Novel Porous Titanium Structures for Primary and Secondary Fixation in Orthopaedic Applications

Successful orthopaedic implants require both immediate mechanical stability and long-term biological integration to ensure durable fixation and functional recovery. This thesis investigates the role of three-dimensional (3D) porous titanium architecture in enhancing osseointegration through a multidisciplinary approach that integrates cell biology, mechanical design, and long-term tissue interaction. The first study employed RNA sequencing to evaluate the gene expression profiles of osteoblast-like MG-63 cells cultured on flat versus 3D porous titanium, with and without exposure to the pro-inflammatory cytokine interleukin-1. The findings demonstrated that 3D surfaces promoted osteogenic signalling and extracellular matrix (ECM) remodelling while attenuating inflammatory responses compared to flat surfaces, supporting their potential to enhance bone healing even in inflammatory environments. Building on these biological insights, the second study focused on mechanical optimization of 3D porous titanium pins through the design of novel surface strut geometries. Custom-designed angled and spike-like surface features were evaluated for their impact on insertion force, expulsion force, and rotational stability. Certain geometries particularly those with angled lower struts were found to improve fixation strength while reducing insertion resistance, highlighting the potential of surface feature engineering to improve primary mechanical stability. The final study addressed long-term implant performance by introducing interconnected porous channels (IPC) into the titanium structures to mitigate ECM occlusion and maintain internal fluid flow. Over a 28-day in vitro culture period with bone cells, IPC regions demonstrated sustained permeability and reduced occlusion compared to standard porous regions. Scanning electron microscopy and fluid flow analysis confirmed that IPC-enhanced structures support prolonged internal perfusion, which is critical for vascularisation and long-term osseointegration. Collectively, this body of work presents a comprehensive strategy for advancing orthopaedic implant design by integrating biological responsiveness, mechanical fixation, and long-term tissue compatibility. The findings support the development of next-generation titanium implants with optimized surface and internal architecture to improve clinical outcomes in bone repair and regeneration.