WO2013179013A1

WO2013179013A1 - Surgical instruments

Info

Publication number: WO2013179013A1
Application number: PCT/GB2013/051399
Authority: WO
Inventors: James Anderson; Gary Moore
Original assignee: Depuy (Ireland)
Priority date: 2012-06-01
Filing date: 2013-05-28
Publication date: 2013-12-05
Also published as: GB201304721D0; GB201209812D0

Abstract

A kit and an assembly of surgical instruments for use in preparing a cavity within a bone of a patient and corresponding method are described. A guide tube has a proximal end, a distal end, a guide tube bore extending between them along a guide tube longitudinal axis and a releasable attachment mechanism at the proximal end. An adjustable stop has a central bore for receiving an instrument extending along an adjustable stop longitudinal axis, a stop surface presented at a proximal end and an attachment formation distal to the stop surface for engaging the releasable attachment mechanism of the guide tube. The adjustable stop includes an adjustment mechanism operable by a user to vary the position of the stop surface along the longitudinal axis relative to the guide tube and a lock selectively actable by a user to allow operation of the adjustment mechanism.

Description

Surgical Instruments

The present invention relates to surgical instruments and in particular to controlling the depth of insertion of surgical instruments into a surgical site.

The accurate placement of implanted components is often a factor in the success of a surgical procedure. The accurate placement of implanted components can be difficult to achieve in open surgical sites such as the knee or hip during orthopaedic surgical procedures. The accurate placement can be more challenging in minimally invasive approaches in which access to the surgical site is more limited. Accurate placement can be even more challenging when the surgical site is not open, i.e. is within a bone and not on an outer surface.

For example, WO 2010/097636 describes an assembly for deploying a support structure implant within a bone cavity to support the bone and an insertion tool. The described support is particularly suited for implantation in a cavity within the femoral head in order to reinforce the femoral head.

WO 2008/099187 and WO 2010/013027 describe instruments for forming cavities in bone suitable for receiving such support structure implants. However, such devices can require considerable operator skill and experience and provide little control over accurate positioning of the cavity within the bone.

Hence, it would be beneficial to provide surgical instrumentation allowing the more accurate and controllable creation of cavities in bone for the insertion and/or implantation of surgical implants in a cavity within a bone.

A first aspect of the invention provides a kit of surgical instruments for use in preparing a cavity within a bone of a patient. The kit can comprise a guide tube and/or an adjustable stop. The guide tube can have a proximal end, a distal end, a guide tube bore extending therebetween along a guide tube longitudinal axis. The guide tube can further comprise a releasable attachment mechanism at the proximal end. The adjustable stop can have a central bore for receiving an instrument and extending along an adjustable stop longitudinal axis. The adjustable stop can further comprise a stop surface presented at a proximal end and an attachment formation distal to the stop surface for engaging the releasable attachment mechanism of the guide tube. The adjustable stop can also include an adjustment mechanism operable by a user to vary the position of the stop surface along the longitudinal axis.

The range of adjustment of the adjustable stop can be at least 50mm and preferably at least 60mm. The range of adjustment of the adjustable stop can be not more than 200mm, preferably not more than 150mm and more preferably not more than 125mm. The range of adjustment of the adjustable stop is preferably from 60mm to 125mm.

The guide tube and adjustable stop can be used with a variety of different surgical instruments which can interact with parts of the guide tube or adjustable stop in order to guide or otherwise control the use of the different surgical instruments during the surgical procedure. In particular, the adjustable stop can be used to set a maximum insertion depth so that the depth of insertion of different surgical instruments into a surgical site can be controlled.

The kit of parts can further comprise a soft tissue protector. The soft tissue protector can have a proximal end, a distal end and a soft tissue protector bore extending therebetween along a soft tissue protector longitudinal axis. The guide tube can be dimensioned to be received concentrically within the soft tissue protector bore. The soft tissue protector can act to protect the patient's soft tissue from other instruments, particularly cutting instruments such as drills, cutters, reamers or broaches which may be used with the other parts of the kit of parts.

The soft tissue protector can include a handle. The handle can be used by a surgeon to control the positioning or angle of the soft tissue protector. The handle can extend laterally from the soft tissue protector. The handle can be arranged so as not to obscure access to the soft tissue protector bore, for example by not impinging on or overlapping the longitudinal axis of the instrumentation.

The guide tube can have a stop formation. The soft tissue protector can have a stop surface. The stop surface of the soft tissue protector can be at the proximal end or be a proximal most part of the soft tissue protector. The stop formation and stop surface can co-operate to limit the extent of travel of the guide tube within the soft tissue protector bore. Hence, the soft tissue protector can provide a fixed datum which fixes the position of the guide tube and hence parts connector to, or attached to, or used with the guide tube. The guide tube can be longer than the soft tissue protector. In his way, the guide tube can extend into the patient's bone to provide guidance of other instrumentation within the patient's bone.

The kit of parts can include an anti-rotation mechanism to prevent relative rotation between the guide tube and the adjustable stop themselves. The guide tube can include a first part of the anti-rotation mechanism. The adjustable stop can include a second part of the anti-rotation mechanism. The first and second parts can co-operate to prevent relative rotation between the adjustable stop and the guide tube about their longitudinal axes. The first part can be in the form or one or more spigots or teeth. The second part can be in the form of one or more sockets or notches. The first and second parts can be provided on engagable surfaces or parts of the guide tube and adjustable stop. The first and second parts can be positioned in registration with each other. A pair of opposed first parts can be provided and a pair of opposed second parts can be provided. The kit of parts can further comprise an instrument. The instrument can include a second part of the anti-rotation mechanism. The first and second parts can be arranged to cooperate to prevent relative rotation between a part of the instrument and the guide tube about the longitudinal axis. The kit of parts can further comprise an instrument including an attachment formation for engaging the releasable attachment mechanism of the guide tube.

