Dominick
Semenza, 58
Knee Replacement

Listen to Dominick

Problem: Osteo-arthritis of the knee. "Getting in and out of the car was very painful. Often my wife had to drive because I cound not operate the pedals. Stairs were a problem."

Solution: Uni-compartmental (partial) knee replacement.

Result: "I'm ecstatic, no pain. I kept my job and my norrmal activities are just as they were before I had the problem. My knee feels great. I am able to function totally on-the-job and I'm able to do work around the house."

Barbara Flynn, 52
Knee Replacement

Listen to Barbara

Problem: Severe osteo-arthritis of both knees. "The pain had got to the point where it was disturbing my sleep, it was disturbing my daily activities, climbing stairs was awful. The thought of going to an audition where I'd have to go up and down several subway steps and all that, I thought...oh I'll just skip that audition."

Solution: Total knee replacement of both knees.

Result: "As an actress in New York City you have to be able to bend, move and negotiate backstage, go up stairs, and do so gracefully and with confidence. And now I can."

Resurfacing and Partial Knee Replacement Implants

Sometimes the deterioration of the knee joint is such that total knee replacement can be avoided and your surgeon may suggest resurfacing or partially replacing components of your arthritic knee. Preserving healthy bone stock is especially important to younger and more active individuals.

This device, which is modified for each individual, allows patients to return to light to moderate physical activities in short time. It can delay the need for further surgery by redistributing joint stresses and preserving the bone structure in the joint. The device closely matches the normal joint geometry, permitting the femur (thigh bone) to articulate against a smooth implant surface. Because the implant conforms to the bony structure of the tibia, it stays in place without the need for cement or screws.

Knee Interpositional Device
(ConforMIS Inc.)

Uni-compartmental
Partial Knee Replacement

A partial knee replacement -- also called a uni-compartmental knee replacement -- involves putting an implant on just one side of the knee, rather than over the entire surface of the knee joint. Think of the knee as having three compartments: an inside, outside, and a front compartment for the kneecap. Most frequently, it is the inside compartment that becomes arthritic. A uni-compartmental knee replacement is done if part of the knee joint is damaged by arthritis and the other compartments have healthy, normal cartilage.

By retaining undamaged parts of the knee, the joint may bend better and function more naturally.

In a healthy knee, the meniscus serves as a shock absorber between the ends of the bones. The implant to the right features an artificial meniscal bearing designed to glide freely throughout the knee's range of motion, more closely replicating normal movement. The free floating nature of the device also improves durability of the implant.

The implant to the right is designed using Computed Tomography (CT) images of the patient's knee. The implant is manufactured using anatomical information derived from these images, thereby achieving a custom fit for each patient.

The advantage of this type of implant is that only the damaged cartilage from the weight bearing portion of the femur is removed. It is resurfaced with a cobalt chrome implant that conforms precisely to the anatomy of the knee. The tibial component is made of polyethylene and only requires minimal bone removal to secure the implant.

Partial Knee with Floating
Artificial Meniscal Bearing
(Biomet Inc.)

Uni-Compartmental
Implant for the Knee
(ConforMIS Inc.)

As osteoarthritis progresses, and the patient is no longer a candidate for a uni-compartmental implant, a total knee replacement has been the only treatment option available.

The bi-compartmental implant was developed to address this particular need, that is, when a standard uni-compartmental procedure is not indicated and a total joint replacement is not required or desired, for example due to disease in only two compartments or younger age.

The implant shown here is made specifically for an individual patient from their CT scan. Its unique design preserves the unaffected portions of the knee, maintaining the stability and natural properties of the joint.

Bi-Compartmental Resurfacing
Implant for the Knee
(ConforMIS Inc.)

Total Knee Replacement Implants

A diagnosis of advanced osteoarthritis of the knee will indicate the need for total replacement of the knee joint. Based upon your age and lifestyle, there are several design options to choose from that will help you return to an active enjoyable life.

The polyethylene cushion may be part of the platform (fixed) or free to move on a metal base (mobile).  Most people get a fixed-bearing prosthesis that reduces knee pain dramatically and may last for many years.  If you are younger, more active and/or overweight, sometimes a doctor may recommend a mobile-bearing or a rotating platform knee replacement designed for potentially longer performance with less wear.  Doctors also consider gender, occupation, disability level, pain intensity, interference with lifestyle and other medical conditions in selecting the appropriate prosthesis.

Fixed Bearing
(DJO Surgical)

Medial Pivot 

The Medial-Pivot knee replicates the rotating, twisting, bending, flexion, and stability of your natural knee, so it feels more like your natural knee. A normal knee actually pivots on its medial (inner side) condyle. When the knee flexes, the lateral (outer side) side rolls back while the medial side rotates in one place.  This design "stays put" or is more stabile during normal knee motion as opposed to sliding forward slightly.

Advance Medial-Pivot Knee
(Wright Medical)

Rotating Platform and
Mobile-Bearing

Knee implants imitate the motion of your natural knee. In the Rotating Mobile Knee prosthesis, the polyethylene insert can rotate slightly around a conical post.  It also slides back and forth on the tibial tray.  This allows the knee to twist and turn (called rotation), as well as move back and forth, flexing and extending (called articulation). The insert absorbs forces across a larger contact surface, helping reduce the amount of wear to the bearing and loosening in places where the implant attaches to bone. However, compared with Fixed-Bearing designs, Mobile-Bearing knee implants are less forgiving of imbalance in soft tissues. They may increase the chance of dislocation and may cost more than Fixed-Bearing implants.

Rotating Platform / Mobile-Bearing
(DJO Surgical)

Posterior Cruciate Ligament (PCL)-Retaining or Substituting

The Posterior Cruciate Ligament is one of the major ligaments in the knee. It provides support and stable movement of the knee. In total knee replacement surgery, the PCL can be kept or removed and this choice depends on the condition of the PCL, the type of knee implant or the type of surgery the surgeon likes to do.  Each of these designs has advantages and disadvantages. Surgeon preference depends on his or her training and the clinical situation.

PCL-Retaining

In PCL-Retaining designs, rearward movement of the tibia is resisted by an intact PCL, which creates stability.

PCL-Substituting 

PCL-Substituting knees (also called posterior stabilized knees) have a raised sloping surface or a polyethylene post that compensates for the missing PCL to give your knee more stability. 

PCL-Substituting
(Wright Medical)

Special Need Knee Implants

Narrow Femur vs.
Normal Femur

People with smaller skeletons present challenges that require the adoption of implants constructed for their special needs. Research shows that regular-sized implants may overhang on the bone and lead to soft tissue interference or mid-flexion instability in those people with narrow femurs.

Implant manufacturers are now introducing special need implants for smaller than average patients. These new implants (represented in teal in the image to the right) are designed to accommodate those male or female femora with smaller than average dimensions. This helps ensure the special need patient will receive the best implant fit possible.

Special Need - Narrow Femur
(Wright Medical)

Special Need Implant Patient Testimonials

"My new knees brought me back to life. I didn’t even realize I had lost my ability to live until I had surgery because the transition happened so slowly. I feel like I am part of the human race again, and it feels good.”
Sam ...read more...

"I am very excited for everything I can now do, like walking around during lunch, working in the yard, having a better social life and even doing household chores. I am so happy that I giggle all the time.”
Kelly ...read more...