A Bi-CONDYLAR and BI-COMPARTMENTAL TOTAL KNEE REPLACEMENT

SYSTEM

TECHNICAL FIELD

The present invention relates in general to replacement prosthesis for joints, but more particularly to a replacement system for knee joints. BACKGROUND OF THE INVENTION

The knee joint connects three bones: the femur (thigh bone), the tibia (leg bone), and the patella (knee cap). When the hyaline articular cartilage is damaged by disease, injury or pre-mature wear from mal-alignment, it breaks down and obliterates the knee joint space. Diseases needing knee joint replacement or arthroplasty indude traumatic arthritis, osteoarthritis, rheumatoid arthritis, osteoarthritis, and rheumatoid arthritis. Surgical procedures that led to failures need also knee arthroplasty. The knee joint damage can be traditionally treated with physical therapy, pain medication, and steroid injection. When these treatment procedures fail, all or portions of the damaged joint surfaces may need to be replaced with an implant. The commonly available materials for artificial knee joint parts typically use plastic and metal which are rigid. Typically the current available total knee replacement systems has four-parts and includes a plastic patellar button, a metal femoral prosthesis, a flat metal tibial platform , and a plastic tibial spacer. Its sizes have also been based on Caucasian cadaver knees, which have larger aspect ratios than Filipino or Asian knees.

SUMMARY OF THE INVENTION

The main object of the present invention is to provide a bi-condylar bi compartmental total knee replacement parts and the procedure that will replace the diseased or damaged knee parts. The replacement parts had been reduced to only two: the femoral metal implant and the monobJock plastic tibial implant. Bone cement will anchor the implants to the connecting bones. The femoral implant and the tibial platform are provided with securing means on the surfaces thereof to prevent the rotation of said tibial platform with respect to the horizontal plane of said tibial and femoral bones.

T e metal part had been tested in animal rabbits and found not to result in any adverse tissue reaction (2). The sizes of these implants have been based on measurements of 72 pairs of Filipino cadaver knees and 200 radiographic plates of Filipino knees (3). Since Filipino knees are of similar sizes as other Southeast Asian people, they are referred to as Asian-fit. The total knee replacement parts had also been designed for either left or right Filipino knee. There are currently no available total knee replacement implants that had been based on Filipino cadaver knees. The knee prosthesis comes in three sizes: small, medium, and large sizes for Filipino or Asian knees. The sizes come in three kinds: small, medium, and large. For each size there is a right or left knee implant also. The surgical procedure to install these parts to the diseased knee was also modified to conform to the reduced parts. It does not require the replacement of the patella, and cutting the Posterior Cruciate Ligament (PCL).

Another object of the present invention to provide a two-piece knee replacement implant which will fit the left or right knees of Filipino patients. The available sizes were not available from previous designs. The previous designs were based on human knees which were larger than Filipino or Asian knees. Because the parts had been reduced from four to two, the surgical procedure will be faster and the instruments or equipment needed for installation simpler. The arthroplasty pieces have features that are designed to allow recipients more than 145-degrees range of motion allowing the recipient to kneel or squat. This larger range of motion is a feature added to the removal of the pain and dysfunction following the disease or injury of the affected knee joint. The two-piece implant in agreement with the current invention achieves greater range of physiologic motion while walking, kneeling or squatting and acts as a stronger knee replacement between moving bones while in motion. The shared features of the implant include: anatomic design symmetry based on Filipino knee aspect ratios and joint sizes, balanced rigidity with attachments to the distal end of the affected femur and the proximal end of the affected tibia, without resurfacing the patella and retaining the posterior cruciate ligament and durability which addresses and meets the needs for reconstruction thus far not found in previous designs.

Still, another object of the present invention is to provide for a total knee replacement system that is easy to produce and manufacture using locally available technology.

These and other objects and advantages of the present invention will become more apparent upon a reading of the ensuing detailed description taken in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the present invention for the total knee prosthesis in extended position;

Figure 2 is a top view thereof;

Figure 3 is a sectional view taken along line A-A of figure 2;

Figure 4 is a sectional view taken along line B-B of figure 2;

Figure 5 is a sectional view taken along line C-C of figure;

Figure 6 is an exploded showing in detail the femoral implant and tibial platform components of the present invention; and

Figure 7 is a bottom view of the tibial platform component of the present invention.

DETAILED DESCRIPTION

Before describing the present utility model in detail, it is to be that the phraseologies and terminologies used herein are for the purposes of description and should not be regarded as limiting.

