Paownder SL, Koff MF, Shah PJ, et al.
American College of Veterinary Radiologists 2012:84.
Introduction/Purpose: Evaluation of the instrumented canine stifle joint is technically challenging, and conventional radiographs and computed tomography fail to adequately address soft tissue injuries. MRI provides excellent soft tissue resolution; however, it suffers from susceptibility artifact in the presence of indwelling hardware. Additionally, common veterinary implants such as tibial plateau leveling osteotomy (TPLO) are stainless steel, which produces the greatest artifact among the metals available for implantation. Protocols to create diagnostic images of the
canine stifle instrumented with stainless steel are needed as none currently exist.
Methods: A pilot study was performed using a cadaveric canine limb. A stainless steel TPLO implant was applied to the right stifle, and MRI was performed using narrow receiver bandwidth fast spin echo imaging (nbw-FSE), wide bandwidth FSE (wbw-FSE), and a prototype pulse sequence (multi-acquisition variable-resonance image combination [MAVRIC]), which is optimized to provide superior spectral coverage and reduced artifact. A scoring system was created to determined conspicuity of soft tissue structures (0-not seen, 1-seen). Twenty structures of the medial stifle joint were assessed including meniscal horns, ligament attachments, articular cartilage, and neurovascular structures. Comparisons were made to a non-instrumented limb using standard-of-care wbw-FSE.
Results: The instrumented limb received a score of 4/20 with nbw-FSE, 11/20 with wbw-FSE, and 14/20 with MAVRIC. A score of 15/20 was achieved when combining results of wbw-FSE and MAVRIC. The non-instrumented limb yielded a score of 20. Wbw-FSE yielded higher spatial resolution. MAVRIC demonstrated the greatest artifact reduction. Only MAVRIC was able to evaluate the medial meniscus in its entirety (Figure 1).
Discussion/Conclusion: Stainless steel TPLO implants create large susceptibility artifact that precludes evaluation of important soft tissue structures of the medial stifle joint, including articular hyaline cartilage and fibrocartilage when using traditional MRI pulse sequences. A combination of wbw-FSE and MAVRIC pulse sequences reduce susceptibility and aid in evaluation of the joint.