Patent Description:
In hip arthroplasty, the anatomic reconstruction of the joint is sought. The natural acetabulum is removed and replaced with an implant formed of an acetabular shell placed in the recess in the bone and fixed in position. Subsequently, an appropriately sized liner is inserted into the shell, mated and locked. On occasions, it is necessary to remove a polyethylene acetabular liner from an implanted shell, for instance to remove that liner and replace it with another.

Existing designs provide for jaw based surgical instruments which are used to take hold of the liner and apply a force to pull the liner from the shell.

It is desirable for the surgical instrument, system or methods of use to remove the liner without damaging or risking damage to the shell holding it. It is desirable for the surgical instrument, system or methods of use to be easily positioned, used and removed. It is desirable for the surgical instrument, system or method of use to effectively and reliably remove the liner, in wound sites which are hard to access or have limited access.

A surgical instrument according to the invention is defined in claim <NUM>, with various embodiments defined in dependent claims <NUM>-<NUM>.

According to a second aspect of the invention there is provided a surgical system according to claim <NUM> and its dependent claims.

Various embodiments of the disclosure will now be described, by way of example only, and with reference to the accompanying drawings in which:.

In hip arthroplasty the anatomic reconstruction of the joint is sought. The natural acetabulum is removed and replaced with an implant formed of an acetabular shell placed in the recess in the bone and fixed in position. Subsequently, an appropriate sized liner is inserted into the shell, mated and locked. On occasions, it is necessary to remove a polyethylene acetabular liner from an implanted shell, for instance to remove that liner and replace it with another. This must be done whilst minimising the risk of damage to the shell holding it.

One prior art instrument, a liner extractor <NUM>, is illustrated in <FIG>. This provides a first jaw <NUM> and second jaw <NUM> pivotally mounted relative to one another about pin <NUM>. The distal end <NUM> of the first jaw <NUM> extends beyond the distal end <NUM> of the second jaw <NUM>. The distal end <NUM> of the first jaw <NUM> is provided with a pair of contact surfaces <NUM> facing the second jaw <NUM>. The distal end <NUM> of the second jaw <NUM> is provided with a pair of teeth <NUM> facing generally towards the first jaw <NUM>.

As can be seen in <FIG>, the first jaw <NUM> has a separate central element <NUM> which is provided between a first jaw element 19a and second jaw element 19b which in combination form the first jaw <NUM>. The distal end <NUM> of the central element <NUM> has an abutment surface <NUM> generally perpendicular to the pair of contact surfaces <NUM>.

With the first jaw <NUM> and second jaw <NUM> open, wider than is shown in <FIG> where the closed state is shown, the liner extractor <NUM> can be engaged with a liner <NUM> sitting in a shell <NUM>, as shown in <FIG>. The abutment surface <NUM> is brought into contact with the circumferential face <NUM> of the shell <NUM>. This limits axial movement of the liner extractor <NUM> relative to the shell <NUM>. The pair of contact surfaces <NUM> are brought into abutment with the small side wall <NUM> of the liner <NUM>. Closing the jaws, by moving the second jaw <NUM> inwards towards the first jaw <NUM>, brings the pair of teeth <NUM> into contact with the inside of the liner <NUM>. The teeth <NUM> are sharp enough to penetrate the liner <NUM> upon application of force through the liner extractor <NUM>, as the contact surfaces <NUM> and side wall <NUM> combine to prevent movement of the first jaw <NUM>.

In <FIG>, the partial removal of the liner <NUM> from the shell <NUM> is shown. This is achieved by retraction of the first jaw element 19a and second jaw element 19b relative to the central element <NUM>. Hence, the central element <NUM> maintains the position of the shell <NUM> and the liner <NUM> is eased out of the shell <NUM>.

As access to the wound site is not easy, the positioning of the liner extractor <NUM> with the abutment surface <NUM> and contact surfaces <NUM> in the necessary position during movement of the contact surfaces and abutment surface relative to one another can be awkward.

