CCMIS Frequently Asked Questions About MIS

Minimally invasive surgery to the hip and knee is a new, comprehensive approach to replacement of worn joints that is much more than simply a smaller skin incision. Not all surgeons have been trained to use the specialized instruments required to reliably and safely replace joints through smaller incisions with minimal disruption to the surrounding tissues. Zimmer Corporation, the makers of the implants that Dr. Woods uses in knee and hip replacements, is a leader in the field of minimally invasive surgery, having pioneered many of the techniques for MIS total hip surgery, as well as the Quad sparing MIS total knee surgery. Zimmer Corporation requires that surgeons attend the Zimmer Institute before they give surgeons access to these specialized instruments. The Institute graduates are highly encouraged to go and visit surgeons that have already demonstrated proficiency in using the instruments and the implants. Dr. Woods has attended the Zimmer Institute in Quad Sparing Total Knee replacement and traveled to visit and scrub in with two of the pioneers in this technique including the inventor of the instrumentation. Dr. Woods has been performing MIS total hip replacements for the last two years since scrubbing in with one of the innovators in MIS total hip replacement surgery.

Is the minimally invasive surgery procedure covered by insurance?

Yes, insurance companies do not distinguish between MIS total hip and knee surgeries and standard procedures that have been covered for years. Authorization from your insurance company will be obtained by Dr. Woods’ staff prior to your pre-operative appointment.

When do I have to take antibiotics after my joint replacement?

Bacteria can be introduced into the blood stream and travel to the prosthetic component with all dental procedures and any other gastrointestinal or genitourinary procedure. Infections of the skin, throat or gastrointestinal track can get into the blood stream and travel to the joint causing infection. For this reason, it is recommended that prophylactic (protective) antibiotics be taken prior to any dental procedure or procedure of the gastrointestinal or genitourinary tract.

What can I do prior to my surgery to improve my outcome?

Strengthening
Anti-oxidants / vitamins
Discontinue blood thinners

When can I stop taking the pain medications?

Minimally invasive surgery is a comprehensive program to not only put the same tried and true prosthetic components in to replace the worn surfaces of the hip and knee, but also includes a well designed program of pre-operative pain medications, intra-operative medications and post-operative pain management. The result is that many patients have very little pain in the first 24 hours of surgery (typically 0-3 on an analogue pain scale of 1-10). The pain thereafter is usually tolerable with Vicodin, Norco or a similar strength pain medication. Many patients move on to Tylenol or ibuprofen shortly after going home and may take something stronger only prior to therapy.

When can I shower after surgery?

Dr. Woods uses a ‘plastic surgery’ closure of both the MIS total knee and MIS total hip replacement wounds. This is essentially a single running stitch of dissolvable suture material that is woven from side to side down the length of the 2 ¾ to 5 inch hip incision or the 4 to 6 inch knee incision. This is in turn covered with a plastic paint-on dressing called Dermabond. There are no sutures to take out or that would allow infection to get under the skin. In addition to the skin incision there are two small 1/8 inch puncture wounds from the drains that need to seal. This usually occurs by the third to fourth post-operative day. Patients can then get the wound wet in the shower without any covering. Bathing or sitting in a Jacuzzi is not recommended for 10 days.

Should I have a special diet after surgery?

No special diets are necessary. If you are on Coumadin, a blood thinner to prevent clots after surgery, there are certain food items that should be avoided that may alter the blood levels of the Coumadin.
(see How do you prevent clots in the legs following surgery?)

MIS Knee Questions

What is the difference between minimally invasive knee replacement and traditional knee replacement?

In traditional knee replacement, an approximately 10 to 12 inch skin incision is made centered over the knee. This is followed by making an incision into the quadriceps tendon above the knee, down the side of the kneecap and two inches below the joint and then the kneecap is flipped 180 degrees and off to the side (everted). The knee is then bent up to expose the bones of the knee for resurfacing with the knee prosthesis.

