Patent Description:
In total hip replacement surgery, a patient's natural hip is replaced by an acetabular cup component that replaces the acetabular socket and a femoral component that replaces the femoral head.

The femoral component of the hip prosthesis includes a generally spherical head, connected via a neck portion, to an elongate stem. The patient's femur is prepared to receive the stem. The proximal end of the femur is resected to expose the medullary canal. This involves resection of at least part of the greater femoral trochanter, and the creation of a cavity that matches the shape of the implant stem.

Surgeons may use several different instruments such as an osteotome, rasp, canal probe, and starter broach to initiate the canal. Changing between instruments takes time. Additionally, the number of instruments required for surgery indirectly increases cost of a procedure.

There is therefore a need for a multifunctional instrument that combines the functionality of existing instruments.

To help ensure proper final orientation of the stem, lateral bias during implant preparation may be preferred. Retraction of the gluteus medius and removal of the lateral cortical bone at the trochanteric fossa helps the surgeon to obtain optimal proximal fit of the stem. This also reduces the risk of undersizing and/or varus placement of the stem.

Surgeons currently face several challenges when using traditional osteotomes. For example, the surgeon conventionally positions the osteotome relative to external anatomical landmarks, such as the trochanteric fossa, in an effort to position the osteotome to cut the desired bone leading to the femoral canal. Since every bone is shaped differently, the surgeon may not correctly predict the starting position which would lead to the desired bone removal. This may be further exacerbated by a poor grip between the osteotome and the bone surface, resulting in slippage of the osteotome after initial placement caused by impaction strikes.

The surgeon also conventionally angles the osteotome relative to the external anatomical landmarks, such as the femoral leg axis, in an effort to direct the angle that the osteotome resects the bone. Since it is often difficult to visualize the external anatomical landmarks and to hold the osteotome at the desired angle while impacting, the surgeon may not achieve the desired angle of bone removal.

The necessary amount of lateral bone may not be fully removed by the first cut. This is particularly true if the surgeon adopts a conservative and iterative bone cutting approach. Thus, further cuts with the osteotome, or removal of the bone with other instruments (e.g., rasp, rotational initiator or broach) may be required.

<CIT> discloses an apparatus for replacing the knee joint with an implant prosthesis. The apparatus includes a notch cutter for cutting a bony channel into the end of the bone. The notch cutter comprises a box chisel and an attachment device for attaching the body of the notch cutter to an intramedullary guide starter drill and mill. The notch cutter includes a pair of curved legs which fit around the femoral condyles to align the notch cutter perpendicular to the condyles and brace it.

<CIT> discloses a modular prosthesis rasp. The rasp is provided with rasp teeth on its outer surface. A box chisel is connectable to the rasp main body for machining the bone.

There is therefore a need for an improved osteotome that does not rely on external visual landmarks for positioning. There is also a need for an osteotome having an improved grip on the proximal surface of the femur.

An aspect of the invention provides an osteotome according to claim <NUM>.

The osteotome includes a curved guide member which may extend distally from its medial side. This curved guide member interfaces with the medial curvature of the femoral canal. The guide member guides the osteotome using the internal bone geometry of the femoral canal instead of relying on external anatomical landmarks.

During initial positioning, the guide member provides haptic feedback of the location of the femoral canal. During impaction, the guide member helps to position and align the osteotome with the curvature of the femoral canal.

In some constructions, the curved guide member may extend distally from the medial side of the osteotome.

In some constructions, the curved guide member may comprise;.

in which each of the lateral face and medial face has a longitudinal curve extending between the proximal end of the guide member and the distal tip. The distal tip may be substantially straight. A distal tip that mimics the distal shape of a number of the broaches used to prepare the femoral canal and/or the femoral stem implant component may be provided.

The curved guide member comprises cutting elements. Advantageously, the curved guide member may have a profiled outer surface for removing bone. This provides the osteotome with broach functionality. The profiled outer profile may comprise a plurality of cutting elements. The cutting elements may be disposed along the length of at least one of the lateral face and the medial face of the curved guide member. The cutting elements may be in the form of cutting teeth.

The osteotome's cutting edge may include a least one tooth extending distally therefrom. For example, a "shark" tooth. Upon impaction of the osteotome, the at least one tooth bites into the proximal surface of the femur. This helps to maintain the rotational position of the osteotome on the bone surface and prevents slipping. As a result, the initial placement of the osteotome on the proximal surface of the femur is maintained, even during impaction strikes.

