Ask Dr Woods

Electromagnetic Navigation is Here

2005-09-30T18:17:00.000-07:00

Boston--The Harvard Advances in Arthroplasty (hip and knee replacement) course has been excellent. Honestly a little grueling. The first almost two days covered total hip replacement. This included 82 lectures and two satellite video cast live surgeries. The total knee replacement portion of the meeting started late yesterday with five lectures. Knee replacement lectures resumed this morning and continued throughout the day with thirty six more lectures and two satellite video cast live surgeries. The course ends tomorrow with eleven lectures and one satellite video cast live surgery. My mind and other parts of my anatomy are a little numb this evening as I write this.

As to new computer navigation...the rumors were true. Medtronics in conjunction with Zimmer Corporation has been working with a prototype electromagnetic navigation system since February 2005 and introduced it to a few centers in June 2005. It is now available for general use. I just got back from an evening demonstration of the system. From everything I saw this evening, this system is where I had hoped it would be. I have been looking for a system that would confirm precise bone cuts without the complexity of an optical system. The 'trackers' are much, much smaller, and fit inside the skin incisions even on a minimally invasive knee patient. This eliminates the need for large pins to be drilled into the bone either through separate incisions or through much longer incisions in the skin and muscles. The 'sensor' that reads the measurements being sent from the trackers is a small hand held device that can be put in a sterile bag and kept right on the operative field. No more need for large 'line of sight optical cameras that have to be constantly adjusted by the un-scrubbed staff. The resulting measurements are going to allow very precise cuts in the bones, allowing perfect placement of the components. The instruments we have now are very good, but this new technology will eliminate any outliers even in very difficult knees.

The pictures here show the new trackers and instruments for reading the orientation of the tools we use for making the bone cuts. The first picture above show one of the electromagnetic trackers attached to a model bone of the tibia, the lower leg bone. The second wire seen in the picture runs to the second tracker attached to the thigh bone or femur.

The second picture shows an electromagnetic tracker that is attached to a flat blunt blade that is sticking into the cutting slot of the tibial cutting jig. Through every elegant computer modeling, the combination of the three trackers tells the surgeon on a computer screen exactly where his instruments are relative to a computer generated model of the knee he is working on. The computer also gives out exact measurements as to how thick and in what plane the proposed cuts are.

This is just one more significant advancement that will help us as surgeons give our patients the very best in care ensuring a longer lasting joint replacement.

A Great Course in Bean Town

2005-09-27T15:42:00.000-07:00

I just flew into Bean Town--Boston, for a three and a half day intensive Harvard Medical School course on Advances in Arthroplasty. The subtitle of the course is A Major Focus on Navigation, Bearing Surfaces, and MIS Techniques. This is the 35th Annual Course on the latest and greatest new information on hip and knee replacement surgery. I am returning after being at the course for the first time last year. Just couldn't absorb enough last year! Lectures start each morning at 7:00 a.m. (read 4:00 a.m. on my biologic clock) and run through the day until 5:00 p.m. every night. The material is excellent. There are 76 lecturers each trying to get their 'best stuff' packed into a ten to fifteen minute lecture. I am looking forward to a very stimulating three and a half days of learning by day, and one of my favorite bookstores (The Coop at Harvard Square) by night. I will try and post some of the best here on the blog over the next couple of days.

In my post "Dine Out..." Standing Room Only I mentioned that I was waiting to see the next generation of computer navigation, one that uses electromagnetic fields instead of bulkier and more invasive infrared tracking probes. Rumor has it, that the prototypes may be demonstrated here at the meeting. Stay tuned.

Never too old

2005-09-26T23:32:00.000-07:00

Last week I had the privilege of treating an old patient of mine. Bill came to see me three years ago when his right hip was keeping him from enjoying life. Bill was 90 at the time I performed his hip replacement.

