WO2022055348A1

WO2022055348A1 - Surgical cutter

Info

Publication number: WO2022055348A1
Application number: PCT/NL2021/050545
Authority: WO
Inventors: Maikel Michaël Adrianus BEERENS
Original assignee: Xilloc Holding B.V.
Priority date: 2020-09-10
Filing date: 2021-09-08
Publication date: 2022-03-17
Also published as: NL2026444B1

Abstract

A trephine cutter (1) is provided. The cutter extends in an axial direction (A) and comprises, along the axial direction: a proximal connecting end (3) for connecting and driving the cutter (1) and a generally tubular shaft (5) surrounding an axial lumen (L) and comprising a distal cutting end (7), preferably having a generally annular shape, surrounding the axial lumen. At least part of the shaft (5) comprises one or more enclosed fluid channels (33) within the shaft for transporting a fluid in a direction from the connecting end (3) to the cutting end (7).

Description

Surgical cutter

TECHNICAL FIELD

The present disclosure relates to reamers, in particular for surgery.

BACKGROUND

Implants in the extremities of a human or of other mammals such as tibial and femoral implants are well known. Such implants tend to wear and/or fracture in time. Possible causes comprise fatigue and/or higher mechanical stress than prescribed by the manufacturer. Worn and/or damaged implants must be removed and should preferably be replaced, e.g. known as revision surgery. Thus, the value and/or success of an implant and/or an implantation surgery may be seen to include also the possible removal of the implant. Similarly, in some cases an implant should be removed from the bone, in particular if the bone has been broken (with or without damage to the implant).

Successful removal of an implant may relate to various aspects, including of the implant itself, of tools for the removal and of (risks of) collateral tissue damage to tissue surrounding the implant which may be relevant for accommodating a new implant (in particular bone tissue). Such collateral tissue damage may be due to microfractures in the bone adjacent to the cutting area and/or thermal damage.

Tools for removal of an elongated implant have been developed but are found to be inadequate. E.g. presently available reamers are found to be either too thick or too thin, considering that thick reamers tend to remove most or all of the remaining cortical bone, leaving none or too little of it for (anchoring) new implant placement. Thin reamers may be fragile and break. Further, the reamers tend to lack (creation of) space for removal of cut material from the cutting site, e.g. removal of bone fragments, which tends to increase friction and cause (over)heating of the reamer and thermal damage of the tissue such as osseonecrosis; for thick reamers heating may be in particular localized near a distal cutting end whereas in thin reamers overheating generally occurs along the entire shaft.

Different aspects of such issues and attempts to provide improved cutters have been discussed in: M.S. Austin, et al. “Previously Unreported Complication of Trephine Reamers in Revision Total Hip Arthroplasty”, The Journal of Arthroplasty, (2006) 21 (2):299-300, DOI 10.1016/j.arth.2005.04.034;

N. Bertollo and W.R. Walsh, “Drilling of Bone: Practicality, Limitations and Complications Associated with Surgical Drill-Bits”, in: Biomechanics in Applications, Dr Vaclav Klika (Ed.), (2011 ) ISBN: 978-953-307-969-1 , InTech;

T. Tanaka, et al. “A new strategy to remove broken femoral mega- prostheses with hollow trephine reamers”, Eur. J. Orthop. Surg. Traumatol. (2013) 23:357-360, DOI 10.2007/s00590-012-0974-3;

R.K. Pandey and S.S. Panda, “Drilling of bone: A comprehensive review” J. Clin. Orthop. and Trauma (2013) 4:15-30, DOI 10.1016/j.jcot.2013.01.002;

J. Soriano et al. “Study and improvement of surgical drill bit geometry for implant site preparation”, Int J Adv Manuf Technol (2014) 74:615-627, DOI 10.1007/S00170-014-5998-x.

Further, WO 2008/100484 is noted, disclosing a flexible trephine and a method of removing a bowed implant from a bone. WO 2009/151926 discloses a method and devices for treating spinal stenosis, EP 2 712 571 discloses a hollow reamer for dental purposes, WO 2011/026164 discloses a trepan drill, GB 2 463 522 discloses a controlled feed reamer and single pass cutter, and US 2009/0209964 discloses a trephine designed for removal of a bone core and equipped with a device guiding it inside the bone and combining a drill bit and tubular cutting tool.

SUMMARY

In view of the above, herewith is provided a trephine cutter, the cutter extending in an axial direction and comprising, along the axial direction, a proximal connecting end for connecting and driving the cutter and a generally tubular shaft surrounding an axial lumen and comprising a distal cutting end, preferably having a generally annular shape, surrounding the axial lumen. In the cutter, at least part of the shaft comprises one or more enclosed fluid channels within the shaft for transporting a fluid in a direction from the connecting end to the cutting end.

The axial direction is along an axis of the cutter, defined by the axis of rotation of (the shaft of) the cutter in operational rotation. Note that at least part of the cutting shaft may be flexible (see below) and the axial direction may accordingly follow bends of the shaft.

The connecting end may comprise one or more facets for connecting into a driver so that the driver can operably impart rotary and optionally axial forces to the cutter for cutting an object, in particular mammalian bone more in particular human bone. The axial lumen accommodates material not (to be) cut and/or a guide for cutting.

At least part of the one or more of the fluid channels may accommodate a fluid flow from a relatively proximal position (e.g. the connecting end) to a relatively distal position (e.g. at or near the cutting end) and back towards a proximal position (e.g. the connecting end). E.g., the channel may have a general U-shape within the shaft. However, it is preferred that one or more of the fluid channels have one or more exits at or near the cutting end for providing fluid transported through that enclosed fluid channel at or near the cutting site.

