Revision femoral prosthesis

Abstract

A femoral prosthesis is disclosed. The femoral prosthesis includes a femoral component. The femoral component is configured to be attached to the femur and is made of cobalt-chromium-molybdenum. The femoral component has a three-dimensional curved shape within its box 202. The femoral prosthesis further includes a tibial insert. The tibial insert is attached to the femoral component. The tibial insert is made of ultra-high molecular weight polyethylene material and includes an articular surface. The articular surface interacts with the femoral component to facilitate flexion-extension and internal / external rotation movements. The tibial insert includes a tibial support. The tibial support has increased widths in the medial-lateral and anterior-posterior directions. Based on the three-dimensional curved shape within the box, internal / external rotation gradually increases with different flexion angles of the femoral component, achieving an internal / external rotation angle ranging from 0.4° to 5.5°.

Description

[Technical Field]

[0001] The present subject matter relates generally to orthopedic prostheses, and more particularly to revision femoral prostheses having progressive internal and external rotation angle changes at different flexion angles. [Background technology]

[0002] Advances in surgical techniques and implant technology have improved 10-year survival rates after primary total hip arthroplasty (THA). Despite this, the number of revision procedures has increased in recent years, and this trend is predicted to continue. Revision THA is a technically challenging procedure, often complicated by loss of host bone stock and the need to remove the original implant. In the UK, both cemented and uncemented implant designs are commonly used in primary and revision THAs, although there is still considerable controversy regarding the ideal stem fixation method. Revision THA is often indicated for instability, aseptic loosening, osteolysis, infection, periprosthetic fracture, component malposition, or catastrophic implant failure. Understanding the etiology of THA failure is essential to guide clinical decision-making. Revision of the femoral component poses a complex challenge for total hip arthroplasty surgeons due to bone loss in the proximal femur as well as modern implant designs. Postoperative outcomes depend on precise surgical reconstruction based on thorough patient evaluation, defect classification, and comprehensive preoperative planning. Knowledge of the various reconstructive options and their respective indications is necessary to achieve a successful outcome.

[0003] Prior applications, such as U.S. Patent No. 5,147,405, disclose femoral prostheses including tibial components. This patent places significant emphasis on controlling "rollback" (the posterior movement of the contact point during knee flexion). While this is controlled to some extent, the rollback distance is described as approximately 6 mm. This lack of rollback, particularly in comparison with the first invention, could potentially lead to problems and complications. The design in U.S. Patent No. 5,147,405 specifies that rollback does not occur when the femoral and tibial components are flexed from approximately 45° to a flexed position. This can limit natural motion and create an unnatural feeling during mid- to late flexion. Conversely, given the lack of such limitations, the first invention may provide more continuous or smooth motion throughout the entire range of motion. As described in U.S. Patent No. 5,147,405, this design incorporates a multifaceted mechanism, including a posterior cam surface, a multi-section stabilizing support, and a fixation rod. This may increase the complexity of the implantation procedure and prolong the surgical and recovery periods. The very fact that the patent emphasizes these features to reduce the likelihood of dislocation between the femoral and tibial components suggests a higher inherent risk. The previously mentioned invention may have a more robust and stable design that inherently reduces the risk of such dislocation. The patent suggests that controlled rollback is important to prevent the tibial tray from flexing or rocking and loosening. However, relying on the stability of the tray may lead to complications if it malfunctions or moves unexpectedly. Given the addition of stabilizing supports, fixation rods, and camming surfaces, the prosthesis according to U.S. Patent No. 5,147,405 may be bulkier than the previously described invention. This may result in a thicker profile that may not be suitable for all patients and may require more extensive bone resection during surgery.Multiple articulations and engagement points (such as the engagement means of the posterior cam surface during certain flexion angles) can increase wear and tear over time and shorten the lifespan of the implant.

[0004] Another prior application, US 2011 / 125275 A1, discloses an artificial joint including a first implant component for attachment to a first bone and a second implant component for attachment to a second bone. The first implant component has a condylar portion with first and second condylar bearing surfaces, and the second implant component similarly has a complementary bearing surface for receiving the first and second condylar bearing surfaces. Each of the first and second condylar bearing surfaces and each of the bearing surfaces of the second implant component have cross sections in a coronal plane that exhibit two different radii, and contact points are provided between the first and second condylar bearing surfaces and the bearing surface of the second implant component. The bearing surfaces of each implant component are configured such that the contact points move outward with varus and valgus rotation of the first implant component relative to the second implant component. Summary of the Invention

[0005] SUMMARY OF THE INVENTION Embodiments of the present disclosure provide technical improvements as solutions to one or more of the technical problems set forth above.