When his left knee had become so arthritic that he couldn't get along well, he showed up again with his wife of 70 years and his daughter. He wanted a knee that worked as well as his hip. Last week I replaced Bill's knee using a quad-sparing minimally invasive total knee replacement.

At three days post-op Bill had a range of motion of 5 to 110 degrees and was walking a good 200 feet briskly with his walker. At five days post-op Bill has a range of motion of 5-117 degrees of motion. He has been doing straight leg raises since he got to the recovery room.

Here is a picture of Bill five days after surgery with his sweet wife Marjorie. I don't know what Bill has been eating all these years, but I am going to find out!

"Dine Out..." Standing Room Only

2005-09-09T21:48:00.000-07:00

Either the offer of a free meal was just too much to pass up, or there is a great deal of interest in minimally invasive total knee surgery! As I mentioned in the post Dine Out and hear about Minimally Invasive Knee Surgery, French Hospital Medical Center invited seniors from the central coast of California in for a free meal and a lecture on "A Minimally-Invasive Knee Replacement.' Places were set for 115 guests. The response was overwhelming, with all 115 seats taken and 20 more people sent to the cafeteria to sit and eat their meal before the lecture started.

I presented a PowerPoint lecture explaining what osteoarthritis is and how minimally invasive knee surgery differs from traditional total knee replacement. The lecture ended with case presentations of three typical patients, followed by questions and answers up at the podium.

Some of the representative questions went something like this:

Does my insurance cover this procedure? The answer: Yes, all insurances including Medicare cover MIS knee surgery as the end result is the same, a total knee replacement. The difference is less pain and a faster recovery due to the pain management and anesthetic techniques and the much less invasive incision and trauma to the muscles and tendons.
I have had a knee replacement surgery and am having problems with the knee. Can a revision knee replacement be done through minimally invasive techniques?
Answer: Unfortunately no. A revision knee replacement may require taking all the components and cement out of the knee, a task that requires a much larger exposure.
Do you use computer navigation to put the components in?
Answer: Not usually. I have used computer navigation on five or six knee replacements. I have found that for a standard arthritic knee - that is, one without severe angular deformities or severe bone deficiencies (where MIS is contraindicated) - computer navigation did not change the alignment that I had obtained using the instruments designed for the implants. Computer navigation also increases the cost of the procedure, which isn't warranted if alignment can be accurately obtained with the current instruments. In addition, the computer navigation just lengthened the operating time - and thus time under anesthesia. Since increased operating time increases the risk of infection, I don't prefer today's computer navigation.

However, I believe that when navigation systems improve to the point where positioning can be checked non-invasively with electromagnetic frequency, it will reduce operating time and may be more attactive as a way to confirm alignment.

My thanks to French Hospital for the invitation to share information on this new technique.

Can badly deformed hips be replaced with MIS?

2005-09-04T22:14:00.000-07:00

I received the following question regarding minimally invasive hip replacement surgery:

Hi, I am 31 years old and have multiple epiphyseal displaysia and my right hip is really bad now (chronic pain, frequent locking up, etc.) Is your MIS procedure something that would be available to me or is it more for lesser severity hip arthritis? Also, I have been told in the past that the first hip lasts 20 years, the second lasts 10 years and that there is no third one. At this point, barring further advances in the procedure, this would put me in a wheelchair by time I'm 61. Is this still the case or is there more hope for me now? I would love to put this destroyed hip behind me and get a replacement, but am worried about the risk of not being able to walk when I'm 60.

I offered the following response:

In all likelihood you would be a candidate for MIS surgery, provided there is not significant deformity to the acetabulum or socket of your hip. Hips are lasting longer and longer with some of the newer materials that we are using. Will these materials last longer than 20 years? Hip simulators seem to indicate that they will, but it goes without saying that we haven’t been using these materials in humans long enough to know whether they will last longer in human hip joints. The studies on the newer plastics and ceramic materials done in simulators indicate that they have excellent wear characteristics. It is the wear particles that are responsible for the failure of these artificial joints, so if there are fewer wear particles, they should last longer.