Thus, fluid, in particular coolant and/or lubricant may be transported to the cutting end through the cutter and may possibly be provided at the cutting site, in case of an exit. Coolant may cool the shaft itself and therewith cool material outside and/or inside the shaft. In particular when cutting bone overheating of the tissue may thus be prevented.

Fluid emanating from the shaft (from one or more exits of a fluid channel) may also serve for removing cut material (e.g. bone tissue) from the cutting site, preventing build-up of cut material. Lubricant may assist cutting allowing reduction of force for cutting and/or allowing reduction and/or prevention of heating by reduction of friction and/or facilitating transport of cut material along the cutter away from the cutting site and/or out of the object being cut. One fluid may serve for a combination of two or more of cooling, debris removal, flushing and lubrication.

By providing the fluid through one or more enclosed channels within the shaft, obstruction of the fluid flow is prevented, increasing reliability and/or robustness of a cutting process using the cutter.

The shaft may be provided, in particular on a radial outside, with one or more helical ribs providing lands and flutes.

The flutes may facilitate removal of cut material from the distal cutting site towards the proximal side, out of the body part or object being cut. The ribs may provide strength to the cutter. At least part of one or more of the ribs may comprise one or more relatively elevated margins and/or other reaming portions on the lands which may serve for defining an inner diameter of at least part of a hole cut with the cutter and/or an outer diameter or at least part of an outer diameter of at least part of material accommodated in the axial lumen. The lands and flutes, respectively, may have a constant shape and/or width along the shaft.

A helix angle of at least part of the lands and flutes may affect removal of cut material and may be determined with respect to one or more of the material (to be) cut, such as one or more of the amount of cut material, deformability of cut material, fluidity of the cut material, amount of flushing liquid, velocity of rotation of the cutter, etc.

At least part of one or more of the enclosed fluid channels extend through one or more of the helical ribs. This facilitates reducing a thickness of the shaft. Thus, the amount of cut material may be reduced and/or an outer size of the cut may be reduced for a given size of the axial lumen. Also or alternatively, this may reduce weight of the cutter which may facilitate manipulation and/or use of the cutter.

Although the present concepts may be applied to a trephine cutter comprising a smooth knife edge, the cutting end may comprise one or more cutting teeth. This may facilitate cutting hard and/or brittle material, e.g. bone. The teeth may be symmetric or asymmetric, e.g. having a steeper sloping side towards a forward rotation direction (or: intended forward rotation direction) of the cutter and having a gentler sloping side towards a rear side with respect to a direction of rotation (and/or an intended direction of rotation, respectively) of the cutter.

One or more of such cutting teeth may extend from one or more of the ribs, when provided.

Thus, the teeth may extend from locally thicker portions of the shaft which may provide robustness to the cutter.

The cutting teeth may be integral portions of the shaft. In some embodiments, one or more cutting teeth may comprise and/or be of one or more different materials than other portions of the shaft, e.g. being formed as portions attached to the mantle as separate elements and/or being coated with one or more other materials.

One or more of the cutting teeth may extend generally in axial direction. This facilitates use of the cutter for cutting in axial direction. A width of a cut into a material may be defined by the thickest and/or widest portion of the cutter so that in case all cutting teeth extend in axial direction along the shaft and do not extend radially outside other portions of the shaft, a cut made with the cutter will generally be narrowest and affect least material.

In some embodiments, one or more of the cutting teeth have a front side defining a rake face and a rear side defining a relief face, and at least one of the front side and the rear side continues into an associated front side and/or rear side of a helical rib. In particular, the rake face may continue smoothly into a front face of a helical rib.

A continuation of a front and/or rear side may reduce or prevent local stresses in the cutter, due to fabrication process and/or in operation, thus improving strength. Further, such cutter facilitates smooth transition from the tooth to the rib and facilitates guiding cut material into a flute adjacent the rib. It is believed that the smoother the transition, the better the guiding. Smoothness may be defined as a variation in a second derivative of a tangent to the surface along a helical path traced by the helical rib; the smaller a variation, the smoother the surface is at a particular position. Preferably, the rake face and the front face form a constant uninterrupted plane.

The rake face may define a rake angle and the relief face may define a relief angle, either or both may be optimized for cutting a particular material, e.g. mammalian bone, more in particular human bone.

In some embodiments, one or more of the cutting teeth have a front side defining a rake face and a rear side defining a relief face and wherein one or more of the enclosed fluid channels has an exit at a position between a rear side of at least one of the cutting teeth and a rake face of an adjacent cutting tooth, in particular having an exit on a rear side of at least one of the cutting teeth.

In such case, the fluid is provided close to the cutting site. This facilitates one or more of cooling along all or most of the shaft, cooling of the cutting teeth, removal of debris (i.e. cut matter) close to the location of formation of the debris into a flute rearward of the respective tooth, lubrication of the cutting site. Further, arranging the exit at an exit at a position between a rear side of at least one of the cutting teeth and a rake face of an adjacent cutting tooth, or on a rear side of a cutting tooth facilitates reducing or preventing risk of clogging of the exit by debris; note that in case the exit(s) would be arranged in the front side of a tooth, when rotating the cutter in use any debris entering such forward-facing exit would likely do so with significant force, and dislocation and removal of such debris would at least be hindered and/or require excessive fluid pressure. Also or alternatively, with an arrangement of an exit on a rear side of the cutter as specified above in combination with a forward rotation of the cutter a suction force may be produced to the fluid facilitating a fluid flow.