The instrument can be a drill. The drill can be a cannulated drill. The drill can be a bone material harvesting drill.

The adjustable stop can include a lock. The lock can be selectively actuable by a user to prevent operation of the adjustment mechanism. Hence, accidental changes to the depth of insertion once set using the adjustment mechanism can be reduced or avoided. The default state of the lock can be to prevent operation of the adjustment mechanism so that the lock has to be operated by a user to allow the adjustment mechanism to operate. The lock can act as an interlock for the adjustment mechanism. The lock and adjustment mechanism can be arranged as a dog clutch or similar mechanical clutch arrangement. The adjustment mechanism can include a tubular member. The tubular member can bear a first thread on an outer surface. The tubular member can have the stop surface at its proximal end. The adjustment mechanism can include a rotatable wheel bearing a second thread. The second thread can be on an inner surface of the rotatable wheel. The tubular member can be journaled within the rotatable wheel. The second thread can cooperate with the first thread. Hence, rotation of the wheel can drive the tubular member to change the position of the stop surface along the longitudinal axis.

The lock can include a locking ring. The locking ring can be translatable along the longitudinal axis to engage and disengage at least one spigot and socket arrangement provided by parts of the locking ring and rotatable wheel.

The kit of parts can further comprise a first instrument. The first instrument can have a working part toward a distal end and an instrument stop toward a proximal end. The first instrument can be dimensioned to be accepted within the central bore of the adjustable stop. The instrument stop can be arranged, positioned or located on the first instrument to co-operate with the stop surface to limit the extent of travel of the first instrument along the longitudinal axis.

The kit of parts can further comprise a second instrument. The second instrument can have a working part toward a distal end and an instrument stop toward a proximal end. The second instrument can be dimensioned to be accepted within the central bore of the adjustable stop. The instrument stop can be arranged, positioned or located to co-operate with the stop surface to limit the extent of travel of the second instrument along the longitudinal axis. The length of the first instrument from its working part to its instrument stop can be substantially the same as the length of the second instrument from its working part to its instrument stop. Hence, the working part of the second instrument will automatically be positioned at the correct position in the patient's bone when the second instrument stop abuts against the adjustable stop at a positioned defined in relation to the first instrument. The first instrument and the second instrument can be the same type of instrument or different types of instrument. The first instrument can be a drill. The second instrument can be a reamer or a cutter for forming a non-tubular cavity, such as a spherical cavity.

A further aspect of the invention provides a kit of parts for carrying out a surgical procedure, comprising at least one of, or a plurality of, or any combination of the following: a soft tissue protector; a guide drill; a cannulated drill; a guide tube; an adjustable stop; a bone harvesting drill; an access channel drill; a cavity reamer; a deformable implant; and an insertion instrument for inserting the deformable implant.

Various combinations of the parts of the kit of parts can provide various benefits disclosed herein in improving the accuracy and reliability of conducting a surgical procedure carried out inside the bone of a patient.

A further aspect of the invention provides an assembly of surgical instruments, comprising a guide tube and an adjustable stop. The guide tube can have a proximal end, a distal end and a guide tube bore extending therebetween along a guide tube longitudinal axis. The guide tube can have a releasable attachment mechanism at the proximal end. The adjustable stop can have a central bore for receiving an instrument extending along an adjustable stop longitudinal axis concentric to the guide tube longitudinal axis. The adjustable stop can also have a stop surface presented at a proximal end and an attachment formation distal to the stop surface and engaging the releasable attachment mechanism of the guide tube. The adjustable stop can include an adjustment mechanism operable by a user to vary the position of the stop surface along the longitudinal axis.

The assembly of surgical instruments can further comprise a soft tissue protector. The soft tissue protector can be in the form of a sheath or sleeve. The soft tissue protector can have a proximal end and a distal end and a soft tissue protector bore extending

therebetween along a soft tissue protector longitudinal axis concentric to the guide tube longitudinal axis. The distal part of the guide tube can be received concentrically within the soft tissue protector bore. The assembly of surgical instruments can further comprise a first instrument having a working part toward a distal end and an instrument stop toward a proximal end. The first instrument can be accepted or located within the central bore of the adjustable stop. The instrument stop can be arranged, positioned or located on the instrument to co-operate with the stop surface to limit the extent of travel of the first instrument along the longitudinal axis.

An aspect of the invention can also provide a method for forming a cavity within a bone of a patient. The method can include one, or a plurality, or any combination of the following: exposing a surface of the bone via an incision in soft tissue; inserting a soft tissue protector in the incision, the soft tissue protector having a bore extending along a longitudinal axis and having a stop at a proximal end; inserting a guide drill into the bone via the bore; using a cannulated drill guided by the guide drill to drill through cortical bone; using a cannulated drill guided by the guide drill to harvest bone graft material; assembling a guide tube and adjustable stop into a surgical assembly and inserting at least part of the surgical assembly into the bore of the soft tissue protector; removing the guide drill; inserting a drill into the surgical assembly and using the drill to create an access tunnel wherein the depth of insertion of the drill is limited by the adjustable stop; and inserting a cavity cutter into the surgical assembly and using a cavity cutter to create a cavity wherein the depth of insertion of the cavity cutter is limited by the adjustable stop; inserting a cavity cleaner into the surgical assembly and using the cavity cleaner to clean the cavity and wherein the depth of insertion of the cavity cleaner is limited by the adjustable stop; and inserting an insertion tool bearing a deformable implant into the surgical assembly and deploying the deformable implant in the cavity and wherein the depth of insertion of the insertion tool is limited by the adjustable stop.