As to your second question, this brings up a good point. It is bone loss that limits how many times a joint can be re-operated on. This is the reason that it is so important to do regular post-operative x-rays every year or two. Comparing the x-rays with the x-rays taken immediately post-op and in subsequent years can reveal early bone loss due to wear particles. If the lining surfaces are replaced before the cup shell or the thigh stem become loose, the second or third hip may last as long as the first.

Dine Out and hear about Minimally Invasive Knee Surgery

2005-09-03T16:54:00.000-07:00

I will be giving an update on minimally invasive knee replacement surgery at French Hospital Medical Center on Thursday, September 8, 2005. French Hospital invites the Seniors to 'Dine Out for your Health' on the second Thursday of each month. Seniors are invited to join them for a free dinner from 5:00-7:00 p.m. in the French Hospital Medical Center Auditorium while listening to a health related lecture. This invitation is open to all seniors 55 years of age and older.

During the complimentary meal, I will be giving a powerpoint presentation introducing the 'Minimally Invasive Quad-sparing Total Knee Replacement' procedure. The lecture will focus on the differences between MIS knee replacement surgery and traditional total knee replacement surgery. Case examples of my patients that have undergone this procedure will be presented as well.

If you live in the area, and want to learn more about newer techniques that cut down the post-operative pain and markedly decrease post-operative rehab, please join us for dinner this coming Thursday evening.

When Should I have this hip replaced?

2005-08-30T20:24:00.000-07:00

I received an email today with a very commonly asked question. A gentleman sent me the following:

Dear sir: I was told 4 days ago that I was going to need a new hip in about a year from now. knowing that it won't get any better, should I have the operation now rather than latter. I can still get around ok but limp a little. my biggest problem is sleeping,just cant get comfortable. Your help will be appreciated, thank-you

The decision as to when to proceed with a hip or for that matter a knee replacement is not made based on any single factor. We as surgeons don't recommend replacement surgery based, for example, solely on a review of a set of x-rays that show significant or total joint space loss. Nor should the decision be based on restricted activities, or pain alone. Rather, the decision to proceed with joint replacement is based on a review of the patient's activity restrictions, response to conservative treatment, a physical exam and radiograph review.

In young patients (patients under the age of 60), there may be other procedures that can prolong the life of the joint prior to replacement surgery. This is particularly true of the knee.

In the past the frequently heard recommendation to the above question went something like this. "When you can no longer walk, come back in and we will replace your hip." Unfortunately this led to patients becoming significantly debilitated prior to surgery. As a result, they were not able to enjoy the new joint replacement to its fullest, and led a miserable existence up until their joint replacement. Assuming x-rays show considerable joint destruction, current recommendations are to consider the joint replacement when you can no longer participate in the activities that you enjoy despite arthritic medications, supplements and good conditioning.

If life is miserable due to an arthritic hip or knee, there really isn't much to be gained by trying to put off surgery for a year.

Less is sometimes more

2005-08-23T23:57:00.000-07:00

Every so often a good article comes along that needs to be shared. Forbes.com just posted an article provided by HealthDay news. It's entitled "Joint Replacement: Less is Sometimes More." This article does a good job defining the currently accepted terms for the various joint replacement options available. Conventional replacement is just that, the way things have been done for years. For a knee replacement, this means a 10-12 inch incision with division of the quadriceps or thigh muscle tendon. The article, quoting Dr. Jay Mabrey of Baylor University Medical Center in Dallas, describes the differences between 'less invasive' and 'minimally invasive' replacements.

Dr. Mabrey also highlights an important partner to the smaller incisions and less muscle trauma of the minimally invasive techniques: newer anesthesia techniques that allow patients to get out of the hospital 24-36 hours after surgery.