The exit of an enclosed fluid channel exiting on a rear side of a cutting tooth may be formed to project a portion of liquid transported through the fluid channel, in particular a jet of the liquid, towards a front side of an adjacent cutting tooth.

In such case, the fluid exiting one tooth may cool the front side of the adjacent tooth, which is prone to experience most heating. Thus, active cooling may be provided where it may be needed most. Also or alternatively, lubrication may be provided at or close to the very location of cutting the material, optimising the lubrication. Also or alternatively, providing a fluid jet may facilitate dispersal and/or dilution of debris.

The shaft may have a constant inner diametric size, i.e. the axial lumen has a constant diametric size. Also or alternatively, the shaft may have a constant outer diametric size, e.g. ribs extending to a constant radial distance about the axis. Also or alternatively, one or more of the cutting teeth may have an inner face on a radial inward side and an outer face on a radial outward side, at least one of the inward side and the outward side continuing into an associated inward side and/or associated outward side of a helical rib. In particular the inner face then continuing smoothly into an associated inner face of a helical rib and/or the outer face then continuing smoothly into an associated outer face of a helical rib.

Thus, such cutter may have a generally cylindrical shape with respect to the axis. This allows reduction of the amount of material affected by a rotary cutting action using the cutter.

It is noted that some trephine cutters have cutting teeth extending radially outward with respect to a body section of the shaft for passage of cutting debris and/or for prevention of friction; thus a wide cut is made compared to the thickness of the body section. This is obviated by the cutter according to one or more of the present concepts.

One or more cutting teeth may have a radial cutting edge. Also or alternatively, one or more cutting teeth may have a non-radial cutting edge, e.g. at least part of the cutting edge having an axial and/or tangential component of direction. At least part of the shaft may be flexible about the axis for cutting along a bent path, e.g. so that the axial lumen may accommodate a bent object. In such case of a flexible shaft section, the cutter axis may not be straight but bent at least locally. In particular, the cutter may allow sideways deformation of the shaft yet retaining a cutting action generally in (local) axial direction. In an embodiment of a cutter having such at least partly flexible shaft, at least part of the shaft may be formed as an at least partly helical element between the proximal end and the distal cutting end.

The cutter may be used on an object comprising different materials, in particular as a reamer for isolating and/or removal of an object. In such case, the axial lumen may accommodate a portion of the object not to be cut. For reduction of an amount of material (in particular tissue) affected by the cutting, the shaft should follow the material in the axial lumen as close as possible and/or the axial lumen should have a small size. In particular for removal of a bent portion of an implant out of a piece of bone tissue, the flexible shaft may allow adaptation of the cutting path along the bent implant portion so as to minimise the amount of bone tissue removed and maximise the amount of remaining bone tissue.

Although several designs for a flexible shaft are possible, in one or more embodiments at least part of the shaft comprises at least one at least partly helical element forming more than one turn about the axis, and at least a portion of one helical turn is interlocked to an adjacent portion of a previous turn adjacent the at least part of the one turn, and/or at least part of the cutter comprises plural at least partly helical elements adjacent each other and at least part of one helical element is interlocked to an adjacent part of an adjacent helical element; and wherein the thus formed interlocked portions and/or elements are interlocked for at least partially imparting and/or transferring rotary and/or axial forces from the proximal end towards the cutting end for cutting by rotating the cutter about the axis.

By provision of one or more helical elements, e.g. in the shape of a helical spring, the shaft may deform sideways while rotary and axial forces may be imparted and/or at least in part be transferred along, respectively, the helical element(s) and/or from one turn to the next turn and/or from one helical element to the adjacent helical element. By provision of interlocking structures the transmission may be improved and/or an amount of deformation be limited, e.g. to within predetermined amounts. Also, radial size variation, e.g. widening or narrowing of the cutter seen in transverse cross section at the axial position of the helical element(s), may be prevented.

E.g. the helical element(s) may have a helix angle in the direction of rotation of the cutter, so that in operation and/or when the shaft subjected to axial forces, the shaft will tend to increase its diameter. This may prevent that the cutter reduces a size of the axial lumen and clamps onto material accommodated in the lumen. Such effect may also or alternatively be provided or increased by forming (e.g. cutting) at least part of the edges with a tapering angle with respect to the axis in an outward direction (such that at least part of a proximal turn is forced outward by an adjacent part of a distal turn).

The interlocking structures may be formed in any suitable manner, e.g. as and/or by interlocking dovetails and/or jigsaw patterns formed by undulating cuts, etc.

It is preferred that the cutter comprises an annular portion on a proximal side and/or on a distal side of the flexible part of the shaft, which may improve structural robustness of and/or control over the cutter in use. An annular portion on a distal side of the flexible part may comprise one or more cutting teeth. Such cutter may comprise further annular portions.

In such at least partly flexible cutter, at least one of the one or more enclosed fluid channels may extend through at least part of the flexible part of the shaft, in particular through at least part of a helical element if applicable, for transporting fluid from the connecting end to the cutting end passing through at least part of the flexible part of the shaft.

Thus, also a cutter having a flexible part may provide one or more of the benefits discussed herein.

One or more of the helical elements may comprise one or more of the enclosed fluid channels.

Any cutter provided herein may comprise at least one manifold within the shaft, fluidly connecting at least one of the one or more enclosed fluid channels with plural channel exits and/or fluidly connecting plural enclosed fluid channels with each other.