The method for forming a cavity may be considered an aspect of the invention only in those countries in which such methods are patentable. An embodiment of the invention will now be described in detail, and by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a cross sectional view in the medial-lateral plane of the proximal part of the femur illustrating the positions of an implant cavity and access tunnel;

Figure 2 shows a perspective view of a soft tissue protector; Figure 3 shows a side elevation of the soft tissue protector shown in Figure 2;

Figure 4 shows a longitudinal cross-sectional view of the soft tissue protector shown in Figures 2 and 3;

Figure 5 shows an exploded perspective view of a guide tube;

Figure 6 shows a side elevation of the guide tube shown in Figure 5 in an assembled state;

Figure 7 shows a longitudinal cross-sectional view of the guide tube shown in Figures 5 and 6;

Figure 8 shows a perspective view of the guide tube shown in Figures 5 to 7; Figure 9 shows a surgical instrument assembly including the soft tissue protector and guide tube shown in Figures 2 to 4 and 5 to 8;

Figure 10 shows a longitudinal cross-sectional view of the surgical instrument assembly shown in Figure 9;

Figure 11 shows an exploded perspective view of an adjustable stop;

Figure 12 shows a perspective view of the adjustable stop shown in Figure 1 1 in an assembled state;

Figure 13 shows a side elevation of the adjustable stop shown in Figure 12;

Figure 14 shows a longitudinal cross-sectional view of the adjustable stop shown in Figures 12 and 13;

Figure 15 shows a side elevation of an assembly of the guide tube and the adjustable stop;

Figure 16 shows a longitudinal cross-sectional view of the assembly shown in Figure 15;

Figure 17 shows a side elevation of a surgical instrument assembly of the assembly shown in Figure 15 and a drill;

Figure 18 shows a longitudinal cross-sectional view of the surgical instrument assembly shown in Figure 17;

Figure 19 shows a flow chart illustrating a surgical procedure according to an aspect of the invention and in which a kit of parts according to an aspect of the invention can be used;

Figure 20 shows a partial cross sectional view of a proximal part of the femur and surgical instruments being used during a guide drilling step of the surgical procedure illustrated in Figure 19; Figure 21 shows surgical instruments being used during an access drilling step of the surgical procedure illustrated in Figure 19;

Figure 22 shows surgical instruments during a depth stop mounting step of the surgical procedure illustrated in Figure 19; and

Figure 23 shows surgical instruments being used during an access cavity drilling step of the surgical procedure illustrated in Figure 19.

Similar items in different Figures share common reference signs unless indicated otherwise.

The present invention will be described in the context of a surgical procedure for treating avascular necrosis of the femoral head. However, it will be appreciated that the invention is not limited to this particular application. Rather, the invention can be applied to any surgical procedure in which it is desired to carefully control the depth of insertion of various instruments into the patient.

Figure 1 shows a cross sectional view through the proximal part of a femur 100, and in particular including the femoral head 102. The cross section is generally in the medial- lateral plane. As illustrated in Figure 1, a portion of damaged bone tissue 104, such as a necrotic lesion, exists within the femoral head. Otherwise, the femoral head consists of healthy bone.

It is desired to remove as much of the necrotic lesion 104 as possible by forming a cavity into which a deformable support structure will be implanted and bone graft material deposited in order to encourage replacement bone growth. As illustrated in Figure 1, the spherical cavity 106 to receive the support structure implant should be positioned to overlap as much of the necrotic lesion as possible while ensuring that the majority of the implant is surrounded by healthy bone. An access tunnel 108 has to be formed through the femur, from the lateral side 110 and preferably having its entrance port within the ephysis of the proximal part of the femur. It is important to consider the position of the access tunnel during pre-operative planning as it may be necessary to increase the size of the implant used to ensure that the access tunnel follows a path that does not significantly weaken the femoral neck. A suitable deformable support structure and insertion instrument are described in International patent application number PCT/GB2010/050337 (publication number WO 2010/097636) which is incorporated herein by reference in its entirely for purposes.

The present invention focuses on the instrumentation used to create the access tunnel 108 and in particular to help ensure that the cavity 106 is created at the correct "depth" within the bone. Ideally, the implant should be adjacent to the inner surface of the subchondral bone in the load bearing area. This will typically be 5mm from the bone cartilage boundary.

With reference to Figure 2 there is shown a perspective view of a soft tissue protector 200. Figure 3 shows a side view of the soft tissue protector 200 and Figure 4 a cross sectional view along line A- A'. The soft tissue protector 200 is made from a radiolucent material in order to allow accurate fluoroscopic navigation of a reference drill. The entry position 112 and angular alignment in the anterior-posterior and medial-lateral planes are assessed fluoroscopically prior to starting drilling with the reference drill as described in greater detail below. The soft tissue protector can be made from, for example, titanium. The soft tissue protector 200 provides a sheath or outer sleeve and has a generally tubular construction with a generally circular transverse form and defines a circular bore 202 extending along a central longitudinal axis. The soft tissue protector 200 has a distal end 204 and a proximal end 206. A chamfered surface 208 extends around the periphery of the distal end 204. The proximal end 206 includes a pair of ribs 210, 212 defining a recess 214 therebetween for receiving a fastener of a handle as will be described in greater detail below.

A proximal entry 216 to the bore 202 includes a chamfered surface 218 to guide entry of other instrumentation into the bore 202. The body of the soft tissue protector 200 includes a distal portion 220, an intermediate portion 222 and a proximal portion 224. The distal and proximal portions 220, 224 are each in the form of a generally right circular cylinder with the proximal portion 224 having a greater diameter. Intermediate portion 222 provides a smooth taper between the distal and proximal portions as best seen in Figure 4. Figure 5 shows a perspective exploded view of a guide instrument 230. Figure 6 shows a side view. Figure 7 is a cross sectional view along line B-B' and Figure 8 a perspective assembled view of the guide tube 230. In use, guide tube 230 is inserted within the bore 5 202 of the soft tissue protector 200 and is suitably dimensioned for snug engagement therein as illustrated in later Figures below.

