Chimutengwende-Gordon, NF; (2015) Enhancing the Soft Tissue-Implant Seal and Reducing Bacterial Colonisation around the Intraosseous Transcutaneous Amputation Prosthesis. Doctoral thesis , UCL (University College London).

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Abstract

The Intraosseous Transcutaneous Amputation Prosthesis (ITAP) may improve quality of life for amputees by avoiding soft tissue complications associated with socket prostheses and by improving sensory feedback and function. ITAP relies on a soft tissue seal forming at the skin-implant interface in order to prevent epithelial downgrowth and infection. A successful soft tissue seal is dependent on soft tissue cells winning the ‘race for the surface’ against bacteria. The current ITAP design includes a flange with drilled holes to promote soft tissue attachment. Despite this, infection remains a significant risk. This thesis aimed to investigate the effect of a fully porous titanium alloy (PT) flange with interconnected pores and fibronectin (Fn)-functionalised hydroxyapatite (HA) coatings on soft tissue integration. Silver (Ag) was incorporated into coatings for its antimicrobial properties. In vitro fibroblast viability and bacterial colonisation on HAAgFn coatings was studied. HAAgFn was applied to PT flanges of transcutaneous pins implanted into sheep tibiae. A histological assessment of soft tissue integration was undertaken and bacterial colonisation within the soft tissues and on the flange was quantified. The key original contributions to knowledge from this thesis are that firstly, HAAgFn coatings have antibacterial activity and are cytocompatible after serum- preconditioning in vitro. Secondly, in vivo, PT significantly reduces epithelial downgrowth, increases soft tissue integration and reduces bacterial colonisation compared with the current ITAP drilled-hole flange. Overall, the addition of coatings did not enhance these effects in vivo. HA reduced the favourable effects of PT. Fn and Ag counteracted some of the negative effects of HA suggesting that using these coatings without HA could improve results. In conclusion, a PT flange has the potential to reduce the susceptibility of ITAP to infection compared with the current ITAP design. It is hoped that this finding will be translated into clinical practice.

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