Knees with Smaller Posterior Tibial Slope And More Concave Medial Tibial Plateau Are At Higher Risk Of Isolated Meniscal Injuries. Issue 7 (31st July 2020) - Murray, Martha
Objectives: Meniscal injuries are extremely common. Several anatomical features of the knee, including the tibial plateau morphology, have been shown to influence knee biomechanics and the risk of ligamentous injuries. Little is known, however, how these morphological features influence the risk of isolated meniscal injuries in the ACL intact knee. In the current study, we used MRI and 3D image analysis to investigate anatomical variables of knees in patients with and without isolated meniscus tears. We hypothesized that there are differences in slopes and concavity of the tibial plateau between patients with isolated meniscus tears and matched normal controls. Methods: 65 subjects with first-instance isolated medial or lateral meniscal injuries requiring surgical fixation (Age: 15 +/- 2 years, BMI: 23.2 +/- 3.7 Kg/m2; 43% females) were matched to 65 subjects with normal knees and no prior injuries (Age: 15 +/- 2 years, BMI: 23.1 +/- 3.8 Kg/m2; 43% females) based on age, BMI and sex. Sagittal Proton Density SPACE MR images (preoperative for injured group) were used to measure the posterior slope of the medial (MTS) and lateral (LTS) tibial plateau, coronal slope of the tibial plateau (CTS), and the maximum depth of the medial tibia plateau (MTD, as a measure of medial tibial plateau concavity), following established techniques-Figure 1. Two-sample t-test was used to compare the quantified anatomical features between the cases and matched controls. Results: There were no differences in age (p = 0.999), sex distribution (p = 0.999) and BMI (p = 0.963) between the two cohorts. Compared to matched controls, patients with isolated meniscal tears had lower LTS (3.6 +/- 3.2 vs 5.6 +/- 3.0 degrees; p < 0.001), lower MTS (3.4 +/- 2.9 vs 4.9 +/- 2.5 degrees; p = 0.001) and deeper MTD (2.4 +/- 0.8 vs 1.5 +/- 0.8 mm; p < 0.001). There was no difference in CTS between the groups (3.6 +/- 1.6 vs 3.9 +/- 2.2 degrees; p = 0.300). Conclusion: This study suggests that subjects with isolated meniscus tear have a lower posterior tibial slope and a deeper MTD (more concave medial tibial plateau) than matched population who do not have a meniscus tear. This is contrary to what is known for ACL tears, where a higher posterior tibial slope and a shallower MTD have been associated with an increased risk of ACL tear. During load-bearing activities, in particular high impact movements such as jumping, increased tibial slope and decreased MTD have shown to result in greater anterior shear forces across the knee. In contrast, the less sloped and more concave plateau will experience lower shear forces but more compression, which could be detrimental to the meniscus. This study provides preliminary evidence suggesting a link between tibial plateau morphology and risk of isolated meniscal injuries. Further mechanistic studies are required to better understand the interaction between knee morphology, meniscal loading and subsequent risk of injury. Figure 1.