This week I was immersed in a variety of activities, and was able to further define my research project to be completed over the next few weeks.
The biggest long term problem with knee implants, and all arthroplasties for that matter, is wear of the material over time, due to the cyclic loading over years and years. With the improvement of materials, such as cross-linked ultra high molecular weight polyethylene (CL UHMWPE), the wears of implants has been reduced significantly, but still occurs. When metal debris and other debris appears in the joint, inflammation and other reactions can occur, even at concentrations as low as parts per billion.
My project for the summer will be comparing the wear and tear of two different types of knee implants: one that has a "mobile bearing" surface, and another that is identical in every way except without the mobile bearing part. These implants have already been retrieved from patients. I will be working with a med student to examine each implant on two surfaces, each surface divided into ten regions, to determine the type and severity of wear. Seven different wear categories will be examined, including burnishing, scratching, and abrasion. This week I learned how the implants are to be graded, and was given some reading material on the background of this grading system, and how it has been used previously.
Also this week, I attended a fracture clinic with Dr. Lane. For 6 hours, I shadowed him and some of his residents as they followed up with patients who previously had fractures usually due to osteopenia or osteoporosis. In my research at Cornell, I work with Dr. van der Meulen, who is interested in bone fractures, osteoporosis, and bone properties at the nano, micro, and whole bone level. Seeing patients who have dealt with these issues was a great supplement to my graduate work. I learned about the clinical side. One thing that was interesting to me was to learn the normal levels of nutrients important to bone: Ca should be at a level of 9-10, and vitamin D should be over 32. During the clinic, I saw patients who had calcium levels below 8 and vitamin D levels below 20! Another very interesting aspect of the day was to learn about all the drugs used to treat osteoporosis. Osteoporosis is a turnover disease. Constantly, bone is being formed and resorbed at rates dependent on a number of factors, including age, activity level, genetics, hormone levels, and nutrition. When this is imbalanced, bone can be lost. Many of the osteoporotic drugs used aim to decrease the bone turnover, thereby preventing bone loss - one example is bisphosphonate. However, I learned that there is one drug, called Forteo, that actually builds new bone. However, it cannot be used on patients who have had irradiation treatment, and so people who have suffered myelomas or other bone diseases are often ineligible. Dr. Lane would often prescribe Forteo for a 24-month period, followed by a bisphosphonate to "lock in" the effects of the Forteo. I am wondering why Forteo is not used more, as I have heard of bisphosphonates but not Forteo before.
This week, I also accompanied Dr. Padgett and Dr. Kelly in the OR to observe three surgeries. The first was a hip arthroplasty revision; the stem of the femoral component was misaligned and impinging on the cortical shell of the femur. The second surgery was performed on a patient who had abnormal bone growths near the femoral stem, neck, and head. These sections had to be removed so the hip would not interfere with normal movement. The third surgery involved a young women who needed bone shaved off of the femoral head so that it would not impinge the acetabular shell. I would describe the orthopedic surgeries as almost barbaric and brutal! The nurses who handed off the tools to the surgeons had between 3 and 4 tables covered with various tools, including hammers and drills! It was almost like carpentry. I was amazed at how resilient the bone was. The surgeons were using a significant amount of force (or so it seemed) during some of the procedures.
Standing for 10 hours (with some breaks of course) was very tiring. I give a lot of credit to the whole staff who has to stand throughout the procedures. I'm not sure that I would be cut out for it! Luckily, the lounge in HSS is filled with cookies, juice, and coffee, so I made sure to keep my blood sugar up and myself hydrated. I really enjoyed the experience and hope that I get to see more surgeries in the future.