Assessment of the viability of microvascularized bone grafts after mandibular reconstruction by means of bone SPET and semiquantitative analysis

The purpose of this study was to investigate the value of bone scintigraphy including single-photon emission tomography (SPET) and semiquantitative an alysis for the assessment of graft viability following microvascularized bo ne transplantation. We evaluated 60 scintigraphic studies of 36 patients wi th 39 bone grafts. Thirty-four investigations were performed 6-11 days (ear ly bone scans) and 26 up to ii months (late bone scans) after mandibular re construction. After administration of 550 MBq technetium-99m methylene diph osphonate, planar scintigrams and a SPET study were performed. The data wer e reconstructed iteratively. Scans were evaluated visually and semiquantita tively by a region of interest technique using the ratio between transplant and cranium (T/C). Patients with uncomplicated healing showed a T/C ratio >1.0 in early and late bone scans. In cases with necrosis, the T/C ratio wa s below 1.0 when performing early bone scans. However, in late bone scans, some patients with necrosis showed a slightly increased uptake and a TIC ra tio >1.0. The data demonstrate that as early as 6-11 days after mandibular reconstruction, increased tracer uptake proves that the surgery has been su ccessful and indicates a normal healing process. Especially in the early bo ne scans no false-positive or false-negative results were observed and the T/C ratio clearly differentiated between vital and non-vital bone grafts. A t later times false-positive findings could be observed; these were, howeve r, rare because of the significantly higher tracer uptake of the healthy gr afts when compared with completely or partially necrotic transplants.