GB2422110A - Ligament saving knee prosthesis - Google Patents

Ligament saving knee prosthesis Download PDF

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Publication number
GB2422110A
GB2422110A GB0500781A GB0500781A GB2422110A GB 2422110 A GB2422110 A GB 2422110A GB 0500781 A GB0500781 A GB 0500781A GB 0500781 A GB0500781 A GB 0500781A GB 2422110 A GB2422110 A GB 2422110A
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GB
United Kingdom
Prior art keywords
tibia
portion
tray
insert
tibial
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0500781A
Other versions
GB0500781D0 (en
Inventor
Gursharan Singh Chana
Original Assignee
Gursharan Singh Chana
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gursharan Singh Chana filed Critical Gursharan Singh Chana
Priority to GB0500781A priority Critical patent/GB2422110A/en
Publication of GB0500781D0 publication Critical patent/GB0500781D0/en
Publication of GB2422110A publication Critical patent/GB2422110A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/38Joints for elbows or knees
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/38Joints for elbows or knees
    • A61F2/3859Femoral components
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2/38Joints for elbows or knees
    • A61F2/389Tibial components
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2002/30001Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30108Shapes
    • A61F2002/3011Cross-sections or two-dimensional shapes
    • A61F2002/30112Rounded shapes, e.g. with rounded corners
    • A61F2002/30131Rounded shapes, e.g. with rounded corners horseshoe- or crescent- or C-shaped or U-shaped
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02Prostheses implantable into the body
    • A61F2/30Joints
    • A61F2002/30001Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30316The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30329Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
    • A61F2002/30331Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit
    • A61F2002/3038Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit made by pushing a key or a peg into a mating slot or hole
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2220/00Fixations or connections for prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2220/0025Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
    • A61F2220/0033Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61FFILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0004Rounded shapes, e.g. with rounded corners
    • A61F2230/0013Horseshoe-shaped, e.g. crescent-shaped, C-shaped, U-shaped

Abstract

The invention provides a tibial tray 1, a tibial insert, and a femoral component that may be used in knee prostheses. The tibial tray 1 comprises a medial portion 2 and a lateral portion 3, and has a proximal face 6 and a distal face 7, wherein the tibial tray is shaped so as to define a channel 5 between the medial portion 2 and the lateral portion 3 that extends between the proximal face 6 and the distal face 7 and that is of a shape and size so as to allow the tray to be slid into position onto said tibia without being hindered by the presence of the cruciate ligaments. The tibial insert comprises a medial portion and a lateral portion, and has a proximal face and a distal face, wherein the tibial insert is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the insert to be slid into position onto a tibial tray that has been inserted onto a prepared tibia without being hindered by the presence of the cruciate ligaments. The femoral component comprises a medial portion and a lateral portion, and has a proximal face and a distal face, wherein the femoral component is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the insert to be slid into position onto a prepared femur without being hindered by the presence of the cruciate ligaments.

Description

KNEE PROSTHESES

The present invention relates to an improved knee prosthesis, and to improved total knee replacement methods.

Procedures for total knee replacement, which involve the removal of a thin layer of bone from the surface of both the tibia and the femur and the insertion of a prosthesis comprising a tibial component and a femoral component to replace the removed bearing surface, have been in existence for a number of years. However, in order to improve access to the joint area during surgery, in particular to provide sufficient clearance for insertion of the tibial component and the femoral component, current procedures require cruciate ligament sacrifice. Some total knee replacement procedures require sacrifice of both the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), which results in the stability of the knee being maintained only by the medial and lateral collateral ligaments together with the configuration of the prosthesis used.

Other current procedures allow retention of the posterior cruciate ligament (PCL), but nonetheless require the sacrifice of the anterior cruciate ligament (ACL).

In many cases the sacrificed cruciate ligament or ligaments are healthy.

Therefore it would be desirable to be able to maintain the cruciate ligaments in the knee.

Accordingly, there is a need for a total knee joint prosthesis and related method of total knee replacement whereby both the ACL and the PCL may be retained.

