US20050171612A1

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Publication number: US20050171612A1
Application number: US11/089,826
Authority: US
Inventors: Lindsey Rolston
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-02-20
Filing date: 2005-03-25
Publication date: 2005-08-04
Also published as: US20040167630A1; US6916341B2

Abstract

Disclosed is a device and method of bicompartmental arthroplasty of the knee. The device permits arthroplasty of the medial or lateral and patellofemoral compartments of the knee while leaving the opposite compartments and the anterior and posterior cruciate ligaments intact. The device provides a femoral prosthesis component that includes a trochlear surface and a tibial prosthesis component which can be secured to the tibia. The femoral component is essentially “u” shaped having an anterior leg upon which the trochlear surface is positioned and a posterior leg which engages the posterior surface of the distal end of the femur. The femoral component also has a convex articulating surface which engages a concave articulating surface of the tibial prosthesis component to approximate the articulation of a healthy knee. The patellar prosthesis is applied to the posterior surface of the patella and articulates with the trochlear exterior surface of the femur.

Description

PRIORITY INFORMATION

This application is a divisional application of application Ser. No. 10/370,002, titled DEVICE AND METHOD FOR BICOMPARTMENTAL ARTHROPLASTY, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a device and method for bicompartmental arthroplasty for resurfacing of either the medial joint and the patellofemoral joint of the knee or the lateral and patellofemoral joint of the knee in order to treat the pain associated with arthritis. The present device and method resurfaces either the medial or lateral joints depending on which compartment is diseased, but does not resurface both the lateral (outside) and medial (inside) compartment of the knee at the same time.

BACKGROUND OF THE INVENTION

Total knee joint replacement (arthroplasty) is a common and very successful surgery for people with degenerative arthritis (osteoarthritis) of the knee. Over 450,000 patients a year in the United States undergo total knee replacement surgery. Total knee replacement puts an artificial surface on all parts of the knee joint that contact each other as the knee bends. The damaged cartilage is removed, a small amount of bone is removed, the knee implant is attached to the distal end of the femur and proximal end of the tibia, and the patella is resurfaced if necessary. The implant typically is made of metal and plastic and provides an artificial articulating surface which causes no pain to the patient. Unfortunately total knee replacement results in sacrifice of the anterior and posterior cruciate ligaments.

More recently, unicompartmental knee arthroplasty has been utilized where there is arthritic damage to only a single compartment of the knee and no damage to the other compartments. The inside (medial) component (medial tibial plateau and the medial femoral condyle) is most commonly involved and replaced using unicompartmental arthroplasty. However, occasionally, the outside (lateral) compartment (the lateral tibial plateau and the lateral femoral condyle) is sometimes involved and must be replaced. Also the knee cap, i.e., the patellofemoral compartment (the patella and femoral trochlear notch) may also develop osteoarthritis. Heretofore, if more than a single compartment of the knee had arthritic disease, total knee replacement was the only available treatment. The present invention provides a device and method for bicompartmental arthroplasty which permits the resurfacing of the medial and patellofemoral joints of the knee or the

lateral and patellofemoral joints without the necessity for resurfacing of the opposite compartment of the knee or the sacrifice of the anterior or posterior cruciate ligaments.

BRIEF DESCRIPTION OF THE INVENTION

A device for bicompartmental arthroplasty of a patient's knee in accordance with the present invention comprises a femoral prosthesis component configured to resurface the patellofemoral and one other compartment of the knee i.e., either the medial compartment or the lateral compartment depending on which compartment is diseased. The femoral prosthesis component has a first internal surface configured to be secured to a surgically prepared distal end of the one other compartment of the patient's femur so that the anterior and posterior cruciate ligaments remain intact. The femoral prosthesis component also has a second exterior convex curved surface positioned and configured to replicate a femoral condyle for that compartment and a concave trochlea surface positioned and configured to articulate with the patella. The device also comprises a tibial prosthesis component configured for the one other compartment of the knee having a first interior surface configured to be secured to a surgically prepared proximal end of the one other compartment of the patient's tibia and a second concave curved exterior surface configured to receive the second convex curved surface of the femoral prosthesis component to permit pivotal articulation between said femoral prosthesis component and the tibial prosthesis component, approximating the articulation of a healthy knee joint.

