Shoulder Surgery

Hip Replacement

Knee Replacement

Knee Arthroscopy, Ligament Reconstruction & Knee Replacement

Zimmer Nexgen prosthesis, Zimmer Gender specific implants, Zimer,high flexion technology, MIS and minimally invasive technology. Conformis custom partial knee replacements.

South Valley Orthopedics & Sports Medicine strives to improve patient quality of life by using minimally invasive solutions and procedures with leading-edge advancement in surgery.

Minimally Invasive Knee Replacement Procedure - Candidate Profile

The decision to have a MIS™ total knee replacement procedure is up to you and your orthopaedic surgeon. Your doctor will consider a number of factors, including:

  • Medical history
  • Weight
  • Health status
  • Anatomical structure, including bone structure and type of arthritis

Symptoms

Your doctor must help you determine if you are a candidate for a Conformis custom partial knee replacement or a Zimmer® MIS Mini-Incision procedure. Knee replacement is considered when:

  • Joint damage is visible on x-ray
  • Episodes of pain, swelling, and stiffness in the knee are prevalent
  • Persistent pain and disability interfere with daily life activities
  • Mobility is extremely limited
  • Nonsurgical interventions, such as medication, physical therapy, and the help of a cane or other walking aid, are unsuccessful

To diagnose your condition, an orthopaedic surgeon will perform a thorough examination of your knee, analyze x-rays, and conduct physical tests. You will be asked to describe your pain, if you suffer from other joint pain, and if you have endured past injuries that may have affected your current knee condition. Your joints will then be tested for strength and range of motion through a series of activities, which include bending and walking. X-rays of your knee joint will indicate any change in size, shape or unusual circumstances.

Based on your examination, your surgeon will determine whether you are a candidate for the Mini-Incision knee procedure. While total knee replacement is a proven option to alleviate knee arthritis pain, your surgeon may also advise you on non-operative treatment options including anti-inflammatory medications or injections, physical therapy, or a cane to aid in walking.

During your consultation with your doctor. As with any surgery, there are risks involved. Some complications during and after surgery can include infections, blood clots, prosthesis loosening, and nerve damage.

Knee Replacement - Frequently Asked Questions

This page provides a brief introduction to knee replacement. It can help you make a list of questions to ask your doctor, but it is not meant to provide complete information. Check with your surgeon's office about more comprehensive resources and patient education materials.

What causes knee pain?

There are many different causes of knee pain, including injury, arthritis and infection.

Is there a cure?

It depends on the problem. Some knee pain can be treated through rehabilitation, other cases may require surgery.

What is a knee replacement?

In total knee replacement surgery, the parts of the bones that rub together are resurfaced with metal and plastic implants. Using special, precision instruments, your surgeon will typically remove the damaged surfaces of all three bones. The replacement surfaces will then be fixed into place.

The surface of the femur is replaced with a rounded metal component that comes very close to matching the curve of your natural bone. The surface of the tibia is replaced with a smooth plastic component. This flat metal component holds a smooth plastic piece made of ultra-high-molecular-weight polyethylene plastic that serves as the cartilage. The undersurface of the kneecap may also be replaced with an implant made of the same polyethylene plastic.

How do I know if I need a knee replacement?

If you have difficulty walking or performing everyday activities such as getting dressed, it may be time to consider knee replacement surgery.

Doctors generally try to delay total knee replacement for as long as possible in favor of less invasive treatments. However for patients with advanced joint disease, knee replacement offers the chance for relief from pain and a return to normal activities.

How do I prepare for knee replacement surgery?

If you and your surgeon decide that total knee replacement is right for you, a date will be scheduled for your surgery. Several things may be necessary to prepare for surgery. For example, your surgeon might ask you to have a physical examination by an internist or your regular doctor.

Because blood transfusions are likely to be needed during your surgery, you may want to donate one unit of your own blood, or possibly two units if your surgeon feels it is needed. All preparations for surgery should be discussed with your surgeon.

What happens during knee replacement surgery?

