Henrik Malchau, M.D., Ph.D., is an Associate Professor in the Department of Orthopedics at the University of Göteborg in Sweden. Dr. Malchau is also Project Leader at the Joint Replacement Unit (JRU) at Sahlgrenska University Hospital, where he runs the Swedish National Hip Arthroplasty Register. The Register is a collection of data on all primary total hip replacements and hip implant revisions performed in Sweden since 1979.
MedTech1: Who undergoes total hip replacement (THR) surgery?
Dr. Malchau: Joint replacements are recommended for everybody with a degenerative hip disease. I would guess that 80 percent of hip replacement operations are performed due to this condition, called osteoarthritis. Some patients with inflammatory hip cases, such as rheumatoid arthritis, will also need THR. Finally, there is an increasing number of patients getting joint replacement due to hip fractures and especially femoral neck fractures.
MedTech1: Is that a new indication?
Dr. Malchau: It’s not new, but the fraction of the population age 80 and above steadily increases. A lot of these individuals face a hip fracture, and it seems like the best treatment for fracture is just replacing the femoral head. But more and more are in need of THR instead.
MedTech1: Do athletes account for the greatest percentage of people requiring total knee replacement surgery?
Dr. Malchau: No, athletes are a minor fraction. Degenerative joint disease is probably connected, for most of the patients, to an increase in age. Just as the skin wrinkles when you get older, the cartilage in the joints ages as well. That is what causes the need for this operation.
MedTech1: How long have you worked in orthopedics?
Dr. Malchau: A long time now. Twenty years.
MedTech1: Have you noticed an improvement in the quality of artificial joints used in replacement surgery?
Dr. Malchau: I have been heavily involved in running the Register in Sweden, documenting all failures after THR. We have information on approximately 200,000 primary procedures and 15,000 revision procedures since the Register started in 1979. If you look at those patients who got their hip replacement in 1979, then look 10 years down the line, 11 or 12 percent of those would have been through a revision. And today, when taking the cohort operated on in 1990, it is only 4 percent. That is one way of documenting a definite improvement in the outcome of the procedure.
MedTech1: Have you been involved in the design of joint replacement prostheses?
Dr. Malchau: Running the Register is to be unbiased, so for that reason I have not been involved in design. I will probably have to stay out of that business until I quit the Register to avoid having double interests.
MedTech1: Is the Register comprised of people from the United States, Europe, or both?
Dr. Malchau: Only Sweden. The Register is everyone operated on in Sweden, so it covers more than 96 percent of the population of total hip operations in Sweden.
MedTech1: Some people with osteoarthritis of the hip or knee are hesitant to have joint replacement surgery. What would you say to those people?
Dr. Malchau: I would show them the results. I get emails from patients, even patients from the States, and I tell them to go to the Register’s home page and look up the results themselves. There are risk groups. Patients younger than 50 years have a higher risk than the average patient. The average age for this procedure is 70 years. The younger you are or the more active you are, the higher the risk is for complications because you use your joint more. It’s like a car. The more miles you put on a car, the higher risk there is that something is going to break down. The weak link in artificial joints has been the articulating mechanism and the materials that have been used for the cup.
MedTech1: Are most people pleased with the procedure?
Dr. Malchau: My guess is between 1 million and 1.3 million people annually worldwide are getting this operation, 200,000 just in the States per year. For the majority of the patients, THR is working just beautifully.
But it can still be improved. That’s what I’m working on research-wise. There is a lot of focus on the articulating mechanism. Now there is a new, exciting way to treat the polyethylene used in the cup to make it much more wear-resistant. That’s one of the promising things. Implant design and surgical technique can also be improved.
For more information on Dr. Malchau's research, visit the Register's Home Page.