From Jets to Joints
To assess the wear and tear on jet engine parts, mechanics used an old technology called ferrography to run the aircraft’s 
lubricating fluid through a magnetic device to separate out metal shavings and other ferrous engine debris. URI Assistant Professor of Mechanical Engineering Donna Meyer uses a similar process to assess the wear and tear on artificial hip and knee joints so patients can reduce the number of follow-up surgeries they must undergo or reduce the time spent in revision surgery.
Meyer envisions using her research to create a “wear atlas” that can be used by orthopedic surgeons as a diagnostic tool.
Most artificial hips consist of a polyethylene socket and metal ball or metal-on-metal combinations that are connected to adjoining bones with screws or cement. Total knee replacements are made of similar materials. Over time as the ball, socket, and bone rub against each other, tiny debris is produced and settles between the bone and the implant interface, discouraging the much-needed growth of bone around the prosthesis. This contributes to the loosening and separation of the interface, which necessitates revision surgery to repair it.
“Polyethylene wear debris can be a significant problem for patients because a loosened joint can cause great discomfort,” said Meyer. “If we can determine the number and size of wear debris contained in a patient’s synovial fluid, and also look at the ratio of polyethylene to other constituents like metal, bone, and cement particles, we can create a tool to assist in diagnosing the problem with the implant before surgery is necessary. Ultimately we would like to minimize the number of revision surgeries that patients face, or at least minimize the amount of time spent in surgery for additional operations.”
Meyer takes a sample of a patient’s synovial fluid, which is part of the lubricating fluid surrounding knees and hips, and uses a process called bio-ferrography to capture the tiny particles of polyethylene, metal, bone and cement with a very strong magnet. Since most of the wear debris isn’t magnetic and therefore wouldn’t be collected by the device, she adds to the fluid sample a magnetic compound that binds to the non-magnetic particles.
Once she perfects the technique for collecting the wear debris, she will begin creating the atlas. Meyer said the atlas will be designed so doctors can easily compare a patient’s age, activity level, implant type and time since implantation with the size and composition of the wear debris to quickly determine which part of the implant is the likely cause of the problem.
“The atlas can be used by doctors as a maintenance guide, in addition to a radiograph for example, and hopefully give more information about early wear detection, just like the guides used by aircraft mechanics,” she said.
lubricating fluid through a magnetic device to separate out metal shavings and other ferrous engine debris. URI Assistant Professor of Mechanical Engineering Donna Meyer uses a similar process to assess the wear and tear on artificial hip and knee joints so patients can reduce the number of follow-up surgeries they must undergo or reduce the time spent in revision surgery.Meyer envisions using her research to create a “wear atlas” that can be used by orthopedic surgeons as a diagnostic tool.
Most artificial hips consist of a polyethylene socket and metal ball or metal-on-metal combinations that are connected to adjoining bones with screws or cement. Total knee replacements are made of similar materials. Over time as the ball, socket, and bone rub against each other, tiny debris is produced and settles between the bone and the implant interface, discouraging the much-needed growth of bone around the prosthesis. This contributes to the loosening and separation of the interface, which necessitates revision surgery to repair it.
“Polyethylene wear debris can be a significant problem for patients because a loosened joint can cause great discomfort,” said Meyer. “If we can determine the number and size of wear debris contained in a patient’s synovial fluid, and also look at the ratio of polyethylene to other constituents like metal, bone, and cement particles, we can create a tool to assist in diagnosing the problem with the implant before surgery is necessary. Ultimately we would like to minimize the number of revision surgeries that patients face, or at least minimize the amount of time spent in surgery for additional operations.”
Meyer takes a sample of a patient’s synovial fluid, which is part of the lubricating fluid surrounding knees and hips, and uses a process called bio-ferrography to capture the tiny particles of polyethylene, metal, bone and cement with a very strong magnet. Since most of the wear debris isn’t magnetic and therefore wouldn’t be collected by the device, she adds to the fluid sample a magnetic compound that binds to the non-magnetic particles.
Once she perfects the technique for collecting the wear debris, she will begin creating the atlas. Meyer said the atlas will be designed so doctors can easily compare a patient’s age, activity level, implant type and time since implantation with the size and composition of the wear debris to quickly determine which part of the implant is the likely cause of the problem.
“The atlas can be used by doctors as a maintenance guide, in addition to a radiograph for example, and hopefully give more information about early wear detection, just like the guides used by aircraft mechanics,” she said.