Eduard Mitroi, Daniel Vlasceanu Applicability of Self-reinforced Polylactic Acid in Humeral Transcondylar Osteosynthesis

Eduard Mitroi, Daniel Vlasceanu Applicability of Self-reinforced Polylactic Acid in Humeral Transcondylar Osteosynthesis

Abstract:
The emergence of self reinforced polymers relaunched the osteosynthesis with resorbable materials, especially in the case of the long bone ends fractures. The improved mechanical resistance and the slow resorbtion are the main advantages compared with previous generations of bioresorbable materials. These qualities prompted us to conduct this study, which focuses on assessing the strength of new implants made of self reinforced polylactic acid (SR-PLA). The implants are designed for osteosynthesis of transcondylar fractures, one of the most common types of distal humerus fractures. Our innovation in terms of implants is to amend a malleolar bone screw so that it can be locked with a Kirschner wire or a thin screw. Thus, an assembly consisting of two screws of this type and a locking wire significantly increases the contact surface between the fragile epiphyseal bone and the implant. The study uses the finite element method and simulates the postoperative loading conditions of the bone-implant assembly. Two CAD models were created representing a stable and an unstable fracture fixed with these implants having the properties of SR-PLA. The models were imported, edited and analyzed in a state of the art finite element program. The evaluation of the interfragmentary displacements, normal stresses in bone and equivalent stresses in implants shows that the osteosynthesis of the stable fracture successfully bears the loads imposed on the entire arc of flexion-extension, while the unstable fracture fixation is fragile at the extremes of the range of motion. The weak point of both assemblies is the metaphyseal cancellous bone. For both models the screws made of SR-PLA held up very well in the given circumstances: the equivalent stresses were low relative to material mechanical resistance. SR-PLA appears as a suitable material for this type of osteosynthesis, but additional biomechanical studies are needed to confirm these results. Keywords: self-reinforced polylactic acid, transcondylar fracture, finite element analysis

Issue: 2014 Volume 51, Issue 4

Pages:

Publication date: 2014/12/30