The tibial tubercle–trochlear groove (TTTG) distance is used to quantify the degree of lateralization of the patellar tendon insertion on the tibial tubercle relative to the deepest part of the trochlear groove. Disagreement exists as to whether the TTTG distance measured on computed tomography (CT) and magnetic resonance imaging (MRI) can be considered equivalent.
The purpose of this study is to compare TTTG distance as measured on axial CT and MRI and to investigate the potential effect of patient positioning between modalities. It was concluded that a systematic bias toward lower TTTG distances on MRI compared with CT was found. This finding is likely dependent on imaging technique, including patient positioning. Patient knees were positioned in varus on the MRI compared with the CT examination, with resulting lower TTTG distances on MRI compared with CT. The TTTG distances on CT and MRI vary with imaging technique, which may be attributable to patient positioning and result in differences among imaging centers.