GB2420715A

GB2420715A - Arthroplastic surgical apparatus

Info

Publication number: GB2420715A
Application number: GB0426665A
Authority: GB
Inventors: Babis Karagkevrekis
Original assignee: HOSPITAL BIRMINGHAM NHS F, University of
Current assignee: HOSPITAL BIRMINGHAM NHS F, University of
Priority date: 2004-12-06
Filing date: 2004-12-06
Publication date: 2006-06-07
Anticipated expiration: 2024-12-06
Also published as: GB0426665D0; GB2420715B

Abstract

This invention provides an arthroplastic surgical apparatus 2 comprising a means 4 to releasably mount a femoral ball 14, arranged in use to be demountably located in an acetabulum of an individual, and a means 10 to enable marking of an acetabulum when the means to releasably mount the femoral ball is located in the acetabulum, in use.

Description

IMPROVEMENTS IN AND RELATING TO ARTHROPLASTIC SURGICAL

APPARATUS

Field of the Invention

This invention relates to arthroplastic surgical apparatus.

Background to the Invention

Operations to repair or replace diseased or injured joints, known as arthroplasty, have been practiced worldwide for decades. Total knee and hip replacement arthroplastic operations have been refined to the point where nearly 600,000 people every year undergo such operations and return to a life of substantially pain-free mobility.

Total hip arthroplasty, the replacement of the hip joint, involves the replacement of the femoral ball of the femur and its corresponding socket in the pelvis, known as the acetabulum. The femoral ball is the roundtipped S...

uppermost portion of the femur, and the acetabulum is a forwardpositioned, cup-like indentation in the pelvis *. into which the femoral ball fits.

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During the procedure, a surgeon removes the femoral ball, and optionally part of the top of the femur below the ball, and replaces it with a metal stem with a replacement *Ia* ball. The surgeon also prepares the acetabulum to accept a replacement acetabular cup. Preparation of the acetabulum may involve removing or widening the acetabulum, in order that for example, a metal or plastics acetabular cup may be inserted into the acetabulum and be adhered or otherwise fixed thereto.

Flip replacement surgery presents significant obstacles for the surgeon. Among the most challenging is the placement of the replacement acetabular cup after preparation of the acetabulum. Approximately half of postoperative hip dislocations are due to misalignment of the replacement cup, and even with slight misalignment, the rate of wear within the replacement femoral ball and socket joint increases the likelihood of early implant failure due to excessive or uneven wear. Early implant failure requires additional hip surgery to replace the components.

As is commonly practiced today, a surgeon achieves proper positioning through "feel", that is, the surgeon uses specialised instruments combined with his or her hands to determine where best to remove bone in the acetabulum for insertion of the replacement cup, and how best to align the replacement cup in the prepared acetabular socket.

Once the cuts in the bone are made, the natural bone cannot be replaced and the alignment is set. S..

I S...

Various specialised instruments have been manufactured to S..

help the surgeon correctly align the replacement acetabular cup, for subsequent adhesion to the existing acetabular socket. One such instrument is the Apollo (RTM) apparatus manufactured by Zimmer, US. In this piece of apparatus, a cup positioner comprises a handle at the *..I end of which is an elongate member arranged to hold the replacement acetabular cup. At the joint between the handle and the elongate member is a positioning member comprising a right-angled rod extending 400 from the longitudinal axis of the handle and elongate member. The surgeon positions the right-angled member such that, when the vertical rod of the positioner is held "straight up and down" or at 90 to the body of the patient, the elongate member of the positioning apparatus provides a 40 abduction angle. To attach the replacement acetabular cup in the acetabular socket, a surgeon must have previously prepared the socket and adhered cement to the prepared socket or replacement cup. When the replacement acetabular cup on the end of the elongate member of the positioning apparatus is inserted into the prepared socket, a surgeon may then release the replacement cup into the prepared socket.

As can be seen, with the Apollo apparatus, prior to positioning of the replacement acetabular cup, a surgeon must have previously applied cement to the prepared socket or replacement cup. This method creates its own problems in that the cup must be positioned extremely accurately in a short period of time, in order that the cement does not set before the replacement cup is positioned accurately.

Furthermore, using this apparatus does not allow the surgeon to determine the optimum positioning of the cup in U...

conjunction with the optimum positioning of the U...

replacement femoral ball at the same time. U. S 4 4*

* Recently, attempts have been made to assist surgeons in S *UUU* * 25 hip arthroplasty, by the use of computed tomography.

