By Varshini Kamaraj
It is common to witness older family members undergoing knee or hip replacements due to degenerative joint disease. Unfortunately, most of these individuals aren’t satisfied with the end results of their corrective surgeries.
To address patient dissatisfaction, Dr. Joshua Roth, a postdoctoral fellow from the department of mechanical engineering at University of Wisconsin-Madison develops patient-centered methods in his research at the UW Neuromuscular Biomechanics Laboratory. Roth presented his research at the Mechanics Seminar on February 23, 2018.
Roth’s research focuses on improving existing treatments for osteoarthritis of the knee. Osteoarthritis is a condition where the cartilage in the joints of the human body breaks down. When this occurs in the knee, patients experience pain and loss of knee function. The most effective treatment for this condition is total knee replacement (TKR) surgery.
Currently, up to 25% of patients who undergo TKR are reportedly unsatisfied. Roth explains, “This is a huge number because it is projected that up to 1.5 million total knee replacements will be performed annually in the U.S. alone by 2020, and if you do the math that means 375,000 patients per year who aren’t happy with their knee and that’s a lot of patients. So TKR must improve to reduce the number of dissatisfied patients.”
Through his interactions and observations with orthopedic surgeons, Roth traces a probable source of patient dissatisfaction to improper tensioning of soft tissues during surgery. These soft tissues are structures connecting the long bones of the leg that provide joint stability in the knee and, when improperly tensioned, it can lead to pain and discomfort after the surgery. Orthopedic surgeons assess the ‘tightness’ of the tissues typically by holding the foot and thigh and wiggling the lower leg around. Depending on whether the tissue feels tight or loose, surgeons decide to either release the tension or increase it. The problem in the treatment arises due to a lack of a well-defined way to measure the ‘tightness’ or ‘looseness’ of the tissues.
Current technological advancements that help give surgeons a more concrete measurement include placing an instrumented device onto the structures of the knee during surgery. This device measures the contact forces between the bones. Although the contact forces are related to the tension in the tissues, they only provide a summation of forces at the joint and do not convey to surgeons which exact tissue needs to be tightened or loosened.
Roth attempts to overcome the current issues in TKR procedures by using a sensor technology called a shear wave tensiometer. The sensor is currently being developed in the UW Neuromuscular Biomechanics Laboratory and could be used to measure the tension in the knee’s soft tissues. Roth envisions that surgeons could use the sensor to measure tensions and detect if they are incorrect. Using the data from the sensor, surgeons can then use computer simulations to find the best possible solution and then execute the procedure on patients using surgical robots.
The challenging part, according to Roth, is translating the technical solutions he has discovered to clinicians and developing a user-friendly version of the technology. He hopes that his solutions can reach patients and clinicians within the next ten years.