Original Study

Utility of the claw sign in spine magnetic nuclear resonance with diffusion to differentiate Modic type I changes for degenerative disease versus infection

Juan Esteban Muñoz Montoya, Carlos Pérez Cataño, Angela María Tapicha Cuellar, Maria Paula Vargas Osorio, Jimar Rivero Cano, Juan Carlos Luque Suarez, Marco Luciano Charry Lopez


Background: In 1988, Modic and his colleagues described changes in the subchondral bone marrow of the vertebral plates in patients with degenerative disease or other pathologies, which were observed in the nuclear magnetic resonance (NMR) of the spine and were subdivided into three patterns of signal changes, called Modic type I, Modic type II and Modic type III. The main differential diagnosis of the Modic I changes of the vertebral plates due to degenerative disease in spine NMR, is infection in its early stages. In their study in 2014, Patel and collaborators, using a protocol and the concept of diffusion in spine MRI, were able to demonstrate that by means of the “claw sing”, a degenerative disease with Modic type I changes, can be differentiated from an infection in early stages. In this series of cases, the algorithm used by Patel et al. was implemented.
Methods: The clinical records of patients who consulted the emergency department for lumbar pain without clear etiology, between January 1, 2017 and December 31, 2017, were analyzed. Due to axial lumbar pain, subjects were hospitalized and studies were ordered, including contrasted MRI of the lumbosacral spine. Then, with laboratory tests and MRI findings of Modic type I changes, it was not possible to differentiate between degenerative disease vs. spondylodiscitis. Therefore, the algorithm used in the study by Patel and collaborators was applied.
Results: There were 13 patients identified with lumbar or dorsal pain over 3 months of evolution, with nonspecific symptoms; 5 patients (38.46%) reported arterial hypertension, 4 patients (30.77%) diabetes mellitus, and 4 patients (30.77%) chronic kidney disease stage V in management with hemodialysis, 3 patients (23.08%) presented immunosuppressive conditions and 3 patients (23.08%) had a history of spinal surgery with instrumentation. All the patients were hospitalized and a lumbosacral and thoracic spine simple MRI was performed with Modic type I changes to perform contrast-enhanced MRI with diffusion and ADC. From the 13 cases studied for low back pain, there were 7 patients (53.85%) with confirmed findings of Modic type I changes due to degenerative disease for presenting claw sign in spinal MRI diffusion and 6 patients (46.15%) Modic type changes I due to infection in the absence of a claw sign in the column MRI diffusion.
Conclusions: Spinal column MRI with diffusion is useful to differentiate patients with type I changes due to degenerative disease with positive claw sign; of patients with type I changes due to infection with absent claw sign. In addition, in patients with compromised renal function, column MRI with diffusion without contrast could be a diagnostic alternative, since it does not require contrast media to confirm infection.

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