared defect site.
44. The kit, use or method of any previous claim wherein the tissue is selected from the group consisting of: cartilage, bone, ligament, tendon, meniscus, periodontal tissue, dentine, enamel, intervertebral discs, annulus fibrosus, and nucleus pulposus.
45. The kit, use or method of any previous claim wherein the patient is selected from the group consisting of: human, dog, camel, and horse.