Guide tube 230 has a main body 232 having a generally tubular form, a distal end 234 of the guide tube has a serrated formation 236. The serrated end formation 236 enables the0 guide tube to cut into the bone in conjunction with a harvest drill as described in greater detail below. The harvest drill cuts slightly small to ensure a press-fit on the outer- diameter of the guide tube. The end portion 235 of the distal end (extending form the serrated end formation 236 to line 237) has an outer diameter slightly less than the outer diameter of the remainder of the distal tubular portion 242 to facilitate engagement of the end portion 235 into the patient's bone. Put another way, line 237 corresponds to a step or lip of size approximately 50μηι between parts 235 and 242. Hence, the diameter of part 235 is approximately ΙΟΟμηι less than that of part 242. The size of the step can be less, for example about at least 25μπι or greater, for example about 75μπι or up to about 1 ΟΟμηι. The lesser diameter of the end portion 235 provides an engineered press fit in the hole drilled in the patient's bone. The step 237 can also help to provide reliable seating of the distal end 234 in the hole in the patient's bone cut by the harvest drill.

A proximal end 238 includes a releasable attachment mechanism generally in the form of a bayonet coupling.

Similarly the guide tube 230 has a distal tubular portion 242 and a proximal tubular portion 244 connected by an intermediate tapered portion 244. The distal tubular portion 242 has a lesser diameter than the proximal tubular portion 244. Towards the proximal end 238, a shoulder extends from proximal tubular portion 244 and defines an annular portion extending around the longitudinal axis. A generally cylindrical wall 250 extends therefrom and defines an opposed pair of oblong apertures 252, 254 and an opposed pair of "C" shaped, or re-entrant, recesses for receiving a pair of co-operating pins of a bayonet fitting. The recessed apertures are disposed on opposed sides of wall 250 and at an angle approximately 90° to the oblong apertures 252, 254. A string 260 is arranged concentrically to the longitudinal axis of the guide tube and surrounds wall 250. A milled ring 262 includes a pair of pegs 264, 266 disposed in apertures on opposed sides of the ring. Pegs 266, 264 are arranged to engage in oblong apertures 252, 250 as best illustrated in Figure 7. Spring 260 acts to urge ring 262 in the proximal direction, as 5 illustrated in Figure 7. Pegs 266, 264 retain ring 262 and the longitudinal extension of oblong apertures, 252, 250 to permit some travel of ring 262 in the distal direction.

A proximal most, upper surface 270 of ring 262 bears a first and second anti-rotation formation 272, 274 in the form of a proud extension or tooth. Anti rotation formations 10 272, 274 are disposed generally diametrically opposite and aligned with the pegs 266, 264 of ring 262.

Figure 9 shows a side view of a surgical instrument assembly 280 comprising soft tissue protector 200, guide tube 230 and a canulated drill 290. As mentioned above, soft tissue

15 protector 200 includes a clamp 300 located in and extending around channel 214. An arm 302 extends from clamp 300 to a handle 304 by which the assembly 280 can be held by a surgeon in use. Figure 10 shows a partial cross sectional view along lines C-C of the surgical instrument 280. Drill 290 includes a canulated drill bit 292 formed for the harvesting of bone graft material. Although not forming part of the instrument assembly, 0 a guide drill 294 providing canulated guidance to the assembly 280 is illustrated in

Figures 9 and 10.

Drill 290 further comprises a bearing 294 through which an axle attached to drill bit 292 passes and terminating in a proximal connector 296 for attachment to a power tool. A 5 distal face of bearing 294 has a body 298 extending therefrom bearing a pair of opposed pegs, e.g. peg 300, for cooperating with bayonet attachment fitting recesses 256, 258 to complete the bayonet attachment mechanism.

Bearing 294 also includes a pair of opposed notches or recesses, e.g. 302, disposed to0 cooperate with anti-rotation teeth 272, 274 on ring 262.

Hence, assembly 280 can be assembled by sliding the engaging guide 230 within soft tissue protector bore 202 and then inserting drill bit 292 within guide tube 230 and operating bayonet attachment mechanism to releasably secure the drill to the guide tube. The notch 302 in drill bearing 294 cooperates with the anti-rotation teeth 272, 274 to prevent relative rotation of bearing 294 and guide tube 230 when power is applied to coupling 296.

5 The use of instrument assembly 280 will be described in greater detail below.

Figure 11 shows an exploded perspective view of an adjustable stop 310 usable with the guide tube 230. Figure 12 shows a perspective view of the adjustable stop 310 in an assembled state. Figure 13 shows a side elevation of the adjustable stop 310 and Figure

10 14 shows a cross sectional view of the adjustable stop along the line D-D'. Adjustable stop 310 includes a central tubular portion 312 defining a central bore 314 extending along a longitudinal axis thereof. An outer surface of tubular portion 312 bears an external thread 316 extending toward a distal end 318. A proximal end 320 includes a flange 322 extending around the periphery of the tube 312. A proximal most surface 324

15 of which provides a stop surface as will be described in greater detail below.

Adjustable stop 310 also includes a main body 330 defining a circular channel extending therethrough and dimensioned to receive tubular body 312. A generally tubular portion 332 extends from a distal side of body 330 and bears a pair of mutually opposed pegs 0 334, 336 providing part of the bayonet attachment mechanism to guide tube 230. Body 330 also includes a pair of mutually opposed notches, e.g. 338, arranged to cooperate with anti-rotation formations 272, 274 of guide tube 230.

