March/April 2002 edition
Life Engineer: Refining the Human Machine
From peg-legs to pacemakers, humans have engineered themselves for centuries. Joel M. Bach, assistant professor of Engineering at CSM, is raising our endless quest for self-improvement to new heights. His work in biomechanics and biomedical engineering is improving the lives of many people, from disabled children and surgical patients to downhill skiers.
Children with severe cerebral palsy lose control of their muscles and sometimes the ability to sit upright, which can cause scoliosis. Bach, who is also an assistant professor and director of biomechanics research at the University of Colorado Health Sciences Center (UCHSC), studies better ways to help these children regain mobility. "It's a medically important problem that affects children's quality of life," Bach said.
The traditional solution is surgical implantation of a metal rod against the patient's spine. The rod is wired to the spine and fits into holes drilled in the pelvis. Ideally, the implant provides support long enough for the spinal bones to fuse and hold the child upright. However, the lowest pair of wires can fail before the bones fuse. When these wires fail, the rod is no longer tightly held to the spine and it slides inside the holes in the pelvis. A second traumatic surgery is required to correct the problem. Bach and his colleagues at UCHSC and The Children’s Hospital developed a modified spinal implant that would resist failure and reduce the need for another surgery.
In the new implant, the two lowest wires holding the rod to the spine are replaced by a pedicle screw. The screw is drilled into the vertebra and clamps onto the support rod. The team tested the strength of this arrangement by fitting the spines of six cadavers with the all-wire implant and six others with the new implant. They measured displacement between the bone and the rod as stress was applied to the spine in different orientations.
The new implant outperformed the old. It provided 50 percent more stiffness (the ratio of load to amount of displacement) and withstood twice as much load before failing. The new implant is also successful because it does not increase the cost or complexity of surgery. "This technique minimizes the chance of complications," Bach said. "I don't think there's any downside to using it."
Bach's future research may involve adding more hardware to strengthen the implant, conducting studies using more specimens, and developing a computer model of the spine so that virtual experiments can be performed.
Measuring Twice, Cutting Once
Orthopedic surgery can be more of an art than a science. An operation is typically planned using two-dimensional x-rays and the surgeon's judgment. For example, a common hip surgery involves cutting a muscle away from the bone at one location and reattaching it to another. The surgeon examines x-rays of the hip and uses his or her experience to decide where to cut and where to reattach the muscle. The result may not be optimal, even with the best surgeon.
Bach has written computer software that optimizes the surgical plan based on the biomechanics of the hip joint. Key points from the x-rays are collected, and the software calculates the geometry and forces that will result from different placements of the muscle. The surgeon is then able to choose the optimal configuration. Bach has completed software for two-dimensional optimization and is working on three-dimensional optimization.
Planning surgery is one thing, performing surgery is another. "Orthopedic surgeons say they measure with a micrometer and cut with an axe," Bach said. One way for surgeons to be more precise is by using a surgical navigation system.
In these systems, sensors are attached to the surgical instruments and to the patient. Cameras monitor the sensors and show precise real-time positions of the instruments and patient. Such systems are currently designed only for a specific task, such as emplacing a bone screw, making them "quarter-million dollar screwdrivers," according to Bach. He aims to make surgical navigation systems more flexible by combining them with surgical planning software. "The computer can guide the surgeon to match the engineering analysis," he said.
There are several advantages to this approach. It is cost effective because it allows the surgical navigation system to be used for numerous types of surgery. It allows surgeons to attain a high level of precision without using robots, which are not approved for use in the United States. It also makes remote surgery possible. A specialist could create an optimal surgical plan and transmit it to a less experienced surgeon, who can follow the plan while operating thousands of miles away.
Work on this project will be enhanced by a computer biomechanics laboratory that is being built at CSM. The laboratory will benefit from Bach's knowledge of biomechanics and the knowledge of computer experts at CSM.
Repairing Damage to the Human Body
Skiing at warp speed down a mogul-covered slope is great fun. Suffering a severe knee injury is not. Bach built a machine to apply different stresses to the knee to determine how knee ligament injuries occur and how to prevent them. The data from these tests is being used to design computerized ski bindings. The bindings will account for the height and weight of a skier, measure muscle contractions and stresses, and would automatically release when knee failure is imminent.
A common method for repairing broken long bones, such as the femur, involves placement of a rod through the hollow bone. To place the rod, the surgeon must first ream out the bone. The friction caused by reaming creates heat that can damage bone and tissue. Bach and his colleagues are working on a technique that measures the infrared light produced by heat and lets the surgeon know when to allow the bone to cool.
Headlines from the March/April edition of Technology Community
Page 2 Shock Proofing: From Mirco-machines to Space Station
OUT IN FRONT
Page 3 President Names Council on BioEthics
Page 4 First Ever Rotary eClub Open to Memberships
COLUMNS & NEWS
Page 5 News & Colorado Photonics Industry Association
Page 6 Colorado Business Advancement Center
Page 7 Technology Transfer Society &
TIPS & TREASURES
Page 8 Colorado Environmental Business Alliance
Page 9 Rockies Venture Club
Page 10 NCSE Releases handbook of Federal Funding for Environmental R&D
Page 11 Department of Energy
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