BioMed Research International. 2016;2016:1429892.
Magnetic Resonance Imaging of Postoperative Fracture Healing Process without Metal Artifact: A Preliminary Report of a Novel Animal Model.
Zhe Jin1, Yuheng Guan2, Guibo Yu2, and Yu Sun1
1 Department of Orthopaedics, First Hospital of China Medical University, Shenyang 110001, China
2 Department of Radiological Diagnosis and Interventional Treatment, First Hospital of China Medical University, Shenyang 110001, China
Background. Early radiological diagnosis and continual monitoring are of ultimate importance for timely treatment of delayed union, nonunion, and infection after bone fracture surgery. Although magnetic resonance imaging (MRI) could provide superior detailed images compared with X-ray and computed tomography (CT) without ionizing radiation, metal implants used for fracture fixation lead to abundant artifacts on MRI and thus prohibit accurate interpretation. The authors develop a novel intramedullary fixation model of rat femoral fracture using polyetheretherketone (PEEK) threaded rods and investigate its feasibility for in vivo MRI monitoring of the fracture healing process without artifact.
Methods. Femoral fractures of 3 adult male Sprague-Dawley rats were fixed with intramedullary PEEK threaded rods. X-ray and MRI examinations were performed at day 7 postoperatively. Radiological images were analyzed for the existence of artifact interruption and postoperative changes in bone and peripheral soft tissue.
Results. Postoperative plain film revealed no loss of reduction. MRI images illustrated the whole length of femur and peripheral tissue without artifact interruption, and the cortical bone, implanted PEEK rod, and soft tissue were clearly illustrated.
Conclusion. This preliminary study introduced a novel rat model for in vivo MRI monitoring of the fracture healing process without metal artifact, by using intramedullary fixation of femur with PEEK threaded rod.
Fracture nonunion or non-healing is a common and severe postoperative complication in patients with long bone fractures of upper and lower extremities. The incidence rate could be 14% and 13.9% for tibia and femur respectively, and surgical intervention itself is a major risk factor. [1-3] For decades orthopaedic surgeons have been using a diagnostic protocol based on X-ray or CT examination aiming at detecting calcified fracture site tissues, which will take at least 3 or even 9 months to establish a definitive diagnosis and may have missed the best period for early diagnosis and intervention.
The fracture healing process is comprised of several complex pathophysiological stages including hematoma formation, fibrous callus formation and transformation into cartilaginous callus, mineralization of cartilaginous callus and bone remodeling established by published lab researches.[4-7] However, current diagnostic protocols could not identify or evaluate early biological events before callus mineralization. As to the working principle, magnetic resonance imaging (MRI) could provide detailed anatomical and functional information of inflammatory hematoma and fibrous/cartilaginous tissue at early critical stages of fracture healing. While commonly used metal implants for fracture fixation induced strong artifacts in magnetic field, limiting the application of MRI for the research of bone healing.
The aim of our project is to get around the above technical limitations and to bridge the gap between lab studies and clinical practice. First of all, we established in vivo animal models of normal fracture healing and nonunion mimicking clinical operation procedure and allowing postoperative continual MRI examinations without metal artifact.[8-9] Using these animal models we are now conducting further in vivo investigations which may provide novel preclinical research strategies for early diagnosis and therapies for postoperative fracture nonunion.
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 Kolar P, Schmidt-Bleek K, Schell H, et al. The early fracture hematoma and its potential role in fracture healing. Tissue Eng Part B Rev. 2010;16(4):427-34.
 Wang T, Zhang X, Bikle DD. Osteogenic Differentiation of Periosteal Cells During Fracture Healing. J Cell Physiol. 2017;232(5):913-921.
 Hankenson KD, Gagne K, Shaughnessy M. Extracellular signaling molecules to promote fracture healing and bone regeneration. Adv Drug Deliv Rev. 2015;94:3-12.
 Jin Z, Sun Y, Guan Y, Yu G. A Novel Rat Model of Intramedullary Tibia Fracture Fixation Using Polyetheretherketone Threaded Rod. Plast Reconstr Surg Glob Open. 2015 Jul 8;3(6):e417.
 Jin Z, Guan Y, Yu G, Sun Y. Imaging of Postoperative Fracture Healing Process without Metal Artifact: A Preliminary Report of a Novel Animal Model. Biomed Res Int. 2016;2016:1429892.
First author Dr. Zhe Jin (left) and corresponding author Dr. Yu Sun (right) in the First Hospital of China Medical University.
Yu Sun, M.D.
Lecturer, attending physician and researcher
Dept of Orthopaedics
First Hospital of China Medical University
Shenyang, Liaoning, China 110001