Just yesterday I replaced the left knee of a 75 year old gentleman using a minimally invasive technique. Despite being the second joint replacement patient of the day, he was up that afternoon (the day of surgery). The physical therapist reported an immediate range of motion of 4-105 degrees and took him on a 90 foot walk down the length of the hospital corridor. He was effectively functioning at the same level as a patient would on post-op day three following a conventional total knee replacement. I am convinced that this phenomenal progress is related both to the minimal tissue trauma to the thigh muscles as well as to the pre-op, intra-op and post-op pain management techniques. And the bottom line is a much happier, more comfortable, and faster-recovering patient.

Can't you just give me some new cartilage?

2005-08-20T08:11:00.000-07:00

Faced with arthritis of the knee, many of my patients have asked me, “Isn’t there a way that you could slip something in to replace the cartilage that’s gone?” Some use the term “Squirt,” as in “Squirt something into my knee.”

Since it’s the worn-out cartilage that leads to bone-on-bone pain (and sometimes bone spurs), this is a really attractive idea. And, yes, a procedure very similar to this has been developed and tried over the last five to six years.  It is called UniSpacer Arthroplasty, and was designed to be used in patients who had just one side of their knee worn out. In this surgery, the UniSpacer, a tiny metallic disc, is simply inserted between the worn parts of the knee through a small incision, with no bone removal and no cementing of the implant in the knee. The hope was that this simple procedure would restore stability and alignment of arthritic knees while providing sustained pain relief – all without trauma to the surrounding bone or soft tissue.

Well, I’m sorry, but I have some bad news. Just yesterday I received this month’s Journal of Bone & Joint Surgery (the peer-reviewed ‘Official Scientific Publication of the American Academy of Orthopedic Surgeons’).  It contained an article titled “UniSpacer Arthoplasty of the Knee” (see abstract).  The jury is in. The UniSpacer DOES NOT work. The study was performed at the Los Angeles Orthopaedic Institute in Sherman Oaks, California by Drs. Domenick Sisto and Isaac Mitchell. From April 2002 through November 2002, thirty-seven UniSpacer Arthroplasties (joint surgeries) were performed. There were no excellent, ten good, fifteen fair and twelve poor results. Six of the twelve poor results were in knees that had a dislocation of the UniSpacer (it ‘squirted' out from between the bones.) All twelve poor results were converted to a total knee arthroplasty.  The authors concluded that on the basis of their experience, they could not recommend the UniSpacer arthroplasty for the treatment of arthritis in one side of the knee joint.

I agree with their negative recommendation. This study and others have shown that UniSpacer Arthroplasties have resulted in negative outcomes in too high a percentage of cases for me to recommend this surgery to my patients.

My recommendation instead is for Unicompartmental Arthroplasty. Patients who have only one-sided arthritis to their knees have done very well with this minimally invasive procedure, where new metal surfaces are cemented onto the worn side of the knee joint, and a highly specialized plastic is fixed into the lower component. I perform this surgery frequently, and have always had good results. More importantly, other orthopedic surgeons have matched my positive experience with Unicompartmental Arthroplasty and have reported their experiences in peer-reviewed literature.

For more information on this procedure visit my website at http://www.centralcoastmis.com/MISKnee.htm.  To read a patient story on Unicompartmental Arthroplasty, read Bob’s story at http://www.centralcoastmis.com/PatientStories.htm#Bob.

For those whose knees or hips hurt

2005-08-18T10:28:00.000-07:00

If your knees or hips hurt, you'll probably find this Blog helpful. I'll be posting articles to help you understand what's going on when your knees or hips become painful, and when arthritis takes away your mobility. I'll discuss some non-surgical steps you can take to reduce your discomfort and buy some time before surgical intervention is required. I'll clarify what's involved in a knee or hip replacement. I'll discuss new techniques for knee and hip surgeries. I'll share some patients' stories so you can get an idea of what they've experienced. And I'll answer your questions. Just email me using the link on this Blog.
I also have a website dedicated to making this kind of information available in a well-organized way. It's at www.CentralCoastMIS.com, and I invite you to visit it at any time.