Diagnostic value of single-photon emission computed tomography combined with computed tomography in relation to MRI on osteochondral lesions of the talus.

Background: Osteochondral lesion of the talus (OLT) involves the separation of a fragment of articular cartilage, as defined by Kappis in 1922. MRI is the current standard for noninvasive diagnosis of OLT. Single-photon emission computed tomography combined with computed tomography (SPECT/CT) provides both morphologic and functional information. The purpose of the study was to compare SPECT/CT with MRI for image interpretation and treatment decision making in talar osteochondral lesions.

Materials And Methods: A total of 21 patients (four bilateral) were evaluated with MRI and SPECT/CT. Diagnostic arthroscopy was performed to validate the indication by identifying unstable cartilage areas. Activation was assessed in nine regions of interest, as described by Elias and colleagues. SPECT/CT findings were assessed by the modified scoring system of Hart and colleagues, and MRI findings with the modified classification system of Hepple and colleagues. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for SPECT/CT and MRI.

Results: A total of 25 lesions were identified. Seventeen lesions were located on the medial third of the talar dome, eight on the lateral third, and seven on the central third. Four patients revealed diffuse uptake on more than one zone on SPECT/CT. SPECT/CT identified two subchondral lesions, which were not visualized on MRI.

Conclusion: MRI is the current standard for OLT diagnosis. SPECT/CT allows a three-dimensional localization of scintigraphic osteoblastic activity in the area of interest, providing additional information about the involvement of the subchondral bone and the vitality of the osteochondral lesion and the location of multiple lesions. We recommend the use of SPECT/CT and MRI together for comprehensive diagnostic assessment of OLT.