On the day of surgery, a small tube (intravenous line) will be inserted into your arm. This tube will be used to administer antibiotics and other medication during your surgery. You will then be taken to the operating room and given anesthesia. After the anesthesia takes effect, your knee will be scrubbed and sterilized with a special solution.

The surgery will begin with an incision over the knee that will expose the joint. When the bones are fully visible to the surgeon, special, precision guides and instruments are used to remove the damaged surfaces and shape the ends of the bones to accept the implants.

The implants are then secured to the bones. It might also be necessary to adjust the ligaments that surround the knee in order to achieve the best possible knee function. When the surgeon is satisfied with the fit and function of the implants, the incision will be closed.

A special drain may be inserted into the wound to drain the fluids that naturally develop at the surgical site. A sterile bandage will then be applied, and you will be taken to the recovery room, where you will be closely monitored. Your surgery will likely take between one and three hours, depending on your individual circumstances.

As your anesthesia wears off, you will slowly regain consciousness. A nurse will be with you, and may encourage you to cough or breath deeply to help clear your lungs. You will also be given pain medication. When you are fully awake, you will be taken to your hospital room. Your knee will remain swollen and tender for a few days.

What about Patient Specific Total Knee Replacement?

Orthopedic companies are now able to construct models that fit on an individual patients bone to guide the surgeons placement of the knee components. First the patient gets an MRI or CT Scan of the affected knee. The images are then sent to the specific orthopedic company, and a model of the bone is made. A reverse mold of the bone is also made with special slots in the mold that either act as a guide for pins or as guides for the bone cutting equipment. This technology is relatively new, however the accuracy of this technique closely matches that of existing techniques.

What type of knee does Dr. Harwood use?

Dr. Harwood utilizes the Zimmer platform of total knees in his patients. Currently Dr. Harwood implants the NexGen cruciate substituting (posterior stabilized) prosthesis. Additionally, in most cases he utilizes High Flexion and/or Gender Specific options in his cases. High Flexion prostheses allow for a greater amount of flexion, or bend, aiding in activities such as kneeling, sitting and squatting. In some cases a Gender Specific prosthesis may be used. This prosthesis was developed by Zimmer to address the differences between the anatomy of the male and female knee. Some knees have a narrower and thinner shape, and the Gender Specific knee allows for a better fit in these cases.

At times Dr. Harwood will perform a partial knee replacement, whereby only a portion of the knee will be replaced. Replacement of the patellofemoral joint (knee cap portion), the medial ( inside portion), the lateral (outside portion), or a combination of two of the three areas may be performed. In terms of the Patellofemoral Replacements, Dr. Harwood uses the Zimmer prosthesis.

Custom knee replacements, are they for real?

There has been increasing interest over the last several years in the possibility of truly custom prosthesis. Currently Conformis, a Boston Massachussetts based company, offers custom made replacements of one or two portions of the knee. The iUni and iDuo prosthesis are the answer for custom made partial knee replacements. Utilizing the nformation from a CT Scan, Conformis builds a 3 dimensional model of the knee. From pictures including the hip, knee, and ankle adjustments for the alignment of the specific limb is accounted for. A custom made femoral component is then designed to replace the missing cartilage for the diseased portion of the knee. A small resection of bone is made on the tibial side, so as to restore proper balancing of the ligaments in the knee. Lastly custom polyethelene spacers are produced that allow for fine tuning of the ligament balancing of the individual knee. This is a very bone conserving prosthesis, saving roughly 98% of the original bone. Every implant is custom made, allowing for the restoration of near normal kinematics of a specific knee.

How is the implant affixed in the body?

Generally, implant systems are affixed to the body in one of three ways:

1. Cemented with bone cement
2. Cementless (biologic ingrowth)
3. Combination of 1 & 2

Bone Cement

A special type of acrylic bone cement may be used to secure some or all of the implant components to the bone. If used, the bone cement takes about 15 minutes to set.

Cementless

In other cases, the implants may be implanted into the bone without cement. These components have a special porous coating that allows tissue to grow into it for fixation.

