Thesis

126 Part I Chapter 5 imaging. In CNC, CT will often reveal a narrowed space between the calcaneus and navicular, with elongation of the anterior process and a hypertrophic distally squared bony surface (anteater nose sign). Cartilaginous TCs may mimic osteoarthritis with space narrowing, mild sclerosis (eburnation), and subchondral cysts in an otherwise normal foot without other sites of osteoarthritis [8]. CT alone also has known limited sensitivity in cartilaginous and fibrous TCs [12]. Moreover, it is noteworthy that correlation between the changes on CT and pain complaints may be challenging as solely anatomical changes in TCs are often asymptomatic. Magnetic Resonance Imaging (MRI) can be useful for characterization of (suspected) TC, with especially high accuracy for soft tissue abnormalities [8, 12]. In osseous TCs, an abnormal osseous continuity with bone marrow signal (high signal on T1weighted images, low signal on T2-weighted fat-suppressed images) is seen similar to the normal bone [8]. Cartilaginous TCs will often demonstrate intermediate- to hypointense signal on T1-weighted images (both similar to cartilage) and a combination of bone marrow edema together with intermediate signal on T2weighted images with fat saturation [8]. Fibrous TCs on the other hand, will often display hypointense signal on both T1- and T2-weighted images. Specificity in discriminating cartilaginous from fibrous TCs may be limited, though (as is the case with other modalities). Some therefore proclaim to merely aim to discriminate between a non-osseous or osseous TC [8]. In CNC, MRI, may demonstrate a hypointense band (Figure 4, panel B, middle images) between the calcaneus and navicular bone with an irregular surface of the articulating bones and adjacent bone edema on sagittal T1-weighted sequences (Figure 4, panel B, middle images). On the T2-weighted sequences with fat suppression Figure 4, panel B, image on the right), a hypointense band at the site of the CNC is seen with accompanied adjacent bone marrow edema. The hypointense signal on both the sequences is consistent with a fibrous CNC (Figure 4, panel B). Performance of MRI in TCs is often described as very effective, with generally excellent sensitivity. Although radiology can identify bony coalitions (plain radiographs, CT) and cartilaginous and fibrous coalitions (MRI), pinpointing the precise origin of pain complaints may be challenging [8, 13]. Moreover, in post-surgical TCs including metallic implants, use of MRI is often limited due to image distortion, signal loss and misregistration [14].

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