Patent Description:
All orthopaedic implants require a set of tools to enable installation of implant components. The set will comprise several trial fittings to establish the implant component sizes required for the patient, as well as a number of specific tools to facilitate the fixing of the implant in the patient's joint. The implant tool set will often be augmented in theatre by generic tools, readily found in orthopaedic surgical environments, such as impactors of various weights, osteotomes of various sizes, retractors of various types, K-wires and oscillating saws.

<CIT>) describes prosthetic wrist implants and a set of tools for installation of stem implants including a stem-shaped priming tool, a plurality of stem-shaped broaches and a liner exchange tool. <CIT>) describes an implant for the CMC joint. <CIT>) describes preparation of a sacroiliac joint for fusion. <CIT>) describes a femoral elevating tool. <CIT> (Hip Innovation Ttechnology) describes hip replacement equipment.

The invention is directed towards achieving improved efficiency in implant surgery.

The invention provides a set of tools as set out in claim <NUM>, and optional features for the set of tools and a kit are set out in the dependent claims <NUM>- <NUM>.

The invention will be more clearly understood from the following description thereof, given by way of example only, in which:.

One example of an implant which may be installed using the set of tools of the invention is shown in <FIG>. Referring to <FIG> an implant <NUM> has a distal part with an insert <NUM> in a stem <NUM>, and a proximal part <NUM>. In this case the implant <NUM> is for a mammalian first carpometacarpal joint for spacing a trapezium bone of the joint from a first metacarpal bone of the joint while allowing translational and rotational movement of the first metacarpal bone in relation to the trapezium bone. The distal part <NUM> is configured for intramedullary engagement with an end of the first metacarpal bone. The proximal part <NUM> has a curved saddle-shaped platform <NUM> with a proximal-facing surface <NUM> for sliding on or traversing the trapezium bone. An articulating coupling comprises a neck <NUM> bridging the saddle <NUM> to a ball <NUM>, as is known. This allows controlled articulation of the trapezium and first metacarpal bones.

The insert <NUM> may have a buffer interface feature, in this case a flange <NUM> with a contoured proximally-facing surface <NUM>. Distally of this surface there is a shoulder <NUM> which acts as a key for engaging the insert <NUM> in the stem <NUM> and preventing rotation of the insert in the stem, and surrounding a socket <NUM> with a rim <NUM> to receive the articulated coupler ball <NUM>. There is snap-fit engagement of the ball <NUM> (see especially <FIG>) in the socket <NUM>, behind the socket's rim <NUM>, to enable the assembly of an articulating hemiarthroplasty intra-operatively, and it may also prevent disassembly of the device in vivo. The socket can be central or offset in any direction or angle as needed.

Further distally, the insert <NUM> comprises an annular locking rim <NUM> for snap-fitting into a corresponding groove of the stem <NUM> recess <NUM> which accommodates the insert <NUM>. Engagement of the insert <NUM> into the stem <NUM> is effective due to the resilience of the insert material and the fact that there is comprehensive surface-to-surface contact in a snap-fitting manner between the rim <NUM> and its corresponding engagement surface within the stem <NUM>. The insert is keyed by the shoulder <NUM> to prevent rotation and potential consequent back side wear.

Referring to <FIG> there is illustrated a set of tools for use in installing an implant such as the implant of <FIG>. The set of tools in this example comprises:.

Referring to <FIG> the primer <NUM> has a cutting head <NUM> and facilitates the first incision into the metacarpal and eliminates the need for an awl or similar by the surgeon prior to deployment of the first broach <NUM>. In addition, the geometry of the cutting head <NUM> of the primer <NUM> is modelled on the geometry of the smallest broach in the tooling set, broach <NUM>. The primer <NUM> has less bulk, is shorter, has more cutting teeth <NUM> per unit length and has a much sharper point <NUM>, but has the requisite curved volar, flat dorsal geometry of the broaches and the implant. The primer distal tip does not have a non-toothed bone marrow compacting distal end which is a feature of the broaches. In this case the head <NUM> has <NUM> cutting teeth <NUM>, and in general it is preferred that there are in the range of <NUM> to <NUM>, and more preferably <NUM> to <NUM> teeth.

The net effect is that the primer <NUM> penetrates much farther than an awl or similar, can be used to more precisely locate the initial incision, and most significantly, reduces the effort required with the first broach <NUM>. This is a particularly significant benefit for surgeons with low or reduced hand strength.