Using infrared cameras, fluoroscopic images and simple tracking devices, computer-assisted hip replacement U...

operations reduce exposure to radiation and reduce the need for invasive surgery. By combining fluoroscopic images of the femur and pelvis with an implant-specific software package, computer hardware tracks the precise positioning of the patient's leg and pelvis on an operating table, and the implant and surgeon's instruments, at all times during the procedure.

The computer computes all the information coming in from the patient and instruments, and enables the surgeon to determine where the precise replacement acetabular cup position should be.

Although computed tomography may enable less invasive surgery, the cost of utilising real time computed tomography during a hip or knee arthroplastic operation is prohibitively expensive. Furthermore, studies have shown that computed tomography assisted operations do not necessarily provide better results than traditional mechanical apparatus assisted operations.

It is therefore an aim of preferred embodiments of the present invention to provide an arthroplastic surgical apparatus which enables a surgeon to pre-determine the optimum position of a replacement acetabular cup in a prepared acetabular socket of a patient, but in which the surgeon may subsequently re-align the replacement * acetabular cup should initial positioning not be optimum.

Furthermore, it would be advantageous to provide an arthroplastic surgical apparatus in which a surgeon may insert a replacement femoral ball into a prepared acetabular socket, in order to determine optimum positioning of the replacement femoral ball, without the need for prior insertion of a fixed replacement acetabular cup into the prepared socket. It would be furthermore advantageous to provide an arthroplastic surgical apparatus which is relatively inexpensive to manufacture and sell compared to computed tomographical-based systems.

It is therefore an aim of preferred embodiments of the present invention to overcome or mitigate at least one problem in the prior art, whether expressly disclosed herein or not.

Summary of the invention

According to a first aspect of the invention there is provided an arthroplastjc surgical apparatus comprising a means to releasably mount a femoral ball, arranged in use to be demountably located in an acetabulum of an individual, and a means to enable marking of an acetabulum when the means to releasably mount the femoral ball is located in the acetabulum, in use.

By "femoral ball" we mean an anatomical femoral ball or a prosthetic femoral ball. By "acetabulum" we mean an anatomical acetabulum or an otherwise surgically prepared acetabulum, which may, for example, be an anatomical acetabulum which has been widened or which has had bone removed therefrom.

The means to releasably mount a femoral ball may comprise 2U* 61$: 20 a receptacle into which a femoral ball may be located. I...

The receptacle may comprise a cup. The cup may be substantially hemispherical or spherical cap-shaped. The cup may comprise a collar or flange extending outwardly around the peripheral edge of the cup. I. $2 22*

Suitably the apparatus comprises means to enable one of a S...

plurality of femoral balls of different sizes to be releasably mounted on the apparatus. The means to enable a plurality of femoral balls of different sizes to be releasably mounted on the apparatus may comprise means to adjust one or more dimensions of the means to releasably mount a femoral ball. The adjustment means may comprise a moveable portion of the means to releasably mount a femoral ball. When the means to releasably mount a femoral ball comprises a receptacle, suitably the adjustment means comprises means to adjust the cross- sectional area of the cavity of the receptacle. When the means to releasably mount a femoral ball comprises a cup, suitably the adjustment means comprises means to adjust the diameter of the cup.

In preferred embodiments the means to enable a plurality of femoral balls of different sizes to be releasably mounted on the apparatus may comprise one or more remote means to releasably mount a femoral ball, capable of being connected to the apparatus, the or each remote means being capable of releasably mounting a femoral ball of a different size. Suitably the means to releasably mount a femoral ball comprises a receptacle and the or each remote means comprises a receptacle having a cavity of different diameter. In preferred embodiments the means to *SS ** 20 releasably mount a femoral ball comprises a cup and the or each remote means to releasably mount a femoral ball . comprises a cup having a different diameter cavity. Thus if it is desired to releasably mount a femoral ball which is too small to be releasably mounted in the releasable mounting means of the apparatus, a suitable remote S...

S....' mounting means having the desired dimensions may be connected to the apparatus. In particularly preferred embodiments the releasable mounting means comprises a hemispherical or spherical-cap shaped cup and the or each remote mounting means comprise a hemispherical or sphericalcap shaped cup insert, having a cavity diameter smaller than the releasable mounting means, and which can be connected to the apparatus by stacking in the cavity of the releasable mounting means.

The apparatus may comprise a handle. The handle is preferably connected to the means to releasably mount a fernoral ball. The handle preferably comprises an elongate member. The elongate member may comprise a substantially straight elongate member, or may be curved or include a distal portion extending from the releasable mounting means and an angled portion extending from the distal end of the proximal portion.

