Publication Date

2008

Document Type

Thesis

Committee Members

Tarun Goswami (Advisor), Michael Prayson (Committee Member), David Reynolds (Committee Member)

Degree Name

Master of Science in Engineering (MSEgr)

Abstract

Locking compression plates are proven to be safe for use in open reduction and internal fixation (ORIF). The ORIF is a procedure performed to treat fractures. It has various combination of holes, the system provides more options for clinicians to use either locking screw or non-locking screws. This thesis investigates and determines the best construct with special locking and non-locking screws under both axial and torsion loading. Twenty femur constructs were assembled with 2 cm osteotomy gap between femur shaft and condyle, bridged with 4.5 mm - 10 holes condyle plates. Femurs were divided in to 4 groups according to screw types and where they were placed. All screws were tightened to 4 Nm torque with a torque meter. Axial loads of -50 N to -700N and ±5 degree rotation were applied for 50,000 cycles. Loosening torques of screws, stiffness and displacement of constructs were measured. Finite element analysis (FEA) was performed on locking plate and screws based on computed tomography images and Solidworks models. Analytical simulations were run under static and limited dynamic conditions were investigated with the experimental results. Axial load was applied and stresses induced were measured on the simulated models. Locking screw increased the torsional resistance of adjacent non-locking screw. Deformation and torsional stiffness in constructs with two locking screws were higher compared to one locking screw after 50,000 cycles. Locking screws increased flexibility of the constructs allowing reduction in osteotomy gap. FEA results show plate with locking screws induced lower von Mises stress compared to plate with non locking screws. This study concluded that among hybrid locked plated constructs, constructs with two locking screws provided more stability, flexibility and durability under various loading. A locking screw near the fracture gap increases axial and torsional strength of locking plated system and increased torsional strength of all the other screws.

Page Count

67

Department or Program

Department of Biomedical, Industrial & Human Factors Engineering

Year Degree Awarded

2008

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