Body 330 defines a slot 340 substantially transverse to the longitudinal axis of the 5 instrument for receiving an adjustment wheel 342. Adjustment wheel 342 has a generally annular construction and comprises knurled portions extending around the periphery of its outer surface. An inner wall 346 defines a circular aperture for receiving the thread 316 of tubular member 312. The surface of wall 346 bears a thread 348 for cooperatively engaging threaded portion 316. The pitch of threads 348 and 316 are such that a rotation0 of adjustment wheel 342 through 360° will translate tubular body by 3mm along its longitudinal axis. The length of tubular part 312 and pitch of the threads are arranged to provide a range of adjustment of the stop of between about 60mm and 125mm. That is the position of the stop can be adjusted by at least about 60mm and at most about 125mm. Sufficient stop position adjustment is needed to accommodate a range of patient soft tissue depths and too large a stop position adjustment should be avoided so as to ensure that the instrumentation maintains reliable operation and use.

Adjustment wheel 342 can also include a plurality of equi-angularly positioned indicia, e.g. indicium 343, on its outer surface which are arranged provide a visual indication of the degree of adjustment of the adjustable stop. For example, in the presently described embodiment, three indicia can be provided at 120° spacing so that each indicium corresponds to 1mm of travel of the tubular part 312 and hence stop surface 324. A side wall 350 of wheel 342 includes a plurality of circular apertures disposed substantially equi-angularly thereabout. The eight apertures inside the wall 350 form part of a locking mechanism as will be described in greater detail below.

A proximal side of body 330 bears a substantially cylindrical wall 360 extending from an annular plate section 362 bearing four elongate apertures 264. A circular spring 266 is located about circular wall 360.

The adjustable stop also includes a locking ring 370 having a generally annular shape including a knurled ring portion 372 with a wall 374 extending therefrom and bearing four pegs, e.g. 376. An annular retention plate 378 is also provided within locking ring 372 in order to retain spring 366 therein in a compressed state. As best illustrated in Figure 14, spring 366 acts against locking ring 378 to urge pegs 376 through apertures 364 into four of the eight apertures in adjustment ring 342. Hence, as illustrated in Figure 14, rotation of adjustment ring 242 is prevented. In order to rotate ring 342 locking ring 370 is pulled in a proximal direction against the action of spring 366 to release pegs 376 from the apertures in the adjustment ring 342. Adjustment ring 342 can then be rotated to drive tubular member 312 in the proximal or distal direction. Once the tubular member 312 has been translated a sufficient distance relative to the body 330, locking ring 370 can be released and spring 366 acts to draw pegs 376 through apertures 364 into apertures in the adjustment ring to lock the adjustment ring in place and prevent further rotation thereof and translation of the tubular guide member 312.

Similarly to assembly 280, adjustable stop 310 can be releasably attached to the bayonet fitting of the guide tube 230 by engaging pegs 334, 336 with the recess slots 258, 256 and notch 338 with anti-rotation teeth 272. This prevents relative rotation of the adjustable stop and guide tube once assembled.

Figure 15 shows a side view of a surgical instrument assembly 400 comprising the guide 5 tube 230 and adjustable stop 310. Figure 16 shows a cross sectional view along line E-E' of Figure 15 of the surgical instrument assembly 400. As described above, adjustable stop 310 is operable to vary the separation between stop surface 324 and ring 248 so as to control the depth of insertion of ancillary instrumentation into the bore defined by the assembly. As described above, a user can pull on locking ring 370 to release pegs 376 10 from apertures in adjustment wheel 342. This frees adjustment wheel 342. Rotation of adjustment wheel 342 drives the tubular member 316 in the distal or proximal directions thereby changing the separation between guide surface 324 and ring 248.

Figurer 17 shows a further surgical instrument assembly 410 comprising guide tube and 15 adjustable stop assembly 400 and a drill instrument 420. Figure 18 shows a cross section through Figure 17 along line F-F'. Drill 420 includes a drill bit 422. The drill 420 is a tunnel drill and drill bit 422 is configured to complete drilling of the access tunnel 108. A proximal end of drill 420 includes a coupling 424 for attaching a power drive. A ring 426 extends around drill 420 and can abut against the proximal end 320 of tubular member 20 316 to prevent further travel of drill bit 422 through the guide structure. Hence, once the insertion depth has been set by the adjustable stop, the depth of insertion of drill 420 can be controlled by abutments against stop surface 324.

With reference to Figure 19, there is shown a flowchart illustrating a surgical method 450 25 in which the instrumentation of the invention can be used. It could be understood that the description of the method illustrated in Figure 19 will include both acts carried out on the patient and also acts carried out on the instrumentation. The description of Figure 19 therefore includes both surgical method steps but also method of operation of the instrumentation steps which are not limited to surgery. Hence, an aspect of the invention 0 can also provide a method of operation of the surgical instrumentation which does not include any surgical steps. In countries where surgical methods are patentable, an aspect of the invention can also provide a surgical method in which the instrumentation is used. As discussed above with reference to Figure 1, the aim of the surgical method 450 is to remove necrotic bone from beneath the articular surface of the femoral head, and replace it with bone graft supported by an implant support structure. To maximise its

effectiveness, the implant should be adjacent to the inner surface of the sub-chondral bone in the load bearing area. This will typically be approximately 5 mm from the bone- cartilage boundary. Implant positioning objectives include positioning of the implant adjacent to sub-chondral bone, maximising the necrotic bone removal, minimizing healthy bone removal, avoiding impingement in the femoral neck and starting the access tunnel in metaphyseal bone. It is not necessary to remove the entire necrotic region. However, the implant should be surrounded by healthy bone around the majority of its circumference, as illustrated in Figure 1. A correctly selected implant will maximise region removal while minimising healthy bone removal. The surgeon should consider the position of the access tunnel 108 during pre-operative planning as it may be necessary to increase the size of the implant used to ensure that the access tunnel follows a path that does not weaken the femoral neck.