Combination

In some cases, your surgeon may choose a combination of cement and cementless attachment, depending upon the implant components and the condition of the bone around the knee joint.

The decision as to whether to use a cemented or cementless component depends upon many factors, including the intended use of the product, surgeon philosophy and the patient’s condition.

What can I expect after knee replacement surgery?

When you are back in your hospital room, you will begin a rehabilitation program that will help you regain strength, balance, and range of movement in your knee. This program will be designed specifically for you. It may include a machine, called a continuous passive motion machine that automatically moves your leg to help reduce stiffness.

Your physical therapist will help you perform appropriate exercises. About 24 hours after surgery, you will probably be asked to stand. Within the next 24 hours, you will probably begin to walk a few steps with the help of a walker. You will be discharged as soon as your surgeon determined that you have recovered sufficiently. You can expect to stay in the hospital for about three days after your surgery. You may or may not be transferred to a rehabilitation facility for a few more days, as determined by your surgeon. Your bandages and sutures will usually be removed before you leave the hospital. At home, you will need to continue your exercises. Your physical therapist will instruct you about proper home care, and may continue to work with you.

Bony Stress Pain: Perhaps the biggest surprise after surgery is the bony stress pain that patients feel for the first 3 months. A knee replacement entails removing about 6-8 mm of bone and replacing it with metal. The metal is about 100 times stiffer than the bone that it is replacing. Therefore, the knee joint has to adjust to the new stiffness of the metal replacement. Bone is constantly remodeling itself, but this is a slow process (fracture remodeling takes 3-6 months). The bone around the new knee replacement remodels according to the new stress it sees, but this process also takes a few months. Knee replacement patients feel this remodeling pain typically as a delayed activity related throbbing or achy pain deep in the knee joint. A typically example is 4 weeks after surgery, a knee replacement patient might walk for 30 - 45 minutes through a grocery store without much discomfort, but later that night they feel like their knee is pounding and they have a hard time getting to sleep. This delayed pain usually disappears by the next morning. As the bone remodels over the 3-4 months after surgery, the amount of activity required to generate the pain increases and the intensity of the pain decreases. The factors that cause the bony stress pain are typically related to the quality of the bone and the stress across the joint, but not the surgical technique. Patients with weak bones and/or heavy set patient are at greater risk for bony stress pain. Patients who try to do too much activity too quickly are also at a greater risk. All surgeons have some of patients that have little to no stress pain, while others have a considerable amount of stress pain. The occurrence of this stress pain is difficult to predict and explains the large variation in recovery between patients. It also makes short term comparisons between surgeons' outcomes difficult.

Lateral Numbness: Most knee replacement incisions are vertical. A small patch of skin to the outside of the incision (lateral) is typically numb following the surgery. Typically this is a result of trauma to small nerve branches that course across the front of the knee. This numbness seldom bothers patients and often returns to normal. There is nothing that can be done during surgery to prevent this minor numbness.

Noise: Knee replacements often initially make a clunking noise that is typically not painful. Usually that noise diminishes with time, but occasionally the noise will persist. The noise does not usually represent a problem with the components and typically occurs when the replaced patella surface moves along the trochlear grove of the femoral component with knee extension and flexion.

Activity Level: Knee replacements allow a patient to resume all normal daily activities. Sports like swimming, biking, golf and doubles tennis are also possible after 6 months or so. Vigorous activities like basketball, water skiing, marathon running, and football are not recommended.

How soon can I return to normal activities after surgery?

Within six weeks after surgery, most patients are able to walk with a cane. You will probably feel well enough to drive a car within seven to eight weeks after surgery.

In most cases, successful joint replacement surgery will relieve your pain and stiffness, and allow you to resume many of your normal daily activities. But even after you have fully recovered from your surgery, you will still have some restrictions. Normal daily activities do not include contact sports or activities that put excessive strain on your joints. Although your artificial joint can be replaced, a second implant is seldom as effective as the first.

Will an implant set off a metal detector?

Since knee implants are made of metal, there’s a chance they could set off metal detectors.