In accordance with a first aspect of the present invention, there is provided a tibial tray suitable for implantation in the knee joint, which tibial tray comprises a medial portion for location over the medial tibial condyle of a prepared tibia and a lateral portion for location over the lateral tibial condyle of said tibia and has a proximal face suitable for bearing a tibia! insert, and a distal face, opposite the proximal face, suitable for attachment to said tibia, wherein the tibia! tray is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the tray to be slid into position onto said tibia without being hindered by the presence of the cruciate ligaments.

The tibia! tray may be of one-piece construction or may comprise two or more pieces. In particular, the medial portion may be integral with the lateral portion or the medial portion and the lateral portion may be provided as separate pieces.

When the tibia! tray comprises separate medial and lateral portions, the medial and lateral portions may suitably be of different depths, that is the distance between the proximal face and the distal face is different for the medial portion and the lateral portion.

This is advantageous in that it allows the depths of the medial portion and the lateral portion to be independently chosen. Accordingly, the depth of the media! portion and the depth of the lateral portion can be chosen such that when the medial portion is located on the medial tibia! condyle of a prepared tibia and the lateral portion is located on the lateral tibia! condyle of said tibia the proximal face of the medial portion and the proximal face of the lateral portion lie in the same plane, even if the surfaces of the medial tibial condyle and the lateral tibia! condyle do not lie in the same plane. This allows the tibia to be prepared with minimal removal of bone, as only the bone on each of the medial tibial condyle and the lateral tibia! condy!e that actually needs removal due to degradation need be removed.

In contrast, in the prior art when single piece tibia! trays were used, if the media! tibial condyle and the lateral tibia! condyle differed in the amount that they had been worn or that the bone had degraded, healthy bone would need to be removed from one in order that the medial and lateral condyles were prepared to the same height, to provide a flat tibial surface upon which the tray could be located.

The channel defined between the medial portion and the lateral portion may be of any width and length provided that these dimensions permit the tray to be slid into position onto the tibia without being hindered by the presence of the cruciate ligaments. The depth of the channel is of course the distance between the proximal face and the distal face.

The channel suitably has a substantially constant cross section along its depth from the proximal face to the distal face. Suitably, the channel has a substantially rectangular cross section along its depth from the proximal face to the distal face.

In one embodiment, the tibia! tray comprises a neck portion that connects the medial portion and the lateral portion. In particular, the tibia! tray may be substantially horseshoe shaped, with the medial portion and lateral portion each forming an "arm" of the horseshoe.

The tray may be any suitable material for use in a prosthesis. For example, the tray may be a metal or metal alloy such as cobalt-chromium or titanium or may be a plastic such as polyethylene. In one embodiment, the tray is titanium.

The tibia! tray may be a trial tibia! tray or a definitive tibial tray.

If the tibia! tray is a trial tibial tray, it is suitably provided with one or more holes, with each hole extending from the proximal face to the distal face. Preferably the tray is provided with two or more holes, more preferably the tray is provided with one or more holes in the medial portion and one or more holes in the lateral portion, with each hole extending from the proximal face to the distal face. Accordingly, when the tray is located on the tibia a drill can be passed thorough the or each hole to drill a corresponding hole in the surface of the tibia below, which holes can be used in securing the definitive tray to the tibia. In one embodiment, the trial tibial tray is provided with three holes.

If the tibial tray is a definitive tibia! tray, it is suitably provided with one or more lugs, with the or each lug extending from the distal face away from the tray. Preferably the tray is provided with two or more lugs, more preferably the tray is provided with one or more lugs on the medial portion and one or more lugs on the lateral portion, each lug extending from the distal face away from the tray. Accordingly, when the tray is located on the tibia the lugs can be used to secure the tray onto the surface of the tibia below by location of the lugs in prepared holes on the tibial surface. In one embodiment, the definitive tibial tray is provided with three lugs.