In order to ream cavity 106, a plurality of sequentially sized cavity cutters are used to create surgical cavities increasing size with their tangents aligned at the proximal most point 105. This is to prevent further migration of the spherical cavity towards the bone- cartilage boundary and maintain a minimal gap of at least approximately 5 mm between the cavity and bone-cartilage boundary. A benefit of this method is that the minimum distance between the sub-chondral bone and the edge of the cavity is kept relatively constant. Preoperative planning of the spherical cavity 106 position, access tunnel 108 position and entry point 112 can use accurately scaled anterior-posterior and medial-lateral X-rays. X- ray templates can be used to define the path of the access tunnel and position of the spherical cavity. The patient can be placed supine on a traction table. Prior to draping, a good fluoroscopic view of the femoral head should be ensured in both the anterior-posterior and medial- lateral views. The surgical procedure 450 begins at step 452 and an initial incision of length necessary to gain sufficient exposure is made at step 452. The incision is position in line with the femur, centred about the proximal third of the lesser trochanter. Subcutaneous tissue is divided sharply in line with this incision until the lateral aspect of the metaphysis are exposed. Once the metaphysis is exposed, at step 454, the soft tissue protector 200 is inserted with its distal end 208 against the patient's bone. The insertion of the soft tissue protection should ensure that a clear path to the lateral cortex is obtained. The soft tissue protector 200 controls the depth to which a starter drill and guide tube cut. A reference drill is used to define the path of the access tunnel 108 and thus the position of the implant. Both the anterior-posterior and medial-lateral angles should be checked prior to progressing the drill. As illustrated in Figure 20, at step 456, a reference drill guide 480 is inserted into the proximal end of the soft tissue protector 200. The reference drill 482 is progressed using a power tool to a point medial to the neck-head junction and should be stopped at least 30 mm from the articular surface. This is to safeguard against the risk of puncturing the articular surface should the reference drill become jammed subsequently. Fluoroscopic images and fluoroscope templates can be used to guide the positioning and progress of the reference drill. The drill guide 480 is removed and at step 458 a starter drill is used to cut through to the cortex creating a hole through the cortex through which a harvesting drill can pass. This reduces the risk of chipping the cortex. Step 458 is illustrated in Figure 21 in which a cannulated starter drill 490 is passed over the reference drill 482 and into the bore of the soft tissue protector 200. A power tool is attached to the starter drill and the starter drill is progressed until a shoulder 492 reaches and abuts against a proximal most part 212 of the soft tissue protector to limit insertion of the starter drill. It is important to stop cutting as soon as progress of the drill is impeded to avoid the potential for damaging the surrounding bone. Hence, as will be appreciated, the length of the starter drill from the chip of the drill bit to the shoulder 492 is selected to be greater than the length of the soft tissue protector 200 and extends subsequently from the distal end thereof in order to limit the degree of cutting once through the cortex.

At step 460, bone graft is harvested from the interior of the femur using the instrument assembly 280 illustrated in Figures 9 and 10. Firstly, the bone harvesting drill is inserted in the guide tube 230 and loosely attached thereto by the bayonet mechanism by twisting ring 262 to accept the bayonet pins 300 on the harvesting drill 292. The harvesting drill is pushed into the guide tube 230 until the locking ring 262 disengages. The drill is then rotated clockwise until the anti-rotation 272, 274 locates in the notches 302, of the harvesting drill bearing. As illustrated in Figures 9 and 10, the harvesting drill is cannulated and can be inserted over guide drill 294 and into the bore of soft tissue protector 200. At step 460, a power tool is used to power the harvesting drill to harvest bone graft from the access tunnel. The guide tube 230 provides a stable datum for the subsequent steps. The depth of the cut created by the bone graft harvesting drill is limited by the soft tissue protector 200. The drill is driven forward until the shoulder 248 on the guide tube contacts the proximal stop 212 of the soft tissue protector 200. Once the final depth is reached, the harvesting drill can be disengaged from the guide tube 230 by retracting the locking ring 262, rotating anti-clockwise until the bayonet fitting

disengages and pulling firmly. A T-handle can be used to facilitate easy removal of the harvesting drill. Care should be taken when removing the drill to ensure that the maximum possible bone graft is recovered. The bone graft should be retained within the sterile field so that it can be used to fill the support structure implant.

At step 462, the adjustable depth stop 310 is inserted in the guide tube 230 and attached thereto using the bayonet fitting. The length of the depth stop can be altered by pulling locking ring 370 in the proximal direction and rotating adjustment ring 342 to drive the proximal end 320 in the proximal or distal direction. Once the depth has been corrected adjusted, the locking ring 370 is released and under the action of spring 366, pegs 376 engage with the apertures in the locking ring to prevent any change in depth by accident or rotation of the adjustment ring 342. The instruments used in the subsequent steps all have the same length that are designed to interact with the adjustable depth stop so as to control their depth of insertion into the patient's bone. Figure 22 shows the assembly of the guide tube and adjustable stop 400 inserted in the soft tissue protector 200. The reference drill 482 is removed at step 464 and then at step 466 the tunnel drill 422 is used to complete the access tunnel up to the distal most point 105 of the cavity. Hence, surgical instrument assembly 410 as illustrated in Figures 17 and 18 is used to complete the access tunnel, as illustrated in Figure 23. The tunnel drill 422 is used to complete the access tunnel and cover a more viable bone graft. The tunnel drill is operated through the adjustable depth stop and guide tube assembly 400. To ensure accurate control of cutting depth, the adjustable depth stop is first fully extended before the tunnel drill is used. The tunnel drill is progressed until the shoulder 426 engages the stop part 322 of the adjustable stop. The adjustable stop is operated to progressively be retracted until the correct final depth of drilling is reached. The adjustment screw 342 bears three marks, e.g. indicium 343, and rotation between adjacent marks changes the position of the drill by 1 mm. The marks are indicative only and the position is checked using a fiuoroscope. The tunnel drill is driven forward until the position determined during preoperative planning has been reached. A fiuoroscope template is used to determine when the optimum position has been reached.

