Biomechanical effect of tibial slope on the stability of medial unicompartmental knee arthroplasty in posterior cruciate ligament-deficient knees

Abstract

Aims Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA. Methods Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition. Results As compared to intact UKA, there was no significant difference in AP translation in PCL-deficient UKA with a low flexion angle, but AP translation significantly increased in the PCL-deficient UKA with high flexion angles. Additionally, the increased AP translation became decreased as the posterior tibial slope increased. The contact stress in the PF joint and the articular cartilage significantly increased in the PCL-deficient UKA, as compared to the intact UKA. Additionally, the increased posterior tibial slope resulted in a significant decrease in the contact stress on PF joint but significantly increased the contact stresses on the articular cartilage. Conclusion Our results showed that the posterior stability for low flexion activities in PCL-deficient UKA remained unaffected; however, the posterior stability for high flexion activities was affected. This indicates that a functional PCL is required to ensure normal stability in UKA. Additionally, posterior stability and PF joint may reduce the overall risk of progressive OA by increasing the posterior tibial slope. However, the excessive posterior tibial slope must be avoided. Cite this article: Bone Joint Res 2020;9(9):593–600.

Computational analysis of tibial slope adjustment with fixed-bearing medial unicompartmental knee arthroplasty in ACL- and PCL-deficient models

“…Furthermore, our previous study indicated that the PCL is crucial to restraining AP translation, by showing a significant difference in the amount of translation between the PCL deficiency and the intact knee in UKA. 15 Defrate et al 37 demonstrated that ACL deficiency alters AP translation, and the difference between the translation of the ACL-deficient knee and the intact knee was more pronounced near full extension. In particular, the ACL has the functionally important role of restricting anterior tibial translations in the medial UKA.…”

“… 14 In addition to performing these evaluations, we researched the effects of posterior tibial slope in posterior cruciate ligament (PCL)-deficient patients in a previous study. 15 However, no studies have compared the effects in ACL-deficient and PCL-deficient knee models.…”

Anterior cruciate ligament injury should not be considered a contraindication for medial unicompartmental knee arthroplasty: Finite element analysis

“…The researchers concluded that a fixed-bearing UKA with a 5–8° posterior tibial slope adjustment can partially compensate for the lack of ACL function and can be a feasible treatment option for ACLD patients. Furthermore, it can maintain a higher average survival period in their study [ 32 – 34 ]. These findings also explain why the contact structure stress in the knee joint does not show significant changes when the ACL is missing but the other knee ligaments are intact under rotational loads.…”

Editorial Commentary: Posterior Tibial Slope: The “Unknown Size” of the Knee Joint

“…Given the growing awareness of the importance of bony morphology in reconstructive knee surgery and total knee arthroplasty (TKA), many efforts have been made in recent years to increase the knowledge of the role of PTS. 2,5,6 In the case of the PTS, similar to the question of alignment in TKA, it is absolutely necessary to take a step back and first define the goal and insist on uniform reporting. We are still unclear what the real "true PTS" is.…”