As an orthopaedic surgeon and a specialist in joint replacement, I am often asked to give a second opinion on difficult cases. Recently, I had the pleasure to meet a very pleasant 52-year-old gentleman. Mr. N is a carpenter who had a total knee replacement two years ago in another state. After the normal healing process, he continued to have some mild pain and stiffness. He felt that his knee was better than before he had surgery, but wasn't totally happy. It just wasn't up to his activity level and often felt achy and not quite natural. Could I find out what was wrong with it? He asked.
In these cases, orthopaedic surgeons take a systematic approach. They examine the patient, take X-rays and perform a battery of tests to determine the cause of the discomfort. After finishing my evaluation, I presented Mr. N with my findings. His exam, X-rays and tests were all normal -- I had no idea what was wrong with his knee.
There were more than 600,000 knee replacements performed nationwide last year, and the majority are very successful at relieving pain and restoring function in patients with sometimes debilitating arthritis. Doctors know that knee replacement is one of the most effective operations known to medicine, but we also know that not all our patients are happy with them. Data from 2008 (citation included below) shows that up to 20 percent of patients with what seem to be successful knee replacements are unhappy with their result. And this leaves orthopaedic surgeons with a problem: How can we make them better?
Knee replacements are made of metal and plastic and are usually cemented to the patient's bone. They are designed to be as close to the real, normal knee as possible. However, because they are designed for an average knee, they are still just approximations. Artificial knees have to bend like a real knee in everyone -- no matter how big or small their bones may be. So, they come in sizes, just like a pair of shoes. And just like shoes, surgeons have to fit them as best they can. As everyone knows, from struggling with shoes that aren't quite right, the new knees don't always fit perfectly either.
Many investigative surgeons such as myself have wondered, could poor fit be the reason our results aren't quite as good as we think they should be?
There may be an emerging answer to this problem as advancements in personalized medicine emerge -- in orthopedics specifically through -- customized knee replacement. Breakthroughs in computer imaging and 3D printing now allow us to scan a patient's knee, create an accurate model in a computer, and literally print out a new knee. The parts are specific to each patient and follow every curve, surface and groove of their real knee. The computer can compensate for areas of bone that have worn away, and align the new parts to correct deformity, such as bow legs, or knock knees.
This technology has had other, unexpected benefits. Because we do not need hundreds of parts available for every different size knee, the inventory and associated costs are greatly reduced. With custom knees, there are about one-eighth the number of instruments to sterilize and prepare, cutting down both cost and effort for the nursing staff. I was surprised to find out the surgery could be done significantly faster because I could avoid using many of the measurement off-the-shelf knees require to align and size the new knee.
The early data we are collecting shows some promising results. My first 60 patients who received customized knees have needed less pain medication and got their motion back quicker and with less effort than with previous, standard/off-the-shelf knee replacements. Many of them report that their new artificial knee feels similar to their old natural knee, except, of course, without the pain.
Further study is going to be needed to see if there results hold up for years or decades and how much better this technology may be, but it is an exciting time for both me and my patients. I'm very much looking forward to where personalized medicine will take us. In the future, we may be able to make more accurate hip replacements, shoulder replacements and even smaller joints like the elbow and ankle. Like all orthopaedic surgeons, I am always trying to find new ways to help my patients with their arthritic pain and to see less patients like Mr. N, who aren't totally happy with their surgery.
Citation:
"Estimates of the Prevalence of Arthritis and Other Rheumatic Conditions in the United States." Authors: Reva C. Lawrence, David T. Felson, Charles G. Helmick, Lesley M. Arnold, Hyon Choi, Richard A. Deyo, Sherine Gabriel, Rosemarie Hirsch, Marc C. Hochberg, Gene G. Hunder, Joanne M. Jordan, Jeffrey N. Katz, Hilal Maradit Kremers, and Frederick Wolfe, for the National Arthritis Data Workgroup. ARTHRITIS & RHEUMATISM. Vol. 58, No. 1, January 2008, pp 26-35. DOI 10.1002/art.23176. 2008, American College of Rheumatology