Thus, distribution of fluid may be improved e.g. evening a fluid pressure between several of the channels. In case of a cutter comprising an annular portion on a proximal side and/or on a distal side of a flexible part of the shaft, as described above, a manifold may be arranged in one or more of such annular portions.

Also or alternatively, a manifold fluidly connecting plural enclosed fluid channels with each other may connect the plural enclosed fluid channels with a common fluid inlet.

The cutter may be provided with at least one handle at least part of which extending substantially radial and/or tangential to the axis, and at least part of the cutter then being rotary about the axis with respect to the handle.

The handle facilitates manipulation and/or control of the cutter. Also or alternatively, the handle may provide one or more of a connection for supplying fluid to the cutter, a manifold for distributing fluid, a connection for a rotary and/or axial driver for the cutter, one or more sensors.

In view of the above, herewith also an assembly is provided comprising a trephine cutter as disclosed herein, a cutter driver for rotating the cutter, and a fluid supply for supplying fluid to the one or more enclosed channels

The assembly facilitates use of the cutter. The driver may comprise a rotary drive and/or an axial drive. The fluid supply may comprise one or more fluid controls for controlling one or more of fluid pressure, temperature, fluid composition fluid flow (e.g. one or more of velocity, flux, amount, etc.), sterilisation. The fluid may be a liquid e.g. water, saline, etc.

In view of the above, herewith also a method is provided comprising the steps of: providing a cutter as disclosed herein and/or an assembly as disclosed herein, rotating the cutter for cutting the object and flowing a fluid through at least one of the one or more enclosed fluid channels within the shaft thus transporting a fluid from the connecting end towards the cutting end.

In an embodiment of the method, the object comprises a first portion and a second portion, and the method comprises accommodating at least part of the first portion inside the axial lumen, cutting the object around the at least part of the first portion and removing the first portion from the second portion. In particular the first portion may comprise, or be substantially of, a first material and the second portion then may comprise, or be substantially of, a second material different from the first material. More in particular, the first portion may be or comprise an implant and the second portion may be bone tissue.

Further, it is noted that at least part of the tubular shaft, preferably the entire shaft, more preferably the shaft and the connecting end, and possibly the entire cutter, may be manufactured by one or more additive manufacturing techniques. The additive manufacturing techniques may comprise fusing of metal particles, preferably of one or more of titanium alloys, stainless steel and cobalt chromium alloys, and/or fusing of polymers and/or sealing materials such as one or more of (artificial) rubbers and thermoplastic polyurethane (TPU).

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described aspects will hereafter be more explained with further details and benefits with reference to the drawings showing a number of embodiments by way of example.

Fig. 1 shows a trephine cutter 1 in side view;

Fig. 2 is a detail perspective view of the distal cutting end of the cutter of Fig. 1 ;

Fig. 3 shows a cross section perpendicular to the axis A in plane III indicated in Fig. 1 ;

Fig. 4 is a cross section view along the axis A, in plane IV indicated in Fig. 3;

Fig. 5 shows a detail perspective view of the proximal connecting end of the cutter of Fig. 1 ;

Fig. 6 is the detail of Fig. 5 with part of the mount removed;

Fig. 7 is the detail of Fig. 6 with a further part of the mount removed;

Figs. 8 - 10 show a flexible trephine cutter;

Fig. 11 indicates a method of cutting an object using a flexible trephine cutter according to the present concepts.

DETAILED DESCRIPTION OF EMBODIMENTS It is noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms "upward", "downward", "below", "above", and the like relate to the embodiments as oriented in the drawings, unless otherwise specified. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral, where helpful individualised with alphabetic suffixes.

Further, unless otherwise specified, terms like “detachable” and “removably connected” are intended to mean that respective parts may be disconnected essentially without damage or destruction of either part, e.g. excluding structures in which the parts are integral (e.g. welded or moulded as one piece), but including structures in which parts are attached by or as mated connectors, fasteners, releasable self-fastening features, etc. The verb “to facilitate” is intended to mean “to make easier and/or less complicated”, rather than “to enable”.

Fig. 1 shows a trephine cutter 1 in side view. The cutter 1 extends in an axial direction along an axis A and comprises, along the axial direction a proximal connecting end 3 for connecting and driving the cutter and a generally tubular shaft 5 surrounding an axial lumen and comprising a distal cutting end 7 provided with cutting teeth 9. Fig. 2 is a detail perspective view of the distal cutting end 7, as indicated in Fig. 1 , showing the distal cutting end 7 being generally annular and surrounding the axial lumen L providing an entrance to the lumen L. Fig. 3 shows cross section plane III and Fig. 4 is a cross section view with respect to plane IV containing the axis A, planes III, IV being mutually perpendicular.

The cutter 1 is provided with a mount 11 . The cutter 1 is provided with a handle 13, here being attached to the mount 11 and extending substantially radial to the axis A. The cutter 1 is rotary about the axis A with respect to the mount 11 and therewith with respect to the handle 13. For connecting and driving the cutter the connecting end 3 comprises a driving connector 14, such as the shown faceted shaft section and/or some other suitable connector, for connecting the cutter to a driver (not shown) for rotary driving the cutter and possibly also for providing axial impulses to the cutter 1 for cutting hard and brittle substances. The mount 11 comprises a fluid inlet 15, here as an option being provided with a Luer-type connector 17 for attachment of a fluid supply, see also below. The cutter 1 may be replaceable in the mount 11 for re-use of the mount 11 with different cutters 1 .

