Paper 24: Reliability of Posterior Tibial Slope Measurement on Magnetic Resonance Imaging Versus Computed Tomography

Objectives: Increased posterior tibial slope (PTS) has been linked to higher rates of anterior cruciate ligament (ACL) injury and ACL graft failure post-reconstruction. In recent years, more specific investigations have delineated distinct roles the medial plateau (MTP) lateral (LTP) geometries on anteroposterior rotatory stability knee. While diagnostic workup patients with insufficiency typically consists radiographs magnetic resonance imaging (MRI), computed tomography (CT), which is gold standard for evaluating osseous geometry proximal tibia, not routinely obtained. With increased understanding MTP LTP tibiofemoral kinematics, accurate sagittal measurements both will be crucial further defining treatment algorithm insufficiency. It currently unknown whether traditional MRI can used accurately measure PTS how well these correlate those CT. Therefore, purpose this study was compare versus Methods: After Institutional Review Board approval obtained, an institutional picture archiving communication system database retrospectively queried that received concurrent CT same knee within a one-year interval. Knees significant arthrosis (Kellgren-Lawrence grade >2), deformity, tibia fracture, or artifact obscured visualization landmarks were excluded. On paired studies, measured using previously described, validated method (Hudek et al, Clin Orthop Relat Res, 2009) by two independent raters (Figure 1). Interrater reliability assessed intraclass correlation coefficient (ICC). Intermethod agreement between ICC Bland-Altman analysis. Results: A total 41 knees in 40 (mean age, 37.9±13.4 78.0% male) met final inclusion criteria. moderate (ICC = 0.62-0.73) high 0.83-0.86). Mean at 3.3±2.8° (range, -4.7-8.4°) 3.7±3.1° -3.8-10.4°) CT, respectively. 4.5±3.8° -8.0-10.6°) 5.2±3.6° -3.6-15.7°) The mean absolute differences 2.6±2.1° 2.6±2.6° LTP, Poor intermethod observed 0.31-0.41), while 0.61-0.62). plots demonstrated variability minimal bias compared (-0.9° [95% Limit Agreement (LOA) -7.5-5.6°] MTP; -1.0° LOA -7.2-5.2°] LTP) 2). Conclusions: setting insufficiency, are necessary guide decisions. study, lower interrater Poor-to-moderate bias. may reliable MRI.