The handle may be used to mount the apparatus in an acetabulum, and enable a user to remove the apparatus from the acetabulum after use. The handle is also useful for aligning the releasable mounting means in the acetabulum and mitigates or prevents the need for the user to directly contact the acetabulum.

The handle may be fixedly connected to the means to releasably mount a femoral ball, or may be releasably *S..

connected. The handle may be releasably connected by way of a suitable clip, for example. S. S * S S

* Preferably the means to enable marking of an acetabulum *SSS..

* when the means to releasably mount a femoral ball is located in the acetabulum comprises a means to enable marking of the acetabulum through the apparatus when the apparatus is mounted on the acetabulum. Preferably the marking means comprises one or more apertures in the apparatus. Suitably, the or each aperture enables a user of the apparatus to mark the acetabulum through the apertures in any suitable manner. Marking may be achieved by insertion of a suitable marking tool through the or each aperture. Suitable marking tools include tools capable of effecting visual indicia on the acetabulum.

Tools capable of effecting visual indicia on the acetabulum may include tools capable of printing or applying a visual indicia, such as a pen, printing device or the like for example, and tools capable of scoring or carving a visual indicia on the acetabulum, such as a knife, drill, blade, bore or awl, for example.

In preferred embodiments, the tool is a Kirchner wire or other pin which can be inserted through the apertures and protrude from the acetabulum to create a visual indicja.

Preferably there is a plurality of apertures in the apparatus, so that a plurality of marks may be made on the acetabulum.

Preferably the marking means are formed on the means to releasably mount a femoral ball. When the apparatus also comprises remote releasable mounting means, preferably the remote releasable mounting means also comprises marking *S..

means, which may be arranged to be aligned with or S...

superimposed on the marking means of the apparatus. S. S * . S

* Preferably the releasable mounting means, handle and S.....

* S remote releasable mounting means are constructed from materials which do not react adversely with biological tissue. Suitable materials include metals (including alloys) such as stainless steel and titanium, any composite materials, plastics materials and any combination thereof, for example.

Brief Description of the Drawings

For better understanding of the invention, and to show how embodiments of the same may be put into effect, the invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 illustrates a front perspective view of a first embodiment of an arthroplastic surgical apparatus of the invention; Figure 2 illustrates a side view of the arthroplastic surgical apparatus of Figure 1; Figure 3 illustrates an exploded, front perspective view of a second embodiment of an arthroplastic surgical apparatus of the invention; and Figure 4 illustrates a rear perspective view of the embodiment of the arthroplastic surgical apparatus shown in Figure 3.

*:* Description of the Preferred Embodiments S... S...

We refer firstly to Figures 1 and 2. A first embodiment of an arthroplastic surgical apparatus 2 of the invention comprises a means to releasably mount a femoral ball in the form of a hemispherical cup 4. The cup 4 comprises a cup wall 12, into which is rigidly fixed a plug 13 having *S..

a substantially hemispherical cavity 14 in the middle thereof. Running through the plug 13 and the wall 12 of the cup 4 are means to enable marking of an acetabulum when the apparatus is located on an acetabulum, in the form of apertures 10. The apertures 10 run through the wall of the plug 13, and the wall 12 of the cup 4, in alignment, so that a user may insert a desired tool through the apertures 10, from one side of the cup 4 through the other side.

Connected to the plug 13 of the cup 4 is a handle 6. The handle 6 comprises a proximal straight portion 16 at the distal end of which is a distal portion 18, angled at approximately 20 to the longitudinal axis of the proximal portion 16.

Use of the apparatus in Figures 1 and 2 will now be described.

In, for example, an operation to replace a diseased hip joint, the arthroplastjc surgical apparatus 2 can be utilised as follows. Firstly, a surgeon or other medical practitioner must prepare the acetabulum of a patient, and if necessary replace the femoral ball of the femur with a prosthetic femoral ball. After preparation of the acetabulum and femoral ball, the surgeon or medical practitioner needs to ensure that a replacement acetabular cup is positioned correctly in the prepared acetabulum, before the femoral ball or prosthetic femoral ball can be inserted into the replacement acetabular cup. In order to determine the correct placement for the acetabular cup and femoral ball, the surgeon or medical practitioner is :. required to locate the replacement acetabular cup in the * correct position before fixing it to the acetabulum. The surgeon or medical practitioner will firstly grasp the handle 6 of the arthroplastic surgical apparatus 2 by the distal portion 18, and locate the cup 4 over the prepared acetabulum. The cup 4 can then be located in the acetabulum in a rough position, and the surgeon or medical practitioner may then insert a femoral ball or prosthetic femoral ball into the cavity 14. In this position, the cup 4 is in the approximate position in which the replacement acetabular cup will be when it is fixed onto the acetabulum. The surgeon or medical practitioner then adjusts the positioning of the femora]. ball in the cavity 14, and at the same time may adjust the angle of the cup 4 in the prepared acetabulum, by moving the handle 6 in the desired direction. In this way, the surgeon or medical practitioner can determine the optimum angle of the cup 4 in the acetabulum, in order that the femoral ball or prosthetic femoral ball is positioned correctly in the acetabulum.

