Knee valgus deformity and lateral bone defects affect the function of superficial medial collateral ligament: A finite element analysis

Purpose: The superficial medial collateral ligament (sMCL) is the primary restraint to valgus laxity of the knee, which is one of the significant indicators of implant selection in valgus knee. Our purpose is to explore the in-fluence of knee valgus deformity and lateral bone defects in the function of sMCL. Methods: the right knee joint of a healthy male volunteer was subjected to CT and MRI scans. The scanned data were imported into Mimics, Geomagic, Solidworks and Ansys software to establish a three-dimensional finite element model of the human knee joint. Femorotibial angle (FTA)5 degrees,10 degrees,15 degrees,20 degrees,25 degrees,30 degrees,35 degrees and lateral bone defect 0,0.5,1,1.5,2 cm are controlled in Solidworks. Tensile test in vitro of maximum load on sMCL was simulated in Ansys. Results: The peak stress of sMCL is raising with valgus deformity while there is no lateral defect. Increasing lateral bone defect can lessen the augmentation of the stress of sMCL caused by the valgus deformity. The peak stress of sMCL when it is in maximum load is 35.252 MPa. While valgus 35 degrees, the peak stress of sMCL exceeds the value, with or without bone defect; the same is true for the valgus 30 degrees with 0, 0.5, 1 cm bone defect and valgus 25 degrees without defect. Conclusion: Our findings allow for preoperative evaluation of sMCL function in the valgus knee, which would play an instructive role to some extent for implant selection in total knee arthroplasty.