In some constructions, the distal tip of the curved guide member may include a plurality of longitudinal flutes disposed along its exterior surface. These flutes are adapted to remove bone when the curved guide member is inserted into the intramedullary canal. In some constructions, the flutes are provided with a blunt edge which enables the user to easily rotate the device in order to create a hole in the cancellous bone.

In some constructions, a lateral side of the body of the osteotome may be provided with a plurality of cutting teeth. This provides the osteotome with rasp functionality. The plurality of lateral cutting teeth are adapted such that any bone which is located laterally of the piriforma fossa, such as the greater trochanter, can be removed. Advantageously this rasping action provides the osteotome with the ability to be lateralised relative to the femoral canal. This results in the medial face of the curved guide member of the osteotome being located within the femoral canal such that it follows the medial curvature of the femoral bone.

The surgeon may find an osteotome provided with a depth indicator useful. The depth indicator may indicate to the surgeon the depth that the curved guide member of the osteotome should be progressed into the femoral canal in order to create the required depth of cavity. This depth indicator may take the form of an indicium provided on a wall of the body of the osteotome. This indicium may be a line. This line may be formed by the interface of two regions of the body of the osteotome. The interface may be a visual interface formed between two regions each having a different colour or textured surface.

The osteotome may be a box osteotome. During hip arthroplasty, the box osteotome cuts a box shape out of the femoral bone to open the patient's femoral canal.

The box osteotome may be generally provided with at least one window through which the surgeon can remove the resected bone during use. This window also enables cleaning of the device. Ideally, the at least one window is provided on a wall of the body of the box osteotome which allows the surgeon to hold the device without encountering any of the cutting teeth and also facilitates ease of cleaning.

The osteotome may be achieved by manufacturing using conventional manufacturing processes known in the art. The osteotome may formed by three-dimensional printing. The osteotome may be formed by a moulding technique, such as metal injection moulding (MIM).

According to a further aspect of the invention, there is provided a kit according to claim <NUM>. A broach may have a medial face and a lateral face, in which the curve of at least the medial face of the curved guide member of the osteotome matches a curve of the medial face of the broach. This ensures that the medial face of the curved guide member of the osteotome interfaces with the medial curvature of the femoral canal in the same manner as that of the medial face of the broach.

Advantageously, the outer profile of the curved guide member may match the outer profile of the smallest broach. This provides the curved guide member with the functionality of a starter broach. This prepares the bone cavity for further broaching. The fact that the outer profile of the curved guide member matches the outer profile of the smallest broach also ensures that one size of osteotome is safe to be used for all stem sizes.

According to a further aspect of the invention, there is provided a kit according to claim <NUM>. A femoral stem component may have a medial face and a lateral face, in which the curve of at least the medial face of the curved member of the osteotome matches a curve of the medial face of the femoral stem component. This ensures that the medial face of the curved guide member of the osteotome interfaces with the medial curvature of the femoral canal in the same manner as that of the medial face of the femoral stem component.

Constructions of the guided osteotome will be described hereinafter, by way of example only, with reference to the accompanying drawings in which like reference signs relate to like elements and in which:.

Constructions of the guided osteotome are described in the following with reference to the accompanying drawings.

Referring now to <FIG>, there is shown a box osteotome <NUM> for use in preparing the proximal end of a patient's femur. The osteotome includes a body <NUM> and a curved guide member <NUM>.

The body <NUM> has a proximal end <NUM> and a distal end <NUM>. The proximal end <NUM> includes a connection element <NUM> that is adapted to facilitate the releasable connection of the osteotome to a handle, such as a broach handle. As shown, the connection element <NUM> is a female connection element that is adapted to connect with a male connection element on a handle. In other constructions, the connection element is a male connection element that is adapted to connect with a female connection element on a handle.

The distal end <NUM> includes a generally rectangular aperture <NUM> that extends proximally into the body of the osteotome. The outer periphery of the aperture is bordered by a cutting edge <NUM>. A plurality of cutting elements <NUM>, <NUM> shown here in the form of shark teeth, extend distally from the lateral edge of the aperture <NUM>. The shark teeth help to anchor the osteotome within the proximal surface of the femur and prevent slippage during impaction. A plurality of cutting elements <NUM> are also provided on the lateral face <NUM> of the body. Cutting elements <NUM> provide the osteotome with a rasping functionality. This facilitates removal of laterally located bone, such as the areas of the greater trochanter.

