For two years, Jacob Elkins worked as a surgical technician at the Reno (Nev.) Veterans Hospital. He witnessed many hip and knee replacement surgeries and quickly learned that these implants can fail.
“When they fail, it’s horrible for the patients,” Elkins says. “Sometimes, they need multiple revision surgeries, increasing the risk of vascular injury, neurological injury, infection, and even limb loss.”
Motivated to make a difference, Elkins enrolled in the University of Iowa’s M.D./Ph.D. Program in Biomedical Engineering in 2005 and developed the first computational model that simulates the hip dislocation process as it actually occurs in the human body. It took Elkins a full year and a half to develop the model, which became the centerpiece of his doctoral dissertation. Elkin’s research has garnered interest in his field, resulting in eight published/accepted papers and thirty-five conference presentations.
Elkins’ dissertation, “Biomechanics of Failure Modalities in Total Hip Arthroplasty,” details his research on the failure of total hip implants due to impingement and/or dislocation.
“Jake’s dissertation research has broken new ground in the area of computational biomechanics and finite-element modeling as applied to orthopaedics,” says Joseph Reinhardt, professor of biomedical engineering and member of Elkins’ dissertation review committee. “His dissertation will have a lasting impact on how medical implants are designed and how we treat patients with orthopaedic disorders.”
Model of normal hip function
The first portion of Elkins’ thesis outlines the overall model formulation, with particular emphasis on the hip capsule—a thick jacket of ligamentous tissue that surrounds the joint.
“He kept getting slapped down by the algorithm for the model and he kept bouncing back up,” says Thomas Brown, Richard and Janice Johnston Chair of Orthopaedic Biomechanics and Elkins’ dissertation advisor. “I really love the guy’s perseverance. He is a warrior. His capsule model isn’t something for the faint-hearted. From a biomechanics standpoint, it’s been so difficult to quantify.”
Problems with metal implants
The second section focuses on implant problems that occur due to impingement, which is caused by a lack of room or clearance between the neck of the femur and the rim of the hip socket.
This work has several potential applications, including solutions for impingement problems that occur in metal-on-metal implant designs, currently a pressing clinical concern due to large numbers of early failures of this class of implants.
“I started looking at metal-on-metal, because these things were failing at astronomical rates, but they shouldn’t have,” Elkins says. “From an engineering perspective, metal-on-metal bearings are superior to anything else out there, but when you put them in a patient, they weren’t working. The bottom line is the actual design of the implant was sub-optimal. People designing the implant didn’t look at various factors that we’re able to explore readily with this model.”
One factor implicated in implant failure is edge-loading, which occurs when too much pressure is placed between the edge of the metal cup and the ball. Such pressure dramatically increases the rate at which the replacement joint deteriorates. The tiny metal particles that wear off the joint through edge-loading can lead to loosening in the joint. The particles can also inflame surrounding flesh and enter the bloodstream, causing illness or injuries elsewhere in the body.
Problems with ceramic implants
Next, Elkins’ dissertation describes fractures that can occur in ceramic total hip implant designs, which serve as an alternate to metal-on-polyethylene and metal-on-metal bearings. Ceramic implant fractures are rare, but when they happen the result is disastrous. Elkins approaches this issue computationally, since many ceramic fractures occur due to impingement.
“My favorite part of his dissertation is the fracture work,” Brown says. “To simulate that computationally, which is very desirable from a design standpoint, was a bear. Jake picked that up beautifully.”
In addition to winning the UI Spriestersbach Prize and placing among the top dissertations in the national competition, Elkins received the prestigious William H. Harris, MD Award from the Orthopaedic Research Society in 2011. This award, sponsored by the Harris Fellows Club, honors an individual based on the quality and scientific merit of a paper submitted to members of the Orthopaedic Research Society Special Projects Committee.
Elkins also was honored by his faculty mentor.
When Brown received the Orthopaedic Research and Education Foundation’s Clinical Research Award in 2012, he recognized Elkins as a co-author on the winning project, “Impingement and Dislocation in Total Hip Arthroplasty: Mechanisms and Consequences.”
“We’ve done a lot of research in this lab through the years,” Brown says. “On Jake’s watch, the research was beautifully brought to closure. It was sheer hard work; he put in huge hours.”