Rice’s model could help clinicians personalize hip flexion

Rice University engineers hope to make life better for those with new joints by modeling how artificial joints tend to rub in the wrong way.

The Brown School of Engineering laboratory computer analysis of mechanical engineer Fred Higgs simulates and monitors how lumps change, including unparalleled fluid dynamics and roughness of surfaces together as well as factors that clinicians typically use to predict how well implants will exceed their expected 15-year lifespan.

The direct goal of the design team is to promote stronger prostheses.

Ultimately, they say the model could help clinicians personalize hip personalization for patients by gender, weight, age and leg changes.

Higgs and co-authors Authors Nia Christian, a Rice graduate student, and Gagan Srivastava, a mechanical engineering lecturer at Rice and now a research scientist at Dow Chemical, outlined their findings Biotribology.

The researchers saw a need to look beyond the confines of previous mechanical studies and conventional clinical practices that use simple walking as a baseline to evaluate artificial limbs without the involvement of higher-impact functions.

When we talk to surgeons, they tell us that many of their decisions are based on their wealth of knowledge. But some have called for a desire for better monitoring tools to predict how long an implant will last. Fifteen years is like a long time but if you have to insert an artificial hip into someone who is young and active, you want it to last longer so they don’t have multiple surgeries. “

Nia Christian, Graduate Student, Rice University

Higgs ’Particle Flow and Tribology Lab with mechanical BJ and bioengineer Rice, was invited to collaborate on his work to model human movement to improve life for patients with neurologic and orthopedic disorders.

“He wanted to see if we could predict how long their best candidate hip joints would last,” said Higgs, Rice John and Ann Doerr Professor of Mechanical Engineering and co. professor of Bioengineering, who inspired his own father’s reincarnation to the extent of the study. “So our model uses a walking movement of real patients.”

Physical simulators need to run millions of cycles to predict wear and failure points, and can take months to get results. The Higgs model seeks to speed up and simplify the process by analyzing real motion capture data such as those performed by the Fregly Laboratory along with data from “learned” hip implants. studied Georg Bergmann at the Free University of Berlin.

The new study covers the four specific physics modes – communication mechanics, fluid dynamics, wear and particle dynamics – at play in hip movement. Previous studies have not considered all four at once, according to the researchers.

One issue that others did not consider was how the beer between bones changed. Natural joints contain synovial fluid, an extracellular fluid with egg-white consistency and secreted by the synovial membrane, a connective tissue that stretches the component. When a hip is replaced, the membrane is retained and continues to dispense the beer.

“In naturally healthy joints, the fluid generates enough weight to keep you from communicating, so we all walk without pain,” Higgs said. “But an artificial hip joint usually goes through a partial joint, which wears and shrinks the joint you have over time. We call this type of mixed massage.”

Such friction can lead to more generation of wear debris, especially from the plastic material – ultrahigh molecular weight polyethylene – commonly used as the socket (the acetabular cup) in artificial joints. These particles, which are estimated at up to 5 microns in size, mix with the synovial fluid sometimes escaping from the component.

“Eventually, they can loosen the implant or cause the surrounding material to break down,” Christian said, “and they are often transported to other parts of the body, where they cause osteolysis. There’s a lot of debate about where they end up but you want them not to contaminate the rest of your body. “

She noted that the use of metal sockets instead of plastic is an interesting topic. “There has been a strong push towards metal-to-metal lumps because metal is durable,” Christian said. “But some of these cause metal cracks to break off. As they build up over time, they appear to be much more harmful than polyethylene particles. “

Further impetus for the new study came from two previous works by Higgs and colleagues who had nothing to do with bioengineering. The first looked at the chemical mechanical polishing of semiconductor components used in integrated circuit manufacturing. The latter pushed their prediction model from a micro-scale to a full-scale wafer interface.

The researchers noted that future versions of the model will include more modern materials being used in combination.