The present invention relates to devices and methods for optimising the inclination angle of implants, particularly acetabular cups.

It is known to implant an acetabular cup into the acetabulum using an introducer. An introducer may also be referred to as an inserter or impactor. An introducer is a device comprising a shaft having a proximal end and a distal end. An implant such as an acetabular cup is reversibly connected to the distal end of the introducer and the surgeon manipulates the introducer so as to position the implant in a surgical site such as an acetabulum. When the implant is correctly positioned, the surgeon applies impact force to the proximal end of the introducer and the force is transferred via the introducer shaft to the implant, thereby impacting it into the surgical site.

Implants such as acetabular cups are produced in different sizes (for example different diameters). Producing a range of introducers specific to each implant size is not practical or cost-effective. It is therefore advantageous to provide a modular system comprising a single introducer and a series of devices that correspond to the different sizes of implant and which are reversibly attachable to an implant and to the distal end of the introducer such that it is the device that contacts the implant. These devices are known as impactor caps.

When implanting an acetabular cup, the introducer is disposed with respect to the inner bearing surface of the acetabular cup. Direct contact of the introducer with the bearing surface is best avoided as this may damage the bearing surface during implantation. This is particularly important in the case of metal on metal (MOM) bearing surfaces, wherein direct contact of the introducer with the bearing surface has to be avoided. In order to prevent damage to the bearing surface of the acetabular cup, an impactor cap is located on the distal end of the introducer such that it is the impactor cap that contacts the bearing surface of the acetabular cup. Accordingly, the impactor cap is made of a suitable material that does not damage the bearing surface under load during impaction. Therefore, impactor caps may be made of relatively soft, elastic, non-abrasive materials. For example, impactor caps may be made of suitable polymer materials, such as ultra-high molecular weight polyethylene (UHMWPE).

For non-MOM bearings, the inner bearing surface of the implant may not need protecting from damage during insertion, unlike MOM bearings. For such bearings, the impactor caps may be made of other suitable materials, such as harder, less elastic materials. For example, impactor caps may be made of metal or metal alloy materials.

In order to function properly, the inclination angle of an acetabular cup in an acetabulum may be in the range 30-55°. The optimum inclination angle may be in the range 35-50°. The optimum inclination angle may be in the range 35-45°. Frequently, a surgeon needs to implant the acetabular cup with a reduced angle of inclination in the acetabulum. Usually, an inclination angle in the range 40-45° is optimal. An inclination angle of around 42° is particularly preferred.

Known impactor caps are based on a cylinder, having two circular end surfaces that are oriented parallel to each other, and perpendicular to the main axis of the impactor cap and the introducer, when connected. Accordingly, in order for a surgeon to correctly position the acetabular cup at or near to an inclination angle of 45° relative to the acetabulum, the surgeon positions the entire assembly of introducer, impactor cap and acetabular cup at or near to an angle of 45° with respect to the acetabulum.

However, if the surgeon needs to reduce the angle of inclination of the acetabular cup, positioning the known device assemblies at such angles is problematic in that the surgeon has to work against the soft tissue incision. The surgeon may have to resort to increasing the length of the incision resulting in further scarring. Consequently, the existing procedure is more onerous, more invasive and subject to damage and/or further scarring of the surgical site. This is clearly disadvantageous, particular in the context of minimally invasive surgery.

The present invention provides device and methods that overcome the disadvantages associated with known devices and methods.

According to a first aspect of the present invention, there is provided a device for impacting an implant, comprising: a first surface for engaging, in use, with the implant; and a second surface for engaging, in use, with a shaft having a proximal end and a distal end, wherein the first surface and the second surface are not parallel to one another, and wherein, in use, the distal end of the shaft releasably engages with the second surface of the device such that when force is applied to the proximal end of the shaft the force is transferred via the device to the implant, thereby impacting the implant.

