Lateral–medial asymmetry of posterior tibial slope and small lateral tibial plateau articular surface depth are morphological factors of lateral meniscus posterior root tears in ACL-injured patients

Abstract

Purpose To investigate whether knee morphological features, patient characteristics, and intraoperative indings are associated with a lateral meniscus (LM) posterior root tear (LMPRT) in anterior cruciate ligament (ACL) injuries with the integrated data from two academic centres. Methods This retrospective study used registry data acquired prospectively at two academic centres. Patients with ACL reconstruction (ACLR) with LMPRT and no other LM injury were selected (LMPRT group) from each database. The control group included patients who underwent ACLR without LM tears. Patients were matched to the LMPRT group according to age and gender (1:1). Morphological factors evaluated on preoperative magnetic resonance image scans included lateral femoral condyle (LFC) anterior-posterior diameter, height, and depth; lateral tibial plateau (LTP) articular surface (AS) depth and sagittal plane depth; and lateral and medial posterior tibial slopes (PTSs). LFC height and depth ratios, LTP AS depth and sagittal plane depth ratios, and lateral-to-medial slope asymmetry were computed from previous measurements. Patient characteristics and intraoperative indings were extracted and compared between both groups. ResultsThe study included 252 patients (126 in each group). The lateral-medial asymmetry of PTS was greater in the LMPRT group (1.2° vs 0.3°, p < 0.05), and the LTP AS depth was smaller in the LMPRT group (31.4 mm vs 33.2 mm, p < 0.01). There were no diferences in LFC morphology between the control and LMPRT groups. Pivot shift grade (p < 0.05), percentage of complete ACL tears (p < 0.05), and medial meniscus ramp lesions (p < 0.05) were signiicantly higher in the LMPRT group. Conclusion LMPRT was associated with signiicantly increased lateral-medial asymmetry of PTS and signiicantly smaller LTP AS depth. LMPRT was also associated with an increase in the preoperative pivot shift grade and the presence of a medial meniscus ramp lesion. These morphological characteristics are rather simple to measure and would serve as helpful indicators to preoperatively detect LMPRT, which is frequently challenging to diagnose preoperatively. Level of evidence Level III. KeywordsLateral meniscus posterior root tear • ACL injury • Posterior tibial slope • Lateral tibial plateau articular surface depth * Hideyuki Koga

Investigation of the anatomic risk factors in acute anterior cruciate ligament ruptures to develop ramp lesions of the medial meniscus by quantitative MRI

“…First, we investigated several anatomic factors reported in previous studies including the lateral and medial posterior tibial slope (LPTS and MPTS), the asymmetry of LMPTS, medial and lateral meniscal slope (MMS and, LMS) and medial femoral condyle (MFC). LPTS has been extensively inspected as a potential risk factor for non-contact ACL injuries [ 19 , 23 , 24 , 29 ], but few studies have assessed whether it is related to ramp lesions. A cross-sectional study has indicated that the LPTS and the asymmetry of LMPTS were risk factors for ramp lesions in ACL-injured knees [ 12 ], while another study reported no correlation between LPTS and ramp lesions [ 22 ].…”

“…When the ACL ruptures, the compressive forces result in an anteriorly directed shear force, eventually leading to anterior translation and internal rotation of the tibia, posterior rolling of the LFC, and anterior rolling of the MFC, relatively [ 2 , 29 , 35 , 36 ]. According to previous studies, a steeper LPTS and a higher asymmetry of LMPTS could further increase anterior translation and internal rotation of the tibia.…”

“…3b , d ), and the asymmetry of the LPTS and MPTS (LMPTS) was defined as LPTS minus MPTS. The measurement of the MTP anterior-to-posterior length (MTP AP length) was adapted and employed in this study by Yoshihara et al [ 29 ] at the central sagittal MRI slice of the MTP (Fig. 3 g ).…”

“…For the parameters of femoral condyle, the diameter of the medial femoral condyle (MFC) was assessed at the central sagittal plane, following the method described by Yoshihara et al (Fig. 3f, g ) [ 29 ]. This involved the following steps: (1) drawing two circles that were tangential to the cortex in the femoral shaft on the mid-sagittal MRI; subsequently, the femoral longitudinal axis was established by connecting the midpoints of these two circles.…”