Another instrument-based option for liner <NUM> removal is to form a pilot hole in the liner <NUM>. Initial engagement of a self-tapping screw in the pilot hole is then provided, with tightened of the screw pushing between the liner <NUM> and the shell <NUM> with sufficient force to remove the liner <NUM> from the shell <NUM>. Where the liner <NUM> is of the thicker and/or larger and/or stiffer variety, then multiple pilot holes and self-tapping screws may be needed.

In this type of option, to be effective, the pilot hole needs to be created in a consistent and precise location and also with a consistent angularity with respect to the liner <NUM>. This needs to be achieved in a wound space which frequently only offers difficult access.

<FIG> illustrates one example of the disclosure which provides a surgical instrument in the form of guide instrument <NUM>, a surgical tool in the form of a drill bit <NUM>, an intermediate section in the form of an extension drive <NUM>. <FIG> also shows the same extension drive <NUM> engaged with a different surgical tool, a self-tapping screw <NUM>.

The guide instrument <NUM> includes a guide element in the form of a guide piece <NUM> at the distal end <NUM>. The guide piece <NUM> is mounted on a stem <NUM> with a handle portion <NUM> at the proximal end <NUM>. The stem <NUM> is divided into several sections. A first section, a transition section <NUM>, spaces the rest of the guide instrument <NUM> from the operative axis of the drill bit <NUM>. A second section, aligned section <NUM>, is aligned with but spaced from the operative axis of the drill bit <NUM> and thereby aligns force applied through the handle portion <NUM> to the liner <NUM> in use, with the axis along which force applied through the drill bit <NUM> passes to the liner <NUM> in use. A third section, inclined section <NUM>, is inclined away from the operative axis of the drill bit <NUM> so as to increase the space and improve the line of sight for the surgeon down to the distal end <NUM>. The third section, inclined section <NUM>, leads to the handle portion <NUM>.

In use, as shown in <FIG>, the distal end <NUM> of the guide instrument <NUM> is brought into proximity with the junction <NUM> between the liner <NUM> and the shell <NUM>. The guide piece <NUM> on the distal end <NUM> provides a guide channel in the form of a through bore <NUM> through which the drill bit <NUM> can be inserted. The axis of the bore <NUM> matches the operative axis for the drill bit <NUM>, in use.

The guide piece <NUM> is provided with a configuration that provides visual clues and guides to its correct alignment/positioning with respect to a liner <NUM> and/or shell <NUM>. The guide piece <NUM> includes a first extending element 130a which extends from a body element <NUM>, provided at the junction of the guide piece <NUM> and the transition section <NUM>. The first extending element 130a extends in a first direction. A second extending element 130b is provided in the same manner, but extending in the opposing direction. The first and second extending elements are one form of the positioning location supports. Both the first extending element 130a and the second extending element 130b have a body element contacting end <NUM> and an extending element protruding end <NUM>. The two protruding ends <NUM> are turned towards one another. A chord drawn between the two protruding ends <NUM> will pass closer to the axis of the bore <NUM> than a chord drawn between other parts of the extending elements and particularly between the body element contacting ends <NUM>. In the illustrated example this is provided by curvature of the first extending element 130a and the second extending element 130b.

At the distal end <NUM> of the guide piece <NUM>, as seen in <FIG> and <FIG>, a planar distal end face <NUM> is provided around the bore <NUM>. This is one form of the secondary positioning locations. In this example, a common distal end is provided for both the first extending element 130a and the second extending element 130b by a contiguous planar distal end face <NUM>. This distal end face <NUM> extends the full length of the curvature of both the first extending element 30a and the second extending element 30b. This is one form or the positioning locations. The distal end face <NUM> is provided on a distal end section <NUM>. The distal end section <NUM> has a smaller cross-section away from the distal end face <NUM> than at the distal end face <NUM> and hence a distal edge <NUM> is defined. The distal edge <NUM> extends along the full curvature of both the first extending element 30a and the second extending element 30b in this form.

