Effects of Screw Materials in Anterior Cruciate Ligament Reconstruction using Finite Element Analysis

Abstract Interference screw fixation in Anterior Cruciate Ligament (ACL) reconstruction is a well known surgery to replace the damage or tear ligament of ACL with a graft made from tissue from other part of the body. The successive reconstruction and fixation strength is dependent on the bone quality and stability of the fixation as there is a potential damage to the graft due to screw threads. In this study, a finite element analysis is used to examine the effects of different screw materials in ACL reconstruction. The calculated mechanical behaviors are discussed with respect to the primary stability of screw fixation in ACL reconstruction. Three types of bio-absorbable materials are considered in the analysis namely poly-lactic acid (PLA), poly-lactic co-glycolic acid (PLGA) and poly-caprolactone (PCL). In addition, two metallic biomaterials are also included in the analyses which are titanium alloy and stainless steel. A 200 N tensile force is used as the loading condition directed on the interference screws at the femoral and tibial tunnels. It is the approximation of the graft tension at full extension during gait (level walking). Result shows that the maximum von-mises stress occurs on the interference screws are less than 40 MPa at the femoral and tibial fixation. A screw with stiffer material is identified to experience higher stress variation. The total displacement results show that the maximum displacements for all cases are less than 0.06 mm, which are small. The largest displacement is defined at less stiff material.