The body also includes a window <NUM> through which resected bone is removed. The window also aids with the cleaning of the osteotome. The window is connected to the aperture <NUM>. The window <NUM> in the construction shown is provided on the anterior face <NUM> of the body <NUM>. However, the window can be provided on other external faces of the body. Preferably, the window is provided on the body in a location that enables the surgeon to handle the device away from any of the cutting elements. For example, as shown in <FIG>, in a second construction of the box osteotome <NUM>, the window <NUM> is provided on the medial face <NUM> of the body <NUM>. This enables the surgeon to grip the device about the anterior face and the posterior face (not shown).

The body <NUM>, <NUM> may also be provided with a depth indicator. The depth indicator can be used to indicate to the surgeon the depth that the curved guide member <NUM> should be progressed into the femoral canal in order to create a cavity having a depth that generally matches the longitudinal length of a starter broach or femoral stem component. In the first construction (<FIG>), the depth indicator takes the form of a raised edge <NUM> extending at least partially between the lateral face <NUM> and medial face <NUM> of the body. In the second construction (<FIG>), the depth indicator is formed by the interface <NUM> between a first region <NUM> of the body <NUM> having a first colour (e.g., silver) and a second region <NUM> of the body <NUM> having a second colour (e.g. black). The interface <NUM> extends at least partially between the lateral face <NUM> and medial face <NUM> of the body <NUM>. In the third construction (<FIG> and <FIG>), the depth indicator takes the form of a line <NUM> applied, for example by laser marking, to the body of the device. The line extends at least partially between the lateral face <NUM> and medial face <NUM> of the body <NUM>.

Referring again to <FIG>, the curved guide member <NUM> extends from the medial edge <NUM> of the aperture <NUM>. The curved guide member includes a longitudinal shaft <NUM> with a proximal end <NUM>, a distal tip <NUM>, a lateral face <NUM> and a medial face <NUM>. The lateral face <NUM> and the medial face <NUM> have a longitudinal curve extending between the proximal end <NUM> of the curved guide member and the distal tip <NUM>. Advantageously, the curvature of the medial face <NUM> is designed to generally match the curvature <NUM> of the medial face of the starter broach <NUM> to be used in the preparation of the femur, and also the femoral stem component <NUM> to be implanted within the femur. This is shown with reference to a third construction of the osteotome <NUM>, in <FIG> (an overlapping image with a starter broach) and <FIG> (an overlapping image with a femoral stem component).

In the construction shown, cutting elements <NUM> are disposed along both the lateral face <NUM> and the medial face <NUM> of the curved guide member. In other constructions, the cutting elements may be disposed on only one of the lateral face <NUM> or the medial face <NUM>. The cutting elements <NUM> provide the osteotome with a broaching functionality.

The distal tip <NUM> of the curved guide member <NUM>, <NUM> includes a plurality of longitudinally extending flutes <NUM>. These flutes <NUM> are adapted to remove bone when the curved guide member is inserted into the intramedullary canal. The flutes <NUM> may have a blunt edge. This enables the user to easily rotate the osteotome in order to create a hole in the cancellous bone. The distal tip of the curved guide member may be designed to generally match geometry of the distal tip of the broaches used to prepare the intramedullary canal and/or the femoral stem component.

In use, the surgeon or other operator would use the osteotome <NUM> which would include the body <NUM> having the proximal end <NUM> connectable to the handle (not shown) and the distal end <NUM> having the cutting edge <NUM>. The osteotome <NUM> would also include the curved guide member <NUM> extending in a distal direction from the distal end <NUM>. The user would then position the osteotome <NUM> at a proximal end of the femur and insert the distal end of the curved guide member into a canal of the femur. Using the osteotome, the operator would shape the proximal end of the femur with the osteotome.

Claim 1:
An osteotome (<NUM>) for preparing a proximal end of a femur of a patient for installation of a stem of a femoral component of a prosthetic hip during hip replacement surgery, the osteotome (<NUM>) comprising:
a body (<NUM>; <NUM>; <NUM>) having
a proximal end (<NUM>) connectable to a handle, and
a distal end (<NUM>) having a cutting edge (<NUM>), wherein the distal end (<NUM>) includes an aperture (<NUM>) extending proximally into the body (<NUM>; <NUM>; <NUM>) of the osteotome (<NUM>), and wherein the aperture (<NUM>) is bordered by the cutting edge (<NUM>), and
a guide member (<NUM>) extending in a distal direction from the distal end (<NUM>) of the body (<NUM>; <NUM>; <NUM>),
characterised in that, the guide member is curved and in that the curved guide member (<NUM>) further comprises cutting elements (<NUM>).