[0006] Before proceeding with this subject matter relating to revision femoral prostheses, it should be understood that the present disclosure is not limited to the particular systems and methodologies described, as there may be multiple possible embodiments not explicitly illustrated in the present disclosure. It should also be understood that the terminology used herein is for embodiments or versions or embodiments only, and is not intended to limit the scope.

[0007] This Abstract is provided to introduce aspects related to revision femoral prostheses. It is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining or limiting the scope.

[0008] In one embodiment, a femoral prosthesis is disclosed, which includes a femoral component and a tibial insert. The femoral component is made of cobalt-chromium-molybdenum (CoCrMo) alloy and configured for attachment to the femur. The femoral component has a curved shape within its femoral box. Furthermore, a tibial insert is attached to the femoral component. The tibial insert is made of ultra-high molecular weight polyethylene (UHMWPE) material and has an articular surface that interfaces with the femoral component to promote flexion-extension and internal / external rotation. The tibial insert includes a tibial support that has increased width in the medial-lateral and anterior-posterior directions. Based on the curved shape of the femoral box, internal / external rotation gradually increases with different flexion angles of the femoral component, achieving an internal / external rotation angle ranging from 0.4° to 5.5°.

[0009] The femoral component is available in both left- and right-handed configurations and includes mounting points for distal and posterior augmentation attachments. Additionally, the femoral component features a deeper patellar groove. In this embodiment, the tibial bearing is tapered 4° from the bottom surface of the tibial bearing, and the tibial insert features a 7° posterior slope toward the articular surface. The tibial insert features chamfers on both the anterior and posterior sides; the anterior chamfer facilitates patellar movement, while the posterior chamfer provides space for ligaments.

[0010] Furthermore, when the flexion angle is 0°, the clearance between the femoral box and the tibial support limits the maximum internal and external rotation to 1°. Furthermore, when the flexion angle is 90°, the maximum internal and external rotation is 5.5° to 6°. [Brief explanation of the drawings]

[0011] The foregoing detailed description of the embodiments will be better understood when read in conjunction with the accompanying drawings. For purposes of illustrating the disclosure, example structures of the disclosure are shown herein; however, the disclosure is not limited to the systems / apparatus or specific methods disclosed in the specification and drawings.

[0012] The present disclosure will now be described in detail with reference to the accompanying drawings, in which the leftmost digit(s) of a reference number identifies the figure in which the reference number first appears, and the same numbers are used throughout the drawings to refer to various features of the present subject matter to identify them.

[0013] [Figure 1] 1A, 1B, 1C, and 1D illustrate anterior-posterior motion according to an embodiment of the present subject matter.

[0014] [Figure 2] 2A and 2B illustrate medial-lateral movement (femoral component lift) according to an embodiment of the present subject matter.

[0015] [Figure 3] FIG. 3 illustrates the curve dimensions of a femoral component according to an embodiment of the present subject matter.

[0016] [Figure 4A] FIG. 4A illustrates a loft geometry according to a second curvature of a three-dimensional shape according to an embodiment of the present subject matter.

[0017] [Figure 4B] FIG. 4B shows a cross section of a loft shape according to an embodiment of the present subject matter.

[0018] [Figure 5] 5A, 5B, and 5C show various views of a tibial insert according to an embodiment of the present subject matter.

[0019] [Figure 5D] FIG. 5D illustrates the medial-lateral support distance (dimension A) of the tibial insert according to an embodiment of the present subject matter.

[0020] [Figure 6] 6A, 6B, and 6C illustrate a femoral insert assembly (shown after IE rotation of the femur on the insert contact point) according to an embodiment of the present subject matter.

