134 Part I Chapter 5 Non-osseous talocalcaneal coalitions (TCC) In order to optimally visualize the joint space and the structures immediately adjacent after plain radiographs, combining bone-SPECT/CT with arthrography (ArthroSPECT/CT) may be helpful [Figure 11 panel A]. Additionally, the amount of increased bone-turnover can be measured semi-quantitatively, either to assess severity or for intrapatient follow-up [22-24]. A small number of studies also evaluated quantitative bone-SPECT/CT parameters, such as SUVmax, in benign bone diseases other than TCs, for example in osteoarthritis of the knee, and in epiphyseal growth plates [23, 25]. In these studies, the SUVmax of quantitative bone-SPECT/CT was highly correlated with traditional imaging parameters for severity of medial compartment osteoarthritis in the knee. Analogous to these findings, we incorporated quantification in boneSPECT/CT in order to contribute to the limited evidence for feasibility and usefulness of this technique in TCs. on pre-operative bone-SPECT/CT if dedicated reconstruction algorithms are available [Figure 11 panel B] and subsequently in order to objectify comparison to post-surgery. Semi-quantitatively, change of the maximum standardized uptake value (SUVmax) at the site of the coalition increased from initial value of 12.8 to SUVmax 20.8 (Figure 11 panel B; post-operative SUV-measurement not shown). 3-D reconstructions with maximum intensity projections (MIP) may be helpful to inform the clinician [Figure 11 panel C]. Partly ossified TCC As already demonstrated in Figure 2, lateral plain radiographs demonstrating a C-sign (blue arrows) are suggestive of TCC. Subsequent bone-SPECT/CT images in Figure 2 show partially fused TCC (posterior facet) with increased uptake in the nonfused area, indicating the likely pain generator region. Bone-SPECT/CT adequately combines the ability to anatomically depict a partly ossified TCC as well as localizing the increased bone turnover, and thus pinpointing the site of pain generation at the non-fused area in a patient with partially ossified TCC. For clinical management this means that the patient could benefit from surgery in order to become pain free. Completely ossified TCC Also in this entity, first indication of completely ossified TCC will consist of the C-sign on plain radiographs, no bone edema on MRI as well as normal bone turnover on bone-SPECT/CT at the site of a completely ossified TCC. Also in these cases, MRI might especially detect soft tissue changes and bone-SPECT/CT is able to confidently exclude pain generation from the completely ossified TCC and to either exclude or pinpoint other (especially osseous) causes of pain.