WO2012100962A1

WO2012100962A1 - Knee prosthesis

Info

Publication number: WO2012100962A1
Application number: PCT/EP2012/000386
Authority: WO
Inventors: Cosimo Donno; Marc MÜNCHINGER
Original assignee: Zimmer Gmbh
Priority date: 2011-01-27
Filing date: 2012-01-24
Publication date: 2012-08-02

Abstract

The present disclosure relates to a knee prosthesis comprising a tibial component (14) with at least one tibial condylar portion (20a, 20b) and a femoral component (12) with at least one femoral condylar portion ( 18a, 18b). The knee prosthesis further includes a stabilization means comprising an artificial ligament (24, 24') connecting the tibial component and femoral component and a fixation means for fixing a ligament to the tibial component or the femoral component, wherein the fixation means is adapted and positioned to be manipulated from an anterior side of the prosthesis.

Description

Knee prosthesis

The present disclosure relates to a knee prosthesis comprising a tibial component with at least one tibial condylar portion and a femoral compo- nent with at least one femoral condylar portion.

Important aspects of a knee prosthesis are its properties as regards the kinematics of the articulation and an efficient stabilization of the prosthesis in order to mimic at least in part the articulation kinematics of a natural knee. Attention has to be paid in this context to the functionality pro- vided by the ligaments of a natural knee, in particular by the cruciate ligaments, since they contribute significantly to the stabilization of the knee joint. It is further important that the implantation of the prosthesis can be performed relatively easily.

One object of this disclosure is to provide a knee prosthesis of the afore- mentioned kind with an improved stability of the knee prosthesis during articulation, which can be implanted and assembled easily to minimize the impact of a corresponding surgical intervention.

Accordingly, the present disclosure provides a knee prosthesis including a stabilization means comprising an artificial ligament connecting the tibial and the femoral components. Further, a fixation means adapted and positioned to be manipulated from an anterior side of the prosthesis is provided. The fixation function of said means allows to fix the artificial ligament to the tibial component or the femoral component and to maintain a tension applied to the ligament. Such an arrangement of the fixation means facilitates the fixation of the ligament and allows easy access during implantation and/ or revision of the prosthesis.

In a further embodiment of the knee prosthesis according to the present disclosure, the fixation means is accessible from an anterior side of the prosthesis. Alternatively or additionally, the fixation means can be ar- ranged on an anterior side of the prosthesis. In particular, the fixation means is arranged on an anterior side of the tibial component.

In a further embodiment of the knee prosthesis according to the present disclosure, the artificial ligament is adapted to replace functionally at least one of the ligaments, in particular at least one of the cruciate ligaments, of a natural knee joint. In particular, the artificial ligament is flexible.

In a further embodiment of the knee prosthesis according to the present disclosure, the ligament is accessible from an anterior side of the prosthesis. In this case the ligament can be conveniently manipulated directly if necessary requiring only minimal surgical intervention. In particular, the ligament remains accessible even after final assembly of the knee prosthesis as regards the fixation means.

In a further embodiment of the knee prosthesis according to the present disclosure, the stabilization means further comprises an adjustment means for adjusting a tension of the ligament.

The adjustment function allows modifying the tension of the ligament according to the specific needs of a given patient. Although the fixation function and the adjustment function can be furnished by a single means, alternative embodiments of a knee prosthesis according to the present disclosure can be envisaged that are provided with a fixation and adjustment means that comprises separate - in certain cases also spatially separated - units providing said functions independently from each other.

The adjustment function allows selecting the suitable tension of the ligament during implantation of the knee prosthesis. The adjusted ligament is then secured by the fixation functionality of the fixation and adjustment means. Of course, said means can be adapted to provide an automatic fixation during adjustment so that no separate fixing procedure has to be performed. In some cases the problem arises after implantation of the knee prosthesis that the initially selected tension of the ligament degrades and/or that the selected tension shows to be insufficient or too high. The adjustment functionality of the stabilization means described above allows adjusting the tension of the ligament without the need for a major surgical intervention. A surgeon has merely to access the fixation and/or adjustment means - e.g. via a minor incision at the anterior part of the knee of the patient - and to manipulate it in order to change the tension of the ligament. Manipulation of the fixation and /or adjustment means can be carried out directly or using a corresponding tool. Said manipulation is facilitated by the fact that at least the fixation means is adapted and positioned to be manipulated from an anterior side of the prosthesis. The adjustment means can also be adapted and positioned likewise. In particular, the adjustment means is accessible from and/or arranged on an anterior side of the prosthesis.

