Anterior tibial subluxation measured under a modified protocol is positively correlated with posterior tibial slope: a comparative study of MRI measurement methods

Abstract

Purpose Anatomic factors, such as posterior tibial slope (PTS) and anterior tibial subluxation (ATS) obtained by quantitative measurement, have been proposed as predictors for clinical outcomes of anterior cruciate ligament (ACL) reconstruction. However, the correlation between PTS and ATS is controversial, and the method for quantitative ATS measurement remains unsettled. This study aimed to identify the correlation between PTS and ATS in patients with injured and intact ACLs and compare the two ATS measuring protocols. Methods This study included 128 ACL-injured and 176 ACL-intact patients with no concomitant ligament injuries. PTS and ATS were measured on sagittal MRI. ATS was measured using two measuring protocols, including the modiied protocol using the longitudinal tibial axis (axis protocol) and the established protocol using a line perpendicular to the tibial plateau (plateau protocol). Correlation analyses between PTS and ATS and between PTS and the diference in the ATS value measured under the two protocols (ATS dif ) were performed. The diference between the two ATS measuring protocols was further analyzed by trigonometric analysis. Intra-and interobserver reliability tests were performed for the axis protocol. Results Under the axis protocol, ATS was positively correlated with PTS in both the ACL-injured and ACL-intact groups (p < 0.001). Under the plateau protocol, no correlation was observed in the ACL-injured group. In the ACL-intact group, no correlation was observed for lateral ATS, and a negative correlation was observed for medial ATS (p = 0.001). ATS dif was positively correlated with PTS (p < 0.001), indicating that the two protocols varied greatly in those with a steep PTS. Trigonometric analysis showed that a steep PTS inluenced the measurement of ATS under the plateau protocol but not the axis protocol. Intra-and interobserver reliability tests showed good-to-excellent strength of reliability for the ATS measurement under the axis protocol. Conclusion ATS measured under the axis protocol was positively correlated with PTS, indicating that a steep PTS was associated with a worse anatomic tibiofemoral relationship. The axis protocol for ATS measurement is a promising method for clinical use since it is not inluenced by PTS and relects the global position of the tibia. Level of evidence III.

Association of Concomitant MRI-Determined Anterolateral Complex Injury With Quantitative Measurements of Altered Rotational Tibiofemoral Position on MRI in Patients With ACL Injury

“…Several confounding factors—such as concomitant meniscal injuries, a long injury-to-MRI time, 14 , 25 , 26 and steep PTS 24 —could also have affected the results. To control for these variables, we only included nonchronic ACL-injured patients with an injury-to-MRI time of <3 months.…”

“…On sagittal T1WIs, measurement of anterior tibial subluxation (ATS) in the lateral and medial compartments (LATS and MATS) was performed according to previous studies, 23 - 25 using the LTA 8 as the reference line ( Figure 1, B and C ).…”

Association Between Anterior Tibial Subluxation of Lateral Compartment and High-Grade Knee Laxity in Patients With Anterior Cruciate Ligament Deficiency

“…Recently, magnetic resonance imaging (MRI) was introduced to measure the ATS of medial and lateral compartments (ATSMC and ATSLC, respectively) separately and showed satisfactory interobserver and intraobserver consistencies. 24,25,34,49 Furthermore, some risk factors related to high-grade knee laxity, including chronic injury, meniscal tear, injured ALL, chondral defect, and steep PITS, have been validated as predictive risk factors of excessive ATSMC or ATSLC, 34,40,45,53,55 similarly leading to increased graft failure and inferior knee stability after ACLR. 16,46,56…”