Novel Methodology for Using Radiostereometric Analysis to Monitor Fracture Healing

Abstract

Background: Radiostereometric Analysis (RSA) is a method for performing highly accurate three-dimensional measurements in-vivo using sequential radiographs. RSA has been used extensively for monitoring prosthesis fixation in hip and knee replacements. Recently, there has been increasing interest in applying RSA towards the monitoring of fracture healing. Objective: The objective of this study was to evaluate the feasibility of using RSA to measure strain, stress, and plate migration in a distal femur fracture model. Methods: Femoral sawbones with a distal femur fracture were used as models. A distal femur condylar locking compression plate (LCP) was used to reduce the fracture model. Stainless steel screws were used to fasten the plate to the sawbone. In addition, translucent polyester screws were composed, embedded with 1mm steel beads, and fastened to the most proximal and distal portions of the plate. This allowed for recognition by the RSA imaging modality. The femoral sawbones were then placed in a mechanical testing complex and RSA X-rays taken at different forces of compression. The radiographs were analyzed for plate migration using the 1mm steel beads as points of reference. Results: Preliminary data indicate that it is possible to use a plate model that incorporates a micro-bead system to measure migration. Further analysis will quantify the amount of migration to determine whether significant changes occur at different stages of compression. Conclusion: The ability to measure plate migration in a Radiostereometric Analysis X-ray model is an important step towards improving the ability of orthopedic surgeons to monitor fracture healing and prevent non-union. The next stage of this research will involve using this model in clinical trials of distal femur fractures and building a database to correlate levels of plate migration with surgical outcome.