A Loading Device to Measure Stiffness of Fractured Bones and Monitor Healing Over Time

At a Glance

Researchers at Colorado State University have developed a non-invasive measurement system and device in which an antenna electromagnetically couples with a patient’s implanted hardware to sense deflections of the hardware due to an applied load. This system and device utilizes displacement and load sensors to determine the stiffness of a limb. When measurements are taken over time, the system can determine whether callus stiffness is increasing and provide diagnostic monitoring of the fracture healing process during critical time points.

The direct electromagnetic coupling method developed here holds strong potential for clinical assessments and predictions of fracture healing. For more details, please contact our office.

Background

Diagnostic monitoring and prediction of bone fracture healing is critical for the detection of delayed union or non-union and provides the requisite information as to whether therapeutic intervention or timely revision are warranted. A promising approach to monitor fracture healing is to measure the mechanical load-sharing between the healing callus and the implanted hardware used for internal fixation.

Overview

When a fracture is stabilized with a fixation plate or intramedullary nail, the implant first carries a high share of the load. As the bone heals, the share of the load on the plate decreases; therefore, the load measurements can be used to monitor the healing process and inform doctors on the proper course of treatment. As the implanted hardware is loaded, the material experiences deformations and displacements due to bending that are proportional to the load. These displacements are detected by an electromagnetic antenna. The electromagnetic profile of the antenna is sensitive to the movement of objects in the near field range. For example, the displacements of the metal due to loading causes a shift in the resonant frequency of the antenna as measured by the S-parameter. The frequency shift is calibrated to determine the load on the implant. Therefore, an antenna is held against a patient’s extremity such that a metal implant is in the near-field range of the antenna and loading the extremity causes displacements of the implant relative to the antenna. The resonant frequency shifts of the antenna are used to measure the load on the implant. Allowing doctors to assess whether a fracture is healing properly, or if further intervention is necessary.
The technology detects loosening of orthopedic implants, for example, in total joint replacements. Since the antenna is sensitive to displacements of the hardware, the increased displacements of a loose implant can be detected.

Benefits

  • No internal sensor required (implant itself provides the signal)
  • Requires no alterations or additions to existing implants
  • Eliminates any regulatory approval hurdles
  • Cost effective

Applications

  • Orthopedic fracture healing monitoring
  • Detection of loosening orthopedic implants (e.g., joint replacements)
  • Research development
Last Updated: October 2023
Opportunity

Available for Licensing

Inventors

Christian M Puttlitz
Kevin M Labus

Reference Number
18-053
Licensing Manager

Steve Foster
Steve.Foster@colostate.edu
970-491-7100