In an exemplary embodiment of the knee prosthesis according to the present disclosure, the fixation and/ or adjustment means is selectively detachable, i.e. said means can be at least in part be separated from the further components of the knee prosthesis. The assembly of said means can be performed prior or during the implantation and/ or revision of the knee prosthesis.

In a further embodiment of the knee prosthesis according to the present disclosure, the fixation and/ or adjustment means comprises a set screw connected to the ligament and received in a complementary threaded bore. Other mechanisms that provide a fixation and/or adjustment function suitable for a use in a knee prosthesis according to the present disclosure are also conceivable. E.g. EP 2 192 863 describes various examples of suitable fixation mechanisms.

Exemplarily, the fixation and/ or adjustment means is disposed on the tibial component, in particular on a base member of the tibial component. In an further embodiment of the knee prosthesis according to the present disclosure, the stabilization means comprises a deflection member to define a orientation of at least a segment of the ligament adjacent to the fixation and/or adjustment means. In particular, said segment of the lig- ament adjacent to the fixation and/ or adjustment means is oriented parallel to an anterior-posterior direction of the prosthesis in order to facilitate the fixation and/or adjustment of the ligament.

A protection of the segment of the ligament adjacent to the fixation and/or adjustment means can be achieved when disposing said segment at least in part in a channel formed by the base member of the tibial component.

In particular in cases where both cruciate ligaments are damaged and have to be replaced by artificial ligaments, a suitable embodiment of the knee prosthesis according to the present disclosure comprises a tibial component with a medial tibial condylar portion and a lateral tibial condy- lar portion and a femoral component with a medial femoral condylar portion and a lateral femoral condylar portion. The stabilization means of said embodiment comprises a first artificial ligament connecting the medial femoral condylar portion with the tibial component, a second artificial ligament connecting the lateral femoral condylar portion with the tibial component, a first fixation means for fixing the first ligament to the tibial component or the femoral component and a second fixation means for fixing the second ligament to the tibial component or the femoral component. In particular, both the first and second fixation means are adapted and positioned to be manipulated from an anterior side of the prosthesis. For example, both first and second fixation means are arranged on an anterior side of the tibial component. Of course, first and second adjustment means with the features described above can be provided to facilitate the adjustment of the tension of the first and second ligaments, respectively. A method for implanting a knee prosthesis according to the present disclosure comprises the steps of preparing a distal end of the femur for fixation of the femoral component, e.g. by resectioning, preparing the proximal end of the tibia for fixation of the tibial component, e.g. by resection- ing, and fixing the femoral and the tibial components to the prepared femur and the prepared tibia, respectively.

In an embodiment of said method, the step of fixing the artificial ligament to the tibial and femoral components is carried out after implantation of said components.

In a further embodiment of said method, the step of fixing the artificial ligament is performed prior to implantation of the tibial and femoral components.

In a further embodiment of said method, the ligament is fixed to one of the tibial and femoral components prior to their implantation. Fixing the liga- ment to the other component is carried out after the implantation of the tibial and femoral components.

In a further embodiment of the method, the tension of the ligament is adjusted after implantation of the tibial and femoral components.

In a further embodiment of the method, a revision of the knee prosthesis is performed by creating an incision adjacent to the fixation and/or adjustment means of the stabilization means of the knee prosthesis according to the present disclosure and manipulating said means in order to adjust the tension of the ligament as required.

The different embodiments of the knee prosthesis in accordance with the scope of the independent claim and/ or the method described above and the features realized there can naturally be combined with one another.

Further embodiments of the disclosure are also recited in the dependent claims, the description and the drawings. Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for the purpose of illustration only and are not intended to limit the scope of the disclosure in any way. The figures are simplified and schematic. Details not necessary for the understanding of the disclosure are omitted.

The present disclosure will be explained in more detail and become fully understood from the detailed description and the accompanying drawings, wherein

Figs. 1 to 5 show a first embodiment of a knee prosthesis according to the present disclosure and

Figs. 6 to 9 show a second embodiment of the knee prosthesis

according to the present disclosure.