According to a second aspect of the present invention, there is provided a device for impacting an implant, comprising: a first surface for engaging, in use, with the implant; and a second surface for engaging, in use, with a shaft having a proximal end and a distal end, wherein the first surface and the second surface are disposed at an angle to one another, and wherein, in use, the distal end of the shaft releasably engages with the second surface of the device such that when force is applied to the proximal end of the shaft the force is transferred via the device to the implant, thereby impacting the implant. The implant may be an acetabular cup.

The angle between the first surface and the second surface may be in the range 1-30°. The angle may be in the range 1-25°. The angle may be in the range 1- 20°. The angle may be in the range 5-20°. The angle may be in the range 5-15°. The angle may be in the range 8-12°. The angle may be around 10°.

According to some embodiments of the present invention, the device has at least one hole for receiving, in use, at least one wire for releasably connecting the device to a shaft.

According to some embodiments of the present invention, the device comprises more than one hole for receiving at least one wire, in use, wherein the holes are disposed equidistantly around the periphery of the device.

According to some embodiments of the present invention, the implant has at least one hole for receiving, in use, at least one wire for releasably connecting the device to the implant.

In use, the device and the shaft may be releasably connected by a bayonet-type connection.

In use, the device and the shaft may be releasably connected by a clamp-type connection.

In use, the device and the shaft may be releasably connected by a friction-fit connection.

In use, the device and the implant may be releasably connected by a bayonet- type connection. In use, the device and the implant may be releasably connected by a clamp-type connection.

In use, the device and the implant may be releasably connected by a friction-fit connection.

According to some embodiments of the present invention, the device has at least one hole disposed in the second surface for receiving, in use, a protrusion on the distal end of the shaft.

According to some embodiments of the present invention, the device has two holes disposed in the second surface for receiving, in use, two protrusions on the distal end of the shaft.

The device may have at least one notch disposed at the periphery of the device.

At least one of the first and second surfaces of the device may be based on a circle.

The first and second surfaces may be separated by an annular portion.

The at least one hole for receiving, in use, at least one wire for releasably connecting the device to a shaft may be disposed in the annular portion.

The at least one notch disposed at the periphery of the device may be disposed in the annular portion.

The second surface of the device may be continuous.

The second surface of the device may have an inset (recess). The device may be made of any suitable material.

The device may be made of a soft material.

The device may be made of an elastic material.

The device may be made of a non-abrasive material.

The device may be made of a polymer. For example, the device may be made of ultra-high molecular weight polyethylene (UHMWPE).

The device may be made of a hard material.

The device may be made of a non-elastic material.

The device may be made of a polymer.

The device may be made of a metal or metal alloy.

According to a third aspect of the present invention, there is provided a method for implanting an implant, comprising the steps of: providing a device according to the first or second aspect of the present invention; providing a shaft having a proximal end and a distal end; releasably engaging the first surface of the device with the implant; releasably engaging the second surface of the device with the distal end of the shaft; applying force to the proximal end of the shaft, thereby transferring the force via the shaft and the device to the implant and impacting the implant; and disengaging the device from the implant and the shaft. The implant may be an acetabular cup.

Reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 shows a side view of a device according to an embodiment of the present invention;

Figure 2 shows a perspective view of the device shown in Figure 1 ; Figure 3 shows a top view of the device shown in Figure 1 ; Figure 4 shows a top view of the device shown in Figure 1 attached to an acetabular cup for use with dysplasia screws;

Figure 5 shows a top view of the device shown in Figure 1 attached to an acetabular cup for use with dysplasia screws;

Figure 6 shows a perspective view of a device according to another embodiment of the present invention;

Figure 7 shows a perspective view of the device shown in Figure 6; Figure 8 shows anterior views of a device according to an embodiment of the present invention in use with an introducer in contrast with an introducer for a known device; Figure 9 shows axial views of a device according to an embodiment of the present invention in use with an introducer in contrast with an introducer for a known device; and

Figure 10 shows lateral views of a device according to an embodiment of the present invention in use with an introducer in contrast with an introducer for a known device.