Referring now to the drawings, wherein like reference numerals designate the components or elements throughout the ensuing enabling description, the present invention provides for a total knee replacement system designated as 10.

As shown in the drawings, the total knee placement system 10 includes a tibial platform component 11 and a femoral implant 12. The tibial platform 11 is secured to the tibial knee bone "T" and the femoral implant 12 is secured to the corresponding femoral knee bone "F". The femoral implant 12 is configured to rotate about the tibial platform 11 in relation to the movement of the knees as shown in figure 1 in extended position and figures 2 and 3 in flexion position.

Referring now to figure 6 and 7 in relation to figures 1 and 2, the tibial platform 11 is provided with a first securing means ^W S" disposed at the bottom surface 11a of the tibial platform 11 to prevent the rotation of the tibial platform 11 with respect to the horizontal plane of said tibial bone "T". Likewise, the femoral implant 12 is also provided with a second securing means "O" disposed on the top surface 12a of the femoral implant 12 to prevent the rotation of the femoral implant 12 with respect to the horizontal plane of the femoral bone "F".

Referring again to the drawings, the tibial platform 11 comprises of a continuous curved concave body 13 having a lateral articulating surface 14 and a medial articulating surface 15 at the posterior portion "P" and an articulating extension surface 16 extending from the lateral and medial articulating surfaces 14 and 15 towards the anterior portion "A" thereof. The tibial platform 11 further comprises of a raised portion 17 provided between the lateral and medial articulating surfaces 14 and 15, and a tibial stem 18 downwardly extending from the articulating extension surface 16.

As further shown in figures 1, 3 6 and 7, a locking means "L" is provided on the tibial platform 11 to enhance strength, stability to the knee replacement system 10, and to allow for radiographic referencing procedures, such as X ray films referencing. The locking means "L" includes at least a channel, preferably a pair of opposed channels 18a, provided along the tibial stem 18, fastening elements 19 such as screws, and a corresponding holes 16a and 16b provided on the articulating extension surface 16 to receive the fastening elements 19.

Referring now to figure 7, first securing means ^W S" which is provided at the bottom surface 11a of the tibial platform 11 comprises of a honeycomb- like structure 20 provided at the bottom surface of said tibial platform. The honeycomb-like structure 20 is defined a plurality of spaced apart notches 21, preferably of different sizes.

Referring again to the drawings, the femoral implant 12 of the present invention comprises of a continuous curved concave body 22 having a lateral condyle 23 and a medial condyle 24 at the posterior portion "P" and an extension surface 25 extending from the lateral condyle 23 and medial condyle 24 towards the anterior portion "A" thereof. The lateral condyle 23 and a medial condyle 24 further define lateral flexion surface 26 and medial flexion surface 27 thereon. The flexion surfaces 26 and 27 are adapted to flex along the lateral and medial articulating surfaces 14 and 15 of the tibial platform during the extension and flexion movements of the human knee. A space 28 is defined between the lateral condyle 23 and a medial condyle 24 and concurrent with the space 29 defined between the lateral and medial articulating surfaces 14 and 15. The space 28 defined between the lateral condyle 23 and a medial condyle 24 interlocks with the raised portion 17 of the tibial platform during the flexion movement of the human knees. The raised portion 17 also serves as support and stopper for the condyles. A pair of posts 30 and 31 is provided on the extension surface 25 adjacent to lateral condyle 23 and medial condyle 24.

As further shown in the drawings, the second securing means "O" comprises of spaced apart notches 32 provided on said extension surface 25 of the femoral implant 12. The pair of posts 30 and 31 also helps in enhancing the structural strength and stability of the knee replacement system 10.

The following is a diagram for the surgical algorithm for the knee replacement employing the parts of the total knee replacement system of the present invention. Pre-op

initialization Femoral imp ant available

Install Femoral imolant

Tibial implant available

Patients may complain of pain and knee joint dysfunction signalled by locking, clicking , or giving way. Knees may be swollen, mal-aligned or has slow crepitus (palpable crunching on movement). Pathognomonic symptoms for mentseal tearing include locking, clicking, giving way from wear or the twisting the knee. Diffuse aching may arise from arthritis or synovitis; anterior knee pain is generally patella- femoral, increased with stair use due to magnified body weight forces. Diagnosis should be accurate as distinguished from pain through the knee actually arising in the back caused by L4 nerve root irritation. Physical examination findings of pathologic knees include observed swelling, redness , or deformity. The patella inhabitation test position when positive, connotes retro patellar pathology, and often tracking problems that warrant soft tissue or bony correction. Improved limb alignment will increase benefits, and in part accrue from selective inflation of embodiments of the implants provided herein. X - rays of the knee are best evaluated in weight bearing views , and should be coupled with other data including MRI or CT. relative compartment narrowing suggests cartilage degradation. When the knee joint is damaged different treatment modalities can attempt to manage the condition including: supplements, prescription medication, fluid injections, and even steroid shots. All of these provide only temporary relief. An arthroplasty implant and procedure fit for Filipino or Asian knees is given in this invention to treat the above description.