Once the surgeon or medical practitioner has determined the correct orientation and angle of the cup 4 in the acetabulum, he or she removes the femora]. ball or prosthetic femoral ball from the cavity 14. The surgeon or medical practitioner can then insert a marking tool into the apertures 10, such that at least a portion of the tool passes through the apertures 10 and marks the acetabulum below the apertures. The marking tool may be

SS

any suitable tool such as a tool which applies visible S...

indicia on the acetabulum, for example, Kirchner wires, *. pins, a pen or print head. Alternatively, the marking tool may be a device which cuts or scores visible indicia in the acetabulum, such as a blade, drill, knife, or the * 25 like. The surgeon or medical practitioner preferably SI..

marks visible indicia through all of the apertures 10, in order that a full set of reference points is visible on the acetabulum once the apparatus 2 has been removed away from the acetabulum.

When the surgeon or medical practitioner has marked visible indicia on the acetabulum through all of the apertures 10, the apparatus 2 can be removed from the acetabulum. The acetabulum is then left with visible iridicia corresponding to the correct position at which replacement acetabular cup should be located on the acetabulum. The surgeon or medical practitioner may then rigidly adhere a replacement acetabular cup into the prepared acetabulum by reference to the visible indicia on the prepared acetabulum.

We refer now to Figures 3 and 4 which illustrate a second preferred embodiment of an arthroplastic surgical apparatus 2 of the invention. Like numerals represent like components. In this embodiment, the cup 4 is a substantially hollow cup comprising a wall 12 defining a cavity 14. In this embodiment there is no plug rigidly connected within the wall 12. The wall 12 includes a plurality of apertures 10 corresponding to the means to enable marking of an acetabulum when the apparatus is located on an acetabulum. In this embodiment, the handle 6 is rigidly connected to the wall 12 of the cup 4. * S..

** In the embodiment shown in Figures 3 and 4, a remote means S..

20 to releasably mount the femoral ball is present in the *:*. form of insert 17. Insert 17 comprises a cavity 20 having a diameter smaller than that of the cavity 14 of the cup S.....

* 4. The cavity 20 is surrounded by a ledge 19, through which ledge extend a plurality of apertures 22. In use, the insert 17 is arranged to be inserted into the cavity 14 of the cup 4, such that the ledge 19 connects to the body 12 of the cup 4. In this way, the reduced diameter cavity 20 will present from the cup 4, in order for a femoral ball or prosthetic femoral ball of reduced diameter to be releasably mounted within the apparatus 2.

When the ledge 19 connects to the wall 12 of the cup 4, the apertures 22 of the insert 17 and the apertures 10 of the cup 4 align in order that the apertures run substantially through the cup 4 from the insert 17. Use of the apparatus 2 of Figures 3 and 4 without the insert 17 connected to the cup 4 is identical to the use described for the embodiment described in Figures 1 and 2.

If a surgeon or medical practitioner deems that a smaller femoral ball or prosthetic femoral ball is needed for a particular patient, the surgeon or medical practitioner can connect the insert 17 to the cup 4, so that the femoral ball or prosthetic femoral ball of reduced diameter may be releasably mounted in the reduced diameter cavity 20 of the insert 17, rather than the larger diameter cavity 14 of the cup 4. The surgeon or medical practitioner can then adjust the positioning of the cup 4 and femoral ball or prosthetic femoral ball as described for the embodiment shown in Figures 1 and 2. Finally, the surgeon or medical practitioner can mark the acetabulum to which the apparatus 2 is located in the same manner as described for the embodiment shown in Figures 1 and 2, *.S.

is.. 20 with the exception that the marking tool passes through *** the apertures 22 of the insert 17 and the apertures 10 of the cup body 12, before marking the acetabulum below the cup. * S

In alternative embodiments, instead of an insert 17, the apparatus 2 may be provided with a means to adjust the diameter of the cavity 14, in order to adjust the cross- sectional area of the cavity 14, in the form of moveable members such as moveable plates, for example, located on the wall 12. Thus if a surgeon or medical practitioner desired to releasably mount a femoral ball or prosthetic femoral ball in the cup 4, but the femoral ball or prosthetic femoral ball had a diameter too small to be mounted within the cavity 14, the surgeon or practitioner may adjust the diameter of the cavity 14 by moving the moveable plates as desired.

