Challenge:
Post-surgical complications are more common in elderly patients with weaker bones. Researchers at the Munich University of Applied Sciences wanted to create realistic models of different repair options to determine which were best for these osteoporosis patients.
Solution:
Dassault Systèmes SIMULIA’s Simpack software enabled the researchers to created detailed, flexible, multi-body simulations of broken bones and the surgical techniques used to repair them. Simpack models accurately captured damage that can result over time when abnormal bones respond to forces resulting from different methods of surgery.
Benefit:
With their Simpack simulations verified against actual patient data, the researchers can offer their models to surgeons as useful tools for analyzing clinical problems. They see potential for using Simpack to model other biomedical applications going forward.
Almost everyone damages their shoulder—the blade, collar bone or upper arm bone—at some point in their life, according to the American Academy of Orthopedic Surgeons (AAOS). If you’re lucky you just get a bad bruise or sprain, but you can break the upper arm bone— the proximal humerus—fairly easily: The AAOS says that a fall, a collision, or a motor vehicle accident are the most common causes of such a fracture. The elderly are particularly susceptible to injury due to the loss of bone density, i.e. osteoporosis, with age.
As described by the AAOS, during a surgical procedure to set a fracture, the bone fragments are first repositioned (reduced) into their normal alignment. They are held together with special implants, such as biocompatible stainless steel or titanium plates secured by screws or nails. Internal fixation allows shorter hospital stays, enables patients to return to function earlier, and reduces the incidence of improper healing and positioning of broken bones.
The surgical procedure that stabilizes and joins the ends of fractured bones with implanted mechanical devices is called osteosynthesis. While osteosynthesis can be highly successful in restoring normal shoulder function, “choosing which type of implant to use at the break is critical to long-term success,” says Martin Ott, B.Sc., Munich University of Applied Sciences. “In the last few years more so-called ‘angular locking implants’ are being used.” Locking means a fixed, rigid connection that doesn’t allow any movement between a plate implant and its locking screws.
The latest surgical techniques may not benefit elderly patients
“In general this type of implant produces an increase in the connectivity between the bone and the prosthesis as well as higher stability,” says Ott’s colleague, Dr. Stefan Lehner. “But, particularly when the patient is older and has osteoporosis, we see an increased number of metal/bone screw ‘cutouts’ happening.”
For his Bachelor of Science thesis, Ott wanted to explore bone-repair alternatives to help surgeons decide which surgical options would be best for older patients. “The in vivo stresses of different implants are almost unknown,” says Ott. “We wanted to investigate these stresses to see if we could predict which methodology produces the optimum results.” He teamed with Lehner, a lecturer in biomechanics at the university, on the project.
The researchers set up a study to compare the biomechanics of an angular locking nail osteosynthesis versus an angular locking plate osteosynthesis in terms of the risk of a bone screw cutout at the head of the proximal humerus. They were able to obtain CT scan data from actual patients that provided measured in vivo loads. “This way we could simulate realistic activities and measure the displacements of the stabilizing interacting bodies,” says Lehner.
Want to learn more?
Discover how doctors are leveraging simulation technology to for biomedical simulations.
Read the Munich University case study
