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Implant Components

In the knee replacement procedure, each prosthesis is made up of four parts.

The tibial component has two elements – a metal base and a plastic insert – and replaces and the top of the tibia (shin bone). This prosthesis is made up of a metal tray attached directly to the bone and a high-density plastic spacer that provides the bearing surface.

The femoral component replaces the bottom of the thigh bone or femur. This component also replaces the groove where the patella or kneecap rides.

The patellar component replaces the surface of the knee cap, which rubs against the femur. The patella protects the joint, and the resurfaced patellar button will slide smoothly on the front of the joint. In some cases, surgeons do not resurface the patella.

Bearing Surfaces

One of the keys to a successful implant is its ability to withstand the rigors of daily activity, and central to that is the quality of the artificial surfaces that slide against each other, or articulate, in the new joint.

In knee implants, bearing surface options have been somewhat limited over the last few decades. The standard substance used for the femoral component is cobalt chrome, a metal alloy typified by its toughness and biocompatibility. However,even this high-quality industry standard has its shortcomings. Over time, this metal surface can become roughened by bone and bone cement particles trapped between the femoral component and the plastic tibial insert.

This roughened surface, when rubbing against the plastic component up to two million times per year, can more quickly wear out your implant. When that happens, you will have to undergo surgery to replace the plastic piece, the femoral component, and possibly even the tibial component. For this reason, implants have been shown to last between ten and fifteen years in the human body.

An exciting material to enter orthopedics in recent years is OXINIUM◊ Oxidized Zirconium. This remarkable material combines the strengths of ceramic and metal, such as wear-reduction and strength, but does not have the weaknesses, such as limited implant options and the possibility of fracture.

Zirconium is a biocompatible metal, similar to titanium. When the zirconium alloy undergoes a unique heating process, the surface of the metal transforms into a ceramic. Even though the new ceramic surface is 4,900 times more abrasion resistant than cobalt chrome, it retains the toughness and flexibility of the underlying metal.

Because it can achieve this remarkable reduction in implant wear without sacrificing strength as actual ceramic components do, oxidized zirconium implants have the potential to last significantly longer.

The JOURNEY II BCS Knee

Recent advances in biomedical engineering software have opened a new chapter on high performance knee implants.

One remarkable breakthrough has been the creation of the JOURNEY II BCS knee, a second-generation knee replacement that combines the stability and natural motion of the human knee with new low-friction materials that may extend the life of the implant.

While the lifespan of a knee implant is heavily influenced by the materials used to make it, the natural feeling of the implant during physical activity is dependent upon the way the patient’s muscles, ligaments and tendons are addressed during surgery and by the implant’s shape within the body after surgery.

As discussed previously in this booklet, the knee is a hinge joint, but it does not swing like a simple door hinge. It has a complex rotational motion that you don’t notice is there – but many patients know when it’s not there after total knee replacement. Traditional implants attempt to recreate this subtle swing-and-rotate action with either a rotating platform (a simple pivot point) within the implant or by requiring an angled alignment of the implant during surgery.

With these traditional knee replacement designs, the muscles and ligaments around your new joint have to work harder because the implant’s slightly unnatural shapes and resulting motion make these soft tissues move in unfamiliar, stressful ways. This leads to joint pain, muscle fatigue and the unnatural feeling patients experience while walking or bending in the months after their procedure.

The JOURNEY II BCS knee, on the other hand, is designed to reproduce the original internal shapes and angled forces of the human knee through its full range of motion – accommodating the swing-and-rotate of the joint with the same engineering principles your real knee currently uses. Because of this, your soft tissues don’t have to readjust to new shapes and forces after surgery and your stride can return to its natural rhythm.

The JOURNEY II BCS knee also reproduces the stability provided by your anterior cruciate ligament (ACL) and your posterior cruciate ligament (PCL). Your ACL and PCL are key to the stability of your real joint and contribute to natural motion when your knee is fully extended and fully bent. No other knee implant reproduces both functions.

The Procedure

Knee replacement surgery typically takes between one and two hours to complete. This section will provide you with a brief, easy-to-understand description of the surgical procedure. (Please consult with your physician for details regarding your specific procedure.)

