Total Knee Replacement

In this animated episode of eOrthopodTV, orthopedic surgeon Randale C. Sechrest, MD narrates the procedure to replace an arthritic knee with an artificial joint.

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 orthopaedics 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

Implant Components

Implanted

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

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

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

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

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

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

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

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

                       Bone Cuts                                                Implant Components                          Implanted Total Knee

 

Postoperative Care

After your surgery is completed, you will be transported to the recovery room for close observation of your vital signs, circulation, and sensation in your legs and feet. As soon as you awaken and your condition is stabilized, you will be transferred to your room. Below is an example of what you may see when you wake up:

  1. You will find a large dressing applied to your incision in order to maintain cleanliness and absorb any fluid.

  2. There may be a drain placed near your incision in order to record the amount of drainage being lost from the wound.

  3. You may be wearing elastic hose, and/or a compression stocking sleeve designed to minimize the risks of blood clots.

  4. Your doctor may prescribe a PCA (patient-controlled analgesia) that is connected to your IV. The unit is set to deliver a small, controlled flow of pain medication and is enacted when you firmly press the button on your machine. Press the button anytime you are having pain.

  5. You may have a catheter inserted into your bladder as the side effects of anesthesia often make it difficult to urinate.

  6. A continuous passive motion (CPM) unit may be placed on your leg to slowly and gently bend and straighten your knee. This device is important for quickly regaining your knee range of motion.

  7. When your leg is not in the CPM, you may be wearing a knee immobilizer to protect your knee when you stand up.

 

Rehabilitation Following Knee Replacement Surgery

In order for you to meet the goals of knee replacement surgery, you must take ownership of the rehab process and work diligently on your own, as well as with your physical therapist, to achieve optimal clinical and functional results. The rehabilitation process following total knee replacement surgery can be quite painful at times. However, if you commit to following your program and overcome the challenges in rehab, you will succeed in meeting the goals you set when deciding on surgery. The following outline will summarize the process you will adhere to during rehabilitation:

  1. In the Hospital
    • CPM (continuous passive motion) beginning day one or two
    • Ambulation with a walker or crutches (weight-bearing status determined by your surgeon)
    • Range of motion exercises
    • Edema control (ice, compression, elevation)
    • Instruction in home exercise program
    • Discharge goals are as follows:
      1. Independent getting in and out of bed
      2. Independent in walking with walker or crutches
      3. Independent in walking up and down 3 steps
      4. Independent in your home exercise program
      5. Ability to bend your knee 90 degrees
      6. Ability to fully straighten your knee
  2. At Home
    • Begin ambulation with a cane as tolerated.
    • Continue CPM (if necessary) and range-of-motion exercises.
    • Keep incision clean and dry; watch closely for signs of infection.
    • Continue home exercise program.
  3. Outpatient Physical Therapy
    • Advanced strengthening program, adding weights as tolerated
    • Stationary cycling
    • Walking program
    • Aquatic therapy program
  4. Long-term Rehabilitation Goals
    • Range of motion from 100-120 degrees of knee flexion
    • Mild or no pain with walking or other low-impact physical activities
    • Independent with all activities of daily living

 

Preventing Complications

In a small percentage of patients, as with all major surgical procedures, complications can occur. Below is a list of potential complications and steps you can take to minimize their occurrence:

Also known as deep vein thrombosis (DVT), this problem occurs when the large veins of the leg form blood clots and, in some instances, become lodged in the capillaries of the lung and cause a pulmonary embolism. The following steps may be taken to avoid blood clots:

IMPORTANT: If you develop swelling, redness, pain, and/or tenderness in the calf muscle, report these symptoms to your orthopaedic surgeon or internist immediately.

Although great precaution is taken before, during, and after surgery, infections do occur in a small percentage of patients following knee replacement surgery. Steps you can take to minimize this risk include the following:

Because your lungs tend to become "lazy" as a result of the anesthesia, secretions may pool at the base of your lungs, which may lead to lung congestion or pneumonia. The following steps may be taken to minimize this risk:

In some cases, the mobility of your knee following surgery may be significantly restricted and you may develop a contracture in the joint that will cause stiffness during walking or other activities of daily living. The following steps must be taken to maximize your range of motion following surgery:

  1. Thrombophlebitis
    • Blood-thinning medication (anticoagulants)

    • Elastic stockings (TED hose)

    • Foot and ankle exercises to increase blood flow and enhance venous return in the lower leg.

  2. Infection
    • Monitor your incision closely and immediately report any redness, swelling, tenderness, increased drainage, foul odor, persistent fever above 100.4 degrees Fahrenheit orally, or increasing pain.

      Speak with your physician for a complete list of potential complications. The information on this page is not intended to replace professional medical advice.

    • Take your antibiotics as directed and complete the recommended dosage duration.

    • Strictly follow the incision care guidelines your surgeon recommends.

  3. Pneumonia
    • Deep breathing exercises: A simple analogy to illustrate proper deep breathing is to, "smell the roses and blow out the candles." In other words, inhale through your nose, and exhale through your mouth at a slow and controlled rate.

    • Incentive spirometer: This simple device gives you visual feedback while you perform your deep breathing exercises. Your nurse or respiratory therapist will demonstrate proper technique.

  4. Knee stiffness
    • Strict adherence to the CPM protocol as prescribed by your surgeon

    • Early physical therapy (day one or two) to begin range of motion exercises and walking program

    • Edema control to reduce swelling (ice, compression stocking, and elevation)

    • Adequate pain control so you can tolerate the rehabilitation regime

 

 

 

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Video courtesy of eOrthopodTV.com.  All other materials copyright © 2015 Smith & Nephew, All Rights Reserved.