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Why Robotic Partial Knee Replacement?

The answer to the questions are related.

1) "Why would you resurface only part of the knee, when you could replace the entire thing?" 
2) "Why do you use a robot in the OR?"

The answer to the questions are related.

Robotic Partial Knee Replacement (also known as MAKOplasty) is a procedure for knee arthritis where only the arthritic portion of the knee is resurfaced while the remainder of the knee is left intact. It applies robotic technology to partial (or unicondylar) knee replacement. So to answer the questions, you need to understand why partial knee replacement may be preferable to total knee replacement AND why robotic techniques improve partial knee replacement.

“Why would you resurface part of the knee, when you could replace the entire thing?”


Deciding between Partial

Knee Replacement and Total Knee Replacement

Total Knee Replacement

Total knee replacement (TKR) is an excellent operation and one of the most successful procedures developed in the 20th century. However, total knee replacement often does not meet the expectations of those who currently undergo the procedure. Designed to allow patients to walk but not to run or play sports, the modern day total knee replacement removes the major ligaments in the knee (the ACL and PCL for example). Recent studies have demonstrated no functional limitations during swimming and biking; however, significant limitations were noted during more strenuous

activities such as kneeling, squatting, moving laterally, turning and cutting, carrying loads, stretching, leg strengthening, tennis, dancing, gardening, and even sexual activity(1). Increasingly, this operation is performed on younger patients with over 40% of total knee replacements performed in patients under the age of 65 years old (there has been a 3 fold increase in TKR for this group over the last decade)(2)! The demands of this group often include a rapid return to work, participation in sports, and normal or near normal knee function.

Unfortunately expectations are not always met with TKR. Indeed 15-25% of patients who undergo TKR would not do the operation again(3)!! This is particularly sobering considering that we will spend up to 1% of the GDP on this operation in 2030. An emerging alternative to TKR is partial knee replacement. With this strategy, only the damaged portion of the knee is resurfaced; this is akin to filling a cavity rather than capping the entire tooth (as is the case with TKR).

Partial Knee Replacement

With Partial Knee Replacement (PKR), only the arthritic region of the knee is resurfaced, conserving the central ligaments of the knee (the ACL and PCL) as well as near normal knee motion. Partial Knee Replacement was nearly abandoned over 40 years ago due to concerns about durability. In these early days, the materials and fixation were not developed enough for a partial solution to provide long lasting pain relief. However, over the past quarter century, the material and fixation improvements pioneered for total knee replacement have resulted in durable solutions for partial replacements as well.

Partial knee replacement is not possible for all patients with arthritis; indeed, it is indicated when the arthritic condition is fairly localized. However, when it is appropriate, it is important to educate patients of the pros and cons of partial vs total knee replacement.

Pros and Cons of Total Knee Replacement vs Partial Knee Replacement

Here is a list of the issues that are important to my patients and a review of the pros and cons of the two operations. The choice is personal as different patients have different goals and realities. Often, either operation would appropriately service the needs of an individual.

Click on the topics below for a direct comparison between Total & Partial Knee Replacement.