Figures 1 and 2 show side and perspective views, respectively, of a device 1 according to an embodiment of the present invention. The device comprises a first surface 2 for engaging, in use, with an implant (not shown) and a second surface 3 for engaging, in use, with a distal end of a shaft (not shown). The first 2 and second 3 surfaces are separated by an annular portion 4. The first 2 and second 3 surfaces are disposed at an angle to one another. The angle may be in the range 1-30°. The angle may be in the range 1-25°. The angle may be in the range 1-20°. The angle may be in the range 5-20°. The angle may be in the range 5-15°. The angle may be in the range 8-12°. The angle may be around 10°.

Figure 2 shows a perspective view and Figures 3 to 5 show top views of a device 1 having a centrally disposed hole 5 and an offset hole 6. Central hole 5 is used to locate an introducer shaft central to device 1. Offset hole 6 is used to locate an offset protrusion on an introducer shaft to provide rotational stability of device 1.

Figures 2 to 5 show a pair of cut-outs (notches) 7a, 7b made in the outer periphery of annular portion 4. Cut-outs 7a, 7b may be used to enable the identification of the position of optional fins disposed on the outer surface of an acetabular cup 10.

Figures 2 to 5 show a pair of cut-outs (notches) 8a, 8b made in the outer periphery of annular portion 4. Cut-outs 8a, 8b may be used to enable the preparation of dysplasia screws which are threaded through optional attachment holes 11a, 11b disposed on the outer surface of an acetabular cup 10.

Figures 2 to 5 show three pairs of holes 12a, 12b, 13a, 13b, 14a, 14b located in the outer periphery of annular portion 4. Holes 12a, 12b, 13a, 13b, 14a, 14b are used for threading introducer wire to releasably connect the implant to the introducer.

Figures 6 and 7 show perspective views of a device 15 according to another embodiment of the present invention. Device 15 has similar features to device 1. However, instead of a continuous second surface 3 (device 1), device 15 has a second surface 16 in the form of a rim for engaging, in use, with a distal end of a shaft (not shown). That is, as shown in Figures 6 and 7, surface 3 of device 1 has been recessed in the central portion to form an outer rim 16 and an inner inset 17, wherein the outer rim 16 provides the second surface for engaging, in use, with a distal end of a shaft. The remaining features of device 15 may be the same as those for device 1 , as shown in figures 6 and 7. Advantages of this embodiment of the invention are that the recess/inset reduces the bulk of the device and allows better peripheral visibility for the surgeon.

Figures 8-10 show anterior, axial and lateral views, respectively, contrasting a device 1 according to an embodiment of the present invention in use with an introducer 18, with an introducer 19 (shown in grey-scale) for a known device (not shown). The acetabular cup 20 is shown with a reduced angle of inclination. Attached to the acetabular cup 20 is a device 1 according to an embodiment of the present invention. An introducer 18 is attached to the device 1. The orientation angle of introducer 18 is normal. Therefore, as a result of the device 1 the surgeon can implant the acetabular cup 20 with a reduced angle of inclination without having to change the orientation angle of the introducer. Accordingly, devices according to the present invention mean that the surgeon does not have to work against the soft tissues and/or increase the length of the incision. In contrast, the orientation angle of conventional introducer 19 is significantly different to the normal orientation angle. It is clear from the figures that a surgeon using conventional introducer 19 would have to work against the soft tissues and/or increase the length of the incision.

In use, the distal end of the shaft releasably engages with the second surface of the device such that when force is applied to the proximal end of the shaft the force is transferred via the device to the implant, thereby impacting the implant.

The figures show embodiments of the present invention which are intended for use with a wire-type introducer. However, the present invention also includes devices that can be used with other types of wireless introducers. For example, according to some embodiments of the present invention, the introducer may reversibly attach to a device by alternative mechanical means. Such alternative mechanical means include a bayonet type connection, a clamp type connection, and a friction fit, for example.

The figures show embodiments of the present invention having first and second surfaces based on a circle. However, the present invention also includes devices having different shapes and geometries.

The present invention also includes devices having different sizes corresponding to the different sizes of implant. For example, in the case of acetabular cups having a range of diameters, a series of devices may be provided having corresponding diameters.