The broaches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (referred to as broaches A to E) are a geometrical match for the implant stems <NUM>. Therefore, the end user can utilize the broaches as trial stems. When the surgeon has completed broaching the metacarpal cavity, there is no need for a separate trial stem to be put in place to assess stem fit as the broach itself will have provided this clinical information.

In addition to the tools described, a trial implant head <NUM> (<FIG>) may also be used during the procedure, as described in more detail below.

To install the implant, the primer <NUM> is used to make the first incision into the metacarpal. By virtue of its cutting teeth density and the fact that the primer geometry closely mimics that of the smallest broach (size A, <NUM>), the primer also aids the surgeon in creating accurate location and orientation of broaches, and hence the stem implant within the metacarpal. One or more of the broaches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are then used to broach the metacarpal cavity. Broaches are used in order of increasing size. Thus, size A (<NUM>) follows after use of the primer. For any given metacarpal, based on surgeon feel when broaching and/or using X-ray images, the surgeon decides whether successive broach sizes are required. After broaching, the stem insertion tool <NUM> is used to insert the stem part <NUM> of the implant into the metacarpal cavity until the metacarpal stem implant <NUM> is located flush or just proud of the resected metacarpal. This is facilitated by the close relationship of broaches to stem implants, and the surgeon being able to gauge where the base of the stem will end up in relation to the resected metacarpal based on the position of the final broach he or she uses.

Referring to <FIG> and <FIG>, the first dual purpose tool <NUM> has both rasp <NUM> and broach <NUM> features. The rasp <NUM> on the concave side may be used to sculpt the trapezium bone to the exact radius of the implant head <NUM>. The convex side of the tool <NUM> carries broach-like teeth <NUM> which may be used to remove incidental osteophytes or other protuberances encountered in the course of sculpting the trapezium.

As noted above the head <NUM> of this tool has dual purpose capability. It has a shaft <NUM> which is tapered, or otherwise reduced in diameter for ease of access to the small joint.

The concave side <NUM> of the head <NUM> has rasp construction and is designed for sculpting the trapezium to the shape of the implant head. The convex side <NUM> has broach construction for removal of osteophytes and is designed to cut on the pull stroke rather than the push.

Other uses include maxillofacial surgery where bone remodeling is required but a surgeon does not want to have to remove and replace tools in succession. For example, the first dual purpose tool <NUM> may be inserted into a body cavity and used for rasping function, left in situ but rotated <NUM> degrees, and then be used for broaching or bone remodeling functions.

The tool <NUM> may be used to modify the geometry of any bone's external or internal surface depending on the geometry of the bone, the cutting surfaces, and the distal end of the tool, with the novel dual function head facilitating ease of use.

The distal end of the tool <NUM> may be circular, square, flat, or toroidal in shape in accordance with the desired anatomical geometry to be produced by its use.

The distal cross-section above and below the center-line may be of one geometry on one side and another on the other side i.e. toroidal on one side and flat on the other.

Referring to <FIG>, the second dual purpose tool <NUM> is used as a metacarpal elevator to move tissue aside and to present the metacarpal to the surgeon for resection. It comprises a stem <NUM> and a head <NUM> with a keyhole feature <NUM>. The keyhole feature <NUM> is at the distal end of the head <NUM> of the second dual purpose tool <NUM> and may be used to separate the trial head (<NUM>) from the implant stem as illustrated in <FIG>.

This tool <NUM> may for example serve as a metacarpal elevator and be used to present the metacarpal to the surgeon for resection. The shaft <NUM> is flat and is angled with respect to the handle <NUM> and provides optimum access to both the metacarpal and a fulcrum point location. The head <NUM> is curved to match the curvature of the metacarpal bone.

In addition, a keyhole slot <NUM> at the distal end of the head <NUM> matches the radius of the neck of the implant stem <NUM> and can be used to lever out a trial head <NUM> from the liner <NUM> as illustrated in <FIG>, when the surgeon is ready to fit the implant head <NUM>. In general, the head of the tool <NUM> is a claw with a variety of uses as a holder or a gripping lever for remoting an item.

Other uses for the second dual purpose tool <NUM> include: a) manipulation of any small bone such as the second through fifth metacarpals during surgery; b) removal of plates in small j oint surgery by using the tool to leverage the plate off the bone; c) removal of plates with screws in situ where the keyhole can sit around a nail or screw while the plate is leveraged away from the bone; d) removal of screws out of bones where the slot/keyhole <NUM> is used to leverage screws out of bone which may be of poor quality but where the screw has some fixation.