Fig. 1 shows a knee prosthesis 10 comprising femoral component 12 and tibial component 14. Femoral component 12 comprises patella condyle 16 and femoral condyles 18a, 18b that cooperate with corresponding tibial condyles 20a, 20b disposed on tibial base 22.

Components 12, 14 are connected by an artificial flexible ligament 24 extending between a posterior part of femoral condyle 18b and a central section 26 of tibial base 22 disposed between tibial condyles 20a, 20b.

Ligament 24 is fixedly secured to femoral condyle 18b. A first segment of ligament 24 extends obliquely from a condylar fixation device 28 disposed on femoral condyle 18b towards distal and anterior before it is deflected into a plane defined by tibial base 22. The deflected part of ligament 24 forms a second segment of ligament 24 that is oriented in essence in a posterior-anterior direction. Said second segment enters a fixation portion 25 protruding partly from central section 26 of tibial base 22. The anterior end of ligament 24 is disposed in a bore 30 of fixation portion 25. Said bore 30 is accessible from an anterior side of tibial component 14. Fig. 2 shows knee prosthesis 10 in a partly disassembled state as it occurs during one embodiment of a method to implant knee prosthesis 10. Ligament 24 is already secured to femoral component 12. The anterior segment of ligament 24 to be connected to tibial component 14 is not yet introduced in fixation portion 25. To finalize the assembly of knee prosthesis 10, the second segment of ligament 24 is introduced in a channel - described in detail below - and in bore 30 to be fixed there. The process of fixation includes in one embodiment of the method for implanting a knee prosthesis introducing a fixation member - e.g. a screw - through bore 31. An adjustment means - which is not shown in detail - facilitates the adjustment of the tension applied to ligament 24 in order to provide knee prosthesis 10 with the required stability. Said adjustment means is arranged according to one embodiment of the present disclosure such that is can be easily manipulated from an anterior side of knee prosthesis 10 therefore minimizing the complexity of a corresponding surgical procedure.

Contrary to knee prosthesis without adjustment means, the knee prosthesis according to one aspect of the present disclosure allows to adjust the tension of ligament 24 after primary knee replacement during a simple revision procedure. Positioning of the fixation and/or adjustment means on an anterior side of tibial component 14 allows easy access requiring only a minor incision to reach ligament 24 via bores 30, 31. The means for fixing and adjusting ligament 24 are in one embodiment of the present disclosure provided with an interface that can be coupled to a correspond- ing fixing and/ or adjustment tool. Instead of providing a tool for manipulating the fixation and/or adjustment means, a corresponding mechanism that can be manipulated manually can be provided on knee prosthesis 10 itself.

It should be understood that bores 30, 31 are merely examples of how to fix ligament 24 to an anterior part of the tibial component 14. A plethora of fixing and/or adjustment means are conceivable, such as a set-screw fixed to ligament 24 that is seated e.g. in bore 30. A further screw may be inserted in bore 31 to pinch anterior end of ligament 24 in channel 36 or bore 30 thereby providing fixation after an adjustment of the tension of ligament 24 using said set-screw.

Fig. 3 shows a view of knee prosthesis 10 from posterior to reveal a deflection means 32 disposed between proximal-distal extending walls 34 limiting medial and lateral sides of central section 26. Deflection means 32 deflects ligament 24 in a plane defined by tibial base 22. Deflecting liga- ment 24 in said plane bears the advantage that a force needed to provide the tension of ligament 24 can also be applied in said plane minimizing oblique forces acting on the tibial component during tensioning. Further, it is avoided that oblique forces are exerted on the means provided for fixing and adjusting ligament 24.

Fig. 4 shows the anterior side of knee prosthesis 10, whereas Fig. 5 shows a side view. Tibial component 14 is shown in transparent in Fig. 5 in order to avoid obstruction of the view on ligament 24. It can be seen from Fig. 5 that deflection means 32 is a pin extending in a plane parallel to tibial base 22. Fig. 5 further shows that the second segment of ligament 24 ex- tending in the plane of tibial base 22 is in essence disposed to its full extent in a channel 36 traversing fixation portion 25 of central section 26 in a posterior-anterior direction thereby protecting said segment and constraining its movements.