The shaft 5 is provided with plural helical ribs 19 providing lands 21 and flutes 23 and for which a helix angle a may be defined. At least part of the ribs 19 may be provided with additional cutting structures such as reaming margins (not shown).

The cutter 1 is configured for rotation in clockwise direction about the axis A, as may be seen from the shape and/or (helical) direction of the ribs 19 and/or the cutting teeth 9. The helical ribs 19 may assist propelling cut material from the cutting end towards the connecting end when the shaft 5 is thus rotating.

Best seen in Fig. 2, each of the cutting teeth 9 extends from a rib 19 and generally extends in an axial direction. The cutting teeth 9 have a front side 9F defining a rake face 25 and a rear side 9R defining relief faces 27. In the shown embodiment, the rear side 9R is, as an option, multifaceted, but a smoothly curved and/or a straight rear face could be used as well. In the shown embodiment, the front side 9F and the rear side 9R continue into the associated front side 19F and, respectively, rear side 19R of a helical rib 19. The rake face 25 may define a rake angle equal to or different from the helix angle a of the associated (front side 19F of) rib 19. Note that the front and rear sides 19F, 19R of the ribs 19 may at least partly be rounded as shown, which may prevent local accumulation of mechanical stress.

Figs. 2-4 show that the shaft 5 has a constant inner diametric size d. The cutting teeth 9 have an inner face 9I on a radial inward side and an outer face 90 on a radial outward side. The inward sides 9I continue smoothly and uninterruptedly into an inward side 191 of an associated helical rib 19 (e.g. indicated as imaginary separation S in Figs. 2-3) here forming a plane inner surface 29 of the shaft 5 defining the lumen L. However, other embodiments (not shown) may comprise, also or alternatively, one or more cutting teeth and/or ribs extending radially inward for cutting material on a radial inside, i.e. within the axial lumen.

In the shown cutter, the ribs 19 have constant size and separation and, apart from the rotation inherent from the helicity of the helical ribs 19, the shaft 5 has a constant cross sectional shape along its length. However, at the cutting end 7 the cutting teeth 9 have a slightly larger radial thickness than the associated ribs 19 and protrude further out. Thus, the cutting teeth 9 are strengthened with respect to the remainder of the shaft 5 and the teeth 9 provide for cutting action radially outside from the shaft 5 which may create space for accommodating the cutter in the cut object thus increasing space for removal of debris and/or transport of fluid (see below) and/or for preventing contact between the shaft and the cut object for prevention of friction and heat build-up. Note that one or more of the cutting teeth 9 may have other shapes than shown. In particular, some teeth might have a taper, a bevel or a chamfer in radial direction to provide a relatively sharp and/or relatively rounded end in radial direction in addition to or in contrast to a relatively sharp and/or relatively rounded end in circumferential direction as in the Figures. E.g. some cutting teeth may in particular be rounded on a radial inner side so as to reduce chances of cutting into an object accommodated in the axial lumen. This may be particularly relevant for cutting bone around metal implants: metal cutting teeth may otherwise get damaged against such metal implant, especially in the case of a flexible cutter (see below).

Also, best seen in Fig. 2, in the cutting end, the lands 21 comprise optional sections, here end sections 31 , with greater depth as seen from an outside (as in the viewpoints of Figs. 1 -2), i.e. having locally relatively thinner wall sections in radial direction. Such sections may improve force distribution between the separate cutting teeth and the annular portion of the shaft by providing one or more portions of intermediate thicknesses between adjacent portions of the cutter and preventing one or more of large differences in size, mechanical properties, thermal properties, sharp edges and sharp corners.

Figs. 2-4 show that the shaft 5 comprises plural enclosed fluid channels 33 within the shaft 5, i.e. the channels being separated from the axial lumen by the shaft material, for transporting a fluid from the connecting end 3 to the cutting end 7. The enclosed fluid channels 33 extend through the helical ribs 19.

In the shown embodiment, the enclosed fluid channels 33 have exits 35 at the cutting end 7 for providing fluid transported through the respective enclosed fluid channel 33 at or near the cutting site. Here, each channel 33 has one exit 35 but in another embodiment (not shown) one or more channels may have more than one exit. One or more exits may be arranged on a radial inside of the shaft 5 directing fluid into the axial lumen (not shown), and/or on a radial outside of a land 21 , and/or on a front side 19F of a rib 19 and/or a rear side 19R of a rib 19. As a particular option, the channels 33 extend through at least part of the teeth 9 for cooling these. The shown exits 35 are arranged on a rear side 9R of the cutting teeth 9, although one or more exits on a rear side 19R of a rib 19 could also be provided as indicated above. A flute portion 31 adjacent the exit 35 may be formed for assisting direction of fluid emerging from the exit 35 and/or assisting prevention of obstruction of the exit 35 by debris.

Some, preferably all, exits 35 of the fluid channels 33 may be formed to project a portion of liquid transported through the fluid channel 33 in a predetermined direction, in particular as a liquid jet. In particular, like here, one or more exits 35 on a rear side 9R of a cutting tooth 9 may be formed to project a liquid jet towards a front side 9F of an adjacent cutting tooth 9. At least part of a flute portion 33 adjacent the exit

35 may be formed for assisting formation and/or direction of such jet.