[0021] Moreover, the figures depict various embodiments of the present subject matter for purposes of illustration only. Those skilled in the art of the present subject matter will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles described herein. DETAILED DESCRIPTION OF THE INVENTION

[0022] Several embodiments of the present disclosure exhibiting all of its features will now be described in detail. The words "comprising," "having," "containing," and "including," as well as other forms thereof, mean that the item or items following any one of these words are an exhaustive list of such items or items, are equivalent in meaning, and are intended to be open-ended, in that they are not intended to be limited to only the listed items or items. It should also be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Exemplary revision femoral prostheses similar or equivalent to those described herein and that can be used in practicing or testing embodiments of the present disclosure are described herein.

[0023] Various modifications to the present embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments. The present disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.

[0024] As mentioned above, primary total hip arthroplasty (THA) has witnessed a significant improvement in 10-year survival rates due to advances in surgical techniques and implant technology. However, the number of revision procedures is increasing. Revision of the femoral component presents complex challenges due to modern implant designs and bone loss in the proximal femur. Various femoral prostheses have been designed, as exemplified in U.S. Patent No. 5,147,405 and U.S. Patent No. 2011 / 125275A1. However, there remains a need for more advanced revision femoral prostheses that address the specific technical challenges associated with revision of the femoral component.

[0025] In one embodiment, the revision femoral insert for a revision femoral prosthesis features a progressive angulation. The revision femoral component is made of CoCrMo alloy (cobalt chromium molybdenum). The tibial insert is made of ultra-high molecular weight polyethylene (UHMWPE) material. The articular surface interacts with the tibial insert to facilitate flexion-extension and internal / external rotation. The femoral design is available in eight different sizes for both left and right use. The femoral component has a narrow flange on the anterior side to avoid bone interference, which can lead to complications such as periprosthetic fractures. The distal and posterior thicknesses of the femoral component promote proper articular surface maintenance and ensure postoperative knee movement as close to natural movement as possible. The femoral component features a deeper patellar groove and has mounting points for distal and posterior augmentation attachments. Revision femoral components feature a three-dimensional curved box to facilitate progressive internal and external rotation. Different curves are added to the femoral component to achieve up to 5.5° of internal and external rotation. The tibial insert is available in eight sizes with different thicknesses. The tibial insert features a 7° posterior slope on the articular surface. This slope is important for achieving natural biomechanics and ensures postoperative knee movement is as close to natural as possible. The tibial insert also features chamfers on the anterior and posterior sides. The anterior chamfer facilitates patellar movement, while the posterior chamfer facilitates ligament movement. The femoral component slides, rolls, and rotates at different angles and contact points relative to the tibial insert as it moves in the medial-lateral or anterior-posterior direction. Different contact points exist for medial-lateral or anterior-posterior movement.

[0026] In one embodiment, an advantage of the present subject matter is its ability to provide gradual internal / external rotation (IE) angle changes with different flexion angles, including a three-dimensional curved shape within its femoral box (also called a box), allowing for gradual increases in IE angle as the flexion angle changes. Specifically, it can rotate up to 1° at 0° of flexion and 5.5° to 6° at 90° of flexion. This not only ensures patient comfort after surgery, but also plays a vital role in extending the life of the implant and reducing the need for subsequent revisions. The above-mentioned and other advantages will become more apparent below.

[0027] One embodiment provides gradual internal / external rotation (IE) angle changes at different flexion angle positions associated with the revision femoral prosthesis. Additionally, a curved shape is added within the femoral box component. The curved shape within the femoral box progressively increases IE rotation. At 0°, there is slight clearance between the femur and the insert, resulting in a maximum of 1° of IE rotation. As the femoral component rolls over the tibial insert through flexion, IE rotation also occurs, resulting in 5.5° to 6° of IE rotation at 90° of flexion. The width of the tibial support increases in the medial-lateral and anterior-posterior directions to maintain IE rotation between 0.4° and 5.5°. A 4° gradient is added to the tibial support from the bottom surface.

[0028] The present subject matter and its embodiments will now be described in more detail with reference to the figures. Furthermore, the following glossary indicates the symbols used in the figures. JPEG2025529346000002.jpg86153

[0029] Referring to Figures 1A, 1B, 1C and 1D, an anterior-posterior movement is disclosed.