A method of performing bicompartmental arthroplasty of a patellofemoral and one other compartment of a patient's knee comprises the steps of making an incision along the anterior aspect of the one other compartment of the knee, excising the remnants of the meniscus of the one other compartment, surgically preparing a proximal end of the one other compartment of the patient's tibia to receive a tibial prosthesis component in a manner so as to preserve the integrity of the anterior and posterior cruciate ligaments. The tibial prosthesis component has a first surface configured to be secured to the surgically prepared one other compartment of the proximal end of the tibia and a second concave curved surface. Next the patella is rotated approximately 90 degrees. The distal end of the one other compartment of a the patient's femur is surgically prepared to receive a femoral prosthesis component. The femoral prosthesis component has a concave trochlea surface and a first surface configured to be secured to the surgically prepared one other compartment of the distal end of the femur. The femoral component also has a second convex curved surface configured to replicate the condyle and articulate with the second concave curved surface of the tibial prosthesis component to permit pivotal articulation between the femoral prosthesis component and the tibial prosthesis component in a manner approximating the articulation of a healthy knee joint. The femoral component is next secured to the femur and the tibial component is secured to the tibia. The patella is positioned over the concave trochlea surface of the femoral prosthesis component and the incision is closed.

If the patella is also diseased, the method also comprises the additional steps of surgically preparing a posterior surface of the patient's patella to receive a patella prosthesis component having a first surface configured to be secured to the surgically prepared posterior surface of the patella, and a convex curved second surface configured to engage the concave trochlea surface of the femoral prosthesis component, and securing the patella prosthesis component to the patella.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of the articular surface of a medial femoral prosthesis component in accordance with the present invention.

FIG. 1B is a side view of the medial femoral prosthesis component ofFIG. 1.

FIG. 2 is a front view of the medial femoral prosthesis component ofFIG. 1 and a medial tibial prosthesis component of the present invention as surgically implanted on a human knee.

FIG. 3 is a rear view of a device for bicompartmental arthroplasty of the knee in accordance with the present invention as surgically implanted on a human knee.

FIG. 4 is a front view of a device for bicompartmental arthroplasty in accordance with the present invention as implanted on a human knee showing the position of the patella on the device.

FIG. 5 is a front view of a human knee flexed 90° showing the medial femoral prosthesis component and the medial tibial prosthesis component implanted on the knee.

FIG. 6 is a lateral side view of a knee showing the positioning of the patella and a patella prosthesis component.

FIG. 7 is a side view of a patella component that may be used in conjunction with the present invention.

FIG. 8 is a side view of one type of medial tibial prosthesis component for use in connection with the present invention.

FIG. 9 is an upper side perspective view of the prosthesis ofFIG. 8.

FIG. 10 is an upper side perspective view of an alternative medial tibial prosthesis component that may be used in connection with the present invention.

FIG. 11 is a side view of the prosthesis shown inFIG. 10.

FIG. 12 is a front view of an alternative embodiment of the present invention for the lateral compartment of the knee as implanted on a human knee.

FIG. 13 is a rear view of the embodiment ofFIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and B illustrate a medialfemoral prosthesis component10 for use in connection with a combination device for bicompartmental arthroplasty of the knee. Theprosthesis10 is essentially unshaped with one leg of the “u” forming the anterior (front)portion20 of the prosthesis and the other leg of the “u” forming the posterior (rear)portion22 of the prosthesis and abase portion21 connecting the anterior and

posterior portions

20 and22. The medialfemoral prosthesis component10 has an interiorfirst surface12 which is configured to be secured to a surgically prepared portion of the distal end of the medial compartment of thefemur26 as shown inFIG. 2 as will be described in more detail below. Theexterior surface14 ofcomponent10 has a concavetrochlear groove16 formed on the anterior surface of theleg20 ofprosthesis component10. A convexsecond surface18 is formed on the medial side of thebase portion21 ofprosthesis10 and is configured to replicate the medial femoral condyle of the knee. Apost13 is mounted to theinterior surface12 ofbase portion21 and extends essentially perpendicularly from that surface.Post13 is inserted into a hole drilled in the femur during surgical preparation to aid in securing thecomponent10 to thefemur26. More than onepost13 could be mounted todevice10 as necessary.

