V 48 SPECT-CT: A new imaging diagnostic tool for osteochondral lesions (OCL) of the talus-Comparison to MRI

Introduction Magnet resonance imaging (MRI) is the gold-standard of non-invasive diagnostics in OCL of the talus. Single photon emission computed tomography – computed tomography (SPECT-CT) shows additional, high-resolutioned information of osteoblastic (szintigraphic) activity and bony morphology. The study aimed for evaluating the influence of the SPECT-CT on clinical application of the imaging information and decision-making in OCL therapy. Methods MRI and SPECT-CT of 26 patients (average age: 32 y) were analyzed separately by 3 blinded, independent orthopaedic foot and ankle surgeons experienced in treating OCL and working with MRI and SPECT-CT for treatment decision-making. Imaging information was analyzed by using a specified questionnaire. Results By the SPECT-CT, a change in treatment was documented in 46 of 78 decisions (59%) in comparison to the MRI. Following treatment decisions were chosen most often (total decisions: 156): Retrograde drilling: 64 (41.0%); microfracture and antegrade drilling: 28 (17.9%); osteochondral autologous transplantation (mosaicplasty): 23 (14.8%); excision and debridement: 16 (10.3%); physiotherapy: 9 (5.8%); autologous chondrocyte implantation: 5 (3.2%); joint-sacrificing therapy (e.g. joint replacement): 5 (3.2%); cancellous bone grafting: 4 (2.6%); passive conservative therapy (e.g. cast): 1 (0.6%); drug therapy (e.g. hyaluronic acid): 1 (0.6%); refixation: 0 (0%). However, overall distribution of therapies remained unchanged between MRI and SPECT-CT. The questionnaire revealed main differences in imaging interpretation for: subchondral bone plate morphology (17; 65%), subchondral sclerosis (16; 62%), subchondral cysts (11; 42%), and kissing lesions (10; 38%). The area of szintigraphic activity in comparison to bone bruise was found to be smaller in 50% of cases (13) and bigger in 27% (7 cases). Discussion The additional information provided by the SPECT-CT influences the decision-making for the treatment of OCL in the talus significantly. This is due to changed interpretation of subchondral bone plate morphology and subchondral bone activity. No study reported on SPECT-CT in OCL yet. SPECT-CT may become important in diagnostics and treatment decision-making in OCL of the talus.