Patients have reported mixed experiences at airports: some detectors go off and some don’t.

You may be provided with a special card to keep in your wallet explaining that you have a knee implant.

How common is knee replacement surgery?

Knee replacement is a routine surgery performed on over 600,000 people worldwide each year. Over 90% of people who have had Total Knee Replacement experience an improvement in knee pain and function.

How old is the average patient?

In the U.S., the average joint replacement patient is around 65-70 years old, however patients of all ages have received knee implants.

What about sex?

Doctors generally allow patients to resume sexual activities as soon as they feel able. In the months following surgery, patients are generally advised to take it easy and modify their positioning to keep pressure off of the joint while it’s healing. As always, it is best to consult with your doctor about what’s safe for your particular condition.

I am knock-kneed/bow-legged. Can knee replacement surgery correct this?

Many people are born with a natural tendency toward knock knees or bowleggedness. However, severe arthritis can lead to an uncomfortable degree of misalignment.

One of the goals of total knee replacement is to restore your body’s natural alignment. Zimmer has special instrumentation to help surgeons replicate natural, optimum alignment.

How long will a joint replacement last?

Longevity of the prosthetic knee varies from patient to patient. It depends on many factors, such as a patient's physical condition, activity level, and weight, as well as the accuracy of implant placement during surgery. It is useful to keep in mind that prosthetic joints are not as strong or durable as a natural, healthy joint, and there is no guarantee that a prosthetic joint will last the rest of a patient's life.

Today, total knee replacement has become a common and predictable procedure. Many patients enjoy relief from pain and improved function, compared to their status before surgery. As a result, some patients may have unrealistic expectations about what the prosthetic knee can do and how much activity it can withstand. As with any mechanical joint, the knee components move against each other. Natural fluid in the joint space, called synovial fluid, helps to lubricate the implants just as it lubricates the bones and cartilage in a natural joint. Still, the prosthetic components do wear as they roll and slide against each other during movement. As with car tires or brake pads, the rate of wear depends partly on how the knee joint is used. Activities that place a lot of stress on the joint implants, as may be the case with heavier and more active patients, may reduce the service life of the prosthesis. Implant loosening and wear on the plastic portions of the implant can lead to the necessity for revision surgery to replace the worn components, or all of the components. Your doctor will be in the best position to discuss these issues with you, taking into account your particular clinical circumstances, the type of implants used, and your post-surgical lifestyle.

Talk with your doctor about the following points, and how they might affect the longevity and success of your knee replacement:

  • Avoiding repetitive heavy lifting
  • Avoiding excessive stair climbing
  • Maintaining appropriate weight
  • Staying healthy and active
  • Avoiding "impact loading" sports such as jogging, downhill skiing and high impact aerobics
  • Consulting your surgeon before beginning any new sport or activity
  • Thinking before you move
  • Avoiding any physical activities involving quick stop-start motion, twisting or impact stresses
  • Avoiding excessive bending when weight bearing, like climbing steep stairs
  • Not lifting or pushing heavy objects
  • Not kneeling
  • Avoiding low seating surfaces and chairs

What are the possible complications of a Total Knee?

Blood Clots: Blood clots in your leg veins are possible after any surgery on the lower extremities. The occurrence of blood clots can be minimized with blood thinners, foot pumps, compression stockings, and early mobilization. The main danger of blood clots is if they dislodge and travel to your veins in your lungs. This phenomenon is called a pulmonary embolus and can result in respiratory difficulty, chest pain, or even death. Blood clots may or may not hurt or cause swelling in your leg and can occur anywhere in either leg. If you have unexplained pain or swelling in your legs, let Dr. Harwood know as he may order a duplex ultrasound to look for a blood clot. If you feel chest pain or breathing difficulties, you should call 911 and then call Dr. Harwood. The risk of these clots causing death has been drastically reduced, and is less than 0.1%. The treatment for a proven blood clot is additional blood thinners for 3-6 months, and occasionally a filter in your veins.