Figs. 4-7 show that the mount 11 comprises a sleeve 36 which surrounds the connecting end 3 of the cutter 1 ; the sleeve 36 is removed in Figs. 6-7). The (sleeve

36 of the) mount 11 is fixed to the cutter 1 in axial direction but allows relative rotation about the axis A. Here, the axial fixation is by provision of a flange 37 and circumferential groove 39 in the connecting end 3 of the cutter 1 and a corresponding parker 39 fixed in the mount 11 and protruding into and fitting the groove 38. An optional sleeve 40 facilitates relative rotation of the cutter 1 and (the sleeve 36 of) the mount 11 , e.g. acting as a bearing; the sleeve 40 is removed in Fig. 7. Such sleeve 40 may comprise an outer layer of a metal or of a polymer or be formed as a whole of a polymer or of a metal. However, other suitable mechanical connections and/or bearings may be provided.

For providing fluid to the enclosed channels 33 of the cutter 1 , the cutter 1 provides a fluid connection at the connecting end 3. In the shown embodiment, the fluid connection is, as an option, integrated into the mechanical connection of the mount 11 . Best seen in Figs. 4 and 7, the connecting end 3 comprises a circumferential fluid channel 39, fluidly connected with the enclosed fluid channels 33 by channel exits/entrances 41 of each channel 33. Thus, the enclosed fluid channels are all connected with each other. When the sleeve 36 is connected to the cutter 1 the fluid channel 39 is in fluid communication with the fluid inlet 15, and is sealed with circumferential seals 43. Here, the seals 43 comprise O-rings 45 in circumferential grooves 47 in the cutter 1 . The O-rings may have an X-shape in cross section for providing a double sealing contact as shown, but they may be of any type.

Another embodiment (not shown) may comprise one or more fluid channels accommodating a fluid flow from such proximal mounting portion to at or near the cutting end and back towards the connecting end wherein such channels generally U-shaped within the shaft have entrances and exits at different axial positions. For providing fluid to the enclosed channels and receiving fluid from the enclosed channels, the entrances and the exits may both be provided with a respective fluid connection as described above.

Figs. 8A-10B show as another embodiment a trephine cutter 100. Like Figs 1 , 3 and 4 before, Figs. 8A-8B show the cutter 100 in side view in two configurations; Fig. 9 shows cross section plane IX and Figs. 10A, 10B are cross section views with respect to plane X containing the axis A, planes IX, X being mutually perpendicular.

Best seen from a comparison of Figs. 8A-8B and 10A-10B, in the cutter 100 part of the shaft 105 is flexible about the axis A’ for cutting along a bent path, such that the axis of rotation of the shaft traces a bent path which may deviate, locally or as a whole, from a straight direction (A) as indicated with an angle y. The local direction of the path and the (expected) axis of rotation of the shaft 105 may be determined by taking plural cross sections of the shaft in a substantially perpendicular direction to the local direction of extension of the shaft, defining a midpoint of the cross section shape and connecting the midpoints of adjacent such cross sections.

In particular, part 105A of the shaft 105 is formed as a helical element 149 between the proximal mounting end 103 and the distal cutting end 107. The helical element 149 forms multiple turns about the axis A’ as a helical spring at a helix angle 0. The helical element 149 is provided with undulating side edges 151 forming interlocking dovetails of adjacent turns. The turns are movably interlocked for imparting and/or transferring rotary axial forces from the proximal end 103 towards the cutting end 107 for cutting by rotating the cutter 100 about the axis A’. The interlocking provides some play between the adjacent edges so that at least part of the shaft 105 can move sideways while the edges remain operably interlocked and detachment of (the edges of) adjacent turns of the helical element is prevented. Such undulating shape may be provided by (laser) cutting of a tubular element and/or by additive manufacturing of at least part of the cutter. The edges may have a shape which may differ in different portions of the shaft, e.g. for locally providing different amounts of flexibility. This may in particular apply at or near an end of the edges, e.g. at or near an end of the shaft 105 and/or at or near an end of a helical element and connection to another shaft portion such as e.g. an annular portion. The different shape may comprise one or more straight (not-undulating) portions compared with a scale of undulations elsewhere along the shaft 105. An end of an edge may be provided with a rounding, e.g. an at least partially substantially circular portion at an end of a cut to prevent stress build-up. Such substantially circular portion may be wider than at least part of the cut itself adjacent the circular portion.

The shaft 105 is provided with helical ribs 119 at helix angle a providing lands 121 and flutes 123 which extend over plural turns and crossing edges 151 due to the difference between the helix angles a and 0.

Best seen in Figs. 9-1 OB the shaft 105 comprises an enclosed fluid channel 133 within the shaft for transporting a fluid in a direction from the connecting end 103 to the cutting end 107. The enclosed fluid channel 133 is contained in the helical element 149.

In an embodiment, not shown, having plural helical elements, one or more of the helical elements may comprise one or more enclosed fluid channels. In such embodiment some of the enclosed fluid channels may be interconnected for accommodating a fluid flow from a relatively proximal position (e.g. the connecting end) to a relatively distal position (e.g. at or near the cutting end) through one helical element and back towards a proximal position (e.g. the connecting end) through another helical element.

In the embodiment shown in Figs. 8A-10B, the helical element has a generally constant shape and size along its length (both along the helical path traced by the element) and along the axial length of the shaft 105, apart from the undulations of the edge, and the shape of the edges is constant along the helical element and the helix angle 0 is (at least when the cutter 100 is straight and free from external loads and/or local outside forces) constant along the axis A’. However, in other embodiments (not shown) one or more helical elements may have a varying size and/or helix angle (in radial and/or in axial direction with respect to the axis A’) along the length of the respective helical element. This may assist providing locally varying bending strengths and/or bending radii of the respective element and/or of the shaft as a whole.

