Engineering better surgical techniques for a common sports injury

Feb 13, 2004

Football players and female athletes will jump for joy when researchers at Kettering University and McLaren Regional Medical Center complete their experiments into improving Anterior Cruciate Ligament (ACL) surgery.

Football players and female athletes will jump for joy when researchers at Kettering University and McLaren Regional Medical Center complete their experiments into improving Anterior Cruciate Ligament (ACL) surgery.

Funding for the ACL research project was provided by Dane Miller, CEO of BioMet and Kettering University Board of Trustees member and alumnus, and the McLaren Foundation.

The Anterior Cruciate Ligament (ACL) is a knee ligament that runs down the middle of the knee from the mid-thigh to mid-calf. An injury to the ACL usually falls under the purview of sports medicine. According to Dr. Patrick Atkinson, associate professor of Mechanical Engineering at Kettering, it is a fairly common sports injury.

"This particular ligament is right in the middle of the knee, you can't even palpitate it. It is attached to the middle of the thigh bone and the middle of the shin bone, and helps keep those bones together," said Dr. Brian Rill, M.D., McLaren orthopedic surgery resident.

"Football players are always tearing their ACL - they are the most prone to this injury," said Atkinson. Breaking or tearing the ACL occurs when an athlete cuts hard to the side while the foot stays fixed to the ground. "The body is trying to go in a new direction and the knee bears the brunt of the maneuver," he said, "that's when you snap the ligament." Statistically, the injury is significantly more common in women athletes than men.

When the ACL snaps the individual loses the stability of the knee joint. The knee is a hinge-like joint, and without an ACL, it becomes a very sloppy joint. Atkinson likened it to a door hinge with slightly loose screws; the door doesn't just rotate open and closed, it slops back and forth too, it will "chatter." "That's what your knee will do, so instead of nice smooth back and forth motion, it will slop and make your step unstable," said Atkinson.

The injury can be fixed, in fact, ACL surgery is quite common. The procedure involves taking a piece of tendon from another part of the knee and inserting it where the torn ligament used to be.

"What we are looking at is how to improve the surgical processes used to repair ACL injuries using mechanical engineering," Atkinson said. "The current surgical procedure works pretty well. It reconstructs the ACL so the knee feels tight and normal, but one negative outcome is that patients complain about knee pain in an area not originally injured," he said. The ACL reconstruction is altering the normal bio-mechanical performance of the knee.

"We hypothesize that the pain is due to altered contact stresses between the knee cap and end of thigh bone," Atkinson said. The researchers have developed, and are going to try, a new surgical procedure on knee models to attempt to alleviate these excessive pressures.

Equipment to conduct this type of research is so specialized that the research team had to build their own. What they needed was an Oxford Rig. The first Oxford Rig was built at Oxford University, England, in the 1970's. It is designed to simulate the human hip and upper leg functions. There is no manufacturer of Oxford Rigs because they have limited application. Replicas are built by individual research teams to specifications taken from the original rig. Clifford Colwell, M.D., an orthopaedic surgeon in San Diego assisted with the specifications for the Kettering/McLaren rig.

Dan Van Cura, a Mechanical Engineering lab technician and student at Kettering, built the Kettering/McLaren Oxford Rig, and Dr. Jeff Hargrove, associate professor of Mechanical Engineering, wired the electronics for the ACL research project.

The team working to improve surgical techniques to repair torn ACLs includes Atkinson, Dr. Sidney Martin, M.D., of Family Orthopaedics, Dr. Brian Rill, M.D., McLaren resident, Dr. Scott Anseth, M.D., McLaren resident, Ishamel Dean-Al, Mechanical Engineering graduate student at Kettering, and Jason Snyder, Mechanical Engineering undergraduate at Kettering. The Kettering/McLaren ACL project was originally the idea of Lewis Martin, M.D., an orthopaedic surgeon in Georgia. Research started May of 2003 and is expected to be completed in the summer of 2004.

What is the difference between a ligament and a tendon? Not much in terms of material - the difference is in their function. Ligaments and tendons are made from the same material, but they are attached to different things. Ligaments attach a bone to a bone, tendons attach a muscle to a bone.

The opportunity to work on this type of research is common at the graduate level, but rare for undergraduate students. Jason Snyder said of the experience that he has be able "to do a lot more things than most undergrads get to experience. I've learned a lot from the doctors I've worked with at McLaren. I had an interest in bio-medical engineering from the beginning, but being able to work on research with Dr. Atkinson has helped me decide to pursue medicine as a career. I wouldn't have had this hands-on opportunity at a larger university," he said.

The research opportunities have enabled graduate student Ishmael Dean-Al to combine his interest in motorcycles with his degree in mechanical engineering and his experiences in bio-engineering, making him a cross-trained engineer. "What we have created is a graduate with a high demand specialty," said Atkinson.

After completion of testing, researchers will analyze the data and publish their findings.

Written by Dawn Hibbard
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