Fig. 6 shows a knee prosthesis 10' which essentially comprises the com- ponents described already in connection with knee prosthesis 10. Additionally, a second ligament 24' is provided connecting a central portion of femoral condyle 18a with tibial component 14. To this end, ligament 24' extends obliquely from a condylar fixation device 28' towards distal and posterior before being deflected by deflection means 32' shown in Fig. 7 into the plane of tibial base 22. Ligament 24' extends from said deflection means 32' towards anterior in a channel 36' until reaching the anterior side of tibial component 16. Ligament 24' is accessible there through bores 30', 3 Γ.

Figs. 8 and 9 show a view of knee prosthesis 10' from posterior and ante- rior, respectively, to demonstrate that ligaments 24, 24' are brought towards the anterior portion of tibial component 14 in a substantially similar manner. Hence, they are both easily accessible to facilitate implantation and revision procedures especially with respect to a tensioning of ligaments 24, 24'.

It should be noted that ligaments 24, 24' are disposed in separate channels 36, 36' to prevent obstructions.

All anatomical terms relating to directions or locations, such as anterior, posterior, medial, lateral, proximal and distal, refer to an implanted state of the components and implants described above.

The description of the disclosure is merely exemplary in nature, and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure.

List of References Numerals

10, 10' knee prosthesis

12 femoral component

14 tibial component

16 patella condyle

18a, 18b femoral condyle

20a, 20b tibial condyle

22 tibial base

24, 24' ligament

25 fixation portion

26 central section

28, 28' condylar fixation device

30, 30", 31 , 31' bore

32, 32' deflection means

34 wall

36, 36' channel

Claims

A knee prosthesis, comprising:

a tibial component (14) with at least one tibial condylar portion (20a, 20b);

a femoral component (12) with at least one femoral condylar portion (18a, 18b);

a stabilization means comprising:

an artificial ligament (24, 24') connecting the tibial and the femoral components, and

a fixation means for fixing the ligament to the tibial component or the femoral component, wherein the fixation means is adapted and positioned to be manipulated from an anterior side of the prosthesis.

A knee prosthesis according to claim 1,

wherein the fixation means is accessible from an anterior side of the prosthesis.

A knee prosthesis according to claims 1 or 2,

wherein the fixation means is arranged on an anterior side of the prosthesis, in particular on an anterior side of the tibial component.

A knee prosthesis according to any of claims 1 to 3,

wherein the artificial ligament is adapted to replace functionally at least one of the ligaments, in particular at least one of the cruciate ligaments, of a natural knee joint.

5. A knee prosthesis according to any of claims 1 to 4,

wherein the artificial ligament is flexible.

6. A knee prosthesis according to any of claims 1 to 5, wherein the ligament is accessible from an anterior side of the prosthesis.

A knee prosthesis according to any of claims 1 to 6,

wherein the stabilization means further comprises an adjustment means for adjusting a tension of the ligament.

A knee prosthesis according to any of claims 1 to 7,

wherein the fixation and/ or adjustment means is selectively detachable.

A knee prosthesis according to any of claims 1 to 8,

wherein the fixation and/ or adjustment means comprises a set screw connected to the ligament and received in a complementary threaded bore.

A knee prosthesis according to any of claims 1 to 9,

wherein the fixation and/or adjustment means is disposed on the tibial component, in particular on a base member (22) of the tibial component.

A knee prosthesis according to any of claims 1 to 10,

wherein the stabilization means comprises a deflection member (32, 32') to define an orientation of at least a segment of the ligament adjacent to the fixation and/or adjustment means.

A knee prosthesis according to any of claims 1 to 1 1,

wherein a segment of the ligament adjacent to the fixation and/ or adjustment means is oriented parallel to an anterior-posterior direction.

A knee prosthesis according to claim 12,

wherein the segment of the ligament adjacent to the fixation and/or adjustment means is disposed at least in part in a channel (36, 36') formed in a base member of the tibial component.

14. A knee prosthesis according to any of claims 1 to 13,

wherein the tibial component comprises a medial tibial condylar portion and a lateral tibial condylar portion;

wherein the femoral component comprises a medial femoral condylar portion and a lateral femoral condylar portion; and

wherein the stabilization means comprises a first artificial ligament connecting the medial femoral condylar portion with the tibial component, a second artificial ligament connecting the lateral femoral condylar portion with the tibial component, a first fixation means for fixing the first ligament to the tibial component or the femoral component and a second fixation means for fixing the second ligament to the tibial component or the femoral component.

A knee prosthesis according to claim 14,

wherein both the first and the second fixation means are adapted and positioned to be manipulated from an anterior side of the prosthesis.