With reference toFIG. 2, theprosthesis component10 is shown in position as it would be on the distal end of thefemur26 of the human knee. Theanterior leg20 of the “u” shapedmedial component10 is positioned over a surgically prepared anterior surface of thefemur26. With reference toFIG. 3, theposterior leg portion22 ofmedial component10 extends upwardly along the posterior surface of a surgically prepared medial compartment of the distal end of thefemur26. The interiorfirst surface12 can be textured to facilitate attachment to the femur using a cement or it may have a bone ingrowth surface applied so that the bone will grow into the ingrowth surface thereby securingcomponent10 to the femur. Prior to implanting, the distal end of thefemur26 is surgically prepared to remove the diseased portions of the distal end of the femur and the remnants of the medial meniscus are excised or removed. The distal end of the femur is then cut to mate with theinterior surface12 ofcomponent10 and a hole is drilled to accommodatepost13. Alternately, a second hole may be drilled to accommodate a second post or a keel punch may be used to prepare for a keel in place of the post to secure rotation of the femoral implant.

With reference toFIG. 2, a medialtibial prosthesis component28 is shown secured to a surgically prepared portion of the proximal end of the tibia. With reference toFIGS. 8 and 9, themedial tibial component28 has a firstflat surface30 and a secondconcave surface32. Theconcave surface32 of themedial tibial component28 is configured to articulate with the convex second surface of the medialfemoral component10.Flat surface30 has apost31 extending perpendicularly from that surface and is configured and adapted to be secured to a surgically prepared portion of the medial compartment of thetibia34.Flat surface30 can be textured to facilitate attachment by cement or it can have a bone ingrowth surface applied so that the bone will grow into the ingrowth surface thereby securing thecomponent28 to the tibia. As illustrated inFIGS. 2 and 3, a portion of the tibial plateau is surgically removed so that themedial component28 can be attached. Themedial tibial component28 illustrated inFIGS. 8 and 9 is comprised entirely of a plastic material that is biomedically compatible with the human body.

FIGS. 10 and 11 illustrate an alternative embodiment of a medial tibial prosthesis component for use in connection with the present invention. TheFIG. 10 and11 component comprises a flatmetallic base36 to which aplastic insert38 with aflat base37 and a concaveupper surface39 is attached either rigidly to or to allow rotation or movement upon the fixedbase plate37. Theplastic insert38 can be formed of the same plastic materials ascomponent28 illustrated inFIGS. 8 and 9.Metal base portion36 has a flatfirst surface40 and a downwardly extendingflange42 along one edge which is designed and configured to extend into a corresponding groove cut into the posterior surface of the tibia so as to aid in securingbase section36 to the tibia.Surface40 can either be textured to aid in securingbase portion36 to the tibia using a cement, or a bone ingrowth surface can be applied to surface40 so thatbase portion36 can be secured to the tibia by bone growth into the bone ingrowth surface.

It can be appreciated fromFIGS. 2, 3 and5 that the lateral compartment of the knee remains in its natural state due to the fact thatdevice10 is affixed only to the medial compartment of the knee. Consequently, the anterior and posterior

cruciate ligaments

70 and72 remain intact and are not compromised by thedevice10 or its implantation.

With reference toFIGS. 4 and 6,patella50 is shown in its normal position in thetrochlear groove16 of medialfemoral component10. Thepatellar tendon52 covers the patella and is attached at oneend54 to the anterior surface of the tibia and theother end56 to the quadriceps muscle (not shown). Contraction of the quadriceps muscles pulls the patella through the trochlear groove, thereby lifting the tibia.

If there is arthritic disease of the patella, it may be necessary to replace the diseased posterior surface of the patella with a plastic prosthesis component. With reference toFIG. 6,patella50 is shown in dotted lines under thepatellar tendon52. Also shown in dotted lines is apatellar component58 as it would be positioned in a surgically prepared posterior surface of thepatella50. With reference toFIG. 7, a side view of apatella prosthesis component58 is shown.Patella component58 is configured to have aconvex surface60 configured and dimensioned to engage and articulate in thetrochlea surface16 of the medialfemoral prosthesis component10.Patellar insert component58 also comprises asurface62 which includes apost64 configured and adapted to be secured to a surgically prepared posterior surface of the patella.

As discussed above, theinterior surface12 offemoral component10 can either be configured to be secured to the femur by the use of a cement, or a bone ingrowth surface may be applied to theinterior surface12 so that the femur bone will grow into and more permanently secure the femoral component to the femur. Such bone ingrowth surfaces are well-known in the art and have previously been used in connection with both unicompartmental and full knee replacement prosthesis. Similarly, the medialtibial prosthesis component28 can either be secured to the tibia by use of a cement or also by the use of a bone ingrowth surface applied to the tibial component so that the bone structure of the tibia will grow into the bone ingrowth surface to more permanently secure the tibial component to the tibia.

