Does posterior tibial slope laterality exist? A matched cohort study between ACL-injured and non-injured knees

Purpose The purpose of this study is to examine 1) the degree and frequency of laterality in posterior tibial slope (PTS) with control and anterior cruciate ligament (ACL) injury groups and 2) the laterality of PTS between sides of injury and dominant legs in patients with primary ACL injuries.Methods A total of 187 consecutive patients with clinically diagnosed noncontact ACL injuries and an age- and sex-matched 1:1 control group were identified. PTS was measured using three different methods (aPTS = anterior PTS, mPTS = middle PTS, pPTS = posterior PTS) on a lateral knee radiograph. PTS of the left and right sides were compared between the patients in the control and ACL-injured groups, and between the injured and non-injured and dominant and non-dominant legs among the patients in the ACL-injured group. The patients with a difference in PTS of >= 3 degrees in mPTS were selected. The percentages were compared between left and right between and among both groups, and between the injured and non-injured, and non-dominant and dominant leg, for the ACL group. Multiple regression analysis was performed to analyze the factors influencing the degree of mPTS.Results Both control (Right vs Left: aPTS; 9.0 +/- 2.5 vs 10.5 +/- 3.0, mPTS; 6.6 +/- 2.3 vs 8.1 +/- 2.7, pPTS; 4.0 +/- 2.4 vs 5.6 +/- 2.8, respectively, p < 0.01) and ACL injury groups (Right vs Left: aPTS; 10.6 +/- 3.0 vs 12.6 +/- 2.9, mPTS; 7.6 +/- 2.6 vs 9.5 +/- 2.6, pPTS; 5.9 +/- 3.0 vs 8.0 +/- 3.0, respectively, p < 0.01) had a significantly greater PTS on the left than on the right side, and the ACL group had a significantly greater PTS than the control group on both the left and right sides. In the ACL group, PTS was greater on the injured and the non-dominant leg than on the non-injured and the dominant leg. The percentage of patients with a PTS difference of >= 3 degrees was significantly greater on the left, injured, and non-dominant leg (95.3% vs 4.7%, 73.8% vs 26.2%, 86.1% vs 13.9%, respectively, p < 0.01). Only the left leg had a significant influence on PTS in the multivariate analysis.Conclusion There was laterality in PTS within control and ACL injury groups, and this information is of benefit for effective treatment of ACL injuries.