In accordance with a second aspect of the present invention, there is provided a tibial insert suitable for implantation in the knee joint, which tibial insert comprises a medial portion for location over the medial tibial condyle of a tibia and a lateral portion for location over the lateral tibial condyle of said tibia and has a proximal face that is shaped to engage and articulate with a femoral component, and a distal face, opposite the proximal face, shaped to fit with the proximal face of a tibial tray, wherein the tibia! insert is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the insert to be slid into position onto a tibia! tray that has been inserted onto a prepared tibia without being hindered by the presence of the cruciate ligaments.

The tibia! insert may be of one-piece Construction or may comprise two or more pieces. In particular, the medial portion may be integral with the lateral portion or the medial portion and the lateral portion may be provided as separate pieces.

The channel may be of any width and length provided that these dimensions permit the insert to be slid into position onto the tibial tray without being hindered by the presence of the cruciate ligaments. The depth of the channel is of course the distance between the proximal face and the distal face.

The channel suitably has a substantially constant cross section along its depth from the proximal face to the distal face. Suitably, the channel has a substantially rectangular cross section along its depth from the proximal face to the distal face.

In one embodiment, the tibia! insert comprises a neck portion that connects the medial portion and the lateral portion. In particular, the tibia! insert may be horseshoe shaped, with the media! portion and lateral portion each forming an "arm" of the horseshoe.

The insert may be any suitable material for use in a prosthesis. For example, the insert may be a metal or metal alloy such as cobalt- chromium or titanium or may be a plastic such as polyethylene. In one embodiment the insert is ultra high molecular weight polyethylene.

The tibial insert may be a trial tibial insert or a definitive tibial insert.

The tibia! insert suitably has a curved proximal face to allow for engagement and articulation with a femoral component. In a preferred embodiment, the medial portion of the proximal face is curved and the lateral portion of the proximal face is curved. Preferably, the medial portion of the proximal face is curved both from front to back and from side to side. The lateral portion of the proximal face is preferably curved both from front to back and from side to side. The curvature of the medial portion of the proximal face is preferably concave. Preferably, the curvature of the lateral portion of the proximal face is concave.

Preferably both the lateral portion and the medial portion of the proximal face is curved from both front to back and side to side, as this means that articulation of the tibial insert with a femoral component is possible in both the autro posterior and the lateral planes of the knee. This clearly allows for improved movement of the prosthetic knee.

In accordance with a third aspect of the present invention, there is provided a tibia! component of a prosthesis suitable for implantation in the knee joint, which tibia! component comprises (i) a tibial tray in accordance with the first aspect and (ii) a tibia! insert in accordance with the second aspect, wherein the distal face of the tibial insert is shaped to fit against and articulate with the proximal face of the tibia! tray.

The present invention further provides, in a fourth aspect, a femoral component suitable for implantation in the knee joint, which femoral component comprises a medial portion for location over the medial femoral condyle of a femur and a lateral portion for location over the lateral femoral condyle of said femur and has a proximal face that is shaped to engage and articulate with a tibial insert, and a distal face, opposite the proximal face, suitable for attachment to said femur, wherein the femoral component is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the insert to be slid into position onto a prepared femur without being hindered by the presence of the cruciate ligaments.

The femoral component may be of one-piece construction or may comprise two or more pieces. In particular, the medial portion may be integral with the lateral portion or the medial portion and the lateral portion may be provided as separate pieces.

The channel may be of any width and length provided that these dimensions permit the insert to be slid into position Onto the femur without being hindered by the presence of the cruciate ligaments. The depth of the channel is of course the distance between the proximal face and the distal face.

In one embodiment, the femoral component comprises a neck portion that connects the medial portion and the lateral portion. In particular, the femoral component may be substantially horseshoe shaped, with the medial portion and lateral portion each forming an "arm" of the horseshoe.

The component may be any suitable material for use in a prosthesis. For example, the component may be a metal or metal alloy such as cobaltchromium or titanium or may be a plastic such as polyethylene. In one embodiment the femoral component is cobalt-chromium.