In the Mini-Incision and Quad Sparing incision total knee replacements, the incision is 4-6 inches. The quadriceps tendon is not cut, nor is the kneecap flipped backwards. In the mini-incision total knee replacement (the larger of the two MIS total knee techniques), a small incision of about 1 inch is made into the muscle fibers of the vastus medialis muscle--one of the four quadriceps muscles, leaving the quadriceps tendon intact. The quad sparing total knee replacement leaves all of the quadriceps muscles intact including the vastus medialis. Both techniques result in a marked decrease in muscle and tendon damage, which in turn does not weaken the quadriceps muscle and allows a much quicker return to normal activity.

Is there a difference between the replacement knee prosthesis used in minimally invasive surgery and the one used in traditional surgery?

No, the prosthesis is the same. Dr. Woods uses the Zimmer Corporation’s NexGen Flex prosthetic components. This prosthesis has a long track record in the United States and abroad. Zimmer does have a prototype tibial component (the leg bone side of the joint) which comes in two pieces to make it easier to put in through the smaller incision.

Will the knee replaced with minimally invasive surgery last as long as one replaced through traditional surgery?

Since the prosthesis is the same one as used in the traditional knee replacement surgery, there should be no difference in how long the prosthesis lasts - provided it is put in by an experienced knee surgeon using the same tried and proven techniques of proper sizing and positioning, as well as ligament balance.

How does Dr. Woods put a new knee prosthesis through such a small incision?

The mini-incision and Quad Sparing total knee replacement surgery is performed with specialized instruments which allow Dr. Woods and his assistant to move the smaller incision ‘window’ around the knee joint to give access to the areas he is working on. These specialized instruments include custom retractors for holding tissue out of the way, a knee holder to allow infinite different angles of flexion, extension and rotation of the knee joint, and new cutting jigs that allow cuts to be made from the side of the knee where the incision is rather than from the front of the knee.

How would I benefit from the minimally invasive knee replacement?

Studies have shown that using the quadriceps-sparing MIS knee replacement technique allows patients to recover three times faster, have about one-third less pain, one-third the length of hospital stay, 30 percent less blood loss and 10 degrees more motion of the knee at the end of the first and second years after the surgery, than those who underwent the traditional knee replacement procedure.

What are the risks of the procedure?

The risks of the procedure are the same as with traditional knee replacement surgery. These include infection, blood loss requiring transfusion, stiffness to the knee, prosthetic component loosening, and misalignment. Studies have shown 30% less blood loss with the quadriceps-sparing MIS knee replacement as well as 10 degrees more motion of the knee at the end of the first and second years after the surgery.

Who is a candidate for MIS knee replacement surgery?

Not everyone is a candidate for the MIS Quad Sparing total knee procedure. The procedure is not possible in very over weight individuals, very heavily muscled individuals, patients with very significant ‘knock knees’, or ‘bow legs’ or in patients with significant contractures of their knees. Most patients are candidates for the mini-incision total knee procedure which does involve cutting a small portion of one of the quadriceps muscles. Other patients that may not be candidates include those with significant prior open knee surgery (not arthroscopic procedures) or patients that have hardware fixed to the bones just above or below their knee from prior injuries.

When can I drive?

This will depend on whether you drive an automatic transmission or a manual transmission and whether it is your left or right knee that was replaced. Provided you have an automatic transmission and it was your left knee that was replaced you can drive short distances as soon as you are no longer on narcotic pain medication. This could be as early as a week after surgery. If you had the right knee replaced or you have a manual transmission, you should be able to drive short distances when you can control your knee movement without significant discomfort. This could be as early as three weeks after surgery.

When can I get back to full activity?

Full return to activity will depend on several factors. These include your overall physical condition and the condition of your knee prior to the surgery. If you have maintained good strength to muscles of your thigh and leg as well as adequate cardiovascular conditioning, you should be back to a walking program as early as two weeks after surgery. Near full motion to the knee should be back by six weeks after surgery, although many patients have had the majority of their motion back by two weeks. Patients who have had MIS total knee replacement generally rehab about three times faster than patients who have had traditional knee replacement.

