Knee And Hip Replacement

By Dr. Cass Nakasone
Interviewed by Melissa Moniz
Wednesday - November 26, 2008
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Dr. Cass Nakasone

Orthopedic Surgeon, Chief of Staff of the Department of Orthopedics at Straub

Interviewed by Melissa Moniz

Where did you receive your schooling and training?

I graduated from Punahou, then began a five year combined physics/engineering program with Whitman College and the California Institute of Technology. I spent three years at Whitman and received my physics/mathematics degree, then transferred to the California Institute of Technology and earned my engineering degree. Following that, I went to Stanford University where I earned my Master of Science degree in mechanical engineering.

At that time, I had no plans of going into medicine at all. But I was working with some doctors at Stanford who were also engineers, and during a research project one of those doctors made a very casual comment like, ‘Hey, you should think about going into medicine because of your background.’ Then right after my master’s degree, I applied for medical school. To be honest, it was a poorly thought-out decision and I had no idea what it took to be a doctor! Luckily, I was accepted at the University of Hawaii medical school.


I had no idea what area of medicine I wanted to pursue. But I guess because of my engineering background, orthopedics just seemed to call to me. I did my orthopedic residency program at the University of Hawaii and then after that I went to the University of Southern California, where I did my specialty training in joint replacement surgery with Dr. Kelly Vince, who was my mentor. It was during my fellowship that I was exposed to these different techniques. I also had the good fortune of being introduced to Dr. Joel Matta, who taught me this minimally invasive anterior hip replacement approach. Dr. Vince is considered one of the world’s leading experts on total knee replacement and complex revision total knee replacements. Dr. Matta is considered the pioneer of the minimally invasive anterior hip approach and is also a world leader regarding complex pelvic and hip fractures. I consider myself to be extremely fortunate to have been exposed to and trained by surgeons of this caliber.

What is your area of specialty?

My area of specialty is hip and knee replacement through a minimally invasive or traditional approach as treatment for arthritis. And that’s all I do. I really have sub-specialized my practice. I would say 98 percent of my practice is related to hip or knee surgery related to arthritis or complex cases related to that. For example, people who have had a hip or knee replacement in the past and have had complications or need a revision surgery.

Dr. Nakasone examines patient Ellen Fujihara during her two-week status post left total hip arthroplasty

How much of your practice is doing hip replacement surgery and how much of it is doing knee replacement surgery?

In Hawaii, generally speaking, it’s about four knee replacements to every one hip replacement. The reason for that is the population. There’s a higher rate of knee arthritis in Asians and Polynesians, as opposed to hip arthritis, which is more common in Caucasians. So on the Mainland, the rate of hip and knee replacements is about one to one.

At what point does a patient need to do the surgery?

The answer to that is very simple. No one needs to have surgery. Arthritis is not a life-threatening condition and there is no urgency to do surgery. Joint replacement surgery is a choice. Patients choose to have surgery if the pain due to the arthritis cannot be alleviated with non-surgical methods and is no longer tolerable or has made the quality of their life unacceptable. The use of anti-inflammatory medication, injectable therapies like cortisone, exercise, activity modification and weight reduction are some of the non-surgical methods of dealing with the pain from arthritis. When all of these attempts repeatedly fail, then surgery should be considered. Thankfully, hip and knee replacement surgeries are very successful in eliminating pain and restoring function.

Do most patients need to do rehabilitation after the surgery?

There are different opinions on that, but my opinion is that rehabilitation, especially for knee replacements, is probably as important as the surgery itself. And an excellent physical therapist can have a huge impact on the functional outcome.

Dr. Nakasone with patient Jeanette Ness, who came in for her one-year status post right hip arthroplasty exam

You mentioned earlier the minimally invasive anterior hip approach. Can you talk about that procedure?

The difference between the minimally invasive surgery and the standard or traditional way of doing the surgery is in the way in which the implants are put in. The “traditional” incision for a hip replacement is about 8-12 inches long and most orthopedic surgeons are trained with this technique. When I was at my fellowship I was fortunate enough to be trained in several techniques. The “traditional” technique and also the minimally invasive posterior approach, as well as the minimally invasive anterior approach as mentioned above. Although the minimally invasive posterior approach has a much smaller incision, I still have to cut four or five muscles around the hip joint in order to do the hip replacement, the same as for a “traditional” approach.

These muscles are very important muscles that help keep the hip in place. So even though I make a smaller incision, the patient still has to observe hip precautions for three or four months (and more safely for the rest of their life) because they have to heal the muscles that were cut, and once cut, these muscles or ten-dons never return to normal strength. Because of this, the rate of dislocation following a hip replacement surgery using the “traditional” approach within three to four months ranges anywhere from 0 to 20 percent. Then I was exposed to this minimally invasive anterior hip approach, where the incision length is, generally speaking, about four inches. But the length of the incision is not what’s important. What’s important is that I can put in the same hip implant without having to cut or repair any muscles. The surgery uses spaces between the muscle groups. And because the muscles aren’t cut, the patients don’t have any hip precautions after the surgery. And in the approximately 200 to 300 hip replacements I’ve done so far, despite having no hip precautions, none of my patients has had hip dislocations after a primary hip replacement.

In general, is a hip or knee replacement surgery more difficult to perform?

It really depends on the patient. But knee replacements in general are more difficult to make people totally happy with because the knee is such a complex joint. The knee replacement that we have is so amazing, but it’s nowhere near what your knee was like when you were 20 years old. So what I tell people is I can be about 95 to 98 percent confident that I can make their knee 90 to 95 percent better, but I cannot give them a 20-year-old knee or make it perfect. From a mechanical and anatomical standpoint, it’s a little more difficult to get that perfect.

Generally speaking, what are the most common concerns patients have when considering the surgery?

I think patients want to know how long they will be dependent on others for help. I think mostly it’s just the worry of the recovery and what the pain is going to be like. Most people want to know how long they will take to recover. And those are very difficult questions to answer, especially about pain and recovery, because again, a lot of it has to do with the patient. People have very different coping skills, pain tolerance, functional skills, coordination, strength and mental toughness. Also, satisfaction and happiness are truly matters of personal perception. Interestingly enough, I don’t think people pay enough attention to the discussion of surgical risks and complications.

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