[0030] Due to the clearance between the femoral box 202 and the tibial support 112, medial-lateral movement (femoral component lift) occurs. Furthermore, FIGS. 2A and 2B disclose the medial-lateral angle. The contact point of the femoral insert changes as the cam 108 engages the tibial support 112 at angles from 15° to 90°. Internal and external rotation occurs along with the anterior-posterior movement of the femur. Due to the three-dimensional curved shape 114 of the femoral box 202, internal and external rotation gradually increase. At 0°, there is slight clearance between the femur and the insert, resulting in a maximum of 1° of internal-external rotation. Internal-external rotation also occurs when the femoral component 102 rolls on the tibial insert 104 at different angles. At a flexion angle of 90°, the internal and external rotation angle increases to 5.5°. Furthermore, Figure 3 shows the curve dimensions along with Table 1 below. Table 1: Curvature dimensions for Figure 3 JPEG2025529346000003.jpg48153

[0031] After this curvature, drawings are made with the femur rotated 0°, 15°, 30°, 45°, 60°, 75°, and 90° relative to the tibial insertion 104, and sketches are added. The dimensions of the cross sections are as follows. The 4° angle is constant for all cross sections. All drawings are used in different positions to add the curved section. Furthermore, Figures 4A and 4B show the dimensions of the curved section, along with Table 2 below. Table 2: Loft dimensions and loft cross section JPEG2025529346000004.jpg49153

[0032] To accommodate the progressive angulation, several modifications were made to the revision tibial insert 104. The width of the tibial bearing 112 was increased in the medial-lateral and anterior-posterior directions to maintain IE rotation from 0.4° to 5.5°. A 4° slope is added from the bottom surface of the tibial bearing 112. Additionally, Figures 5A, 5B, 5C, and 5D show various views of the tibial insert 104. Additionally, Figure 5D shows the medial-lateral support distance (dimension A) of the tibial insert 104 with reference to the table below. JPEG2025529346000005.jpg53153 The femur and the insertion part rotate internally and externally, and different contact points exist at different angles. When the femur and insertion part do not rotate IE, the three contact points are on the same line; when they rotate IE, the contact points should be diagonal. Figures 6A, 6B, and 6C show the femoral insertion part assembly (shown after IE rotation of the femur on the insertion part contact points).

[0033] Although examples of revision femoral prostheses are provided herein, it should be understood that the above description is not necessarily limited to the specific features and methods disclosed as examples of revision femoral prostheses.

Claims

1. a femoral component (102) made of cobalt chromium molybdenum (CoCrMo alloy), configured to be attached to the femur via a stem base (106), and having a three-dimensional curved shape (114) within its box (202); a tibial insert (104) attached to the femoral component (102), made from an ultra-high molecular weight polyethylene (UHMWPE) material, and including an articular surface (508); The articular surface (508) interacts with the femoral component (102) to facilitate flexion-extension and internal / external rotation movements, and the tibial insertion portion (104) includes a tibial support (112), which has an increased width in the medial-lateral direction and the anterior-posterior direction, and based on its three-dimensional curved shape within the box (202), the internal / external rotation gradually increases according to different flexion angles of the femoral component (102), achieving an internal / external rotation angle in the range of 0.4° to 5.5°. Femoral prosthesis.

2. The femoral prosthesis of claim 1 , wherein the femoral component (102) has both left-handed and right-handed configurations.

3. 2. The femoral prosthesis of claim 1, wherein the femoral component (102) has mounting portions for distal and posterior augmentation attachments.

4. 2. The femoral prosthesis of claim 1, wherein the tibial bearing (112) includes a 4° slope applied from a bottom surface of the tibial bearing (112).

5. 2. The femoral prosthesis of claim 1, wherein the tibial insert (104) has a posterior tilt of 7° on the articular surface (508).

6. The femoral prosthesis of claim 1 , wherein the femoral component (102) comprises a deeper patella groove.

7. 2. The femoral prosthesis of claim 1, wherein the tibial insert (104) includes an anterior and posterior chamfer.

8. 8. The femoral prosthesis of claim 7, wherein the anterior chamfer facilitates easy patellar movement and the posterior chamfer provides space for ligaments.

9. 2. The femoral prosthesis of claim 1, wherein when the flexion angle is 0°, the clearance between the box (202) and the tibial support (112) allows a maximum internal / external rotation of 1°.

10. 2. The femoral prosthesis according to claim 1, wherein the maximum internal and external rotations are in the range of 5.5° to 6° when the flexion angle is 90°.

Images