A natural knee that is diseased or damaged can be exchanged with a total knee joint metal / plastic parts. The metallic femoral implant replaces the damaged femoral condyles, while a plastic tibial platform replaces the tibial cartilages. The implant can substitute the damaged femoral ends and tibial ends where drugs and other related modalities have failed to cure. Physiologic function can be restored by the artificial knee implants. When the cartilage is diseased or damaged, the femoral and tibial implant offers lining which the cartilage used to provide, thereby cushioning both the femoral and tibial joints and thus preventing bone and bone rubbing against each other during motion of the joint. The surface of bone osteotomized during the surgery will be replaced by the implant can provide movement between its opposing joint surfaces replacing the femoral condyle and tibial plateau. The gap (or gasps) filled by the ball or balls of the femoral implant(s) will provide movement between opposing implant joint surfaces substituting the femoral condyle or condyles and tibial plateau. The femoral implant has a grove along which the natural patellar cap can move during flexion (bending) or extension (straight). The tibial plateau may have some or all portions of the meniscal fibre cartilages, including all of said fibro cartilages, none of said fibro cartilages, or some portion thereof, are removed including a portion of the bony tibial plateau depending upon the size of the tibial implant and extent of the damage to the patient's fibro cartilage. When the knee is extended (straight) the implant buffers the femuro-tibial joint. When the knee is flexed, the implant ball apposition is more between the trochlear groove portion of the anterior distal femur (groove between the condyles on the " front of the knee") and the patella.

The anatomy of the knee is distinctive. The bones of the knee, the femur and the tibia, meet to form a hinge joint. The joint is protected in front by the patella (kneecap). The knee joint is cushioned by articular cartilage that covers the ends of the tibia and femur, as well as the underside of the patella. The lateral meniscus and medial meniscus are pads of cartilage that further cushion the joint, acting as shock absorbers between the bones. Ligaments support the knee. The collateral ligaments course along the sides of the knee and limit sideways motion. The anterior cruciate ligament, or ACL, attaches the tibia to the femur at the center of the knee. It limits rotation and forward motion of the tibia.. The posterior cruciate ligament, or PCL (located just behind the ACL) limits backward motion of the tibia. (1) These components of the knee, along with the muscles of the leg, work together to manage the stress the knee receives while walking, running and jumping. This anatomy must be accommodated by a comfortable implant that should not impede the natural joints' functions and movements.

Furthermore, the knee joints are able to withstand forces that vary depending on the particular movement of the individual not only in force per unit area, but also in vector direction as well. The joints of the knee work together to allow rotational movement in a screw like manner.

This is made possible by the tibia that is twisted relative to the femur. The joints are uniquely designed to allow this twist, but to limit the twist as well. The Asian-fit total knee implant can closely replicate the rotating, twisting, and stability of the natural knee. Thus, the implants as described herein are uniquely designed to account for these factors and should be able to maintain the natural function and movement of the knee. It should give the patient a more natural feel, enable the patient to feel stronger while dimbing, kneeling or squatting and there should be fewer dunks, pops or clicks.

As described herein, embodiments of the implant conform to the patient's own joint features not only in that it can be pre-molded and/ or adapted to mimic the contours of the patient's bone (femoral condyle ) , but it should be comfortable to the patient wearing it by allowing freedom of joint movement like his / her natural joint while preserving the joint and bone natural tissues as much as possible. Once an embodied of an implant described herein has been successfully implanted and the knee adequately rehabilitated, the appearance of a knee with such implant should resemble a normal joint. The knee may be distended due to saline and/or air insufflations. Knee implant patients will benefit from tailored rehabilitation programs, cautious weight bearing , early motion and potential the use of constant passive motion machine regiments. A post-surgical program will accompany the surgery to install this invention.

Additional advantages and modifications of the present invention will readily occur to those skilled in the art in view of these teachings. The present invention in its broader aspects is not limited to the specific details, representative contrivances, and illustrative examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit and scope of the general concept as defined in the appended daims and their equivalents.