Event Abstract Back to Event Making the most of additive layer manufacture - development of tailored titanium implants with embedded therapeutics Sophie Cox1, Hany Hassanin2*, Parastoo Jamshidi2*, Moataz Attallah2*, Duncan Shepherd3*, Owen Addison4* and Liam Grover1* 1 University of Birmingham, Chemical Engineering, United Kingdom 2 University of Birmingham, Materials and Metallurgy, United Kingdom 3 University of Birmingham, Mechanical Engineering, United Kingdom 4 University of Birmingham, Dentistry, United Kingdom Introduction: Musculoskeletal disorders cost society an estimated $254 billion annually[1]. Common metallic alloys used for bone prostheses, including titanium, exhibit modulus values significantly higher than native bone tissue. This mismatch results in a phenomena called stress shielding, which ultimately may impact implant functionality and patient quality of life. Furthermore, despite low incidence rates, infection of primary and revision prostheses represents one of the most serious and devastating complications[2]. Since invention in the 1980s, additive layer manufacture (ALM) techniques have been employed in a number of industries. The utilisation of such methods has provided researchers with improved geometrical design flexibility since the part is manufactured from a model constructed using computer aided design (CAD) software, which circumvents a number of limitations associated with traditional techniques, such as casting. Primarily, ALM techniques have been employed in medicine to manufacture tailored implants created from patient geometries obtained from CT or MRI data. We propose that these manufacturing modalities may be further exploited to address stress shielding and infection issues related to bone prostheses. In this case study we demonstrate the design and manufacture of novel implant models using selective laser melting (SLM), that incorporate a mechanically optimised reservoir containing a secondary biomaterial phase loaded with a therapeutic reagent. Materials and Methods: A dental screw model was altered using CAD (Solidworks) to incorporate a central reservoir connected to the extremities via four pore channels on the bottom face of the part (Figure 1). Implants were manufactured from a Ti-6Al-4V alloy using a Concept M2 Cusing System. Structures were then loaded with injectable calcium phosphate cements containing gentamicin sulphate as a model antibiotic. Results: Micro-CT revealed successful infiltration of the reservoir with optimised cement formulations. The majority, >80%, of cement porosity was found to be open and this is suggested to have contributed to release of gentamicin sulphate, which was monitored by UV absorbance. Within 72 hours the antibiotic payload had been released from the implant and was shown, using an agar diffusion assay, to inhibit the growth of staphylococcus aureus and epidermis bacteria. Conclusions: Restoring the structure and function of musculoskeletal disorders, particularly in areas of significant load bearing, continues to challenge researchers and clinicians. Promisingly, this case study demonstrates that by fully utilising the geometrical design flexibility of ALM further mechanical and therapeutic functionality may be incorporated into bone prostheses. The results of this study show that this innovative approach has the potential to address stress shielding and infection issues associated with implants, which currently devastatingly impact patient quality of life. EPSRC for financially supporting this research (EP/L020815/1)
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