  • Why should I come to HSS for my surgery?
    Hospital for Special Surgery more joint replacements of any hospital in the world. This allows us to optimize your care in every way. It is well established that fewer post-operative complications occur if surgery is performed at a joint replacement center. HSS has been rated the top orthopedic hospital by US News and World Report for the last five years. Our nursing staff has also been recognized with the prestigious Magnet Award for Nursing Excellence. At HSS, you will find the best surgeons, the best hospital, and the best nurses -- a winning combination for successful outcomes.
  • How long will I be in the hospital?
    After partial knee replacement, patients usually go home the same day or spend the night in the hospital.
  • What can I expect in the first couple weeks after the surgery?
    For 1-2 weeks after surgery, your activity level is usually limited, however, you will be able to walk independently and do normal household chores. You may leave the house once you feel safe using the cane.
  • What can I expect at 6 weeks post-op?
    Within 6 weeks, you will have resumed most of your normal activities. Squatting and kneeling will come with time.
  • When can I return to work?
    It depends on your occupation. It is never a mistake to take more time off in the beginning of your recovery, as it will give you time to focus on your surgery. I recommend taking at least 1-2 weeks off for partial knee replacement. Keep in mind that you may still be using a cane at 1-2 weeks and it may be difficult to commute.
  • When can I drive?
    You should not drive as long as you are taking narcotic pain medication. If it is your left knee, you can resume driving when you are off the pain meds. If it is your right knee, I usually allow driving 2-4 weeks after partial knee replacement.
  • When can I play golf after partial knee replacement?
    Typically patients are able to get back on the golf course 4-6 weeks after surgery, albeit with some pain and stiffness. Be patient - at 3 months, patient usually feel much more comfortable playing golf or tennis than they do at 6 weeks.
  • How long should I use the pain medication?
    This is different for each patient; some are able to use Tylenol or Advil after you leave the hospital, and others require pain medication as needed for 1-2 weeks. A general rule is that you should try to decrease your use of these medications as time passes.
  • When can I shower?
    I do not like your stitches or staples to get wet. Therefore, you may shower when you get home, but the incision will need to be covered. I recommend using saran wrap around the area to prevent it from getting wet. The stitches or staples will be removed at the first follow up appointment 7-14 days after the surgery; thereafter, it is safe to get the incision wet.
  • Is there a better time of year to have the surgery?
    This is a personal decision; some patients like to have the surgery in good weather so that they may walk outdoors as part of their recovery; others prefer to do the surgery in the winter so that they may recover in time to participate in springtime activities.
  • Do I need a special card to tell the airport screeners that I have a metal implant?
    You do not need a card to get through the airport; however, your implant will likely set off the metal detector. In this day and age, you will need to be hand-screened, so please leave extra time when you travel. We do provide an implant card for your convenience, which will be available postoperatively.
  • Can I get an MRI?
    Yes, MRI are perfectly safe with a partial knee replacement. An MRI in the area of the joint implant, however, will not yield good pictures because of artifact created by the metal. MRI of a joint replacement should be performed at a facility with experience with techniques used to suppress the metal artifact.
  • When should I go to outpatient therapy?
    I like to see you in follow up before you go as an outpatient; that way I can tailor your PT to what you need. However, if you feel that it is essential that you begin outpatient PT right away, you can call my office and we will provide a prescription and a list of places.
  • I feel "clicking" inside the knee, is this normal?"
    The clicking is a result of the soft tissue moving across the joint, or the metal parts coming into contact with one another. This sensation usually diminishes as your muscles get stronger.
  • My knee still feels stiff 6 weeks after the operation - is this normal?
    Surgical healing usually takes 6-8 weeks. However, the tissues remain swollen which can cause discomfort for some time. This is usually manageable with over the counter medications like Aleve or Tylenol although sometimes prescribed pain pills are necessary. Over time, the knee tissues begin to soften and become more natural.
  • I am experiencing a lot of swelling, is this normal?"
    Fluid can accumulate in the legs due to the effect of gravity. It is not unusual that you didn't have it in the hospital, but it got worse when you went home (because you are doing more!) To combat this, you should elevate your legs at night by lying on your back and placing pillows under the legs so that they are above your heart. There are also TEDS stocking (the white stockings from the hospital) that you can put on during the day - have someone help you on with them in the morning, use them during the day, and then take them off at night. If you did not get the TEDS from the hospital, you can purchase knee high, medium (15-20 mm Hg) compression surgical stockings at most drug stores.
  • I notice an area of numbness around my knee - is this normal?
    You may notice a small area of numbness on the outside area of the knee incision. This may or may not resolve over time.
  • When can I go to the dentist?
    Please wait until 3 months after surgery, as the joint is still healing and there is increased blood flow to this area.
  • Can I travel?
    In general, I like to see you before you fly. If you are traveling by car, you should be sure to take frequent breaks so that you don't feel too stiff when getting up. On an airplane, I like you to wear compression stockings (if within 1 month postop), and take a couple of walks during the flight. Having an aisle and bulkhead seat will help you get more space. If you are going to fly within 6 weeks of the surgery, I recomend blod thinners to prevent blood clots. Call the office for more information.
  • Should I be taking any medications or supplements for bone health after a partial knee replacement?
    Yes, I recommend that everyone take calcium and vitamin D to help maintain bone strength. Generally 1000-1500 mg of calcium citrate and 400 IU of Vitamin D are adequate. Occasionally I will also prescribe a medication to help promote bone strength.
  • Can I run after surgery?
    I recommend minimizing high impact activities after partial knee replacement. The parts are man-made and have a finite life span. High impact activities are those where the entire body is off the ground and all your weight lands on one leg. As such, running, jumping, and even jogging are high impact while cycling, stairmaster, elliptical, golf and walking are low impact. As a general rule, I recommend limiting high impact activities so as to extend the longevity of your implant.
  • How long does the implant last?
    All implants have a limited life expectancy that depends on several factors including a patient's weight, activity level, quality of bone stock and compliance with the doctor's orders. However, alignment and positioning are also are very important factors affecting the life expectancy of an implant. The goal of the robotic partial knee replacement is to achieve the absolute best alignment and positioning for your implant to help it last as long as possible. Most studies have demonstrated a 90% implant survival rate at 10 years.

Summary - Deciding Between Partial and Total Knee Replacement

Both partial and total knee replacement can provide durable pain relief and improve function in patients with knee arthritis. Partial knee replacement is not appropriate for all patients with knee arthritis and may only be possible in 10-30% of patients.