Infection: Antibiotics are given before and after surgery to decrease the risk of infection, but an infection still can occur immediately or even years after the surgery. If an infection occurs, early detection and treatment is crucial. It is usually treated with another surgery to remove infected tissue and often the prosthesis as well. If the components are removed, a revision knee prosthesis can sometimes be inserted months later if the infection clears, but sometimes the patient is left without a knee joint or with a fusion of the knee. Although patients rarely have life threatening problems from their joint infection, an infection is a devastating complication.

Stiffness: Patients may experience stiffness in the knee joint after surgery. A knee that is stiff before surgery is more likely to remain stiff after surgery; however, any knee can lose motion after surgery. It is imperative that patients work hard with the physical therapist after surgery to prevent the knee from getting stiff. Occasionally, a patient may have their knee manipulated under anesthesia, or bent, to regain the motion lost in the post-operative period.

Component Loosening: Occasionally the implanted components will loosen from the bone and change position. Component loosening can occur years after the surgery from wear debris from the plastic liner, or as a result of the failure of the bond between the cement used in surgery and the prosthesis. The motion of the loose component may cause pain with activity and require another surgery to revise the components.

Component Wearing out: A knee replacement is compromised of a metal femoral component, a metal tibial component, and a plastic insert. The plastic insert can wear out over time, usually 15-20 years. Just like the tires on a car, the more miles a patient puts on their total knee replacement, the sooner the plastic insert might wear out. The plastic insert can be replaced, if necessary.

Nerve Injury: Although extremely rare, nerves to your leg and feet can be injured during surgery. These nerves may or may not recover by themselves. If they do not, you may need a brace for your ankle, and your walking ability could be limited.

Ligament Injury: Although extremely rare, ligaments or tendons surrounding the knee can be injured during surgery. A ligament injury can usually be repaired during the surgery, but it may change the post-operative course. The ligaments most commonly injured are the patella tendon or the medial collateral ligament. A brace may be required to help protect the ligament as it heals after an injury.

Bleeding: Blood vessels around the knee are rarely damaged by the surgery. If excessive bleeding occurs during or after surgery, the patient may require a blood transfusion. Occasionally, blood gathers in the knee even if no major blood vessel is damaged, forming a collection known as a hematoma. At times the hematoma may have to be washed out in surgery.

Limp: The limp that most people have before the surgery usually persists until the muscles become stronger after surgery. It sometimes never goes away, and sometimes the surgery creates a new limp. Most people's gait (walk) is greatly improved by joint replacement surgery though.

Fracture: The femur, patella, or tibia can crack when preparing the bone for insertion of the components, during the insertion of the components, or even years after the surgery. Fractures are usually treated with screws and plates, wires or cables, and occassionally changing out of the components. Luckily fractures around the knee and prostheses usually heal.

Osteolysis Polyethylene bearings can wear out over many years and cause osteolysis which is the body's response to the plastic wear debris from the knee replacement. The body tends to attack the tiny plastic particles and inadvertently causes the bone around the knee joint to weaken. The weakened bone can lead to fractures or component loosening.

Dislocation: The femoral component rarely can dislocate from the tibia component. Knee replacements with a rotating platform (mobile bearing) can also dislocate if the bearing surface rotates more than it should. If your total knee dislocates, your leg would be manipulated under anesthesia or sedation to place the components back together. Occasionally, unstable knee replacements need to be revised to correct this condition if it keeps occurring.

Need for Further Surgery: Though uncommon, knee replacements occasionally fail sooner than expected. Some other problems can also make further surgery necessary, including abnormal bone formation and irritation of the soft tissues.

Death: Though very rarely, patients have died following knee replacements. This is typically due to underlying medical or heart problems that arise or worsen from the stress placed on the body after the surgery.

Other Problems: This list covers only the most frequent problems encountered during knee replacement surgery. Just as every patient is unique, so are many problems and complications.

It is important to remind patients that although many complications have been reported in the orthopedic literature, most are minor and rare. Total knee replacement remains one of the most successful operations that orthopedic surgeons perform.

Information provided by Zimmer Orthopedics