Referring to <FIG>, the interaction of the distal edge <NUM> with a first combination of shell <NUM> and liner <NUM> is shown. In this example, the liner <NUM> has a relatively small extent of protrusion from the shell <NUM> and so the perimeter edge wall <NUM> has only a small height. Different interactions, as further exemplified below, will occur for different liner <NUM> and shell <NUM> combinations.

In <FIG>, the distal end face <NUM> and distal edge <NUM> has a greater distal extent relative to the guide instrument <NUM> than the guide piece <NUM>, for instance the distal end face <NUM> thereof. The planar distal end face <NUM> is parallel to but not co-planar with the distal end face <NUM> of the guide piece <NUM>.

In use, this means that as the guide instrument <NUM> is brought towards the shell <NUM> and liner <NUM>, one end then the other or both simultaneously of the distal end face <NUM> will abut the circumferential end face <NUM> of the shell <NUM>. This limits generally axial movement of the guide instrument <NUM>. The distal end face <NUM> can then be slid radially inward relative to the shell <NUM> and liner <NUM> across the end face <NUM>. This continues until parts of the distal edge <NUM> abut the raised perimeter edge wall <NUM> of the liner <NUM> formed by the liner <NUM> extending slightly above the plane of the end face <NUM> of the shell <NUM>. At this point, the liner <NUM> resists further inward movement. In the illustrated form, the curvature of the distal edge <NUM> is such that the ends of the distal edge <NUM> provide the abutment. The profile of the distal edge <NUM> is such that its ends act like teeth <NUM>. The distal edge <NUM> faces laterally away from the extending elements relative to the proximal to distal orientation of those extending elements. That is the distal edge <NUM> faces towards the liner <NUM> in use, and in particular towards the perimeter edge wall <NUM> at the junction of the liner <NUM> and shell <NUM>. The application of radial force to the guide piece <NUM> through the handle portion <NUM> causes the teeth <NUM> at the ends of the distal edge <NUM> to penetrate the material of the liner <NUM> and particularly to penetrate the perimeter edge wall <NUM>. The limited extent of the distal edge <NUM> and it not being possible to cause the extending element behind them to penetrate the liner <NUM>, means that the radial position of the extending elements 130a, 130b and hence of the guide piece <NUM> and hence the bore <NUM> is very closely controlled. The pilot hole is created in a consistent and precise location.

In an alternative format, the curvature of the distal edge <NUM>, particularly its radius of curvature, could be greater than the curvature, particularly radius of curvature of the liner, such that intermediate locations on the distal edge <NUM> abut the liner. The distal edge <NUM> is sharp enough along its length to penetrate the liner <NUM> and so act in a tooth like manner at that abutment.

<FIG> shows the pilot hole <NUM> being formed by a drill bit <NUM>. The drill bit <NUM> extends through the guide piece <NUM>, into the liner <NUM> and down to the junction between the liner <NUM> and the shell <NUM>. The teeth <NUM> at the ends of the curved edge <NUM> are engaged with the liner <NUM>.

The location used for the pilot hole <NUM> is adjacent the peripheral edge of the liner <NUM> and is also adjacent the peripheral edge of the shell <NUM>. In this area, no contact between the shell <NUM> and the liner <NUM> is intended in use, and so, even if the removal of the liner <NUM> by the disclosure causes minor damage to the shell <NUM>, that minor damage is not in a material location on the shell <NUM>. If a location further into the liner <NUM>, for instance at or close to the pole of the liner <NUM> and shell <NUM>, was used then any damage would be in a material area. The location used for the pilot hole <NUM> is however far enough radially inward relative to the edge of the liner <NUM>, that the pilot hole <NUM> is away from the retaining mechanism <NUM>, <NUM> for the liner <NUM> in the shell <NUM>. In the illustrated example, a lug <NUM> on the shell <NUM> engages with a recess <NUM> on the liner <NUM>, but other retention mechanisms are possible.