In the shown embodiment, as an option, the flexible cutter shaft part 105’ is contained within the shaft 105, the edge 151 being finite and bound within the length of the shaft 105. In particular, on the proximal side of the cutter 100 a proximal portion of the shaft 105 and the mounting end 103 limit the flexible cutter shaft part 105’. The mounting end 103 and the proximal portion of the shaft 105 provide, like the mounting end 3 discussed above, as an option, a manifold for providing fluid access to the enclosed fluid channel 133. As an option, on the distal side of the of the cutter 100 the cutting end 107 limits the flexible cutter shaft part 105’; e.g. by being formed as an annular element as in the shown embodiment. The cutting end 107 is, as an option, provided substantially identical to the cutting end 7 discussed above, except that it is provided with an optional enclosed manifold channel 153 fluidly connecting the enclosed fluid channel 133 with the channel exits 135 on the rear sides of the cutting teeth providing a fluid manifold. The manifold channel 153 may have an annular portion, as here, extending fully around the axis A’ in circumferential direction. Also or alternatively, plural manifold channels may be provided (not shown).

By appropriately sizing of at least part of the enclosed fluid channel 133, at least part of the manifold channel 153 and at least some of the channel exits 135 - preferably all of the channel exits 135 - a substantially even fluid pressure distribution may be provided at the respective the exits 135 in operation and when fluid is provided at the fluid inlet 115, 117 at appropriate flux and pressure. E.g., the manifold channel 153 may have a smaller cross sectional open size (fluid transmission area) than the enclosed channel 133, or the enclosed channels 133 when present, and the cross sectional open size of the exits 135 fluidly connected with the manifold channel 153 may provide, together, a larger flow resistance than the manifold channel 153. Thus, the fluid pressure of channels may be decisively determined by the exits 135 improving fluid control and possibly control over jet formation of fluid emerging from the exits. Similarly in (shaft 5 of) cutter 1 the fluid pressure in one or more of the enclosed channels 33, preferably each channel 33, may be decisively determined by the exit(s) 35 of the respective channel(s) 33.

The cutter 100 and/or the cutter 105 may be manufactured by additive manufacturing e.g. by laser welding of deposited metal particles; the lumen I lumina of one or more enclosed channels may be formed by leaving the respective portion open and/or by multi-material additive manufacturing and by filling the portion of the respective lumen-to-be with a sacrificial material. After completion of the additive manufacturing step, the cutter may be subjected to one or more post addition-step processes such as heat treatment and/or sintering bake off. The cutter may be of, or at least be substantially of, tantalum. At least part of the cutter may be provided with a surface coating of another material and/or be provided with a surface treatment for one or more of polishing, hardening, and/or otherwise increasing durability. At least part of the cutter may be manufactured for single use and/or be sterilisable.

Fig. 11 schematically indicates a method of cutting an object 260 using a flexible cutter 200 according to the present concepts. However, in contrast to the cutter 100, in the cutter 200, as an option, the ribs 219 and helical elements 249 have opposite helicity about the axis A”, see helix angle a” of ribs and helix angle p” of the helical elements indicated in Fig. 11 . The object 260 comprises a first portion 261 and a second portion 263 of different materials, e.g. the first portion 261 being a metal implant and the second portion 263 being bone tissue. The cutter is operably connected with a driver 255 for rotating at least shaft 205 of the cutter 200, and with a liquid supply 257 for controllably providing a constant liquid flow through (enclosed channels within) the cutter shaft 205 thus transporting the fluid from the connecting end 203 towards the cutting end 207 of the cutter 200.

Part of the first portion 261 is accommodated inside the axial lumen of the shaft 205. Part of the second portion 263 of the object 260 is cut around the first portion 261 . During at least part of the cutting, cut debris is flushed from the cutting site (where (cutting teeth of) the cutting end cut and remove material from the object 260) by the fluid and at least part of (the shaft 205 of) the cutter 200 and part of the object 260 are cooled by the fluid.

At least part of the flexible shaft 205 of the cutter may follow the curved shape of the implant 261 , preventing scraping off material from the implant 261 and/or preventing damaging the cutter. Note that metal particles from an implant and/or from a metal cutter may form corpora aliena in the bone and/or in the body of the bone’s owner and/or bone’s recipient which may cause inflammations and/or other medical complications in a patient. Flushing the cutting site and/or along the cutter with fluid may also reduce the risk of such noxious debris remaining in the cut (e.g. in a wound site).

After cutting to a sufficient depth, the cutting is halted and at least part of the first and second portions 261 , 263 are separated and at least part thereof may be further separated. E.g., the implant 261 may have been cut loose from the bone and the two be disassembled from each other. Thereafter, the removed implant 261 may possibly be replaced by a new implant and/or the bone 262 may be surgically treated otherwise.

The disclosure is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims. For instance, a cutter shaft may be longer or shorter or wider or narrower than shown and/or a different ratio of outer diameter and inner diameter may be provided. Cutting teeth may be provided in different numbers and/or they may have a different shape. A flexible cutter may comprise a shaft having plural annular portions in between cut portions, helical or not. Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise.

