1. General introduction 25 1. OBJECTIVES AND OUTLINE OF THIS THESIS The aim of this thesis was to investigate the efficacy, safety and patient satisfaction of an innovative needle-free drug delivery device (Enerjet) to treat patients with keloidal scars. In order to study this, various research techniques and designs were used. First, the available evidence for needle-free jet injectors in dermatology was studied according to a systematic review approach. Hereafter, an ex vivo study was performed to visualize the distribution patterns of EPI-assisted jet injections in keloids. A randomized controlled trial was performed to study the efficacy and safety of EPI-assisted bleomycin in patient with recalcitrant keloids. Subsequently, two retrospective real-world studies using EPI-assisted drug delivery were performed. The first study aimed to explore the effectiveness, tolerability and patient satisfaction of EPI-assisted bleomycin and lidocaine in adult patients with recalcitrant keloids. The second study was performed to explore the effectiveness, tolerability and patient satisfaction of EPI-assisted triamcinolone in children with keloids or hypertrophic scars. Chapter 2 The second chapter of this thesis describes the current evidence regarding the efficacy and safety of needle-free jet injectors to treat various dermatological indications. The available evidence for needle-free jet injectors in dermatology is summarized and critically appraised in a systematic review with risk of bias assessment. Chapter 3 The third chapter describes the distribution of EPI-assisted jet injections in severe keloids by performing pre-clinical experiments. In this chapter we performed an ex-vivo study, in which EPI-assisted jet injections and conventional needle injections in normal skin samples and recalcitrant keloid samples were visualized using the 3D-FICS, an innovative 3D-imaging technique. Chapter 4 The fourth chapter describes the clinical factors that may negatively influence the treatment response in keloids according to previous literature. In this chapter we
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