Aim: 99mTc-biphosphonate (99mTc-DPD) bone scintigraphy with single photon emission tomography coupled with computed tomography (SPECT/CT) plays an important role in orthopaedic and traumatological clinical investigations as it enables to detect and precisely locate subtle lesions with increased bone turnover in bones and joints (1,2). Nowadays, it has become possible to quantify osteoblastic activity in lesions by precisely measuring their 99mTc- DPD uptake (3). This study aims at understanding whether quantification parameters correlate with patient’s clinical outcomes (symptomatology and treatment) of osteochondral lesions of the talus (OLTs). A secondary aim was to correlate quantitative SPECT parameters with MRI results.
Method: We retrospectively identified 28 patients that underwent a quantitative bone SPECT/CT with OLTs between 2016 and 2022. SPECT/CT parameters were retrieved, namely standard uptake value (SUV) measurements: SUVmean, SUVmax, SUVpeak, SUVpeak/SUVmeanTibia, SUVmax/SUVmeanTibia, total lesion glycolysis (TLG) and metabolic tumour volume (MTV) values. Magnetic resonance imaging (MRI) parameters were also analysed when available, namely lesion type (chondral or osteochondral), presence and size of intraarticular fragments, size and surface of lesions, presence or absence of articular effusion and size of talar bone oedema. Patient’s symptomatology (positive or negative) and intervention (no intervention, conservative or surgery) was retrieved from their electronic record. Clinical data was then correlated to imagery values. SPECT/CT and MRI measurements were also correlated with each other.
Results: No statistically significant correlations were established between SPECT/CT measurements (SUVmean, SUVmax, SUVpeak, SUVpeak/SUVmeanTibia, SUVmax/SUVmeanTibia, TLG, MTV, lesion sizes) and patient’s outcome (symptomatology or treatment). MRI lesion depth (in millimetres) is positively correlated with two SPECT/CT parameters (SUVmax/SUVmeanTibia and SUVpeak/SUVmeanTibia) (r= 0.50, p<0.05). MTV was significantly higher in patients with a free intraarticular fragment seen on MRI (p=0,049), and MTV positively correlated with the size of the intraarticular fragment (r= 0.46, p<0.05). TLG was higher in patients with articular effusion (p<0.05). No correlation was found between quantitative parameters and the surface of the lesion or talar oedema on MRI.
Conclusion: Within our group of 28 patients, some had asymptomatic OLT that were detected incidentally, others suffered from fracture-related OLT, and a few presented OLTs of unknown origin, showing the heterogeneity of the group. Along with this, not all patients were clinically followed following their SPECT/CT imaging. The heterogeneity of the study and the relative low sample probably contributed to the absence of significant correlations between SPECT/CT parameters and clinical outcomes, indicating the need of further prospective studies. When correlating quantitative SPECT parameters with MRI results, our study showed that MTV is correlated to the presence and the size of intraarticular fragments visualised on MRI. The depth of the lesion on MRI and the presence of articular effusion are also positively correlated to the intensity of the osteoblastic activity. Therefore, quantitative SPECT/CT parameters measuring osteoblastic activity seem to increase in the presence of known MRI criteria of lesion severity, indicating a potential role in the pathophysiology of osteochondral lesions of the talus.