Claims

1. Trephine cutter (1 , 100, 200), the cutter extending in an axial direction (A, A’) and comprising, along the axial direction (A, A’): a proximal connecting end (3, 103) for connecting and driving the cutter and a generally tubular shaft (5, 105) surrounding an axial lumen (L) and comprising a distal cutting end (7, 107), preferably having a generally annular shape, surrounding the axial lumen (L), wherein the cutting end (7, 107) comprises one or more cutting teeth (9, 109) having a front side (9F) defining a rake face (25) and a rear side (9R) defining a relief face (27), wherein at least part of the shaft (5, 105) comprises one or more enclosed fluid channels (33) within the shaft (5) for transporting a fluid in a direction from the connecting end (3) to the cutting end (7), and wherein one or more of the enclosed fluid channels (33) has an exit (35) at a position between a rear side (9R) of at least one of the cutting teeth (9) and a rake face (25) of an adjacent cutting tooth (9).

2. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein the shaft (1 , 105) is provided with one or more helical ribs (19, 119) providing lands (21 , 121 ) and flutes (23, 123).

3. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein one or more of the enclosed fluid channels (33, 133) extend through one or more of the helical ribs (19, 119).

4. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein one or more of the cutting teeth (9, 109) extend from one or more of the helical ribs (19, 119).

5. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein one or more of the cutting teeth (9, 109) extends generally in axial direction.

6. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein at least one of the front side (9F) and the rear side (9R) continues into an associated front side (19F) and/or rear side (19R) of a helical rib, in particular the rake face (25) continuing smoothly into a front face (19F) of a helical rib (19).

7. Trephine cutter (1 , 100, 200) according any preceding claim, wherein one or more of the enclosed fluid channels (33, 133) has an exit (35, 135) on a rear side (9R) of at least one of the cutting teeth (9, 109).

8. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein the exit (35, 135) of an enclosed fluid channel (33, 133), in particular an exit of an enclosed fluid channel exiting on a rear side (9R) of a cutting tooth (9, 109) is formed to project a portion of liquid transported through the fluid channel (33, 133), in particular a jet of the liquid, towards a front side of an adjacent cutting tooth (9, 109).

9. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein the shaft (5, 105) has a constant inner diametric size and/or a constant outer diametric size; and/or wherein one or more of the cutting teeth (9, 109) have an inner face (9I) on a radial inward side and an outer face (90) on a radial outward side and wherein at least one of the inward side and the outward side continues into an associated inward side and/or associated outward side of a helical rib (19, 119), in particular the inner face continuing smoothly into an associated inner face of a helical rib (19, 119) and/or the outer face continuing smoothly into an associated outer face of a helical rib (19, 119).

10. Trephine cutter (100, 200) according to any preceding claim, wherein at least part (105A) of the shaft (105) is flexible about the axis (A’) for cutting along a bent path, e.g. at least part (105A) of the shaft (105) being formed as an at least partly helical element (149) between the proximal end (103) and the distal cutting end (107).

11 . Trephine cutter (100, 200) according to claim 10, wherein at least part of the shaft (105A) comprises at least one at least partly helical element (149) forming more than one turn about the axis (A’), and at least a portion of one helical turn is interlocked to an adjacent portion of a previous turn adjacent the at least part of the one turn, and/or wherein at least part of the cutter (100) comprises plural at least partly helical elements (149) adjacent each other and at least part of one helical element (149) is interlocked to an adjacent part of an adjacent helical element (149); and wherein the thus formed interlocked portions and/or elements are interlocked for at least partially imparting and/or transferring rotary and/or axial forces from the proximal end (103) towards the cutting end (107) for cutting by rotating the cutter about the axis (A’).

12. Trephine cutter (100, 200) according to claim 10 or 11 , wherein at least one of the one or more enclosed fluid channels (133) extends through at least part of the flexible part (105A) of the shaft, in particular through at least part of a helical element (149) if applicable, for transporting fluid from the connecting end (103) to the cutting end (107) passing through at least part of the flexible part of the shaft (105).

13. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein the cutter (1 , 100) comprises at least one manifold fluidly connecting at least one of the one or more enclosed fluid channels (33, 133) with plural channel exits (35, 135) and/or fluidly connecting plural enclosed fluid channels (33, 133) with each other.

14. Trephine cutter (1 , 100, 200) according to any preceding claim, wherein the cutter (1 , 100) is provided with at least one handle (13, 113) at least part of which extending substantially radial and/or tangential to the axis (A, A’), and at least part of the cutter (1 , 100) being rotary about the axis (A, A’) with respect to the handle (13, 113).

15. Assembly comprising a trephine cutter (1 , 100, 200) according to any preceding claim, a cutter driver (255) for rotating the cutter (1 , 100, 200), and a fluid supply (257) for supplying fluid to the one or more enclosed channels.

16. Method of cutting an object (260), in particular a piece of bone, comprising providing a cutter (1 , 100, 200) according to any one of claims 1-14 and/or the assembly according to claim 15, rotating the cutter (1 , 100, 200) for cutting the object (260) and flowing a fluid through at least one of the one or more enclosed fluid channels (33, 133) within the shaft (5, 105, 205) thus transporting a fluid from the connecting end (3, 103) towards the cutting end (7, 107).

17. Method according to claim 16, wherein the object (260) comprises a first portion (261 ) and a second portion (262), the method comprising accommodating at least part of the first portion (261 ) inside the axial lumen (L), cutting the object (260) around the at least part of the first portion (261 ) and removing the first portion (261 ) from the second portion (262), wherein in particular the first portion (261 ) comprises or is of a first material and the second portion (262) comprises or is of a second, different, material, wherein more in particular the first portion (261 ) is an implant and the second portion (262) is bone tissue.