Total knee replacement is a very durable operation that can last for 30 years. It predictably allows patients to walk, hike, ride a bike, and swim. It is less predictable in return to sporting activity. The recovery is long and arduous.

Partial knee replacement has a quicker recovery, permits rapid return to work, and often allows patients to expand their sports participation. In addition, the surgery has fewer risks than total knee replacement and is less costly to the patient. Though many studies have demonstrated excellent and long lasting durability, I still caution patients that partial knee replacement has a higher revision rate than total knee replacement.

“Why do you use a robot in the OR?”

Domo Arigato Mr Roboto (Thank you very much, Mr. Robot) -

The emergence of Robotic Knee Resurfacing

A Technical Problem

A downside of Partial Knee Replacement is that is may not be as long-lasting as Total Knee Replacement. One of the primary reasons for this is that Partial Knee Replacements can fail quickly if they are poorly positioned at the time of surgery. Indeed, PKR is a technically demanding procedure, and prone to surgeon error. Rather than making perpendicular cuts to remove the entire ends of the knee (as we do in total knee replacement), the surgeon has to preserve the inner ligaments (ACL and PCL) as well as the dimensions of the native knee in partial knee replacement. Technical error is a major source of failure in partial knee replacement. There are two main solutions to this problem: robotics and surgeon experience.

The Robotic Solution

I have pioneered the use of robotics for partial knee replacement (I call the procedure robotic partial knee replacement- it is also known as MAKOplasty) because robotics affords a level of precision and reproducibility that cannot be achieved with manual techniques. I have shown that implant position is 3x more accurate and less variable with robotic techniques

compared to manual tools and that alignment can be controlled with robotic resurfacing(14,15). My colleague in England, Justin Cobb, demonstrated in a prospective randomized trial that robotic partial knee resurfacing achieved accurate placement of the implant 100% of the time compared to only 40% with manual techniques(16). With robotics, I can reliably get it right the first time.

I have been using robotic assistance for more than a decade. On a preoperative CT scan, I make a virtual model of a patient's knee. On this model, I can virtually place the implants and position them perfectly, customizing them precisely for the individual anatomy. This allows me to test many different positions until I find the "sweet spot" for the implant - indeed, I will often perform the surgery on the computer 20 or 30 times until the implants fit just right. This ability to perform the surgery "virtually" on the computer screen before ever touching the patient's skin eliminates the guess-work of manual techniques. The plan is then programmed into the robotic arm which helps sculpt the bone so that the implants fit perfectly. The result is a robotic partial knee replacement of the damaged joint. So Domo Arigato, Mr Roboto - no more trial and error, no more removal of too much bone, no more blunt saw cuts and no more guess-work.

For the patient, the robotic assistance results in more refined bone resection (to preserve as much native bone as possible), smaller incisions, and a less painful recovery. The optimized positioning promises to ensure more durable results and better function.

Robotics and Experience - a winning combination

Another major factor in determining surgical outcome is after partial knee replacement is surgeon experience. Medical evidence has long shown that the more you do something, the better you get. This is particularly the case for partial knee replacement. In a recent study looking at partial knee replacement it was found that high volume surgeons had a revision rate of less than 1% over 5 years. Surgeons who performed 8-12 partial knee replacements per year had a revision rate of 5% while surgeons who performed less than 8 partial knees/year had a revision rate of 6-8% over 5 years(17). Low volume surgeons had a revision rate 6-8x that of high volume surgeons!! I currently perform over 200 partial knee replacements per year, which is the most of any surgeon in the greater New York area.

Another study demonstrated that there was a direct association between the number of partial knee replacements performed in the hospital and the revision rate. In this study, the greater the surgical volume of partial knee replacements performed, the lower the rate of revision(18). Surgical volume is one reason to choose Hospital for Special Surgery. No hospital in the world performs more joint replacement surgeries than HSS. We are truly experts at what we do. Because Hospital for Special Surgery is devoted exclusively to orthopedics, every one of our scientists, nurses, and therapists is a specialist in this field and aligned to provide the best possible care.

Coupling robotics with extensive surgeon experience in the world-class environment of the Hospital for Special Surgery is a winning combination.

Summary - Why Robotic Partial Knee Replacement

Robotic Partial Knee Replacement is not for everyone and Total Knee Replacement is an excellent solution for many patients. However, in patients with localized arthritic disease, Robotic Partial Knee Replacement offers the following advantages:

  1. Safer procedure than TKR

  2. More rapid return to work and play than TKR

  3. Lower cost to the patient than TKR

  4. Quicker recovery than TKR

  5. Smaller incision and less pain than TKR

  6. More reliable result compared with manual partial knee replacement techniques

The above video was filmed in 2012.
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