The femoral component may be a trial femoral component or a definitive femoral component The femoral component is preferably curved so as to allow for engagement and articulation with a tibial insert and to allow for attachment to the femoral surface. In particular, the femoral component may be curved both from front to back and from side to side. The curvature of the femoral component is suitably convex. Preferably, the femoral component is curved such that it has a substantially C shaped cross section.

It is advantageous for the femoral component to be curved from both front to back and side to side, as this means that articulation of the femoral component with a tibial insert is possible in both the autro posterior and the lateral planes of the knee. This clearly allows for improved movement of the prosthetic knee.

The invention also provides, in a fifth aspect, a prosthesis suitable for implantation in the knee joint, which comprises a tibial component in accordance with the third aspect and a femoral component in accordance with the fourth aspect.

The invention further provides, in a sixth aspect, a method of total knee replacement, which method comprises: removing the proximal tibial surface except for a rectangular block of bone surrounding the anterior cruciate ligament tibial insertion and bone posterior to this leading up to the posterior cortex of the tibia; inserting a tibial tray in accordance with the first aspect described above; and inserting a tibial insert in accordance with the second aspect described above.

Such a method is advantageous, as it does not require the sacrifice of the anterior or posterior cruciate ligament.

The method may suitably further comprise the step of: inserting a femoral component in accordance with the fourth aspect described above.

Optionally, the method may comprise the step of: inserting a patella component.

Preferably, the method comprises: removing the proximal tibia! surface except for a rectangular block of bone surrounding the anterior cruciate ligament tibia! insertion and bone posterior to this leading up to the posterior cortex of the tibia; inserting a trial tibial tray in accordance with the first aspect described above; inserting a trial tibia! insert in accordance with the second aspect described above; inserting a trial femoral component in accordance with the fourth aspect described above; testing the trial implants; inserting a definitive tibia! tray in accordance with the first aspect described above; inserting a definitive tibial insert in accordance with the second aspect described above; and inserting a definitive femoral component in accordance with the fourth aspect described above.

A specific embodiment of the present invention will now be described, by means of example only, with reference to the drawings, in which: Figure 1 is a perspective view of a trial tibia! tray in accordance with the invention; Figure 2a is a view from above of a tibial insert in accordance with the invention; Figure 2b is a cross section through line A-A of the insert shown in Figure 2a; Figure 2c is a cross section through line B-B of the insert shown in Figure 2a; Figure 3 is a perspective view of a definitive tibia! tray in accordance with the invention; Figure 4a is a view from above of a femoral component in accordance with the invention; and Figure 4b is a side view of the femoral component shown in Figure 4a.

Figure 1 shows a trial tibia! tray 1 which is horseshoe shaped, having two arms 2, 3 linked by a neck portion 4 and defining a channel 5. One of the arms of the horseshoe shape is a medial portion 2 for location over the medial tibia! condyle of a prepared tibia and the other of the arms is a lateral portion 3 for location over the lateral tibial condyle of said tibia.

The tray 1 has a proximal face 6 suitable for bearing a tibia! insert, and a distal face 7, opposite the proximal face, suitable for attachment to said tibia.

The channel 5 defined between the medial portion 2 and the lateral portion 3 extends between the proximal face 6 and the distal face 7 and is rectangular in cross section along its depth. The channel is sized so as to allow the tray 1 to be slid into position onto a prepared tibia without being hindered by the presence of the cruciate ligaments.

The width "a" of the neck 4, from channel 5 to the outer edge of the tray 1, is 2cm.

The tray 1 is provided with three holes 8, with each hole extending from the proximal face 6 to the distal face 7. One hole is located towards the centre of the medial portion 2, one hole is located towards the centre of the lateral portion 3, and one hole is located towards the centre of the neck 4.

Figures 2a-c shows a tibia! insert 11 which is horseshoe shaped, having two arms 12, 13 linked by a neck portion 14 and defining a channel 15.

One of the arms of the horseshoe shape is a medial portion 12 for location over the medial tibia! condyle of a prepared tibia and the other of the arms is a lateral portion 13 for location over the lateral tibia! condyle of said tibia.