With reference toFIGS. 3 and 5, it can be seen that the present invention can be implanted in the knee without disturbing or damaging the middle third of the knee joint where the anteriorcruciate ligament70 and the posteriorcruciate ligament72 are located. Thus, the present invention allows a bicompartmental knee arthroplasty that preserves the integrity of the anterior and posterior cruciate ligaments.

To implant theFIG. 1-4 embodiment in a patient, a 3 to 4 inch longitudinal incision is made on the anterior aspect of the knee from the medial aspect of the patellar tendon 1 centimeter below the joint line extending approximately 3 to 4 inches in a vertical fashion. The incision is opened along the length of the incision with a medial parapatellar arthrotomy extending in a minimal fashion into the quadriceps femoris muscle medially. Alternately, a mid vastus or mini mid vastus or trivector approach may be employed to arthrotomize the knee joint. The remnants of the medial meniscus are excised. A portion of the fat pad is excised with care being taken to preserve the integrity of the anterior and posterior cruciate ligaments.

Surface cuts are made on the medial tibial articular surface using the technology previously employed by the Accuris® unicompartmental arthroplasty of Smith and Nephew Orthopedics, Inc. Alternately, intramedullary or extramedullary alignment guides can be employed to guide the medial tibial cuts. After the tibial cut is made, the patella is subluxed or rotated 90°. The intramedullary canal at the distal end of the femur is exposed using a ⅜ inch drill bit. An intramedullary rod is inserted into the distal femur until a distal femoral cutting block is flush against the distal medial femur. A distal femoral cutting block of the appropriate angle is attached after the cutting block is pinned in place, the distal femoral cut is made with an oscillating saw. The jig is removed and a sizing block is placed against the distal femur in order to reference the posterior femoral condyles. A stylus is attached in order to reference the anterior thickness of the distal femur and the appropriate size of thefemoral prosthesis10 is selected, the appropriate femoral cutting block is attached to the intramedullary rod in the appropriate rotation. The block is pinned and the distal anterior cutting block is used to remove the anterior surface of the distal femur.

Anterior and posterior chamfer cuts are made from the medial aspect of the distal femur followed by a posterior femoral cut for the medial femoral condyle. The anterior chamfer cut is extended over the medial aspect of the lateral femoral condyle and a sagittal saw is used to complete the diagonal cut.

Next, a trial reduction with thefemoral component10 andtibial component28 is employed to assure correct surgical preparation and sizing. The extent of possible arthritic disease of the patella is next assessed. If there is extensive disease of the patella, the patella is rotated approximately 90° and an inset patella reamer is applied to the posterior surface of the patella and the patella is reamed to permit the inset of apatella prosthesis component58. Alternatively, an onset or a mobile bearing patella prosthesis may be used as is well known in the art.

A partial lateral facetectomy is typically performed to limit the patellar contact with the transition zone of the distal femur and thefemoral component10. Thepatellar implant58 should be medialized to assist with patella tracking. Release of the medial collateral ligament and/or postero-medial structures can be employed as necessary to allow for ligamentous balancing of the arthroplasty.

The femoral tibial and

patellar implants

10 and28 are next either cemented in the usual fashion if the trial reduction is found to be satisfactory or securely placed over the prepared bone surface so that bone ingrowth can occur if the components have a bone ingrowth surface applied. The knee capsule is closed with a non-absorbable suture followed by skin closure and sterile metal staples with sterile dressing.

With reference toFIGS. 12 and 13, an alternative embodiment of the present invention is shown. While in most cases, the medial compartment of the knee is more prone to be subject to arthritic disease than the lateral compartment, in some cases, the lateral compartment may be diseased while the medial compartment remains healthy and unaffected. This alternative embodiment is designed for those situations where the lateral and patellofemoral joints are affected, but the medial compartment is not.

