Biomechanical study of a new locking plate model: locking screws behavior in bending assays compared to non-locking screws. comparison of the holding force of the screw in the plate hole, of plates with a standard holes and plates of the PACS system

• Grant number: 11/07303-3
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2012
• End date: January 31, 2014
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Clinics and Surgery
• Principal Investigator: Cassio Ricardo Auada Ferrigno
• Grantee: Cassio Ricardo Auada Ferrigno
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The technological advancements of materials used in osteossynthesis increases in great speed. One of the most recent devices is the locking plate, its main indications are fractures with a great degree of comminution, fractures that don't require anatomical reduction, osteopenic bones caused by, for instance, osteoporosis, among others. The locking plate is a rigid system that doesn't allow movement between its components (plate - bone - screw), providing extreme stability and rigidity to the system. The screw head and the plate holes have threads that lock the components, and due to this characteristic, a perfect contouring of the plate to the bone isn't necessary. Nowadays new locking plate models are being developed, where the screw and plate interface is made by the deformation of the hole, with the advantage of screw installation in any angle. In this project we will compare the difference between both types of screw-plate interface, as well as study the use of regular screws in a new locking device. Therefore destructive assays will be made with a model of application of a pure axial load in 20 standard locking screws (male and female threads) and 20 screws of the new locking model (hole deformation). The 2.4mm, 2.7mm and 3.5mm systems of both types of locking screws will be studied, and the rigidity of conventional screws (without head threads) will be compared to locking screws in a bending assay, in plates with the new locking system. (AU)