The peripheral location for the pilot hole <NUM> has been established in testing to offer the most effective approach to removing the liner <NUM> from the shell. This is particularly important in providing enough force to overcome the retention force between the liner <NUM> and the shell <NUM>. The peripheral location is more effective than locations further into the liner <NUM>, for instance at or close to the pole <NUM> of the liner <NUM> and shell <NUM>.

Referring to <FIG>, a different interaction of the distal edge <NUM> with a first combination of shell <NUM> and liner <NUM> is shown. In this example, the liner <NUM> has a relatively large extent of protrusion from the shell <NUM> and so the perimeter edge wall <NUM> has a significant height.

In use, this means that as the guide instrument <NUM> is brought towards the shell <NUM> and liner <NUM>, the distal end face <NUM> will abut the circumferential end face <NUM> of the liner <NUM>. This limits generally axial movement of the guide instrument <NUM>. The distal edge <NUM> in this position is still spaced from the circumferential end face <NUM> of the shell <NUM>, but the distal edge <NUM> can still be slid radially inward relative to the shell <NUM> and liner <NUM> until sections of the distal edge <NUM>, in the illustrated example the teeth <NUM> at the ends, abut the raised perimeter edge wall <NUM> of the liner <NUM> formed by the liner <NUM> extending slightly above the plane of the end face <NUM> of the shell <NUM>. At this point, the liner <NUM> resists further inward movement. The application of radial force to the guide piece <NUM> through the handle portion <NUM> causes the distal edge to penetrate the material of the liner <NUM> and particularly to penetrate the perimeter edge wall <NUM>.

Whilst the embodiments above reference a tooth <NUM> at each end of a continuous distal edge <NUM> for providing the penetration of the liner <NUM>, it is possible to provide two or more teeth in other positions. A series of teeth spaced along the distal edge <NUM> and/or a serrated distal edge <NUM> could be provided. Equally it is also possible to rely upon intermediate parts of the distal edge <NUM> engaging with and penetrating the liner <NUM>.

The configuration of the distal edge <NUM> of the extending elements and/or the teeth <NUM> means that a wide range of different diameter shells <NUM> and liners <NUM> can be used successfully with the same guide instrument <NUM>.

The drill bit <NUM> is provided separately from the guide instrument <NUM> and is mounted on an extension drive or other actuating instrument <NUM>, optionally in the manner described in more detail below. The same diameter of drill bit <NUM> is suitable for a wide range of liner <NUM> sizes and so a given guide piece <NUM> and guide instrument <NUM> is also widely applicable.

The guide piece <NUM> through bore <NUM> has an axis X-X which gives the desired pilot hole with a consistent angularity with respect to the liner <NUM> as the bore <NUM> limits the operative axis of the drill bit <NUM> to the same axis X-X. The cross-section of the bore <NUM> perpendicular to the axis X-X [plus a clearance tolerance] matches that of the cross-section of the drill bit <NUM> also perpendicular to the axis X-X.

In use, therefore, with the guide instrument <NUM> in position on the shell <NUM> and liner <NUM>, with parts of the distal edge <NUM> or teeth <NUM> in the material of the liner <NUM>, the drill bit <NUM> on the drive extension <NUM> is slid into the bore <NUM> and into abutment with the surface of the liner <NUM>. A manual or powered actuator <NUM> [shown schematically in <FIG>] connected to the drive extension <NUM> is used to rotate the drill bit <NUM> and hence form a pilot hole in the liner <NUM>. Once the desired depth of pilot hole is formed, the drive extension <NUM> and the drill bit <NUM> can be retracted. The guide instrument <NUM> can then be moved outward to disengage the parts of the distal edge <NUM> or teeth <NUM> and can then also be withdrawn.

If necessary, the process can be repeated at other locations to provide other pilot holes.

A drive extension <NUM>, which could be the same one with the drill bit <NUM> disconnected, is then provided with a self-tapping screw <NUM>. The distal end of the screw <NUM> is inserted into the end of the pilot hole and rotation of the drive extension <NUM> causes the screw <NUM> to advance into the liner <NUM>. Continued advancement of the screw <NUM> causes the liner <NUM> to be displaced from the shell <NUM>.

