Evaluation of a novel lower radiation computed tomography protocol for assessment of tunnel position post anterior cruciate ligament reconstruction

BACKGROUND: Anterior cruciate ligament (ACL) reconstruction is a common orthopaedic procedure. We developed a novel, low dose computed tomography (LDCT) protocol to assess tunnel position post-operatively. The effective radiation dose of this protocol is < 0.5millisieverts (mSv), which is significantly less than the 2 mSv dose for a conventional CT protocol. The aim of this study was to assess the accuracy of the LDCT protocol for determining tunnel position. METHODS: Twenty-six patients who underwent primary ACL reconstruction were included in the study. A LDCT scan was performed 6 weeks post-operatively. Femoral and tibial tunnel positions were measured on three dimensional (3D) reconstructions using previously validated techniques. Measurements were performed independently by three observers at two time points, 4 weeks apart. RESULTS: There was excellent intra- and inter-rater reliability for all measurements using the images obtained from the LDCT protocol. Intra-class correlation coefficient (ICC) values were > 0.9 for all measurements. CONCLUSIONS: The LDCT protocol described in this study accurately demonstrates femoral and tibial tunnels post ACL reconstruction, while exposing the patient to a quarter of the radiation dose of a conventional CT. This protocol could be used by orthopaedic surgeons for routine post-operative imaging, in place of plain film radiographs.