Evaluation of the incorporation of bone grafts used in maxillofacial surgery with [18F]fluoride ion and dynamic positron emission tomography

This study investigates the incorporation of bone grafts used in maxillofacial surgery by means of [¹⁸F]fluoride ion and positron emission tomography (PET). It considers patients who received pedicle grafts for mandibular reconstruction or onlay grafts for alveolar ridge augmentation. Dynamic PET images and arterialized venous blood samples were obtained within a 1-h period after i.v. injection of [¹⁸F-]fluoride. Assuming a three-compartment model and applying multilinear least squares fitting, bone blood flow (K₁) and fluoride influx (K_mlf) were determined. Additionally Patlak plot analysis was used to calculate fluoride influx (K_pat). In cervical vertebral bodies as the reference region, mean values for flow ofK₁ = 0.1162±0.0396 ml/min/ml and influx ofK_mlf = 0.0508±0.0193 andK_pat = 0.0385±0.0102 ml/min/ml were found. Essentially these figures are comparable with physiological values in animal and man reported in the literature. Early after surgery a significant increase in flow and influx compared to vertebral bodies was observed in the regions of osteosyntheses between grafts used for reconstruction and recipient bone (K₁ = 0.2181,K_mlf = 0.1000 andK_pat = 0.0666 ml/min/ml) and in onlay grafts (K₁ = 0.2842,K_mlf = 0.1637 andK_pat = 0.0827 ml/min/ml). At the same time pedicle grafts showed a significant increase in flow but not in influx (K₁ = 0.2042,K_mlf = 0.0774 andK_pat = 0.0529 ml/ min/ml). FurthermoreK_pat was significantly lower in pedicle grafts than in onlay grafts. In follow-up studies a significant decrease in flow occurred in pedicle grafts and the regions of osteosyntheses. Moreover the latter showed a significant decrease inK_mlf as well. It is concluded that [¹⁸F-] PET depicted increased blood flow and osteoblastic activity in onlay grafts and regions of osteosyntheses, indicating bone repair in the graft and adjacent host bone early after surgery. For the regions of osteosyntheses the decrease in both parameters corresponded to uncomplicated healing. The lack of increased influx, although flow was increased in pedicle grafts, most likely indicates that some necrosis occurred in these grafts despite patency of anastomoses. It may be concluded that [¹⁸F-] PET provides further insight into the biology of graft incorporation.