DIFFERENT RADIOLOGICAL APPROACHES TO PREOPERATIVE ESTIMATION OF IMPLANT STABILITY IN VERTEBRAL BODIES

The present investigation studied whether or not ventral derotation sp ondylodesis (VDS) screw fixation strength can be estimated preoperativ ely by means of radiology. Furthermore? comparison of the techniques a pplied was done to show which of them is most appropriate. The bone mi neral density of human cadaveric lumbovertebral bodies was assessed by both dual-energy Xray absorptiometry (DXA) and quantitative computed tomography (QCT). Trabecular structure was characterised by T-2-relax ation time magnetic resonance imaging (MRI). After ventral instrumenta tion of vertebral bodies with VDS screws, their axial pullout force wa s assessed as a reference value for initial stability of the implant. Data from each radiological method were correlated with it. The highes t correlation with pullout force was registered for density of cancell ous bone by QCT (r = 0.72; P > 0.001), immediately followed by DXA (r = 0.70; P < 0.001). T-2-relaxation time (MRI) correlated moderately ( r = 0.55), whereas cortical bone density (QCT) showed a negligible cor relation (r = 0.2). Results reveal that absorptiometrical techniques l ike DXA and QCT (cancellous bone) are the most appropriate ones to ass ess initial screw fixation strength in vertebral bodies preoperatively .