A lateralfemoral prosthesis component100 similar to the medialfemoral prosthesis component10 ofFIG. 1 except it is configured for the lateral compartment rather than the medial compartment. Lateralfemoral prosthesis component100 is essentially “u” shaped having a firstanterior leg portion102 and a secondposterior leg portion104 that are joined by a base portion (not shown).Anterior leg portion102 has atrochlear groove106 formed on the face thereof to receive and articulate with the patella. Lateralfemoral prosthesis component100 has an interior surface within the “u” (not shown) similar to theinterior surface12 ofcomponent10 that can be secured to a surgically prepared portion of the lateral compartment of thefemur108 using either a cement or a bone ingrowth surface as describe previously.

A lateraltibial prosthesis component110 similar to themedial tibial component28 ofFIGS. 1-4 is shown inFIGS. 12 and 13 as implanted on a surgically prepared lateral compartment of tibia,112.Component110 has a flat bottom surface and a concave upper surface that receives and articulates with a convex outer surface (not shown) on the base portion of thefemoral prosthesis component100 in the same manner as describe previously with respect to theFIG. 1 embodiment. Also,tibial component110 can be fabricated from both metal base and a plastic insert as shown inFIG. 10 and11.

Femoral component

100 andtibial component110 are also configured and designed so that they can be implanted without causing any damage to the middle portion of the knee so that the anterior and posterior cruciate ligaments remain intact after implantation.

It should be appreciated that both

femoral prosthesis components

10 and100 and

tibial prosthesis components

28 and110 can be fabricated from either a metallic material or from plastic. Typically, one component is fabricated from one material and the opposing component is fabricated from the other material so that there is a metal on plastic articulating joint for wear purposes. However, both parts could be fabricated from the same material. A variety of metallic materials can be used including but not limited to stainless steel, cobalt chrome steel, titanium, Zirconia, ceramics and tantalum. Also, a variety of plastic materials can be used including but not limited to polyethylene, polycarbonate-based polyurethane, and implantable-grade polymethyl methacrylate (PMMA).

It should be recognized that the preferred embodiment of the present invention as described above can be varied or modified without departing from the spirit and scope of the present invention as described and claimed in the following claims.

Claims

1. A method of performing bicompartmental arthroplasty of a patient's knee comprising the steps of:

a. making an incision along the anterior medial aspect of the knee;

b. excising the remnants of the medial meniscus;

c. surgically preparing a medial compartment of a proximal end of the patient's tibia to receive a medial tibial prosthesis component in a manner so as to preserve the integrity of a anterior and posterior cruciate ligaments; said medial tibial prosthesis component having a first surface configured to be secured to said surgically prepared medial compartment of the proximal end of the patient's tibia and a second concave curved surface;

d. rotating a patella approximately 90 degrees;

e. surgically preparing a medial compartment of a distal end of the patient's femur to receive a medial femoral prosthesis component having a concave trochlea surface; said medial femoral prosthesis component also having a first surface configured to be secured to said surgically prepared medial compartment of the distal end of the femur and a second convex curved surface configured to articulate with the second concave curved surface of said medial tibial prosthesis component to permit pivotal articulation between said medial femoral prosthesis component and said medial tibial prosthesis component, said pivotal articulation approximating the articulation of a healthy knee joint;

f. securing a medial femoral component to the femur;

g. securing the medial tibial component to the tibia;

h. positioning the patella over the concave trochlea surface of the medial femoral prosthesis component; and

i. closing the incision.

2. A method of performing bicompartmental arthroplasty of the knee as claimed inclaim 1, further comprising the additional steps of:

a. surgically preparing a posterior surface of the patient's patella to receive a patella prosthesis component having a first surface configured to be secured to said surgically prepared posterior surface of the patella, and a convex curved second surface configured to engage the concave trochlea surface of said medial femoral prosthesis component; and

b. securing said patella prosthesis component to the patella.

3. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial femoral prosthesis component comprises a metallic material.

4. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial femoral prosthesis component comprises a bio-compatible plastic.

5. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial tibial prosthesis component comprises a bio-compatible plastic.

6. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial tibial prosthesis component comprises a metallic material.

7. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial tibial prosthesis component comprises a bio-compatible plastic and metallic material.

8. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said medial femoral prosthesis component and said medial tibial prosthesis component are dimensioned to permit the distal end of the femur and the proximal end of the tibia to be surgically prepared in manner so as to preserve the integrity of the patient's anterior and posterior cruciate ligaments.

9. A method for bicompartmental arthroplasty of the knee as claimed inclaim 2 further comprising the additional step of:

positioning said convex curved second surface of said patella prosthesis component to articulate with the concave trochlea surface of said medial femoral prosthesis component.

10. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said femoral prosthesis component is secured to the femur using a cement.

11. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said femoral prosthesis component is secured to the femur by bone ingrowth into an ingrowth surface applied to the first surface of the femoral prosthesis component.

12. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said tibial prosthesis component is secured to the tibia using a cement.

13. A method for bicompartmental arthroplasty of the knee as claimed inclaim 1 wherein said tibial prosthesis component is secured to the tibia by bone ingrowth into an ingrowth surface applied to the first surface of the tibial prosthesis component.

14. A method for bicompartmental arthroplasty of the knee as claimed inclaim 2 wherein said patella prosthesis component is secured to the patella by cement.

15. A method for bicompartmental arthroplasty of the knee as claimed inclaim 2 wherein said patella prosthesis component is secured to the patella by bone ingrowth into an ingrowth surface applied to the first surface of the patella prosthesis component.

16. A method of performing bicompartmental arthroplasty of a patient's knee comprising the steps of:

a. making an incision along an anterior medial aspect of the knee;

b. excising remnants of a medial meniscus;

c. surgically preparing a medial compartment of a proximal end of a patient's tibia to receive a medial tibial prosthesis component in a manner so as to preserve the integrity of anterior and posterior cruciate ligaments; said medial tibial prosthesis component having a first surface configured to be secured to said surgically prepared medial compartment of the proximal end of the tibia and a second concave curved surface;

d. rotating the patient's patella approximately 90 degrees;

e. surgically preparing the medial compartment of a distal end of the patient's femur to receive a medial femoral prosthesis component, said medial femoral prosthesis component having a first leg portion and a second leg portion and a base portion connected between said first and second leg portions to form an essentially U-shaped component, said medial femoral prosthesis component having a first interior surface configured to be secured to a surgically prepared medial compartment of a distal end of the patient's femur so that a base portion of the femoral prosthesis contacts the distal end of the femur, said first leg portion contacts the anterior surface of the distal end of the femur, and the second leg portion contacts the posterior surface of the distal end of the femur, and said medial femoral prosthesis component also having a second exterior convex curved surface on said base portion, and an exterior concave trochlea surface positioned on said first leg portion and configured to articulate with the patella; said second convex curved surface on said base portion configured to articulate with the second concave curved surface of said medial tibial prosthesis component to permit articulation between said medial femoral prosthesis component and said medial tibial prosthesis component, said articulation motion approximating the articulation of a healthy knee joint;

f. securing the medial femoral component to the femur;

g. securing the medial tibial component to the tibia;

h. positioning the patella over the trochlea surface of the medial femoral prosthesis component; and

i. closing the incision.

17. A method of performing bicompartmental arthroplasty of the knee as claimed inclaim 16 comprising the additional steps of:

b. Securing said patella prosthesis component to the patella.

18. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial femoral prosthesis component comprises a metallic material.

19. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial femoral prosthesis component comprises a bio-compatible plastic.

20. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial tibial prosthesis component comprises a bio-compatible plastic.

21. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial tibial prosthesis component comprises a metallic material.

22. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial tibial prosthesis component comprises a bio-compatible plastic and metallic material.

23. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said medial femoral prosthesis component and said medial tibial prosthesis component are dimensioned to permit the distal end of the femur and the proximal end of the tibia to be surgically prepared in manner so as to preserve the integrity of the anterior and posterior cruciate ligaments.

24. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said femoral prosthesis component is secured to the femur using a cement.

25. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said femoral prosthesis component is secured to the femur by bone ingrowth into an ingrowth surface applied to the first surface of the femoral prosthesis component.

26. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said tibial prosthesis component is secured to the tibia using a cement.

27. A method for bicompartmental arthroplasty of the knee as claimed inclaim 16 wherein said tibial prosthesis component is secured to the tibia by bone ingrowth into an ingrowth surface applied to the first surface of the tibial prosthesis component.

28. A method for bicompartmental arthroplasty of the knee as claimed inclaim 17 wherein said patella prosthesis component is secured to the patella by cement.

29. A method for bicompartmental arthroplasty of the knee as claimed inclaim 17 wherein said patella prosthesis component is secured to the patella by bone ingrowth into an ingrowth surface applied to the first surface of the patella prosthesis component.

30. A method for bicompartmental arthroplasty of the knee as claimed inclaim 17 further comprising the additional step of: