Finite element analysis and comparison of stress distribution in a varus knee joint specimen before and after virtual surgery

In a varus knee, the load balance on two sides of the knee joint is disturbed and the stress applied to the medial side of the joint will be greater than that of a healthy knee. The most common type of surgery to correct the deformity and balance the joint load is surgery called High Tibial Osteotomy.

In this study, a 3D model for a varus knee joint specimen was generated from MRI images. The second sample 3D model is prepared for the same joint after performing a virtual Closed Wedge Osteotomy. For the normal standing position, after loading and solving the problem, the stress distribution in the meniscus and the articular cartilage for both samples is obtained.

The results show that the maximum values of Von Mises stress and Contact Pressure for the varus knee are much higher than the corresponding values for the operated knee. The maximum contact pressure, under a 400 Newtons load applied to the upper end of the femoral head, was 7.821 MPa in the internal meniscus for the preoperative knee and 4.099 MPa for the operated knee in the external meniscus. Also, the maximum von Mises stress for before and after surgery was 6.501 and 3.488 MPa, respectively, both in the inner meniscus.

After simulation and finite elements analysis, the results of stress distribution showed that the stresses find a more suitable distribution after the operation and are closer to the values of a healthy knee.