Abstract
Vertebral Modic type 1 (MT1) degeneration may mimic infectious disease on conventional spine magnetic resonance imaging (MRI), potentially leading to additional costly and invasive investigations. This study evaluated the diagnostic performance of the proton density fat fraction (PDFF) for distinguishing MT1 degenerative endplate changes from infectious spondylitis. A total of 31 and 22 patients with equivocal diagnosis of MT1 degeneration and infectious spondylitis, respectively, were retrospectively enrolled in this IRB-approved retrospective study and examined with a chemical-shift encoding (CSE)-based water-fat 3D six-echo modified Dixon sequence in addition to routine clinical spine MRI. Diagnostic reference standard was established according to histopathology or clinical and imaging follow-up. Intravertebral PDFF [%] and PDFFratio (i.e., vertebral endplate PDFF/normal vertebrae PDFF) were calculated voxel-wise within the single most prominent edematous bone marrow lesion per patient and examined for differences between MT1 degeneration and infectious spondylitis. Mean PDFF and PDFFratio of infectious spondylitis were significantly lower compared to MT1 degenerative changes (mean PDFF, 4.28 ± 3.12% vs. 35.29 ± 17.15% [p < 0.001]; PDFFratio, 0.09 ± 0.06 vs. 0.67 ± 0.37 [p < 0.001]). The areas under the curve (AUC) and diagnostic accuracies were 0.977 (p < 0.001) and 98.1% (cut-off at 12.9%) for PDFF and 0.971 (p < 0.001) and 98.1% (cut-off at 0.27) for PDFFratio. Our data suggest that quantitative evaluation of vertebral PDFF can provide a high diagnostic accuracy for differentiating erosive MT1 endplate changes from infectious spondylitis.
Highlights
Erosive osteochondrosis (EO) of the spine constitutes a special form of disc degeneration in which loss of water in the nucleus pulposus leads to a loss of resilience in the fibers of the annulus fibrosus, resulting in increased mobility of the affected disc segment
In Modic type 1 (MT1) stage, thought to indicate an ongoing inflammatory process in EO, vertebral bone marrow compartments close to the intervertebral discs are histopathologically replaced by fibrovascular tissue, accompanied by circumscribed edema zones which might correspond to endplate microfractures [3]
Twenty-five patients with 13 MT1 degenerative changes and 12 infectious lesions were scanned at 1.5T, whereas 28 patients with 18 MT1 degenerative lesions and 10 infectious spondylitis were examined at 3T
Summary
Erosive osteochondrosis (EO) of the spine constitutes a special form of disc degeneration in which loss of water in the nucleus pulposus leads to a loss of resilience in the fibers of the annulus fibrosus, resulting in increased mobility of the affected disc segment. The segmental instability may cause an inflammatory reaction in the adjacent bone marrow compartments which evolves in different stages and is commonly referred to as “Modic changes” [1]. Despite the common terminology of endplate-associated findings, these are signal variations that can extend into the vertebral body to varying degrees [2]. In Modic type 1 (MT1) stage, thought to indicate an ongoing inflammatory process in EO, vertebral bone marrow compartments close to the intervertebral discs are histopathologically replaced by fibrovascular tissue, accompanied by circumscribed edema zones which might correspond to endplate microfractures [3]. Recent research suggests a multifactorial genesis in which activated degeneration is maintained by a proinflammatory milieu of the intervertebral disc, thereby favoring low-grade bony infections [4]. Assessment of EO is an important clinical task because of the positive and very specific association between magnetic resonance imaging (MRI) evidence of MT1 changes and non-specific lower back pain [5]
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