The internal features of a head <NUM> of the stem insertion tool <NUM> captures both the outline and the depth of the liner flange <NUM> and these features permit the distal portion of the tool head to bottom out on the base of the metacarpal stem implant <NUM>. The distal head <NUM> of the tool <NUM> sits on the base of the stem <NUM>. As the surgeon manipulates the stem <NUM> into the bone, the liner <NUM> will not be damaged because the forces are transmitted from the metal head of the stem insertion tool <NUM> to the metal base of the stem <NUM>, should an impactor be used in conjunction with the stem insertion tool <NUM>.

The profile of the distal portion of the tool head <NUM> exceeds that of the base of the metacarpal stem implant <NUM>. When the metacarpal stem implant <NUM> has been located flush or just proud of the resected metacarpal, these design features then ensure that the liner <NUM> cannot be inserted below flush in the bone.

The bullnose at the distal end of the stem insertion tool <NUM> is less than the internal diameter of the liner <NUM> at the snap fit location, and because the stem insertion tool <NUM> closely envelops the exterior of the liner <NUM>, no damage occurs to the snap fit of the liner <NUM> with the ball of the head <NUM>.

If necessary, the stem <NUM> may be removed from the metacarpal cavity using the stem exchange tool <NUM>. If the liner <NUM> is removed from the stem <NUM>, a fine metric threaded thread <NUM> of this tool may be engaged with the fine metric threaded thread <NUM> (see <FIG>) in the stem <NUM>, and if so desired, the stem <NUM> may be removed. The stem exchange tool <NUM> has a full round flange <NUM> for impactor use to aid stem withdrawal, regardless of how deep the threads are engaged with each other.

If a stem <NUM> is being implanted without a polymeric liner <NUM>, then the stem exchange tool <NUM> may be used to position the stem <NUM> and facilitate impaction of the stem <NUM> into place. The same would hold true for a stem without a polymeric liner, having instead a metal socket with mating threads for the stem exchange tool <NUM> distal to the socket.

<FIG> illustrates a circular indented handwheel which is at the proximal shaft ends of many prior art orthopaedic broaches. The prior art circular proximal shaft ends (used with impactors for tool removal) are gripped by the surgeon and can promote twisting of the tooling which can lead to larger apertures in the bone than intended. The aperture created by a broach cutting head should correspond to the geometry of the implant. Prior art broaches with the circular type of handles are twisted to gain purchase in the bone.

In the tool set, the tools have plain elongate proximal handles <NUM> which are fluted <NUM> to aid grip as illustrated in <FIG>. The tooling therefore promotes axial motion, and this leads to aperture creation in the bone which conforms more exactly to the geometry of the broach cutting head and thus the implant.

The primer <NUM>, the broaches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and the stem exchange tool <NUM> all have flanges <NUM>, <NUM> at the distal end of the handle <NUM> as illustrated in <FIG>. The flanges <NUM> (and <NUM> on the tool <NUM>) enable an impactor to be used, if required, for tool extraction purposes. They also serve as a stop for the surgeon's hand and, coupled with the flat on the handle which carries the tool identification <NUM> and serves as a thumb grip, the primer <NUM> and broaches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> promote firm axial forward motion.

This means that, in contrast to other tooling, the tooling of the invention requires little or no impacting. This reduces potential fracture damage of the bone during surgery which has been observed in clinical practice with conventional tools.

The flanges <NUM> of the primer <NUM> and all broaches <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are truncated to provide a noncircumferential side edge <NUM> on the volar aspect at <NUM>° as illustrated in <FIG>.

This facilitates the surgeon, by enabling the tools to be used at an angle very much in line with the axis of the metacarpal during surgery. This feature also further reduces any tendency for the surgeon to twist the tool, and it also permits ample space on the distal side of the flange for an impactor to aid withdrawal of the tool, should that be required.

An alternative stem insertion tool <NUM> incorporates a ball <NUM> where the diameter is less than that of the implant head ball diameter, but is just sufficient to provide a light snap-fit. This light snap-fit provides attachment between the tool <NUM> and the implant stem-liner assembly <NUM>, such that the surgeon may use the tool to transport the implant from the preparation area directly to the implant site.

The tool set may additionally include a tool <NUM> to withdraw a liner <NUM> which has been assembled in a stem <NUM>, which in turn has been implanted in a metacarpal. There may be occasion to withdraw a liner when access to the threaded portion <NUM> of the stem is required in order to withdraw or exchange the stem. A threaded head <NUM> of the tool <NUM> is configured as a double-start tapered thread where the helices of the thread engage with the snap-fit diameter of the socket within the liner <NUM>. The tool <NUM> is threaded into the liner <NUM> until resistance is felt at which point the liner <NUM> is readily levered out of the stem housing <NUM> (illustrated in <FIG>).