The insert 11 has a proximal face 16 that is shaped to engage and articulate with a femoral component, and a distal face 17, opposite the proximal face, shaped to fit with the proximal face of a tibial tray.

The channel 15 defined between the medial portion 12 and the lateral portion 13 extends between the proximal face 16 and the distal face 17 and is rectangular in cross section along its depth. The channel 15 is sized so as to allow the insert 11 to be slid into position onto a tibia! tray located on a prepared tibia without being hindered by the presence of the cruciate ligaments.

The width "b" of the neck 14, from channel 15 to the outer edge of the insert 11, is 2cm.

The proximal face 16 is curved so as to facilitate engagement and articulation with a femoral component. The medial portion of the proximal face is curved from back to front and from side to side, with the curvature being concave. The lateral portion of the proximal face has the same curvature, also being curved from back to front and from side to side, with the curvature being concave.

Figure 3 shows a definitive tibial tray 21. The tray 21 is horseshoe shaped, having two arms 22, 23 linked by a neck portion 24 and defining a channel 25. One of the arms of the horseshoe shape is a medial portion 22 for location over the medial tibial condyle of a prepared tibia and the other of the arms is a lateral portion 23 for location over the lateral tibial condyle of said tibia.

The tray 21 has a proximal face 26 suitable for bearing the tibial insert 11, and a distal face 27, opposite the proximal face, suitable for attachment to said tibia.

The channel 25 defined between the medial portion 22 and the lateral portion 23 extends between the proximal face 26 and the distal face 27 and is rectangular in cross section along its depth. The channel 25 is sized so as to allow the tray 21 to be slid into position onto a prepared tibia without being hindered by the presence of the cruciate ligaments.

The width "c" of the neck 24, from channel 25 to the outer edge of the tray 21, is 2cm.

The tray 21 is provided with three tugs 28 extending from the distal face 27 away from the tray 21. One lug is located on the medial portion 22, one lug is located on the lateral portion 23, and one lug is located on the neck 24.

Figures 4a and 4b show femoral component 31 which is horseshoe shaped, having two arms 32, 33 linked by a neck portion 34 and defining a channel 35. One of the arms of the horseshoe shape is a medial portion 32 for location over the medial femoral condyle of a femur and the other of the arms is a lateral portion 33 for location over the lateral femoral condyle of said femur.

The femoral component 31 has a proximal face 36 that is shaped to engage and articulate with the tibial insert 11, and a distal face 37, opposite the proximal face, suitable for attachment to said femur.

The femoral component 31 is curved from front to back and from side to side, with the curvature being convex. The cross section of the femoral component 31 is C shaped, as can be seen in Figure 4b.

The channel 35 defined between the medial portion 32 and the lateral portion 33 extends between the proximal face 36 and the distal face 37.

The channel 35 is sized so as to allow the femoral component 31 to be slid into position onto a prepared femur without being hindered by the presence of the cruciate ligaments.

The femoral component 31 is provided with a lug 38 extending from the distal face 37 away from the component 31. The lug 38 is located on the neck 34.

Procedure Insall surgical approach is used. The knee joint is exposed such that the distal femur and the proximal tibia are exposed with eversion and lateral displacement of the patella. The soft tissue of the anterior distal aspect of femur is removed to expose the distal aspect of the femur.

A power intra-medullary drill is used to make a hole in the distal aspect of the femur such that the intra-medullary drill lies in the middle of the femoral canal, both in the antro-posterior and medio-lateral planes. An intra-medullary rod is inserted into the intra-medullary canal. A femoral jig is attached to the distal end of the intra-medullary rod with a 5 or 7 or 9 degrees valgus setting. A primary or plus 4mm distal femoral cut is then made.

A femoral sizing jig is applied and anteriorly referenced to prevent anterior femoral notching. Three degrees external rotation is applied.

Two lugholes are drilled: one in the medial aspect and one in the distal aspect of the femoral cut. The sizing jig is removed and the distal femoral jog is secured into the lugholes and anterior, posterior and champher. A patella groove of the femur is also cut using a patella groove-cutting rig.

