Abstract
Performing MR investigation on patients instrumented with external fixators is still controversial. The aim of this study is to evaluate the quality of MR imaging of the knee structures in the presence of bridging external fixators. Different cadaveric lower limbs were instrumented with the MR-conditional external fixators Hofmann III (Stryker, Kalamazoo, MI, USA), Large external Fixator (DePuy Synthes, Raynham, MA, USA), XtraFix (Zymmer, Warsaw, IN, USA) and a newer implant of Ketron Peek CA30 and ERGAL 7075 pins, Dolphix®, (Citieffe, Bologna, Italy). The specimens were MR scanned before and after the instrumentation. The images were subjectively judged by a pool of blinded radiologists and then quantitatively evaluated calculating signal intensity, signal to noise and contrast to noise in the five regions of interest. The area of distortion due to the presence of metallic pins was calculated. All the images were considered equally useful for diagnosis with no differences between devices (p > 0.05). Only few differences in the quantification of images have been detected between groups while the presence of metallic components was the main limit of the procedure. The mean length of the radius of the area of distortion of the pins were 53.17 ± 8.19 mm, 45.07 ± 4.33 mm, 17 ± 5.4 mm and 37.12 ± 10.17 mm per pins provided by Zimmer, Synthes, Citieffe and Stryker, respectively (p = 0.041). The implant of Ketron Peek CA30 and ERGAL 7075 pins showed the smallest distortion area.
Highlights
Bridging external fixation of the knee must be implemented for the temporary emergent stabilization of the knee joint [1,2]
Gillig J.D. et al reported that magnetic resonance imaging (MRI) imaging in Schatzker IV, V and VI tibial plateau fractures better visualized bone landmarks and could avoid the use of computer tomography (CT), experiencing no complications [14]
A meniscal tear was diagnosticated on the Limb B and it was detectable and classifiable in each MR study performed on the limb
Summary
Bridging external fixation of the knee must be implemented for the temporary emergent stabilization of the knee joint [1,2]. MRI has been associated with a more accurate classification of fractures involving the knee, a better identification of occult fracture lines and more detailed measurement of displacement of bone fragments in tibial plateau fractures compared to plain radiographs or computed tomography [12,13]. Another aspect related to the use of MRI is the assessment of soft tissues such as cruciate and collateral ligaments after knee dislocation, where the use of temporary stabilization is often advocated [6]. Gillig J.D. et al reported that MRI imaging in Schatzker IV, V and VI tibial plateau fractures better visualized bone landmarks and could avoid the use of computer tomography (CT), experiencing no complications [14]
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