MIS Hip Questions

What is the difference between minimally invasive hip replacement and traditional hip replacement?

The difference is in the size of the skin incision and, more importantly, how much muscle and tissue is cut to put the total joint components in. Cutting less muscle results in less pain, less swelling and potentially a quicker recovery.

Is there a difference between the replacement hip prosthesis used in minimally invasive surgery and the one used in traditional surgery?

No, the same components are used in MIS hip replacement surgery that are used in traditional surgery. They are just put in through smaller incisions in the skin and muscle using specialized instruments. The components have a long track record of excellent performance.

How does Dr. Woods put in a new hip prosthesis through such small incisions?

By using specialized instruments and moving the ‘skin window’ of tissue around, the components are able to be installed in the same precise alignment that is required for a stable, long lasting hip.

How would I benefit from minimally invasive hip replacement?

This is a new procedure, and there isn't a lot of peer-reviewed scientific literature yet comparing results of minimally invasive hip replacements with traditional hip replacements. The existing scientific literature is mixed on whether minimally invasive hip surgery offers significant long-term benefit over traditional hip surgery. However, our experience and that of other MIS pioneers has shown that with less tissue damage, coupled with pre-operative medication, intraoperative nerve blocking techniques and early mobilization, there is less pain, a shorter hospital stay and earlier return to usual activities.

What is the average age of someone who undergoes minimally invasive hip replacement?

MIS techniques can be used on all patients, from patients in their 40’s who have post-traumatic arthritis, to those in their 70s and 80s who are suffering from osteoarthritis.

What types of prosthesis are used in minimally invasive hip replacements?

Dr. Woods uses Zimmer corporation’s prosthetic components, generally selecting the VerSys Hip System.

Typically for patient’s who are in their 40s to early 70s, uncemented components are used for both the femoral (thigh bone) side of the joint as well as on the acetabular (pelvic socket side) of the joint. For patients in their late seventies to eighties, the femoral (thigh bone) side of the joint is cemented into the thigh bone whereas the acetabular component is inserted without cement.

Both of the components are made of a high grade medical alloy called cobalt-chrome. The components used in an uncemented case have titanium alloy pads into which the patients bone grows to hold them.

How long do I need to maintain the hip replacement cautions?

Hip precautions refer to the limitations recommended following a hip replacement. These prevent the hip joint from dislocating (the ball coming out of the socket) prior to the soft tissue healing and strengthening. The precautions are recommended for a period of four months. They include preclusion from crossing one’s legs, bending well beyond 90 degrees at the waist, or bending and contorting the hip to tie one’s shoes. Once the soft tissues have healed sufficiently, these precautions can be dropped.

Will my insurance cover the minimally invasive hip replacement?

Yes, all insurances, including Medicare, pay for MIS total hip surgery. There is no difference in the surgical code used to bill for the MIS total hip surgery. It is the same as for a traditional hip replacement.

When can I get back to full activity after my minimally invasive hip replacement?

Patients, with a few exceptions, are able to start putting full weight on the operative side the same day as surgery. Typically, patients are walking 100-200 feet by the second day after surgery. A walker or crutches are recommended until patients feel confident enough and are stable enough to go to a cane - typically at one to two weeks after surgery. Many of the younger or more fit patients are walking up to a mile without a cane or crutch by six weeks after surgery. At four months after surgery, a full golf swing is possible.

How long will I be in the hospital for my minimally invasive hip replacement?

This will depend on your age and level of fitness prior to the surgery. If you have a spouse at home that can help with meals and household activities, it may be possible to go home as early as two or three days after surgery.

If patients are older and live alone, a short stay in the Transitional Care Facility, a step-down hospital, may be appropriate for a period of seven to ten days prior to going home.