Different radiological approaches to preoperative estimation of implant stability in vertebral bodies

The present investigation studied whether or not ventral derotation spondylodesis (VDS) screw fixation strength can be estimated preoperatively by means of radiology. Furthermore, comparison of the techniques applied was done to show which of them is most appropriate. The bone mineral density of human cadaveric lumbovertebral bodies was assessed by both dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). Trabecular structure was characterised by T2*-relaxation time magnetic resonance imaging (MRI). After ventral instrumentation of vertebral bodies with VDS screws, their axial pullout force was assessed as a reference value for initial stability of the implant. Data from each radiological method were correlated with it. The highest correlation with pullout force was registered for density of cancellous bone by QCT (r = 0.72; P > 0.001), immediately followed by DXA (r = 0.70; P < 0.001). T2*-relaxation time (MRI) correlated moderately (r = 0.55), whereas cortical bone density (QCT) showed a negligible correlation (r = 0.2). Results reveal that absorptiometrical techniques like DXA and QCT (cancellous bone) are the most appropriate ones to assess initial screw fixation strength in vertebral bodies preoperatively.