Removal of the tunnel drill should be careful in order to ensure that the maximum possible volume of bone graft is recovered. Any recovered bone graft should be retained within the scar field so that it can be used to fill the support structure implant. However, any necrotic bone should be separated and discarded.

As described above, the adjustable depth stop is used to control the depth of insertion of the tunnel drill until it reaches the maximally distal point 105 defining the end of the intended spherical cavity 106. Hence at step 468, a cavity cutter can be inserted into the adjustable stop and the adjustable stop acts to control the depth of insertion of the cavity cutter to ensure that the clip of the cavity cutter is located at the correct position 105. The length of the cavity cutter is the same as the length of the tunnel drill (i.e. between the distal most part of its operating tip and its stop flange). Hence the cutting depth set by the adjustable stop in the previous step is not altered. Fluoroscopy can be used to check that the tip of the cavity cutter is at the end of the tunnel and that the shoulder is checking the usual stop. The cavity cutter can be used to create the spherical cavity that is up to 1 mm smaller in diameter compared to the diameter of the implantable support structure. This interference stabilises the implant when ensuring that it deploys completely within the cavity. Hence at step 462, cavity cutters of increasing size are sequentially used in order to Create the spherical cavity. Using sequentially increasing sizes of cavity cutter helps to reduce the stress on the surrounding bone and allows safe intra-operative adjustment of the implant size to be used. After the cavity has been created, at step 470, a cavity cleaner can be inserted in place of the cavity cutter via the adjustable support and operated in order to clean and remove debris from the cavity. After the cavity has been cleaned, at step 472, the implant can be inserted via the adjustable stop. As described above, WO 2010/097636 describes an assembly for deploying a support structure implant within a bone cavity and instrumentation for doing so. The disclosure of this document is incorporated herein by reference in its entirety for all purposes. As described therein, the support structure implant can be deformed to have a narrower width such that it can be inserted through access tunnel in to the spherical cavity and then allowed to regain its deployed state within the spherical cavity. After the implant has been inserted at step 472, bone graft material can be introduced into the cavity and also backfilled into the access tunnel in order to complete the procedure. WO 2008/099187 and WO 2010/013027 describe instruments for forming cavities in bone. The disclosure of these documents is incorporated herein by reference in their entirety for all purposes. Any modifications to the cavity forming instruments described in these documents in order to operate with the adjustable stop assembly described herein will be apparent to a person of ordinary skill in the art from the teaching above.

Hence, as described above, the combination of the guide tube and adjustable stop allows multiple different instruments to be used in order to create the cavity. In particular, the adjustable stop can be used to carefully control the depth of insertion of a drill forming the cavity. The position of the adjustable stop can be fixed once the required cavity depth has been reached. Thereafter, by using instruments with the same length, between their working tip and a proximal stop, means that the instrumentation is automatically controlled or inserted to its correct depth by the action of the adjustable stop on the instrumentation stop. At some stages during the procedure, the stop end face 324 effectively acts as a bushing as it engages rotating parts of other instrumentation, e.g. drills, while also acting as a depth control mechanism. The adjustable stop is used accurately to control the depth of insertion of various instruments, and that depth needs to be adjustable. It is therefore important that the depth can be reliably fixed over a range of values. However, when end face 324 is acting as a bushing for a rotating instrument, some rotation may be imparted to the tube 312. The tube 312 position is adjustable using a thread and rotation therefore it is important to ensure that any rotation imparted to the tube does not result in the tube progressing along the longitudinal axis and therefore changing the depth of insertion. Otherwise, for example, a drill or cutter could cut into bone which should not be removed. It is therefore important that there is a locking mechanism for the adjustment mechanism and also that the locking mechanism can robustly prevent actuation of the adjustment mechanism by any rotational forces imparted by the stop face 324 acting as a bushing. In the described embodiment this is achieved by the locking mechanism acting like a dog clutch, rather than a friction clutch, in which multiple members 376, which are mechanically constrained on a non-rotatable part, are selectably engagable with multiple apertures in the rotatable part (adjustment ring 342). The locking mechanism acts as an interlock of the adjustment mechanism to prevent its operation unless the locking mechanism is de-activated or released. Hence, actuation of the adjustment mechanism which is based on rotation is precluded even when rotational forces are applied .

Further, the releasable attachment mechanism provided on the guide tube allows multiple different types of instrumentation to be securely attached to the guide tube. Further, the anti-rotation mechanism allows instrumentation having rotational parts to be used while preventing relative rotation of the instrumentation themselves.

Various modifications and variations to the instrumentation described herein will be apparent to a person of ordinary skill in the art from the teaching above.

Claims

CLAIMS:

1. A kit of surgical instruments for use in preparing a cavity within a bone of a patient, the kit comprising:

a guide tube having a proximal end, a distal end, a guide tube bore extending therebetween along a guide tube longitudinal axis and a releasable attachment mechanism at the proximal end; and

an adjustable stop having a central bore for receiving an instrument extending along an adjustable stop longitudinal axis, a stop surface presented at a proximal end and an attachment formation distal to the stop surface for engaging the releasable attachment mechanism of the guide tube, and wherein the adjustable stop includes an adjustment mechanism operable by a user to vary the position of the stop surface along the longitudinal axis relative to the guide tube and a lock selectively actable by a user to allow operation of the adjustment mechanism.

2. The kit of parts of claim 1 and further comprising:

a soft tissue protector having a proximal end and a distal end and a soft tissue protector bore extending therebetween along a soft tissue protector longitudinal axis, and wherein the guide tube is dimensioned to be received concentrically within the soft tissue protector bore.