In other embodiments, the cup 4 may be replaced with any suitable receptacle. The receptacle may comprise a hemispherical member, or a member comprising a spherical cap shape. In other embodiments, the means to enable releasable mounting of a femoral ball may not comprise a receptacle but may comprise a gripping means, such as an elastic member, or the like. The gripping means may include apertures therethrough to enable marking of the acetabulum when the apparatus is located in an acetabulum.

In preferred embodiments, the apparatus 2 is constructed from a biocompatibje material, preferably a metal, composite, ceramic or plastics material. Suitable metals include stainless steel or titanium.

In preferred embodiments, the means to releasably mount the femoral ball comprise means which are shaped US..

substantially identically to the shape of a replacement SI..

acetabular cup to be inserted into the acetabulum of a patient. In most cases, the preferred shape will hemispherical or spherical cap shaped.

The handle 6 may be releasably connectable to the cup 4 in S. 5* order that a surgeon or medical practitioner may release the handle if it is obscuring his or her vision during positioning of the cup 4. The surgeon or medical practitioner may then reconnect the handle when desired.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extend to any novel one, or any novel combination, of the features disclosed S...

in this specification (including any accompanying claims, * *. abstract and drawings), or to any novel one, or any novel I.....

* . combination, of the steps of any method or process so disclosed. * S * a.. **.. * S *SSS

Claims

1. An arthroplastic surgical apparatus comprising a means to releasably mount a femoral ball, arranged in use to be demountably located in an acetabulum of an individual, and a means to enable marking of an acetabulum when the means to releasably mount the femoral ball is located in the acetabulum, in use.

2. An arthroplastic surgical apparatus as claimed in Claim 1 wherein the means to releasably mount a femoral ball comprises a substantially hemispherical-shaped cup or spherical cap-shaped cup.

3. An arthroplastic surgical apparatus as claimed in Claim 2 wherein the cup comprises a collar or flange extending outwardly around the peripheral edge of the cup.

4. An arthroplastic surgical apparatus as claimed in any one of Claims 1 to 3 wherein the apparatus comprises means to enable one of a plurality of femoral balls of different sizes to be releasably mounted on the apparatus.

5. An arthroplastjc surgical apparatus as claimed in Claim 4 wherein the means to enable a plurality of femoral balls of different sizes to be releasably mounted on the apparatus comprises means to adjust one or more dimensions of the means to releasably mount a femoral ball.

6. An arthroplastic surgical apparatus as claimed in Claim 4 or 5 wherein the means to enable a plurality of femoral balls of different sizes to be releasably mounted on the apparatus comprises one or more remote means to releasably mount a femoral ball, capable of being connected to the apparatus, the or each remote means being capable of releasably mounting a femoral ball of a different size.

7. An arthroplastic surgical apparatus as claimed in Claim 6 wherein the means to releasably mount a femoral ball comprises a receptacle and the or each remote means comprises a receptacle having a cavity of different diameter.

8. An arthroplastic surgical apparatus further comprising a handle.

9. An arthroplastic surgical apparatus as claimed in Claim 8 wherein a handle is connected to the means to releasably mount a femoral ball.

10. An arthroplastic surgical apparatus as claimed in any preceding claim wherein the means to enable marking of an acetabulum when the means to releasably mount a femoral ball is located in the acetabulum comprises a means to enable marking of the acetabulum through the apparatus when the apparatus is mounted on the acetabulum.

11. An arthroplastic surgical apparatus as claimed in Claim 9 wherein the marking means comprises one or more apertures in the apparatus.

12. An arthroplastic surgical apparatus as claimed in Claim 11 wherein the or each aperture enables a user of the apparatus to mark the acetabulurn through the aperture by insertion of a suitable remote marking tool through the or each aperture.

13. An arthroplastic surgical apparatus as claimed in Claim 12 wherein the marking tool is capable of effecting visual indicia on the acetabulum through the or each aperture.

14. An arthroplastjc surgical apparatus as claimed in any one of Claims 10 to 13 wherein there is a plurality of apertures in the apparatus, such that a plurality of marks may be made on the acetabulum.

15. An arthroplastic surgical apparatus substantially as described herein with reference to the accompanying drawings.