The trial head <NUM> conforms to the geometries of the associated implant head <NUM>, except for having two through holes <NUM> through the saddle, and having two letter identifications appropriate to each of the four trial head types laser etched onto the base. The through holes <NUM> aid in differentiating the trial heads <NUM> from the implant's components <NUM>.

The ball diameter of the trial head <NUM> is also slightly smaller than the ball diameter of the implant head <NUM>, so that the snap-fit of the liner <NUM> is not stressed. Although the ball diameter is slightly reduced, the metacarpal to trapezium distraction distance is maintained the same as that of the implant heads <NUM>, by increasing the neck lengths of the trial heads <NUM>.

The use of trial heads <NUM> in conjunction with the implant stem <NUM> decreases the number of surgical steps to be successfully completed by the end user. It avoids need for the surgeon to open and use an implant on a trial-and-error bases, by using the trial head <NUM> to check size firstly before choosing the implant to use.

The instrument tray is advantageous in that, rather than containing multiple stand-offs to house individual tools <NUM>, all the tools are located by two strips <NUM>, <NUM> which may be of the polymer PPSU (polyphenylsulfone), mounted, such as screwed into a base <NUM> or integrally moulded with the base. The tools (only the tool <NUM> is shown) are further secured by a single strip <NUM> attached to the underside of a lid <NUM>, which acts on the thumb grip flats of the handles of the tools. Correct orientation of the lid <NUM> (and thus the securing strip <NUM>) is ensured by locating two latches closer together on one side of the lid than the other (not shown).

An assembly fixture <NUM> may be used in a surgical setting to assemble a liner <NUM> into a stem <NUM>. A base <NUM> of the fixture <NUM> has separate retainers <NUM> for each of the implant stem sizes. Each retainer <NUM> has a socket <NUM> for cradling the distal (narrow) end of the stem <NUM> to retain it in an upright position. The retainers <NUM> also have aligned upper through holes for retaining the wider (proximal) ends of the stems <NUM>. Each retainer is sized in increasing size order from left to right for a particular stem size, called Stem A, B, C, D, and E respectively.

The assembly also comprises a pusher <NUM> with a knurled thumbwheel <NUM> for rotating a screw <NUM> with a lower pusher face <NUM>. The screw <NUM> extends through a pusher body with a pair of parallel dovetails <NUM> for engaging in corresponding dovetail grooves <NUM>.

A stem <NUM> is placed vertically in the appropriate retainer <NUM>, a liner <NUM> is aligned with the universal cap formed by the body <NUM> of the pusher <NUM>, incorporating a light snap fit as it is fitted to the liner. The pusher <NUM>, when pushed fully home in any one of the sets of slots <NUM>, is positioned such that the centre of the screw <NUM> is centered over the stem. The screw <NUM> is then turned to fully push the liner <NUM> into the stem <NUM>, thereby seating the liner <NUM> in the stem <NUM>.

The following is a listing of all components of a full tool-set apparatus in one example.

It will be appreciated that the apparatus described provides major assistance to a surgeon for performing an operation, both in terms of accuracy and reduced time.

Claim 1:
A set of tools for installation of a stem implant into a bone, comprising:
a stem-shaped priming tool (<NUM>) having a distal tip and a plurality of cutting teeth along a length thereof; and
a plurality of stem-shaped broaches (<NUM>-<NUM>) of different size, each of the broaches having a distal tip and a plurality of cutting teeth along a length thereof,
wherein the priming tool is shorter than, has more cutting teeth per unit length, and has a sharper distal tip than the smallest broach,
a liner exchange tool (<NUM>) comprising a threaded head (<NUM>) configured as a double-start tapered thread,
wherein the priming tool and the broaches each comprises a proximal handle (<NUM>) and a flange (<NUM>) distal of the proximal handle, wherein the flange (<NUM>) is truncated (<NUM>) on one side of the handle, and
at least one dual-purpose tool (<NUM>, <NUM>) selected from:
a first dual-purpose tool (<NUM>) having a head which provides both a rasp (<NUM>) and a broach (<NUM>), and
a second dual-purpose tool (<NUM>) which comprises a claw head with a lever (<NUM>) for elevation of a bone, and the lever comprises a distal engagement slot (<NUM>).