3. The kit of parts as claimed in claim 2, wherein the soft tissue protector includes a handle extending laterally from the soft tissue protector so as not to obscure access to the soft tissue protector bore

4. The kit of parts as claimed in claim 2 or 3, wherein the guide tube has a stop formation and the soft tissue protector has a stop surface at the proximal end and wherein the stop formation and stop surface can co-operate to limit the extent of travel of the guide tube within the soft tissue protector bore.

5. The kit of parts as claimed in claim 4, wherein the guide tube is longer than the soft tissue protector.

6. The kit of parts as claimed in any preceding claim, wherein the guide tube includes a first part of an anti-rotation mechanism and wherein the adjustable stop includes a second part of the anti-rotation mechanism and wherein the first and second parts co-operate to prevent relative rotation between the adjustable stop and the guide tube about their longitudinal axes.

7. The kit of parts as claimed in claim 6 and further comprising:

an instrument including a second part of the anti-rotation mechanism and wherein the first and second parts co-operate to prevent relative rotation between a part of the instrument and the guide tube about the longitudinal axis.

8. The kit of parts as claimed in any preceding claim and further comprising:

an instrument including an attachment formation for engaging the releasable attachment mechanism of the guide tube.

9. The kit of parts as claimed in claim 7 or 8, wherein the instrument is a drill.

10. The kit of parts as claimed in any preceding claim, wherein the adjustable stop has a range of adjustment of from 60mm to 125mm.

11. The kit of parts as claimed in claim 1, wherein the adjustment mechanism includes a tubular member bearing a first thread on an outer surface and having the stop surface at its proximal end, and a rotatable wheel bearing a second thread on an inner surface and wherein the tubular member is journaled within the rotatable wheel and the second thread cooperates with the first thread.

12. The kit of parts as claimed in claim 1 or 11, wherein the lock includes a locking ring which is translatable along the longitudinal axis to engage and disengage at least one spigot and socket arrangement provided by parts of the locking ring and rotatable wheel.

13. The kit of parts as claimed in any preceding claim, and further comprising:

a first instrument having a working part toward a distal end and an instrument stop toward a proximal end, wherein the first instrument is dimensioned to be accepted within the central bore of the adjustable stop and wherein the instrument stop is arranged to co- operate with the stop surface to limit the extent of travel of the first instrument along the longitudinal axis.

14. The kit of parts as claimed in claim 13, and further comprising:

a second instrument having a working part toward a distal end and an instrument stop toward a proximal end, wherein the second instrument is dimensioned to be accepted within the central bore of the adjustable stop and wherein the instrument stop is arranged to co-operate with the stop surface to limit the extent of travel of the second instrument along the longitudinal axis, and wherein the length of the first instrument from its working part to its instrument stop is substantially the same as the length of the second instrument from its working part to its instrument stop.

15. The kit of parts as claimed in claim 14, wherein the first instrument and second instrument are different types of instrument.

16. The kit of parts as claimed in claim 13, 14 or 15, wherein the first instrument is a drill.

17. The kit of parts as claimed in any of claims 14 to 16, wherein the second instrument is a reamer for forming a spherical cavity.

18. A kit of parts for carrying out a surgical procedure, comprising:

a soft tissue protector;

a guide drill;

a cannulated drill;

a guide tube;

an adjustable stop;

a bone harvesting drill;

an access channel drill;

a cavity reamer;

a deformable implant; and

an insertion instrument for inserting the deformable implant.

19. An assembly of surgical instruments, comprising: a guide tube having a proximal end, a distal end, a guide tube bore extending therebetween along a guide tube longitudinal axis and a releasable attachment mechanism at the proximal end; and

an adjustable stop having a central bore for receiving an instrument extending 5 along an adjustable stop longitudinal axis concentric to the guide tube longitudinal axis, a stop surface presented at a proximal end and an attachment formation distal to the stop surface and engaging the releasable attachment mechanism of the guide tube, and wherein the adjustable stop includes an adjustment mechanism operable by a user to vary the position of the stop surface along the longitudinal axis relative to the guide tube.

10

20. An assembly of surgical instruments as claimed in claim 19, and further comprising:

a soft tissue protector having a proximal end and a distal end and a soft tissue protector bore extending therebetween along a soft tissue protector longitudinal axis 15 concentric to the guide tube longitudinal axis, and wherein a distal part of the guide tube is received concentrically within the soft tissue protector bore.

21. The assembly of surgical instruments as claimed in claim 20 or 21 and further comprising:

20 a first instrument having a working part toward a distal end and an instrument stop toward a proximal end, wherein the first instrument is accepted within the central bore of the adjustable stop and wherein the instrument stop is arranged to co-operate with the stop surface to limit the extent of travel of the first instrument along the longitudinal axis.

25 22. A method for forming a cavity within a bone of a patient, comprising:

exposing a surface of the bone via an incision in soft tissue;

inserting a soft tissue protector in the incision, the soft tissue protector having a bore extending along a longitudinal axis and having a stop at a proximal end;

inserting a guide drill into the bone via the bore;

30 using a cannulated drill guided by the guide drill to drill ^'through cortical bone;

using a cannulated drill guided by the guide drill to harvest bone graft material; assembling a guide tube and adjustable stop into a surgical assembly and inserting at least part of the surgical assembly into the bore of the soft tissue protector;

removing the guide drill; inserting a drill into the surgical assembly and using the drill to create an access tunnel wherein the depth of insertion of the drill is limited by the adjustable stop; and inserting a cavity cutter into the surgical assembly and using a cavity cutter to create a cavity wherein the depth of insertion of the cavity cutter is limited by the adjustable stop;

inserting a cavity cleaner into the surgical assembly and using the cavity cleaner to clean the cavity and wherein the depth of insertion of the cavity cleaner is limited by the adjustable stop; and

inserting an insertion tool bearing a deformable implant into the surgical assembly and deploying the deformable implant in the cavity and wherein the depth of insertion of the insertion tool is limited by the adjustable stop.