A tibial extra-medullary is applied to make the tibial cuts. The long axis of the jig is positioned in line with the tibial crest and the tibia! tuberosity. The proximal tibial cutting block is applied to the longitudinal bar such that minimal tibial resection is carried out. The tibial cutting block allows removal of the whole of the proximal tibia! surface but sparing a rectangular block of bone surrounding the ACL tibial insertion and bone posterior to this up to the posterior cortex of the tibia.

Once the proximal tibia! cut is completed, the proximal tibial surface is left with a flat smooth surface except for the untouched, raised bone surrounding the ACL tibial insertion and bone anterior to this up to the anterior cortex.

The tibial trial tray 1 is inserted onto the prepared proximal tibia! surface and lugholes are made in the surface through the holes 8 in the tray.

These lugholes are for the fixation of the definitive tibia! tray 21 onto the proximal tibia! surface using its!ugs 18. The appropriate sized trial tibia! insert 11 is secured on the tibia! tray.

A trial femora! component 31 is inserted onto the femoral surface with the knee in hyper flexion. The knee is then straightened and joints tested for ligament stability, in relation to both the collaterals and the cruciates. A ligament balance test is then carried out. The patel!a surface is prepared and a pate!la trial component (as known in the art) is inserted. The joint is then tested for pate!la tracking.

If all the trial implants are satisfactory, definitive implants are cemented in place, starting with the tibia! tray 21 and tibia! imp!ant 11, then the femora! component 31 with the pate!la component (not shown).

Claims (26)

1. A tibial tray suitable for implantation in the knee joint, which tibia! tray comprises a medial portion for location over the medial tibial condyle of a prepared tibia, and a lateral portion for location over the lateral tibia! condyle of said tibia, and has a proximal face suitable for bearing a tibia! insert, and a distal face, opposite the proximal face, suitable for attachment to said tibia, wherein the tibia! tray is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the tray to be slid into position onto said tibia without being hindered by the presence of the cruciate ligaments.
2. The tibia! tray according to Claim 1 wherein the tray comprises two or more pieces.
3. The tibial tray according to Claim 2, wherein the medial portion and the lateral portion are provided as separate pieces.
4. The tibial tray according to Claim 3, wherein the medial and lateral portions are of different depths.
5. The tibia! tray according to any one of the preceding claims, wherein the channel defined between the medial portion and the lateral portion has a substantially constant cross section along its depth from the proximal face to the distal face.
6. The tibia! tray according to any one of the preceding claims, wherein the tibia! tray comprises a neck portion that connects the media! portion and the lateral portion.
7. The tibial tray according to Claim 6, wherein the tibial tray is substantially horseshoe shaped.
8. A tibia! insert suitab!e for implantation in the knee joint, which tibial insert comprises a medial portion for location over the media! tibial condyle of a tibia, and a lateral portion for location over the lateral tibial condyle of said tibia, and has a proximal face that is shaped to engage and articu!ate with a femoral component, and a dista! face, opposite the proximal face, shaped to fit with the proximal face of a tibia! tray, wherein the tibial insert is shaped so as to define a channe! between the medial portion and the lateral portion that extends between the proximal face and the dista! face and that is of a shape and size so as to al!ow the insert to be slid into position onto a tibia! tray that has been inserted onto a prepared tibia without being hindered by the presence of the cruciate ligaments.
9. The tibia! insert according to Claim 8, wherein the channel defined between the medial portion and the latera! portion has a substantially constant cross section along its depth from the proxima! face to the dista! face.
10. The tibia! insert according to Claim 8 or Claim 9 wherein the tibia! insert comprises a neck portion that connects the media! portion and the 25!ateral portion.
11. The tibial insert according to Claim 10 wherein the tibial insert is horseshoe shaped.
12. The tibial insert according to any one of Claims 8 to 11 wherein the tibia! insert has a curved proximal face to allow for engagement and articulation with a femoral component.
13. The tibial insert according to Claim 12 wherein the medial portion of the proximal face is curved and the lateral portion of the proximal face is curved.
14. The tibial insert according to Claim 12 or Claim 13 wherein the medial portion of the proximal face is curved both from front to back and from side to side.
15. The tibia! insert according to any one of Claims 12 to 14 wherein the lateral portion of the proximal face is curved both from front to back and from side to side.
16. The tibia! insert according to any one of Claims 12 to 15 wherein the curvature of the medial portion of the proximal face is concave.
17. The tibia! insert according to any one of Claims 12 to 16 wherein the curvature of the lateral portion of the proximal face is concave.
18. A tibia! component of a prosthesis suitable for implantation in the knee joint, which tibial component comprises (i) a tibia! tray in accordance with any one of Claims 1 to 7 and (ii) a tibia! insert in accordance with any one of Claims 8 to 17, wherein the distal face of the tibia! insert is shaped to fit against and articulate with the proximal face of the tibia! tray.
19. A femoral component suitable for implantation in the knee joint, which femoral component comprises a medial portion for location over the medial femoral condyle of a femur, and a lateral portion for location over the lateral femoral condyle of said femur, and has a proximal face that is shaped to engage and articulate with a tibial insert, and a distal face, opposite the proximal face, suitable for attachment to said femur, wherein the femoral component is shaped so as to define a channel between the medial portion and the lateral portion that extends between the proximal face and the distal face and that is of a shape and size so as to allow the insert to be slid into position onto a prepared femur without being hindered by the presence of the cruciate ligaments.
20. The femoral component according to Claim 19 wherein the femoral component comprises a neck portion that connects the medial portion and the lateral portion.
21. The femoral component according to Claim 20 wherein the femoral component is substantially horseshoe shaped.
22. The femoral component according to Claim 20 or Claim 21 wherein the femoral component is curved so as to allow for engagement and articulation with a tibial insert and to allow for attachment to the femoral surface.
23. The femoral component according to Claim 22 wherein the femoral component is curved both from front to back and from side to side.
24. The femoral component according to Claim 22 or Claim 23 wherein the curvature of the femoral component is convex.
25. The femoral component according to any one of Claims 22 to 24 wherein the femoral component is curved such that it has a substantially C shaped cross section.
26. A prosthesis suitable for implantation in the knee joint, which comprises a tibia! component in accordance with Claim 18 and a femora! component in accordance with any one of Claims 19 to 25.
GB0500781A 2005-01-14 2005-01-14 Ligament saving knee prosthesis Withdrawn GB2422110A (en)