Bone Cuts

An incision is made extending from the thigh, past the inside edge of the kneecap, and down to the shinbone.

The end of the femur is shaped in preparation for sizing the femoral trial component.

The top of the tibia is shaped for proper sizing of the tibial trial component.

Components

The trial units are put in place and the appropriate implant size is selected.

The knee is assessed for alignment, stability, and range of motion.

The underside of the kneecap is prepared and patella trial is selected.

Implanted Components

The trial units are removed and the final femoral, tibial, and patella components are implanted.

The incision is closed, a drain is put in, and the post-operative bandaging is applied.

As a patient considering knee replacement surgery, it is important to remember that you have choices.

In our VERILAST◊ Technology section, we discuss how the choice of materials used to make your implant can have a significant impact on both your implant’s ability to resist wear, and on your body’s ability to accept the implant if you have a metal allergy.

However, as important as your choice of implant materials is, it’s only part of the equation.

After all, no matter how much new technology goes into the creation of your implant, if your implant isn’t correctly aligned within your body, implant wear and performance will still be concerns.

For this reason, we developed VISIONAIRE Patient Match Technology – a system that uses your own MRI and X-Ray images to design and build surgical instruments customized specifically for your unique knee anatomy.

Important Safety Notes:

Knee replacement surgery is intended to relieve knee pain and improve knee functions. However, implants may not produce the same feel or function as your original knee. There are potential risks with knee replacement surgery such as loosening, fracture, dislocation, wear and infection that may result in the need for additional surgery. Longevity of implants depends on many factors, such as types of activities and weight. Do not perform high impact activities such as running and jumping unless your surgeon tells you the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if you do not follow your surgeon’s limitations on activity level. Early failure can happen if you do not guard your knee joint from overloading due to activity level, failure to control body weight or accidents such as falls. Talk to your doctor to determine what treatment may be best for you.

Our LEGION◊ CR Knee with VERILAST Technology was lab-tested to simulate the number of steps the average person takes in 30 years.

If knee replacement is in your future, you’ve come to the right place to learn about one of the truly significant advancements in joint replacement materials in the past 20 years, VERILAST Knee Technology.

Implant Technology

It’s important to remember that not every knee implant is the same. VERILAST Knee Technology directly addresses one of the most commonly cited concerns associated with knee replacement implants, implant wear.

Whether or not to undergo knee replacement surgery is a very important decision. No matter how statistically safe and successful knee replacement surgery has proven to be, every surgery has risks. Before making any surgical decision, conversations should take place with your family, your primary care doctor and your orthopedic surgeon to make sure that knee replacement with VERILAST Technology is the right course of action for your particular situation.

Important Testing Note

VERILAST knee wear testing and results apply only to the VERILAST LEGION CR Primary Knee System only. Extended lab-testing for other VERILAST knee systems have not been performed. The results of laboratory wear simulation testing have not been proven to predict actual joint durability and performance in people. A reduction in wear alone may not result in improved joint durability and performance because other factors, such as bone structure, can affect joint durability and performance and cause medical conditions that may result in the need for additional surgery. These other factors were not studied as part of the testing.

Important Safety Notes:

Knee replacement surgery is intended to relieve knee pain and improve knee functions. However, implants may not produce the same feel or function as your original knee. There are potential risks with knee replacement surgery such as loosening, fracture, dislocation, wear and infection that may result in the need for additional surgery. Longevity of implants depends on many factors, such as types of activities and weight. Do not perform high impact activities such as running and jumping unless your surgeon tells you the bone has healed and these activities are acceptable. Early device failure, breakage or loosening may occur if you do not follow your surgeon’s limitations on activity level. Early failure can happen if you do not guard your knee joint from overloading due to activity level, failure to control body weight or accidents such as falls. Talk to your doctor to determine what treatment may be best for you.

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Wimmer M A et al., “Joint motion and daily activity profile of total knee patients in comparison with the ISO knee wear simulator”. Paper 0159, 48th ORS, 2002.
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Naal F D et al., “How active are patients undergoing total joint arthroplasty? A systematic review”, Clin Orthop Relat Res, DOI 10.1007/s11999-009-1135-9, published online: 28 October 2009.

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