The drill bit <NUM> can be mounted on an extension drive <NUM> or other actuating instrument <NUM> in various ways. One option under the disclosure is illustrated in <FIG>.

The drive extension <NUM> has an internal bore in its distal end <NUM> which receives the proximal end <NUM> and end section <NUM> of the drill bit <NUM> and similarly the proximal end <NUM> and end section <NUM> of the screw <NUM>. The end sections <NUM>, <NUM> have equivalent cross-sectional profiles and as illustrated are provided with six regularly spaced and matching size flats <NUM> which provide an hexagonal drive interface. The internal bore of the drive extension <NUM> is provided with a corresponding drive profile; in the illustrated case with six regularly spaced and matching size flats <NUM> which provide an hexagonal drive interface. The cooperation of the two drive faces readily transfers torque from the drive extension <NUM> to the drill bit <NUM> or screw <NUM>. The depth of the internal bore, considered along axis X-X, matches the length of the end sections <NUM>, <NUM> such that abutment of the proximal ends <NUM>, <NUM> with the base <NUM> of the bore <NUM> results in correct alignment of the drive interfaces. The abutment also constrains axial movement of the drill bit <NUM> or screw <NUM> into the drive extension <NUM> and allows application of axial force to encourage the drill bit <NUM> or screw <NUM> into the material of the liner <NUM>.

It is desirable to provide for easy engagement and disengagement of the drill bit <NUM> and/or screw <NUM> with the drive extension <NUM>. At the same time, there is a need to retain the drill bit <NUM> and/or screw <NUM> on the drive extension <NUM> during their movement to the position of use and during their movement away from the position of use. In the disclosure, this level of axial restraint for the drill bit <NUM> and/or screw <NUM> against relative axial movement away from the drive extension <NUM> is provided by the interaction of an O-ring <NUM> on one with the surface on the other. In one form, the O-ring <NUM> is provided on the single use drill bit <NUM> rather than in the internal bore <NUM> of the drive extension <NUM>. Similarly the O-ring <NUM> may be provided on the single use screw <NUM> rather than in the internal bore <NUM> of the drive extension <NUM>.

In that one form, as the drill bit <NUM> is slid into the internal bore <NUM>, at least when the proximal end <NUM> approaches the base <NUM> of the bore <NUM>, the internal profile of the bore <NUM> causes compression of the O-ring <NUM>. The resilience of the O-ring <NUM> resists this compression and hence resists axial movement of the drill bit <NUM> out of the bore <NUM>. The resistance is sufficient to prevent the weight of the drill bit <NUM> or a knock to the drill bit <NUM> causing it to detach from the drive extension <NUM>. The O-ring <NUM> on the screw <NUM> operates and interacts in an equivalent manner. The resistance to axial movement is limited, however, and so the drill bit <NUM> or screw <NUM> can readily be pulled out of the drive extension <NUM> when desired, for instance to swap from the drill bit <NUM> to a screw <NUM>. As the drill bit <NUM> and screw <NUM> are intended to be single use, there is no need to sterilise a structure with an O-ring <NUM> present.

Claim 1:
A surgical instrument (<NUM>), the instrument comprising:
a stem (<NUM>), the stem having a proximal end (<NUM>) and having a distal end (<NUM>);
a handle portion (<NUM>), the handle portion being provided towards the proximal end of the stem; and
a guide element (<NUM>), the guide element being provided towards the distal end of the stem, wherein the guide element provides:
a body element defining a guide channel (<NUM>), the guide channel having a longitudinal axis and being open at both ends along the longitudinal axis; and
one or more positioning elements (130a, 130b), characterised in that a curved element and/or an edge (<NUM>) is provided towards the distal end of the one or more positioning elements, and wherein the curved element and/or edge project away from the guide element towards a longitudinal axis of the guide channel.