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Application Number Priority Date Filing Date Title
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GB2422110A true GB2422110A (en) 2006-07-19

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8900316B2 (en) 2010-01-29 2014-12-02 Smith & Nephew, Inc. Cruciate-retaining knee prosthesis

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1383474A (en) * 1972-02-08 1974-02-12 New York Society Prosthetic knee-joint
US4309778A (en) * 1979-07-02 1982-01-12 Biomedical Engineering Corp. New Jersey meniscal bearing knee replacement
US5935173A (en) * 1995-02-03 1999-08-10 Cryptych Pty Ltd Knee prosthesis
US20040102852A1 (en) * 2002-11-22 2004-05-27 Johnson Erin M. Modular knee prosthesis
US20040138755A1 (en) * 1999-06-16 2004-07-15 Btg International Limited Tibial component

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1383474A (en) * 1972-02-08 1974-02-12 New York Society Prosthetic knee-joint
US4309778A (en) * 1979-07-02 1982-01-12 Biomedical Engineering Corp. New Jersey meniscal bearing knee replacement
US5935173A (en) * 1995-02-03 1999-08-10 Cryptych Pty Ltd Knee prosthesis
US20040138755A1 (en) * 1999-06-16 2004-07-15 Btg International Limited Tibial component
US20040102852A1 (en) * 2002-11-22 2004-05-27 Johnson Erin M. Modular knee prosthesis

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8900316B2 (en) 2010-01-29 2014-12-02 Smith & Nephew, Inc. Cruciate-retaining knee prosthesis

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