Design of Fracture Fixation Plate for Necessary and Sufficient Bone Stress Shielding

Abstract

The objective of treating the fractured bone is to achieve painless functioning of the bone and undisturbed healing at the fracture. Internal fixation by stiff bone-plate is one of the standard methods to achieve these objectives. Recently, there is considerable interest in the usage of compliant plates to enhance bone healing with reduced stress shielding. Herein, first an analytical solution is developed to determine screw forces in the bone-plate assembly that conforms the plate and the bone under bending load. Based on the analytical calculations, an optimal fixator plate selection criterion for necessary and sufficient stress shielding is proposed. Second, effectiveness of employing a non-homogeneous stiffness graded (SG) plate rather than a homogeneous stainless steel (SS) plate for stress shielding is investigated using a finite element method. It is found that stress shielding on bone by SG plate is less compared to SS plate.

Effects of the bone-plate material and the presence of a gap between the fractured bone and plate on the predicted stresses at the fractured bone

“…At the 50% healed level, as additional callus is generated at the fracture interface, the callus bone becomes able to take on the compressive stress. At this stage, the callus modulus is assumed to be 10 GPa (500 times larger than its value in the first week) [5]. The bone and plate behave as a composite plate, causing the stress at the fracture site to increase and shifting the neutral axis towards the bone domain.…”

“…The plate and screw internal fixation technique has been improved with the presence of new biocompatible rigid materials such as stainless steel, cobalt chromium, titanium and composite materials [2][3][4][5][6][7][8][9]. However, bone osteoporosis is often found under these rigid plates, and bone re-fracture may occur after the plate is removed.…”

“…Therefore, using a high modulus bone-plate for fractured bone fixation will lead to a reduction of bone density and cause bone osteoporosis as a long-term effect. This problem can be eliminated by using low stiffness bone-plates [5,8].…”

“…Ramakrishna et al [5,8] used stiffness-graded material as a bone-plate for long bone fracture fixation. Their 2D finite element simulation results indicated that using a contacted FG material as a bone-plate offers less stress shielding to the bone and provides higher compressive stress at the fracture interface.…”

Design optimization of a xenogeneic bone plate and screws using the Taguchi and finite element methods

“…1 and the type, number, and placement of the bone screws are considered as design factors. 13,19,20 In the current study, we analyzed the thickness, width, and length of the bone plate and the effective diameter and type of bone screws as the design factors influencing fractured bone fusion. Additionally, the size of an implant inserted in a body is very important, as it greatly influences the operation time, the suturing convenience of the incised site, and the amount of bleeding during the operation.…”